Porcine circovirus infection: causes, symptoms and vaccines

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

In farms specializing in breeding piglets, all the required technologies must be strictly observed. Various kinds of violations on such farms lead not only to a decrease in the productivity of animals and a drop in profits, but also to outbreaks of various kinds of contagious diseases. One of the most dangerous diseases affecting piglets and causing significant harm to farms is porcine circovirus infection.

What kind of disease

This ailment mainly affects only small piglets aged 6 to 14 weeks. Moreover, in 70-80% of cases, the disease leads to death. Weaned piglets are particularly susceptible to porcine circovirus infection.

This disease, unfortunately, has not been studied very well at the moment. However, since its prevalence both in other countries of the world and in our country is quiteHowever, it is capable of causing significant damage to farms, and scientists pay a lot of attention to it. To date, several vaccines have been developed that can treat this disease and prevent it from developing in animals.

What kind of virus causes

The cause of the development of this disease in pigs is infection with a DNA virus of the genus Circovirus. At the moment, two main forms of this pathogen are known:

• non-pathogenic (PCV-1);
• pathogenic (PCV-2).

The first type of virus was isolated by scientists back in 1974. This form of disease development does not cause piglets. The cause of circovirus infection of pigs is the second type of virus - pathogenic. The microorganism PCV-2 has a diameter of 17 nm and contains a circular single-stranded DNA genome. A feature of the pathogenic species of the PCV-2 virus is, among other things, a very high degree of resistance to changes in the environment. At a temperature of +60 °C, this virus retains its normal activity for 30 minutes. This pathogen can only be destroyed by boiling for at least 10 minutes. At negative temperatures, this pathogen is frozen with the preservation of all its properties.

In the body of pigs, the PCV-2 virus is usually localized in the cells of the lymphatic and immune systems. Its incubation period is 3-4 weeks.

A bit of history

For the first time, farmers in France faced this infection. The pathogenic form of this microorganism was identified only in 1997. In Russia, the firstcases of infection with circovirus infection of pigs were registered only in 2000. In 2008, the disease spread to the Urals.

At the moment, this disease is one of the main problems of farmers in all European countries that produce pork. What was the impetus for the pathogenic activation of the PCV virus in recent years, scientists, unfortunately, is unknown. At the moment, as already mentioned, the best veterinary laboratories in the world are developing vaccines against circovirus infection.

Risk factors

Today, almost all pig farms in Russia are infected with the PCV-2 virus. But outbreaks of the disease itself still occur only in some farms. The presence of this virus in the body of a pig in many cases does not cause the development of the disease. As noted, piglets get sick with a circovirus infection only under the condition of some sufficiently serious external stress push. It could be, for example:

• weaning and a sharp deterioration in living conditions;
• Vaccination against any disease too early;

• too much crowding with the manifestation of aggression of individuals towards each other.

Very often, outbreaks of such an infection are also observed when piglets are kept in groups of different ages. In this case, older individuals often begin to terrorize the younger ones. As a result, the latter experience severe stress, which causes the development of the disease.

Interesting fact

Scientists studying this disease some time ago conducted a rather informative experiment. Experts tried to infect he althy piglets with a circovirus infection virus in sterile laboratory conditions. And as a result, it turned out that not a single animal got sick.

That is, in addition to stress, the main impetus for the development of circovirus infection in pigs is precisely poor living conditions. These include the lack of ventilation in the pig farm, untimely procedures for cleaning manure and changing bedding, feeding and watering pigs from dirty dishes. Also, the use of low-quality feed on farms - stale, moldy, rotten, etc. - feed can lead to a weakening of the immunity of piglets.

How it spreads

The PCV-2 virus is transmitted from individual to individual mainly by airborne droplets. In some cases, infection can also occur vertically, that is, from the pig to the piglets born to her. At the same time, in the same uterus, some of the cubs are usually born he althy, and some are sick.

The PCV-2 virus can be released into the environment with the feces of infected animals, semen, mucus from the eyes and nose, and urine. The main factor, the "trigger" of the disease, is, as already mentioned, stress. Actually, the PCV-2 virus itself can enter the body of piglets through infected:

• litter;
• feed;
• water.

