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ticks from the african buffalo (syncerus caffer) in ngamiland, botswana.in november 1972, 93 out of 100 african buffalo from 3 areas in ngamiland, botswana, were found to be infested with ticks. the tick species present and the percentage of buffalo infested by each were: hyalomma truncatum (63%), h. rufipes (54%), rhipicephalus evertsi evertsi (68%), r. tricuspis (11%), r. simus (4%) and boophilus decoloratus (1%). the mean number of ticks per animal was 8,6 (standard deviation +/-4,1), representing a mean of 6,5+/-3,4 male and 2,1+/-1,9 female ticks. the incidence ...1976940665
arthropod parasites of springbok, gemsbok, kudus, giraffes and burchell's and hartmann's zebras in the etosha and hardap nature reserves, namibia.a total of 48 springbok, 48 gemsbok, 23 kudus and 6 giraffes were examined for ticks and lice, while 9 burchell's zebras and 6 hartmann's mountain zebras were examined only for ticks. springbok and gemsbok were shot in both the etosha national park in the north and the hardap nature reserve in the south of namibia. all the other animals were shot in the etosha national park. a total of 7 ixodid tick species and 8 lice species were recovered. the springbok carried few ticks. the adults of a rhipi ...19921297955
parasites of domestic and wild animals in south africa. xxxi. adult ixodid ticks on sheep in the cape province and in the orange free state.four to 10 dorper sheep on each of 12 farms in the cape province and 3 farms in the orange free state were examined for adult ixodid ticks at approximately 2- to 4-weekly intervals over periods varying from 4 to 18 months, commencing during january, february or april 1989. the farms in the cape province were located in the north-west, south-west and south of the province. those in the orange free state were situated in the north-east and in the south. the sheep in the cape province harboured 10 ...19921297957
the identification of a shared immunogen present in the salivary glands and gut of ixodid and argasid ticks.the identification of a 70-kda immunogen present in salivary gland extracts of several ixodid species, namely hyalomma truncatum (sweating-sickness-inducing (ss+) and non-inducing (ss-) strains), hyalomma marginatum rufipes and rhipicephalus evertsi evertsi, is reported. the immunogen was identified by western blots using a monoclonal antibody of the igm isotype directed against a 70-kda immunogen present in the salivary glands of (ss-) female h. truncatum ticks. cross-reactivity with the gut of ...19921446571
feeding efficiency of larval hyalomma truncatum (acari: ixodidae) on hosts previously exposed to ticks.the effect of guinea pig response to feeding larval hyalomma truncatum koch ticks was studied by measuring the percentage of ticks engorging and molting, their engorged weight, and hemoglobin content. four guinea pigs were infested with 100, 200, 400, and 1,000 larvae, respectively, on three occasions at 21-d intervals, followed by a fourth infestation with 500 larvae. during the second, third, and fourth infestations, significantly fewer ticks engorged on each guinea pig than during the first i ...19921495048
parasites of domestic and wild animals in south africa. xxix. ixodid ticks on hares in the cape province and on hares and red rock rabbits in the orange free state.one hundred and seventeen scrub hares, lepus saxatilis, were examined for ixodid ticks in various regions of the cape province. they were infested with 18 tick species and the seasonal abundances of the immature stages of amblyomma hebraeum, amblyomma marmoreum, hyalomma marginatum rufipes, rhipicephalus appendiculatus and rhipicephalus glabroscutatum and all stages of rhipicephalus oculatus and the adults of a rhipicephalus sp. (near r. oculatus) were determined. seventy-two scrub hares on 3 fa ...19911780126
crimean-congo haemorrhagic fever virus replication in adult hyalomma truncatum and amblyomma variegatum ticks.the kinetics of the replication of the crimean-congo haemorrhagic fever virus (cchfv) was studied in intra-anally inoculated adult hyalomma truncatum and amblyomma variegatum ticks. the virus was re-isolated by suckling mouse inoculation and revealed by antigen capture with ground ticks and indirect immunofluorescence of haemolymph. the virus was detected in ticks in the first hours post-inoculation (p.i.) and its replication was observed from 36 h p.i. onwards. virus titre reached a maximum wit ...19911803413
the isolation and transmission of an unidentified babesia sp. to cattle by hyalomma truncatum koch 1844.an unidentified babesia sp. which causes a mild disease in cattle was isolated in a splenectomized ox that received pooled blood from field cattle. that this organism is pleomorphic and resembles babesia occultans makes it difficult to differentiate between these organisms microscopically. initially, it was suspected that this babesia could be b. occultans. several attempts to transmit this parasite transovarially with hyalomma marginatum rufipes, the vector of b. occultans, failed. continued ef ...19902293131
increased pathogenicity of an ehrlichia-like agent after passage through amblyomma hebraeum: a preliminary report.after being passaged through 3 generations of amblyomma hebraeum, an ehrlichia-like agent isolated from an adult hyalomma truncatum female became more pathogenic and elicited a disease in sheep indistinguishable from heartwater. cross-immunity between this agent and several stocks of cowdria ruminantium and high levels of antibody elicited by the agent against 2 stocks of c. ruminantium in the indirect fluorescent antibody test, confirmed its close relationship to cowdria.19902293132
experimental transmission of crimean-congo hemorrhagic fever virus by hyalomma truncatum koch.larval hyalomma truncatum ticks were infected with crimean-congo hemorrhagic fever (cchf) virus by allowing them to engorge on viremic newborn mice. the overall tick infection rate was 4.4% (24/542). virus was detected in specimens for greater than or equal to 160 days postinfection. transstadial transmission to the adult tick stage was observed and horizontal transmission to a mammalian host was demonstrated. horizontal transmission of cchf virus to uninfected adult ticks occurred while feeding ...19892493203
transstadial and horizontal transmission of rift valley fever virus in hyalomma truncatum.we exposed hyalomma truncatum and rhipicephalus appendiculatus to rift valley fever (rvf) virus in order to assess the possible role of these ticks as enzootic/epizootic rvf vectors. the virus replicated in h. truncatum after intracoelomic inoculation, and a minimum transmission rate of 17% was achieved after 15 days intrinsic incubation. the virus persisted at least 58 days in these ticks. virus was also shown to pass transstadially from inoculated h. truncatum nymphs to adults, with peak viral ...19892802027
