Porcine Reproductive Respiratory Syndrome (PRRS)


In veterinary PRRS in pigs (reproductive respiratory syndrome) is called a contagious disease associated with impaired activity of the respiratory organs. It leads to mass abortions of pregnant individuals in the late stages of pregnancy, the birth of dead or non-viable piglets. Pathology does not spare animals of all breeds and ages, it becomes a disaster of farms. The danger lies in the fact that special medicines and an effective vaccine against the disease have not yet been invented.

Unfamiliar and dangerous enemy

A brief history of the appearance and control of PRRS is as follows.

It was first registered in the United States in the 1980s. Already in 1990, scientists substantiated its infectious nature, and a year later they were able to isolate the virus-pathogen. The disease of pigs received the name - "epizootic late abortion." It acquired the character of an epidemic in European countries and came in 1991 to the territory of Russia, to the Kursk Region.

Nowadays, PRRS wanders around countries with developed pig breeding, and covers a large number of farms. It causes a high damage to the economy due to a violation of the reproductive capacity of the pig population, the death of piglets (from 80 to 100%), a decline in the quality and value of pork.

At the time of acute outbreak of PRRS outbreaks in the initial stages, adult individuals in pig farms also die (1-3%). Many funds are directed to the diagnostic study and the fight against the disease.

Comes in all directions

The PRRS syndrome covers all livestock, causing respiratory impairment in many pigs, boars and piglets, and reproductive function in pregnant females. The source of infection is transmitted through mucus, excrement, semen. The most dangerous are direct contacts with diseased individuals.

The virus is transmitted during mating and artificial insemination. Facts of infection and at a distance (up to 20 km) are recorded. From a sick individual, the PRRS virus can easily cross the placenta to the fetus.

A virus may appear in the household from contaminated feed, manure, equipment for transporting animals, working clothes, water and air, and rodents.

In separate episodes, the meat of diseased pigs can also become a transmitter of the pathogen.

Very often, the PRRS virus occurs when a herd of pigs is renewed with new, seemingly healthy individuals, but carrying a dangerous microbe.

Insidious plans for the virus

The disease brought by the PRRS virus can "sleep", occur in a latent form in pigs, asymptomatic. An exacerbation starts against the background of stress due to deficiencies in feeding, care, regrouping and transportation of individuals. Usually, from a hidden form to an open disease passes approximately 3-5 months after the acquisition of infected animals.

The virus does not have a favorite season of the year, but is clearly manifested during farrowing.

Pathology of the reproductive system in PRRS occurs frequently. A sow that has had a disease, usually gives birth to no more than 37.5% of viable offspring. If piglets appear during the acute phase of infection, they have almost no chance of survival, the mortality rate reaches 100%. Among weaned piglets, this figure reaches 30-40%.

The surviving individuals after PRRS, as a rule, do not get sick again, however, pigs may later have procreations.

A virus that fears heat and the sun

The PRRS virus is called Arterivirus suis. It consists of RNA, round shape, the size of 28.4 nm. His location is trachea pigs, where he successfully multiplies.

The virus is of American or European genotype. The nature of the disease he causes depends on the strain, which may be more or less dangerous.

This virus - the enemy of pig farms has a weak spot. It loses its activity when heated to a temperature of 55 degrees (after 45 minutes) and up to 37 degrees (after 48 hours).

The virus does not like scattered light and ultraviolet rays, the processes of freezing and thawing, the treatment of carbon dioxide and the change in the acid-base properties of the medium.

The PRRS virus cannot resist against all disinfectants that kill the pathogens of the second resistance group. In an empty room that has not been processed, he can maintain his enemy qualities for up to 3 days.

Dangerous consequences of an attack

From the moment of the PRRS virus penetration into the body of a pig, the appearance of the first symptoms can take from 4 to 35 days. The disease is three-phase, sometimes proceeds covertly. First, adults become ill - they develop respiratory syndrome.

Next, PRRS infection passes to the young, piglets. During the acute exacerbation phase, the following symptoms of the disease are observed:

  • depressed state, oppression of individuals;
  • refusal to eat;
  • increased (40.5-41 degrees) or low body temperature;
  • sometimes bluish coloring of the ears, the area of ​​the patch, tail, mammary glands, genitals;
  • impotence and atrophy of testicles in boars;
  • late abortion in pregnant pigs;
  • death of the born pigs;
  • the presence in the offspring of the mummy of similar and ugly piglets (with a curved head, anomalies in the skeleton, eye pathology).

Attracts bad "friends"

PRRS can occur chronically, which is also accompanied by the depressed state of pigs, lack of appetite, loss of vision, even blindness, and damage to the respiratory tract.

The general clinical picture of PRRS is very similar to other pathologies, for example, rotovirus, enterovirus, often there are complications in the form of the disease colibacteriosis, pasteurellosis, salmonellosis.

PRRS affects the duration of pig farrowing (increased by 2-4 days) and the intensity of labor at birth. The fetus and placenta go out with difficulty, leading to postpartum fever. This requires a long service period. In piglets that have undergone PRRS infection, the number of piglets in one litter decreases in the subsequent period (from 10 to 15%).

The piglets born from a sick pig have long suffered from various diseases: conjunctivitis, diarrhea, cryptorchidism, edema.

Lab test required

There are three criteria for the diagnosis of PRRS.

In accordance with them, firstly, there must be at least one fifth of all sows in the herd who brought the dead piglets. Secondly, 8% of them should have abortions or preterm delivery. And, thirdly, at least a quarter - to be born unviable babies (perishing in the first 7 days after birth).

If there are at least two signs - then, most likely, this is PRRS.

Laboratory diagnosis is required to clarify the diagnosis. As materials, liquid is sent from the cavities of the dead piglets, pieces of the lungs, spleen, brain, blood serum of aborted pigs.

