| the effects of the tick amblyomma hebraeum (acari: ixodidae) on blood composition and weight of rabbits. | | 1980 | 7218269 |
| some effects of 60co irradiation on cowdria ruminantium in its tick host amblyomma hebraeum koch (acarina: ixodidae). | an attempt was made to attenuate cowdria ruminantium by irradiation of the nymphal stage of its tick host, amblyomma hebraeum. the irradiated nymphs were homogenized and serial dilutions of the resultant suspension were injected intravenously into heartwater-susceptible sheep. no attenuation could be demonstrated but the results indicate that progressively more micro-organisms will be destroyed the higher the irradiation dosage applied, and that dosages between 20 and 30 kilorad apparently prove ... | 1981 | 7279384 |
| an investigation into the toxic principle in eggs of the tick amblyomma hebraeum. | a purification procedure involving iso-electric focusing by means of which a toxic principle may be obtained in a pure form from crude egg extracts of amblyomma hebraeum is described. the molecular mass of the toxin is approximately 10 000 according to sedimentation equilibrium sedimentation, sodium dodecyl sulphate (sds) gradient gel electrophoresis and calculations from the amino acid composition. non-competitive proteinase inhibitory activity was found to be associated with the toxin. histopa ... | 1981 | 7312303 |
| regulation of body volume by salivation in a tick challenged with fluid loads. | injection into the hemolymph of 1.2% nacl, 11.2% sucrose, 2.3% urea (all approximately isosmotic to hemolymph), or distilled water induced salivary fluid secretion in the ixodid tick amblyomma hebraeum koch. saline gave the largest response at high doses. injection of hyperosmotic nacl into the hemolymph did not induce salivation but led to the drinking of distilled water in amounts sufficient to dilute the salt load to isosmolarity. atropine only partially inhibited salivation induced by nacl, ... | 1980 | 7356041 |
| the ultrastructure of somatic neuromuscular junctions in the tick amblyomma variegatum (fabr.). | peripheral nerve axons synapse with somatic muscle fibres in the tropical bont tick amblyomma variegatum. each fibre is innervated by numerous terminals; some of the axons synapse more than once. the nerve terminals on coxal muscle fibres contain agranular electron lucent vesicles 50 to 58 nm in size and have the specialised synaptic membranes characteristic of chemically transmitting nerve-muscle junctions. some of the terminals on trochanteral muscle fibres additionally contain larger vesicles ... | 1980 | 7388905 |
| regional specialization of the sperm membrane in the tick amblyomma hebraeum koch (acari: ixodidae). | the spermatozoon of amblyomma hebraeum is about 200 micrometers long and comprises: (l)a thick, club-shaped anterior part, about 20 micrometers long bearing at its apex a "tactile" hemisphere, and (2) an elongated tail-like part, about 180 micrometers long. the surface of the "tactile" hemisphere is covered by numerous bulbous expansions, attached to it by short stalks. the base of the hemisphere is surrounded by a fringe of thin motile processes; the remaining surface of the spermatozoon is cov ... | 1980 | 7388929 |
| a critical evaluation of the role played by the red-billed oxpecker buphagus erythrorhynchus in the biological control of ticks. | buphagus erythrorhynchus uses 4 feeding methods--scissoring, plucking, pecking and insect catching. during the day the birds spend 68% of their time feeding, with peaks of activity during the early morning and late afternoon. a total of 21 641 ixodid ticks were found in 53 stomachs examined, with a range of between 16 and 1 665 per stomach. boophilus and rhipicephalus were the most important genera eaten. thirty diptera, also found in the stomachs, accounted for 0,4% of the diet by mass. the foo ... | 1980 | 7413164 |
| cattle ticks from the waterberg district of the transvaal. | macroscopically visible ticks were collected from the hides of 28 cattle slaughtered in pairs during a period of 14 months in the waterberg district. in order of prevalence rhipicephalus appendiculatus, rhipicephalus evertsi evertsi, amblyomma hebraeum, hyalomma marginatum rufipes, ixodes cavipalpus, hyalomma truncatum and boophilus decoloratus were recovered. immature stages of the three commonest species constituted a major portion of the population for varying periods during the months april ... | 1980 | 7452655 |
| bacteriocidal qualities of ixodid tick (acarina: ixodidae) salivary cement plugs and their changes under the influence of a viral tick-borne pathogen. | the abundance of bacteriocidal compounds contained in the salivary cement plug of ixodid ticks was changed because of the reproduction of tick-borne encephalitis virus (tbev) in their bodies. the size of tbev-infected ixodes persulcatus shulze lytic zone surrounding the cement plug enlarged to that of naive ticks, whereas micrococcus lysodeikticus (cohn) lytic zones induced by the cement plugs of tbev-infected amblyomma hebraeum koch nymphs or rhipicephalus appendiculatus neumann females were re ... | 1995 | 7473610 |
| the detection of antibodies cross-reacting with cowdria ruminantium in the sera of domestic ruminants in regions of south africa where amblyomma hebraeum does not occur. | high levels of seropositivity, in all probability attributable to ehrlichia, were recorded in the serum of domestic ruminants throughout districts in south africa where amblyomma hebraeum, the vector of the heartwater agent, does not occur. the antibodies, detected with the indirect fluorescent antibody (ifa) and the indirect elisa tests, cross-reacted with cowdria ruminantium, which was used as antigen in both tests. a combination of the ifa and elisa tests, currently employed to detect antibod ... | 1994 | 7501358 |
| effects of tick infestation and tick-borne disease infections (heartwater, anaplasmosis and babesiosis) on the lactation and weight gain of mashona cattle in south-eastern zimbabwe. | the effects of ticks and tick-borne disease infections on the lactation and weight gain of mashona cattle were studied at mbizi quarantine station in the south-eastern lowveld of zimbabwe. twenty-nine mashona cows were allocated to 2 balanced groups and kept in separate paddocks at a stocking rate of one animal per 8 ha. one group received regular acaricide treatment to control bont (amblyomma hebraeum) and other ticks. the other group was left untreated. the cows were artificially inseminated. ... | 1995 | 7502343 |
| laboratory reared amblyomma hebraeum and amblyomma variegatum ticks differ in their susceptibility to infection with cowdria ruminantium. | the susceptibility of laboratory reared zimbabwean amblyomma hebraeum and a. variegatum ticks to infection with geographically distinct cowdria ruminantium strains was investigated by feeding both species simultaneously on individual sheep infected with one of the four strains (crystal springs [zimbabwe], ball 3 [south africa], gardel [guadeloupe] and nigeria [nigeria]). a. hebraeum ticks demonstrated a high susceptibility to infection with all four c. ruminantium strains. in comparison, a. vari ... | 1995 | 7589273 |
| evaluating the economic damage threshold for bont tick (amblyomma hebraeum) control in zimbabwe. | controlling ticks and tick-borne diseases by frequent applications of acaricides (e.g., dipping) is costly, and can leave treated livestock vulnerable to epizootics of tick-borne diseases should the system of applying acaricides break down. the concept of only applying acaricides on an infrequent (strategic) basis often relies on the target tick population displaying a seasonal cycle. however, as adult bont tick (amblyomma hebraeum) infestations in zimbabwe's lowveld do not have a strictly seaso ... | 1993 | 7628230 |
