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serological survey of heartwater relative to the distribution of the vector amblyomma variegatum and other tick species in north cameroon.a study was carried out on the spatial and temporal distribution of amblyomma variegatum and other ticks infesting sheep and goats in northern cameroon. a serological survey of heartwater (cowdriosis) using a competitive elisa was concurrently carried out in the same flocks. a. variegatum was found to be the most predominant species accounting for 48.3% of all the ticks collected. other species identified included rhipicephalus sulcatus, r. lunulatus, r. turanicus, boophilus decoloratus, b. annu ...19979066062
[asymptomatic carrier state in creole goats and cattle after recovery from cowdria infection in guadeloupe].creole goats and cattle in guadeloupe can be carriers of cowdriosis (heartwater: cowdria ruminantium) after recovery for a period as long as 11 months in goats and 2 months in cattle. the carrier status was demonstrated by feeding amblyomma variegatum nymphs on recovered animals and the resulting adult ticks on susceptible goats. cowdria ruminantium was not detected permanently during the carrier status.19921301623
tick-borne diseases of domestic animals in northern nigeria. ii. research summary, 1966 to 1976.during the first 10 years of its existence, the department of parasitology and entomology of the faculty of veterinary medicine, ahmadu bello university in zaria, nigeria, confirmed or described for the first time the occurrence of 25 different tick-borne parasites of domestic animals in the northern part of the country. most of these organisms occur as inapparent infections but may serve as complicating factors in any adverse host condition. the transmission of babesia bigemina by boophilus dec ...1977339447
comparison of efficacy of american and african amblyomma ticks as vectors of heartwater (cowdria ruminantium) infection by molecular analyses and transmission trials.the ability of amblyomma americanum, amblyomma cajennense, amblyomma maculatum, and amblyomma variegatum to acquire and transmit cowdria ruminantium infection was investigated. uninfected nymphs were fed on clinically reacting c. ruminantium-infected sheep and then analyzed for infection by specific dna detection assays and by tick transmission trials. by polymerase chain reaction (pcr), the mean infection prevalence of a. maculatum ticks (50.7%) was similar to that of a. variegatum, elevage str ...200010701562
a mouse lethal dose assay for detection and titration of cowdria ruminantium (kwanyanga strain) in goats and ticks.a mouse lethal dose assay was used to detect a mouse pathogenic strain (kwanyanga) of cowdria ruminantium, the etiological agent of heartwater in goats and ticks. the titer of the rickettsial organisms in goat blood was directly related to the febrile response of the goat and the rickettsia were undetectable after the fever subsided. the maximum rickettsial titer in goat blood was 10(3) mouse ld50 ml-1. cowdria-infected goat blood was shown to retain infectivity when held on ice for up to 2 h, b ...19892705290
the distribution of ixodid ticks (acari: ixodidae) in central ethiopia.ixodid ticks were collected from domestic animals, mainly cattle, in 11 administrative zones covering 84 districts in central ethiopia over a period of 2 years (july 1996 to june 1998). nineteen tick species were identified. four of these belonged to the genus amblyomma, one to boophilus, two to haemaphysalis, three to hyalomma and nine to rhipicephalus. amblyomma variegatum and rhipicephalus evertsi evertsi were present in all 11 administrative zones and, with the exception of afar, boophilus d ...200112026058
attempts to feed amblyomma variegatum ticks on artificial membranes.feeding jars were used to feed nymphs of amblyomma variegatum on blood of goats or cattle. sterile blood was collected daily or weekly (kept at 4 degrees c or frozen until use), with addition either of heparin alone or of heparin and antibiotics/fungicide or of heparin, adenosine triphosphate and glutathione. membranes were made of a thin (0.12-0.32 mm) film of silicone mastic. blood in the jars was replaced twice a day, and reached a temperature of 39 degrees c in a waterbath before it became a ...19989668493
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 ...19938236490
