ViscerotropicVelogenicNewcastle Disease Outbreak in Missouri

The ADDL was notified by Dr. Francisco Collazo-Mattei of the USDA,APHIS-VS,Indiana Area Office that on July 16, 1996 a viscerotropicvelogenic Newcastle disease (WND) virus was isolated from two 6-week-old double yellow-head amazon parrots that belonged to an aviary in Rolla, Missouri.

On July 8, 1996, a VS foreign animal disease diagnostician was notified by a private practitioner of a Newcastle disease suspect. An investigation revealed that two young amazon parrots became ill on July 2 and were taken to the private practitioner to be euthanized. WND virus was isolated from frozen tissue samples that were forwarded from the University of Missouri to the National Veterinary Services Laboratory in Ames, Iowa.

An epidemiologic investigation identified the source of the Missouri parrots as a pet bird broker in Stigler, Oklahoma who received bird shipments two to three times a year from an unknown Texas source. An investigation of the bird broker and the Texas source is in progress. The broker received a shipment of 16 double yellow-head amazon parrots, as well as other birds, on June 1 from Texas. These birds were distributed to various locations. All premises associated with a shipment are under quarantine. There is no evidence of involvement of commercial poultry. The situation is restricted to two aviaries and a small number of pet birds in private homes.

Clocal swabs were collected from birds that were considered to be at risk. As of August 16 a total of five premises (seven birds) in Missouri have been diagnosed as positive for WND. Most of the birds on the affected premises have not become ill.

Newcastle disease virus is a paramyxovirusthat varies widely in pathogenicity. The pathotypesrecognized in chickens are lentogenic (mild), mesogenic (intermediate), and velogenic (severe). Velogenic strains can cause peracute death with no clinical  signs,  neurologic  signs,  or  acute gastrointestinal disease with abundant diarrhea (often green), anorexia, and lethargy. The susceptibility to WND virus varies among psittacifomies with amazons,  macaws,  and cockatoos reported to be highly susceptible and budgerigars and cockatiels to be of low to moderate susceptibility.

Most reports of WND in psittacines or commercial poultry can be traced back to imported caged birds as the source. The investigation is not complete in the present case. Emphasis on domestic breeding of pet birds should continue to minimize the risk to private aviaries or commercial poultry.

- by Rob Porter, DVM,PhD