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Reproductive Failure by Infectious Causes*
| Disease and agents | Clinical signs | Comments and diagnosis aids |
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Parvovirus |
Vary with gestational stage at infection. Usually in gilts. Increases in returns to heat, failure to farrow, mummies, stillbirths, and neonatal mortality. Fewer pigs per litter. There seldom are abortions or fetal anomalies. The dams are normal. | A major cause of embryonic and fetal death, more often in gilts. Infection usually endemic and inapparent. Diagnosis by IFAT on lungs of mummies <16 cm long. |
|
Porcine reproductive and respiratory syndrome (PRRS) Arterivirus |
Sows may be sick from primary infection and abort, or abortions may occur several weeks after sow infected due to fetal infection. Decreased conception and farrowing rates. Increases in stillborns, weak pigs, mummies, premature farrowings and last trimester abortions. Improved reproductive performance after 3-5 months. | Respiratory signs and illness may be in any age group. PCR on serum from acutely ill sows or serology on convalescent sows; identify virus in fresh or fixed tissues of acutely affected neonates, or PCR on fluids from multiple aborted piglets. |
|
Leptospira spp. |
Initial outbreak: Abortions and stillbirths common in late pregnancy. Piglets often weak and many die within a few days. Illness seldom noticed in dams. | After one failure, dams often breed successfully. Focal nephritis and hepatitis may be in fetuses or older swine. Diagnosis: by herd serology or by IFAT, PCR on fetal tissues. |
|
Herpesvirus |
Depends on gestational stage at infection; initially, abortions or respiratory signs. CNS signs or sudden deaths in young piglets; mortality often high, decreasing with age. Immune sows show no signs. | If endemic, reproductive signs less common than CNS or respiratory signs. Diagnosis by serology, virus isolation, IHC, PCR. Eradicated from the US since 2004. |
|
Porcine circovirus type 2 (PCV2) Family Circoviridae |
A common virus in swine population that may cause myoclonia congenita. It is associated with sporadic outbreaks of fetal death and/or mummification. | PCR may detect PCV2 in serum or tissues of presuckle piglets with myoclonia congenita. Lesions and virus detectable in hearts of aborted or mummified fetuses. |
|
Brucella suis |
Infertility common. Any manifestation of reproductive failure may occur. Abortions at any stage of pregnancy. In adults, lameness or paralysis. In older boars, orchitis. | Disease nearing eradication in the US. A serious zoonosis. Diagnosis by various serologic tests. |
| * |
Other less likely causes of reproductive failure include influenza, inclusion body rhinitis, classical swine fever, African swine fever, Japanese B encephalitis, and virulent enteroviral infections. Sporadic microbiologic causes include miscellaneous bacterial infections. Mycotoxins in feed are anecdotally reported but not proven. Any acute generalized illness during advanced pregnancy can lead to abortion. |
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| Key: | CNS-central nervous system IFAT-immunofluorescent antibody test IHC-immunohistochemistry PCR-polymerase chain reaction |