While some poultry farmers may be feeling anxious about the infectious bursal disease (IBD), also known as gumboro, veterinarians warn that the deadly chicken killer can be managed. Like many other diseases, gumboro is usually rampant in the wet, rainy or cold seasons.
Biosecurity management
Speaking to Food For Mzansi, Rainbow Chicken veterinary executive Andrew van Wijk said small-scale farmers can easily implement prevention methods on their farms. The most important part is to practice good biosecurity management and it starts with buying day-old chicks.
Van Wijk said: “Buying good quality day-old chicks that come from a supplier who vaccinates their breeder birds properly against IBD is important.
“This is because broilers are partially dependent on IBD antibodies from the hens, especially in the early stages of their life. These are called maternally derived antibodies (MDA).”
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Tips to prevent spreading?
In case of an IBD outbreak, spreading to other houses or farms should be prioritised through good biosecurity measures. Van Wijk listed the following:
- Shower facilities.
- Protective clothing and separation between clean and dirty areas.
- Gumboot disinfectants are used between houses through a disinfectant water bath.
- Enough open time between flocks – aim for at least 10 days from the last bird caught till placing the chicks of the next flock.
- Proper washing and disinfecting of the site and surroundings, IBD is a very resistant virus. Disinfectants include glutaraldehyde, formalin, and QAC.
- IBD is immunosuppressive, so you should apply good farming principles and stockmanship to alleviate stress on the birds.
- Apply rodent control.
- Limit visitors and keep a record of their movements.
“Maintain high standards of hygiene, particularly with regard to disinfection between batches. Store poultry manure for at least three months before spreading. Do not spread manure on land used for poultry, and protect manure heaps from wildlife,” she advised.
Important note on vaccinations
According to Dr Prisciilla Muradas, the founder of Douglas Veterinary Clinic and Vetshop in the Northern Cape, it is important for farmers to have a vaccination programme. If there are cases of gumboro, it is important that farmers vaccinate all birds at a week old and operate an “all-in, all-out” policy between batches of birds.
The main goal of any IBD vaccination programme is to use vaccines that most closely match the antigenic profile of the field viruses.
High levels of maternal antibody during early brooding of chicks can minimise early infection, subsequent immunosuppression, or both, she explained.
“Live vaccines are typically administered via drinking water. Vector vaccines can be used in-ovo or subcutaneously at hatch. Longer-lived birds should be vaccinated one or more times during the growing period, first with a live vaccine and again just before egg production with an inactivated vaccine,” Muradas said.
Timing is crucial
Broilers are vaccinated with live vaccines on the farm through drinking water. The age of this vaccination is dependent on the number of antibodies the chicks received from the hens.
A higher number of antibodies received via the yolk will protect the chick for longer against the disease, while chicks with lower MDA levels will have to be vaccinated sooner.
An important note is that vaccinating your chicks too soon could result in the MDA breaking down the vaccine (virus).
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Different types of vaccines
According to Muradas, there are different gumboro disease virus strains used in the vaccines and there are different levels of attenuation.
“Vaccine types are categorised into four groups: ‘Mild’ which is highly attenuated, ‘Intermediate’ which is very attenuated, ‘Intermediate Plus’ which is moderately attenuated, and ‘Hot’ which is poorly attenuated,” Muradas explained.
Vaccine immunity induced by the administration of a vaccine will develop according to the vaccine(s) employed, the quality of the application, and the immune status of the chickens at the time of the vaccination, she added.
New types of vaccines include immune complex (antigen-antibody complex) vaccines as well as vector vaccines, where the immunogenic component of the IBD virus is inserted into a vector/carrier.
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