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Year : 2013  |  Volume : 138  |  Issue : 2  |  Page : 267-269

Seroprevalence of pandemic influenza H1N1 (2009) & seasonal influenza viruses in pigs in Maharashtra & Gujarat States, India, 2011

1 National Institute of Virology-Microbial Containment Complex, 131/1, Sus Road, Pashan, Pune 411 021; Bombay Veterinary College, Parel, Mumbai 400 012, India
2 National Institute of Virology-Microbial Containment Complex, 131/1, Sus Road, Pashan, Pune 411 021, India
3 Bombay Veterinary College, Parel, Mumbai 400 012, India

Date of Web Publication3-Sep-2013

Correspondence Address:
Shailesh D Pawar
National Institute of Virology-Microbial Containment Complex, 131/1, Sus Road, Pashan, Pune 411 021
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Source of Support: None, Conflict of Interest: None

PMID: 24056606

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How to cite this article:
Sabale SS, Pawar SD, More BK, Mishra AC. Seroprevalence of pandemic influenza H1N1 (2009) & seasonal influenza viruses in pigs in Maharashtra & Gujarat States, India, 2011. Indian J Med Res 2013;138:267-9

How to cite this URL:
Sabale SS, Pawar SD, More BK, Mishra AC. Seroprevalence of pandemic influenza H1N1 (2009) & seasonal influenza viruses in pigs in Maharashtra & Gujarat States, India, 2011. Indian J Med Res [serial online] 2013 [cited 2021 Jul 24];138:267-9. Available from:


Pandemic influenza H1N1 (2009) virus (H1N1pdm) was reported for the first time in Mexico in March 2009. Pandemic of influenza was declared by the World Health Organization (WHO) on June 2009 as the virus was reported in several countries within a short period of time [1] . India also reported cases of pandemic H1N1 from various States [2] . The Centers for Disease Control and Prevention, Atlanta, USA, reported swine originated variant of influenza H3N2 virus in humans which has been linked to pig exposure. This virus showed matrix M gene from 2009 H1N1pdm virus which might make it easily transmissible in humans [3] . The pigs are an important host in influenza virus ecology since they are susceptible to infection with both avian and human influenza virus strains [4] . Pigs express both sialic acid (SA) linked to galactose (Gal) by α-2,3 linkage (SA α-2,3-Gal) and α-2,6 receptors (SA α-2,6-Gal), preferred by avian and human influenza viruses, respectively [5] .

There are no reports of seroprevalence studies of pandemic influenza H1N1 (2009) virus in pigs from India after emergence of pandemic influenza virus. Therefore, the present study was undertaken to explore transmission of H1N1pdm and other influenza viruses in pigs in Maharashtra and Gujarat States. During this study serum samples were taken from apparently healthy pigs of around 6-7 month of age at an abattoir in Mumbai, Maharashtra. A total of 925 serum samples were collected in 16 visits to an abattoir during May to August 2011. The sample represented 30 per cent of the total slaughtered pig population. The limitation of study was the limited number of samples screened. Hence, the study did not represent the total pig population in Maharashtra and Gujarat. Pigs were randomly received at an abattoir from different locations and piggeries. The samples were from 11 districts of Maharashtra and five districts of Gujarat State [Table 1]. Antibodies to influenza viruses were detected by haemagglutination inhibition (HI) assay [6] . HI antibody titre of ≥ 20 was considered seropositive. Three influenza viruses namely H1N1pdm (A/Jalna/NIV9436/2009) similar to A/California/04/2009, seasonal H1N1 similar to A/New Caledonia/20/99 and H3N2 similar to A/Perth/16/2009 were used as antigens for detection of antibodies in pig serum samples. Influenza virus strains used in this study were isolated and grown in the allontoic cavity of 10 day-old embryonated chicken eggs [6] at the National Institute of Virology (NIV), Pune. The reference hyperimmune serum samples of each subtype, raised in chickens at NIV were used as positive controls. Seroprevalence was estimated and reported as percentages with 95% confidence intervals (CI). As this was exploratory study, the seropositivity was not analyzed district-wise; hence district-wise sample size analysis was not done. Geometric mean titre (GMT) of antibody was estimated for each antigen and CI was calculated using of Nby2 software developed by the Statistics Unit at the NIV, Pune.
Table 1: District-wise sample collection from an abattoir

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A total of 37.8 (C.I. 34.71, 40.96), 29 (C.I. 26.05, 31.81) and 0.3 per cent (C.I. 0, 0.69) serum samples were positive for antibodies against H1N1pdm, H3N2 and seasonal H1N1 viruses, respectively. The GMT of HI antibody indicated high antibody titres against H1N1pdm followed by H3N2 virus [Figure 1]. A total of 12.5 per cent (C.I. 10.41, 14.67) serum samples were positive for antibodies against both H1N1pdm and H3N2 viruses; 0.1 per cent (C.I. 0, 0.32) serum samples were positive for antibodies against both H1N1pdm and seasonal H1N1 viruses.
Figure 1: Percentages of positive serum samples and geometric mean titres of antibodies against pandemic influenza H1N1 (2009), influenza A (H3N2) and seasonal influenza (H1N1) viruses.

