First case report of Equine Protozoal Myeloencephalitis in Argentina

MORÉ, G.; MONINA M.; IDIART J.; GIROTTI G.; VENTURINI L.; VENTURINI M.C.

Buenos Aires

Congreso; The 23rd International Conference of the World Association for the Advancement of Veterinary Parasitology (WAAVP 2011); 2011

Equine protozoal myeloencephalitis (EPM) is frequently caused by Sarcocystis neurona and generates significant economic losses in American horses. In Argentina antibodies to this protozoan have been detected but no clinical cases have been reported. EPM is characterized by neurological signs corresponding with multifocal lesions of the central nervous system (CNS). Serological tests, histopathology, immunohistochemistry (IHC) and polymerase chain reaction (PCR) are recommended methods for specific diagnosis.A 12-year-old, mix breed, female horse, from a farm in Buenos Aires Province was received with asynchronous walking and bilateral stringhalt. The mare was treated with phenytoin, B1 vitamin, NSAIDs and subsequent tenectomy, without positive results. The clinical course was progressive with depression, involvement of cranial nerves V and VII, atrophy of the muscles of the back, loin and pelvic limbs, dysmetria and gait instability, generalized tremors, poor response to stimuli, severe dragging of hooves and tetraparesis. Considering the prostration, the horse was euthanized and necropsied. At necropsy no gross lesions were observed in the CNS. Microscopically, lesions were observed mainly in thalamus, brainstem and spinal cord, and consisted in small hemorrhagic multiple foci and small foci of chronic inflammation conformed by histiocytes, multinucleated cells and occasional foam cells. Neuronal necrosis was also observed together with sateliosis, perivascular mononuclear infiltrates, and endothelial swelling in the spinal cord and scattered areas of axonal degeneration. The IHC revealed the presence of intracellular S. neurona meronts and free merozoites in brain and spinal cord samples. By PCR-RFLP using the primers JNB33-JNB54 digested with HinfI and DraI, and primers JNB25-JD396 digested with HinfI and HindIII, a specific restriction pattern of S. neurona was observed in brain samples.This is the first case report of EPM in Argentina, confirmed by histopathologic, immunohistochemical and molecular studies. The previous detection of antibodies to S. neurona in horses, the abundance of opossums (Didelphis albiventris) in our environment and the specific confirmation in this case, suggest that the disease may be widespread in Argentina. It is necessary to establish an EPM surveillance program in order to evaluate the importance of this disease in Argentina, as well as to establish control strategies.