Hepatitis E Virus Genotype 7 RNA and Antibody Kinetics in Naturally Infected Dromedary Calves, United Arab Emirates (original) (raw)

2020, Emerging Infectious Diseases

I nfection with hepatitis E viruses (HEVs) is one of the major causes of acute hepatitis in humans (1). Most HEV strains infecting humans belong to the virus species Orthohepevirus A (HEV-A) (2). HEV-A comprises 8 genotypes; genotypes 1-4 and 7 are found in humans. HEV-A genotypes 1 and 2 seem to be restricted to humans. The other 3 genotypes have also been detected in animals, including pigs (genotypes 3 and 4) and camelids (genotype 7) (1). The most likely source of human zoonotic HEV infection is consumption of contaminated food. Typically, human HEV infections lead to acute and self-limiting disease or asymptomatic seroconversion, but chronic hepatitis E has also been reported, mainly in transplant recipients (3,4). Infection with camel-associated HEV-A genotype 7 was reported in a patient from the United Arab Emirates with chronic hepatitis after liver transplantation (4,5). This infection was likely acquired through consumption of contaminated camel products. Despite the risk for zoonotic transmission, data about shedding and immunity of HEV-A genotype 7 infection in naturally infected dromedaries are scarce. The Study We investigated HEV-A RNA and specific antibody levels in dromedary calves and corresponding dams from 1 farm at monthly intervals over the course of the calves' first year of life. We included serum samples from 11 dam-calf pairs in the United Arab Emirates. The farm contained ≈4,500 camels. The 11 dam-calf pairs investigated in this study were kept in different fenced compartments within 100-150 m of each other but were housed together with other dam-calf pairs in the same paddock throughout lactation (6). All calves were born during June 2014. Serum samples were obtained during the first week and then at monthly intervals until 1 year after birth. We tested samples for HEV RNA by using 2 reverse transcription PCRs (RT-PCRs) and for HEV antibodies by an HEV-A genotype 7 IgG ELISA (Appendix, https://wwwnc.cdc.gov/EID/article/26/9/19-1758-App1.pdf). In the studied cohort, all calves were naturally infected by HEV-A, as confirmed by RNA detection in serum samples, or seroconversion. In 9 of the 11 calves (#1-#9) (Figure 1), HEV-A RNA was detected in >1 serum sample. In 2 calves (#10 and #11) no RNA was detected, but an increase in ELISA ratio, equivalent to seroconversion, confirmed recent HEV-A infection. The average age for infection of calves was 4.6 months (range 1-6 months). All HEV-A-RNA positive calves cleared the virus from their blood and showed accompanying seroconversion (Figure 1). Average viremia was 2.1 months (range 1-4 months). Viral RNA concentrations in serum samples ranged from 6.6 × 10 2 IU/mL to 2.3 × 10 6 IU/mL (mean 4.6 × 10 5 IU/mL).