in vitro feeding of instars of the ixodid tick amblyomma variegatum on skin membranes and its application to the transmission of theileria mutans and cowdria ruminatium.an in vitro feeding method using rabbit or cattle skin membranes, applied successfully to all stages (larvae, nymphae and adults) of the ioxodid tick, amblyomma variegatum, is described. the feeding apparatus consisted of a blood container with a membrane placed on top of a tick containment unit. a carbon dioxide atmosphere of between 5 and 10% and a temperature of 37 degrees c were used as stimulants for the attachment of the ticks. high co2 concentrations in the atmosphere improved the feeding ...19938233589
[epidemiology of cowdria infection in senegal. ii. results of sero-epidemiological follow-up studies].the authors report the results of sero-epidemiological monitoring of zebu, diakoré and ndama cattle in the sahel, niayes and north guinea zones, respectively. calves aged 0-3 or 3-6 months were subjected to blood sampling every three months for a period of 20 months. in the niayes and north guinea zones, the immunofluorescence test showed that about 70% of 0-1 month old calves reacted positively to the cowdria ruminantium antigen, whereas the prevalence was 92% between 3 and 6 months. after the ...19938190981
[epidemiology of cowdria infection in senegal. i. study of the transmission and infection level in amblyomma variegatum (fabricius, 1794) in the niayes region].the authors report the results of research on infection rates of amblyomma variegatum nympha and imago populations by cowdria ruminantium in the niayes region as well as on the transmission rates of a. variegatum by the various stases. the experiments were carried out on sheep from the sahelian zone where the vector tick is not endemic. the infection rate, estimated by inoculating sheep with ground ticks, gave the following prevalences: t = 13.3% for nymphae and t = 1.2% for adults. the transmis ...19938190980
effect of acaricide treatment of cattle on amblyomma variegatum (acari: ixodidae) infestation of mongooses (carnivora: viverridae: herpestes auropunctatus) in guadeloupe, french west indies.the effect of acaricide treatment of cattle on the infestation of the small indian mongoose (herpestes auropunctatus hodgson) by amblyomma variegatum (f.) was determined during a field evaluation of selected acaricides in guadeloupe, french west indies. from april 1990 to april 1991, cattle at one site were treated every 14 d with pour-on formulations of deltamethrin, flumethrin, or permethrin; and cattle at a second site were treated as per a local standard treatment using a spray formulation o ...19948057326
experimental trypanosoma congolense infection on naturally occurring ticks in n'dama and gobra zebu cattle.the effects of experimental trypanosoma congolense infection in gambian n'dama and gobra zebu cattle on number of naturally-occurring adult ticks attaching were studied. an indirect fluorescent antibody test was performed to detect serological prevalence of cowdria ruminantium antibody. the intravenously imposed trypanosome infection did not result in significant (p > 0.05) differences in amblyomma variegatum and hyalomma spp. infestations between control and infected n'dama cattle. control n'da ...19947638002
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 ...19938432329
demonstration of colonies of cowdria ruminantium in midgut epithelial cells of amblyomma variegatum.the development of colonies of cowdria ruminantium was studied in midgut epithelial cells of adult amblyomma variegatum that had become infected by feeding as nymphs on cattle with experimentally induced heart-water disease. colonies were not observed in gut tissues obtained from nymphs during the feeding period, but were present in midgut epithelial cells of ticks obtained at 15 days after they were replete through molting to the adult stage. colonies were small (1 to 10 micron) initially, but ...19873551699
cowdria ruminantium antibodies in acaricide-treated and untreated cattle exposed to amblyomma variegatum ticks in the gambia.an indirect enzyme-linked immunosorbent assay (elisa), based on the major antigenic protein i fragment b (mapi-b) of cowdria ruminantium, was used to assess seroprevalence in cattle in the gambia. two groups of 20 n'dama and 20 gobra zebu cattle were monitored for 12 months with flumethrin treatment and for another 10 months without acaricidal treatment. two groups of 20 n'dama and 20 gobra cattle served as untreated controls. during the period of acaricidal treatment, the cumulative proportions ...200011354623
identification of babesia bovis and cowdria ruminantium on the island of unguja, zanzibar.babesia bovis and cowdria ruminantium were identified for the first time in cattle on unguja island, zanzibar. b bovis is common and widespread, although clinical disease had not been diagnosed previously. the vector of heartwater, amblyomma variegatum, is found throughout unguja but c ruminantium appears to be more localised in distribution than b bovis.19902301128
