Turkey coronaviral enteritis in Indiana turkey flocks in 2009

Since 1995, Tom Hooper, ADDL-Heeke, has performed serological testing against turkey coronavirus (TCoV) using direct and/or indirect immunofluorescent antibody assays for more than 180,000 turkeys from U.S. turkey flocks.  More than 32,000 serum samples were tested in 2001 from various turkey producing states.  Requests for TCoV serology have diminished since 2001; 7,848 tests were performed in 2008.

TCoV has been quiet in southern Indiana turkeys until September 2009.  An 8-week-old commercial male turkey flock was showing increased water consumption and wetter litter.  No increased mortality was seen.  Virus was isolated in embryonated turkey eggs.  The flock was marketed at 20 weeks with below average body weights but normal livability. Serological tests against TCoV have been run on turkey flocks with clinical enteritis as well as those in the surrounding areas.  Flock supervisors have been diligent about submitting six serum samples twice in two-week intervals for detection of antibodies to TCoV in order to confirm infection.  Tom Hooper has provided Drs. Tsang Long Lin and Ching Ching Wu TCoV isolates for comparison of genetic uniformity among TCoV isolates over the years because chicken coronaviruses (infectious bronchitis virus) tend to vary.  TCoV isolates from various geographic locations in the U.S., including those from Indiana, have been found to possess more than 90% genetic similarity and share close antigenicity over the last 15 years.  Nevertheless, genetic analysis of Indiana TCoV isolated in 2009 is being conducted by Drs. Lin and Wu.

Clinical summary :  In discussion with submitters for TCoV serology over the years, Tom Hooper and Dr. Tom Bryan have felt that the virus can show very few signs in some flocks, but persists quietly until feed conversions are noted and testing commenced.  Routine serological profiles against TCoV have been helpful to the turkey industry for those subclinical flocks mentioned above as well as the clinical flocks that need turkey turkey coronaviral infection controlled by biosecurity measures and eradication programs.

-by Dr. Tom Bryan, Heeke ADDL Avian Diagnostician

References

1. Lin TL, Loa CC, Wu CC, Bryan TA, Hooper T, Schrader D: 2002.  Antigenic relationship of turkey coronavirus isolates from different geographic locations in the U.S.A.  Avian Diseases 46:466-472.

2. Loa CC, Lin TL, Wu CC, Bryan T, Thacker HL, Hooper T, Schrader D: 2001.  Humoral and cellular immune responses in turkey poults infected with turkey coronavirus.  Poultry Science 80:1416-1424.

3. Loa CC, Lin TL, Wu CC, Bryan TA, Hooper T, Schrader D: 2006.  Comparison of 3' End Encoding Regions of Turkey coronavirus Isolates from Indiana, North Carolina, and Minnesota.  Intervirol 49:230-238.

4. Patel BL, Gonder E, Pomeroy BS: 1977.  Detection of turkey coronaviral enteritis (bluecomb) in field epiornithics, using the direct and indirect fluorescent antibody tests.  American Journal of Veterinary Research 38:1407-1411.