| pheromonal composition of two species of african amblyomma ticks: similarities, differences and possible species specific components. | two species of bont ticks, amblyomma hebraeum and amblyomma variegatum, common to africa were studied to compare types and quantities of compounds known or believed to serve as components of the attraction-aggregation-attachment pheromone (aaap). a complex of attraction, aggregation and attachment stimulating pheromone components are used by these ticks to detect hosts, mates and, perhaps, minimize interspecific breeding. solvent extraction of pheromone emitting ticks followed by gas chromatogra ... | 1994 | 7628240 |
| factors affecting the distributions of the ticks amblyomma hebraeum and a. variegatum in zimbabwe: implications of reduced acaricide usage. | the ticks amblyomma hebraeum and a. variegatum are the main vectors of heartwater, a disease of ruminants caused by cowdria ruminantium, in the agricultural areas of zimbabwe. at present, a. hebraeum is widely distributed in the dry southern lowveld, and occurs in at least seven foci in the higher rainfall highveld. amblyomma variegatum occurs in the zambezi valley and surrounding dry lowveld areas in the northwest. the distribution of a. hebraeum has changed considerably over the past 70 years, ... | 1994 | 7628253 |
| the effect of rainfall on tick challenge at kyle recreational park, zimbabwe. | the effect of rainfall pattern on tick challenge was investigated at kyle recreational park, zimbabwe, from 1991 to 1992 using drag and removal plot methods to sample environmental tick density. the abundance of adults and nymphs of the brown ear-tick rhipicephalus appendiculatus and larvae of the bont tick amblyomma hebraeum was positively correlated with monthly rainfall, whereas no relationship with rainfall was revealed for larval r. appendiculatus, adults of the red-legged tick r. evertsi, ... | 1994 | 7628257 |
| an investigation into the health status and diseases of wild dogs (lycaon pictus) in the kruger national park. | many factors have been cited as possible reasons for the decline in the number of wild dogs (lycaon pictus), but few studies have provided supportive data. between 1990 and 1993, the dynamics of 10 wild dog packs in the southern district of the kruger national park in south africa were monitored. casual observations of the causes of disease and mortality in the entire population were also recorded. during the same period, 46 wild dogs were immobilised, weighed, and subjected to physical examinat ... | 1995 | 7629782 |
| development and evaluation of pcr assay for detection of low levels of cowdria ruminantium infection in amblyomma ticks not detected by dna probe. | the sensitivities of a pcr assay and a dna probe assay were compared for the detection of cowdria ruminantium in amblyomma ticks that were fed on c. ruminantium-infected, clinically reacting, and recovered carrier animals. the pcr assay and dna probe detected infection in 86.0 and 37.0%, respectively, of 100 ticks fed on a febrile animal. in 75 ticks fed on carrier animals, pcr and the dna probe detected infection in 28.0 and 1.33% of ticks, respectively. this demonstrates that the dna probe has ... | 1995 | 7699036 |
| [changes in the bactericidal activity of the cementing fraction in ixodid tick saliva under the influence of the presence of the tick-borne encephalitis virus]. | it is demonstrated that the abundance of bactericidal compounds in the salivary cement plug of ixodid ticks is changing under the influence of virulent tick-borne encephalitis virus (tbev) reproduction in their bodies. tbev infected ixodes persulcatus cement plug-forming lytic zone size enlarged in comparison with the naive tick one whereas micrococcus lysodeikticus lytic zones induced by the cement plug of tbev infected amblyomma hebraeum nymphs or rhipicephalus appendiculatus females reduced c ... | 1994 | 7715548 |
| ecdysteroid titre and metabolism and cuticle deposition during embryogenesis of the ixodid tick amblyomma hebraeum (koch). | three embryonic cuticles are formed before larval cuticle deposition during embryonic development of amblyomma hebraeum. the quantity of radioimmunoassay-positive material varied between 50 and 200 pg ecdysone equivalents per mg, but no significant peaks were detected. maternally incorporated [3h]-20-hydroxyecdysone and [3h]-ecdysone contained in freshly laid eggs appear to be conjugated to c-22 fatty acid esters and 3 alpha epimers of those esters, and, thus, appear doubly inactivated. in addit ... | 1995 | 7858939 |
| helminth and arthropod parasites of indigenous goats in the northern transvaal. | helminth and arthropod parasites of 60 female indigenous goats of three age groups on a farm in the northern transvaal were collected, identified and counted. anoplocephalid tapeworms were present in the two younger groups of goats, while larvae of taenia hydatigena were recovered from all three groups. eight species and two genera of nematodes were found in the youngest goats, five species and three genera in the middle group and six species and two genera in the oldest goats. strongyloides pap ... | 1994 | 7898893 |
| a new pathogenic spotted fever group rickettsia from africa. | a spotted fever group (sfg) rickettsia was isolated in zimbabwe from a patient with tick-bite, fever, headache and regional lymphadenopathy. a further six isolates were obtained from amblyomma hebraeum ticks collected in zimbabwe. these human and tick isolates were indistinguishable from each other, and from an ethiopian sfg rickettsia, by microimmunofluorescence (mif), sodium dodecyl sulphate-polyacrylamide gel electrophoresis (sds-page), western blotting and polymerase chain reaction followed ... | 1994 | 7911846 |
| isotopes as host blood markers to measure blood intake by feeding ticks (acari: ixodidae). | we have modified an experimental technique in which two different isotopes (cr51 and i125) were used simultaneously as blood markers for determining the amount of blood removed by feeding ticks. this method enables us to measure separately and directly the volumes of red blood cells and plasma in ticks and to calculate the ratio between the two parameters (concentrating ability). the concentration of red blood cells in nymphs of amblyomma hebraeum kock and rhipicephalus appendiculatus neumann an ... | 1994 | 7932595 |
| parasites of domestic and wild animals in south africa. xxxii. ixodid ticks on scrub hares in the transvaal. | a total of 264 scrub hares (lepus saxatilis) were examined for ixodid ticks at various localities in the kruger national park, eastern transvaal lowveld. thirteen tick species were recovered from these hares. the seasonal abundances of the immature stages of amblyomma hebraeum, amblyomma marmoreum, hyalomma truncatum, rhipicephalus appendiculatus, rhipicephalus evertsi evertsi, rhipicephalus simus and rhipicephalus zambeziensis and all stages of a rhipicephalus sp. (near r. pravus) were determin ... | 1993 | 7970571 |
| the relationship between cowdria and ehrlichia: change in the behaviour of ehrlichial agents passaged through amblyomma hebraeum. | following an earlier report that an ehrlichia-like agent isolated from an adult hyalomma truncatum female became more pathogenic and elicited a disease in sheep indistinguishable from heartwater after having been passaged through amblyomma hebraeum, a similar phenomenon is herewith recorded. an ehrlichial agent demonstrated in the blood smear of a serologically positive, naturally infected lamb, changed in behaviour and assumed the characteristics of cowdria after passage through a. hebraeum. cr ... | 1993 | 8134623 |