heartwater in ghana: implications for control of ticks.heartwater, an often fatal rickettsial disease of domestic ruminants transmitted by amblyomma variegatum ticks, ranks with the a. variegatum-associated skin disease dermatophilosis as a major constraint to the upgrading of livestock productivity in ghana. an epidemiological survey, using new diagnostic tests, is being carried out to determine the incidence and distribution of heartwater and other tickborne diseases in ghanaian cattle, sheep and goats. preliminary results from a longitudinal surv ...19968809994
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, ...19947628253
vector situation of tick-borne diseases in the caribbean islands.the most important ticks transmitting diseases to ruminants in the caribbean islands are: amblyomma variegatum, vector of cowdriosis and associated with acute dermatophilosis; amblyomma cajennense, potential vector of cowdriosis; boophilus microplus, vector of babesiosis and anaplasmosis. at the present time, amblyomma variegatum is widespread in the lesser antilles from barbados to puerto rico. the intensity of the tick control program varies in the different islands and the tick infestation in ...19957597781
a cloned dna probe identifies cowdria ruminantium in amblyomma variegatum ticks.heartwater, caused by cowdria ruminantium and transmitted by ticks of the genus amblyomma, is a constraint to ruminant animal production in sub-saharan africa. this rickettsial disease could spread from endemically infected areas of sub-saharan africa and certain caribbean islands to other countries, including the united states, in which amblyomma ticks exist. to detect c. ruminantium in tick vectors and animals, we made dna probes from c. ruminantium dna isolated from endothelial cell cultures. ...19911774264
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 ...199810030008
detection of the agent of heartwater, cowdria ruminantium, in amblyomma ticks by pcr: validation and application of the assay to field ticks.we have previously reported that the pcs20 pcr detection assay for cowdria ruminantium, the causative agent of heartwater disease of ruminants, is more sensitive than xenodiagnosis and the pcs20 dna probe for the detection of infection in the vector amblyomma ticks. here, we further assessed the reliability of the pcr assay and applied it to field ticks. the assay detected dna of 37 isolates of c. ruminantium originating from sites throughout the distribution of heartwater and had a specificity ...200010747140
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 ...19989809322
transcription analysis of the major antigenic protein 1 multigene family of three in vitro-cultured ehrlichia ruminantium isolates.ehrlichia ruminantium, an obligate intracellular bacterium transmitted by ticks of the genus amblyomma, causes heartwater disease in ruminants. the gene coding for the major antigenic protein map1 is part of a multigene family consisting of a cluster containing 16 paralogs. in the search for differentially regulated genes between e. ruminantium grown in endothelial and tick cell lines that could be used in vaccine development and to determine if differences in the map1 gene cluster exist between ...200515995193
genetic diversity of ehrlichia ruminantium in amblyomma variegatum ticks and small ruminants in the gambia determined by restriction fragment profile analysis.understanding genetic diversity of ehrlichia ruminantium in host and vector populations is an important prerequisite to controlling heartwater by vaccination in traditional livestock systems in sub-saharan africa. we carried out a study in two phases: (i) evaluating the usefulness of the pcr-rflp assay based on the map1 coding sequence of e. ruminantium as a discriminatory tool to characterise genetic diversity, (ii) applying the technique to field samples from amblyomma variegatum ticks and sma ...200817646061
a review of heartwater and the threat of introduction of cowdria ruminantium and amblyomma spp. ticks to the american mainland.heartwater, caused by the rickettsial agent cowdria ruminantium, is one of the most devastating livestock diseases in sub-saharan africa. in addition to domestic cattle, sheep, and goats, a variety of nondomestic species can acquire subclinical and clinical infections. recent epidemiologic findings that demonstrate a long-term host carrier state in domestic and wild ruminants, intrastadial transmission by the tick vectors (amblyomma spp.), vertical transmission of the agent from cows to their ca ...19989732023
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
