Sero-epidemiology of porcine parvovirus, circovirus, and classical swine fever virus infections in India.

Reproductive problems in swine caused by porcine viruses pose a serious threat to the pig industry in developing countries like India. For evaluating the true extent of porcine infections, a total of 1308 representative sera samples were collected from 92 different pig farms covering 8 North-Eastern states and Punjab state of Northern India during a period of 2 years (2011-2013). Sera samples were tested for the presence of antibodies against porcine parvovirus (PPV), porcine circovirus-2 (PCV-2), and classical swine fever virus (CSFV) using commercial enzyme-linked immunosorbent assay (ELISA) kits. In the North-Eastern states, the seroprevalence of CSFV in non-vaccinated animals was 6.30% and that of PCV2 and PPV was 6.28% and 1.24%, respectively. In Punjab, the seroprevalence of CSFV in non-vaccinated animals was 44.44% and seroprevalence of PCV-2 and PPV was 34.07% and 39.10%, respectively. Detection of antibodies against more than one virus revealed that 4.66% animals had co-infection with PCV-2 and PPV, 1.75% with CSF and PPV, 1.98% with CSF and PCV-2, and 1.75% with all the three viruses. The receiver operator characteristics (ROC) curve analysis depicted that piglet mortality, parvovirus, and CSFV were the most important parameters with an AUC value of 0.997, 0.897, and 0.973, respectively. Incidence of single or co-infection with different viruses showed that the occurrence of single infection was significantly more prevalent than co-infection. This study provides useful information to set up future epidemiologic, flock management, and public animal health policies for the prevention and control of PCV-2, PPV, and CSF in India.

Molecular characterization of classical swine fever virus isolates from India during 2012-14.

Classical swine fever is a highly contagious and economically important viral disease of pigs. Outbreaks of classical swine fever virus (CSFV) were recorded in different places in the Kamrup district of Assam in India between the years 2012 and 2014. The nucleotide sequences of the 10 CSFV isolates were analyzed based on the partial nucleotide sequences of the E2, 5'NTR and NS5B genes. Phylogenetic analysis indicated the dominance of subgroup 2.2 along with 2.1 strains in the northeast part of India. Variation in the nucleotide sequences of E2, 5'NTR and 3'NS5B genes of CSFV allows tracking changes in the virus population over time. The study will provide epidemiological information useful for assessing CSFV circulating genogroups in India.

Molecular characterization of E2 glycoprotein of classical swine fever virus: adaptation and propagation in porcine kidney cells.

Classical swine fever virus (CSFV) is the causative agent of a highly contagious disease, hog cholera in pigs. The disease is endemic in many parts of the world, and vaccination is the only way to protect the animals from CSFV infection. The lapinized vaccine strains are occasionally not protective because of animal to animal passage, inadequate vaccination strategy, suboptimal vaccine dose, and emergence of new variants. The surface glycoprotein E2 of CSFV is a major antigenic determinant and can modulate the disease outcome in pigs. In the present study, we characterized the CSFV in porcine kidney cells. The CSFV vaccine strains showed enhanced replication following 15 passages in porcine kidney cells. Nucleotide sequence analysis of the E2 protein gene of the cell culture-adapted vaccine strain of CSFV showed a mutation in putative amino acid sequences that are identical to its virulent counterpart. The study suggests the possibility of exaltation in vaccine strains following its adaptation in host cells and paves the way for a further exploration of the biology of its outbreak.