Equine piroplasmosis,
United States of America

Information received on 24/12/2009 from Dr John Clifford, Deputy Administrator, Animal and Plant Health Inspection Service, United States Department of Agriculture, Washington, United States of America

Summary

Report type Follow-up report No. 6
Start date 02/10/2009
Date of first confirmation of the event 19/10/2009
Report date 24/12/2009
Date submitted to OIE 24/12/2009
Reason for notification Reoccurrence of a listed disease
Date of previous occurrence 25/08/2009
Manifestation of disease Clinical disease
Causal agent Theileria equi
Nature of diagnosis Laboratory (advanced)
This event pertains to a defined zone within the country
Related reports
Outbreaks There are no new outbreaks in this report

Epidemiology
Source of the outbreak(s) or origin of infection
  • Unknown or inconclusive
Epidemiological comments The USDA Animal Plant Health Inspection Service (APHIS) and individual State Departments of Agriculture continue to conduct comprehensive epidemiological investigations of these events.

Update as of 21 December 2009:

Kleberg County, Texas outbreak:
• The NVSL has confirmed equine piroplasmosis (Theileria equi) in 357 horses that are directly epidemiologically linked to the index premises. The T. equi positive horses either currently live or previously lived on the index premises, or live on a premises immediately adjacent to the index premises, or are dangerous contacts (positive foal born to an infected mare, or temporarily boarded on index premises).
• The epidemiologically linked T. equi positive horses are currently located in 12 States as follows: 289 T. equi positive horses are located on the index ranch in Texas, 41 are on other premises in Texas, 2 are in Alabama, 2 are in California, 5 are in Florida, 1 is in Georgia, 2 are in Indiana, 5 are in Louisiana, 1 is in Minnesota, 2 are in North Carolina, 4 are in New Jersey, 1 is in Tennessee, 1 is in Utah, and 1 is in Wisconsin.
•Over 1,500 horses have been tested for equine piroplasmosis as part of the epidemiological investigation. This includes testing of 587 equine cohorts of positive T. equi horses outside of the index premises. All 587 cohorts tested have tested negative for equine piroplasmosis.
• All known T. equi positive horses are currently under quarantine.
• Transmission and entomological investigations/studies are continuing.
• Testing of all epidemiologically linked horses is ongoing.

Control measures
Measures applied
  • Control of arthropods
  • Quarantine
  • Disinfection of infected premises/establishment(s)
  • Dipping / Spraying
  • Vaccination prohibited
  • No treatment of affected animals
Measures to be applied
  • No other measures

Diagnostic test results
Laboratory name and type National Veterinary Services Laboratory (NVSL) (National laboratory)
Tests and results
Species Test Test date Result
Equidae competitive ELISA (c-ELISA) 15/12/2009 Positive
Equidae complement fixation test (CFT) 15/12/2009 Positive

Future Reporting
The event is continuing. Weekly follow-up reports will be submitted.