Articles

Outbreaks of poult enteritis mortality syndrome (PEMS) have caused devastating economic losses to the turkey industry since its emergence in 1991. Recently completed addressed the development of diagnostic antibodies against a new virus isolated from PEMS-infected turkeys.

The research, "Development of Diagnostic Antibodies Against a New Virus Isolated From the Thymus of Poult Enteritis Mortality Syndrome-Infected Turkeys," was conducted—and reported—by Stacey Schultz-Cherry, Ph.D. of the Southeast Poultry Research Laboratory in Athens, GA.

Many infectious agents have been isolated from PEMS-affected turkeys, the causative agent remains unknown. The new research isolated a "small round virus" from the thymus of PEMS-affected turkeys that was recently defined as a novel turkey astrovirus based on its genomic composition. This astrovirus is distinct from the astrovirus that circulated in turkeys in the 1980s.

The research sought to to develop antibodies to the "small round virus" (astrovirus), to develop a diagnostic test for astrovirus and to determine its role in PEMS.

During these studies, highly specific antibodies against the astrovirus were produced that detect the astrovirus in the intestines of infected embryos, and in the feces and tissues of infected turkeys by many different techniques including western blot, ELISA, and indirect immunofluorescence.

Current studies are focused on developing a diagnostic ELISA test to detect antibodies against the astrovirus in the serum of commercial turkey flocks. Additionally, a highly sensitive and specific molecular "RT-PCR" test was developed that that detects the astrovirus in the feces and intestines of commercial turkeys. This test successfully identified PEMS-associated astrovirus in turkeys in the southeastern United States, Texas, Arkansas, Virginia, Michigan, and California.

Currently, there are two diagnostic laboratories using this test to screen commercial turkey flocks. The RT-PCR test was developed to detect the PEMS-associated astrovirus as well as any emerging or new strains of astrovirus. The RT-PCR test will be most useful to monitor young flocks placed in brooder houses (from day of age - three weeks of age) or sick turkeys.

Finally, the researchers found that the astrovirus causes a disease similar to the mild form of PEMS affecting the immune system of the young birds, potentially leaving them susceptible to devastating secondary infections. Of concern, many commercial disinfectants fail to inactivate the astrovirus. Therefore, it will be critical to monitor houses for the presence of astrovirus after clean-out before the placement of new poults. The RT-PCR test coupled with a serological test will provide the turkey industry with the tools to monitor flocks from day of age through processing for infection with the astrovirus.

These diagnostic tests will aid in understanding the role of astrovirus in enteric diseases of turkeys and PEMS.

The project was partly funded by the U.S. Poultry & Egg Assn., Tucker, GA, association's $2 million-plus research budget for broiler, turkey, and commercial egg operations. The work was done under the direction of the Agricultural Research Service of the U.S. Dept. of Agriculture.

Edited by Bob Sperber