5/18/2013 7:00 AM
By Charlene M. Shupp Espenshade Special Sections Editor
LANCASTER, Pa. — Patty Dunn and other members of the Penn State Animal Diagnostic Laboratory have been busy this past year following what is happening with reovirus infections in Pennsylvania broilers.
Several companies detected a problem and acted proactively by requesting testing.
“We were one of the first to dig in and think it was not going away,” Dunn said of the state’s poultry industry after a spike in positive tests in early 2012.
The reovirus, short for respiratory enteric orphan virus, is not new. It was first identified in the 1950s and is found throughout the world. A clinical case depends on the pathotype and age of the bird.
About 80 percent of the reoviruses found in chickens are nonpathogenic. The latest spike is the result of pathotypes causing pathogenic infections that are not covered under current commercial vaccines.
Dunn spoke to more than 30 poultry industry and farm representatives at Monday’s Penn State Poultry Health Seminar at the Eden Resort in Lancaster.
Reovirus is primarily a problem in meat-type birds and causes the inflammation of the tendons. Dunn described the infection as affecting synovial fluid, which is the tendon and joint lubricant.
The infection can cause the rupture of the tendons and threaten the bird’s mobility, growth, digestion and life.
This virus can transfer vertically from hen to chicks and horizontally from bird to bird. The latest rise in reovirus cases started in February 2012.
“It’s not just three companies anymore” and most Pennsylvania companies have had cases of reovirus, Dunn said.
Flocks with the infection showed lameness, uneven growth and decrease in weight gain. Birds also showed inflammation of the tendons. Lab results have found higher than normal levels of antibody titers in birds with the virus.
What does this mean? For one thing, birds heading to the Kosher market could be rejected during the rabbinical inspection process, and if a company does not have an alternative market, “it’s a huge dollar loss,” she said.
Dunn showed photos depicting different variations of the tendon infection.
Looking outside Pennsylvania, the same situation is occurring in “virtually all broiler production areas,” she said.
Why is there a problem?
Dunn said she’s “not sure why, it seems to be a proliferation of reovirus isolations” and to be vertically transmitted, which is not surprising considering the nature of chick distribution.
“It’s not a criticism, it’s just the nature of the game,” she said.
So what is a grower to do?
The short-term solutions are the obvious farm practices of increased downtime between flocks along with good cleaning and disinfection of facilities, and control of darkling beetles.
Long-term control includes vaccination programs and evaluations. Traditionally, breeders are vaccinated before they begin laying to prevent prevent transmitting the virus to the eggs and to provide antibodies to the chicks.
A new autogenous vaccine, a killed virus made with three reovirus isolates from Pennsylvania broiler cases in 2012, has had some positive results. This vaccine has been in use by Pennsylvania breeders since the fall of 2012 and has been effective so far.
Dunn said there could be some expansion of the use of the autogenous vaccine to operations with multiple flocks or premises if epidemiologic links can be established to current strains. That might also allow a regional approach to use of the vaccine.
“I would not assume all leg problems are reovirus,” Dunn said. “But I would not assume all leg problems are not reovirus.”
Many attendees asked if a commercial vaccine is on the horizon.
Dunn said not in the short term and that it could be years before one is developed and available for sale.