Fatal human eosinophilic meningo-encephalitis caused by CNS co-infection with Halicephalobus gingivalis and West Nile virus

The first molecular isolation of Halicephalobus gingivalis from horses in Iran

BACKGROUND

Parasitic infections pose significant threats to humans' and animals' well-being worldwide. Among these parasites, Halicephalobus spp., a genus of nematodes, has gained attention due to its ability to cause severe infections in various animal species, including horses.

OBJECTIVE

This study aimed to determine the prevalence of Halicephalobus spp., specifically focusing on Halicephalobus gingivalis in horses.

MATERIALS AND METHODS

In July 2022, a cross-sectional study was conducted in northern Iran to determine the prevalence of Halicephalobus spp. Using standard coprological techniques, 141 fecal samples from randomly selected horses were analyzed for GI helminth eggs. The Halicephalobus spp. eggs present in faeces were identified by molecular methods. Polymerase Chain Reaction (PCR) was used to amplify the partial 5' variable region (~ 390 base pairs) of 18 S DNA using SSUA_F and SSU22_R primers. Furthermore, the PCR products obtained were sequenced, and phylogenetic analysis was performed using available sequences from GenBank.

RESULTS

Microscopic examination of 141 fresh faecal samples revealed 5 fecal samples were infected with small ellipsoidal nematode eggs ranging between 40 and 50 × 50-60 μm. This study's PCR amplicons showed ~ 390 bp bands on 2.0% agarose gel. A partial sequence of 18 S DNA (363 bp) was obtained herein (GenBank accession no. OQ843456).

CONCLUSION

Overall, using molecular tools represents a significant step forward in diagnosing and managing the Halicephalobus gingivalis infections in horses.

West Nile Virus: An Update on Pathobiology, Epidemiology, Diagnostics, Control and "One Health" Implications

West Nile virus (WNV) is an important zoonotic flavivirus responsible for mild fever to severe, lethal neuroinvasive disease in humans, horses, birds, and other wildlife species. Since its discovery, WNV has caused multiple human and animal disease outbreaks in all continents, except Antarctica. Infections are associated with economic losses, mainly due to the cost of treatment of infected patients, control programmes, and loss of animals and animal products. The pathogenesis of WNV has been extensively investigated in natural hosts as well as in several animal models, including rodents, lagomorphs, birds, and reptiles. However, most of the proposed pathogenesis hypotheses remain contentious, and much remains to be elucidated. At the same time, the unavailability of specific antiviral treatment or effective and safe vaccines contribute to the perpetuation of the disease and regular occurrence of outbreaks in both endemic and non-endemic areas. Moreover, globalisation and climate change are also important drivers of the emergence and re-emergence of the virus and disease. Here, we give an update of the pathobiology, epidemiology, diagnostics, control, and “One Health” implications of WNV infection and disease.

First description of a fatal equine infection with Halicephalobus gingivalis in Portugal. Relevance for public health

Halicephalobus gingivalis is a small saprophytic rhabditid nematode, represented only by females with a typical rhabditoid oesophagus and one egg in the uterus, capable of infecting vertebrates. This opportunistic parasite present 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 their eggs, leading to malacia and causing a sudden onset of neurological signs, such as anorexia, ataxia, urinary incontinence, blindness, decreased menace and tonal reflexes, tremors and aggressiveness. The disease is invariably fatal whenever brain lesions are present, and the diagnosis usually achieved only post‐mortem. The present work aims to describe the first case of infection by H. gingivalis ever reported in Portugal. An 8‐year old warmblood horse presented with an 8‐day history of progressive blindness involving the left eye, initially with normal pupillary reflexes, advancing to bilateral blindness and increasing deterioration in clinical condition. 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 corresponding to 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, and high numbers of inflammatory cells were found. The nematodes were identified as H. gingivalis. The clinical history, necropsy and histological findings presented constitute a typical case of H. gingivalis infection in a horse, never previously described in Portugal to the authors’ best knowledge. Humans can be infected by contact with contaminated manure, which makes this nematode a public health concern, especially for people living and/or working in close proximity to horses.