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 ...19883391338
[experimental transmission of monanema nilotica el bihari & coll., 1977, a filaria with skin-dwelling microfilaria parasitic in african murids].the value of monanema of murids as experimental models of ocular lesions due to onchocerciasis would be greatly increased if we could experiment with several host and parasite species since, in many cases, the lesions induced are more significant when the host-parasite association is poorly adapted. the life cycle of 2 isolates of monanema nilotica is completed, one from lemniscomys striatus from the central african republique and the other from arvicanthis niloticus of mali. as in m. globulosa, ...19853985535
[1st isolation of a strain of rickettsia (cocksiella) burneti from ticks (hyalomma truncatum) in senegal]. 19704931489
parasites of domestic and wild animals in south africa. xv. the seasonal prevalence of ectoparasites on impala and cattle in the northern transvaal.the prevalence of ectoparasites on a total of 36 impala (aepyceros melampus) slaughtered monthly from february 1975 to february 1976 and a total of 24 cattle slaughtered monthly from march 1976 to march 1977 in the nylsvley provincial nature reserve was determined. six species of ixodid ticks were collected from the impala and these, in order of abundance, were: rhipicephalus evertsi evertsi, rhipicephalus appe. diculatus, amblyomma hebraeum, boophilus decoloratus, ixodes cavipalpus and hyalomma ...19827177586
comparison of characteristics of life cycle in female ticks collected on n'dama and zebu cattle.characteristics of the life cycle of female ticks (amblyomma variegatum, hyalomma truncatum and boophilus geigyi) fed on n'dama and zebu cattle were studied in the laboratory from pre-oviposition period to larval development. percentage of a. variegatum eggs hatched and engorgement weight of h. truncatum were lower in ticks collected on n'dama than on zebu cattle. laboratory results confirmed field observations of species specific tick resistance in the n'dama breed.19957502345
delayed-type hypersensitivity test for assessing tick-immune status of cattle in zambia.delayed-type hypersensitivity skin reactions were used to assess the tick resistance status of tonga calves in zambia. the antigen used in the tests was a homogenate of unfed nymphal rhipicephalus appendiculatus which had been shown to give protective immunity in guinea pigs to adult female r appendiculatus. there was a significant negative correlation between the intensity of the reactions and the total number of ticks (amblyomma variegatum, r appendiculatus, hyalomma truncatum, boophilus decol ...19892773195
control of induced infestations of three african multihost tick species with sustained-release ivermectin.the efficacy of ivermectin, released intraruminally from a 28-day-delivery device was evaluated in two titration studies against induced infestations of adult rhipicephalus appendiculatus, r. evertsi and hyalomma truncatum on cattle. cattle were given a sufficient number of devices to release ivermectin at approximately 20, 40, 60 or 80 micrograms kg-1 day-1 at a steady-state rate 7-28 days after administration. tick mortality was recorded, engorged female ticks were weighed and individually inc ...19892766895
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 ...19947932595
[ticks and hemoparasitoses of livestock in senegal. vi. the soudano-sahelian zone].the authors report the results of a study on ticks and hemoparasitoses among cattle, sheep and goats in the sudano-sahelian zone. during a period of 15 months, ticks were systematically removed from 40 cattle, 40 sheep and 40 goats in order to assess the population dynamics and determine more accurately the preferential sites of settlement of the different species. the following species were collected in ruminants: hyalomma truncatum, h. marginatum rufipes, rhipicephalus evertsi evertsi, rh. gui ...19947991897
[ticks and hemoparasitoses in livestock in senegal. v. the northern guinea area].the authors report the results of a study on ticks and hemoparasitoses among cattle, sheep and goats in the north-guinean zone. during a period of 15 months, ticks were systematically removed from 40 cattle, 40 sheep and 40 goats in order to assess the population dynamics and to determine more accurately the preferential sites of settlement of the following different species collected from these animals: amblyomma variegatum, boophilus geigyi, hyalomma truncatum, h. marginatum rufipes, rhipiceph ...19938073170
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 ...19938134623
the transovarial transmission of babesia caballi by hyalomma truncatum.babesia caballi, isolated from a horse that originated from south west africa/namibia, was transmitted transovarially by adult hyalomma truncatum. b. caballi proved to be highly infective for adult h. truncatum. forty-five per cent of ticks feeding on a reacting animal with an extremely low parasitaemia became infected. in spite of a low parasitaemia, the ticks were severely affected by the parasite. seventy per cent of the infected ticks either died during oviposition or after laying only a few ...19902339004
parasites of cattle in the south western orange free state.a number of young friesian oxen were slaughtered (one at a time) for parasite recovery for 12 consecutive months, from april 1987 to march 1988, on a farm in the fauresmith district of the south western orange free state. a total of 5 ixodid and one argasid tick species, 2 lice species, plus one nematode species and one cestode species, were recovered. peak numbers of adult hyalomma marginatum rufipes were present from november 1987 to february 1988, while the largest numbers of hyalomma truncat ...19902269986
[ticks and hemoparasitic diseases in cattle in senegal. iv. the southern sudan area].the authors report on the results of an investigation on ticks and hemoparasitoses of cattle, sheep and goats in the south sudanian area of senegal. systematic routine dipping against ticks of cattle, 40 sheep and 40 goats was set during 15 months, with a view to determine the population dynamics together with an acurate localization of the different species concerned. the following parasites were collected from these ruminants: amblyomma variegatum, boophilus geigyi, hyalomma truncatum, h. m. r ...19902218038
