Effective April 1, 2014 Anaplasmosis is no longer a federally reportable disease and is now listed as immediately notifiable disease. This change will mean that:
- Only diagnostic laboratories will be required to report suspected or confirmed cases to the Canadian Food Inspection Agency (CFIA)
- The CFIA will no longer respond to anaplasmosis cases detected on farms
- The CFIA will no longer conduct surveillance for anaplasmosis to verify Canada's status for the disease
- Cattle, bison and elk producers in Alberta will have to contact their herd veterinarian to examine animals that are showing clinical signs suggestive of anaplasmosis.
- All breeding cattle, feeder cattle and bison imported from US into Canada will not be required to be tested for Anaplasmosis.
- It will be the buyer's responsibility to ensure that the purchased animals are free of Anaplasmosis and the buyers should consult their herd veterinarians to obtain the relevant advice to prevent introducing the disease in their herds.
- Anaplasmosis in cattle, bison, cervids, sheep and goats is a provincially notifiable disease and any suspected or confirmed cases of anaplasmosis must be reported within 24 hours to the Office of the Chief Provincial Veterinarian at the following address:
Dr. Keith Lehman
Chief Provincial Veterinarian
Animal Health and Assurance Branch
Alberta Agriculture and Forestry
Tel: 780-427-3448 – Office Hours
Tel: 1-800-524-0051 – After Hours
Alberta Agriculture and Rural Development will not be engaging in testing and control of the disease in confirmed infected cases in the province. Producers with the assistance from their herd veterinarian will be responsible for prevention, testing and treatment of the disease on the farm.
What can livestock producers do to reduce the risk of Anaplasmosis?
- Livestock producers play an important role in keeping their animals healthy and are encouraged to talk to their veterinarians about the disease and prevention of the disease.
- Producers must comply with all import requirements when purchasing animals from outside of Canada. This may include testing of animals for other diseases prior to import, depending on the country and location of origin.
- Once Anaplasmosis is in the herd, it is costly to treat and difficult to control
Owners should consider:
- testing the animals for absence of the disease if importing from endemic regions.
- treating the animals with an effective acaricide to kill all ticks that may be on the animal before introducing the animals in the herd.
Anaplasmosis – The Disease
- Anaplasmosis in cattle is an infectious disease of the red blood cells caused by the rickettsial bacteria Anaplasma marginale. Most commonly transmitted by ticks, A. marginale primarily causes disease in cattle. Other domestic and wild ruminants such as bison, deer, elk, sheep and goats can be infected, but clinical disease is uncommon.
- Anaplasmosis is endemic in many areas of the world including parts of the United States, while Canada experiences sporadic cases. Since 2000, a bison herd in Saskatchewan, beef cattle in Manitoba and a dairy herd Ontario have had confirmed cases.
- There is higher prevalence of infection and disease in southern USA due to environmental conditions that favour the survival of the tick that carries the micro-organism.
- Anaplasma central is a less pathogenic but closely related organism. It has never been reported in North America. The organism is used as a live vaccine for cattle in Israel, South Africa, South America and Australia (de la Fuente et al., 2005b).
- Anaplasma ovis, the agent of ovine anaplasmosis, may cause mild to severe disease in sheep, deer and goats but is not infectious for cattle.
How is Anaplasmosis Transmitted?
- Anaplasma marginale can be transmitted by three methods:
- Ticks are biological vectors of A. marginale and this is the most common route of transmission. Amplification of the infective organism occurs in the salivary glands of the ticks.
- Mechanical transmission occurs by direct inoculation of cattle with blood-contaminated hypodermic needles and surgical or dehorning instruments. Horseflies (Tabanids spp.) may also mechanically transmit the disease on their mouthparts after taking a blood meal from an infected animal.
- Transplacental transmission where infected erythrocytes from infected cows move across the placenta in the uterus to the fetus without amplification of A. marginale.
- In North America, A. marginale can be transmitted by the Dermacentor species of ticks, including the three-host ticks Dermacentor andersoni (Rocky Mountain wood tick), Dermacentor variabilis (American dog tick), Dermacentor occidentalis (Pacific Coast tick – not present in Canada), and the one-host tick Dermacentor albipictus (winter or moose tick).
- It seems that unmated male ticks retain infection longer than mated males and were infective from 63 to 232 days under simulated hibernation conditions (Anthony and Roby, 1966; Coan et al., 1989). Thus, male ticks may be potential reservoirs of infection for ruminants for extended periods (Kocan, 1995).
