Infectious bursal disease, or Gumboro, is the second most serious viral disease of poultry (after Newcastle disease) in Indonesia. Infection with the virus suppresses the animal's normal immune response, with the result that other infections can readily take hold. The economic impact of IBD in Indonesia has been worsened by the appearance in 1991 of very virulent strains of the virus (referred to as vvIBDV). These variants caused up to 30% mortality in broilers and 60% in layers. Surviving birds perform poorly because of severe immunosuppression by the virus.
Chicken meat is the main source of dietary protein in Indonesia. But since the economic crisis of 1997, there has been a decline in availability of poultry meat and eggs. The traditional backyard farming of kampung (native) chickens continues, with more households adopting ways of intensive growing in response to the high demand for kampung chicken meat.
Unfortunately, most smallholders and backyard chicken farmers do not vaccinate against vvIBDV in spite of frequent heavy losses, because of the vaccine price and the packaging sizes available. As well, many kampung chicken owners are not aware of the importance of the disease. Consequently, subclinical disease, causing poor growth and non-specific deaths, is often not recognised.
Australia is one of the few countries free of vvIBDV, but Indonesia is a potential source for its introduction. Earlier collaboration between Australian and Indonesian researchers led to an approach from Indonesia's BALITVET to ACIAR for help in developing a local vaccine. Locally produced vaccines would be cheaper, and packaging could be tailored for use by smallholders.
This project built on earlier work funded by AusAID, and carried out the research to develop and produce a local vaccine in Indonesia for the newly emerged very virulent infectious bursal disease (vvIBD).
Three IBDV clones were selected and tested in chickens in laboratory to make certain that they had characteristics of a safe and effective IBDV vaccine. The three selected clones were either intermediate or mild vaccine strains. Although laboratory testing of developed vaccines is necessary and useful, it is vaccine performance in the field that is the most relevant for measuring vaccine efficacy and safety. In Indonesia, infections caused by the virulent Newcastle Disease Virus (NDV) are common and chickens are often made more susceptible to Newcastle Disease if they are vaccinated with an IBDV vaccine that is not adequately attenuated.
The scientists compared the efficacy of three candidate vaccine clones in field trials, with the aim of choosing the most efficacious vaccine for commercialisation. Trials took place using both village and smallholder chickens, layers and meat-type chicks, as the two production systems differ vastly. For each type of chicken, flocks at three different locations were used - for example broiler flocks on farms located around Medan, Yogyakarta and Bogor - reflecting different maternal antibody status and husbandry conditions. Flock sizes varied between 1000 and 10,000 for broilers and layers, and between 1000 and 60 for village type chicks. All chicks were vaccinated via drinking water at either 8, 10 or 12 days of age, and village type chicks were revaccinated 28 days of age.
Two different commercial live IBD vaccines were used for comparison on two broiler farms and on one village chicken farm. In these instances broilers in one shed were vaccinated with a commercial vaccine and broilers in the other shed with either Ind4BV or Ind18BV. In all field trials, Ind4BV and Ind18BV vaccines were equally efficacious in all type of chickens.
All vaccinated flocks had good vaccination response, showed no mortality from Gumboro during the entire growing period, showed no signs of immunosuppression and growth performance at the end of growing period, as expected. Comparison of Ind4BV and Ind18BV with two commercial vaccines in broiler and village chickens indicated that both were as safe and as efficacious as the two commercial vaccines. Since in all field trials two of the vaccines performed well, they were consequently offered to local veterinary vaccine manufacturers for commercialisation in Indonesia. From three companies that expressed interest, two commercial partners were selected (Vaksindo and Caprifarmindo) and agreements made for transfer of vaccine seeds.
Links:
[1] http://www.aciar.gov.au/country/Indonesia
[2] http://www.aciar.gov.au/programarea/Animal Health