feeding nymphs of hyalomma truncatum (acari: ixodidae) on guinea pigs previously exposed to nymphs.the ability of nymphal hyalomma truncatum koch to feed on guinea pigs previously exposed to nymphal ticks was studied by measuring the percentage of ticks engorging and molting, their engorged weight, and hemoglobin content. four guinea pigs were infested with 20, 40, 80, and 200 nymphs, respectively, on three occasions at 21-d intervals, followed by a fourth infestation after another 21-d interval with 100 nymphs. guinea pigs originally infested with 20 and 80 nymphs were infested a fifth time ...19938271249
laboratory biology of hyalomma truncatum (acari: ixodidae).the life cycle of hyalomma truncatum koch (acari: ixodidae) required an average of 108 d at 26 +/- 1 degree c. 92-96% rh, and a 12:12 (l:d) photoperiod to complete. mean weights of unfed larvae, nymphs, and females were 0.02, 0.19, and 11.1 mg, respectively. weight of larvae, nymphs, and females increased 20-, 91-, and 48-fold, respectively, as a result of feeding on guinea pigs. all stages exhibited host-seeking behavior less than 1 d after emergence. the mean (+/- se) feeding period of larvae, ...19912056512
sweating sickness: relative curative effect of hyperimmune serum and a precipitated immunoglobulin suspension and immunoblot identification of proposed immunodominant tick salivary gland proteins.although of low morbidity, sweating sickness is readily induced in calves by infestation with positive hyalomma truncatum adult ticks. this epitheliotrophic disease has no specific cure except by the administration of hyperimmune serum obtained from animals which have recovered and are subsequently immune to the disease. treatment with hyperimmune serum, however, has associated problems of donor availability, possible serum contamination and i.v. administration of a relatively large volume. this ...19911923386
viraemic transmission of crimean-congo haemorrhagic fever virus to ticks.in order to determine the way in which vertebrates infected with crimean-congo haemorrhagic fever (cchf) virus and potential ixodid tick vectors interact in nature, immature and adult ticks of several species were fed on viraemic mammals and then assayed for virus content at varying times after feeding. cchf virus was not isolated from ticks of six species tested after feeding as adults and immature forms on sheep with viraemia of 10(2.5-3.2) ld 50/ml, nor from larval ticks fed on guinea-pigs an ...19911902186
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 ...19958551500
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 ...19958600436
the role of hyalomma ticks in foot infestations and temporary lameness of sheep in a semi-arid region of south africa.an outbreak of lameness amongst merino lambs, associated with the presence of hyalomma ticks, was investigated on a farm in the south-western free state, south africa. the purpose was to follow the progress of the condition and to determine the extent of involvement of the two hyalomma species which occur in the region. the flock of experimental sheep (n = 460) ranged free in natural veld under extensive farming conditions. during september and october 1993, adult ewes and lambs in this flock we ...19958628574
attachment preferences of hyalomma truncatum and hyalomma marginatum rufipes ticks (acari: ixodidae) on two sheep breeds.hyalomma ticks were collected from merino and black-headed dorper sheep and their attachment preferences determined. the preferred site of attachment for hyalomma marginatum rufipes on both dorper and merino sheep was the anogenital and inguinal areas (75-76%). on dorper sheep, h. truncatum attached predominantly to the anogenital and inguinal areas (67.7%). on merino sheep, most adults of this species attached to the feet (26%). almost equal percentages also attached to the anogenital/inguinal ...19958628576
transmission of crimean-congo haemorrhagic fever virus from experimentally infected sheep to hyalomma truncatum ticks.crimean-congo haemorrhagic fever (cchf) virus was inoculated into west african sheep that were simultaneously infested with adult hyalomma truncatum ticks. certain sheep developed a viraemia and antibodies, indicating virus infection and replication; however, the length and magnitude of the viraemia and serological responses corresponded to the animals' immunological status. tick attachment and feeding was not influenced by sheep infection. cchf virus infection was acquired by 11-33% of female a ...19911771294
sexual and transovarian transmission of crimean-congo haemorrhagic fever virus in hyalomma truncatum ticks.male hyalomma truncatum ticks were inoculated with crimean-congo haemorrhagic fever (cchf) virus, hypostomectomized and then allowed to mate with uninfected females feeding on a naive rabbit. after mating, cchf virus was reisolated from 2 out of 3 males tested and from 4 of 6 mated, engorged females (titre greater than or equal to 2.2 log ld50/ml). vertical transmission was then demonstrated by virus reisolation from a portion of 2 of the 6 batches of eggs laid by the positive females. from thes ...19921565850
replication and tissue tropisms of crimean-congo hemorrhagic fever virus in experimentally infected adult hyalomma truncatum (acari: ixodidae).adult hyalomma truncatum koch ticks were inoculated intracoelomically with crimean-congo hemorrhagic fever (cchf) virus to examine tissue tropisms of this virus in ticks. virus was recovered from all 185 ticks examined between 2 and 42 d after inoculation with cchf virus. titers or virus recovered from unfed male and female ticks were essentially the same (means, 10(2.4) and 10(2.5) plaque-forming units [pfu] per tick, respectively). infection rates and titers recovered per gland for both saliva ...19921404255
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 ...19979249695
a sero-epidemiological survey of equine piroplasmosis in the northern and eastern cape provinces of south africa.serum samples from yearling thoroughbred horses (n = 176) in the magisterial districts of colesberg, venterstad, and wodehouse in the northern and eastern cape provinces were collected between september and november 1995 to determine the prevalence of antibodies to babesia equi and babesia caballi in these regions. samples were examined for specific antibodies using the indirect fluorescent antibody test. the 95% confidence intervals for the prevalence of serum antibodies in the 3 districts comb ...19969284032