There are new possibilities for the determination of the PRRS virus antigen, for example, the diagnosis of a sample of saliva by PCR and ELISA. They not only help identify PRRS, but also swine flu, enzootic pneumonia, type 2 circovirus.

An autopsy will show the true reasons.

An opening of those who died from PRRS or abortion piglets shows that they have puffiness and hemorrhage in the subcutaneous tissue, excessive fluid in the internal cavities — thoracic, percardial, abdominal, hyperemia and hemorrhage in the lungs, dystrophic processes with hemorrhages in the liver, heart, non-suppurative encephalsis, dystrophic processes with hemorrhages in the liver, heart, non-purulent encephalon, heart, non-suppurative hemorrhages in the lungs;

Pork lungs (usually the front plates) are stained (red, brown). As a rule, the lymph nodes are enlarged, they are filled with fluid and have cysts. Deviations are observed on the nodes of the neck, groin, mediastinum. The umbilical cord may be edematous, with bruising.

When opening sows, lesions of the uterus are found, and there are no other characteristic features.

Many changes are the result of exposure to the organs of pigs, not the PRRS virus, but other microorganisms.

Important measures and restrictions

If the diagnosis of PRRS is confirmed, the authorities declare the farm or the entire settlement to be unfavorable and begin to impose restrictions. First of all, it is necessary to isolate all individuals with symptoms of the disease, as well as those who have been in contact with them.

Slaughter and sale of individuals, sperm, movement and rearrangement of pigs is stopped. Undesirable is the contact of the person serving the sick piglets with healthy animals. On farms, transport, equipment, facilities, clothing are subject to mandatory disinfection, personnel - sanitary and shower processing.

Pork is sent for heat treatment (sausage and canned food), bones, offal is processed into bone meal.

Restrictions are removed 2 months after the last case of detection of sick pigs. Only six months later, you can acquire new individuals.

The main thing - to prevent complications

To date, there is no effective treatment for the virus Arterivirus suis. Given that it dramatically reduces the immunity of pigs, it is important to prevent complications from PRRS and the appearance of a "bouquet" of infections.

In the fight against the latest antibiotics are good. They should be given to pigs before farrowing.

To reduce mortality among newborn piglets, they are sucked up with colostrum (artificially possible), glucose, electrolyte solutions, give drugs from the tetracycline series or amoxicillin.

Tetracycline can also be mixed with feed for adults in the event of an outbreak of PRRS disease. In order to prevent bacterial infection, it is useful to give probiotics with B. licheniformis and B. subtilis.

Be sure to monitor the temperature in the room: it must be at least 21 degrees. Machines for sows should be disinfected with infrared rays.

Vaccinations are needed, but do not always help.

Measures to combat the virus Arterivirus suis on farms are reduced mainly to periodic vaccinations.

It should be remembered: vaccine immunity in pigs is partial. The effectiveness of vaccinations depends largely on compliance with the conditions of biological safety in the economy.

Arterivirus suis is vaccinated to pigs for various purposes: to suppress the outbreak of the infection, to adapt, acclimatize the individuals, to re-vaccination and immunize the piglet babies.

In case of emergency vaccination of pigs, the preparation should contain live (attenuated and modified) viruses. When the procedure is repeated, the use of inactivated vaccines is possible.

The effectiveness of vaccination depends on the strain of the virus. Unfortunately, there are very dangerous varieties against which vaccines do not provide protection.

Read more about the topic in the article "Vaccinations of pigs from birth."

Live and non-living vaccines

Live vaccine pigs are vaccinated at the age of 20-30 days for the first time and in the second - in 2-3 months.

It is very important to observe the deadlines for the maintenance of young stock - no later than 2 months before mating (artificial insemination).

A live vaccine in a volume of 2 ml is administered intramuscularly. Immunity is developed approximately 2 weeks after vaccination and lasts 4 months.

Vaccinated pig emulsion inactivated vaccine is done twice, maintaining an interval of 20-30 days, no later than 3 weeks before mating. Next, vaccinated sows are given 1 injection 21 days before conception, and boars every six months.

Pigs are vaccinated for 1.5 or 2 months, repeated procedure - in 20 days. Dose - 2 ml. Immunity appears 3 weeks after the second vaccination and lasts up to six months.

The vaccine protects pigs from paravirus infection.

Protection from multiple enemies

Inactivated concentrated vaccine is used not only against the PRRS virus. This is the prevention of leptospirosis, chlamydia, Aujeszky's disease. She vaccinated repair females (before mating for 3-4 weeks), pigs after weaning piglets, young boars in 6-7 months. The vaccination is done 1 time intramuscularly (2 ml in the neck).

Revaccination is carried out every six months. Immunity is developed in about a month and lasts up to 6 months.

Prevention of PRRS with vaccines is cost-effective, but still risky. There is a possibility of reversing the virus, getting it into the external environment.

For any vaccination, it is important to avoid accidental transmission of the virus from vaccinated animals to unvaccinated, especially pregnant pigs and producing boars (the pathogen can be transmitted with sperm, remaining there for more than 90 days).

Simple preventive truths

To prevent the occurrence of outbreaks of PRRS infection, one should strictly adhere to the veterinary standards for pigs.

Prevention includes the creation and maintenance of a microclimate that complies with zoohygienic standards, preparation of safe and complete food, periodic disinfection of all rooms, transport, work clothes, timely cleaning of places for pigs from manure, systematic assessment of herd health, compliance with quarantine rules for new individuals.

It is especially necessary to pay attention to the fact that it is impossible to feed waste to pigs and piglets without thermal preparation (70 degrees, at least 30 minutes).

Premises on the farm should be repaired, whitened, washed and disinfected after each technological cycle. Preventive break should be at least 10 days.

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