2022-02-09
What's new with the virus?
Fowl adenovirus (FAdV) in poultry is an important etiologic agent of the disease known as
inclusion body hepatitis (IBH). The main virus is Adenovirus which is widespread in all avian
species and its antibodies can be found in healthy birds. The spread of this virus is very
wide, but most adenoviruses cause no or only mild disease; however, some are associated
with specific clinical conditions. A syndrome referred to as gizzard erosion (GE) and
hydropericardium syndrome (HPS) has also been associated with FAdV (mainly FAdV-1) in
some countries and in quail causing bronchitis disease in quail.
Based on virus neutralization assays, FAdV responsible for IBH has been classified into 12
serotypes (1-7, 8a, 8b, and 9-11). Based on molecular techniques, FAdVs have been
classified into 5 species (A–E) with varying degrees of cross-protection reported between
viruses belonging to different serotypes or genotypes. Recent analyzes of the entire
genome sequence of a large number of FAdVs have revealed recombination events
between FAdV strains, reflecting the complex cross-protective relationship between them.
Horizontal and vertical transmission plays an important role in IBH and HPS. Vertical
transmission has been described in the progeny (day old chick) of a breeder infected with
FAdV-4 and FAdV-8. Horizontal transmission has also been demonstrated; Young chicks that
come into contact with infected chicks may die from peracute IBH or HPS. Infection with
some types of FAdV can cause minimal liver disease; however, if the bird has been infected
with an immunosuppressive virus, clinical disease becomes apparent. Most out brakes
occur in broiler farms whose parent stocks have not been vaccinated against IBH.
What are the signs and symptoms of the disease?
Some clinical signs of IBH is sudden mortality usually seen in birds <6 weeks old and as
young as 4 days old. Mortality normally ranges between 2% and 40% where sudden
mortality per day could reach >1% and mordibity rate about 1 – 10%. The mortality rate
also varies depending on the pathogenicity of the virus as well as other co-agents such as
viruses or bacteria. Signs associated with diseases caused by other pathogens (eg: bacteria,
fungi, or viruses) commonly occur if birds are immunosuppressed condition. Flocks
affected with IBH often have abrupt onset of mortality, and individual chickens may show
nonspecific clinical signs such as lethargy huddling, ruffled feathers, and yellow, mucoid
droppings due to excess bile acids. Mortality usually lasts for 5 – 7 days.
Post mortem lesions in IBH, Haemorraghe muscle thigh and breast, the liver is often
swollen and enlarged and has yellowish discoloration and multiple pale and/or red
(hemorrhagic) foci. Sometimes found straw-colored transudate in the pericardial sac
(hydropericardium), lesions in the heart include myocardial edema and necrosis. Gizzard
errosion and swollen kidney with urates sometimes found.
Histopathologic lesions in the liver include acute hepatocytic degeneration, necrosis,
mononuclear cell infiltration and rare to widespread basophilic intranuclear inclusion
bodies.
Why IBH still breaks out?
In Indonesia, the many cases happens due to parents stock either did not vaccinated
parents or maternal antibody transmission is erratic because of improper vaccination
procedures that result in a substantial number of unvaccinated birds. When the parent
stock are properly vaccinated, the antibodies produced by the vaccine are transmitted to
their progeny, providing protection against field infections and clinical disease. In addition,
immunosuppressive diseases such as mycotoxicosis and infectious bursal disease (IBD) will
pave the way for FAdV to infect livestock.
How seriously does this disease affect the development of the poultry industry? (if you
can have some statistics of the impact on the country's total flock, that would be great).
The increase in mortality in broilers became a national issue that attracted quite a lot of
attention in 2018 and made many farmers suffer. Various agencies carry out investigations
of poultry diseases, one of which is carried out by PT Medion. These observations show
that in the period December 2017 – January 2019, 40 cases were found in 8 provinces in
Indonesia that tested positive for Fowl Adenovirus (FAdV), the causative agent of Inclusion
Body Hepatitis (IBH) (Wibowo MH et al. 2019). Until now, IBH cases still occur and raise the
awareness from breeders to commercial birds.
Based on the results of monitoring case analysis reports conducted by the Technical
Education and Consultation Medion team (2021), IBH disease is included in the top 5 cases
of viral disease in broilers in the January-June 2021 period. Cases increased in March and
decreased in June. Meanwhile, at the farm layer, IBH cases are very rare, but they are still
included in the top 10 rankings of viral diseases in the last 3 years so they still need to be
watched out for. The losses that are often experienced by farmers are as follows:
• Could attack at various ages of birds
• Direct damage to the liver system due to immunosuppressive effects
• Standard body weight is not achieved until the feed conversion ratio (FCR) increases
in broilers.
• Layer birds can also inhibit growth during grower and affect egg production during
layer period.
• In breeder It is a subclinical vertical virus transmission and causes low hatchability
as well
What are the solutions to prevent this disease?
Inactivated vaccines are used to control IBH in many countries, they use it for the parent
stock. Primary breeders with stringent biosecurity practices sometimes use inactivated
vaccines to ensure the transfer of maternal immunity from breeding flocks to their progeny.
The FAdV most frequently used to prepare commercial vaccines belong to serotypes 4, 8
and 11. In Indonesia an inactivated vaccines like Medivac IBH Emulsion are routinely used
to vaccinate breeders and broilers. The following is an example of an IBH vaccination
program using Medivac IBH Emulsion that can be used as a general guide for prevention
programs.
Other information.
Medion has succeeded in finding an effective way to prevent IBH
disease by vaccination using Medivac IBH Emulsion which contains 2
local Indonesian IBH viruses, namely FAdV serotypes 8b and 11 so
that they are homologous to the latest field isolates. In addition,
Medivac IBH Emulsion has also passed the safety and potency test so
that it is effectively used to prevent IBH. The first vaccination using
Medivac IBH Emulsion in breeders (parent stock) with revaccination,
was proven to be able to protect breeders during production and
optimize maternal antibodies to progeny. With the support of good
biosecurity and good farm management practice, Birds are safe from IBH attacks. Until July
2021, Medivac IBH Emulsion has been registered in 2 Asian countries such as Indonesia and
Cambodia.
Yonatan Dimascahyo Budianto, DVM, MSc, MM.
Technical Education and Consultation
Artha Vena International Pte. Ltd.