indigenous and crossbred cattle--a comparison of resistance to ticks and implications for their strategic control in zimbabwe.a comparison of the tick resistance of indigenous mashona and crossbred afrikander x sussex oxen following natural tick infestation indicated that significantly more african blue ticks boophilus decoloratus were found on the crossbred than the indigenous cattle (p < 0.05). the two groups of cattle were exposed to babesia bigemina and theileria taurotragi as indicated by high antibody titres on the indirect fluorescent antibody test, but no antibodies could be demonstrated to anaplasma marginale ...19921305338
hyalomma truncatum (acari; ixodidae): evidence for the inability of adult ticks to discriminate between colours.behavioural investigations into the perception and differentiation of coloured objects by unfed adult hyalomma truncatum ticks revealed that silhouettes of blue, green, red and yellow colour, under illumination by a sun-simulating waveband spectrum, are perceived by the ticks and responded to equally by a directed response. two green or dark grey rectangles each with a luminance contrast ratio of 5:1 against the white wall of the test arena in combination with an overlapping, equally sized dark ...19957634970
african swine fever virus infection in the argasid host, ornithodoros porcinus porcinus.the pathogenesis of african swine fever virus (asfv) infection in ornithodoros porcinus porcinus was examined in nymphal ticks infected with the asfv isolate chiredzi/83/1. at times postinfection (p.i.) ranging from 6 h to 290 days, ticks or dissected tick tissues were titrated for virus and examined ultrastructurally for evidence of virus replication. the asfv infection rate in ticks was 100% in these experiments, and virus infection was not associated with a significant increase in tick mortal ...19989499019
sweating sickness in adult cattle.a kenyan strain of hyalomma truncatum was shown to cause sweating sickness in adult cattle in the laboratory. the typical lesions of moist eczema and mucous membrane changes were accompanied by a marked fall in circulating leucocytes with a severe neutropenia. although all cattle recovered, some suffered a severe clinical disease and recovery was slow. recovered cattle were immune to toxicosis 1 year later.19807414698
seasonal prevalence of ixodid ticks on cattle in the windhoek district of south west africa/namibia.the seasonal prevalence of ixodid ticks was determined over a 2-year period by the weekly removal from at least 5 cattle of all adult ticks and the immature stages of rhipicephalus evertsi mimeticus in the ears. the highest mean weekly burden was 286,6 adult ticks/cow/week in march 1979, and the lowest 6,9 adult ticks/cow/week in july 1979. virtually no tick control is practised in this area. rhipicephalus capensis group adults peaked in the summer from october to march/april. rhipicephalus ever ...19846533509
[experimental transmission of crimean-congo hemorrhagic fever virus: role of 3 vector species in the maintenance and transmission cycles in senegal].in this article, we published the role of three species of ticks amblyomma variegatum (fabricius, 1974), hyalomma marginatum rufipes (koch, 1844) and hyalomma truncatum (koch, 1844) in the maintenance and transmission of the cchf virus. the imagos of these species were infected by intracoelomic route. vertical transmission (transtasial and transovarial) and horizontal transmission for different stases were studied by isolation on newborn mice, polymerase chain reaction, indirect immunofluorescen ...199910229934
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 ...19937970571
new and earlier records of ticks (acari: ixodidae, argasidae) from guinea-bissau.ticks were collected from pastures and domestic and wild vertebrates during the rainy seasons of 1994 and 1996 in guinea-bissau. we collected the following species: from pastures rhipicephalus lunulatus neumann, r. muhsamae morel & vassiliades, r. senegalensis koch, and r. sulcatus neumann; from reptiles amblyomma nuttalli dönitz and aponomma flavomaculatum (lucas); and from mammals amblyomma paulopunctatum neumann, amblyomma splendidum giebel, amblyomma variegatum (f.), hyalomma truncatum koch, ...200011126561
the fine structure of developmental stages of babesia caballi in the salivary glands of hyalomma truncatum.the development of babesia caballi in the salivary glands of hyalomma truncatum was studied at the electron microscopic level. kinetes were first observed in the salivary glands of ticks on day 2 of tick feeding and on each subsequent day of feeding until engorgement on day 8. sporogony appeared to involve the formation of cytomeres. after continued nuclear division, sporozoites formed when individual rounded nuclei were incorporated into portions of cytoplasm. sporozoites were first observed on ...19892812703
feeding patterns of immature stages of hyalomma truncatum and hyalomma marginatum rufipes on different hosts.in this study we examine the feeding patterns of immature stages of hyalomma truncatum and hyalomma marginatum rufipes ticks on different hosts. larvae of h. truncatum developed through a three-host pattern on two species of field mice, rhabdomys pumilio and lemniscomys rosalia. on guinea-pigs, both hyalomma species followed a mixed two-host and three-host pattern, with the latter route being preferred, since more than 70% of the fully fed larvae dropped off from their hosts. h. truncatum was a ...200011110240
observations on cattle ticks in huila province (angola).in huila province of angola, 3864 ticks were collected during a parasitological survey carried out in the rainy season from october 1990 to april 1991. the samples were collected from cattle gathered for the annual vaccination campaign against contagious bovine pleuropneumonia, anthrax and blackleg in 18 veterinary stations of six municipalities. after tick classification, the following proportions of ticks were obtained: rhipicephalus evertsi mimeticus (27.1%), amblyomma pomposum (26.4%), booph ...19948171837
ixodid ticks feeding on humans in south africa: with notes on preferred hosts, geographic distribution, seasonal occurrence and transmission of pathogens.this paper records the identities of 558 ixodid ticks feeding on 194 humans in south africa. these ticks belonged to 20 species in six genera and those most frequently encountered were amblyomma hebraeum, haemaphysalis leachi, hyalomma marginatum rufipes, hyalomma truncatum, rhipicephalus appendiculatus, rhipicephalus gertrudae and rhipicephalus simus. with the exception of the larvae of r. appendiculatus, the incidents of these ticks feeding on humans correlated well with their seasonal occurre ...200212593517
