Serological evidence for a hepatitis e virus-related agent in goats in the United States

Abstract

Hepatitis E virus (HEV) causes an important public health disease in many developing countries and is also endemic in some industrialized countries. In addition to humans, strains of HEV have been genetically identified from pig, chicken, rat, mongoose, deer, rabbit and fish. While the genotypes 1 and 2 HEV are restricted to humans, the genotypes 3 and 4 HEV are zoonotic and infect humans and other animal species. As a part of our ongoing efforts to search for potential animal reservoirs for HEV, we tested goats from Virginia for evidence of HEV infection and showed that 16% (13/80) of goat sera from Virginia herds were positive for IgG anti-HEV. Importantly, we demonstrated that neutralizing antibodies to HEV were present in selected IgG anti-HEV positive goat sera. Subsequently, in an attempt to genetically identify the HEV-related agent from goats, we conducted a prospective study in a closed goat herd with known anti-HEV seropositivity and monitored a total of 11 kids from the time of birth until 14 weeks of age for evidence of HEV infection. Seroconversion to IgG anti-HEV was detected in seven of the 11 kids, although repeated attempts to detect HEV RNA by a broad-spectrum nested RT-PCR from the faecal and serum samples of the goats that had seroconverted were unsuccessful. In addition, we also attempted to experimentally infect laboratory goats with three well-characterized mammalian strains of HEV but with no success. The results indicate that a HEV-related agent is circulating and maintained in the goat population in Virginia and that the goat HEV is likely genetically very divergent from the known HEV strains.

Keywords: animal reservoir; experimental infection; goat; hepatitis E virus; neutralizing antibodies; prospective study.

Figure 1

Seroconversion to IgG anti-HEV antibodies in goats from a prospective study in a closed herd in Virginia. The kids born to seronegative dams from a known seropositive goat herd were monitored for evidence of HEV infection for a total of 14 weeks from the time of birth. The weekly serum samples were tested by an ELISA for IgG anti-HEV. The ELISA OD values (Y-axis) are plotted along the X-axis which showed the ages of the animals (dates when the samples were collected). The ELISA cutoff value that is indicated with a dotted line was set as 3 standard deviations above the mean OD value of the day 0 serum samples.