Canadian Food Inspection Agency officials plan to test a south-central Saskatchewan cattle herd and neighbouring herds for anaplasmosis after one cow turned up positive for the disease.
According to the web site of the World Organization for Animal Health (OIE), CFIA confirmed the disease Oct. 10 in one beef cow out of an 89-cow herd in the Assiniboia region, 48 km from the Montana border. The agency submitted its report last Friday to the OIE.
The cow was slaughtered last Wednesday, but the source of the reportable disease in this case remains unknown, the OIE said.
The remaining herd will be retested after Nov. 15, 35 days after the first day of nighttime temperatures below 0°C, the OIE said, to allow for incubation time and die-off of vectors due to cold weather.
CFIA had tested the Assiniboia herd after finding an “anaplamosis seroreactor” in the an area previously defined as “high-risk” for the disease. The farm on which the animal was found is in the same area of Saskatchewan that was affected by an anaplasmosis outbreak in 1983, OIE said. Canada can harbour ticks capable of transmitting anaplasmosis, the OIE noted.
According to the report from CFIA’s Dr. Brian Evans to the OIE, the agency used ELISA and PCR (polymerase chain reaction) screening on 82 animals, which found the one PCR-positive cow, 80 ELISA-negative cattle and an ELISA-positive but PCR-negative animal.
CFIA’s trace-out investigation is expected to be completed this week, the OIE said. The cow’s herd has been quarantined and epidemiological investigation is “ongoing” on neighbouring farms that also have cattle.
Anaplasmosis, also known as “tick fever,” affects cattle, sheep, goats and deer and is caused by a microorganism that invades red blood cells. According to CFIA, adult cattle, particularly those over three years old, are usually most severely affected, with such symptoms as fever, anemia, weakness, respiratory distress and, in some cases, death. Affected dairy cattle will have a “rapid” decline in milk production. The OIE’s terrestrial animal health code recommends that anaplasmosis-free countries importing cattle from countries considered “infected” should require presentation of an international veterinary certificate attesting that the animals showed no clinical sign of anaplasmosis on the day of shipment and were, since birth, kept in a zone known to be free of bovine anaplasmosis for the previous two years.
Alternately, the certificate can attest that the cattle in question showed no clinical sign of anaplasmosis on the day of shipment, tested negative for anaplasmosis during the 30 days prior to shipment, and were properly treated with an effective drug such as oxytetracycline for five consecutive days.
Also, in either of the above cases, the cattle will need to come with certification that they were treated with an acaricide and, if need be, a repellant against biting insects prior to shipment, and were completely free of ticks.