Molecular differentiation and pathogenicity of Aviadenoviruses isolated during an outbreak of inclusion body hepatitis in South Africa

Abstract

Fowl adenovirus (FAdV) is a member of the genus Aviadenovirus and causes a number of economically important poultry diseases. One of these diseases, inclusion body hepatitis (IBH), has a worldwide distribution and is characterised by acute mortality (5% - 20%) in production chickens. The disease was first described in the United States of America in 1963 and has also been reported in Canada, the United Kingdom, Australia, France and Ireland, but until now, not in South Africa. Adenoviruses isolated from the first outbreak of IBH in South Africa were able to reproduce the disease in chicken embryo livers. The aim of the present study was to characterise the viruses and determine the pathogenicity of the FAdV strains responsible for the first reported case of IBH in South Africa. Polymerase chain reaction (PCR) amplification of the L1 loop region of the fowl adenovirus hexon gene using degenerate primer pair hexon A/B was used to identify the viruses that were isolated. Restriction fragment length polymorphism (RFLP) of the amplification products was used for the differentiation of 14 isolates of fowl adenovirus. Sequencing of the PCR products followed by amino acid comparison and phylogenetic analysis using the L1 loop region of the hexon protein was done to determine the identity of the isolates. Amino acid sequences of the hexon genes of all the South African isolates were compared with those of reference strains representing FAdV species. Amino acid comparison of 12 South Africa field isolates to FAdV reference strains revealed a high sequence identity (> 93.33%) with reference strains T8-A and 764. Two of the isolates had high sequence identity (93.40%) with reference strains P7-A, C2B and SR48. Phylogenetic analysis of the L1 loop region of the hexon protein of all 14 South African isolates was consistent with their RFLP clusters. The mortality rates of embryos challenged with 106 egg infective doses (EID50) FAdV 2 were 80% - 87% and mortality rates for embryos challenged with 105.95 (EID50) FAdV 8b were 65% - 80%.

Isolation and molecular characterization of prevalent Fowl adenovirus strains in southwestern China during 2015–2016 for the development of a control strategy

“…Over the past 5 years, epidemics with mixed serotypes have been observed in different regions, such as FAdV-2, -11, -7 and -8 in Europe and North America, 7 , 35 , 36 , 37 FAdV-4 in Asia 5 , 38 , 39 , 40 , 41 and FAdV-2 and -8b in South Africa. 42 , 43 The most notable diseases associated with FAdV infection in chickens are IBH, HHS and GE. There were no reports of severe HHS prior 2014 in China.…”

Epidemiological and pathological investigation of fowl aviadenovirus serotypes 8b and 11 isolated from chickens with inclusion body hepatitis in Spain (2011–2013)

“…In recent years, IBH outbreaks caused by different FAdV serotypes have been described in Canada (Philippe et al, 2005;Ojkic et al, 2008a, b;Grgic et al, 2011;Dar et al, 2012), the USA (Wilson et al, 2010), the Republic of Korea (Choi et al, 2012), India (Thakor et al, 2012), South Africa (Joubert et al, 2014), Japan (Nakamura et al, 2011), China (Zhao et al, 2015), Australia (Steer et al, 2011) and in some European countries (Pizzuto et al, 2010;Zadravec et al, 2011Zadravec et al, , 2013Kajan et al, 2013;Schachner et al, 2016). Most of these outbreaks have been associated with genotypes FAdV-D, -E or -C, with serotypes 2, 4, 8b and 11 being the most frequently involved.…”

“…In recent years, IBH outbreaks have been detected in different countries; serotypes 2, 4, 8a, 8b and 11 have been the most frequent serotypes involved (Grgic et al, 2011;Nakamura et al, 2011;Steer et al, 2011;Choi et al, 2012;Dar et al, 2012;Kajan et al, 2013;Joubert et al, 2014;Zhao et al, 2015;Schachner et al, 2016).…”

An Inactivated Novel Genotype Fowl Adenovirus 4 Protects Chickens against the Hydropericardium Syndrome That Recently Emerged in China

“…The first FAdVs infection case was reported in Pakistan in 1987 [ 4 ], and subsequent outbreaks have been reported in Germany [ 5 , 6 ], Canada [ 7 ], Poland [ 8 ], Hungary [ 9 ], Chile [ 10 ], South America [ 11 ], Mexico [ 12 ], India [ 13 ], Korea [ 14 ], Japan [ 15 ], and China [ 16 ], resulting in significant economic losses to the poultry industry. Almost all the FAdVs could induce IBH with or without mortality, while fowl adenovirus serotype 4 (FAdV-4) plays a primary role in the aetiology of HPS with a mortality that ranges from 10 to 100 percent [ 12 , 16 ].…”