First description of a fatal equine infection with Halicephalobus gingivalis in Portugal : relevance for public health

Research Areas: Veterinary SciencesABSTRACT - Halicephalobus gingivalisis a small saprophytic rhabditid nematode, represented only by females with a typicalrhabditoid oesophagus and one egg in the uterus, capable of infecting vertebrates. This opportunistic parasitepresent in the soil, manure and decaying humus, is thought to penetrate through previous injuries to the mouth,eyes and skin of horses and migrate to various organs. The brain is one such organ, where the females lay theireggs, leading to malacia and causing a sudden onset of neurological signs, such as anorexia, ataxia, urinaryincontinence, blindness, decreased menace and tonal reflexes, tremors and aggressiveness. The disease isinvariably fatal whenever brain lesions are present, and the diagnosis usually achieved only post-mortem. Thepresent work aims to describe the first case of infection byH. gingivalisever reported in Portugal. An 8-yearold warmblood horse presented with an 8-day history of progressive blindness involving the left eye, initiallywith normal pupillary reflexes, advancing to bilateral blindness and increasing deterioration in clinical condi-tion. After euthanasia, the animal was submitted for necropsy. Organ samples were collected and fixed in 10%neutral buffered formalin for routine histopathology. A large mass was found in the left kidney correspondingto fibrous tissue heavily infiltrated with inflammatory cells and numerous nematodes. In the brain, multiple,bilateral and asymmetrical foci of malacia containing several rhabditoid nematodes, larvae and zygotes, andhigh numbers of inflammatory cells were found. The nematodes were identified asH. gingivalis.The clinicalhistory, necropsy and histological findings presented constitute a typical case ofH. gingivalisinfection in ahorse, never previously described in Portugal to the authors’ best knowledge. Humans can be infected bycontact with contaminated manure, which makes this nematode a public health concern, especially for peopleliving and/or working in close proximity to horses.