Veterinary Division - Animal Health Programs
If you own cattle in North Carolina, this publication will assist you in maintaining the health and productivity of your cattle. The intent of this pamphlet is to make cattle owners aware of this potentially severe infectious disease.
What is Anaplasmosis? Anaplasmosis is an infectious disease of cattle, sheep and goats. The disease can be acute or chronic in nature. Most commonly, animals with anaplasmosis show signs such as fever, anemia (pale gums), and jaundice (yellowing of the linings of the mouth and nose and yellowing of the whites of the eyes). Infection is more common in beef cattle than it is in dairy cattle. Anaplasmosis does not infect humans.
What causes Anaplasmosis in cattle? Anaplasmosis is caused by the organism "Anaplasma marginale." This organism is a member of the Rickettsia family of disease-causing agents. Anaplasmosis is spread by the bite of the common horsefly, other biting insects, or any instrument which can transmit blood.
Are cattle in all parts of North Carolina affected? This disease is found worldwide and in the United States is most common in the southeastern, gulf coast, lower plains, and western states. From historical information and laboratory testing, the central and eastern parts of North Carolina have the highest rates of anaplasmosis infected cattle within the state.
I have never had a problem with Anaplasmosis, will I have one in the future? Although it is difficult to estimate the probability of an anaplasmosis problem in a particular herd or area, the incidence of clinical cases appears to be increasing in North Carolina. Experience in other parts of the country suggests that the occurrence of anaplasmosis in an area is cyclical and peaks every 5-7 years.
What is the cost of this disease if I get it in my herd? Research from Texas and California suggests that the costs of a clinical case of anaplasmosis average over $400 per animal. Research shows that if anaplasmosis infects a previously uninfected herd, the following effects are expected: calf crop reduced by 3.6%, 30% increase in cull rate, and 30% of the adults showing signs will die.
What do I do if I suspect Anaplasmosis in my cattle? A practicing veterinarian with experience in cattle diseases and production should be consulted immediately. The state offers technical support for herds with this problem.
How do I prevent Anaplasmosis? As with many cattle diseases, prevention is the key to disease control. Minimizing horsefly and tick populations, cleaning surgical instruments, and professional advice are the key to prevention of this disease. Add only known anaplasmosis negative cattle to negative herds.
Can I vaccinate against this disease? There is a commonly available vaccine. This vaccine does have some severe side effects and is not routinely recommended for use by cattlemen. Currently, a state permit is required prior to its use in North Carolina. An experimental vaccine is being developed and could be a viable option in the future.
If I buy cattle from other states, can they bring Anaplasmosis into my herd? With the current regulations within North Carolina and in other parts of the country, it is possible to buy cattle that are carriers of anaplasmosis. Buying only anaplasmosis negative cattle from known negative sources is the best means of preventing anaplasmosis positive cattle from entering your negative herd.
Will my herd be quarantined if Anaplasmosis is suspected? As of April 1990, there is no quarantine status for confirmed anaplasmosis herds in North Carolina. The North Carolina Department of Agriculture and Consumer Services does offer technical support for herds with an anaplasmosis problem.
Definition Anaplasmosis is an infectious disease of cattle that affects the red blood cells. Affected red blood cells are removed from circulation causing fever and severe anemia. Other signs such as jaundice (yellowish discoloration of linings of mouth and nose and the whites of the eyes) will follow the signs of anemia. Animals affected with this disease may exhibit severe signs or more subtle signs such as sudden onset of weight loss and failure to perform over a longer period of time. Anaplasmosis has been present in the United States for a number of years and appears to be on the increase in North Carolina. Cattle owners should be aware of this disease because of the potential of economic and production losses.
Prevalence Anaplasmosis is an important pathogen to cattle worldwide and is present in tropical, subtropical, and temperate areas. In the United States, anaplasmosis has been reported in all of the continental states. The southeastern states (including North Carolina), gulf coast states, lower plains, and western states have the highest levels of disease. Previous estimates have assessed the national annual loss for cattle owners to be in excess of $100 million. Research has shown that each clinical case of anaplasmosis costs cattle owners an average of $424. These costs include reduced performance of infected animals, cost of diagnosis and treatment, and the 30% chance that affected animals will die.
