| | What is Bluetongue?
Bluetongue is an insect-borne viral disease that can affect all ruminants; cattle are the natural reservoirs of the virus. There are 21 different strains of Bluetongue that have been identified. In Canada, Type 11 Bluetongue virus was isolated in 1987 and 1988 in the Okanagan Valley of British Columbia.
What causes Bluetongue?
Bluetongue is caused by reoviruses. A specific type of gnat transmits the viruses. The gnats take blood from an infected animal and spread the disease to other cattle when they take additional blood meals. Following an infection in cattle, the virus incubates for 3 to 10 days, and may remains active in the blood for 60 to 80 days. During this active phase, red blood cells of the infected animal are destroyed, and the disease can be transmitted to other animals. Red blood cells in the blood of sheep and wild ruminants have a shorter lifespan than in cattle, thus decreasing the time that the blood is infected.
What are the signs and symptoms of Bluetongue?
Cattle infected with bluetongue cannot have a confirmed diagnosis without laboratory testing. Clinical signs that appear are in an infected animal can be common to many diseases or nutritional problems. Some of these signs include:
- Abortion, infertility, and stillbirths.
- Congenital defects with weak or dummy calves, deformed legs and feet, blind, white-eye, overshot lower jaw etc.
- Persistently infected cattle that are infected with one strain of bluetongue will not show signs until infected with another strain. At this point in time, ulcers of the mouth, nose and udder, lameness with inflammation on the top of the hoof, hoof crack, hair loss, and a swollen protruding tongue can appear.
Symptoms are much more visible in sheep, but it is critical to obtain conformation from a blood sample submitted for laboratory analysis. Unfortunately, an animal that tests negative for bluetongue, that is not infected by the disease, but may still be able to carry the virus.
Can Bluetongue be transferred from animal to animal?
Yes bluetongue can be transferred from animal to animal. A cow can pass on the infection to the calf in utero. The fetus is most susceptible at 60 to 140 days of pregnancy. Infected semen can infect a cow resulting in the disease being transferred to the cow and then to the calf.
Is there a time of year when Bluetongue is most often present?
Bluetongue is a seasonal disease, but cattle can carry the virus over the winter months. Typically, the disease is present from midsummer until shortly after the first hard frost. The vector (gnat) that spreads the disease is active during this period. In areas like the southern United States with milder climates the gnats can be active year round.
Can Bluetongue be prevented?
Currently there is no vaccine available to protect cattle from bluetongue in cattle. There is one vaccine available for type 10 in sheep. Controlling gnat populations by draining stagnant pools of water, debris filled water areas, and applying insecticides in areas that cannot be drained help. In warmer climates and in certain situations, housing cattle during the day can be beneficial, as the insects tend to feed primarily in the early morning and the evening.
What is Anaplasmosis?
Anaplasmosis is a form of ‘tick fever’ in cattle, it is also known as yellow bag or yellow fever. It is an infectious disease of cattle that infects cattle’s red blood cells.
What causes Anaplasmosis?
A microorganism, Anaplasma marginale, causes the disease. This parasite infects the red blood cells and causes sever anemia. Ticks that bite infected cattle spread the disease to non-infected animals, transferring the parasite from infected to susceptible animals. Using contaminated syringes, or by blood transfer between animals with unclean equipment when dehorning or pregnancy checking (same glove for many animals) can also transmit the disease.
What are the signs and symptoms of Anaplasmosis?
Severe anemia, weakness, fevers, loss of appetite, depression, constipation, decrease milk production, jaundice, abortion and death can occur. Calves rarely become infected or show symptoms but can be carriers of the disease. The disease is rarely fatal in cattle up to 2 years of age, but can be is fatal in animals up to 3 years of age and is often fatal in older cattle.
In what countries is Anaplasmosis found?
Currently no cases of anaplasmosis have been found in Canada. The disease commonly occurs in Africa, the Middle East, Asia, Australia, the United States, Central and South America and Southern Europe.
Can Anaplasmosis be prevented?
At present there is only one commercially available vaccine against anaplasmosis in the United States, but it will not prevent the disease, it will only reduce death loss.
Prepared by Nanita Blomquist, Alberta Ag-Info Centre, Alberta Agriculture and Rural Development |
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