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Earlier reports from India have shown prevalence of antibodies against influenza viruses in pigs [7],[8],[9] . H1N1pdm virus was isolated from pigs in north India in 2009, after emergence of H1N1pdm virus in India [10] . In Maharashtra and Gujarat States, stray pig population is predominant and these animals wander in backyard. The piggery farms are semi-organized and pigs are reared in backyard. It has been estimated that influenza virus infection results in weight loss in pigs [11] . Therefore, swine influenza might be of substantial economic concern for farmers, and there is a growing concern of the impact of synergistic infections with influenza and other respiratory viruses [12] . The higher antibody positivity against H1N1pdm was followed by influenza H3N2 virus. As influenza vaccination is not practiced in pigs in India, the antibody positivity indicates influenza virus infection in recent past. A very small percentage of samples showed antibodies against seasonal influenza H1N1 virus, indicating predominant circulation of H1N1pdm virus. Also, antibodies to both H1N1pdm and H3N2 viruses indicate co-circulation of these both viruses in pigs.

India reported outbreaks of highly pathogenic avian influenza H5N1 virus in poultry [13] and prevalence of avian influenza H9N2 has been reported from poultry markets [14] . Rearing of pigs in backyard provides an opportunity of intermingling of pigs with backyard poultry which might provide opportunities for reassortant influenza viruses. Therefore, the present study highlights need of influenza surveillance in pig population in India.

   Acknowledgment Top

Authors thank M.R. Khude, S.K. Waghmare, J.P.N. Babu, Drs Aniket Mahse, Shrikrishna Waval, Ajay Masture, Shivali Gaikwad, D.P. Kadam, S.S. Koratkar, Avian influenza staff, and Dr B.V. Tandale for support in field and laboratory work, and the Indian Council of Medical Research, Government of India, New Delhi, for the financial support.

   References Top

1.Centers for Disease Control and Prevention (CDC). Outbreak of swine-origin influenza A (H1N1) virus infection - Mexico, March-April 2009. MMWR Morb Mortal Wkly Rep 2009; 58 : 467-70.  Back to cited text no. 1
2.Tandale BV, Pawar SD, Gurav YK, Chadha MS, Koratkar SS, Shelke VN, et al. Seroepidemiology of pandemic influenza A (H1N1) 2009 virus infections in Pune, India. BMC Infect Dis 2010; 10 : 255.  Back to cited text no. 2
3.Centers for Disease Control and Prevention (CDC). Interim information for clinicians about human infections with H3N2v virus. 14 September 2012. Available from: , accessed on September 8, 2012.  Back to cited text no. 3
4.Wentworth DE, McGregor MW, Macklin MD, Neumann V, Hinshaw VS. Transmission of swine influenza virus to humans after exposure to experimentally infected pigs. J Infect Dis 1997; 175 : 7-15.  Back to cited text no. 4
5.Wright PF, Neumann G, Kawaoka Y. Orthomyxoviruses. In: Howley DM, Peter M, editors. Fields virology, 5 th ed. Philadelphia: Lippincott Williams & Wilkins; 2007. p. 1693-739.  Back to cited text no. 5
6.World Health Organization (WHO). WHO Manual on animal influenza diagnosis and surveillance, WHO/CDS/CSR/NCS/ 2002.5. Geneva, Switzerland: WHO; 2002.  Back to cited text no. 6
7.Chatterjee S, Mukherjee KK, Mondal MC, Chakravarti SK, Chakraborty MS. A serological survey of influenza A antibody in human and pig sera in Calcutta. Folia Microbiol (Praha) 1995; 40 : 345-8.  Back to cited text no. 7
8.Kelkar SD, Banerjee K. Serological evidence of infection with H1N1 subtype of influenza virus at Dibrugarh, Assam. J Commun Dis 1981; 13 : 248-52.  Back to cited text no. 8
9.Rao BL, Khan FU, Bhat HR, Kadam SS. Zoonotic studies on influenza in pigs and birds, India, 1980-81. Int J Zoonoses 1983; 10 : 40-4.  Back to cited text no. 9
10.Nagarajan K, Saikumar G, Arya RS, Gupta A, Somvanshi R, Pattnaik B, et al. Influenza A H1N1 virus in Indian pigs & its genetic relatedness with pandemic human influenza A 2009 H1N1. Indian J Med Res 2010; 132 : 160-7.  Back to cited text no. 10
11.Easterday BC, Hinshaw VS. Swine influenza. In: Leman AD, Straw BE, Mengeling WL, D′Allaire SD, Taylor DJ, editors. Diseases of swine. Iowa City, Iowa, USA: Iowa State Press; 1992. p. 349-57.  Back to cited text no. 11
12.Kay RM, Done SH, Paton DJ. Effect of sequential porcine reproductive and respiratory syndrome and swine influenza on the growth and performance of finishing pigs. Vet Rec 1994; 135 : 199-204.  Back to cited text no. 12
13.Chakrabarti AK, Pawar SD, Cherian SS, Koratkar SS, Jadhav SM. Characterization of the influenza A H5N1 viruses of the 2008-09 outbreaks in India reveals a third introduction and possible endemicity. PLoS ONE 2009; 4 : e7846.  Back to cited text no. 13
14.Pawar SD, Kale SD, Rawankar AS, Koratkar SS, Raut CG, Pande SA, et al. Avian influenza surveillance reveals presence of low pathogenic avian influenza viruses in poultry during 2009-2011 in the West Bengal State, India. Virol J 2012; 9 : 151-7.  Back to cited text no. 14


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