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Animal viruses show evidence of HAV’s zoonotic origin
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A recent sampling and analysis of more than 200 species of small mammals has detected several animal viruses similar to hepatitis A, and provides new evidence suggesting a zoonotic origin to the human disease.
“The emergence of Ebola virus from bats and hantaviruses from rodents exemplifies the prominent contributions of these taxa to emerging zoonotic threats to human health, but the extent to which such species have contributed to the evolution of well-established human pathogens such as hepatitis A virus (HAV) is less clear,” Jan Felix Drexler, MD, virologist at the University of Bonn Medical Center, Germany, and colleagues wrote.
Figure 1. Researchers found evidence of hepatitis A-related viruses in dozens of different nonprimate hosts, including bats.
Source: Marco Tschapka/University of Ulm
“Unlike other human hepatitis viruses, HAV infections never persist and uniformly engender lifelong, likely antibody-mediated immunity against reinfection. HAV has thus disappeared previously from small, isolated human populations, raising questions as to how it could have evolved in early human hunter-gatherer societies.”
To examine the potential origin of HAV, Drexler and colleagues collected 15,987 samples of tissue, blood and feces from 209 small mammal species. Presence of hepatoviruses was confirmed by reverse transcriptase-PCR, and the genetic diversity and relation of these viruses to human HAV was explored using Bayesian phylogenetic reconstruction. In addition, the researchers compared 14 near-complete nonprimate genome sequences to that of human HAV, explored infection patterns among these creatures and examined potential antigenicity conservation between viruses using multispecies sera samples.
Among the specimens, 0.7% were positive for HAV-related viruses and originated from 28 different nonprimate hosts (13 bats, 13 rodents, one shrew and one hedgehog). Phylogenetic analysis demonstrated these viruses to be highly diversified, but genome analysis found conservation of several unique hepatovirus features. Antibodies collected from bats reacted to cells infected with HAV, and infection patterns among the small mammals reflected those previously observed among human outbreaks of HAV.
According to the researchers, these similarities provide evidence of an ancestral relationship between HAV and non-primate hepatoviruses.
“Zoonotic infections with emerging viruses have become increasingly relevant for human health due to the invasion of pristine habitats by humans and their livestock, advancing global mobility and the rapid spread of pathogens within dense human populations,” they wrote. “Our study exemplifies the utility of looking beyond phylogenetic criteria alone when conducting risk assessment for emerging RNA viruses and the need to include functional, ecologic and pathogenic analyses of animal reservoirs.” – by Dave Muoio
Disclosure: The researchers report no relevant financial disclosures.
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