"Any severe illness in a pregnant sow may result in fetal death due to a disruption in the normal uterine environment. One, several or all fetuses in a litter may be lost. If fetal compromise occurs at less than 35 days of gestation, fetuses may be reabsorbed. If infection occurs between 35 and 70 days of gestation, fetal mummification occurs. If infection occurs after 70 days of gestation, pigs may be delivered weak or dead. This publication addresses several infectious causes of infertility and abortion in sows along with some preventive measures."Jeanette L. Floss (College of Veterinary Medicine), Roderick C. Tubbs (Swine veterinarian, Commercial Agriculture Program)Reviewed November 2018 -- websit

Floss, Jeanette L.

Tubbs, Roderick C.

English

University of Missouri: MOspace

6/10/2019 Infectious Causes of Infertility in Sowshttps://extension2.missouri.edu/catalog/product/view/id/897/ 1/5Infectious Causes of Infertility in SowsJeanette L. FlossCollege of Veterinary MedicineRoderick C. TubbsSwine veterinarianCommercial Agriculture ProgramAny time a sow farrows prematurely, there is the fear that additional litters will be lost. An abortion rate of less than 2 percentis considered an acceptable level in most herds. Premature farrowing usually results from nutritional, genetic orenvironmental stresses, but the exact cause is often unknown.Abortion is the most dramatic expression of production loss. When the incidence increases for a given herd, an infectiousagent is usually suspected. This increase may follow the addition of replacement animals or the mingling of previouslyisolated groups of animals. Approximately 38 percent of diagnosed abortions are attributed to infectious causes.The stage of gestation during which the sow and/or fetuses become infected will determine the litter's ability to survive. Insome cases the infectious agent will directly affect developing fetuses and placentas, causing fetal compromise and death.Any severe illness in a pregnant sow may result in fetal death due to a disruption in the normal uterine environment. One,several or all fetuses in a litter may be lost. If fetal compromise occurs at less than 35 days of gestation, fetuses may bereabsorbed. If infection occurs between 35 and 70 days of gestation, fetal mummiﬁcation occurs. If infection occurs after 70days of gestation, pigs may be delivered weak or dead. This publication addresses several infectious causes of infertility andabortion in sows along with some preventive measures.Bacterial infectionsBacteria gain access to the uterus through the open cervix at farrowing, but usually are eliminated before they are able toestablish an infection. Sows will have a vaginal discharge for 1 to 3 days after farrowing. This discharge is normal, is not foulsmelling and is not associated with clinical illness in the sow or pigs.However, if a sow farrows in an environment contaminated with excessive fecal material or the delivery is assisted in anunsanitary fashion, metritis may develop. This is the most severe form of infection in the uterus. The uterus ﬁlls with largeamounts of malodorous ﬂuid and decomposing fetal membranes. The sow will develop a fever, be ill and possibly die as aresult of bacterial toxins. Her pigs may demonstrate signs of malnourishment. This condition is seen within days of farrowing.If the sow recovers, her fertility during the next breeding will be reduced.Endometritis or inﬂammation of the lining of the uterus is less severe clinically, but possibly more important economically.Bacterial infections of the reproductive tract may result in conception failure and/or early embryonic deaths. Bacteria gainentrance to the uterus during estrus and breeding because the cervix relaxes at this time. An increased return-to-servicerate may be the only indication that a problem exists. Return intervals may be normal or prolonged.Inﬂammation of the endometrium is not compatible with the survival of embryos and the pregnancy will be terminated.These animals are often clinically normal or they may have a low-grade fever. A mild vaginal discharge may be seen aroundthe time of the next expected heat. Gilts that are housed in overcrowded conditions may also develop endometritis.Archive version -- See extsion.missouri.du6/10/2019 Infectious Causes of Infertility in Sowshttps://extension2.missouri.edu/catalog/product/view/id/897/ 2/5Vaginitis will also cause a vaginal discharge. Fertility may not be reduced unless bacteria gain entrance to the uterus atbreeding. Gilts and sows that have been exposed to high levels of the mycotoxin zearalenone in the diet will developvaginitis and a discharge. The estrogenic properties of this compound will prevent these animals from cycling normally.A diet high in calcium or phosphorous may result in the formation of salts in the urine leading to a white, chalky ﬂuid which isseen at the vulva. This should not be confused with infection, although infections of the urinary tract may cause vaginaldischarges. Adequate water intake helps to prevent infection by encouraging frequent urination and mechanical ﬂushing ofthe urinary tract.The bacteria that cause these urinary and reproductive tract infections can be found within the tracts and/or in theenvironment. When the tracts are contaminated and the defense mechanisms are overloaded, infection results. The mosteffective means of preventing this is to provide a clean environment (proper waste removal) and a suﬃcient source of freshwater.LeptospirosisA large number of Leptospira organisms are known to infect swine. In most herds that have already been exposed, fewclinical cases of disease will be found.Leptospira bacteria prefer the kidney and are shed in the urine. Contact with contaminated