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Bovine bluetongue 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 sheep are most often exposed to bluetongue. This type of disease was first officially recorded in the South African region in 1876, and it was only in 1905 that the pathogen was identified.
What is bluetooth
In veterinary medicine, bluetongue in cows is also called sheep punitive fever. This virus is a vector-borne infection that affects both domestic and wild ruminants. This infectious disease is characterized by a febrile condition, inflammatory and necrotic lesions of the mucous membrane of the mouth and nose, the gastrointestinal tract, in addition, skeletal muscles in cattle are subject to deformation.
Causes of occurrence
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 infection 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 show, the main vector 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 initially directed at insects, and they are already transmitting the infection to susceptible cattle.
Most often, outbreaks of a fatal disease are recorded in areas where there are a large number of swamps, 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 primarily affects 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. For vector infection, the incubation period can be from 2 to 18 days. After this period of time, the first signs of the disease begin to appear in cattle.
Bluetongue can proceed differently in different individuals. 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 bluetongue disease:
- sharp;
- subacute;
- chronic;
- abortive.
The acute form is most indicative of the manifestation of signs of the disease. At first, a slight increase in body temperature can be observed - up to 42 ° C, provided that the temperature in an adult animal 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, you can observe strong salivation and profuse nasal discharge in animals with bluetongue, breathing is also difficult, wheezing is present.
Gradually, the lips, tongue and the area around the ears begin to swell.Hemorrhage appears in the mouth of cattle. All this leads to purulent inflammation and an unpleasant odor. The lips droop, a blue tongue protrudes from the mouth. The lethal outcome occurs due to the general weakness of the animal and the depletion 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 stable 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 (cattle fever) enters the bloodstream, the process of destruction of the endothelium begins, as a result of which the animal develops edema and hemorrhage. It is important to understand that clinical symptoms do not appear for a rather long time, as a result of which the incubation period from 1 month increases to 40 days. The process of tissue nutrition is disrupted, and necrotic decay occurs.
Given that this type of disease in cattle in most cases proceeds in a subclinical form, then 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 is necessary to understand that in this case the obtained research results will be as accurate as possible.
As practice shows, the most popular method is IF-analysis, with the help of which it is possible to 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 an animal has bluetongue. After the animal has been ill with the virus in the abortive stage, it acquires lifelong immunity from the virus, but 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 pretty much depleted;
- due to circulatory disorders, edema appears in the lower part of the animal's body;
- the mucous membranes become inflamed, which later turn blue;
- 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 tissue dies;
- the heart muscle increases quite strongly, 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;
- the skeleton, gastrointestinal tract is subjected to deformation.
In the acute course of an infectious disease, a fever can be observed in an 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 more heavily and subsequently dies.
Preventive actions
As a rule, infected animals are sent for slaughter and further disposal. In the event that an individual is of particular value or is a breeding one, then it is preserved.For 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. It is forbidden to graze a sick animal. 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 disadvantaged 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 the insects must be destroyed using insecticides. Animals need to be vaccinated in a timely manner and timely diagnosed for the presence of the virus.
Conclusion
Bovine bluetongue has a high mortality rate. If we consider stationary foci, then the mortality rate is about 10-30%. In new places, upon detection of an infectious disease, the death of livestock can exceed 90%. It is for this reason that it is recommended to carry out preventive measures in a timely manner and fight the dangerous virus. The use of the vaccine allows you to protect the animal's body for 12 months (vaccination is carried out annually). If an animal has an abortive bluetongue, then lifelong immunity is developed.