During a test period in 1989, samples from 1,183 N.C. cattle were presented for anaplasmosis testing at Rollins Disease Diagnostic Laboratory. Of the cattle tested, 44 (3.7%) were positive for anaplasmosis. More positive animals in a much wider range of counties were detected than anticipated, including the Piedmont areas of the state.
Causative Agent Anaplasmosis is caused by the blood parasite Anaplasma marginale. This organism damages red blood cells and is seen microscopically as blue-black dots on the cellular margins of stained blood cells. The parasite does not rupture the red blood cells, but the cells are changed enough for the body to recognize them as damaged. Damaged cells are removed from circulation by the spleen.
Transmission Anaplasmosis is spread in the blood of infected animals. The disease is not spread directly between animals but can be transmitted via blood from an infected animal to a susceptible animal. It can be transmitted directly by ticks, horseflies, mosquitoes, and probably other biting insects. It may also be spread by mechanical means such as needles, surgical instruments, and dehorning equipment. Blood stained instruments subsequently used on non-infected, susceptible animals, will spread the disease. Clinical disease is more commonly seen during the height of the horsefly and tick season. However, some cases may be observed year round due to milder temperatures or mechanical spread.
Clinical Signs and Symptoms While anaplasmosis can affect any age or breed of cattle, the severity of signs varies according to the age when infected and the infective dose of organism. Adult cattle are the most severely affected and show the following signs:
- Depression, lethargy and loss of appetite
- Fever, muscle tremors and weakness
- Pale gums, dry muzzle and labored breathing
The urine will not look blood-colored. This finding can be used to separate anaplasmosis from other diseases with similar clinical signs. Due to the severe anemia associated with this condition, any stress, such as moving or handling, can cause some animals to get very restless, over-excited and possibly die. In these animals, abnormal aggressiveness and other furious behavior may occur. Death in affected adults ranges from 20-50%.
Young calves (up to 1 year) usually have only mild clinical signs with little or no death loss. Most commonly affected calves show the following signs:
- Slight depression for a few days
- Recovery without treatment
- Reduced potential for future infection
Although not clinically apparent, the disease can cause a permanent loss in growth potential.
Stages of Disease The disease can be divided into four different stages: incubation, developmental, convalescent, and carrier according to parasite appearance in the blood and clinical signs.
The incubation stage is the time from the initial introduction of Anaplasma until one percent of the red blood cells are infected. This period lasts between three to eight weeks depending on the infecting dose of Anaplasma. The incubation period ends with the first increase in body temperature. There are no clinical signs seen except maybe mild depression.
The developmental stage begins when the first signs of anemia and other associated clinical signs can be seen. The infected animals will show clinical signs about 4 to 5 days into this stage. The producer will notice weight loss and , if lactating, a rapid fall in milk production. The fever may go as high as 104-106 degrees Fahrenheit. As the disease develops, the anemia worsens as more red cells are affected. A marked icterus will develop (yellowing of the eyes, mucous membranes, and skin) and the animal may have significant production losses during the course of the disease. In severe cases, death may follow in a few days.
The convalescent stage begins with the appearance of immature red blood cells in the blood stream. This stage ends when the majority of red blood cells are normal again. Animals surviving to this stage may e unthrifty and may never produce at their original potential. The recovery may take from a few weeks to a few months.
The carrier stage is that time from the disappearance of Anaplasma in the blood until the animal's death. Carrier animals harbor the parasite in their blood, but the parasite can not be seen under the microscope. The two important aspects of the carrier stage are that carriers remain infective to their herdmates, and specialized laboratory tests are necessary to detect carrier animals.
