Seroprevalence of Babesia caballi and Theileria equi in horses in Central Germany

Equine piroplasmosis is the most prevalent tick-borne disease found in Equidae, including horses, donkeys, mules and zebras, caused by the hemoprotozoan parasites Theileria equi (T. equi) or Babesia caballi (B. caballi). Both parasites are transmitted by ixodid ticks of the genera Rhipicephalus, Dermacenter, Hyalomma, Haemaphysalis and Boophilus. Since Equine piroplasmosis can occur in any region or environment where horses are exposed to vector ticks, horses in countries with a moderate climate may also be affected. Relocation of carrier horses and infected ticks by international transport is a potential way of spreading an infection. The clinical course of Equine piroplasmosis can be subclinical, acute, subacute or chronic. Both parasites are able to cause severe hemolytic anemia with fever, thrombocytopenia, lymphopenia, hyperbilirubinemia, hemoglobinuria, increased lactate dehydrogenase activity and acute renal failure. In case of intrauterine infection, abortion and neonatal death can occur. Infections with B. caballi are usually less severe than those with T. equi (which is also more frequently reported). After recovering from an acute episode, a horse remains a carrier of B. caballi for up to four years. In the case of a T. equi infection, the horse is a carrier for life. The aim of the study was to determine the seroprevalence of T. equi and B. caballi infections among horses in Central Germany, analyse potential risk factors for said infections, and compare the two methods of testing: indirect immunofluorescence antibody test: (IFAT) and competitive ELISA (cELISA). A total of 314 serum samples were collected from horses in Central Germany between May 2012 and November 2013. Blood smears from EDTA blood were prepared from each horse, stained with Diff-Quik and observed microscopically to determine the presence of intracellular parasites in erythrocytes. Two methods to detect antibodies against T. equi and B. caballi were used for analysis. The IFAT was conducted using the Testkits MegaScreen (R) Fluobabesia caballi ad us. vet. and MegaScreen (R) Fluotheileria equi ad us. vet. (Diagnostik Megacor, Horbranz, Austria) according to manufacturers instructions. The cELISA was conducted using the Babesia caballi antibody test kit, cELISA and the Babesia equi antibody test kit, cELISA (Veterinary Medical Research and Development (VMRD), Pullmann, Washington, USA) were used following the manufacturer s instructions. Information on gender, age, type of housing, usage, breed and clinical signs were recorded. Chi-Square test was used to compare the overall prevalence for each agent and positivity values regarding gender, age, type of housing, ability, clinical status, breed and time of blood collection. The Kappa-coefficient was used to compare the compliance of the two methods IFAT and cELISA. No intracellular parasites could be detected microscopically in the blood smears. Out of the 314 serum samples, 19 (6.1%) were found to be T. equi antibody positive, as tested by the IFAT, ranging from 1:80 up to 1:160. Ten (3.2%) out of these 19 sera were confirmed using the cELISA. According to the Kappa coefficient, a substantial agreement (0.68) between the two test systems was found with a concordance of 97%. Only one horse had antibodies against B. caballi, tested with the cELISA. The result could not be confirmed by the IFAT. No horse had antibodies against both, T. equi and B. caballi. Due to the small number of positive horses no significant risk factors could be identified. The horses tested positive for T. equi antibodies were equally distributed in the tested region of Central Germany. It can be concluded that antibodies against T. equi and in some rare cases against B. caballi can be found in serum of horses in Central Germany. Latent infected horses can be a source of infection for seronegative animals. Therefore, a continuous monitoring especially of horses being im- or exported is recommended.