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Quite recently, a new disease has appeared - African swine fever - literally destroying all private pig farming in the bud. Due to the very high contagiousness of this virus, veterinary services are forced to destroy not only the sick livestock, but also all healthy pigs in the area, including wild boars.
Origin of the disease
African swine fever virus (ASF) is a naturally occurring disease affecting wild pigs in Africa. The ASF virus remained there until the beginning of the twentieth century, when white colonists decided to bring European domestic pigs to the African continent. The “natives” of Africa, in the process of evolution, adapted to the African swine fever virus. In their case, the ASF virus persisted in a chronic form within the family herd. This virus did not cause much harm to warthogs, brush-eared pigs and large forest pigs.
Everything changed with the appearance on the African continent of the European domestic pig, descended from the wild boar. It turned out that European representatives of the pig family have zero resistance to the ASF virus. And the virus itself has the ability to spread quickly.
The ASF virus was first isolated in 1903.And already in 1957, the victorious march of the virus across Europe began. The countries located near Africa were the first to be hit: Portugal (1957) and Spain (1960). It turned out that in European pigs, African swine fever, instead of chronic, takes an acute course with a 100% fatal outcome if clinical signs appear.
What is the danger of African swine fever?
If we approach it from the point of view of the danger of the ASF virus to humans, African swine fever is completely safe. The meat of sick pigs can be safely eaten. But it is in this safety for people that the serious danger of the ASF virus for the economy lies. And this is due to the fact that you can spread the virus without knowing it. The ASF virus, which is not dangerous to humans, causes enormous losses in the pig industry. At the beginning of the victorious march of the African swine fever virus, the following people suffered from it:
- Malta (1978) – $29.5 million;
- Dominican Republic (1978-1979) - about 60 million dollars;
- Cote d'Ivoire (1996) – $32 million
On the Maltese archipelago, a total destruction of the pig population was carried out, since due to the size of the islands it was not possible to introduce quarantine zones. The result of the epizootic was a ban on keeping pigs in private homes. The fine for each individual found is 5 thousand euros. Only entrepreneurs breed pigs on specially equipped farms.
Distribution routes
In the wild, the spreaders of the ASF virus are blood-sucking ticks of the Ornithodoros species and wild African pigs themselves.Due to their resistance to the virus, wild African pigs can act as carriers when they come into contact with domestic pigs. “Africans” can be sick for several months, but release the ASF virus into the environment only 30 days after infection. After 2 months after infection, the active ASF virus is contained only in the lymph nodes. And infection with the causative agent of African swine fever can only occur through direct contact of a sick animal with a healthy one. Or by transmitting the virus by ticks.
In the conditions of pig farms and private farms, everything happens differently. In soil contaminated with feces, the virus remains active for more than 100 days. The same applies directly to manure and chilled meat. In traditional pork products - ham and corned beef - the virus is active for up to 300 days. In frozen meat it lasts up to 15 years.
The virus is released into the environment through feces and mucus from the eyes, mouth and nose of sick pigs. On walls, equipment, boards, etc., the virus remains active for up to 180 days.
Healthy pigs become infected through contact with infected animals and their carcasses. The virus is also transmitted through feed (it is considered especially profitable to feed pigs with waste from catering establishments), water, transport, and equipment. If all this is contaminated with the feces of swine plague, healthy people are guaranteed infection.
Since the virus is not dangerous to humans, if signs of African swine fever appear, it is more profitable not to notify the veterinary service, but to quickly slaughter the pigs and sell the meat and lard. This is where the real danger of the disease lies.It is unknown where the food will end up after being sold and where the next time the plague will break out due to the fact that an uneaten piece of contaminated salted lard was fed to pigs.
ASF symptoms
The signs of African swine fever and erysipelas in pigs are very similar and laboratory testing is required for accurate diagnosis. This is another reason why eradicating ASF outbreaks is very difficult. Proving to a pig farmer that his animals have ASF and not erysipelas is very problematic.
For the same reason, there are no videos showing signs of African swine fever. No one wants to attract the attention of the veterinary service to their farm. You can only find a video with a verbal story about the signs of ASF in pigs. One of these videos is presented below.
As in the case of erysipelas, the form of ASF is:
- lightning fast (super acute). The development of the disease occurs very quickly, without the appearance of external signs. Animals die within 1-2 days;
- acute. Temperature 42°C, refusal to feed, paralysis of the hind legs, vomiting, shortness of breath. Difference from erysipelas: bloody diarrhea, cough, purulent discharge not only from the eyes, but also from the nose. Red spots appear on the skin. Before death, falling into a coma;
- adjust Symptoms are similar to the acute form, but are milder. Death occurs on the 15-20th day. Sometimes a pig recovers, remaining a virus carrier for life;
- chronic. It is asymptomatic. It is very rare in domestic pigs. This form is mainly observed in wild African pigs. An animal with a chronic form is a very dangerous carrier of the disease.