Diagnosis The diagnosis of anaplasmosis is based on the typical clinical signs such as fever and severe anemia along with the appearance of the organism in a stained blood smear (microscope examination). Anaplasma bodies are detected during the developmental and convalescent stages of the disease. The carrier stage of disease can be diagnosed by a test called the complement fixation test. If this test is positive, the animal has had anaplasmosis and has mounted an immune response. The complement fixation test will also be positive in the developmental and convalescent stages. Disease management The management of the herd with anaplasmosis can e both expensive and time consuming. Methods for control include the use of feed grade or injectable antibiotics at high levels for extended treatment periods. Drug withdrawal times for both meat and milk must be considered. A licensed veterinarian knowledgeable about this disease should be consulted for the best method of disease control and management.
Practical Preventative Measures Due to the expense of disease control, prevention of this disease will prevent potentially significant economic losses. There are several prevention steps that will greatly reduce the opportunity for anaplasmosis to cause problems.
VECTOR CONTROL: Employ effective insect control such as eartags, fly blocks, sprays, etc. at regular intervals to control flies and other biting insects. Manure management is also important to decrease insect populations. STERILIZE SURGICAL INSTRUMENTS: Dehorners, castration equipment, and needles should be cleaned by hot water and disinfection between each animal to remove any traces of blood.
PROFESSIONAL ADVICE: Talk to your veterinarian about the use of medicated feeds and other control measures during the vector season. Careful consideration must be made in order to achieve the maximum benefits from the cost of control measures.
VACCINES: Anaplasmosis vaccine can reduce the death losses in a herd and decrease the severity of the clinical signs. Major drawbacks to the use of the vaccine are: 1) the high potential for adverse side effects or death in vaccinated calves and, 2) the inability to differentiate infected animals from vaccinated animals. Prior approval from the State Veterinarian's Office is required for use in North Carolina. Most producers have chosen not to request vaccine use.
Control Policy As of April 1990, the North Carolina Department of Agriculture and Consumer Services has revised the procedures for control of anaplasmosis. The diagnosis of anaplasmosis requires that blood samples be submitted to the state diagnostic laboratory. Upon confirmation that a herd test is positive, the following steps will be taken:
- Tests results are sent to the herd owner, area veterinary medical officer, and to the attending veterinarian
- Herd test agreement is sent to the herd owner and area veterinary medical officer
- Herd owner is contacted by the veterinary medical officer
- The veterinary medical officer will advise the herd owner of a positive test, advise of state policy, answer questions regarding the herd test agreement, and answer further questions regarding this disease.
Anaplasmosis is still a reportable disease in North Carolina. The State Veterinarian's Office must be notified when the disease is diagnosed.
Herd Test Agreement The state of North Carolina offers an initial herd test at state expense. The herd test is intended to offer the herd owner beneficial diagnostic information for control of an anaplasmosis problem. To qualify for an initial herd test at state expense, the owner must sign a herd agreement. This agreement is intended to minimize the spread of the disease to other herds. Enrollment is voluntary and the herd owner must agree to the following points:
- Provide the necessary personnel to restrain animals for testing
- Permanent identification of all cattle
- Treat all reactors or sell for immediate slaughter
- Further testing or treatment would be conducted by a veterinary practitioner at the owner's expense
Blood DC and Radostits OM, ed. Herd Health. Philadelphia: W.B. Saunders Company, 1985, 875-878.
Richey, E.J., Bovine Anaplasmosis. In: Howard JL, ed. Current Veterinary Therapy. 2nd ed. Philadelphia: W.B. Saunders Company, 1986; 622-626.
Goodger, W.J., Carpenter MS and Riemann H. Estimation of Economic Loss Associated with Anaplasmosis in California Beef Cattle. Journal of the American Veterinary Medical Association 1979; 174: 1333-1336.
Alderink, F.J. and Dietrich, R.A. Economic and Epidemiological Implications of Anaplasmosis in Texas Cattle Herds, in Proceedings. 86th Annual Meeting of the United States Animal Health Association 1982; 66-75.
The author thanks Drs. Tom McGinn and George Edwards of the Department of Agriculture and Consumer Services, Veterinary Division and Drs. Tim Jordan and Roger McCraw of North Carolina State University for their assistance in the preparation of this pamphlet.