on the reaction of adult rhipicephalus evertsi mimeticus and hyalomma truncatum to horizontally incidenting optical radiation of various wavelengths ranges and different irradiances and to optical radiation of a sun-simulating wavelength spectrum.the valence of horizontally incidenting light/optical radiation for host-seeking-inclined ixodid ticks was investigated by exposing male and female adults of rhipicephalus evertsi mimeticus and hyalomma truncatum to narrow-band monochromatic radiation in the wavelength range of 300-801 nm at irradiances corresponding to an overcast to clear sunny day, a cloudy day and a full-moon night as well as to optical radiation of a sun-simulating wavelength spectrum of 190-2600 nm within a test chamber fr ...19911866424
detection of ehrlichia spp., anaplasma spp., rickettsia spp., and other eubacteria in ticks from the thai-myanmar border and vietnam.a total of 650 ticks, including 13 species from five genera, were collected from animals, from people, or by flagging of the vegetation at sites on the thai-myanmar border and in vietnam. they were tested by pcr to detect dna of bacteria of the order rickettsiales: three anaplasma spp. were detected in ticks collected in thailand, including (i) anaplasma sp. strain anda465, which was considered a genotype of anaplasma platys (formerly ehrlichia platys) and which was obtained from dermacentor aur ...200312682151
climate change decreases habitat suitability for some tick species (acari: ixodidae) in south africa.models predicting current habitat availability for four prominent tick species in africa (boophilus decoloratus, amblyomma hebraeum, rhipicephalus appendiculatus and hyalomma truncatum) were constructed using remotely sensed information about abiotic variables and a point-to-point similarity metric. year-to-year variations in the forecasted habitat suitability over the period 1983-2000 show a clear decrease in habitat availability, which is attributed primarily to increasing temperature in the r ...200312967169
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 ...19807413164
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 ...19807452655
observations on the efficacy of ivermectin in the control of cattle ticks in zambia.the efficacy of multiple subcutaneous injections (200 micrograms/kg) of ivermectin in the control of naturally occurring tick infestations on traditionally managed tonga-iia (sanga type) calves and yearlings was assessed in two field trials. in the first trial boophilus decoloratus infestations were decreased following treatments at monthly intervals. in the second trial, with weekly and two weekly treatment intervals, infestations of rhipicephalus appendiculatus were controlled less effectively ...19853841240
a note on hyalomma nitidum, its distribution and its hosts.the paper summarises the morphological characteristics, the known geographical distribution and hosts of hyalomma nitidum, a tick which has never been properly characterised. h. nitidum was first described in cameroon in 1919, long considered as a synonym of hyalomma truncatum and recognised as a separate and valid species only since the early 1970s. h. nitidum occurs from senegal to the central african republic in more humid conditions than h. truncatum, roughly to the south of the isohyet of 9 ...200515969466
simultaneous detection of "rickettsia mongolotimonae" in a patient and in a tick in greece.rickettsia conorii, a spotted fever group rickettsia which is transmitted by rhipicephalus sp. complex ticks, was considered until now the only pathogenic rickettsia prevalent in greece. here, we report the presence of "rickettsia mongolotimonae" (proposed name) detected simultaneously in a patient and in a hyalomma anatolicum excavatum tick, sampled on the patient.200516000506
a study of the justification for intensive tick control in kenyan rangelands.sixty male weaner cattle at the national range research station, kiboko, kenya were placed in four groups of 15 animals under four different tick control regimens for 16 months. the treatment groups were: spraying with acaricide weekly, spraying every three weeks, spraying whenever group mean tick infestations reached more than 200 per animal (once only in the course of the study) and a control unsprayed group. the cattle were weighed monthly. there were no significant differences between the li ...19863798681
tick-borne rickettsioses around the world: emerging diseases challenging old concepts.during most of the 20th century, the epidemiology of tick-borne rickettsioses could be summarized as the occurrence of a single pathogenic rickettsia on each continent. an element of this paradigm suggested that the many other characterized and noncharacterized rickettsiae isolated from ticks were not pathogenic to humans. in this context, it was considered that relatively few tick-borne rickettsiae caused human disease. this concept was modified extensively from 1984 through 2005 by the identif ...200516223955
tickborne arbovirus surveillance in market livestock, nairobi, kenya.to identify tickborne viruses circulating in kenya and the surrounding region, we conducted surveillance at abattoirs in nairobi, kenya. species of ticks collected included rhipicephalus pulchellus (56%), amblyomma gemma (14%), r. appendiculatus (8%), a. variegatum (6%), and others. a total of 56 virus isolates were obtained, 26 from a. gemma, 17 from r. pulchellus, 6 from a. variegatum, and 7 from other species. virus isolates included dugbe virus (dugv), an unknown virus related to dugv, thogo ...200616836823
ecology and phenology of ticks in zambia: seasonal dynamics on cattle.a study of the seasonality and infestation rates of ticks was carried out in 11 cattle herds in different ecological habitats in zambia between 1980 and 1982. wherever possible supplementary data were obtained from opportunistic collections from cattle and other hosts. analysis of over 1000 tick collections from cattle indicated that infestation rates of the most important species, amblyomma variegatum and rhipicephalus appendiculatus vary in different ecological habitats: (i) in western provinc ...19863451861
tick-borne rickettsial pathogens in ticks and small mammals in korea.in order to investigate the prevalence of tick-borne infectious agents among ticks, ticks comprising five species from two genera (hemaphysalis spp. and ixodes spp.) were screened using molecular techniques. ticks (3,135) were collected from small wild-caught mammals or by dragging/flagging in the republic of korea (rok) and were pooled into a total of 1,638 samples (1 to 27 ticks per pool). from the 1,638 tick samples, species-specific fragments of anaplasma phagocytophilum (1 sample), anaplasm ...200616957192
