Infectious causes of infertilidad in the sows

(*) Dres. Jeanette Floss and Roderick Tubbs, (Univ. of Missouri - Columbia - USA)

In any moment, a sow can have a premature childbirth and it exists the fear that they get lost additional litters. A rate of abortions smaller than 2% is considered acceptable in most of the flocks. The premature childbirths generally take place for estrés nutritional, genetic or environmental, but many times the causes they are ignored.

The abortion is the most dramatic expression in production loss. When in a certain flock their incidence increases, it is usually suspected that an infectious agent exists. The increase of abortions can continue after the addition of substitution animals or to the mixture of groups of animals that previously were separate. Approximately 38% of the diagnosed abortions is attributed to infectious causes.

The gestation stage during the one which the sow and/or the fetuses are infected it will be the one that determines the capacity of survival of the litter. In some cases, the infectious agent affects the development of the fetuses and the placentas directly, causing fetal commitment and the death.

Any serious illness of the pregnant sow can be in death of the fetuses, due to the interruption of the normality of the uterine atmosphere. They can get lost one, several or all the fetuses of the litter. If the infection happens to less than the 35 days of gestation, the fetuses can be reabsorbed. If it happens among the days 35 and 70 days of gestation, the fetuses mummify. If it is after the day 70, it can be that the pigs are born weak or dead. In this article you several infectious causes of infertilidad and abortion discuss in the sows, as well as some preventive measures.

Bacterial infections

The bacterias penetrate to the uterus through the cervix open to the moment of the childbirth, but they are generally eliminated before an infection settles down. The sows will have a vaginal discharge during 1 to 3 days after the childbirth. This discharge is normal, if he/she doesn't have bad scent and it is not associated with some clinical illness in the sow or the pigs.

But, if a sow gives birth to in a polluted atmosphere, an excess of fecal matters or the childbirth is attended with little hygiene, metritis can appear. This is the most severe form in uterine infection. The uterus you full with big quantities of not well smelling fluid and of fetal membranes in decomposition. The sow develops fever, it will feel sick and he/she could die as a result of the toxins that produce the bacterias. Their pigs can show symptoms of malnutrition. The illness leaves to the few days after the childbirth. If the sow recovers, its fertility will be diminished in the next service.

The endometritis, or inflammation of the uterine membrane is less severe, but possibly more important economically. The bacterial illnesses of the reproductive tract can be in flaw in the conception and/or embryonic death. The bacterias penetrate to the uterus during the estro and it mounts it because the cervix relaxes herself in that moment. The increase of the rate of repetitions can be the only indication that a problem exists. The return intervals to zeal can be normal or lingering.

The inflammation of the endometrio is not compatible with the survival of the embryos for what the pregnancy will end. These animals are frequently clinically normal or they can present a low fever. One can observe a slight vaginal discharge in the next zeal. The lechonas that you/they live under sobrepoblación conditions can develop endometritis.

The vaginitis also produces vaginal discharges. The fertility can it doesn't turn affected, unless the bacterias penetrate in the uterus during the service. The lechonas and the mature sows that have been exposed at high levels of the micotoxina zearalenona in their diet will develop vaginitis and vaginal discharges. The properties estrogénicas of this substance will prevent that these animals can have normal cycles.

A high diet in calcium and match can be in the formation of salts in the urine, what causes the exit of a flowing blancuzco that he/she appears in the vulva. He/she should not made a mistake with an infection, although the infections of the tract urinal can cause similar vaginal discharges. An appropriate consumption of water can help to prevent infections helping to frequent micturitions and the mechanical cleaning of the tract urinal.

The bacterias that cause these infections of the tract urinal and reproductive they can be in these systems and/or in the atmosphere. When they are the systems those that are polluted and the defense mechanisms are overloaded, the infection takes place. The most effective methods of preventing it are to provide a clean environment (good waste elimination) and enough it dilutes clean.

Leptospirosis

It is known that a great variety of leptospira bacterias infects the pigs. In most of the flocks that have been exposed they are few clinical cases of the illness.

The lecptospira bacterias prefer the kidney and they appear in the urine. The contact with the infected urine is the form more common of infection of the other animals. Also, you can locate in the uterus of pregnant females. If they are contagious susceptible reproductive animals, the leptospirosis can produce abortions, mortinatos or the birth of weak pigs.

Different serovares of Leptospira interrogans has been found in the pigs. The pomona is the more commonly involved in the infertilidad. The bratislava has also been persistent in the oviduct and uterus of non pregnant females and the superior genital tract of the hogs, contributing to the infertilidad. It is possible that this infection can be contagious during the mating. However, for the time being he/she has not committed the infection of Bratislava with clinical buds to great scale in the United States.

They exist bovine against the leptospirosis, but the immunity that you/they give it is usually brief. The reproducers should be vaccinated at least twice a year and up to four times in infected flocks. The vaccinations should be applied before the services. The antibiotics help to reduce the incidence of the illness but they cannot eliminate it completely in an infected flock. The rodents and the fauna wild local can also be infected and to contribute to the dissemination of the leptospirosis. The handling practices that the populations of rodents eliminate and impede the contamination of the food and the water for the urine, they will also contribute in great measure to clean up the atmosphere. During a bud, the animals clinically sick persons should be treated and those that are in contact with them should be vaccinated.

Brucellosis

The brucellosis is produced in the pig by the Brucella suis. It is a microorganism that also infects the humans. He/she is contagious for direct contact with infected fabrics, especially, miscarried fetuses and membranes. The hogs develop a persistent infection and they can excrete bacterias in the semen, what contributes to the dissemination of the illness. The females that are infected during the service can miscarry in any stage of the gestation.