- Adult Rocky Mountain wood tick (D. andersoni) generally feed on larger mammals such as horses, cattle, moose, deer, mountain goat and elk (James et al., 2006). The tick is the predominant biological vector for genetic strains of A. marginale in the northwestern US (Scoles et al., 2005a). Its distribution in the USA was reported from western Nebraska and South Dakota, westwards to the Cascades and Sierra Nevada Mountains, and from northern New Mexico and Arizona, northwards into Canada.
- In Canada, D. andersoni has been reported from southern British Columbia eastwards into Alberta and extending into Saskatchewan. East of 105_ longitude, it is replaced by D. variabilis, the American dog tick (Wilkinson, 1967).
- Both D. andersoni (Rocky Mountain spotted tick) and D. variabilis (American Dog tick) are present in Alberta.
- Outbreaks of anaplasmosis are usually seasonal and occur during or immediately after the tick breeding season.
- Wildlife may also become infected with A. marginale. While they do not show signs of disease, they may act as a reservoir for the bacteria.
- The season of adult activity usually lasts from the beginning of March to end of April or mid-May in interior British Columbia, and reaches a peak in early April. East of the Rockies, the active period may extend well into June or even July (Gregson, 1956; Alvin Gajadhar, personal communication).
Clinical Signs of Anaplasmosis
- Cattle of all ages can become infected but severity of disease is age dependent with cattle less than a year old showing no or very mild clinical signs of the disease.
- At least 15% of the erythrocytes have to be parasitized before there is clinical disease (Radostits et al., 2007).
- Cattle between one and two years of age develop acute clinical disease manifested by fever, going off feed, rapid shallow breathing, reluctant to walk and pale mucous membranes but fatality is rare. Affected dairy cattle will also have a rapid decline in milk production.
- Cattle older than two years of age will develop acute clinical disease followed by sudden death. Often older animals will be found dead. Fatality rates can range from 29 to 49% in animals older than two years that have experienced clinical disease.
- Infected animals remain persistently infected carriers for life and are reservoirs for the organism in the herd. Current science indicates that short term treatment of infected cattle with tetracycline only temporarily eliminates the bacteria but does not eliminate the carrier state. In order to eliminate carrier state, long term treatment with tetracycline is required and this is expensive both in terms of the cost of the drug and discarded milk.
Samples for Diagnosing Anaplasmosis
- The presence of A. marginale may be confirmed in a sick animal by identifying the organism in stained blood smear from sick animal.
- Whole un-clotted blood and serum can be tested for the presence of the microorganism.
- Pathological examination of fresh and fixed tissues will assist in ruling out other causes of death.
- According to the manufacturer's information, the CELISA test used for testing has a sensitivity (Se) of 95% and a specificity (Sp) of 98% when used to identify persistently infected cattle at a cut-off point of 30% inhibition (%I) (VMRD, 1998).
Pathological Lesions of Anaplasmosis
Animals that have died due to anaplasmosis will show pale to yellow tinged (jaundice) mucous membranes, thin watery blood, enlarged soft spleen with prominent follicles, enlarged liver with yellow-orange discoloration, gall bladder distension with thick green-brown bile, brown hepatic and mediastinal lymph nodes, epicardial and pericardial petechial and ecchymotic hemorrhages. Hemoglobinuria is not a feature of anaplasmosis.
Other Diseases with similar clinical signs:
- Bacillary hemoglobinuria
- Chronic copper poisoning
- Any cause of hemolytic anemia, (for example: cold water intoxication, onion poisoning, postparturient hemoglobinuria)
- Grazing of Brassica sp. (canola, kale, turnips, cabbage)
Are Humans Susceptible?
Anaplasma marginale does not cause clinical disease in humans. Human anaplasmosis is caused by a related bacterium, Anaplasma phagocytophilum. A. phagocytophilum is also transmitted by bites from infected ticks. Black-legged ticks (Ixodes spp.), which are present in Alberta, are the primary vectors of A. phagocytophilum.
Anaplasma phagocytophilum is present worldwide (including USA) but seems to cause the disease called tick-borne fever in domestic and wild ruminants in Europe (Hoar et al., 2008).
What Countries Have Anaplasmosis?
The disease is common in tropical and sub-tropical regions of the world. Many southern states of United States, Australia, central and south America, Africa and southern Asia have such sub-tropical and tropical regions. Infection with A. marginale occurs only occasionally in temperate climate areas.