Infectious Disease · Medical Literature
Human gnathostomiasis - A systematic review and analysis of the literature.
Abstract
Human gnathostomiasis is a foodborne zoonotic nematode infection caused by the larval stage of Gnathostoma species. Although historically reported predominantly from Asia and America, cases are increasingly identified in previously non-endemic regions. The heterogeneous clinical presentation and diagnostic challenges likely contribute to underrecognition of the global disease burden. Current evidence is largely derived from case reports and case series, with a notable lack of prospective studies. To better delineate the epidemiological distribution and clinical characteristics of human gnathostomiasis, we systematically reviewed and analyzed the available literature. Most cases are reported from Asia and the Americas, with Thailand, Japan, and Mexico accounting for the highest numbers. Clinical manifestations are predominantly larva migrans syndromes, including cutaneous involvement (83.6% of cases), followed by neurological (7.7%), ocular (3.5%), and visceral (2.3%) presentations. Long-term sequelae are uncommon overall but occur frequently in ocular (51.8%) and neurological (32.2%) disease, the latter also being associated with a substantial case-fatality rate (33.9%). Diagnosis is based on exposure risk, most commonly consumption of raw fish (70.7%), as well as laboratory findings such as eosinophilia, positive serology, and, when feasible, histopathological confirmation. Treatment primarily relies on anthelmintic treatment with albendazole and/or ivermectin and, if feasible, surgical removal of larvae. Treatment success is highest with albendazole plus ivermectin combination therapy (86.7%) compared to monotherapy with albendazole (73.5%) or ivermectin (56.7%).
Clinical relevance
Human gnathostomiasis is an emerging foodborne zoonotic nematode infection of growing global relevance, as cases are increasingly identified outside historically endemic regions of Asia and Latin America, raising the risk of underdiagnosis in non-endemic settings. The heterogeneous larva migrans presentations — spanning cutaneous, neurological, ocular, and visceral syndromes — alongside diagnostic challenges (reliance on exposure history, eosinophilia, serology, and histopathology) contribute to a likely underestimated global burden. Clinicians in non-endemic regions must maintain a high index of suspicion in patients with compatible exposure history (e.g., raw fish consumption) and eosinophilic syndromes, as delayed diagnosis of neurological and ocular forms carries significant morbidity and mortality.
Key findings
1. Geographic distribution: The majority of reported cases originate from Asia and the Americas, with Thailand, Japan, and Mexico accounting for the highest case numbers; however, cases are increasingly identified in previously non-endemic regions, signaling global spread. 2. Clinical manifestations: Cutaneous larva migrans is the predominant presentation, accounting for 83.6% of cases, followed by neurological (7.7%), ocular (3.5%), and visceral (2.3%) forms. 3. Long-term sequelae and mortality: Long-term sequelae are uncommon overall but occur at high frequency in ocular (51.8%) and neurological (32.2%) disease; neurological gnathostomiasis carries a substantial case-fatality rate of 33.9%. 4. Primary exposure risk: Raw fish consumption is the most commonly identified exposure, reported in 70.7% of cases, with eosinophilia, positive serology, and histopathological larval identification serving as key diagnostic adjuncts. 5. Treatment efficacy — combination vs. monotherapy: Combination anthelmintic therapy with albendazole plus ivermectin achieves the highest treatment success rate at 86.7%, compared to albendazole monotherapy (73.5%) and ivermectin monotherapy (56.7%). 6. Evidence quality limitation: Current evidence is predominantly derived from case reports and case series, with a notable absence of prospective controlled studies, limiting the strength of epidemiological and therapeutic conclusions.
Practice implications
In patients presenting with migratory cutaneous swellings, eosinophilic meningitis, or unexplained ocular inflammation in the context of raw or undercooked fish/reptile/poultry consumption — particularly with travel to or from Thailand, Japan, or Mexico — gnathostomiasis should be included in the differential diagnosis, with workup including eosinophil count, Gnathostoma-specific serology, and CSF analysis where neurological involvement is suspected. Given the superior efficacy of combination therapy (86.7% success rate), albendazole plus ivermectin should be the preferred anthelmintic regimen over either agent alone, with surgical larval extraction pursued when the larva is accessible. Patients diagnosed with ocular or neurological gnathostomiasis require close long-term follow-up given the high rates of permanent sequelae (51.8% and 32.2%, respectively) and the substantial case-fatality rate (33.9%) associated with neurological disease.