Setaria equina is a common parasitic infection in horses that is transmitted by mosquitoes. The absence of previous reports regarding the presence of Setaria equina microfilariae in Nigerian horses highlights the need to confirm its existence in the region. Verifying the existence of this parasite would enhance our overall understanding of its global distribution, which could then inform the development of more effective control measures. This paper reports a case of Setaria equina microfilariae infection in an adult Argentine polo pony mare in Nigeria. The recently acquired adult Argentine polo pony mare was exhibiting depression and weight loss. Despite normal vital parameters, the horse had a poor body condition and no history of deworming. Laboratory analyses, including wet blood film examination, complete blood count, and serum biochemistry, revealed the presence of Setaria equina microfilariae and macrocytic hypochromic anaemia. Treatment involved a five-day course of intramuscular multivitamin injections and three weeks of subcutaneous ivermectin injections. Follow-up examinations demonstrated the absence of microfilaria and a return to an active and lively state. The case report details the clinical presentation, diagnostic process, and successful treatment of a recently acquired adult Argentine polo pony mare. A consistent deworming regimen is essential for horses, including those recently acquired, to prevent parasitic infections and enhance their overall well-being.
