EXOTIC NEWCASTLE DISEASE (END) ROCKS CALIFORNIA

Exotic Newcastle Disease (END), a highly fatal disease of poultry, was confirmed on October 1, 2002 in California and in early January 2003 in Las Vegas , Nevada . In both states the infection was originally diagnosed in backyard poultry, but in California has now spread to three commercial flocks 1.2 million birds), other backyard flocks and pet birds. The END is currently contained in a 30-mile radius in Los Angeles County and along the Los Angeles/Riverside/San Bernardino County border. Up to 90% of exposed birds are dying with a variety of respiratory, nervous and gastrointestinal signs. The California Department of Food and Agriculture initiated a door-to-door search in L.A. County and has also launched an education campaign for poultry growers. For the next three months, the U.S. Animal and Plant Health Inspection Service (APHIS) will be conducting an END eradication program in California . APHIS expects to use 100 people per week on an END Task Force to investigate and identify birds in the containment zone, perform necropsies, collect samples, and isolate the virus. Nationwide, state labs have been urged to provide workers for this tremendous control effort and the Wisconsin Veterinary Diagnostic Laboratory will be sending five employees for two-week stints through March. This highly contagious disease is rapidly spreading and poses a risk for all states and the entire U.S. poultry industry, which is why national cooperation is important. At this time over 280 premises in California have birds testing positive for END. California flocks, including chickens, turkeys, ducks, geese, grouse, partridges, pheasants, quail, pea fowl, pigeons, and ratites are under strict quarantine in five counties. Infected and exposed backyard poultry are being euthanized, disinfected and buried. To date nearly 1.2 million birds have died or have been euthanized. Canada and Mexico are currently banning imports of poultry products from California . If the Mexico ban on U.S. poultry products extends nationwide it will threaten a Mexican export market that was valued at over $70 million by October 2002.

Exotic Newcastle Disease also hit California in the early 1970’s, resulting in the destruction of 12 million chickens at a cost of 57 million dollars. The major challenge to control the current California outbreak is the tremendous concentration of poultry in the region, with an estimated 50,000 private owners having over 3 million game fowl for breeding and fighting. This puts the entire California poultry industry of 24 million laying hens, 38 million broilers and 8 million turkeys at risk. The debate on the control of END pits the philosophy of quarantine, limited slaughter and controlled vaccination against the traditional view of test and slaughter.

What is Newcastle Disease?

DEFINITION: Newcastle disease is an acute, rapid-spreading, contagious viral disease of birds of all ages characterized by lesions in the respiratory tract, internal organs and brain, and causing minor to severe mortality in susceptible flocks.

CAUSE: The ND agent is a paramyxovirus. The virus is present in the discharges from the respiratory and intestinal tracts. Therefore, the infectious ND virus can be transmitted by oculonasal secretions, feces, contaminated feed and water, movement of poultry, and infected wild birds. Perhaps the greatest potential for spread of Newcastle disease is by humans and contaminated equipment. There are three classes of ND virus corresponding to the level of disease they produce. The velogenic strains (Exotic Newcastle disease or END) will produce severe disease and high mortality in susceptible birds. The mesogenic strains cause respiratory disease or marked drop in egg production in field infections, but with less mortality. The lentogenic strains only produce a mild respiratory disease and are commonly used for vaccine production. Lentogenic stains can cause a moderate respiratory disease in broilers, but are rarely fatal unless complicated by secondary E. coli infection.

CLINICAL SIGNS: The clinical signs will vary with the age of the birds, strain of ND virus, the immune status of the birds, and the environmental conditions. In young birds that have little or no maternal antibodies, are under undue stress or haven’t been vaccinated, the clinical signs can be severe.

Velogenic Form (Exotic Newcastle Disease) - spreads rapidly through a susceptible flock. Birds may be found dead without any signs. Initially, birds are observed depressed with increased respiration. There is progressive weakness and prostration. The birds develop a watery greenish diarrhea. A marked cough and gasping respiration, nasal and eye discharge are often present. Comb and wattles may turn dark and bluish, and birds may develop swollen heads. Birds that survive the initial acute phase show involvement of the nervous system. Egg production drops sharply and deformed eggs are present. Mortality is usually over 9O% in a susceptible flock. With the velogenic strain, there are varying degrees of congestion and hemorrhages in visceral organs, including the proventriculus, ceca, and small intestines. Chickens and turkeys infected in lay usually reveal egg yolk in the abdominal cavity.

Mesogenic Form - the clinical signs are similar to the velogenic form, but less severe. Mortality may vary from 5-50%, depending on the age of birds and environmental conditions. Nervous signs may occur but are not common. With the mesogenic form, hemorrhages may occur in the proventriculus and less commonly in the small intestines. Clear fluid can collect in the nasal passages, larynx, and trachea.

Lentogenic Form - characterized by mild respiratory symptoms and by a sudden drop in egg production. The egg production returns to normal within a few weeks and birds completely recover from the disease. In young susceptible birds, severe respiratory disease can occur with tracheitis as the primary lesion.

DIAGNOSIS: A presumptive diagnosis can be made based on the clinical signs, lesions, and serology tests. A positive diagnosis of the causative virus can only be made by isolation and identification of the virus by embryonated chicken egg inoculation. Specimens for virus isolation (trachea, oropharynx, cloaca) should be selected from birds showing early clinical signs of the disease.

TREATMENT: There is no effective treatment against the ND virus. Broad-spectrum antibiotics may help in reducing secondary bacterial infections. Use good management practices to reduce any additional stress on the birds.

PREVENTION: Prevention of Newcastle disease involves having a sound biosecurity. Keep unauthorized personnel out of the poultry house, and maintain good clean-out and sanitation procedures. In some instances vaccine can be effective, but may not be effective in preventing infection with END. Poultry vaccines are produced from lentogens and mesogens. For hobby flocks or backyard chickens, particularly those that have access to the outdoors and wild birds, or those that are routinely mixed with other birds at swap meets and shows, only a killed vaccine should be used because is might be possible to transmit a live vaccine virus between birds.

What does END mean for Wisconsin ?

Currently END has not been identified in Wisconsin or other Midwest states and the key is strict biosecurity. Both the commercial poultry industry and backyard poultry hobbyists should be particularly careful at this time not to bring new birds onto their premises, particularly birds whose origin is poorly documented. Of particular risk are swap meets, live bird markets and poultry shows that may result in congregation of birds from many different states. For the time-being do not mail order birds from western states. Additionally, if you have a flock that has a high death loss with suspicious clinical signs it is essential to contact your local veterinarian or county extension agent and deliver the dead or sick birds to the Wisconsin Veterinary Diagnostic Laboratory for a complete diagnostic workup. Prominent signs of END in California flocks and those that you should look for in your birds include depression, wheezing, sneezing, head shaking, wing droop, leg paralysis and diarrhea. The primary lesions observed in California poultry include a yellow to white diptheritic membrane covering the oropharynx and trachea, conjunctival hemorrhage, tracheal edema, and hemorrhage in the cecal tonsils, proventriculus (Figure 2) and esophagus. Many diseases of birds can appear similar, so a complete diagnostic examination by a veterinary pathologist, including gross evaluation, microscopic examination of tissues and virus isolation are needed for a diagnosis.

If you have questions about the diagnosis or control of this disease, what it may affect your flocks, or any other information in this report please contact Dr. Rob Porter, avian diagnostic specialist at the Wisconsin Veterinary Diagnostic Laboratory (608)262-5432, rob.porter@wvdl.wisc.edu.

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