| ventilation in the adults of amblyomma hebraeum and a. marmoreum (acarina, ixodidae), vectors of heartwater in southern africa. | the objective of this study was to establish the major features of respiratory gas exchange in unfed adults of the ticks amblyomma hebraeum and a. marmoreum, both vectors of heartwater in southern africa. carbon dioxide emission of ticks was measured at 25 degrees c using flow-through respirometry in order to determine standard metabolic rate (smr) and the temporal pattern of gaseous emission. for both species, smr was extremely low and approximately 100 fold less than that predicted for an inse ... | 1993 | 8134650 |
| the impact of pure infestations of rhipicephalus appendiculatus and amblyomma hebraeum on the productivity of cattle and implications for tick control strategies in africa. | this paper reviews studies carried out by an fao project in zimbabwe, on the effects of the ticks rhipicephalus appendiculatus and amblyomma hebraeum on the productivity of cattle. larvae and nymphs of the two species had no detectable effect on liveweight gain (lwg). the losses in lwg caused by each adult female that completed feeding were approximately 4 g for r. appendiculatus and 10 g for a. hebraeum. losses in milk production caused by both species amounted to approximately 7 g for every fe ... | 1990 | 2126617 |
| drag-sampling of free-living ixodid ticks in the kruger national park. | free-living ticks were collected by means of drag-sampling in 32 of the 35 landscape zones of the kruger national park during a period of 1 calendar month. of the 18,199 specimens collected, 99.53% were larvae, 0.05% nymphs and 0.42% adults. fourteen species were collected. amblyomma hebraeum followed by boophilus decoloratus, predominated, both in distribution and abundance. large variations were encountered between drags. there was no correlation between the numbers of larvae collected and tim ... | 1991 | 2052317 |
| isolation of spotted fever group rickettsias from triturated ticks using a modification of the centrifugation-shell vial technique. | a modification of the centrifugation-shell vial technique was used to isolate spotted fever group (sfg) rickettsias from triturated ticks which had previously been stored at -80 degrees c for up to 7 months. sfg rickettsias were successfully isolated in vero cells from all 7 haemolymph positive ticks (amblyomma hebraeum) used in the experiment. attempts were also made to use these tick triturates to establish sfg rickettsial infections in tissue culture. vero cells were used for 5 of the tick tr ... | 1991 | 1949146 |
| transmission of a spotted fever group rickettsia by amblyomma hebraeum (acari: ixodidae). | amblyomma hebraeum, a cattle tick common in southern africa, was demonstrated to be capable of maintaining an infection with an unclassified spotted fever group rickettsia both transtadially and transovarially. all feeding stages of the tick transmitted the infection to rabbits. the rickettsia was isolated and found to be serotypically distinct from three strains of rickettsia conorii by microimmunofluorescence. rabbit serum titers were found to be higher with indirect fluorescent antibody (ifa) ... | 1991 | 1941925 |
| pheromone/acaricide mixtures in the control of the tick amblyomma hebraeum: effects of acaricides on attraction and attachment. | unfed adults and nymphs of the bont tick amblyomma hebraeum koch are attracted to hosts on which fed males, emitting an aggregation-attachment pheromone (aap), are attached. pheromone/acaricide mixtures have the potential to selectively attract and kill these ticks. we have investigated the effects of three acaricides, amitraz (an amidine), flumethrin (a synthetic pyrethroid) and chlorfenvinphos (an organophosphate), combined with aap, on the attraction and attachment of the unfed adults. attrac ... | 1991 | 1893800 |
| specificity and effects of host resistance on the african tick rhipicephalus zambeziensis (acarina: ixodidae). | repeated infestations of the rabbit with adult rhipicephalus zambeziensis ticks resulted in a ten-fold reduction in engorgement weight of adult ticks and a significant decline in engorgement weight of nymphs. there was no evidence of cross-resistance against the south african bont tick, amblyomma hebraeum. immunization of rabbits with crude extracts of whole-tick protein significantly influenced engorgement weights and oviposition rates of adult r. zambeziensis. histological studies of tissues f ... | 1991 | 1893799 |
| resistance of restrained bos taurus dairy bull calves to the bont tick amblyomma hebraeum (acarina: ixodidae). | three infestations of restrained jersey and friesland bull calves with adult amblyomma hebraeum did not affect the rate of engorgement of female ticks and resulted in an insignificant decline in the mean engorgement weight of female ticks recovered from the friesland group. repeated infestations significantly affected the egg-laying capacity of engorged female ticks recovered from both groups of hosts. the friesland calves manifested an enhanced resistance to the larvae and nymphs of amblyomma h ... | 1991 | 1882498 |
| seasonal occurrence of the bont tick (amblyomma hebraeum) in the southern lowveld of zimbabwe. | the seasonal occurrence of the bont tick amblyomma hebraeum was recorded over 2 years on 20 brahman cattle held in a 240-ha paddock at mbizi in southeastern zimbabwe. the cattle were infested with all life cycle stages throughout the study period, and no clearly defined seasonal patterns were recorded. males remained attached for up to about 6 months, and consequently accumulated on the cattle and outnumbered females considerably. the cattle did not acquire resistance to a. hebraeum and the abun ... | 1991 | 1786747 |
| comparison of known and suspected pheromonal constituents in males of african ticks, amblyomma hebraeum koch and amblyomma variegatum (fabricius). | three low molecular weight compounds were found in hexane:diethyl ether extracts of fed males of the african ticks, amblyomma variegatum (tropical bont tick) and a. hebraeum (bont tick), namely, o-nitrophenol, methyl salicylate and 2,6-dichlorophenol. these same compounds were also fond in a rinse of fed a. variegatum males, but were absent or present in only trace amounts in a rinse of fed a. hebraeum males, o-nitrophenol and methyl salicylate were present in much higher concentrations (i.e., a ... | 1991 | 1786745 |
| immunization of rabbits against nymphs of amblyomma hebraeum and a. marmoreum (acari: ixodidae). | himalayan rabbits immunized with homogenates prepared from nymphs of amblyomma hebraeum koch and a. marmoreum koch ticks developed humoral and probably also cell-mediated immunity to their respective homogenates. beta and gamma globulin levels and numbers of eosinophils and neutrophils increased significantly in inoculated rabbits. the recipient animals developed resistance to homospecific nymphal infestations. cross resistance between the two species was not evaluated. nymphs of both species th ... | 1992 | 1404253 |
| perception of breath components by the tropical bont tick, amblyomma variegatum fabricius (ixodidae). i. co2-excited and co2-inhibited receptors. | wall-pore olfactory sensilla located in the capsule of haller's organ on the tarsus of amblyomma variegatum ticks bear cells responding to vertebrate breath: one of these sensilla contains a co2-excited receptor and a second sensillum has a co2-inhibited receptor. each of these antagonistic co2-receptors, which display typical phasic-tonic responses, monitors a different co2-concentration range. the co2-inhibited receptor is very sensitive to small concentration changes between 0 and ca. 0.2%, b ... | 1992 | 1331433 |