some observations on the sero-prevalence of heartwater and tick infestation in zambian goats.a survey was carried out to define the distribution of heartwater in goats that originated from six districts in communal grazing semi-arid areas of zambia. a total of 181 samples (40.1%) out of 451 serum samples from adult goats were positive for ehrlichia ruminantium antibodies after screening using indirect map-1b antigen elisa technique with statistically significant differences (p < 0.01) between the six districts. out of 1 036 adult goats examined for tick infestation, 105 were infested by ...200415373339
detection by two enzyme-linked immunosorbent assays of antibodies to ehrlichia ruminantium in field sera collected from sheep and cattle in ghana.two serological tests for detection of antibodies to ehrlichia (previously cowdria) ruminantium, the causative agent of heartwater, were compared by using field sera collected from sheep and cattle as part of serosurveys in ghana. sera selected as either negative or positive by a new polyclonal competitive enzyme-linked immunosorbent assay (pc-elisa) were tested by the indirect map1-b elisa. cutoff values of 14 percent positivity (14 pp) for both ruminant species were obtained for the map1-b eli ...200312965927
transcriptional analysis of the major antigenic protein 1 multigene family of cowdria ruminantium.the major antigenic protein 1 (map1) of the tick-borne rickettsial pathogen cowdria ruminantium is encoded by a multigene family containing conserved and variable genes. the part of a locus containing the map1 multigene family that was characterized contained three homologous, but non-identical map1 genes, designated map1-2, map1-1, and map1. reverse transcriptase-polymerase chain reaction was used to study the transcriptional activity of these genes in isolates of c. ruminantium grown in bovine ...200212039046
[prevention of cowdriosis and cases of sheep diseases in the niayes region of senegal].sheep originating from an heartwater-free area were immunized by the infection and treatment method, using long-acting oxytetracycline. the animals were then exposed, together with control sheep to natural infection in an enzootic area. tick counts were made to monitor the infestation and establish a correlation between infestation by certain tick species, in particular amblyomma variegatum, and the occurrence of cowdriosis. in some cases of death associated with ehrlichiosis and anaplasmosis in ...19902218032
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 ...19957589273
seasonal epidemiology of ticks and aspects of cowdriosis in n'dama village cattle in the central guinea savannah of côte d'ivoire.in the central guinea savannah of côte d'ivoire, cattle breeding started only approximately 30 years ago. the impact of parasitism on the overall health status and productivity of the trypanotolerant n'dama cattle in this area is unknown. in close collaboration with national veterinary institutions and local farmers, we studied spectrum, burden and seasonal dynamics of ticks (including aspects of cowdriosis) on n'dama village cattle. in a longitudinal study, three randomly selected cattle herds ...200211821134
ehrlichia ruminantium in amblyomma variegatum and domestic ruminants in the caribbean.the highly sensitive nested pcs20 polymerase chain reaction assay for ehrlichia ruminantium was negative on 506 amblyomma variegatum from caribbean islands where clinical heartwater has not been reported, mainly the united states virgin islands (18), dominica (170), montserrat (5), nevis (34), st. kitts (262), and st. lucia (17). positive results were obtained with positive controls (crystal springs strain) and a. variegatum from countries in africa where infections are endemic, mainly tanzania ...201121485394
simultaneous detection of anaplasma and ehrlichia species in ruminants and detection of ehrlichia ruminantium in amblyomma variegatum ticks by reverse line blot hybridization.the detection of anaplasma and ehrlichia species is usually based on species-specific pcr assays, since no assay is yet available which can detect and identify these species simultaneously. to this end, we developed a reverse line blot (rlb) assay for simultaneous detection and identification of anaplasma and ehrlichia species in domestic ruminants and ticks. in a pcr the hypervariable v1 region of the 16s ribosomal rna (rrna) gene was amplified with a set of primers unique for members of the ge ...200212243899
