Dr Fambies van Biljon, veterinarian at Sovereign Foods, talks to Glenneis Kriel about the crucial need to establish a well-run biosecurity programme at a poultry production facility.
Why is biosecurity so important? Why can’t birds simply be medicated when they fall ill?
The problem with poultry production is that many avian diseases, such as avian influenza and Newcastle disease, have no cure. So the best strategy is to prevent these diseases from entering your farm in the first place through a good biosecurity and sanitation programme.
The worldwide movement against the use of antibiotics due to rising fears over antimicrobial resistance is also putting pressure on farmers to use more preventative control measures. Even here in South Africa, cases of E. coli resistance have been reported for certain antimicrobials. Antibiotics should be used only as a last resort, and then as prescribed by the veterinarian who identified the disease.
What about vaccines?
These are widely used for most poultry diseases, but currently vaccines for highly pathogenic avian influenza (HPAI) are not registered for use in South Africa due to fear of negative consequences for international trade. In addition, there are concerns that vaccination would mask a future outbreak.
It would be difficult in any case to vaccinate against HPAI as vaccines are strain-specific: no single vaccine covers all cases of HPAI. Local producers prefer to destroy chicken populations that have become infected.
HPAI vaccines are, however, widely used in countries where the disease has become endemic, such as China and Egypt.
In addition, vaccines are not foolproof, as birds can still contract a disease after vaccination. There are several reasons for this: the vaccine might have been stored or administered incorrectly; the dosage might have been wrong; the medication might have been past its use-by date; or the birds might have had weakened immune systems, or been stressed or already infected when the vaccine was administered.
None of this means that vaccines should not be used; rather, they should be part of a greater disease management strategy that buffers the impact of highly contagious diseases such as Newcastle disease and mycoplasma.
What exactly should an effective biosecurity programme entail?
You need to prevent, as far as possible, contact between an existing flock of birds and anything that might be carrying a disease. This includes visitors, veterinarians, equipment, clothing, vehicles and other animals.
The ideal is to enclose the production area with an electric fence and establish an office where all visitors and staff must report and through which they pass to enter the farm. In this building there should be a shower where people can be sanitised before entering the production premises.
This should be a walk-through design, with the sanitised area on the inside. All clothing should be left outside, and visitors should be supplied with farm clothing on the clean side.
This clothing should be washed and tumble-dried and should have no contact with any potential threats.
Any equipment brought along with visitors, including spectacles and cellphones, should be sanitised before entering the farm.
Staff should only wear clothing provided inside the production area. This is particularly important in the case of gumboots, as these have soles with folds that easily trap pathogens. If an employee has, for example, inadvertently stepped in droppings from a wild bird carrying an avian disease, merely stepping into a footbath may not be sufficient to prevent an outbreak of the disease in the production area.
Feed trucks present a major risk as they often drive from one farm to another. The best solution is for the trucks to offload feed outside the farm, but unfortunately, many farms are not geared for this.
Wheels, wheel wells and mudflaps should be sanitised before these vehicles are driven onto the premises, and feed transport drivers should preferably remain in their trucks. No unnecessary vehicles should be allowed onto the farm.
In the same way, visits by veterinarians and technical representatives should be limited, as these people usually visit many farms during the course of their work and often have contact with diseased animals.
Showering should minimise these risks, but these visitors could, for example, be carrying a threat such as mycoplasma in their nostrils, and sneeze the disease into the production area.
The most effective way to reduce this danger is only to allow veterinarians and technical representatives onto the farm two days or longer after they have been in contact with birds on another farm.
You identified other birds as a threat for HPAI. How can wild birds be kept out of the production area?
The production area should be birdproofed, and nests close to the production premises removed. Under current conditions, I think the risk of HPAI is too high to undertake free-range production.
Free-range farmers can use bird nets to reduce the risk, but these won’t help much as the disease is carried via the droppings, feathers and eggs of wild birds.
Another important point to consider is that avian influenza is carried primarily by wild waterbirds, which can also contaminate water resources with the disease. The production area should therefore preferably be situated away from streams and open dams. Drinking water from boreholes, rivers and dams should be chlorinated to reduce disease risk.
What role does stress play in all of this?
Birds should be kept as stress-free as possible, as stress can render them more vulnerable to diseases. I suspect that many flocks end up with E.coli problems in winter because of poor ventilation and temperature control.
Would keeping indigenous birds help reduce the risk?
Financially, it makes more sense to keep a commercial breed. I’m not always sure about the heritage of some of the birds kept as village chickens. The consensus, however, is that birds kept at lower densities under free-range conditions are generally more resistant to disease than birds kept under higher densities.
On the other hand, there is a risk of avian influenza with birds being kept outside, as they are much more likely to make contact with wild birds that could be carrying the disease.
Do you think the spent hen industry will be halted because of the avian influenza outbreak?
The spent hen industry poses a huge risk, as it involves the sale to hawkers of live birds that have reached the end of their productive lives.
The financial contribution that the sale of spent hens brings to farm income, however, cannot be discarded, so I doubt that the practice will be prohibited in the near future. The ideal would be for abattoirs to be become equipped for the slaughtering of spent hens.
（January 12, 2021. From “Farmer’s Weekly” )
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Post time: Jan-12-2021