| responses of the ticks amblyomma hebraeum and a. variegatum to known or potential components of the aggregation-attachment pheromone. iv. attachment stimulation of nymphs. | ten known or potential components of the aggregation-attachment pheromone (aap) of the ticks amblyomma hebraeum and a. variegatum, as well as a mixture of these components and extracts of prefed males of the two species, were tested as attachment stimulants for nymphs. unfed nymphs were confined in linen bags on the ears of rabbits that had been treated with the test compounds, mixture or extracts; the numbers attached were recorded after 24 h. in a. hebraeum, attachment was induced by four comp ... | 1992 | 1286610 |
| responses of the ticks amblyomma hebraeum and a. variegatum to known or potential components of the aggregation-attachment pheromone. iii. aggregation. | ten known or potential components of the aggregation-attachment pheromone (aap) of the ticks amblyomma hebraeum and a. variegatum, as well as mixtures of these components, extracts of prefed males and live prefed males, were tested as aggregation stimulants. in field assays, laboratory-reared unfed male and female ticks were released 20 cm downwind of co2/pheromone release sites; the numbers of ticks that aggregated at the release sites were recorded after 30 min. in a. variegatum, aggregation w ... | 1992 | 1286609 |
| efficacy of ivermectin against ectoparasites of cattle in south africa. | the efficacy of various formulations of ivermectin administered at the recommended dose rate of 200 micrograms/kg was evaluated in cattle infested with mange mites (sarcoptes scabiei var. bovis.), lice (linognathus vituli and damalinia bovis) and ticks (boophilus decoloratus, amblyomma hebraeum, rhipicephalus appendiculatus and hyalomma spp.) in 8 trials conducted in south africa. mange mites (s. scabiei) were eliminated from animals treated subcutaneously, resulting in marked clinical recovery. ... | 1985 | 3839021 |
| metabolism of [3h]ecdysone by isolated tissues of the female ixodid tick amblyomma hebraeum (ixodoidea; ixodidae). | malpighian tubules, gut, ovaries and carcasses of the adult female tick amblyomma hebraeum were incubated in vitro in the presence of 2 microm [3h]ecdysone. organs and media were separately extracted after 6, 24 and 48 h incubations and the patterns of ecdysone metabolites were analyzed by hplc. esterase-susceptible apolar metabolites similar to the ap2 already described in the soft tick ornithodoros moubata and thus presumably corresponding to the same conjugates (c-22 esters with fatty acids) ... | 1986 | 3758475 |
| parasites of domestic and wild animals in south africa. xviii. the crowned guinea fowl (numida meleagris), an important host of immature ixodid ticks. | the tick burdens of 10 crowned guinea fowl (numida meleagris), shot at approximately 3-monthly intervals in the mountain zebra national park, and of 21 crowned guinea fowl from the andries vosloo kudu reserve, the majority of which were shot at monthly intervals, were determined. no adult ticks were recovered from any of the guinea fowl. the birds in the mountain zebra national park harboured 4 species of ixodid ticks of which amblyomma marmoreum was the most abundant and most prevalent. three b ... | 1986 | 3725331 |
| metabolism of ecdysteroids in the female tick amblyomma hebraeum (ixodoidea, ixodidae): accumulation of free ecdysone and 20-hydroxyecdysone in the eggs. | [3h]-20-hydroxyecdysone ([3h]-20e) injected into amblyomma hebraeum females 7 days before the beginning of oviposition, viz. at the beginning of vitellogenesis, was converted to 3 polar peaks of unknown nature called 1, 2 and 3, and to apolar conjugates ap1, ap2 and ap3. ap2 have the same retention times as the esters of 20e with long chain fatty acids described in ornithodoros moubata (diehl et al. 1985). however, principally unmetabolized 20e was incorporated into the ovaries, and 16% of the i ... | 1987 | 3693624 |
| morphology and development of cowdria ruminantium in amblyomma ticks. | the morphology and development of cowdria ruminantium have been studied in amblyomma hebraeum and a. variegatum. colonies of c. ruminantium have so far been demonstrated microscopically in gut, salivary gland cells, haemocytes and malphighian tubules of infected amblyomma ticks. colonies in gut cells were seen in both unfed and feeding ticks but colonies in salivary gland acini were observed only in nymphs that had fed for 4 days. although the predominant type seen in both tick stages was the re ... | 1987 | 3448559 |
| kinetic properties of toxic protease inhibitors isolated from tick eggs. | 1. egg-toxins from rhipicephalus evertsi evertsi, boophilus microplus, boophilus decoloratus and hyalomma truncatum were found to be inhibitors of trypsin and in two cases also of chymotrypsin. 2. fast tight-binding and slow-binding inhibition were observed. 3. immunological identity of the toxins were assessed with ouchterlony immunodiffusion and elisa. 4. the protease content of b. decoloratus and amblyomma hebraeum tick eggs were determined by a linked enzyme assay. 5. the predictive value of ... | 1988 | 3391338 |
| the use of domestic chickens as laboratory hosts of the larvae of the bont tick, amblyomma hebraeum. | a comparison of attachment, engorgement and moulting success of amblyomma hebraeum larvae fed on domestic chickens and himalayan giant white rabbits indicates that chickens are better hosts than the rabbits. moreover the time needed for detachment of all engorged larvae is significantly less for chickens than for the rabbits. no evidence of induced immunity was found in chickens on re-infestation with larvae of a. hebraeum. | 1988 | 3353104 |
| the developmental success of amblyomma hebraeum and amblyomma marmoreum on the leopard tortoise, geochelone pardalis. | the success of natural infestations of various life history stages of amblyomma hebraeum and amblyomma marmoreum on the leopard tortoise, geochelone pardalis, was compared. success was measured by the time taken for ticks to detach, as well as the percentage of ticks engorging and subsequently either moulting to the next life history stage or laying viable eggs. larvae of a. hebraeum were the only developmental stage not recovered. nymphae and female a. hebraeum were less successful in moulting ... | 1988 | 3353093 |
| the presence of cowdria ruminantium antigen in various tissues of amblyomma hebraeum imagines as detected by an enzyme-linked immunosorbent assay. | investigation into the presence of c. ruminantium antigen, using an enzyme-linked immunosorbent assay (elisa) in various tick tissues and haemolymph of adult amblyomma hebraeum ticks revealed that the organism invades a number of body parts and can be demonstrated in a. hebraeum. in females, the gut, salivary glands, hypodermis and synganglion and in males, the salivary glands and gut showed the highest concentration. | 1988 | 3217097 |
| evidence for multiple receptors mediating fluid secretion in salivary glands of ticks. | using isolated salivary glands of the ixodid tick amblyomma hebraeum koch, we tested the effectiveness of butaclamol and sulpiride in blocking fluid secretion stimulated by a number of agonists. (+)-butaclamol was a potent inhibitor of dopamine, n-methyldopamine and noradrenaline (ki congruent to 30-60 nm), but was less effective on ergometrine (ki congruent to 310 nm). tranylcypromine-stimulated fluid secretion in the absence and presence of (+)-butaclamol and (+/-)-sulpiride suggested that tra ... | 1983 | 6188618 |