immunogenicity of ehrlichia ruminantium grown in tick cell lines.ehrlichia (previously cowdria) ruminantium, the pathogen which causes heart-water in domestic and wild ruminants, can now be propagated in cell lines from one vector (amblyomma variegatum) and five non-vector (ixodes scapularis, i. ricinus, boophilus decoloratus, b. microplus and rhipicephalus appendiculatus) tick species. e. ruminantium isolates from west and south africa and the caribbean vary in their cell line preference, growth patterns and immunogenic capability. in laboratory trials, cert ...200214570129
ehrlichia ruminantium grows in cell lines from four ixodid tick genera.continuous cell lines from the ticks amblyomma variegatum, boophilus decoloratus, boophilus microplus, hyalomma anatolicum anatolicum, ixodes scapularis, ixodes ricinus and rhipicephalus appendiculatus were tested for ability to support growth of the rickettsial pathogen ehrlichia (previously cowdria) ruminantium. five e.ruminantium isolates, from west africa, south africa and the french west indies, were used. twelve tick cell lines were inoculated with e.ruminantium derived either from culture ...200415053931
differential transcription of the major antigenic protein 1 multigene family of ehrlichia ruminantium in amblyomma variegatum ticks.the rickettsial pathogen ehrlichia ruminantium causes heartwater in ruminants and is transmitted by ticks of the genus amblyomma. the map1 gene, encoding the major surface protein map1, is a member of a multigene family containing 16 paralogs. in order to investigate differential transcription of genes of the map1 multigene family in vivo in unfed and feeding ticks, rna was extracted from midguts and salivary glands of e. ruminantium-infected adult female amblyomma variegatum ticks and analysed ...200717321077
cowdriosis in senegal: some epidemiological aspects.the results of a study on the abundance of amblyomma variegatum in different ecological zones and of cowdria ruminantium infection rates in nymphal and adult ticks of the north guinean zones are given. joint research is also conducted on the evaluation of seroprevalence. in this study, it appears that the vector is most important in the north guinean zone, followed by the south sudan and the coastal niayes zones. elsewhere, the tick populations are not significant or absent. the infection rate i ...19938134635
ehrlichia ruminantium seroprevalence in domestic ruminants in ghana; i. longitudinal survey in the greater accra region.serum samples collected monthly over a 34-month period from cattle, sheep and goats in the greater accra region of ghana were tested for antibodies to ehrlichia (previously cowdria) ruminantium, the causative agent of heartwater, by polyclonal competitive elisa (pc-elisa). maternal antibodies, detected in about half of animals followed from under 1 month old, declined to negative levels within 2-4 months. amblyomma variegatum tick vectors were present on livestock in rural areas throughout the y ...200415145496
cowdria ruminantium: stability and preservation of the organism.blood collected in either sodium heparin or disodium edetate vacutainers from febrile goats infected with 4 isolates of cowdria ruminantium and cryopreserved with 10% dimethyl sulphoxide at -70 degrees c and -196 degrees c was an effective stabilate to initiate heartwater infections in goats. a homogenized pool of whole amblyomma variegatum ticks in snyder's buffer, maintained at -196 degrees c, was used to infect a goat with c. ruminantium. liver and spleen collected from swiss mice infected wi ...19873448560
seroconversion to cowdria ruminantium of malawi zebu calves, reared under different tick control strategies.the seroconversion by indirect elisa to cowdria ruminantium over the first year of life of sixty-six malawi zebu calves born into groups which were dipped 17 times per year was compared to seroconversion of 32 calves born into non-dipped groups. amblyomma variegatum tick counts and clinical disease in each group of cattle were monitored throughout the study period. no cases of heartwater were seen in either group of calves over the first 22 months of life. only one case of heartwater was observe ...19938134628
epidemiology of heartwater in guadeloupe and in the caribbean.at present, heartwater in the caribbean is known with certainty only on guadeloupe, marie galante and antigua; the first 2 islands are widely infected. the most important factors responsible for particular aspects of heartwater in guadeloupe are: cowdria ruminantium of high virulence. a very resistant cattle population (creole), not normally clinically affected. a fairly susceptible goat population (creole) (22% goats born in endemic areas die after experimental inoculation) which, fortunately, ...19873448572
