Pathological Findings of Equine Infectious Anaemia in Horses at Polo Clubs in Kaduna, North West Nigeria

Equine infectious anaemia (EIA), caused by an equine lentivirus, is a reportable disease of equids that results in immune-mediated haemolytic anaemia, weight loss, and death in acute cases, with surviving horses becoming lifelong carriers. Horse racing and polo activities in Kaduna State, North West Nigeria, provide a setting where EIA transmission through contaminated equipment may occur. This study examined the haematological and histopathological features of EIA in horses at polo clubs in Kaduna, Nigeria, between March and October 2023. Eighteen horses with a history of recurrent febrile illness and haemolytic anaemia suspicious for EIA were enrolled. Blood samples were collected for haematological profiling and the agar gel immunodiffusion (Coggins) test. Necropsy was performed on six horses that died, and tissue samples from the spleen, liver, lymph nodes, kidney, and bone marrow were processed histologically. Coggins test confirmed EIA in 13 of 18 horses. Haematological findings included severe normocytic normochromic anaemia, thrombocytopaenia, and leucopaenia. Gross lesions included splenomegaly, hepatomegaly with icterus, and lymphadenomegaly. Histopathologically, haemosiderosis in the spleen and liver, glomerulonephritis, and lymphocytic portal hepatitis were dominant features. Bone marrow showed erythroid hyperplasia. These findings necessitate systematic Coggins testing of competition horses, strict equipment sanitation, and EIA control legislation enforcement. Keywords: equine infectious anaemia, EIA, horses, haematology, Kaduna