ABSTRACT
Classical swine fever (CSF) is a highly contagious dreadful disease of pigs leading to 100% mortality in acute form in susceptible population thereby causing huge economic loss to pig farmers. This study was undertaken to assess the seroprevalence of CSF at national level. A two-stage random sampling methodology was adopted that included 271 villages from 115 districts of India. A total of 5848 pig serum samples from twenty-five states and one Union Territory of India were collected during 2018-2019. A percent positivity of 38.52 was found at national level. Puducherry and Sikkim showed the highest and lowest percent positivity respectively. Pigs from the west zone showed the highest seroprevalence of 55.83% and those from the south zone showed the lowest of 30.25%. Adult pigs in the north and east zones showed highest percent positivity of 81.8, whereas pigs of more than 3 years of age showed highest percent positivity of 54.9, 75 and 62.5 in the north east, west and central zones respectively. Young ones showed percent positivity of 41.5 in the south zone. Higher rainfall (> 3 mm/day) and lower temperature (< 26 °C) favoured the existence of disease in the north east region combined with high density of pig population. Amidst no fool proof alert system, seroprevalence is the best method to assess the status of CSF in herd/population that provides the policymakers to plan for control of disease.
Subject(s)
Classical Swine Fever Virus , Classical Swine Fever , Swine Diseases , Animals , India , Seroepidemiologic Studies , Sikkim , SwineABSTRACT
South Asia has experienced regular outbreaks of H5N1 avian influenza virus since its first detection in India and Pakistan in February, 2006. Till 2009, the outbreaks in this region were due to clade 2.2 H5N1 virus. In 2010, Nepal reported the first outbreak of clade 2.3.2 virus in South Asia. In February 2011, two outbreaks of H5N1 virus were reported in the State of Tripura in India. The antigenic and genetic analyses of seven H5N1 viruses isolated during these outbreaks were carried out. Antigenic analysis confirmed 64 to 256-fold reduction in cross reactivity compared with clade 2.2 viruses. The intravenous pathogenicity index of the isolates ranged from 2.80-2.95 indicating high pathogenicity to chickens. Sequencing of all the eight gene-segments of seven H5N1 viruses isolated in these outbreaks was carried out. The predicted amino acid sequence analysis revealed high pathogenicity to chickens and susceptibility to the antivirals, amantadine and oseltamivir. Phylogenetic analyses indicated that these viruses belong to clade 2.3.2.1 and were distinct to the clade 2.3.2.1 viruses isolated in Nepal. Identification of new clade 2.3.2 H5N1 viruses in South Asia is reminiscent of the introduction of clade 2.2 viruses in this region in 2006/7. It is now important to monitor whether the clade 2.3.2.1 is replacing clade 2.2 in this region or co-circulating with it. Continued co-circulation of various subclades of the H5N1 virus which are more adapted to land based poultry in a highly populated region such as South Asia increases the risk of evolution of pandemic H5N1 strains.