When comparing the symptoms of swine erysipelas and ASF, it is clear that the symptoms of these two diseases differ little from each other.Photos of pigs that died from African swine fever also differ little from images of pigs with erysipelas. For this reason, laboratory tests are necessary to accurately diagnose the disease.
The photo shows signs of African swine fever. Or maybe not ASF, but classic. Without microbiological studies it’s impossible to figure it out.
Laboratory diagnosis of African swine fever
ASF must be differentiated from erysipelas and classical swine fever, so the diagnosis is made comprehensively based on several factors:
- epizootological. If there is an unfavorable situation in the area regarding ASF, animals are most likely to suffer from it;
- clinical. Symptoms of the disease;
- laboratory research;
- pathoanatomical data;
- bioassays.
The most reliable way to diagnose ASF is to use several methods simultaneously: hemadsorption reaction, PCR diagnostics, fluorescent body method and bioassay on piglets immune to classical plague.
A highly virulent virus is easy to diagnose, since in this case the fatal outcome among sick animals is 100%. Less virulent strains of the virus are more difficult to identify. Suspicion during an autopsy should be caused by pathological changes characteristic of African swine fever:
- a greatly enlarged spleen of a dark red color. May be almost black due to multiple hemorrhages;
- lymph nodes of the liver and stomach enlarged 2-4 times;
- similarly enlarged hemorrhagic lymph nodes of the kidneys;
- numerous hemorrhages in the epidermis (red spots on the skin), serous and mucous membranes
- serous exudate in the abdominal and thoracic cavities. May be mixed with fibrin and blood
- pulmonary edema.
Genotyping of African swine fever is not performed during diagnosis. Other scientists are doing this using wild African stock.
Instructions for eliminating African swine fever
Measures to eliminate the outbreak of African swine fever are carried out by veterinary services. According to the international classification, African swine fever is assigned hazard class A. All that is required of the pig farmer is to notify the service about the animal disease. Next, the veterinary service acts according to official instructions, according to which a quarantine is introduced in the area with the total slaughter of all pigs and checkpoints on the roads in order to prevent the possible export of infected pork to other areas.
The entire herd on a farm where ASF is detected is slaughtered using a bloodless method and buried at a depth of at least 3 m, sprinkled with lime, or burned. The entire area and buildings are thoroughly disinfected. No animals will be allowed to be kept at this site for another year. Pigs cannot be kept for several years.
All piglets are confiscated and destroyed from the population within a radius of several kilometers. A ban on keeping pigs is introduced.
It must be taken into account that some porous materials cannot be fully disinfected and the virus can exist there for a long time. Materials undesirable for the construction of a pigsty:
- tree;
- brick;
- foam blocks;
- expanded clay concrete blocks;
- adobe brick.
In some cases, it is easier for the veterinary service to burn a building than to disinfect it.
Prevention of ASF
To ensure that ASF does not appear in a private household, certain rules must be followed. In pig-breeding complexes, these rules have been elevated to the rank of law and it is easier to comply with them than in a personal farmstead. After all, a pig-breeding complex is a place of work, not a place of residence. However, unsanitary conditions cannot be maintained in private household plots.
Rules for the complex:
- do not allow animals to roam freely;
- keep piglets indoors;
- regularly clean and disinfect places of detention;
- use a change of clothes and separate equipment for caring for pigs;
- buy food of industrial origin or boil food waste for at least 3 hours;
- exclude the appearance of unauthorized persons;
- do not buy live pigs without a veterinary certificate;
- move animals and pork without permission from the state veterinary service;
- register livestock with local administrations;
- do not slaughter animals without pre-mortem inspection and sell pork without a sanitary examination of the meat;
- do not buy pork “from hand” in places not designated for trade;
- do not interfere with veterinary inspection and vaccination of pig livestock;
- Dispose of corpses and biological waste only in places designated by the local administration;
- do not process the meat of forcedly slaughtered and dead animals for sale;
- in wild boar habitats, do not use water from streams and calm rivers for watering animals.
If you remember how the population complies with all these rules, you will get approximately the same picture as in the video below.
Is African swine fever dangerous for humans?
From a biological point of view, it is completely safe. It is very dangerous for the nerves and wallet of the pig owner. Sometimes ASF is also dangerous for the freedom of the person responsible for the ASF outbreak, since failure to comply with the above rules can lead to criminal liability.
Conclusion
Before getting a pig, you need to check with the veterinary service about the epidemiological situation in the area and whether it is possible to get pigs. And you must always be prepared for the fact that at any moment an outbreak of ASF may appear in the area, as a result of which the animal will be destroyed.
