Horses in South Africa found to infested with 17 tick species

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The most common tick identified on horses in a South Africa-wide study is a species that can spread the organisms responsible for equine piroplasmosis, researchers report.

The study team set out to learn more about the species of hard-bodied (ixodid) ticks that infest horses and donkeys across the country and to identify those species that act as vectors of disease to domestic livestock.

Ticks were collected opportunistically from 391 horses countrywide by their owners or grooms, or by veterinary students and staff at the Faculty of Veterinary Science from the University of Pretoria.

Ticks were also collected from 76 donkeys in Limpopo Province, 2 in Gauteng Province and 1 in North West province.

A total of 5327 adult and immature ticks were collected from horses and a total of 487 from donkeys.

All the ticks were identified by means of a stereoscopic microscope.

Ivan Horak and his colleagues, writing in the Onderstepoort Journal of Veterinary Research, reported that horses were found to be infested with 17 tick species.

The most common was Rhipicephalus evertsi evertsi, which were found on 72.1% of the tick-infested horses, followed by Amblyomma hebraeum, found on 19.4% of the horses, and Rhipicephalus decoloratus, on 15.6% of the horses..

R. evertsi evertsi was recovered from horses in all nine provinces of South Africa and R. decoloratus in eight provinces.

The prevalence of R. evertsi evertsi was potentially important because it is the vector of the organisms that cause equine piroplasmosis, Babesia caballi and Theileria equi, the researchers said. It also transmits Anaplasma marginale, the organism the causes anaplasmosis in cattle.

Infestations with immature ticks of R. evertsi evertsi may be considerable in horses, they noted, but burdens of adult ticks were seldom large.

Various other tick species collected from the horses were important vectors of diseases in domestic cattle, they noted. A. hebraeum is the vector of Ehrlichia ruminantium, the organism that causes heartwater in cattle, sheep and goats, whereas R. decoloratus transmits Babesia bigemina, which causes babesiosis in cattle.

Donkeys were infested with eight tick species: 81.6% were infested with R. evertsi evertsi, 23.7% with A. hebraeum and 10.5% with R. decoloratus.

Horak was joined in the research by Heloise Heyne, Ali Halajian, Shalaine Booysen and Willem Smit. They are variously affiliated with the University of Pretoria, the University of Limpopo, and the Agricultural Research Council-Onderstepoort Veterinary Institute.

Horak, I.G., Heyne, H., Halajian, A., Booysen, S. & Smit, W.J., 2017, ‘Parasites of domestic and wild animals in South Africa. L. Ixodid ticks infesting horses and donkeys’, Onderstepoort Journal of Veterinary Research 84(1), a1302. https://doi.org/10.4102/ojvr.v84i1.1302

The study, published under a Creative Commons License, can be read here

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