The partners of Arkansas’ poultry industry do everything they can to prevent a foreign animal disease outbreak – because if such a disease does appear in one of the state’s flocks, the results could be catastrophic.
Dr. F. Dustan Clark, University of Arkansas Extension poultry health veterinarian, told Ozarks Farm & Neighbor producers routinely vaccinate for diseases like bronchitis, Mareks and Infectious Bursal disease. The majority get the first dose while still in their shells; “Chicken eggs hatch in 21 days,” he said, “so at 18 days of incubation the birds are vaccinated in the egg when the eggs are transferred from the incubator to the hatcher. Then once they hatch they’re usually vaccinated the first day often using a ‘spray’ vaccination technique, where they’re given a vaccine by a fine spray against some of the respiratory diseases – Newcastle and bronchitis, for example.”
The common form of Newcastle is not to be confused with its foreign disease counterpart; there are two strains of the domestic disease, called lentogenic and mesogenic. “It is usually very, very mild,” said Clark. “A little cough, a little sneezing; maybe a little runny nose.” If a laying hen gets Newcastle or infectious bronchitis it can lead to a loss of eggs, and a meat flock could fail to perform, so they’re vaccinated against those diseases.
Exotic Newcastle, or END, is an entirely different matter; there is no vaccination used in the USA since the disease is not present in the USA, so if a flock was found with the disease it would be quarantined and destroyed. This is very, very rare in the U.S.; the last known outbreak was in California in 2002-03 and resulted in the destruction of 3.2 million birds, as California’s state veterinarian and USDA’s Animal and Plant Health Inspection Service fanned out to monitor surrounding flocks. The symptoms are apparent; Clark said, “You saw bird losses – you can have incoordination, serious respiratory disease, production losses and high death losses.”
Another foreign animal disease that could affect birds in the U.S. is avian influenza. Avian Influenza is caused by a virus and can be of two types in poultry; low pathogenic or highly pathogenic. The low pathogenic type causes mild, if any, symptoms in the birds; compared to highly pathogenic which can cause severe signs and losses. Flocks in the U.S. are routinely blood tested for the disease as part of a preventative surveillance effort before they are marketed. In 2008 an Arkansas commercial flock tested positive for low pathogenic avian influenza on routine surveillance blood testing. That flock was destroyed and surveillance testing of surrounding commercial and backyard/hobby flocks showed no other positives. Clark said producers practice biosecurity measures to protect their flocks from exposure to disease.
Among those is all-in, all-out production: “In a poultry house, all the birds go out to market at the same time. Then when they restock that house, the whole house is stocked, and that’s done for the whole farm; if there are three houses on the farm, all three go out at the same time, and they all come back and replace the baby chicks at the same time.”
Biosecurity Measures
Clark has produced a checklist for producers to assess their own on-farm biosecurity; among practices to be avoided are borrowing equipment from other growers, allowing wild animals access to dead birds, and using untreated groundwater to water birds. In a 2002 article, Dr. Frank Jones, who is now retired from the Center of Excellence for Poultry Science, University of Arkansas, pointed out the ripple effect if a foreign animal disease were to shut down an Arkansas poultry complex – farmers’ birds could not be placed, workers at the processing plant, feed mill and hatchery could be laid off, bank notes might not get paid, surrounding retailers could lose business and reduced taxes might curtail public services. “Now that you know the consequences of such an outbreak,” he concluded, “wouldn’t it be nice to prevent one?”
Research And Results in Vaccinations
The more common diseases are also to be avoided, but vaccinations are heavier for laying and breeding hens, which will produce for 65 weeks or longer, than for broilers, which are headed to market in 42-49 or so days. For the same reason, although producers will apply coccidiostats to control coccidiosis, digestive problems caused by the protozoan parasites or internal parasites in commercial flocks tend to be less significant. Therapeutic antibiotic use is very rare; Clark said instead, “We can do some selective marketing such as sending unaffected birds to market earlier than planned if a disease problem is in an area, or some selective culling of affected birds in a house, etc.”
Vaccines are selective for virus strains known to be active in specific regions of the country; poultry health specialists and pharmaceutical companies continually monitor flocks so the preventive inoculants can be tailored. In some cases, Clark said, vaccines have “cross-reactivity” and will be active against more than one strain of the virus. If birds are found to be low in antibodies against one particular strain, they may need to be revaccinated. “The breeder birds are vaccinated so that the hen produces an egg that has antibodies in it,” he explained, “so when the chick hatches it already has a certain level of what we call maternal antibodies through the egg yolk itself.” The shots in ovo and spray vaccination at one day old provide further protection.
“Do new viruses crop up now and then, and can we get a change in those in an area?” he said. “Absolutely, and with that you may have to change your vaccination program; you may have to add a different strain of a virus in there. With any living organism, such as a virus or a bacterium, there is always the potential that it can change a little bit, so the companies look for this, and there are new vaccine developments. You always want to have something that is as protective as it can be, that causes very little problem. There’s research going on here at the University of Arkansas and other universities, looking at things that could be used for a better vaccine – one that would be more protective, or one that you could use less vaccine or give at an earlier age.”
