[Ticks and hemoparasitoses of livestock in Senegal. II. The Sahelian area]

ArticleinRevue d'élevage et de médecine vétérinaire des pays tropicaux 40(2):119-25 · February 1987with1 Reads
Source: PubMed
  • [Show abstract] [Hide abstract] ABSTRACT: Aspects of the spatial and temporal patterns of transmission of Crimean-Congo hemorrhagic fever (CCHF) virus were studied in Senegal, West Africa. A country-wide serological survey of domestic animals indicated that transmission was most intense in the northern dry sahelian zone and least in the southern, more humid guinean zone. Human IgG prevalence, ranging from nearly 20% to < 1% among 8 sites throughout the region, also was greatest in the north. A fatal human case of CCHF from Rosso, Mauritania in 1988 was studied and an accompanying serosurvey of human contacts and domestic animals indicated epidemic transmission during that period. Systematic samples of adult ixodid ticks on domestic animals allowed us to analyze the distribution and relative abundance of potential CCHF virus vectors, demonstrating that Hyalomma spp. predominated in those biotopes where transmission was most intense. A prospective study of CCHF virus infection and tick infestation in sheep exposed a period of epizootic transmission in 1988 that corresponded temporally with increased abundance of adult H. truncatum and H. impeltatum. Four strains of CCHF virus were isolated from pools of these ticks and of Rhipicephalus guilhoni. Our results suggest that CCHF virus is focally endemic throughout the region, although highly variable in time and space, and that the relative abundance of Hyalomma ticks may be the primary determinant of epidemic transmission.
    Full-text · Article · Jan 1990 · Veterinary Parasitology
  • [Show abstract] [Hide abstract] ABSTRACT: 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 and 0-60% of male ticks. Infection in the ticks did not influence their feeding success, as judged by weight at drop-off, and the weight of eggs produced by infected and non-infected ticks was similar. Transovarial transmission of CCHF virus was demonstrated in 2 of 12 (17%) egg batches from infected female ticks, but in none of 19 egg batches from ticks that tested negative for CCHF virus. Our results suggest that under certain ecological conditions, sheep may serve to amplify CCHF virus in nature through horizontal transmission and that the maintenance cycle also may be influenced by transovarial transmission to the next generation of ticks.
    Full-text · Article · Sep 1991
  • [Show abstract] [Hide abstract] ABSTRACT: Giemsa-stained thin blood smears prepared monthly from cattle, sheep and goats in the Greater Accra region of Ghana between May 1994 and December 1996 were examined for presence of tick-borne haemoparasites. The majority of animals were less than 2 months old at the start of the survey. Monthly and cumulative incidences are presented of Anaplasma sp., Babesia bigemina, Borrelia sp., Eperythrozoon sp., Theileria mutans and Theileria velifera in cattle, Anaplasma sp., Borrelia sp., and Theileria sp. in sheep, and Anaplasma sp. in goats. T. mutans was the commonest parasite in cattle, with 100% incidence in calves by 10 months of age, and Anaplasma was commonest in small ruminants. The relative prevalence of these haemoparasites in blood smears from cattle, sheep and goats sampled on a single occasion at sites in all 10 regions of Ghana was found to be similar, though actual infection rates were lower. Packed cell volume (PCV) measurements from the sampled animals are also presented; no seasonal trends were evident in the PCV of the cattle, sheep and goats sampled monthly. In animals sampled on a single occasion, mean PCV was significantly higher in cattle and sheep without detectable haemoparasite infection, and in cattle was lowest in animals positive for both Babesia and Anaplasma, while there was no difference in mean PCV levels between parasitised and non-parasitised goats.
    Full-text · Article · Oct 2004
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