RESUMEN
Aberrant nematode larval migration in the CNS of horses is rare but frequently fatal; one of the main etiological agents involved in this illness is Halicephalobus gingivalis. This soil nematode has been associated with several fatal equine meningoencephalitis reports worldwide; however, it had never been diagnosed in horses of Mexico. A 10 year-old Andalusian horse presented dysphagia, fever, weakness, prostration and ataxia; the patient expired during the medical attention. Post mortem examination was performed and no gross alterations were found. Histopathology revealed meningoencephalitis, vasculitis and intralesional adult nematodes, larvae and eggs compatible with Halicephalobus spp. A polymerase chain reaction (PCR) for the nuclear large subunit ribosomal RNA gene (LSU rDNA) of nematodes was performed from formalin-fixed and paraffin wax-embedded sections of brain. Posterior nucleotide sequence analysis of the amplified fragment identified the agent as H. gingivalis. To our knowledge, this is the first confirmed report of Halicephalobiasis in Mexico.