Classical swine fever
One of the most dangerous infectious diseases of pigs that can cause huge material damage to the farm is the plague. The disease is characterized by rapid spread, a huge number of infected individuals in the population and a very high mortality rate. Read more about this disease later in the article.
Species of plague in pigs
The swine fever virus has the ability to mutate, so new strains periodically arise. However, there are 2 of the most famous and widespread species: classical swine fever (CoES) and African (ASF).
Did you know? Although the disease characteristic of humans and pigs is called the same - the plague, these are two completely different diseases. The plague, which is dangerous for people, is caused by infection, and the cause of CoES and ASF is the virus. But both the human and the pig species of the disease have common features - high contagiousness and mortality.
This form of the disease, affecting both domestic and wild pigs (wild boars), is transmitted mainly through the vital products of infected animals (feces, saliva, all kinds of secretions). There are frequent cases of a hidden course of the disease, without pronounced signs. It also happens that in animals that have undergone the disease, it becomes chronic with a slow course and unexpressed symptoms.
At the beginning of the 20th century, a new virus (Asfivirus) was discovered, which belongs to amphoviruses and is the causative agent of African swine fever. Symptoms of both forms have many common details, but the African form is much more likely to be fatal. Livestock deaths can reach 99-100%. Due to the swiftness of the course of the disease, even a large herd can completely die in a few days. For a long time, the African plague proceeded only in an acute form, and now there is a chronic one.
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There are animals that only carry the infection, but this form of the course of the disease is not found as often as in the case of classical swine fever. The birthplace of ASF, as the name implies, is Africa, or rather, its equatorial regions. But largely thanks to the development of world trade, and, accordingly, communications (especially shipping), the African plague has become a frequent guest in Europe.
Features and dangers of classical swine fever
The danger of this disease lies in several factors, among which the following can be distinguished:
- It affects both piglets and adults;
- transmitted by almost all known methods;
- spreads very quickly inside the stock;
- not amenable to effective treatment;
- very often, CoES is accompanied by complications (pneumonia, intestinal and pulmonary forms, hemorrhagic diathesis), which practically leaves no chance for livestock to survive;
- if you do not notice one sick individual in time, in the shortest possible time you can lose the whole population;
- the virus is very resistant to aggressive environments, persists for a long time, is not afraid of freezing, has the ability to mutate;
- some sick individuals in whom the disease proceeded secretly, asymptomatically, can become the spread of the disease, thereby threatening the entire population;
- causing enormous economic damage to farmers.
Important! CoES virus has 3 types. Type "A" is the cause of the acute form of the disease. Type "B" causes chronic and other forms. And type "C" is an unstable strain, used for the manufacture of a vaccine.
The main source of the disease is sick animals or carriers of the disease. Any discharge of such pigs into the environment carries the virus. An animal can become infected through the esophagus, by airborne droplets (respiratory organs), through microranes in the skin.
- carcasses of animals slaughtered due to illness;
- all kinds of wastes of meat production (offal), not subjected to proper treatment;
- water, feed;
- farm equipment;
- wardrobe items of personnel accidentally in contact with the source of infection;
- wild animals and birds.
In the event that after a past illness the pig survives, it develops immunity to reinfection. Thanks to such animals, experts have developed vaccines against plague. One of these vaccines is "KS", its use contributes to the development of immunity in the animal for a period of more than 1 year. Piglets are given a vaccine with food and water shortly after birth - this increases their resistance to viral attacks.
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Danger to humans
It is believed that both the classical and African forms of the plague are not dangerous to humans. However, due to the fact that the causative agent of the disease is poorly understood, the meat of such animals is undesirable to eat.
CoES causative agent
The causative agent of classical swine fever, as mentioned above, is an RNA-containing togavirus. This virus is resistant to adverse conditions (freezing, lack of water). In frozen meat, it can remain viable for several years. At a temperature of 75-80 ° C - dies in an hour.
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Ultraviolet from direct rays of the sun is able to destroy the causative agent of CoES on the open ground within 10-15 days. In a dehydrated state on the territory of infected yards or farms, the virus remains dangerous for 1 year.
Signs and Symptoms
The incubation period of CoES lasts from 1 to 9 days. Further, the plague can develop into one of 6 forms, the symptoms of which should be discussed separately.
The following symptoms are characteristic:
- constipation or irregular bowel movements (periodically), during breaks - diarrhea;
- the animal stops eating.
Did you know? In Russia, more than 500 outbreaks of ASF were recorded, and a population of more than 1 million individuals was destroyed. Economic damage exceeds 30 billion rubles.
Inherent typical symptoms:
- pneumonia develops;
- the animal breathes with difficulty;
- discharge from the nose;
- gilts to reduce pain sit down like a dog, tucking their hind limbs under themselves and stooping.
It is typical for farms where the livestock is vaccinated, but the conditions of detention and food do not comply with the instructions and norms of SES. The weakest animals begin to hurt first, then the virus spreads to other individuals. Usually the disease lasts up to 8-9 weeks.
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Symptoms are as follows:
- the pig periodically loses interest in food;
- inflammation on the skin;
- the animal loses much weight.
