Kari has issued warnings to farmers to be alert to signs of the deadly chicken fowl pox, following outbreaks that killed hundreds of chickens around Naivasha this year. The disease is responsible for over 40 per cent of chicken deaths, and is common during rainy seasons, but can be limited through both disinfection and vaccination.
Birds easily get the virus from mosquitoes and other biting insects, whose population increase tremendously during the rains. “We have had farmers reporting huge losses over the last six months,” said Phylis Chemutai from KARI Naivasha.
Fowl pox is a slow-spreading highly contagious viral infection of poultry. The virus attacks the skin, the surface of the mouth and throat, leading to wounds that progress to thick scabs. The disease may occur in any age of bird, at any time. But recovered birds do not remain carriers.
However, avipoxvirus, the virus that causes the disease, is very resistant to drying and can survive in scabs for several years. Different strains of the virus affect different species of birds, with fowl and turkey prone to the fowl pox virus.
Farmers have been warned to be on the look out for early signs like odd scabs on the comb that gradually darken, and usually playful birds just standing around with their eyes closed and head under their wings. These first scabs darken and fall off in about a week. Bacteria may gain access causing secondary infection resulting in pus and necrosis. Affected areas on the skin completely heal in 2 to 4 weeks if the lesions are not too extensive. The birds become weak, emaciated, show vision problems, difficulty in swallowing and breathing. Others have soiled facial feathers, conjunctivitis, and edema of the eyelids. Laying birds decrease egg production.
The disease can be spread by direct contact with infected birds, mosquito bites and eating or breathing in contaminated materials. Transmission within a flock is rapid when there are plenty of mosquitoes and is usually observed in seasonal mosquito cycles. Mosquitoes can harbour and transmit the virus for a month or longer through bites after biting an infected bird.
Chemutai said the disease usually occurs in two forms, the dry pox or wet pox, depending on location.
The dry form is the most common, affecting the skin and causing wart-like eruptions, which in many cases are found primarily on the feet and legs.
The wet form affects the mouth, throat, trachea and lungs, causing yellow or white raised and moist necrotic areas that interfere with eating and breathing. Sometimes lesions on the eyelids causes the closure of one or both eyes.
“However both forms of pox are fatal if immediate help is not sought,” she said, citing the outbreak of fowl pox around Naivasha from March this year, which affected mostly free range poultry farmers and left some 1200 chicken dead.
“They just kept on dropping and dropping and within two weeks there was nothing left. It was like watching people die in a war zone. It happened so fast and before we could get remedy it was too late,” said Kihara Nduire, a poultry farmer who lost his 50 chicken to the disease.
Ordinary management and sanitation practices will not prevent fowl pox. But farmers can save their flocks through vaccinations when less than 20 per cent of the birds have lesions. Several kinds of fowl pox vaccines are available and are effective if used properly.
Scientists say two methods of vaccination can be used, which include the 'needle stab' or 'stick' method and the follicle method.
In the first method, two grooved needles are bound together to make a double-pronged instrument that is dipped into the vaccine and thrust through the wing web. In the second method the vaccine is swabbed into feather follicles where sufficient feathers had been plucked from the bird's thigh to expose the skin. Successful vaccination is indicated by small scabs or swollen follicles called "takes," at the inoculation site.
However prevention is always better and cheaper than cure, said Chemutai, “Which is why simple control methods like eliminating standing water and all mosquito habitats to control mosquitoes, isolating infected birds to remove the source of the virus and disinfecting feeders, waterers, birdbaths and cages with a 10 per cent bleach solution go a long way in reducing the risk of infection,” she said.
These measures, which KARI used to train farmers in the Gilgil area, reduced chicken mortality by 80 per cent and helped families cut Sh200 in treatment expenses per bird.
Written by Bob Koigi for African Laughter
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