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Reproduction

PCV2 Associated Abortions and Reproductive Failure

PCV2-associated reproductive failure has been reported primarily in gilt litters. The dams typically are not sick and fetuses may be delivered weak born, fresh but dead, or in varying stages of autolysis and/or mummification.

There have been several reports (O’Conner et al., 2001; Ladekjær-Mikkelsen et al. 2001) of PCV2-associated reproductive failure since the original report of West et al. (1999) in western Canada in 1999. Consistent signs on affected farms include increased numbers of abortions, stillbirths, fetal mummification, and increased pre-weaning mortalities. Affected herds are typically gilt-start-ups or new populations. A nonsuppurative-to-necrotizing or fibrosing myocarditis associated with abundant PCV2 antigen are the major lesions in stillborn and neonatal pigs from field cases (Mikami et al., 2005). PCV2-infection has been confirmed in PMWS outbreaks in CDCD piglets (Harms et al., 1999; Jolie et al., 2000) suggesting that a vertical transmission is possible. Experimental intrauterine infection of fetues with PCV2 resulted in virus replication in the fetuses and supports the heart as primary site of PCV2 replication in fetuses (Sanchez et al. 2001). Johnson et al. (2002) inoculated 37 fetuses from 3 pregnant sows at 86, 92, and 93 days of gestation intramuscularly and observed 24 normal pigs and 13 mummified, stillborn, or weak-born pigs at farrowing confirming that PCV2 can infect late-term fetuses and cause reproductive abnormalities.

The most commonly reported PCV2-associated gross lesion is increased incidence of mummified fetuses. Confirmation of the diagnosis is dependent on finding PCV2-associated lesions and antigen (brown staining) in the heart of aborted fetuses.
 

A retrospective study failed to detect PV2 antigen and nucleic acids in cases of reproductive failure prior to 1999 in areas of endemic PCV2 infection (Bogdan et al. 2001). The authors concluded that reproductive failure may be a new clinical manifestation of PCV2 infection, and that vertical transmission may not have been the primary mechanism of initial dissemination of the virus in the pig population. Farnham et al. (2003) tested 171 sera from stillborn fetuses from 3 different farms for PCV2-specific antibodies by IPMA and found 28 of 171 positive. Thirteen of the 28 sera were also positive for PCV2 nucleic acids as determined by PCR, and 9 of 13 PCR PCV2 positive sera were positive for PCV2 by virus isolation. Kim et al. (2004b) tested 350 aborted fetuses and stillborn pigs from 321 Korean farms submitted between 2000 and 2002 for PCV2, PPV, and PRRSV by PCR and virus isolation. PCV2 was found by PCR in 46 of 350 (13.1%) fetuses and by virus isolation in 25 of 350 (7.1%) fetuses and it was associated with all stages of gestation.

Mauch et al. (2004) observed abortions and death loss in dams after 94 gilts in mid-pregnancy were transported to four PCV2 positive farms. Pensaert et al. (2004) inoculated four 8-month-old nonpregnant gilts with a PCV2 strain isolated from a dead fetus in Canada. The gilts seroconverted to PCV2 by 21 DPI. Viral DNA was found in plasma between 14 and 49 DPI and in peripheral blood monocytes between 7 and 63 DPI. The 21 DPI PCV2 was determined to be infectious by pig inoculation. Park et al. (2005) inoculated 6 pregnant sows 3 weeks before expected farrowing date intranasally with a PCV2 recovered from an aborted fetus. Four of the 6 sows aborted between 7 and 21 DPI and 2 sows farrowed 4-5 days prematurely. The six sows delivered a total of 65 stillborn and 10 live-born piglets. PCV2 DNA was detected by ISH in lymph node, spleen, thymus, lung, tonsil, and liver from stillborn and live-born piglets.

References:

Bogdan J, West K, Clark E, Konoby C, Haines D, Allan G, McNeilly F, Meehan B, Krakowka S, Ellis JA: Association of porcine circovirus 2 with reproductive failure in pigs: a retrospective study, 1995-1998. Can Vet J. 42:548-550, 2001

Farnham MW, Choi YK, Goyal SM, Joo HS: Isolation and characterization of porcine circovirus type-2 from sera of stillborn fetuses. Can J Vet Res. 67:108-113, 2003

Harms PA, Sorden SD, Rotto HF: Hepatopathy associated with spontaneous type 2 porcine circovirus infectin in caesarian derived/colostum deprived pigs. In: Proc Am Assoc Vet Lab Diagn. 42:4, 1999

Johnson CS, Joo HS, Direksin K, Yoon KJ, Choi YK: Experimental in utero inoculation of late-term swine fetuses with porcine circovirus type 2. J Vet Diagn Invest. 14:507-512, 2002

Jolie R, Runnels P, McGavin D: Post-weaning multisystemic wasting syndrome in a group of caesarian derived colostrums deprived pigs. In: Proc Int Conf Pig Vet Soc. 16:639, 2000

Kim J, Chae C: Concurrent presence of porcine circovirus type 2 and porcine parvovirus in retrospective cases of exudative epidermitis in pigs. Vet J. 167:104-106, 2004b

Ladekjær-Mikkelsen AS, Nielsen J, Storgaard T, Botner A, Allan G, McNeilly F: Transplacental infection with PCV-2 associated with reproductive failure in a gilt. Vet Rec. 148:759-760, 2001

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