Isolation and molecular characterisation of Halicephalobus gingivalis in the brain of a horse in Piedmont, Italy

Background

A fatal case of meningoencephalitis was reported in a 13-year-old Koninklijk Warmbloed Paard Nederland stallion, suspected of West Nile virus (WNV) infection, in the Piedmont region of Italy. Clinical signs included right head tilt and circling, depression alternated with excitability, fever and lateral strabismus. Combined treatment consisting of dimethylsulfoxide, dexamethasone, sulphonamides and sedative was administered, but because of the poor conditions the horse was euthanatized and submitted for necropsy.

Results

At post-mortem examination no skin lesions were observed, all organs appeared normal on gross evaluation and only head and blood samples were further investigated. Neuropathological findings consisted of granulomatous meningoencephalitis and larvae and adult females of Halicephalobus gingivalis were isolated and identified from the digested brain. Frozen brain was submitted to PCR amplification and 220 bp multiple sequence alignment was analysed by Bayesian phylogenetic analysis.

Conclusions

Phylogenetic inference revealed that the isolate belongs to H. gingivalis Lineage 3. WN surveillance can help to deepen our knowledge of horse neurological disorders investigating their causes and incidence. Moreover, it can help to understand the geographic distribution of the H. gingivalis, to unravel epidemiological information, and to estimate risk for humans.

Helminths in organ transplantation

With transplantation becoming an increasingly routine form of treatment for diverse populations, and with international travel becoming ever more accessible and affordable, the danger of transplantation-mediated helminth infections, exacerbated by coincident immunosuppression, must be considered. In this Review, we attempt to catalogue all clinically-relevant helminthiases that have been reported to coincide with transplantation, whether by transplantation-mediated transmission, reactivation of latent infections in an immunosuppressed context, or possible de-novo infection during the immunosuppressed peritransplant period. Helminthiasis has been reported in cases of kidney, liver, bowel, pancreas, heart, lung, and stem-cell transplant, and blood transfusion. For each helminthiasis, known risk factors, symptoms, and suggested options for screening and treatment are given. We conclude that helminths are a small but important and potentially severe source of disease after transplantation, and, with options for diagnosis and treatment, these pathogens warrant greater consideration during organ implantation. The achievement of immunological tolerance using helminth-derived products is also an exciting future prospect.

First report of fatal systemic Halicephalobus gingivalis infection in two Lipizzaner horses from Romania: clinical, pathological, and molecular characterization

Halicephalobus gingivalis (H. gingivalis) causes a rare and fatal infection in horses and humans. Despite the zoonotic potential and severity of the disease, the epidemiology and pathogenesis of halicephalobiasis are still poorly understood. Several European cases of equine halicephalobiasis have been documented; however, in South-Eastern European countries, including Romania, equine neurohelminthiasis caused by H. gingivalis has not been previously described. Two Lipizzaner horses with a clinical history of progressive neurological signs were referred to the Pathology Department of the Cluj-Napoca (Romania) for necropsy. Both horses died with severe neurological signs. Gross examination and cytological, histological, and molecular analyses were performed. The stallions came from two different breeding farms. No history of traveling outside Romania was recorded. At necropsy, granulomatous and necrotizing lesions were observed in the kidneys, lymph nodes, brain, retroperitoneal adipose tissue, and lungs, indicating a systemic infection. Parasitological and histopathological analyses evidenced larval and adult forms of rhabditiform nematodes consistent with Halicephalobus species. Parasites were observed in both lymph and blood vessels of different organs and were also identified in urine samples. A subunit of the large-subunit ribosomal RNA gene (LSU rDNA) of H. gingivalis (673 bp) was amplified from lesions in both horses.To the authors' knowledge, this is the first report of equine systemic H. gingivalis infection in Romania and in South-Eastern Europe. Our findings provide new insights into the geographic distribution of specific genetic lineages of H. gingivalis, while also raising public health awareness, as the parasite is zoonotic.