Pathology in practice. Granulomatous nephritis, lymphadenitis, and encephalitis with intralesional adult and larval H gingivalis

Parasitic and zoonotic meningoencephalitis in humans and equids: Current knowledge and the role of Halicephalobus gingivalis

Halicephalobus gingivalis is a saprophytic nematode parasite that causes a rare form of fatal meningoencephalomyelitis in equids, humans, and ruminants. This nematode has neurotropic activity, but has also been found in the kidney, liver, lungs, optic nerves and even heart of its host. Despite the zoonotic potential and severity of the disease, the epidemiology, pathogenesis, life cycle, and risk factors are poorly understood. Cases have been reported from several countries in Europe countries and North America but none is recorded in Africa except Egypt. This review looks at the historical overview, morphology, diagnosis, treatment and summary of reported cases in humans and equids. We recommend the parasitic helminthic infection in the differential list of meningoencephalitis involving humans and animals worldwide despite its rareness.

An outbreak of bovine meningoencephalomyelitis with identification of Halicephalobus gingivalis

Halicephalobus gingivalis is an opportunistic parasite which is known to cause fatal meningoencephalomyelitis primarily in equines but sporadically also in humans. In April 2014, laboratory examination of the head of a young dairy calf, euthanized due to severe central nervous system symptoms, revealed the presence of granulomatous to necrotizing encephalitis and myriads of nematodes in the brain lesion. Morphologically the parasites were identified as H. gingivalis. The diagnosis was confirmed by molecular analysis of the large subunit (LSU) rRNA and the small subunit (SSU) rRNA genes, revealing genetic variations of 0.5-4.4% and 0.7-8.6%, respectively, between the H. gingivalis isolated from the Danish calf and published isolates, collected worldwide from free-living and parasitic stages of the nematode. Clinical symptoms and histological changes indicated infection with H. gingivalis from another three calves in the herd. This is the first scientific publication of H. gingivalis induced meningoencephalomyelitis in ruminants. As ante mortem diagnosis is a major challenge, the infection may easily remain undiagnosed in cattle.