New insights in the diagnosis and treatment of equine piroplasmosis: Pitfalls, idiosyncrasies, and myths

Authors: MENDOZA, FRANCISCO - University Of Colorado; PÉREZ-ÉCIJA, ALEJANDRO - University Of Cordoba; Kappmeyer, Lowell; Suarez, Carlos; Bastos, Reginaldo

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2024
Publication Date: 8/14/2024
Citation: Mendoza, F.J., Pérez-Écija, A., Kappmeyer, L.S., Suarez, C.E., Bastos, R.G. 2024. New insights in the diagnosis and treatment of equine piroplasmosis: Pitfalls, idiosyncrasies, and myths. Frontiers in Veterinary Science. 11. https://doi.org/10.3389/fvets.2024.1459989.
DOI: https://doi.org/10.3389/fvets.2024.1459989

Interpretive Summary: Equine piroplasmosis (EP) is a tick-borne disease of equids caused by the parasites Theileria equi, Babesia caballi, and Theileria haneyi. Clinical signs of EP include fever, anemia, abortions, and high mortality in naive animals. EP is a reportable disease and represents an important barrier for the international movement of horses and other equids, disrupting equine sports worldwide. Control measures against EP include the use of anti-tick acaricides, serological and molecular diagnostic methods, and parasiticidal drugs, while vaccines remain unavailable. Use of acaricides is unsustainable, the available serological and molecular diagnostic methods lack standardization, sensitivity, and specificity, and the existing therapeutic drugs have side effects and are not effective in clearing the parasites. In this review, we propose the standardization and improvement of molecular and serological diagnostic methods for EP to make equid international movement safer, and the evaluation of novel drugs for the radical cure of the EP parasites. Also, we discuss idiosyncrasies, pitfalls and myths associated with the currently available EP diagnostic and treatment methods.

Technical Abstract: Equine piroplasmosis (EP) is a global tick-borne disease of equids caused by the intraerythrocytic apicomplexan parasites Theileria equi and Babesia caballi, and the more recently discovered Theileria haneyi. The parasites responsible for EP can be transmitted by several tick species, including Dermacentor, Hyalomma, and Rhipicephalus, but iatrogenic and vertical transmissions are also common. Clinical signs of EP include poor performance, fever, icterus, abortions, among others, and peracute or acute infections are associated with high mortality in non-endemic areas. EP is a reportable disease and represents an important barrier for the international trade of horses and other equids, causing disruption of international equine sports. Tick control measures, serological and molecular diagnostic methods, and the use of parasiticidal drugs are currently used against EP, while vaccines remain unavailable. Since most acaricides used in equids are non-environmentally friendly and linked to drug resistances, this is considered as an unsustainable approach. Imidocarb dipropionate (ID) and buparvaquone (BPQ) are currently the main drugs used to control the infection. However, while ID has several side and toxic effects and recurrent failures of treatment have been reported, BPQ is less effective in the clearance of T. equi infection and not available in some countries. Thus, novel alternative and effective therapeutics are needed. While current trade regulations require testing equids for EP before exportation, the lack of standardized PCR tests, and limitations of the currently recommended serological assays, entail a risk of inaccurate results. Hereby, we propose a combination of standardized PCR-based techniques and improved serological tests to diminish the risks of exporting EP-infected animals and to make equid international trade safer. In addition, this review discusses, based on scientific evidence, several idiosyncrasies, pitfalls and myths associated with EP, and identifies weaknesses of current methods of control and gaps of research, as initial steps towards developing novel strategies leading to control this disease.