Farmers noticed, among other things, thatpiglets kept in individual boxes, even with a strong outbreak on farms, usually do not get sick.

Methods for diagnosing circovirus infection in pigs

First of all, if this disease is suspected, the veterinarian conducts a visual examination of the animals. You can determine the development of circovirus disease in piglets by the following signs:

• developmental lag from peers;
• refusing food;
• cramps of the neck, limbs.

Infected newborn piglets look sleepy and lethargic. However, in most cases they have difficulty sucking milk. The skin of infected piglets looks icteric.

Dermatitis is also a characteristic symptom of swine circovirus infection. In the photo below you can see two individuals in which this feature is very pronounced. In any case, animals with such an ailment look actually sick and lethargic. And of course, sick piglets develop very slowly.

Very often this ailment manifests itself as impaired coordination of movements and paresis of the limbs. Death with this disease can occur suddenly. In some cases, the disease in piglets proceeds in a latent form. In such animals, symptoms of circovirus infection practically do not appear. However, they are still carriers of the disease.

The outward signs of this disease can thus be expressed quite clearly. However, similarMany other illnesses in piglets also have symptoms. Therefore, the most accurate method for determining pig circovirus infections in animals is laboratory diagnostics. In such studies, the virus is isolated from primary cultures of porcine kidney cells. It is on the basis of laboratory tests that the final diagnosis of circovirus disease in piglets is made.

Treatment

Engaged in the development of vaccines against circovirus infection of pigs today, both foreign and domestic scientists. Russian specialists, among other things, developed the drug "Porcilis PSV". The action of this medicine is aimed at triggering the immune response of the body of piglets.

Foreign vaccine against swine circovirus infection is currently still under development. The use of this serum is expected to reduce the risk of infection in piglets and promote recovery.

Prevention: basic measures

Treatment of porcine circovirus infection can thus be successful. But of course, it is much easier to prevent the development of this disease on the farm. The main measure to prevent the outbreak of this disease is the transfer of the farm to a two-phase pig breeding system.

In the traditional three-phase technique, piglets are weaned abruptly from their mothers and immediately transferred to other quarters. Young animals experience stress in this case due to a change in diet and environment. In addition, in rooms intended for grown-up piglets, the air temperature is usuallylower than in the sow pen. As a result, piglets begin to freeze, which becomes an additional stress factor.

With a two-phase system, after weaning from the mother, the young animals are kept in the same room with her for some time (up to about 3-4 months). Thus, animals at the first stage get used mainly only to a change in diet. Since the mother is next to them during this period, they do not experience much stress. Accordingly, the disease does not develop in them.

Also, in order to avoid stressful situations and outbreaks of circovirus infection, farms use a new vaccination scheme against various diseases. Vaccinations for piglets usually also become stressful and also lead to a temporary weakening of the body. To reduce the risk of an epidemic of circovirus disease, therefore, vaccination of pigs in farms against contagious diseases (with the exception of PCV-2 itself) is started no earlier than at the age of 13 weeks.

Additional measures

Also for the prevention of circovirus infection of pigs in farms:

• exclude contact with farms that are unfavorable for this disease;
• periodically check feed for mycotoxic components.

It has been observed that the complete disinfection of premises on farms, as well as inventory, does not contribute to stopping the development of this disease. But, despite this, of course, they must still observe sanitary standards on farms. If there is a risk of a circovirus outbreak on the farm, old bedding should bepigs are removed and a new one is put in. At the same time, not too much straw is laid. It has been observed that pigs from pens with thick litter containing high levels of pathogens are more likely to develop the disease.

All piglets purchased from other farms, for example, to replenish the herd on farms, are initially supposed to be quarantined in separate rooms. This significantly reduces the risk of a subsequent outbreak on the farm not only of circovirus infection, but also of many other contagious and at the same time very dangerous diseases of piglets.

Vaccination

Vaccinations against this disease in piglets in domestic farms are currently done twice: just before weaning and 3 weeks after that. For the manufacture of a vaccine against circovirus infection, local material from convalescent pigs is used. They give piglets injections in the neck behind the ear.