Meningoencephalitis caused by Halicephalobus gingivalis in a thoroughbred gelding

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.

Evaluation of the Variability of the ORF34, ORF68, and MLST Genes in EHV-1 from South Korea

Equine herpesvirus-1 (EHV-1) is an important pathogen in horses. It affects horses worldwide and causes substantial economic losses. In this study, for the first time, we characterized EHV-1 isolates from South Korea at the molecular level. We then aimed to determine the genetic divergences of these isolates by comparing them to sequences in databases. In total, 338 horse samples were collected, and 12 EHV-1 were isolated. We performed ORF30, ORF33, ORF68, and ORF34 genetic analysis and carried out multi-locus sequence typing (MLST) of 12 isolated EHV-1. All isolated viruses were confirmed as non-neuropathogenic type, showing N752 of ORF30 and highly conserved ORF33 (99.7–100%). Isolates were unclassified using ORF68 analysis because of a 118 bp deletion in nucleotide sequence 701–818. Seven EHV-1 isolates (16Q4, 19R166-1, 19R166-6, 19/10/15-2, 19/10/15-4, 19/10/18-2, 19/10/22-1) belonged to group 1, clade 10, based on ORF34 and MLST analysis. The remaining 5 EHV-1 isolates (15Q25-1, 15D59, 16Q5, 16Q40, 18D99) belonged to group 7, clade 6, based on ORF34 and MLST analysis.

Equine Idiopathic Systemic Granulomatous Disease With Manifestation in the Cerebellum Associated With Equid Gammaherpesvirus 2

Idiopathic systemic granulomatous disease (ISGD), also known as equine sarcoidosis is an uncommon disease of horses, manifesting in exfoliative dermatitis and granulomatous inflammation in various organs. The current report presents a case of a 15-year-old Hanoverian mare with a 4-month history of weight loss, recurrent fever, skin lesions, and movement disorders. Pathological examination revealed granulomatous and necrotizing inflammation in the skin, regional lymph nodes, and cerebellum. Based on histological, immunohistochemical, and microbiological findings, the diagnosis of ISGD was made. Sequencing of the polymerase chain reaction product of pooled brain tissue revealed the presence of equid gammaherpesvirus 2 DNA. This case is the first description of generalized ISGD with granulomatous dermatitis simultaneously affecting the skin and cerebellum.

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.

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.

Fatal Halicephalobus gingivalis infection in horses from Central America

Halicephalobus gingivalis is a free-living nematode that causes an opportunistic infection in animals and humans. Two fatal cases of encephalitis and nephritis caused by H. gingivalis in equines from Costa Rica and Honduras are reported. Case 1: a 6-year-old Arabian stallion, from Costa Rica, presented severe neurological signs and was treated with systemic anti-inflammatory drugs and antibiotics. Because there was no improvement, it was euthanatized. Grossly, both kidneys showed large white nodules, ranging from 0.10 to 2.50cm. Histopathologically, both kidneys showed similar changes consisting of multiple necrotic foci with longitudinal and transversal sections of nematode larvae. In the brain, there were several foci with similar parasites, surrounded by lymphocytes and gitter cells. Case 2: an 8-year-old Spanish stallion from Honduras it was reported as depressed and would not eat or drink water. The animal was treated with antibiotics and analgesics, without response and died spontaneously three days after the onset of clinical signs. Only pieces of kidney were sent for histopathological examination and showed findings similar to those described in case 1. These findings are similar with cases already reported expanding the knowledge about the geographical distribution of H. gingivalis in horses.

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.

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

The saprophytic nematode Halicephalobus is a rare cause of fatal human meningo-encephalitis, and West Nile virus is neurotropic flavivirus implicated in a variety of clinical neurologic syndromes. Here we report a case of rapidly progressive CNS encephalopathy and death. Serologic, immuno-histochemical, histopathologic and nucleic acid studies demonstrate the presence of active Halicephalobus and West Nile virus in the CNS tissue. This is the first reported case of co-infection with these neurotropic pathogens.

First human case of fatal Halicephalobus gingivalis meningoencephalitis in Australia

Halicephalobus gingivalis (previously Micronema deletrix) is a free-living nematode known to cause opportunistic infections, mainly in horses. Human infections are very rare, but all cases described to date involved fatal meningoencephalitis. Here we report the first case of H. gingivalis infection in an Australian human patient, confirmed by nematode morphology and sequencing of ribosomal DNA. The implications of this case are discussed, particularly, the need to evaluate real-time PCR as a diagnostic tool.