A high percentage of piglets become infected with porcine circovirus type 2 (PCV2) due to vertical transmission of the virus from sows to piglets during gestation. This means at birth a portion of the piglets have antibodies to PCV2 or are actively infected with PCV2 prior to colostrum uptake.

The objective of this study was to assess the prevalence of intrauterine PCV2 infection in healthy-looking, newborn piglets in five breeding herds in the United States and Mexico.

A total of 125 sows and 3-5 neonatal piglets/sow were selected. Blood and colostrum samples were collected from sows. Blood was collected from piglets prior to suckling.

All samples collected were analyzed for the presence of anti-PCV2 IgG antibodies and PCV2 DNA. PCV2 DNA-positive samples were further subtyped into PCV2a and PCV2b.

All (125/125) sow colostrum samples and 96.8% (121/125) of the sow serum samples and 21.4% (107/499) of the piglet pre-suckle serum samples were positive for anti-PCV2 IgG antibody.

The overall PCV2 DNA prevalence was 47.2% (59/125) in sow serum, 40.8% (51/125) in sow colostrum and 39.9% (199/499) in pre-suckle piglet serum.

In the PCV2 DNA-positive samples, PCV2b was detected at a higher rate — 69.5% for sow serum, 84.3% for sow colostrum and 74.4% for piglet serum. In comparison, PCV2a was detected in 18.6% of sow serum, 9.8% of sow colostrum and 15.6% of piglet serum.

Concurrent PCV2a and PCV2b infection was found in 11.9% of sow serum, 5.9% of colostrum samples and in 10.0% of the piglet serum samples.

Researchers concluded that an unexpectedly high prevalence of PCV2 viremia (infection in the bloodstream) was detected in healthy sows (serum and colostrum) and their pre-suckle piglets in the five breeding herds investigated.

Studies are currently underway to determine the effectiveness of vaccinating the sows prior to breeding to prevent intrauterine infection with PCV2.

Researchers: H. Shen, C. Wang, D. Madson and T. Opriessnig, Iowa State University. Contact Opriessnig by phone (515) 294-1950, fax (515) 294-6961 or e-mail tanjaopr@iastate.edu.