Ehrlichia ruminantium variants which do not cause heartwater found in South Africa

Show simple item record Allsopp, M.T.E.P. Van Strijp, M.F. Faber, F.E. Josemans, A.I. Allsopp, Basil A. 2007-07-31T08:09:41Z 2007-07-31T08:09:41Z 2007-02
dc.description.abstract In 1994 a batch of apparently healthy goats was selected for intended export to the USA from a heartwater-free and vector tick-free region of South Africa. The animals were tested serologically for heartwater, using either or both an IFA and an ELISA test, and 52% were found to be serologically positive. A PCR assay based on Ehrlichia ruminantium 16S gene sequences gave positive results for 54% of the animals, suggesting that apparently non-pathogenic E. ruminantium variants existed in this heartwater-free area. To identify and characterise the agents responsible for the positive serological and PCR results, ticks and animal blood samples were collected from two of the three farms involved in the original survey during two successive seasons of expected peak tick activity. Ticks were kept alive for a minimum of 3 weeks to allow digestion of any blood meal before being processed. Over the two seasons, 28% of the livestock and 15% of the ticks sampled were found to be carrying E. ruminantium. E. ruminantium 16S and pCS20 sequences were detected in all of the four tick species collected from the livestock (Rhipicephalus evertsi evertsi, Rhipicephalus evertsi mimeticus, Hyalomma truncatum, Hyalomma marginatum rufipes), suggesting that some of the species may act as vectors. Animals generally carried multiple E. ruminantium 16S genotypes, whereas ticks rarely carried more than one. Infection levels in both animals and ticks were too low to generate a marked response when a blood stabilate was sub-passaged in a clean sheep, preventing the subsequent establishment of any of the organisms in culture. en
dc.description.sponsorship This research was funded by the Red Meat Research and Development Trust (RMRDT) of South Africa. We thank Prof. Ivan Horak for advice and critical reading of the manuscript. en
dc.format.extent 194946 bytes
dc.format.mimetype application/pdf
dc.identifier.citation Allsopp, MTEP, Van Strijp, MF, Faber, E, Josemans, AI & Allsopp, BA 2007, ‘Ehrlichia ruminantium variants which do not cause heartwater found in South Africa’, Veterinary Microbiology, vol. 120, no. 1-2, pp. 158-166 [] en
dc.identifier.issn 0378-1135
dc.identifier.other 10.1016/j.vetmic.2006.10.026
dc.publisher Elsevier en
dc.rights Elsevier en
dc.subject Ehrlichia ruminantium en
dc.subject Serology en
dc.subject Molecular diagnosis en
dc.subject ELISA en
dc.subject.lcsh Ehrlichiosis -- South Africa en
dc.subject.lcsh Rickettsial diseases en
dc.subject.lcsh Enzyme-linked immunosorbent assay en
dc.subject.lcsh Goats -- South Africa en
dc.title Ehrlichia ruminantium variants which do not cause heartwater found in South Africa en
dc.type Postprint Article en

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