Swine Influenza in Sri Lanka

Abstract

To study influenza viruses in pigs in Sri Lanka,we examined samples from pigs at slaughterhouses. Influenza (H3N2) and A(H1N1)pdm09 viruses were prevalent during 2004–2005 and 2009–2012, respectively. Genetic and epidemiologic analyses of human and swine influenza viruses indicated 2 events of A(H1N1)pdm09 virus spillover from humans to pigs.

Transmission dynamics of pandemic influenza A(H1N1)pdm09 virus in humans and swine in backyard farms in Tumbes, Peru

“…The pH1N1 virus was introduced into the swine population within 3 months of the first reported human case in the region by the Peruvian Ministry of Health on July 1, 2009. Similar time lags between human and swine infection have been noted in studies of humans and swine on backyard farms in Vietnam, Sri Lanka, and Cameroon 5, 8, 14. The increase in antibody prevalence (24%) in swine during the first post‐pandemic period, in which most pigs sampled were 6–8 months old, likely represents human‐to‐swine infections that occurred during the peak of the human influenza pandemic and possibly limited onward transmission of pH1N1 in swine.…”

“…Although experimental infections in the laboratory confirm the potential for pH1N1 virus shedding and contact transmission between swine,20, 40 most field investigations suggest that sustained transmission among swine is limited in small‐scale farm settings5, 14 although, as infection is often subclinical or associated with mild disease,4, 9 it may go undetected 40. Consistent with this, none of the swine in our study were noted to be sick prior to slaughter and no abnormalities were noted on gross anatomic examination of the lungs of the three virus‐positive animals.…”

“…The influenza A(H1N1)pdm09 virus (pH1N1) was first identified among humans in March 2009 and generated the first pandemic of the 21st century 3. Since 2009, pH1N1 has become endemic in human populations globally and there have been numerous reports of human‐to‐swine transmission 1, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20. Most of these reports, however, have focused on larger scale industrial farms,4, 7, 11, 18 as opposed to smaller scale backyard farms, despite the fact that large numbers of pigs are raised in backyard settings, particularly in developing countries, providing considerable opportunity for influenza virus transmission between humans and livestock 21, 22…”

Continual Reintroduction of Human Pandemic H1N1 Influenza A Viruses into Swine in the United States, 2009 to 2014

“…Since 2009, pH1N1 viruses and pH1N1 reassortants (i.e., viruses with at least one segment of pH1N1 origin) have been identified in swine populations in the Americas (United States [20], Canada [21], Mexico [22], Argentina [6], Brazil [23], and Colombia [24]), Europe (United Kingdom [25], Germany [26], Norway [8], and Italy [27]), Asia (China [3], South Korea [28], Sri Lanka [10], Thailand [29], and Vietnam [7]), Africa (4), and Australia (5). We previously estimated that the pH1N1 virus was introduced at least 49 times from humans to swine on a global scale (9).…”

“…Of particular note is the number of times humans have transmitted pandemic H1N1 influenza A (pH1N1) viruses to swine on multiple continents since 2009 (3)(4)(5)(6)(7)(8). A global estimate of 49 discrete introductions of pH1N1 viruses from humans to swine from 2009 to 2012 is likely an underestimate (9), and increased surveillance efforts in swine continue to identify additional introductions of pH1N1 viruses from humans to swine globally (10).…”