Failure of Pregnancy in Pigs

Rob Foster

University of Guelph

Noninfectious

Idiopathic noninfectious Mummification

Mummification usually occurs after day 34 of pregnancy when bones begin to ossifying.
The rate of mummification is reported to be between 1 and 4% of normal litters. It is important to exclude infectious causes of mummification, particularly porcine parvovirus infection. When infectious causes are excluded, the associations between mummification and production parameters includes a greater number with a greater number of piglets per litter, higher parity and certain breed and line characteristics. The greater the number of piglets in the uterus and the more crowded they are, the higher the likelihood of mummification.

Dron N, Hernández-Jover M, Doyle R, Holyoake P. (2014) Investigating risk factors and possible infectious aetiologies of mummified fetuses on a large piggery in Australia. Aust Vet J 2014; 92: 472-478.

Chromosomal aberations

Chromosomal abnormalities are reported in different countries and in France selection is against chromosomal abnormalities. In Spain it is 3.8% of breeding pigs.

 

Sánchez-Sánchez R, Gómez‐Fidalgo E, Pérez‐Garnelo S, Martín‐Lluch M, De la Cruz‐Vigo P. Prevalence of chromosomal aberrations in breeding pigs in Spain. Reprod Dom Anim. 2019; 54(Suppl. 4): 98–101.

 

 

Infectious

Field studies

Salogni et al (2016) reported on a study of prevalence of reproductive failure in pigs in Italy, concentrating on infectious causes. They studied 549 cases of abortion and found 323 infectious cases (59%). There were 1625 fetuses in total. They found the following agents in the 323 cases:

Viruses

  1. Porcine circovirus-2 - 138 cases
  2. Porcine reproductive and respiratory syndrome virus - 108 cases
  3. Porcine parvovirus - 20 cases
  4. pseudorabies virus - 6 cases
  5. Encephalomyosarditis virus 3 cases

Bacteria

  1. Escherishia coli - 64 cases
  2. Streptococcus - 63 cases
  3. Staphylococcus - 5 cases
  4. Pasteurella - 3 cases
  5. Shigella - 1 case
  6. Yersinia - 1case

 

Salogni C, Lazzaro M, Giacomini E, Giovannini S, Zanoni M, Giuliani M, Ruggeri J, Pozzi P, Pasquali P, Boniotti MB, Alborali GL. Infectious agents identified in aborted swine fetuses in a high-density breeding area: a three-year study. J Vet Diagn Invest. 2016; 28: 550-554.

Bacteria

Brucella abortus

Brucella mellitensis

Brucella suis

There are many biovars of B suis. Biovar 1 to 3 affects pigs, biovar 4 reindeer, artic fox, wolf and cattle, and biovar 5 infects rodents. Of the porcine biovars, biovar 2 is in Europe. Biovar 1 and 3 are worldwide. All biovars are potentially zoonotic. They infect males and female and cause reproductive disease.

Porcine brucellosis is caused by Brucella suis. THere are 3 main biovars numbered 1 to 3. B suis is eradicated from the production swine herds in many countries. It causes disease is feral pig populations, hunting dogs and in countries where eradication is either not possible or is reemerging.

Rebollada-Merino et al (2023) reported on an outbreak of biovar 2 in a piggery. Four of the sows that aborted had fetuses and placentas from 2 piglets per sow examined. The lesions were in all placentas where there was tissue death and inflammation of the chroionic villi. Hemorrhage in the chorionic villi is prominent. Cells include macrophages, neutrophils and lymphocytes. The lymphocytes were CD3 positive. Brucella antigen was detected in the trophoblasts but there was no indication of visible bacteria by routine microscopy. All cases had hemorrhage in the umbilical cords particularly around the vessels. In the aborted piglets, two of 8 piglets had neutrophils and necrotic debris within bronchioles and alveoli in the lungs. All piglets had neutrophilic foci in the livers and there was focal necrosis in some. There was focal hemorrhage in the brain, heart and kidney.

Rebollada-Merino A, García-Seco T, Pérez-Sancho M, Domínguez L, Rodríguez-Bertos A. Histopathologic and immunohistochemical findings in the placentas and fetuses of domestic swine naturally infected with Brucella suis biovar 2. J Vet Diagn Invest. 2023; 35: 258-265.

 

Chlamydia abortus

There are some authors who believe that Chlamydias have an important role in porcine failure of pregnancy. Others do not.

Salinas et al (2012) thought they might. Outbreaks are possible.

Koschwanez et al (2012) thought not.

Salinas J, Ortega N, Borge C, Rangel MJ, Carbonero A, Perea A, Caro MR. (2012) Abortion associated with Chlamydia abortus in extensively reared Iberian sows. The Veterinary Journal 2012, 194: 133–134

Koschwanez M1, Meli M, Vögtlin A, Greub G, Sidler X, Handke M, Sydler T, Kaiser C, Pospischil A, Borel N. Chlamydiaceae family, Parachlamydia spp., and Waddlia spp. in porcine abortion. J Vet Diagn Invest 2012; 24: 833-839

Erysipelothrix rhusiopathiae

Escherishia coli

Leptospira

Mycobacterium spp

Mycobacterium fortuitum

Cole et al (2022) report on a single pregnancy where 2 piglets had M. fortuitum recovered and histologic lesions in the placenta and lungs.

Cole AL, Kirk NM, Wang L, Hung CC, Samuelson JP. Mycobacterium fortuitum abortion in a sow. J Vet Diagn Invest. 2022; 34: 116-120.

Parachlamydia acanthomoebae

Streptococcus

Staphylococcus

 

Virus

Family Circoviridae, Genus Circovirus, Porcine circovirus-2 (PCV-2)

Family Arteriovirus: Porcine reproductive and respiratory syndrome virus (PRRSV)

PRRSV causes late term abortion in pigs. There are inconsistent lesions in the placenta or fetus. There may be placental vasculitis and placentitis.

Lesions are present in the uterus, however. There is myometritis, endometrial vasculitis and endometritis, leading to fetal death and placental separation.

 

Novakovic P, Detmer SE, Suleman M, Malgarin CM, MacPhee DJ, Harding JCS. Histologic Changes Associated With Placental Separation in Gilts Infected with Porcine Reproductive and Respiratory Syndrome Virus. Vet Pathol 2018; 55: 521-530.

Porcine parvovirus

Suid herpesvirus 1 Pseudorabies virus

Encephalomyosarditis virus

 

Classical swine fever virus