urine is the most common meansof spreading the infection to other animals. Leptospira also will localize in the pregnant uterus. If susceptible breedinganimals become infected, leptospirosis may lead to abortions, stillbirths or the birth of weak neonates.Several serovars of Leptospira interrogans have been found to infect swine. Pomona is most commonly involved in swineinfertility. Bratislava also has been found to persist in the oviducts and uterus of non-pregnant females and in the uppergenital tract of boars contributing to infertility. It is possible that this infection could be spread during mating. At the presenttime, however, bratislava infection has not been linked to clinical outbreaks on a wide scale in the U.S.Vaccines are available for leptospirosis. However, the immunity they provide is usually short-lived. Breeding animals shouldbe vaccinated at least twice a year and up to four times a year in infected herds. Vaccinations should be given prior tobreeding. Antibiotics will help reduce the incidence of disease but cannot completely eliminate it from an infected herd.Rodents and local wildlife may also be infected and contribute to the spread of leptospirosis. Management practices thateliminate the rodent population and prevent urine contamination of feed and water will contribute a great deal to controllinginfection. During an outbreak, clinically ill animals should be treated and in-contact animals should be vaccinated.BrucellosisBrucellosis in swine is caused by Brucella suis. Brucella organisms are also infectious to humans, but due to federaleradication programs very few cases are reported in people or livestock. Brucellosis is spread by direct contact with infectedtissues, primarily aborted fetuses and membranes. Boars can develop a persistent infection and shed bacteria in the semen,which contributes to the spread of this disease. Females that become infected at breeding may abort at any stage ofgestation.Antibiotics are of little value in treating brucellosis. The prevalence of swine brucellosis has been reduced to the point thatvaccination is not practical. Management practices for maintaining a brucellosis-free herd status are encouraged. The humanhealth risks of brucellosis should always be considered when handling any aborted fetuses or fetal membranes.Porcine parvovirusFew animals exhibit clinical illness as a result of porcine parvovirus (PPV) infection. This virus is found in most swine herds,but previously exposed animals develop immunity.6/10/2019 Infectious Causes of Infertility in Sowshttps://extension2.missouri.edu/catalog/product/view/id/897/ 3/5Porcine parvovirus will cross the placenta and infect developing fetuses. Non-immune females that become infected duringthe ﬁrst half of gestation will usually have several mummiﬁed fetuses at farrowing. Gilts are affected much more often thansows.Infertility, stillbirths, neonatal deaths and delivery of weak pigs may follow infection during pregnancy. Abortions resultingfrom PPV infection are uncommon. If infection occurs late in gestation, fetuses usually will survive.Because PPV is widespread in swine herds, all gilts should be naturally exposed or vaccinated at least 30 days prior tobreeding. Inactivated as well as modiﬁed live vaccines are available and should be administered under the direction of alicensed veterinarian. There is no treatment for PPV-induced infertility, but animals that are naturally infected are oftenimmune for life.Porcine enterovirusesLike porcine parvovirus, porcine enteroviruses are present in most swine herds but often do not cause clinical illness.Enteroviruses have been associated with central nervous system disease (polioencephalitis), diarrhea and pneumonia. Theymay also produce non-speciﬁc fetal losses resembling those seen with PPV infection. Viruses cross the placenta, thereforepregnant gilts and sows may deliver stillborn pigs and mummies, deliver fewer pigs per litter or fail to farrow. Abortions arerare.There is no vaccine available for protection against reproductive losses resulting from enterovirus infections. The bestpreventive practice is to make sure gilts have been exposed to the fecal material of other herd animals, especially oldersows, at least one month prior to breeding. As with PPV there is no treatment for enterovirus infection. However, subsequentfertility does not appear to be affected.PseudorabiesAbortions resulting from pseudorabies virus (PRV) infections typically follow a period of fever and respiratory disease inpregnant gilts and sows. If susceptible females become infected early in gestation, fetuses may be resorbed. Approximately20 percent of females that become infected late in gestation will abort. Pigs that are delivered alive are weak and often donot survive more than a day or two. Other signs of disease in a recently infected herd include pneumonia in grower/ﬁnisherpigs and nervous system disease and death in suckling and newly weaned pigs. Endemically (chronically) infected herdsmay show no clinical signs other than an increased susceptibility to respiratory disease in growing and ﬁnishing pigs.Vaccines for PRV are available. These do not prevent clinical illness if animals become infected, but they reduce the severityof the disease and its spread within the herd. Vaccinations should be performed by a licensed veterinarian and inassociation with the state regulatory recommendations for the eradication of PRV.PRRS/SIRSIn the late 1980s, many swine herds experienced a large number of abortions. An increased incidence of stillbirths andmummies followed the abortion storms. Survival rates were poor for pigs born alive. Pneumonia, affecting pigs of all ages,was also reported in these herds. Many recovering sows