Etiology, Pathogenesis and Diagnosis
Parvovirus is a very common and important cause of infertility in sows of first pregnancy worldwide. This condition is caused by a DNA single-stranded no enveloped virus; therefore it is very resistant to environmental conditions, for several months, and most disinfectants.
This virus replicates in the intestine without causing clinical signs in pigs for fattening or rearing. Infected sows are immunized replacement, but when the infection occurs during the first pregnancy and they are not previously immunized, the virus causes different problems depending on the stage of fetal development. These reproductive problems are common during the first and second pregnancy, but after the bristles have lifelong immunity and subsequent deliveries will be normal.
The route of transmission is by air or even less frequently sexually and the incubation period is usually about 10 days. In pregnant sows, the virus passes from one end of the uterine horn form continues producing fetal death, and this step of a fetus to another happens approximately every 4 days.
If infection occurs before day 35 fetuses resorbed therefore a high percentage of repetitions. When infection occurs between 35 and 70 days of gestation they will be mummified fetuses in different sizes, as in this case have formed the skeleton. But after 70 days fetuses are immunocompetent and born normally. The maternal immunity lasts about 4 to 6 months in animals born from infected sows.
Therefore, with this infection occur various problems such as:
- Cyclic and acyclic depending on the time of infection Reps per embryo resorption
- Few live piglets
- Expulsion of mummified fetuses
- Infertility occasionally
The clinical diagnosis is made by observing reproductive problems, such as repetitions, the presence of small litters and mummified animals of different sizes and the absence of abortions. So, if they appear stillborn from day 70 it would not be because of Parvovirus. The differential diagnosis should always be compared with PRRS. Other diseases which appear in mummified piglets are Classical Swine Fever and Aujeszky.
The laboratory diagnosis is viral detection or serology:
- Viral Detection: It is better to detect the presence of the virus in dead or mummified fetuses, because the bristles can be positive for developing vaccination or infection before pregnancy. Virus detection can be done mainly by ELISA fetal capture, PCR or immunohistochemistry macerated.
- Serology (ELISA, hemagglutination inhibition): Serological analysis should be done in live piglets before giving colostrum or in the bristles to see seroconversion.