the reservoir status of goats recovered from heartwater.experiments were conducted with creole goats and amblyomma variegatum ticks in guadeloupe to investigate whether it is possible to transmit cowdria ruminantium to susceptible hosts with nymphs fed in the larval stage on recovered goats. of 88 batches of larvae fed after the return of the goats' temperature to normal, or after challenge or immunosuppression, only the 9 batches of larvae fed during the febrile reaction, 2 batches applied 2 and 3 days respectively after recovery, and a single batch ...19873448574
new approaches to detection and identification of rickettsia africae and ehrlichia ruminantium in amblyomma variegatum (acari: ixodidae) ticks from the caribbean.imported from africa in the 1700s and despite frequent modern eradication efforts, amblyomma variegatum (f.) spread through the caribbean by cattle transport, small ruminants, and migrating birds. a. variegatum is a vector for rickettsia africae, the causative agent of african tick bite fever, and ehrlichia ruminantium, the causative agent of heartwater. we examined 95 a. variegatum and six rhipicephalus (boophilus) microplus (canestrini) collected from cattle at an abattoir in antigua. engorged ...200919645301
increasing risks of introduction of heartwater onto the american mainland associated with animal movements.opportunities to introduce heartwater onto the american mainland through animal movements include importation from africa of tick-infested reptiles and of subclinically infected wild ungulates and importation of livestock from islands in the caribbean infested with amblyomma variegatum ticks. measures to control importation of heartwater vectors on reptiles include importation bans of infested species, treatment of imported reptiles, and eradication of established infestations on the american ma ...200212381604
amblyomma variegatum in cattle in marie galante, french antilles: prevalence, control measures, and infection by ehrlichia ruminantium.we report marie galante as one of the caribbean islands most heavily infested by the tropical bont tick (tbt) amblyomma variegatum which is associated with two major diseases of ruminants: heartwater and dermatophilosis. in 2005, a survey was undertaken to assess the prevalence of tbt infestation in cattle, the prevalence of ehrlichia ruminantium infection in tbts, and the tick control measures implemented by livestock owners. a random sample of 195 cattle herds out of 1885 recorded on the islan ...200818406061
climate changes and suitability for the ticks amblyomma hebraeum and amblyomma variegatum (ixodidae) in zimbabwe (1974-1999).the spread of amblyomma hebraeum has been reported in zimbabwe. at the same time there was little or no spread in the distribution of amblyomma variegatum. this paper examines the climatic cycles and their trends in the period 1974-1999 with a view to explaining the abiotic causes of this spread, and of forecasting the likely tendency in climate suitability for both tick species. an annual data-set of rainfall and air temperature was used as a source for climate, together with a habitat-modeling ...200818083309
improved molecular detection of ehrlichia and anaplasma species applied to amblyomma ticks collected from cattle and sheep in ethiopia.detection of ehrlichia and anaplasma species in animals and tick vectors is crucial for an understanding of the epidemiology of diseases caused by these pathogens. in this study, a pair of primers designated ebr2 and ebr3 was designed from the anaplasma 16s rdna sequence and was used along with a previously described primer ehr 16sd for the simultaneous detection of ehrlichia and anaplasma species by nested pcr. the primers were used to amplify 925bp of dna from known species of ehrlichia and an ...201525438799
prevalence of ehrlichia ruminantium in adult amblyomma variegatum collected from cattle in cameroon.ehrlichia ruminantium, the etiologic agent of the economically important disease heartwater, is an obligate intracellular bacterium transmitted by ticks of the genus amblyomma, particularly a. hebraeum and a. variegatum. although serologic and microscopic evidence of the presence of heartwater have been reported in ruminants in cameroon, knowledge of e. ruminantium infection in the tick vector, a. variegatum, is lacking. in order to determine the infectivity of a. variegatum ticks by e. ruminant ...201322833099
identification and characterization of sialidase-like activity in the developmental stages of amblyomma variegatum.amblyomma variegatum f. are obligate hematophagous ectoparasites of livestock that serve as the vectors of ehrlichia ruminantium (formerly known as cowdria ruminantium), the causative agent of heartwater disease. in the light of the fact that they are blood-feeding, their salivary glands play prominent role in their acquisition of nutrients from the bloodmeal. sialic acids are a major component of glycoprotein in mammalian blood fluid and cells. sialome of hard ticks is still sparse. here, for t ...201323427656