| records of the bont tick, amblyomma hebraeum, from the angulate tortoise, chersina angulata, and the leopard tortoise, geochelone pardalis. | a. hebraeum nymphae were found on 4 angulate tortoises and 13 leopard tortoises in the addo elephant national park, eastern cape province. adults of this species were collected for the 1st time from a leopard tortoise in the mkuze game reserve, natal. the significance of this finding, in relation to the normal host preferences of this tick, is briefly discussed. | 1984 | 6533508 |
| acaricides for eradication of the tick amblyomma variegatum in the caribbean. | the success of an eradication campaign against the tropical bont tick in the caribbean imposes the use of active acaricide compounds, if possible with residual activity, easy to apply and requiring few or no accessible water supplies and expensive application equipment. tests of in vitro susceptibility of tick strains from puerto rico and guadeloupe as well as observations of the impact of the current tick control campaigns conducted in some caribbean islands, seem to indicate that there is no p ... | 1993 | 8134652 |
| eradication of a new focus of amblyomma variegatum in puerto rico. | in may 1992 an infestation with the tropical bont tick appeared in a small dairy heifer replacement herd in camuy, puerto rico, a completely new site located near puerto rico's northwest coast. this finding occurred after some three years of no infestation in either puerto rico or the u.s. virgin islands and is not suspected of being associated with any previous infestations. the methods used to eradicate this tick include spray treatment at a two-week interval of all domestic livestock, with am ... | 1993 | 8134653 |
| progress towards a program for the eradication of amblyomma variegatum from the caribbean. | amblyomma variegatum (fabricius), the tropical bont tick, is now widely distributed in the caribbean. eighteen islands countries are now or were recently infested with the tick. to stop the spread of this tick to other non-infested islands and to the mainland areas of south, central and north america, a regional eradication program has been proposed and endorsed by the respective governments on each of the amblyomma variegatum infested islands, including the french government and caricom member ... | 1993 | 8134654 |
| [the acquisition of resistance by laboratory mice to amblyomma hebraeum (ixodidae) larvae]. | repeated feedings of larval amblyomma hebraeum ticks on laboratory mice results in strong decrease of engorged tick yield (from 65-73% after primary feeding to 11% after secondary feeding). laboratory mice differ essentially in this respect from rabbits and sheep which are unable to acquire the resistance (see norval, 1978) to larvae of this tick. | 1993 | 8152843 |
| respiratory gas exchange in the tick amblyomma hebraeum (acari: ixodidae). | respiratory gas exchange was studied in unfed adult amblyomma hebraeum koch. carbon dioxide emission was measured at 25 degrees c using flow-through respirometry to determine standard metabolic rate and the temporal pattern of gaseous emission. the standard co2 production rate (svco2) of inactive ticks was 0.0135 +/- 0.0085 ml g-1 h-1, and the standard o2 consumption rate (svo2) was 0.0158 +/- 0.0097 ml g-1 h-1. ventilation was discontinuous and was characterized by periodic bursts of co2 emissi ... | 1994 | 8158626 |
| antibodies to cowdria ruminantium in mozambican goats and cattle detected by immunofluorescence using endothelial cell culture antigen. | endothelial cell cultures, established from bovine umbilical cord arteries and subsequently infected with cowdria ruminantium, were used as antigen in the indirect fluorescent antibody test. bovine sera (374) and caprine sera (388) collected in 6 provinces of mozambique were tested. overall, 30.4% of goat sera had antibodies to cowdria, and 43% of sera collected from cattle. north of the river save, where the tick amblyomma variegatum is highly prevalent, overall percentages of positive sera wer ... | 1993 | 8236490 |
| an immunoblotting diagnostic assay for heartwater based on the immunodominant 32-kilodalton protein of cowdria ruminantium detects false positives in field sera. | heartwater, a major constraint to improved livestock production in zimbabwe, threatens to invade areas which have been previously unaffected. to monitor its spread in zimbabwe, an immunoblotting diagnostic assay based on the responses of animals to the immunodominant, conserved 32-kda protein of cowdria ruminantium was evaluated. in this assay, no false reactions were detected with sera known to be positive and negative, but sera from some cattle, sheep, and goats from heartwater-free areas of z ... | 1993 | 8253974 |
| detection of cowdria ruminantium by means of a dna probe, pcs20 in infected bont ticks, amblyomma hebraeum, the major vector of heartwater in southern africa. | a dna probe, pcs20, previously described for use in detection of cowdria ruminantium infections in amblyomma variegatum (the principal vector of heartwater) hybridized with c. ruminantium dna in organs of laboratory-infected a. hebraeum adult ticks (the major southern african vector of heartwater). the probe hybridized with c. ruminantium dna in 46/49 midguts from male ticks and 26/29 from females, thus indicating infection. corresponding salivary glands were less heavily infected, but infection ... | 1993 | 8432329 |
| differential recognition of saliva antigens from the ixodid tick amblyomma hebraeum (acari: ixodidae) by sera from infested and immunized rabbits. | we determined the protein composition and antigenic content of saliva from amblyomma hebraeum female ticks of different weight classes. the mean protein concentration of saliva of small partially fed ticks (< 100 mg) was 333 +/- 83 micrograms/ml and that of large partially fed ticks (150-420 mg) was 59 +/- 14 micrograms/ml. the reduction in concentration mostly was caused by the significantly higher fluid volume per minute secreted by large ticks. polypeptide analysis of saliva indicated the pre ... | 1993 | 8433335 |
| the relationship between tick (amblyomma hebraeum) infestation and immunity to heartwater (cowdria ruminantium infection) in calves in zimbabwe. | the occurrence of endemic stability for heartwater (cowdria ruminantium infection) is a controversial issue, because the means by which young cattle and other neonatal ruminants become infected and acquire immunity to the disease have never been adequately explained. we conducted a study in a heartwater-endemic area in southeastern zimbabwe to investigate the relationships between calf immunity to c. ruminatium, infestations of the tick vector amblyomma hebraeum and dam, colostral and calf antib ... | 1995 | 8533273 |
| some properties of the ecdysteroid receptor in the salivary gland of the ixodid tick, amblyomma hebraeum. | salivary gland degeneration in ixodid ticks is triggered by an ecdysteroid hormone. we used [3h]ponasterone a (poa) as a specific ligand to detect the ecdysteroid receptor in the salivary glands of large, partially fed female ticks (amblyomma hebraeum koch; acari: ixodidae). binding of [3h]poa was thermolabile and sensitive to pronase, but not to dnase or rnase, indicating that the ligand binds to a protein. scatchard analysis of [3h]poa binding strongly suggested the presence of an ecdysteroid ... | 1995 | 8536946 |
| the life-cycle of the bont tick amblyomma hebraeum in vitro. | the life-cycle of the hard tick amblyomma hebraeum was completed in vitro by feeding all life-stages of the tick through silicone membranes on bovine blood from an abattoir. ticks were placed in a simple feeder membranes on bovine blood from an abattoir. ticks were placed in a simple feeder consisting of a honey jar containing the blood with a glass tube insert (o.d. 42 mm) across the end of which the membrane was stretched. this feeding unit was held in a water bath (38 degrees c). larvae and n ... | 1995 | 8550288 |
