Avian Pneumovirus Key Info
Avian pneumovirus (APV),
also called turkey rhinotracheitis virus, is a newly emergent pathogen
that causes upper respiratory tract disease in turkeys. Originally isolated
in South Africa in 1978, APV was never detected in the USA until 1997 when
simultaneous outbreaks occurred in the States of Colorado and Minnesota.
Since then, APV has continued to be a problem primarily in Minnesota, even
though few positive cases in commercial flocks have been reported in North
Dakota, South Dakota, and Canada. The Minnesota turkey industry continues to
suffer severe economic loss, estimated at 15 million dollars per year due to
the disease. The losses are attributed to poor weight gain, mortality in
cases of secondary bacterial and/or viral infection, and processing plant
condemnation due to air sacculitis.
The clinical signs of APV disease include open mouth
breathing, sneezing, gasping, coughing, ocular and nasal discharges, foamy
conjunctivitis, and swelling of the infraorbital sinuses. In commercial flocks, weight loss and a
drop in egg production are also observed. APV outbreaks show 100 % morbidity
in susceptible flocks, and mortality, which is normally at 2-5%, can reach
30% in cases complicated by secondary bacterial and/or viral infection.
APV transmission is mainly by contact with infected birds,
since virus shedding begins early after exposure, and continues throughout
the period of clinical disease.
Susceptible turkeys get infected through the upper respiratory track
Analysis of the annual prevalence of APV outbreaks
in commercial flocks in Minnesota revealed that approximately 80% of flock
outbreaks occur in spring (April - May) and fall (October - December). This seasonal trend points to involvement
of environment factors in the maintenance and spread of the virus. Consistent with this finding, infectious
APV has recently been isolated in wild Canadian geese and viral RNA detected
in wild ducks, geese, sparrows and swallows.
Diagnosis of APV in the field
is currently performed by enzyme-linked immunosorbent assay (ELISA). APV can
also be detected by virus isolation from tracheal swabs or turbinates and by
reverse transcriptase polymerase chain reaction (RT-PCR).
Research efforts in progress include the
- Pathogenesis and immune response in APV infection.
- Molecular characterization
of emerging APV isolates in the US.
- Evaluation of killed APV vaccine.
- Completion of whole APV genome sequencing
and generation of a deletion mutant vaccine.
- Characterization of differential
gene expression following APV infection in turkeys.
- Evaluation of an avirulent
goose APV isolate as a vaccine candidate.