A Ifield report on IBH over 4 years
nclusion body hepatitis (IBH) is caused by the fowl adenovirus (FADV) which is made up of five genotypes or molecular groups A-E and twelve serotypes (17, 8a, 8b & 11). Adenoviruses are ubiquitous in nature with antibodies against them found in healthy and diseased chickens making it difficult to interpret serologic tests.
Antibodies develop one week post infection and reach peak levels after three weeks. The humoral immunity is persistent while the local immunity is short-lived.
The incubation period for IBH is short: 1-2 days. Sources of infection are mainly hen-to-egg (vertical) and oral-faecal (horizontal) with factors such as immunosuppression (infectious bursal disease, chicken anaemia virus, mycotoxins, etc.), immunologically naïve broiler breeder parents and high challenge on broiler
farm known to exacerbate the occurrence of IBH.
Some strains of adenoviruses infect and damage organs of the immune system such as the bursa, thymus and spleen resulting in immunosuppression. As there are many serotypes and antibodies are serotypespecific, it is practically not possible to vaccinate breeders against all known twelve serotypes.
Inclusion body hepatitis, IBH, was first described in the USA in 1963 by Helmbolt & Frazier, then in Canada, United Kingdom, Ireland, Australia, France and South Africa.
South African broiler cases that were reported in 2008 were most likely introduced through broiler breeders from the USA and Europe. These cases were associated with non-specific clinical signs such as depression, loss in body weight, watery droppings and weakness. Mortality was acute in 2-29 day old broilers ranged from 10-20%. On post-mortem, abnormalities were noticed in the liver, spleen, kidney and gizzard wall with histopathological changes mainly in the liver; also kidney and spleen. The causative serotypes of the fowl adenovirus (FADV) were found to be 2 and 8a in these 2008 cases.
In South Africa, IBH, is worth more attention as it may be considered an “emerging” disease since its first reporting in 2008, and then our first field experience in 2012.
Field Experience October 2012 to April 2016
Our field report is based on thirteen broiler flocks over about a fouryear period. Broilers at risk were approximately 380,000 spread in three South African provinces, namely Gauteng, Mpumalanga and the Western Cape. The incidence of IBH from October 2012 to April 2016 averaged 0.31% with no apparent seasonal effect.