| prevalence of rickettsia-like organisms and spotted fever group rickettsiae in ticks (acari: ixodidae) from zimbabwe. | the prevalence of rickettsia-like organisms in ticks from zimbabwe was determined using the hemolymph test. amblyomma hebraeum had the highest prevalence of rickettsia-like organisms. other species with rickettsia-like organisms included amblyomma sparsum, amblyomma variegatum, hyalomma marginatum rufipes, ripicephalus simus, haemaphysalis leachi, amblyomma rhinocerotis, and hyalomma truncatum. ticks with no demonstrable rickettsia-like organisms infection were boophilus decoloratus, haemaphysal ... | 1995 | 8551500 |
| propagation of the tick amblyomma variegatum in the caribbean. | the tropical bont tick, amblyomma variegatum, is an african tick species which infests livestock and wildlife. it was probably introduced in the central eastern islands of the caribbean during the 18th or 19th century, with cattle shipped from senegal. in africa and the caribbean, this tick is a vector of heartwater (a rickettsial disease of ruminants) and is associated with acute dermatophilosis (a bacterial skin disease of animals). until 1948, only guadeloupe and the neighbouring islands of m ... | 1995 | 8593414 |
| parasites of domestic and wild animals in south africa. xxxiii. ixodid ticks on scrub hares in the north-eastern regions of northern and eastern transvaal and of kwazulu-natal. | ixodid ticks were collected from scrub hares (lepus saxatilis) at three localities. nine tick species were recovered from 24 hares examined at pafuri, kruger national park, northern transvaal. the most abundant and prevalent species were hyalomma truncatum, rhipicephalus kochi and a rhipicephalus species (near r. pravus). twelve tick species were collected from 120 scrub hares examined around skukuza, kruger national park, eastern transvaal. the immature stages of hyalomma truncatum were most ab ... | 1995 | 8600436 |
| parasites of domestic and wild animals in south africa. xxxiv. arthropod parasites of nyalas in north-eastern kwazulu-natal. | seventy-three nyalas (tragelaphus angasii) in the umfolozi, mkuzi and ndumu game reserves in northeastern kwazulu-natal were examined for arthropod parasites during 1983 and 1984. in addition, six animals were examined during 1994. ten ixodid tick species, two louse species and a louse fly species were recovered. the nyalas were good hosts of all stages of development of boophilus decoloratus, rhipicephalus appendiculatus and rhipicephalus muehlensi and the immature stages of amblyomma hebraeum ... | 1995 | 8628570 |
| investigation of tick-borne viruses as pathogens of humans in south africa and evidence of dugbe virus infection in a patient with prolonged thrombocytopenia. | in the course of investigating suspected cases of viral haemorrhagic fever in south africa patients were encountered who had been bitten by ticks, but who lacked evidence of infection with crimean-congo haemorrhagic fever (cchf) virus or non-viral tick-borne agents. cattle sera were tested by enzyme-linked immunoassay to determine whether tick-borne viruses other than cchf occur in the country. the prevalence of antibody in cattle sera was 905/2116 (42.8%) for cchf virus, 70/1358 (5.2%) for dugb ... | 1996 | 8666081 |
| catabolism of dopamine and 5-hydroxytryptamine by monoamine oxidase in the ixodid tick, amblyomma hebraeum. | the purpose of this study was to assess biogenic amine catabolism in amblyomma hebraeum koch (an african cattle tick). we assayed haemolymph and saliva for a variety of biogenic amines (usually following injection of substrate into the haemolymph) in partially fed females using hplc coupled to electrochemical detection. dopamine (da) and 5-hydroxytryptamine (5-ht) were rapidly converted to dihydroxyphenylacetic acid (dopac) and 5-hydroxyindoleacetic acid (5-hiaa) respectively, indicating that mo ... | 1996 | 8673075 |
| resistance and cross-resistance in rabbits to adults of three species of african ticks (acari: ixodidae). | resistance to rhipicephalus appendiculatus, amblyomma variegatum and amblyomma hebraeum was investigated in the laboratory by infesting rabbits with adults of each of the three species followed by homospecific or heterospecific secondary infestations. significantly lower female engorged weights and egg mass weights were taken as evidence of protective immunity. following a single infestation with adults, rabbits developed homospecific protective immunity (resistance) to only r. appendiculatus an ... | 1996 | 8706589 |
| efficacy of pheromone-acaricide-impregnated tail-tag decoys for controlling the bont tick, amblyomma hebraeum (acari: ixodidae), on cattle in zimbabwe. | a large-scale field test using pheromone-acaricide-impregnated plastic tail-tag decoys demonstrated excellent efficacy of these devices for control of the bont tick, amblyomma hebraeum, on cattle in zimbabwe. the tail tags were impregnated with a mixture containing o-nitrophenol, methyl salicylate, 2,6-dichlorophenol and phenylacetaldehyde and one of three different acaricides (cyfluthrin, flumethrin or alphacypermethrin). o-nitrophenol and methyl salicylate are components of the a. hebraeum att ... | 1996 | 8746132 |
| tropical bont tick eradication campaign in the french antilles. current status. | the amblyomma variegatum eradication campaign was officially started in april 1994 in martinique and in guadeloupe, including its dependencies of marie galante, desirade and st martin. a budget of $10.5 and $5.9 million for guadeloupe and martinique, respectively, was initially (1991) calculated and considered necessary to achieve the program. however, eec, the most important donor, estimated that 75% only of this proposal was acceptable, on which it agrees to support a maximum of 50%. the balan ... | 1996 | 8784487 |
| potential impact of wildlife on the tropical bont tick eradication program in the caribbean. | wildlife are hosts for a. variegatum throughout its range in africa, and have been demonstrated to serve as hosts for larvae and nymphs on several islands in the caribbean. studies conducted in the caribbean have indicated that most larvae and nymphs and all adults of the tick feed on livestock; therefore, eradication can be approached through the treatment of livestock. however, since small numbers of animals such as the mongoose are infested with larvae and nymphs, these animals may represent ... | 1996 | 8784488 |
| efficacy of tail-tag decoys impregnated with pheromone and acaricide for control of bont ticks on cattle. | | 1996 | 8784489 |
| infestations of the bont tick amblyomma hebraeum (acari: ixodidae) on different breeds of cattle in zimbabwe. | infestations of adults and nymphs of amblyomma hebraeum were counted on brahman (br), brahman x simmental (bs), sanga (sa) and hereford (he) steers exposed to infested pastures at mbizi in southern zimbabwe in 1986-1987. herefords were always the most heavily infested, while the sanga tended to carry the fewest ticks with the brahman and brahman x simmental groups being in between. the ratios of the engorged females on the four breeds were 2.3:1.4:1.4:1.0 for he:br:bs:sa. the ratios of the stand ... | 1996 | 8952073 |
