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Bluetongue in cattle is an infectious disease caused by a virus. This type of disease is popularly called blue tongue or punitive sheep fever. This is due to the fact that bluetongue is most often exposed to sheep. This type of disease was first officially recorded in the South African region in 1876, and only in 1905 was it possible to identify the pathogen.
What is bluetongue
In veterinary medicine, bluetongue in cows is also called sheep punitive fever. This virus is a vector-borne infection affecting both domestic and wild ruminants. This infectious disease is characterized by a feverish condition, inflammatory and necrotic lesions of the mucous membrane of the mouth and nose, gastrointestinal tract, in addition, skeletal muscles in cattle undergo deformation.
Causes
The bluetongue virus is found in the blood, plasma, serum and internal organs of sick cattle. As a rule, this type of pathogen can be transmitted from an infected animal to a healthy individual through blood-sucking insects.
Bluetongue disease is a seasonal infection. It is important to consider that the disease coincides with the period when insects show the highest level of activity. As practice and research shows, the main carrier of the pathogen is woodlice, which is widespread.
In addition, mosquitoes and mosquitoes can spread this virus. Migratory birds are considered an intermediate link. This is due to the fact that the transmission of the virus is directed first to insects, and they already transmit the infection to susceptible cattle.
Most often, outbreaks of a deadly disease are recorded in areas where there are a large number of swamps, quite a lot of precipitation falls, and there are areas where stagnant water is observed. In addition, it should be borne in mind that this disease is primarily affected by those animals that have an inadequate diet, as well as if they suffer from worms and other infections.
Symptoms of bluetongue in cattle
If the infection occurred naturally (from mother to fetus through the placenta), then the incubation period in cattle can last up to 7 days. When infected from a vector, the incubation period can last from 2 to 18 days. After this period of time, the first signs of the disease in cattle begin to appear.
Bluetongue can occur in different individuals in different ways. It all depends on the amount of the virus that has entered the body, the state of the immune system. There are the following forms of the course of the disease of bluetongue:
- acute;
- subacute;
- chronic;
- abortive.
The acute form is the most indicative in the manifestation of signs of the disease. Initially, a slight increase in body temperature can be observed – up to 42 ° C, provided that in an adult animal the temperature is considered normal in the range from 35,5 ° C to 40 ° C.
For 24-48 hours, inflammation of the mucous membrane of the mouth and nose occurs. In this case, one can observe strong salivation and copious discharge from the nose in animals with bluetongue, breathing is also difficult, wheezing is present.
Gradually, the lips, tongue and area around the ears begin to swell. Hemorrhage appears in the oral cavity of cattle. All this leads to purulent inflammation and an unpleasant odor. The lips hang down, a blue tongue protrudes from the mouth. The lethal outcome occurs due to the general weakness of the animal and the exhaustion of the body.
Subacute and chronic forms of bluetongue develop in a similar way, only the symptoms are much less pronounced. As practice shows, the abortive form of bluetongue in cattle proceeds without symptoms, in most cases self-healing occurs. After recovery, the animal remains a carrier of the virus for some time, subsequently a strong immunity is developed.
Diagnostics
After the infection has entered the body of cattle, the process of penetration of the virus into the blood cells located on the inner surface of the blood vessels begins. At the moment when the causative agent of bluetongue (bovine fever) enters the bloodstream, the process of destruction of the endothelium begins, as a result of which edema appears in the animal and hemorrhage occurs. It is important to understand that clinical symptoms do not appear for quite a long time, as a result of which the incubation period from the 1st month increases to 40 days. The process of tissue nutrition is disturbed, necrotic decay occurs.
Given that this type of disease in cattle in most cases occurs in a subclinical form, it is not always possible to resort to the use of clinical methods for diagnosis. In order to identify bluetongue, one has to resort to the use of serological methods. PCR is used much less often, but it must be understood that in this case the results of the study will be as accurate as possible.
As practice shows, the most popular method is the IF analysis, with which you can accurately determine whether there are antibodies in the animal’s body. In addition, it is important that the presence of antibodies is not a sign that the animal has bluetongue. After the animal has been ill with the virus in the abortive stage, it acquires lifelong immunity from the virus, but the antibodies are in the body for a long time. Thus, IF analysis is not recommended for detecting the virus in areas where the disease is widespread.
Bluetongue prognosis in cows
With bluetongue in cattle, the following pathological changes are observed:
- the body is quite depleted;
- due to circulatory disorders, edema appears in the lower part of the animal’s body;
- the mucous membranes become inflamed, which later acquire a blue color;
- the tongue increases, falls out of the mouth, becomes a blue tint;
- ulcers and erosion can be seen on the gums and on the inside of the cheeks;
- on the muscular skeletal part, a large number of foci appear in which the tissue dies;
- the heart muscle increases quite a lot, after which it acquires a loose structure;
- there are significant changes in the structure of internal organs;
- often together with bluetongue, dropsy can be found in cattle;
- undergoes deformation of the skeleton, gastrointestinal tract.
In the acute course of an infectious disease, a fever can be observed in the animal, which can last from 1 day to 1 week. If there is no fever during the disease, then the individual suffers the disease much harder and subsequently dies.
Preventive measures
As a rule, infected animals are sent for slaughter and further disposal. In the event that an individual is of particular value or is tribal, then it is preserved. To do this, the animal is placed in an isolated room and special conditions are created with improved feeding.
In such situations, they resort to symptomatic therapy, which is aimed at improving the general condition. Grazing a sick animal is prohibited. This is due to the fact that ultraviolet rays only aggravate the general situation.
During the fight against the disease, it is necessary to adhere to quarantine when importing animals to the farm. As a rule, quarantine should last for one month. It is not recommended to import cattle from unfavorable regions.
If an infectious outbreak has been recorded, then it is worth stopping grazing in the evening. If there are swamps in the immediate vicinity, they must be dried and insecticides should be used to destroy insects. Animals need to be vaccinated and timely diagnosed for the presence of the virus.
Conclusion
Bluetongue in cattle is characterized by a high mortality rate. If we consider stationary foci, then mortality is about 10-30%. In new places, if an infectious disease is detected, the loss of livestock can exceed 90%. It is for this reason that it is recommended to take preventive measures in a timely manner and fight against a dangerous virus. The use of the vaccine allows you to protect the body of the animal for 12 months (vaccination is carried out annually). If an animal has an abortive form of bluetongue, lifelong immunity is developed.