experienced periods of infertility lasting for varying lengths of time.Recently an RNA virus has been isolated as the causative agent. This disease process, once identiﬁed as Mystery PigDisease, is now known as Porcine Reproductive and Respiratory Syndrome (PRRS) or Swine Infertility and RespiratorySyndrome (SIRS).Newly infected herds followed the disease pattern described above. More recently PRRS has been associated with poordoers in the nursery and decreased farrowing rates. In addition, conception rates and the number of animals bred havedecreased. Near farrowing, sows may develop a fever and go off feed.6/10/2019 Infectious Causes of Infertility in Sowshttps://extension2.missouri.edu/catalog/product/view/id/897/ 4/5Because there is no speciﬁc treatment for PRRS, supportive therapy should be provided to clinically ill animals. Medicationsto reduce fever and to encourage animals to resume eating are beneﬁcial. Presently, no vaccine is available for the controlof PRRS/SIRS. Purchasing animals from herds that have not been exposed, isolation of new animals for at least 30 days andstrict control of animal movement within the herd will help to minimize the spread of this disease.SummaryAbnormal vaginal discharges must be distinguished from normal postpartum discharges and urinary sediments in order foraffected animals to be properly managed. Discharges resulting from reproductive tract infections generally are associatedwith other reproductive events such as farrowing (metritis) and estrus or breeding (endometritis). Discharges associated withvaginitis and urinary tract infections usually do not follow the reproductive cycle. Milder cases can be treated with antibiotics,but persistently infected animals should be culled.Porcine parvovirus or enterovirus should be suspected when the incidence of mummiﬁed fetuses increases, particularly ingilts not previously exposed. Respiratory distress accompanied by high fever and followed by abortions may indicate apseudorabies or PRRS infection in a susceptible herd. Abortions resulting from brucellosis are uncommon but leptospirosisshould be considered in areas where it is prevalent.Infectious reproductive problems are best controlled by stringent preventive management practices. All gilts should beexposed prior to breeding to older sows in herds with PPV and PEV. Once infected, gilts will develop a life-long immunityand subsequent fertility is good.Vaccines are available for PPV, PRV and leptospirosis. These should be administered at least 30 days prior to breeding giltsand repeated as necessary in high-risk areas (leptospirosis). Herds are best protected from PRV and PRRS by raisingreplacement gilts or obtaining them only from herds that are free of these diseases. New additions should be isolated fromthe rest of the herd for the ﬁrst 30 days.Sanitary maintenance should include adequate waste removal, suﬃcient housing space and the prevention of feed andwater contamination. The combination of all these management practices will reduce production losses resulting frominfectious causes.Table 1Infectious causes of infertilityMixed bacterialinfectionsClinical signsIncreased return-to-service. Mild to profuse vaginal discharges. Sows with metritis will have a fever and gooff feed.Preventive measuresDo not house gilts or sows in overcrowded, unsanitary conditions. Provide ample amounts of fresh water.CommentsA discharge for one to three days after farrowing is normal.Leptospirosis interroganspomonaClinical signsFew clinical cases in previously exposed herd. Susceptible breeding females may abort or deliver weak ordead pigs.Preventive measuresVaccinate breeding animals two to four times each year. Protect feed and water from urine contamination.CommentsRodent numbers should be controlled because they also contribute to the spread of this disease.Brucella suis Clinical signsAbortions during any stage of pregnancy.6/10/2019 Infectious Causes of Infertility in Sowshttps://extension2.missouri.edu/catalog/product/view/id/897/ 5/5Preventive measuresPrompt removal of all aborted tissues. Routine testing for maintenance of brucellosis-free herd.CommentsPotential for human infection.Porcine parvovirus Clinical signsDelivery of mummiﬁed pigs. Stillbirths, neonatal deaths and infertility are possible. Abortions are rare.Preventive measuresVaccinate or expose gilts to infection 30 days prior to breeding.CommentsPreviously infected animals develop a life-long immunity.Porcine enteroviruses Clinical signsResembles porcine parvovirus. Abortions are rare.Preventive measuresExpose gilts to fecal material from older sows prior to breeding.CommentsNo vaccine is available.Pseudorabies virus Clinical signsAbortions may follow fever and respiratory disease in susceptible gilts and sows. Live-born pigs are weak.Pneumonia in growing pigs.Preventive measuresVaccination will reduce the severity of clinical disease. Participation in the federal eradication program.CommentsVaccination requires the approval of the state veterinarian.PRRS/SIRS virus Clinical signsNew herds experience an increase in abortions, stillbirths and mummies. Pneumonia in pigs of all ages.Reduced fertility in recovered sows.Preventive measuresNew animals should be purchased from unexposed herds and quarantined for at least 30 days.CommentsNo vaccine is available.© 1993 to 2019 Curators of the University of Missouri, all rights reserved, DMCA and other copyright information. University of Missouri Extension is an equal opportunity/access/aﬃrmative action/pro-disabled and veteran employer.

Infectious causes of infertility in sows

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Infectious causes of infertility in sows

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