| impact on salivary gland degeneration by putative ecdysteroid antagonists and agonists in the ixodid tick amblyomma hebraeum | ecdysteroids cause salivary gland degeneration in female ixodid ticks. we tested the effects of the following compounds on salivary gland degeneration in the ixodid tick amblyomma hebraeum koch: hhcs (22s,23s-homocastasterone), ssbr (22s,23s-homobrassinolide), stgm (2alpha,3alpha(oh)2-delta22-stigmasten-6-one), rh 5849, and rh 5992. the first three are brassinosteroids (putative ecdysone antagonists) and the last two are nonsteroidal mimics of ecdysone in a variety of insects. in vitro, hhcs (up ... | 1996 | 8980038 |
| a possible explanation of the apparent breed-related resistance in cattle to bont tick (amblyomma hebraeum) infestations. | adult male amblyomma hebraeum tick infestations and the weights of 20 brahman steers and 38 mashona heifers were measured at different periods at the veterinary quarantine area at mbizi, zimbabwe. the experiment for the brahmans lasted 108 weeks and that for the mashona for 113 weeks. the brahman steers weighed a maximum average of 478.4 kg (se 7.9 kg), which was significantly different to the mashona heifers maximum average of 391.4 kg (se 5.6 kg) (p < 0.001). the brahmans had a maximum average ... | 1996 | 9017875 |
| survival of six species of african ticks in relation to saturation deficits. | the survival of unfed males and females of six species of african ticks was monitored at five different saturation deficits at constant temperature (25 degrees c). the survivorship curves for each species comprised a pre-mortality period, prior to when ticks started to die and a mortality period corresponding to a rapid increase in the mortality rate. longevity was defined as pre-mortality plus mortality. a negative correlation between the longevity of the ticks and the saturation deficits was f ... | 1996 | 9022266 |
| the possible role of two common three-host ticks, rhipicephalus appendiculatus and amblyomma hebraeum, in the transmission of bovine leukosis virus. | the possible role of rhipicephalus appendiculatus and amblyomma hebraeum in the mechanical and transstadial transmission of bovine leukosis virus (blv) was investigated. blv-free laboratory strains of r. appendiculatus and a. hebraeum nymphal ticks (n = 400) were fed on a blv-infected and a negative control bovine. at various intervals after engorgement the ticks were homogenised and injected subcutaneously into blv-negative sheep. adult r. appendiculatus and a. hebraeum, which had fed as nymphs ... | 1996 | 9120860 |
| a novel neuropeptide-endocrine interaction controlling ecdysteroid production in ixodid ticks. | ixodid (hard) ticks are blood-feeding arthropods that require a blood meal to complete each stage of development. however, the hormonal events coordinating aspects of feeding and development are only poorly understood. we have delineated a new neuropeptide-endocrine interaction in the adult tick, amblyomma hebraeum, that stimulates the synthesis of the moulting hormones, the ecdysteroids. in adult female ticks, ecdysteroid synthesis could be demonstrated in integumental tissue incubated in vitro ... | 1997 | 9149427 |
| the effects of the bont tick, amblyomma hebraeum, on milk production of sanga and sanga x brahman cattle. | the effects of adults on the bont tick, amblyomma hebraeum on the milk production of sanga and sanga x zebu (brahman) cattle were measured over a period of 11 weeks in the low veld of zimbabwe in the summer of 1986. four groups of lactating cows, consisting of two breeds, each divided into a high and low tick treatment, were exposed to very low or high challenges of ticks and their milk production measured by weighing their calves before and after suckling. the liveweight gains (lwg) of the calv ... | 1997 | 9226643 |
| identification of an ixodes ricinus salivary gland fraction through its ability to stimulate cd4 t cells present in balb/c mice lymph nodes draining the tick fixation site. | balb/c mice infested with larvae or nymphs of ixodes ricinus develop in their lymph nodes a t cell-specific immune response triggered by salivary gland soluble antigens (sga). sga are apparently conserved in the 3 biological stages of i. ricinus ticks and are species specific. sga derived from partially fed females i. ricinus stimulate lymph node t cells from mice infested with i. ricinus larvae or nymphs. in contrast, lymph node cells from mice infested with amblyomma hebraeum nymphs do not res ... | 1997 | 9226956 |
| helminths and arthropods of black and white rhinoceroses in southern africa. | helminths and arthropods were collected and quantified from two black rhinoceroses (diceros bicornis bicornis) and one white rhinoceros (ceratotherium simum), and ticks from an additional four black and two white rhinoceroses in southern africa. the helminths of a black rhinoceros from the republic of south africa and one from namibia were quantitatively measured and recorded for each compartment of the alimentary tract. probstmayria vivipara was the most abundant parasite in each animal. a rece ... | 1997 | 9249695 |
| ecdysteroid regulation of salivary gland degeneration in the ixodid tick, amblyomma hebraeum: a reconciliation of in vivo and in vitro observations. | salivary gland degeneration in the female tick amblyomma hebraeum koch is triggered by an ecdysteroid (es) hormone. under both in vivo and in vitro conditions, degeneration requires 4 days for completion. in partially fed females that have fed beyond a "critical weight," the commitment period for salivary gland degeneration occurs between 24 and 48 h after removal from the host. although tissue degeneration begins within 24 h postengorgement, es titer as measured by radioimmunoassay (ria) does n ... | 1998 | 9473365 |
| immunization of cattle by infection with cowdria ruminantium elicits t lymphocytes that recognize autologous, infected endothelial cells and monocytes. | peripheral blood mononuclear cells (pbmc) from immune cattle proliferate in the presence of autologous cowdria ruminantium-infected endothelial cells and monocytes. endothelial cells required treatment with t-cell growth factors to induce class ii major histocompatibility complex expression prior to infection and use as stimulators. proliferative responses to both infected autologous endothelial cells and monocytes were characterized by expansion of a mixture of cd4+, cd8+, and gammadelta t cell ... | 1998 | 9573061 |
| pcr detection of cowdria ruminantium infection in ticks and animals from heartwater-endemic regions of zimbabwe. | the development of a pcr assay for the detection of cowdria ruminantium infection in ticks has been previously described. here we report a further evaluation of this assay by comparison with a dna probe and with the mouse inoculation assay (mia). application of the pcr assay in determining the prevalence of infection in ruminants and ticks from heartwater-endemic areas of zimbabwe is also described. one hundred uninfected and 120 infected amblyomma hebraeum ticks were analyzed by pcr, dna probe ... | 1998 | 9668453 |
| the caricom/fao/iica caribbean amblyomma program. | the objective of the caribbean amblyomma program is to eradicate the tropical bont tick (tbt), amblyomma variegatum, from the caribbean. field activities directed to eradication of the tbt were initiated in may 1995 commencing in northern caribbean islands. plans have been finalized for the remaining islands to the south to start eradication activities in early 1997. the components of the program include tick control and surveillance, adaptive research, training, communications, and extension. d ... | 1998 | 9668484 |