isolation and characterization of an anticoagulant present in the salivary glands of the bont-legged tick, hyalomma truncatum.a low molecular mass anticoagulant (17 kda) was isolated from the salivary glands of prefed female hyalomma truncatum ticks by means of reverse phase and anion-exchange hplc. trypsin digestion and amino acid analysis confirmed the protein nature of the anticoagulant. the inhibitor appears to be uncompetitive with a ki of 6.9 x 10(-10)m. the target of the anticoagulant is factor xa at the junction of the extrinsic and intrinsic pathways. this may be crucial for the survival of the tick, making it ...19957656731
antigen-capture enzyme-linked immunosorbent assay for detection and quantification of crimean-congo hemorrhagic fever virus in the tick, hyalomma truncatum.a viral antigen-capture elisa was compared to a viral plaque-assay on human cell monolayers for detection and quantification of crimean-congo hemorrhagic fever virus in triturated experimentally infected hyalomma truncatum ticks. in suspensions of ticks exposed as larvae to viremic mice, the elisa detected 13% positive as compared to 3% (n = 721) positive by plaque-assay. adult ticks inoculated with virus and sampled up to 102 days later were 84% positive by elisa compared to 36% (n = 273) posit ...19938320308
the scrub hare, a reliable indicator of the presence of hyalomma ticks in the cape province.the host preferences of immature and adult hyalomma marginatum rufipes, hyalomma marginatum turanicum and hyalomma truncatum were studied at various localities in the cape province. the immature stages of all 3 ticks preferred scrub hares (lepus saxatilis) as hosts and were recovered from these animals even when few adult ticks were present on large herbivores in the locality. ground-frequenting birds were also infested, but only with immature h. marginatum rufipes and h. marginatum turanicum. s ...19873612673
hyalomma truncatum (acari; ixodidae): investigations into the scototaxis of unfed adult ticks.under controlled test conditions, unfed male and female hyalomma truncatum ticks exhibited a positive scototaxis to stationary, two-dimensional targets. upright-positioned rectangles were the most attractive targets. the attractiveness of these targets increased with their size. significantly more ticks responded scototactically positively to the targets under a luminance contrast ratio of 5:1, as compared with other luminance contrast ratios. targets with an elevation angle of 13 degrees were o ...19957621712
distribution and population dynamics of ticks (acari: ixodidae) infesting sheep in sennar state, sudan.a cross-sectional survey of ticks infesting sheep was conducted in sennar state, sudan. a total body collection of ticks was carried out at five localities sennar town, singa, dinder, abu naama and um banein on two types of desert sheep (watish and ashgar) on two farms at each locality at two monthly intervals for one year starting july 2002 to may 2003. four tick genera and eight species were identified. they were amblyomma lepidum, hyalomma anatolicum anatolicum, hyalomma truncatum, rhipicepha ...200718453239
risk factors for crimean-congo hemorrhagic fever in rural northern senegal.the extent of infection among 722 residents of an enzootic focus of crimean-congo hemorrhagic fever (cchf) virus in rural northern senegal and putative modes of transmission were studied by a cross-sectional seroprevalence survey done from february through may 1989. anti-cchf virus igg was found in 13.1% of 283 persons who completed a standard questionnaire and provided blood samples. seropositivity rates were similar between sexes and increased significantly with age among nomadic persons. beha ...19911910069
a survey of the ixodid ticks parasitising cattle in the eastern province of zambia.the results of tick surveys carried out in the eastern province of zambia between december 1982 and february 1996 were principally in agreement with the findings of earlier surveys conducted during the period 1965-72. boophilus decoloratus has almost been replaced by boophilus microplus. hyalomma truncatum was found in small numbers throughout the province and hyalomma marginatum rufipes was only rarely encountered in collections made from cattle. rhipicephalus evertsi evertsi was largely confin ...19989737594
laboratory transmission of venezuelan equine encephalomyelitis virus by the tick hyalomma truncatum. 19948153988
ixodid ticks infesting domestic goats in communal land areas of zimbabwe.the purpose of this study was to determine the species spectrum of ticks infesting goats owned by resource-limited farmers in the state-owned communal land areas of zimbabwe. ticks were collected from goats at a single locality within each of 5 communal land areas, and a total of 14 ixodid tick species was recovered. the most numerous tick was rhipicephalus evertsi evertsi, which was present in all areas at each sampling, and a rhipicephalus sp. (near r. punctatus), which was most abundant on go ...200819244819
tick toxicosis in a crossbred terrier caused by hyalomma truncatum. 19836636485
ticks associated with the three largest wild ruminant species in southern africa.the objective of this study was to assess the host status of the three largest southern african wild ruminants, namely giraffes, giraffa camelopardalis, african buffaloes, syncerus caffer, and eland, taurotragus oryx for ixodid ticks. to this end recently acquired unpublished data are added here to already published findings on the tick burdens of these animals, and the total numbers and species of ticks recorded on 12 giraffes, 18 buffaloes and 36 eland are summarized and discussed. twenty-eigh ...200717933365
molecules and morphology: evidence for cryptic hybridization in african hyalomma (acari: ixodidae).the role of natural hybridization and introgression as part of the evolutionary process is of increasing interest to zoologists, particularly as more examples of gene exchange among species are identified. we present mitochondrial and nuclear sequence data for hyalomma dromedarii, hyalomma truncatum, and hyalomma marginatum rufipes (acari: ixodidae) collected from one-humped camels in ethiopia. these species are well differentiated morphologically and genetically; sequence data from the mitochon ...200312679078
tick-borne rickettsioses, neglected emerging diseases in rural senegal.rickettsioses are one of the most important causes of systemic febrile illness among travelers from developed countries, but little is known about their incidence in indigenous populations, especially in west africa.201020856858
