Subclinical circulation of avian hepatitis E virus within a multiple-age rearing and broiler breeder farm indicates persistence and vertical transmission of the virus

Abstract

In a prospective longitudinal study, a broiler breeder flock and its progeny were monitored for the presence of avian hepatitis E virus (HEV) RNA and antibodies. The flock was part of a multiple-age farm where the presence of avian HEV with clinical signs (increased mortality and decreased egg production) was demonstrated in several previous production cycles. Samples were taken twice at the rearing site and several times at the production site from broiler breeders including cockerels and day-old chicks. The samples were investigated by conventional and real-time reverse transcriptase-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA) and histological methods. At all time points, samples from the hens were positive for avian HEV RNA. The birds did not show any clinical signs, even though histopathological lesions of non-specific aetiology in the liver and spleen could be demonstrated. A significant increase in the number of positive birds and viral load was seen in week 45, in accordance with an increase in antibody titres. In comparison, cockerels investigated in week 62 tested negative by RT-PCR and ELISA. Avian HEV RNA was also detected in day-old chicks hatched from eggs laid in week 25, indicating vertical transmission. All partial helicase and capsid sequences retrieved within this study clustered together and were identical to previous sequences obtained from the same multiple-age farm. In conclusion, avian HEV persisted on the farm over years and circulated between the rearing and the production sites without causing any clinical signs although high viral loads in the adult hens were observed.

Effect of housing arrangement on fecal-oral transmission of avian hepatitis E virus in chicken flocks

“…The virus can also cause mild clinical disease in chicken flocks, characterized by a decrease in egg production when the external environment is altered (such as with changes in climate and feed) and/or if infection occurs concurrently with other pathogen infections [ 5 ]. Although vertical transmission of the virus has been reported recently [ 6 ], avian HEV is believed to be transmitted mainly by the fecal-oral route in flocks [ 1 , 7 , 8 ]. To date the virus has been reported to be present in many countries [ 1 , 2 , 8 – 13 ].…”

Development and evaluation of a SYBR Green real-time RT-PCR assay for detection of avian hepatitis E virus

“…Avian hepatitis E virus (HEV) is the main causative agent of big liver and spleen disease, as well as hepatitis-splenomegaly syndrome in chickens [ 1 – 3 ]. Both of these diseases result in a decrease in egg production, an increase in mortality, and an enlargement of liver and spleen in broiler breeders and egg laying hens [ 4 – 7 ]. In addition, the antibodies and viral RNA of avian HEV were universally detected in healthy chicken flocks, indicating that the virus can cause subclinical infections in chickens [ 8 – 11 ].…”

C-Terminal Amino Acids 471-507 of Avian Hepatitis E Virus Capsid Protein Are Crucial for Binding to Avian and Human Cells

“…Almost in parallel, hepatitis–splenomegaly syndrome was described in the United States as a disease that causes slightly increased mortality and decreased egg production in broiler breeders and laying hens [ 2 , 3 ]. Transmission of the virus occurs through the fecal-oral route but vertical transmission has been suggested as well [ 4 ]. The presence of avian HEV has been widely detected around the world like in China [ 5 ], Australia [ 6 ], Korea [ 7 ], United States [ 8 ] and Europe [ 6 , 9 , 10 ].…”