| | What is Anaplasmosis?
Anaplasmosis is an infectious, non-contagious disease that affects ruminants, including cattle, bison, sheep, goats, deer and elk.
How it is transmitted?
Anaplasmosis is caused by a parasite called, Anaplasma marginale. It invades and multiplies in red blood cells. This parasite can be spread both mechanically and biologically. Mechanical transmission occurs by direct inoculation of cattle with blood-contaminated hypodermic needles, and surgical or dehorning instruments. Tabanids, including horseflies, may also mechanically transmit the disease on their mouthparts after taking a blood meal from an infected animal. Ticks are biological vectors of A. marginale and spread of the disease is most likely to occur through infected tick bites. The species of ticks important in spreading A. marginale are present in Alberta. Outbreaks of anaplasmosis are usually seasonal and occur during or immediately after the vector season.
What are the symptoms?
As the disease progresses, infected red blood cells are destroyed causing anemia and occasionally death. Animals sick with anaplasmosis may have a fever, and be off feed, depressed, dehydrated, show rapid or difficult breathing and have anemia. A few animals may also become excited or aggressive if enough oxygen doesn’t reach the brain.
Cattle of any age can become infected but calves rarely become sick. Infected calves may become carriers of the parasite. On the other hand, up to 30 to 50 percent of cattle that become infected at three years of age or older may die if they develop clinical signs of the disease.
Are humans susceptible?
No, anaplasmosis does not affect humans.
How is the disease diagnosed?
The presence of A. marginale may be confirmed in a sick animal by identifying the organism in a blood smear. Other specialized laboratory tests, such as serology, are required to detect sub-clinical carrier animals.
Can A. marginale be eliminated from carrier cattle?
Once infected with A. marginale, cattle remain infected for life. Current science indicates that treatment of infected cattle with tetracycline only temporarily eliminates the parasite from the animal’s blood; treatment does not eliminate the organism from the carrier animal. At this time, there is no known method of eliminating the organism from carrier animals.
Is anaplasmosis present in Canada?
Canada is free of anaplasmosis. The Canadian Food Inspection Agency (CFIA) has conducted a survey involving over 15,000 slaughter cattle every three years for anaplasmosis. The most recent survey was completed in 2003 and again verified Canada’s disease free status regarding anaplasmosis.
Occasional outbreaks of the disease have been identified in cattle and farmed bison. In 2000, 18 bison in Saskatchewan tested positive for anaplasmosis. How they contacted the disease remains undetermined. In 1996, five domestic cattle were destroyed after they came into contact with anaplasmosis-carrying cattle imported into Canada illegally. The illegally imported carriers were also destroyed. There was no further spread of the disease.
Cattle entering Canada from countries not free of anaplasmosis must be tested free of A. marginale. An exception to this requirement is the importation of feeder cattle from the United States into Canada under the Restricted Feeder Cattle Entry Program. Under this Program, feeder cattle can be imported into Canada without testing for anaplasmosis provided they go to an "Approved Feedlot". These animals must come from American States demonstrating equivalent health status to Canada regarding tuberculosis and bovine brucellosis. Cattle under this program no longer require treatment with tetracycline but must be treated at the time of arrival with an approved product to control ticks. Cattle imported from Hawaii are exempted from this treatment. For details on importing cattle under the Restricted Feeder Cattle Program, consult CFIA’s website at http://www.inspection.gc.ca/english/anima/heasan/policy/ie-2001-14e.shtml.
What countries have anaplasmosis?
Anaplasmosis is found on all six continents, especially in countries with warmer climates, including Australia and southern Asia. It is also commonly detected in the United States, mostly in the southeast and in California. Infection with A. marginale is occurs only occasionally in temperate climate areas.
What would happen if an outbreak were to occur in Canada?
Anaplasmosis is a Reportable Disease under Canada’s Health of Animals Act, meaning that CFIA must be notified immediately if the disease is suspected or diagnosed. CFIA has the legislated mandate to control an outbreak of anaplasmosis and would put the affected farm under quarantine. All animals testing positive would be depopulated. The owner would be entitled to compensation for all animals ordered destroyed under the federal legislation.
Wildlife may also become infected with A. marginale, however, they do not show signs of disease. They may act as a reservoir for the parasite.
Updated January 2008
For further information, contact:
Dr. Gerald Ollis, Chief Provincial Veterinarian
Alberta Agriculture and Food
Tel: 780-427-3448
Fax: 780-427-1437
Email: gerald.ollis@gov.ab.ca |
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