The antibiotics are of little value in the treatment of the brucellosis. It is better to adopt practical of handling to maintain the flocks free of brucellosis. The risks to the human health should always be considered when miscarried fetuses or fetal membranes are managing.

Swinish Parvovirus

Few animals exhibit clinical illness as a result of infection for swinish parvovirus. This virus is in most of the swinish flocks, but the animals that have been exposed previously they develop immunity.

The swinish parvovirus crosses the placenta and it infects to the fetuses in development. The non immune females, infected during the first half of the gestation, will generally have several fetuses mummified to the childbirth.

The lechonas is affected with more frequency than the mature sows.

If the infection happens during the pregnancy stillborn they will be presented, dead pigs when being born, weak pigs and infertilidad. The abortions are not very common. If the infection happens at the end of the pregnancy, the pigs generally survive.

Because the swinish parvovirus this broadly disseminated in the flocks, all the lechonas should be exposed naturally or vaccinated at least 30 days before the service. There is bovine inactivadas and live modified that should be administered under the supervision of a veterinarian. There is not treatment against the infertilidad induced by the swinish parvovirus, but the animals infected in natural form they are immune of for life.

Swinish Enterovirus

The same as with the swinish parvovirus, the enterovirus is present in most of the flocks, but many times they don't produce any clinical illness. The enterovirus has been associated with illnesses of the central nervous system (poliencefalitis), diarrhea and pneumonia. They can also produce not fetal losses specific, similar to those of the infections with parvovirus.

The virus crosses the placenta, therefore, the lechonas and pregnant sows can give birth to fetuses dead or mummified, less pigs for litter or simply not to give birth to. The abortions are strange.

There is not available vaccine for the protection against losses reproductive resultants of infections with enterovirus. The best preventive practice is to assure that the lechonas has been exposed to fecal matters of animals of other flocks, especially old sows, at least one month before the service. As it happens with the swinish parvovirus, there is not treatment for the infection, however, the subsequent fertility doesn't seem to be affected.

Seudorabia

The resulting abortions of infections for the seudorabia virus (VSRP) they generally take place after a period of fever and of breathing illnesses, in lechonas and pregnant mature sows. If the susceptible females are infected to the beginning of the gestation, the fetuses can be reabsorbed. Approximately 20% of the females infected at the end of the gestation, they miscarry. The pigs that are born alive they are weak and many times they don't survive more than one or two days. Other signs of the illness in a recently infected flock include: pneumonia in the pigs in crecimiento/acabado, illnesses of the nervous system, death in the pigs nurslings and recently weaned pigs. Flocks with endemic infection cannot show other clinical signs that an increase of the susceptibility to breathing illnesses in the pigs in it puts on weight and finish.

There are vaccines for the virus of the pseudorrabia. It doesn't prevent the clinical illness if the animals are infected, but it reduces the severity of the illness and their dissemination in the flock. The vaccination should make it a veterinarian.

SRRP/SRIP

At the end of the decade of the 80, many swinish flocks experienced great quantity of abortions, continued by an increase in the incidence of stillborn and mummified. The rate of survival was very low for the pigs that were born alive. Also, the pneumonia was reported, affecting pigs of all the ages in those flocks. Many of the sows that recovered experienced periods of infertilidad. Recently, it was isolated a virus of RNA like the causal agent. The process of the illness that called you at the beginning the Mysterious Illness of the Pigs, calls himself now Swinish Reproductive Breathing Syndrome (SRRP) or Breathing Syndrome of Swinish Infertilidad (SRIP).

The recently infected flocks followed the illness pattern described previously. Plus recently the SRRP has associated with the pigs that progress bad in the weaning and with the decrease in the pariciones rates. Also, the conception rates and the quantity of served animals has diminished. The next sows to the childbirth, present fever and appetite loss.

As a specific treatment it doesn't exist for the SRRP, support therapy should be given to the sick animals. It is useful to give them medications to diminish the fever and to encourage them to eat. When acquiring animals of flocks that have not been exposed, these they should be isolated at least during 30 days, to diminish the infection of this illness and to establish a strict control of the movement of the animals inside the flock.

Summary

It is necessary to distinguish the abnormal vaginal discharges from the later normal discharges to the childbirths and the silts urinals, so that the affected animals are treated appropriately. The resulting discharges of infections of the reproductive tract are generally associated with other reproductive events as the childbirth (metritis) and the estro or the service (endometritis). The discharges associated with vaginitis and with infections of the tract urinal they don't generally follow the reproductive cycle. The lightest cases can be treated with antibiotics, but the animals infected in persistent form they should be eliminated.

It should be suspected the parvovirus presence or enterovirus when the incidence of mummies increases, especially in lechonas that have not been exposed previously. In a susceptible flock, the breathing nuisances, accompanied by high fever, continued by abortion can indicate pseudorrabia or infection for SRRP. The resulting abortions of brucellosis are not very common, but he/she will be necessary to think of leptospirosis in the areas where this is prevalente.

The problems for reproductive infections can be controlled better with strict practices of preventive handling. All the lechonas should be exposed to mature sows before the service in the flocks where there are parvovirus and enterovirus. Once infected, the lechonas will develop immunity of for life and their fertility is good.

There is bovine against parvovirosis, pseudorrabia and leptospirosis. It should be administered at least 30 days before the service to the lechonas and to repeat the application in the areas of high risk (leptospirosis). The flocks are better protected of seudorrabia and SRRP raising the substitution lechonas or only obtaining them of flocks free of those illnesses. The new additions should be isolated of the rest of the flock during the first 30 days.

The sanitary maintenance should include the appropriate elimination of waste, enough space for the lodging of the animals and to avoid that the foods and the water are contaminated. The combination of all those measures will diminish the production losses that are of the infections.