For the acute form of CoES, the following symptoms are characteristic:
- body temperature rises to 41-42 ° C;
- 50-70 hours after the onset of the first symptoms, the animal loses its appetite;
- constant thirst;
- fever and vomiting;
- alternating diarrhea with blood and constipation;
- swelling of the eyelids, conjunctivitis, while the eyes are very festering;
- the animal is noticeably slouching, trying to hide behind a litter;
- paresis of the hind limbs;
- urine color is dark;
- blisters appear on the body, filled with yellow mucus;
- spots on the skin of a dark red color, which increase in size and gradually merge into one large spot;
- blood is periodically released from the nose (patch);
- ears, patch and tail acquire a purple hue;
- immediately before death, the body temperature drops sharply to 35-36 ° C.
The acute form of CSF in young animals lasts 1-1.5 weeks. Sows bring dead offspring.
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Lightning fast form
This form of the disease is characteristic of piglets feeding breast milk.
The manifestations of the disease are as follows:
- depressed state;
The subacid form, in turn, can occur in 2 subspecies:
- intestinal form;
In pigs killed as a result of the disease, you can see the following characteristic signs:
- The skin is covered with a large number of hemorrhages, of various shapes and sizes.
- The enlarged lymph nodes of burgundy color, at the opening, have a marble-like structure.
- Spots on the lungs.
- The heart is covered with hemorrhages.
- Enlarged spleen, covered with tears along the edges. This fact is the most typical sign of CoES.
- The kidneys have a whitish hue with noticeable traces of small hemorrhages.
- In the event that the death occurred in the subacute phase, you can see typical "plague buds".
Possible complications of the viral process
In addition to the danger posed directly by CoES, it should be said about the complications that may arise as a result of the disease. First of all, among possible complications, it is necessary to distinguish both forms (intestinal and pulmonary) of the subacid variety of the disease.
Did you know? Mortality of classical swine fever is 80-100% of the total number of ill individuals.
In addition, complications can manifest themselves in the form of salmonellosis and pasteurellosis that additionally occurred against the background of the plague. All 3 diseases lead to a fairly quick death.
Diagnosis of the disease
When establishing a diagnosis of CSF, a significant role is played by such indicators as depression, lethargy, weakness, complete or partial refusal of food, and hyperthermia. But the fact is that these clinical signs may accompany other diseases, such as African plague. An accurate diagnosis can only be made as a result of a comprehensive study, which includes biological, clinical, episo-lethological analyzes.
General preventive measures
The main objective of preventive measures is to prevent the penetration of the virus into places of pigs.
To do this, you must follow these rules:
- The farm should be well-fenced, it is unacceptable to get wild animals there.
- It is necessary to equip disinfection at the entrance, including a rug with an antiseptic and a sanitary inspection room.
- Mandatory overalls for farm workers.
- It is unacceptable even temporary holding pigs outside the walls of the farm, in the private farms of personnel (for example, during disinfection work).
- It is necessary to develop and strictly implement measures for the disinfection, destruction of insect parasites and rats.
- Regularly disinfect all equipment and vehicles.
- Pigs that have just arrived on the farm must first be quarantined.
- Mandatory disinfection of water and heat treatment of food waste.
The most effective measure for preventing CSF is vaccination, which can be standard or with a concentrate. In one ampoule of a standard vaccine contains 1 thousand doses, in a concentrate - 1 million.
A standard vaccine is used as follows: put an injection in the lower third of the neck (possibly in the inner thigh) in a volume of 2 ml.
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In the event that the sanitary and epidemiological situation in the economy is normal, vaccination is carried out in the following order:
- Sows are immunized 2–3 weeks before each mating.
- Boars are vaccinated once a year.
- Piglets are vaccinated for the first time at the age of about 1.5 months, re-vaccinated at 3 months.
Concentrated Vaccine Use
The concentrate is used in large livestock complexes in case of an epidemic threat. All animals are vaccinated with no clinical signs. The procedure for immunization is the same as with a standard vaccine. Pregnant sows are also vaccinated a month before farrowing. Immunization is carried out until absolutely no signs of the disease remain on the farm.
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In farms where there is a violation of sanitary and epidemiological requirements, vaccination often causes the death of infected animals during the incubation period. But in this case, a healthy livestock remains alive. Even on farms that fully comply with the SES requirements, after vaccination, one can often observe post-vaccination fever in young animals with hyperthermia (up to + 41 ° C). In the event that the pigs feed normally and a depressed state is not observed, after 50-70 hours their health status will normalize.
Infection control methods
Among the modern methods of controlling CSF, hyperimmune serums should be noted, with the help of which piglets are treated in the early stages of the disease. The success of treatment depends on how early the disease was detected and, accordingly, measures were taken. Today, there are veterinary drugs that give fairly good results in the treatment of CSF, but, again, their effectiveness is directly proportional to the stage at which the disease was diagnosed.
As mentioned above, now sick animals are not treated, so the only truly effective means is immunization. A comprehensive vaccine against plague, erysipelas, and infectious meningoencephalitis has proven fairly well. The adult population is vaccinated once every 10 months, the piglets are vaccinated (2 ml) on the 50th day of life, and then after another 25 days.
Important! The most important condition for an effective and safe vaccination against CSF: the vaccine must be used in the first 3-4 hours after preparation.
To reduce the risk of an outbreak of CoES, both in private farms and large livestock enterprises, it is necessary to observe sanitary and hygienic standards, carry out regular disinfection, control newly arrived livestock, and, of course, vaccination is mandatory. Although CoES is not treated, and the livestock cannot be completely protected from the disease, observing the above rules can minimize the risk of infection.