Swine Influenza Virus and Association with the Porcine Respiratory Disease Complex in Pig Farms in Southern Brazil.

Despite the putative endemic status of swine influenza A virus (swIAV) infections, data on the occurrence of swine influenza outbreaks are scarce in Brazil. The aim of this study was to detect and subtype swIAVs from six outbreaks of porcine respiratory disease complex (PRDC) in southern Brazil. Nasal swabs were collected from 66 piglets with signs of respiratory disease in six herds. Lung tissue samples were collected from six necropsied animals. Virus detection was performed by PCR screening and confirmed by virus isolation and hemagglutination (HA). Influenza A subtyping was performed by a real-time reverse transcriptase PCR (rRT-PCR) to detect the A(H1N1)pdm09; other swIAV subtypes were determined by multiplex RT-PCR. In lung tissues, the major bacterial and viral pathogens associated with PRDC (Pasteurella multocida, Mycoplasma hyopneumoniae, Actinobacillus pleuropneumoniae, Haemophilus parasuis and PCV2) were investigated. In some affected pigs, clinico-pathological evaluations were conducted. Influenza A was detected by screening PCR in 46 of 66 swab samples and from five of six lungs. Virus was recovered from pigs of all six herds. Subtype A(H1N1)pdm09 was detected in four of six herds and H1N2 in the other two herds. In lung tissues, further agents involved in PRDC were detected in all cases; Pasteurella multocida was identified in five of six samples and Mycoplasma hyopneumoniae in three of six. Actinobacillus pleuropneumoniae (1/6), Haemophilus parasuis (1/6) and PCV2 (1/6) were also detected. These findings indicate that subtypes A(H1N1)pdm09 and H1N2 were present in pigs in southern Brazil and were associated with PRDC outbreaks.

Differentiation of classical swine fever virus from ruminant pestiviruses by reverse transcription and polymerase chain reaction (RT-PCR).

A reverse transcriptase-polymerase chain reaction (RT-PCR) assay was designed to allow the differentiation of pestiviruses by the expected size of the amplified fragments. One oligonucleotide primer, conserved amongst pestiviruses, and two others specific for either classical swine fever virus (CSFV) or bovine viral diarrhea virus (BVDV), were designed from the 5' non-coding region of the genome. CSFV infected cultures (10 strains) amplified a fragment of an expected size of 200 bp; BVDV cultures (23 strains) or border disease virus (BDV) (2 strains) amplified a fragment of an expected size of 260 bp. The specificity of the amplified fragments was confirmed by restriction enzyme analysis. The threshold of sensitivity was 100 TCID50 for CSFV and 1 TCID50 for BVDV. The RT-PCR described here provides a rapid and sensitive diagnostic tool for the detection and differentiation of CSFV from ruminant pestiviruses.