weight gain, hemoglobin uptake, and virus ingestion by hyalomma truncatum (acari: ixodidae) ticks after engorgement on viremic guinea pigs.the ability of guinea pigs to serve as a source of an arbovirus for feeding ticks was examined with hyalomma truncatum koch and venezuelan equine encephalomyelitis virus. ticks fed on guinea pigs to varying degrees, as indicated by both low and high weight gain and hemoglobin uptake. pools of larval ticks measured at drop-off with undetectable or very low hemoglobin levels (mean hemoglobin content = 0.05 mg per pool) contained the same amount of virus (> 10(3.0) plaque-forming units [pfu] per po ...19948189423
ticks (acari: ixodidae) infesting camels (camelus dromedarius) in northern sudan.monthly total body tick collections from 13-20 camels were conducted for 2 consecutive years (2000-2001) in northern sudan. tick populations were correlated with locality, season, predeliction site, sex and coat colour. hyalomma dromedarii was found to be the predominant (89%) tick species infesting the camels. other tick species found in very low numbers were hyalomma impeltatum (7.7%), hyalomma anatolicum anatolicum (3.3%), hyalomma truncatum (0.29%), hyalomma marginatum rufipes (0.25%), rhipi ...200920698438
temperature- and humidity-dependent longevity of unfed adult hyalomma truncatum (acari: ixodidae).the survival of unfed adult hyalomma truncatum koch held under different regimes of constant temperature (5, 17, 24, and 30 degrees c) and relative humidity (10, 50, and 80%) was monitored during > 1 yr. longevity of this medically important african tick was shortest at the highest temperature and lowest relative humidity (100% dead at week 25). conversely, h. truncatum lived longest at lower temperatures and higher relative humidity (< 100% dead at week 64). the combined effects of temperature ...19938459425
ticks (acari: ixodidae) infesting cattle and african buffaloes in the tsavo conservation area, kenya.several ixodid tick species are shared between domestic cattle and african buffaloes (syncerus caffer). so too, are a number of tick-borne diseases. the aim of the study was to compare the species composition of ticks that infest cattle and buffaloes utilising the same habitat within the tsavo conservation area, kenya. to this end, 25 cattle and 62 buffaloes were each opportunistically sampled for ticks on a single occasion in february 2010. eight species, namely amblyomma gemma, amblyomma lepid ...201223327329
tick paralysis: regional neurological involvement caused by hyalomma truncatum. 195913836026
tick infestation, and udder and teat damage in selected cattle herds of matabeleland south, zimbabwe.a cross-sectional survey was conducted to determine tick infestation, and udder and teat damage in 286 lactating cows and heifers at six properties in the smallholder and commercial sectors in gwanda district of matabeleland south province, zimbabwe. eight tick species were identified: amblyomma hebraeum, hyalomma truncatum, hyalomma marginatum rufipes, rhipicephalus evertsi evertsi, rhipicephalus (boophilus) decoloratus, rhipicephalus appendiculatus, rhipicephalus zambeziensis and rhipicephalus ...200920698443
morphology of the eyes in adult hyalomma truncatum ticks (acari: ixodidae).the eyes of hyalomma truncatum ticks are morphologically similar in both sexes. they appear as paired hemispherical structures situated dorsally between the first and second pair of legs on the lateral scutal margin. each eye consists of a lens and photoreceptor cells, which are separated by a fine fibrillar layer and the hypodermis. the lens contains numerous channels which open beneath the epicuticle, converge uninterruptedly to the interior of the lens and end below the fine fibrillar layer. ...19979057303
molecular detection of zoonotic tick-borne pathogens from ticks collected from ruminants in four south african provinces.ticks carry and transmit a remarkable array of pathogens including bacteria, protozoa and viruses, which may be of veterinary and/or of medical significance. with little to no information regarding the presence of tick-borne zoonotic pathogens or their known vectors in southern africa, the aim of our study was to screen for anaplasma phagocytophilum, borrelia burgdorferi, coxiella burnetii, rickettsia species and ehrlichia ruminantium in ticks collected and identified from ruminants in the easte ...201526227797
tick-borne infections in human and animal population worldwide.the abundance and activity of ectoparasites and its hosts are affected by various abiotic factors, such as climate and other organisms (predators, pathogens and competitors) presenting thus multiples forms of association (obligate to facultative, permanent to intermittent and superficial to subcutaneous) developed during long co-evolving processes. ticks are ectoparasites widespread globally and its eco epidemiology are closely related to the environmental conditions. they are obligatory hematop ...201527047089
the effect of various host species in the feeding performance of immature stages of the tick hyalomma truncatum (acari: ixodidae).in order to determine the effect of various hosts on the feeding performance of the tick hyalomma truncatum, were used three mammalian species as hosts. larvae and nymphs of h. truncatum were fed, under controlled laboratory conditions, on gerbils, guinea-pigs and rabbits. the larvae fed for 4.3 +/- 1.4 days on gerbils, 5.6 +/- 1.3 days on guinea-pigs and 4.7 +/- 1.2 days on rabbits. the mean weights of the larvae which fed in the rabbits, guinea-pigs and gerbils were 0.58 +/- 0.09, 0.46 +/- 0.0 ...19979291588
a possible canine tick-bite reaction to ixodes muris.an airedale terrier became acutely ill following attachment of an ixodes muris tick. clinical signs waned within hours of tick removal, similar to a pattern previously documented in animals harboring i. muris. this supports the theory that i. muris can induce a noninfectious, severe inflammatory reaction in domestic animals.200818390101
update on tick-borne rickettsioses around the world: a geographic approach.tick-borne rickettsioses are caused by obligate intracellular bacteria belonging to the spotted fever group of the genus rickettsia. these zoonoses are among the oldest known vector-borne diseases. however, in the past 25 years, the scope and importance of the recognized tick-associated rickettsial pathogens have increased dramatically, making this complex of diseases an ideal paradigm for the understanding of emerging and reemerging infections. several species of tick-borne rickettsiae that wer ...024092850
multiple pathogens including potential new species in tick vectors in côte d'ivoire.our study aimed to assess the presence of different pathogens in ticks collected in two regions in côte d'ivoire.201626771308
