First case of fatal equine meningoencephalitis caused by Halicephalobus gingivalis in Mexico

Area of Science:

• Veterinary Neurology
• Parasitology
• Equine Pathology

Background:

• Aberrant larval migration of nematodes in the central nervous system (CNS) of horses is a rare but often fatal condition.
• Halicephalobus gingivalis, a soil-dwelling nematode, is a significant etiological agent implicated in fatal equine meningoencephalitis cases globally.
• Prior to this report, Halicephalobiasis had not been documented in equine populations in Mexico.

Observation:

• A 10-year-old Andalusian horse presented with clinical signs including dysphagia, fever, weakness, prostration, and ataxia.
• The horse unfortunately expired during veterinary intervention.
• Post-mortem examination revealed no gross pathological alterations.

Findings:

• Histopathological analysis of the equine brain demonstrated severe meningoencephalitis, vasculitis, and the presence of adult nematodes, larvae, and eggs consistent with Halicephalobus spp.
• Polymerase chain reaction (PCR) targeting the nuclear large subunit ribosomal RNA gene (LSU rDNA) was performed on formalin-fixed, paraffin-embedded brain sections.
• Nucleotide sequence analysis confirmed the etiological agent as Halicephalobus gingivalis.

Implications:

• This case represents the first confirmed diagnosis of Halicephalobiasis in Mexico.
• The findings expand the known geographic distribution of Halicephalobus gingivalis.
• This diagnosis underscores the importance of considering Halicephalobus gingivalis in the differential diagnosis of equine neurological diseases, even in previously unaffected regions.