| successes and failures in the tropical bont tick eradication campaigns in the french antilles. | the amblyomma variegatum eradication campaigns, based on three phases and a 5-year program, as in other islands of the caribbean, started in the french antilles in april 1994 with various financial inputs. the progress of the campaigns in the two islands of guadeloupe and martinique contrast sharply. owing to a shortage and inadequacy of results with regard to the initial objectives, particularly in organization, communication efforts, cattle identification, and application of acaricides on live ... | 1998 | 9668485 |
| a trial to control or eradicate amblyomma hebraeum ticks and heartwater on three ranches in zimbabwe. | | 1998 | 9668492 |
| investigating the epidemiology of heartwater (cowdria ruminantium infection) by means of a transmission dynamics model. | a mathematical model of the transmission dynamics of cowdria ruminantium by the ixodid tick amblyomma hebraeum in the bovine host is developed and used to investigate the epidemiology of heartwater across a range of vector challenge. the processes described are supported by empirical data. the pattern of outcome measures (incidence, case-fatality and proportion of infected hosts) predicted agrees with those described anecdotally from field experience and empirical observation, and demonstrates t ... | 1998 | 9695100 |
| demonstration of a carrier state for cowdria ruminantium in wild ruminants from africa. | four wild african ruminants, eland (taurotragus oryx), giraffe (giraffa camelopardalis), kudu (tragephalus strepsiceros strepsiceros), and blue wildebeest (connochaetes taurinus), were experimentally infected with the rickettsia cowdria ruminantium, the tickborne agent causing heartwater in domestic ruminants. the infections were established, and c. ruminantium was transmitted to naive small ruminants by the vector amblyomma hebraeum when transmission attempts were made at days 128 (eland and wi ... | 1998 | 9706566 |
| immunization of rabbits with amblyomma hebraeum nymphal homogenates and implications for the host amplification system. | immunochemical mechanisms involved in tick rejection by a host are not well documented. the role of serum globulins, and that played by the amplification system's humoral products (thrombin from the coagulation, plasmin from the fibrinolytic, and kallikrein from the kinin systems) in tick-resistant animal hosts have not yet been demonstrated. it is known, however, that factors c1, c3 and c5 of the complement system play a role in tick rejection, and that factors c3a and c5a are anaphylatoxins ca ... | 1998 | 9741053 |
| the distribution of heartwater in the highveld of zimbabwe, 1980-1997. | heartwater, the tick-borne disease caused by the rickettsia cowdria ruminantium has historically been confined to the southern and western lowvelds of zimbabwe. since 1986, however, cases of heartwater have been diagnosed with increasing frequency in the central and eastern regions of the previously heartwater-free highveld plateau. during the same period, collections of the two major tick vectors of heartwater in zimbabwe, amblyomma hebraeum and amblyomma variegatum, were made for the first tim ... | 1998 | 9809322 |
| comment on "a possible explanation of the apparent breed-related resistance in cattle to bont tick (amblyomma hebraeum) infestations" by m.i. meltzer, veterinary parasitology 67 (1996) 275-279. | | 1998 | 9823067 |
| validation of the indirect map1-b enzyme-linked immunosorbent assay for diagnosis of experimental cowdria ruminantium infection in small ruminants. | the major antigenic protein 1 fragment b (map1-b) enzyme-linked immunosorbent assay (elisa) for the diagnosis of cowdria ruminantium infections was validated to determine cutoff values and evaluate its diagnostic performance with sheep and goat sera. cowdria-infected populations consisted of 48 sheep and 44 goats, while the noninfected populations consisted of 64 sheep and 107 goats. cutoff values were determined by two-graph receiver-operating characteristic (tg-roc) curves. the cutoff value wa ... | 1999 | 9874666 |
| dna binding properties of the ecdysteroid receptor in the salivary gland of the female ixodid tick, amblyomma hebraeum. | salivary gland degeneration in the female tick, amblyomma hebraeum koch (acari: ixodidae) is controlled by an ecdysteroid hormone. in an earlier study (mao, h., mcblain, w.a., kaufman, w.r., 1995. some properties of the ecdysteroid receptor in the salivary gland of the ixodid tick, amblyomma hebraeum. gen. comp. endocrinol. 99, 340-348), we demonstrated that a protein component of a salivary gland extract binds to ponasterone a (pon a) with high affinity (kd-1 nm), suggesting a tick ecdysteroid ... | 1998 | 9887511 |
| [two cases of spotted fever group rickettsiosis contracted in southern parts of africa]. | a 40-year-old japanese male stayed in zimbabwe and developed a fever above 38 degrees c during which he noted a typical eschar in the lumbar region and also regional inguinal lymphadenopathy. although not conspicuous, erythematous eruptions accompanied by itching were observed on the face, trunk and lower extremities. after returning to japan and visiting our hospital, he was suspected of rickettsiosis and put on minocycline which gradually led to the improvement of the symptoms. immunofluoresce ... | 1998 | 9916419 |
| distributions of the vectors of heartwater, amblyomma hebraeum and amblyomma variegatum (acari: ixodidae), in zimbabwe. | the tick vectors of heartwater (cowdria ruminantium infection) in zimbabwe, amblyomma hebraeum and amblyomma variegatum, historically were believed to be confined to the low-lying regions of the south and north-west of the country. however, country-wide surveys performed in 1975-1980 and 1988-1991 demonstrated that both species were also established in western parts of the highveld plateau and had started to encroach on the predominantly heartwater-free central and eastern highveld regions. to d ... | 1998 | 10030008 |
| restriction of major surface protein 2 (msp2) variants during tick transmission of the ehrlichia anaplasma marginale. | anaplasma marginale is an ehrlichial pathogen of cattle that establishes lifelong persistent infection. persistence is characterized by rickettsemic cycles in which new a. marginale variant types, defined by the sequence of the expressed msp2 transcripts, emerge. the polymorphic msp2 transcripts encode structurally distinct msp2 proteins and result in an antigenically diverse and continually changing a. marginale population within the blood. in this manuscript, we used sequence analysis of msp2 ... | 1999 | 10077656 |
| evaluation of 16s, map1 and pcs20 probes for detection of cowdria and ehrlichia species. | a panel of 16s ribosomal rna gene probes has been developed for the study of the epidemiology of heartwater; five of these detect different cowdria genotypes, one detects five distinct genotypes; one detects any group iii ehrlichia species other than cowdria and one detects any group ii ehrlichia species. these probes have been used on pcr-amplified rickettsial 16s rrna genes from over 200 amblyomma hebraeum ticks. control ticks were laboratory-reared and either uninfected or fed on sheep experi ... | 1999 | 10355799 |
| susceptibility and carrier status of impala, sable, and tsessebe for cowdria ruminantium infection (heartwater). | three species of wild african ruminants, impala (aepyceros melampus), sable (hippotragus equinus), and tsessebe (damaliscus lunatus), were experimentally inoculated with in vitro culture-derived cowdria ruminantium organisms, the tick-borne causative agent of heartwater in domestic ruminants, to determine their susceptibility to infection. no clinical disease was observed in any of the ruminants. however, c. ruminantium was detected in the sable by the transmission of heartwater to susceptible s ... | 1999 | 10386439 |