tick-borne pathogens of zoonotic and veterinary importance in nigerian cattle.ticks and tick-borne diseases undermine cattle fitness and productivity in the whole of sub-saharan africa, including nigeria. in this west african country, cattle are challenged by numerous tick species, especially during the wet season. consequently, several tbds are known to be endemic in nigerian cattle, including anaplasmosis, babesiosis, cowdriosis and theilerioris (by theileria mutans and theileria velifera). to date, all investigations on cattle tbds in nigeria have been based on cytolog ...201627090756
intracellular localization of crimean-congo hemorrhagic fever (cchf) virus glycoproteins.crimean-congo hemorrhagic fever virus (cchfv), a member of the genus nairovirus, family bunyaviridae, is a tick-borne pathogen causing severe disease in humans. to better understand the cchfv life cycle and explore potential intervention strategies, we studied the biosynthesis and intracellular targeting of the glycoproteins, which are encoded by the m genome segment.200515850490
infestation and identification of ixodid tick in cattle: the case of arbegona district, southern ethiopia.the study was conducted from october 2014 to june 2015 to estimate tick prevalence and identify major tick genera infesting cattle and the associated risk factors in arbegona district, southern ethiopia. a total of 2024 adult ticks were collected from main body parts of animals and eight species of ticks which belong to three genera were identified. questionnaire survey was employed concerning the general case on the tick infestation problems on the cattle. from 384 cattle examined, 291 (75.7%) ...201628105466
biological and clinical responses of west african sheep to crimean-congo haemorrhagic fever virus experimental infection.west african sheep appear to play a central role as virus hosts in the maintenance cycle of crimean-congo haemorrhagic fever (cchf) virus in endemic areas and also because of their role as a principal host of the cchf virus tick vector. in an effort to clarify cchf epidemiological significance in sheep, we studied the biological and clinical aspects of sheep experimentally infected with cchf virus. west african sheep breeds were infected either by intraperitoneal inoculation or by infestation wi ...19989923021
importance of ticks and their chemical and immunological control in livestock.the medical and economic importance of ticks has long been recognized due to their ability to transmit diseases to humans and animals. ticks cause great economic losses to livestock, and adversely affect livestock hosts in several ways. loss of blood is a direct effect of ticks acting as potential vector for haemo-protozoa and helminth parasites. blood sucking by large numbers of ticks causes reduction in live weight and anemia among domestic animals, while their bites also reduce the quality of ...017048307
coevolutionary analyses of the relationships between piroplasmids and their hard tick hosts.host-parasite coevolution is a key driver of biological diversity. to examine the evolutionary relationships between piroplasmids and their hard tick hosts, we calculated the molecular clock and conducted phylogenetic analyses of both groups. based on our results, we conclude that the divergence time of piroplasmids (∼56 mya) is later than divergence time of their hard tick hosts (∼86 mya). from analyses of the evolution of both piroplasmid and vector lineages and their association, we know that ...201324101988
morphological characteristics of normal and gynandromorphic hyalomma asiaticum schulze and schlottke, 1930.gynandromorphic ticks are extremely rare, and often attract parasitologists' attention. during our examination of tick specimens, an engorged gynandromorph of hyalomma asiaticum was noticed. this is the first record of gynandromorphic ticks from china. in this study, several important morphological structures of normal and gynandromorphic h. asiaticum were analyzed. comparing to the normal h. asiaticum, the gynandromorphic specimen was a typical bipartite protogynander. its right side showed nor ...201526174833
lumpy skin disease: attempted propagation in tick cell lines and presence of viral dna in field ticks collected from naturally-infected cattle.lumpy skin disease (lsd) is of substantial economic importance for the cattle industry in africa and the near and middle east. several insect species are thought to transmit the disease mechanically. recent transmission studies have demonstrated the first evidence for a role of hard (ixodid) ticks as vectors of lumpy skin disease virus (lsdv). the aim of this study was to attempt in vitro growth of the virus in rhipicephalus spp. tick cell lines and investigate in vivo the presence of the virus ...201425468765
tick diversity, abundance and seasonal dynamics in a resource-poor urban environment in the free state province.the objectives of this study were to determine the diversity, seasonal dynamics and abundance of ticks infesting cattle in urban, small-scale farming communities in and around botshabelo and thaba nchu in the eastern free state province, south africa. a total of ten cattle, ear-tagged for individual identification, were investigated monthly at each of five localities. adult ticks were removed from the right hand side of each animal and placed in containers filled with 70% ethanol. they were subs ...199810192844
new data regarding distribution of cattle ticks in the south-western indian ocean islands.recent studies have produced new insight into the origin and distribution of some cattle ticks in the south-western indian ocean islands. rhipicephalus appendiculatus, introduced from tanzania in 2002, is now well established on grande comore but has not yet reached the other islands of the archipelago (mohéli, anjouan and mayotte). only one of the two clades identified in africa has settled so far. amblyomma variegatum, which was not supposed to be able to persist in the antananarivo region (13 ...201324016261
measuring the transmission dynamics of a sexually transmitted disease.sexually transmitted diseases (stds) occur throughout the animal kingdom and are generally thought to affect host population dynamics and evolution very differently from other directly transmitted infectious diseases. in particular, stds are not thought to have threshold densities for persistence or to be able to regulate host population density independently; they may also have the potential to cause host extinction. however, these expectations follow from a theory that assumes that the rate of ...200516204382
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