Many vets and farmers will never wish to encounter Newcastle Disease (NCD). In it is virulent form, the disease can silence the whole flock in just two weeks.
The disease is a global problem; only two countries — US and Canada have managed to put it at bay; although strictly speaking - they may not be free since the disease is also carried by migratory birds that know no border.Luckily the disease can be prevented through vaccination.
Newcastle disease is an infectious viral disease of all birds – Turkeys, geese, ducks and parrots. But its severity differs across the species and immunity status. The disease has a short incubation period sometimes as little as two days post exposure.
For this deadly disease, prevention is the only cure. It comes in both mild and virulent forms; chicken and especially young chicks are most susceptible.
Wild birds like waterfowl and cormorants are NCD carriers for the domestic chicken. The domestic pigeon species, which many farmers keep together with the domestic chicken are also susceptible but not as much as chicken therefore adding to the number of potential sources to your unvaccinated flock.
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RESTRICT VISITORS
Even in farms where vaccinations are done against the disease, many will not think of the domestic pigeons, ducks or the turkeys leaving a loose end in the control of NCD.
Sick or carrier birds will share the virus through exhaled aerosols, droppings and their carcasses, which can contaminate the environment – food, water, litter and other objects. In infected birds the virus can be carried in the eggs subsequently causing infections in chicks.
Direct contact with infected birds and contaminated food, water and equipment will spread the disease. This requires thorough disinfection of contaminated houses before introduction of another batch of birds.
All-in-All-out management of birds can also reduce chances of NCD infections.
Human beings can also spread the disease from one farm to another. This happens though contaminated hands, shoes and clothes. Many farmers take pride in their commercial poultry business and it forms the first stop for any Tom, Jack and Harry visiting their farms. When such visitors are from a contaminated farm get in contact to your healthy birds, NCD can be spread.
In addition, vehicles entering your farm must have their wheels and undercarriage disinfected at the gate.
Your farmhands in the poultry unit need to wear clean clothes while on the farm; they should not use the street clothes in the poultry unit. In other words bio-security measures on poultry farms will reduce chances of the disease flare up in your farm.
Unlike other viruses, the NCD virus can linger around in the environment for a while before dying; this period is even longer in cool environment. The disease can either affect the nervous or respiratory systems and will show clinical signs specific to the affected system.
If it has affected the respiratory system, the birds will gasp for air, cough and sneeze.
When the nervous system is affected the birds will move in circles, twist their necks and will have wing and leg paralysis. Greenish watery diarrhea and swelling of the head may also occur. There is no effective treatment for NCD but birds that recover develop a long lasting immunity.
There are several vaccines against NCD available in the market. Some are administered in drinking water, some as sprays or as drops. The number of administration is determined by the virulence of the implicated strain and risk of exposure.
The greatest challenge in initial vaccines was the loss of potency when it is handled at room temperature for over two hours, making it unsuitable for rural areas where this disease challenge is greatest. Recently the Kenya Veterinary Vaccine Institute developed a thermostable version of the vaccine available to farmers at an affordable cost.
Different hatcheries and manufacturers have their schedule for NCD vaccinations; enquire for this information when sourcing for your foundation stock.
- The writer is a veterinary surgeon working with the Kenya Tsetse and Trypanosomiasis Eradication Council –KENTTEC