amblyomma variegatum ticks and heartwater on three caribbean islands.amblyomma variegatum tick infestation, tick infection by ehrlichia ruminantium (er), and er genetic diversity were studied in the caribbean islands of guadeloupe, marie-galante, and antigua between 2003 and 2005. nested pcr for pcs20 was used to detect er, while er strains were characterized by sequencing or by restriction fragment length polymorphism (rflp) profiles of map-1 pcr products. in 2003 in guadeloupe, the prevalence of tick-infested herds was 35.6%. in marie-galante 79.1% of herds in ...200819120208
innovative approach for transcriptomic analysis of obligate intracellular pathogen: selective capture of transcribed sequences of ehrlichia ruminantium.whole genome transcriptomic analysis is a powerful approach to elucidate the molecular mechanisms controlling the pathogenesis of obligate intracellular bacteria. however, the major hurdle resides in the low quantity of prokaryotic mrnas extracted from host cells. our model ehrlichia ruminantium (er), the causative agent of heartwater, is transmitted by tick amblyomma variegatum. this bacterium affects wild and domestic ruminants and is present in sub-saharan africa and the caribbean islands. be ...200920034374
ehrlichia ruminantium infects rhipicephalus microplus in west africa.the invasion of west africa by rhipicephalus microplus during the past decade has changed the ecological situation of the agent of heartwater ehrlichia ruminantium in this area. before, its local vector, amblyomma variegatum, was the most abundant tick species found on livestock. today, the abundance of the r. microplus is one magnitude higher than that of a. variegatum in many west-african localities. we investigated the potential of this new ecological situation to impact the circulation of e. ...201627334439
molecular detection of ehrlichia ruminantium infection in amblyomma variegatum ticks in the gambia.in west africa, losses due to heartwater disease are not known because the incidence/prevalence has not been well studied or documented. to develop a diagnostic tool for molecular epidemiology, three pcr-based diagnostic assays, a nested pcs20 pcr, a nested map1 pcr and a nested reverse line blot (rlb) hybridization assay, were evaluated to determine their ability to detect infection in vector ticks, by applying them simultaneously to a. variegatum field ticks to detect ehrlichia ruminantium, th ...200717476576
Development of multiple-locus variable-number tandem-repeat analysis for rapid genotyping of Ehrlichia ruminantium and its application to infected Amblyomma variegatum collected in heartwater endemic areas in Uganda.SUMMARYThe rickettsial bacterium Ehrlichia ruminantium is the causative agent of heartwater, a serious tick-borne disease in ruminants. The genetic diversity of organisms in the field will have implications for cross-protective capacities of any vaccine developed, and for an effective vaccine design strategy proper genotyping and understanding of existing genetic diversity in the field is necessary. We searched for variable-number tandem-repeat (VNTR) loci for use in a multi-locus VNTR analysis ...201122008706
use of geographic information systems to identify areas at risk of introducing amblyomma variegatum and a. hebraeum to italy.tick-borne diseases are one of the most important obstacles to the development of livestock breeding in africa. among these diseases, heartwater is of significant importance, second in rank to east coast fever. heartwater affects wild and domestic ruminants and is caused by a micro-organism belonging to the order rickettsiales, previously called cowdria ruminantium and recently renamed ehrlichia ruminantium. the disease is transmitted solely by ticks. although the aetiology and the clinical sign ...200720422545
multi-locus sequence typing of ehrlichia ruminantium strains from geographically diverse origins and collected in amblyomma variegatum from uganda.abstract: background: the rickettsial bacterium ehrlichia ruminantium is the causative agent of heartwater in ruminants. a better understanding of the population genetics of its different strains is, however, needed for the development of novel diagnostic tools, therapeutics and prevention strategies. specifically, the development of effective vaccination policies relies on the proper genotyping and characterisation of field isolates. although multi-locus sequence typing (mlst) has been recently ...201121762509
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