Hepatitis E virus (HEV) is an emerging zoonotic pathogen with worldwide distribution that has been detected in an increasing range of animal species in the last decade. The virus is shed primarily in the feces of infected species, which can lead to viral contamination of the environment. Samples from a wide variety of water sources have tested positive for HEV, and their high similarity to human and/or animal-derived HEV-3 strains has been confirmed. Notably, similar findings have also been detected in echinoderms and several bivalve shellfish species from coastal waters indicating HEV circulation in marine environments. However, information about the susceptibility of other marine species, such as cetaceans, to this emerging virus is still very limited.
A recent study by Dr. Javier Caballero-Gómez and colleagues investigated the prevalence of HEV in both free-ranging cetaceans and cetaceans under human care in Spain. They assessed the dynamics of seropositivity in longitudinally sampled individuals during the study period. Between 2011 and 2022, serum/plasma and/or liver samples from 304 cetaceans, including 240 free-ranging and 64 animals under human care, were collected along the Spanish coast and in six different zoological institutions in Spain. Thirty of the 64 cetaceans kept under human care were also surveyed longitudinally during the study period. Sixty-nine (50.7%; 95% confidence interval (95% CI): 42.3-59.1) of the 136 cetaceans tested by enzyme-linked immunosorbent assay (ELISA) showed anti-HEV antibodies. Seropositivity was detected in six of the nine species tested serologically, and exposure to HEV-3 was confirmed in four of the five ELISA-positive species that could be analyzed by western blot assay. Significantly higher seroprevalence was found in free-ranging (61.1%) animals than in those under human care (39.1%), which could be explained by differences in the diet or longer exposure to environmental contamination. In the free-ranging population, multivariate analyses identified “age” (adult) as a risk factor potentially associated with HEV exposure in cetaceans. Anti-HEV antibodies were also detected in four yearling free-ranging animals and seroconversions were found in two captive bottlenose dolphins (Tursiops truncatus). These findings denote HEV circulation in cetaceans during the study period although none (0.0%; 95% CI: 0.0-1.2) of the 302 cetaceans tested positive for active HEV infection by RT-PCR.
To the best of the authors’ knowledge, this is the first large-scale study to assess HEV circulation in cetaceans and the first report of exposure to the virus in Atlantic spotted dolphins (Stenella frontalis), common dolphins (Delphinus delphis), Risso’s dolphins (Grampus griseus), striped dolphins (Stenella coeruleoalba), as well as Cuvier’s beaked whales (Ziphius cavirostris) and killer whales (Orcinus orca). These results show high exposure to HEV in cetaceans in Spain, suggesting widespread circulation of this virus in the last decade in both free-ranging populations and those under human care. Further studies are required to assess the role of cetaceans in the epidemiology of the virus and to identify the sources of HEV transmission in these species.
Read the full article (Emerg Infect Dis. 2022 Dec;28(12):2543-2547): DOI: 10.3201/eid2812.221188
