Avian hepatitis E virus infection and possible associated clinical disease in broiler breeder flocks in Hungary

Abstract

In broiler breeder flocks in one broiler integration in Hungary, a new syndrome appeared in January 2005 with initially four successive post-peak flocks experiencing significant decreases in egg production. Clinically birds became depressed and there was a small increase in the mortality rate. Postmortem examinations revealed enlarged livers in up to 19% of birds dying, and enlarged spleens in some. Also observed were birds with either clotted blood or serosanguineous fluid in the abdomen and subcapsular haemorrhages of the liver. Histopathology and polymerase chain reaction excluded tumours and the presence of common tumour-associated viruses. Chronic bacterial infections (especially causing hepatitis, peritonitis and airsacculitis) were common but many enlarged livers had no obvious bacterial involvement. After a 9-month period during which a majority of flocks became affected, no newly affected flocks occurred. Investigations showed that all tested affected flocks were seropositive in the big liver and spleen (BLS) Agar Gel Immuno Diffusion (AGID) test. Subsequent flocks without post-peak egg-production drops were shown to be seronegative in the BLS AGID test, as were all the parent flocks contributing to the affected flocks. Liver samples and cloacal swabs were positive by polymerase chain reaction (aHEV helicase target), and calicivirus-like particles were demonstrated in bile samples from affected birds. These observations are similar to hepatitis-splenomegaly syndrome as described in North America and BLS syndrome as described in Australia. Histopathological features were a non-specific chronic hepatitis similar to those described in BLS and hepatitis-splenomegaly syndrome. Immunohistochemistry using a BLS-specific monoclonal antibody confirmed the presence of avian hepatitis E virus antigen in livers and spleen.

Sequence analysis and comparison of avian hepatitis E viruses from Australia and Europe indicate the existence of different genotypes

“…In Australia and Europe, clinically similar disease pictures and the presence of hepevirus have been reported (Handlinger & Williams, 1988;Massi et al, 2005;Morrow et al, 2008;Todd et al, 1993). However, at the molecular level, only a short sequence of the helicase domain in the ORF1 region created a link between possible aetiological agents of these two diseases (Haqshenas et al, 2001;Payne et al, 1999).…”

“…The virus material for sequencing isolate EaHEV (05-5492) was obtained from the liver of a bird displaying hepatomegaly, splenomegaly and severe abdominal bleeding (Morrow et al, 2008). The material for sequencing isolate AaHEV (06-561) was obtained from an FTA Classic Card with liver smears of birds experiencing symptoms of classical BLS, provided by P. Curtin (Goulburn, New South Wales, Australia) and A.…”

TaqMan Real-Time Reverse Transcription-PCR Assay for Universal Detection and Quantification of Avian Hepatitis E Virus from Clinical Samples in the Presence of a Heterologous Internal Control RNA

“…Most of the RT-PCR methods for detection of avian HEV RNA are based on degenerate primer binding within ORF1 (15) and on a nested approach applying degenerate primers binding within ORF1 and ORF2 (30). These primers were developed for isolates from North America but were also successfully used for RT-PCR detection of European and Australian avian HEV (2,21,22,25,28). Recent studies revealed that ORF3 is the most conserved region of avian HEV (2).…”

“…A high prevalence of antibodies was also detected in healthy chicken flocks and avian HEV was isolated from apparently healthy chicken flocks (30). In Europe, a wide distribution of avian HEV has been reported (2,21,22,25,28,32).…”

Avian hepatitis E virus identified in Russian chicken flocks exhibits high genetic divergence based on the ORF2 capsid gene

“…Later on, these two viral agents proved to be variants of the same virus (known as aHEV). aHEV has now been detected in countries such as Spain (Peralta et al, 2009), Hungary (Morrow et al, 2008) and Canada (Agunos et al, 2006). aHEV was previously recognized as a member of the genus Hepevirus within the family Hepeviridae, which also includes swine and human HEVs .…”