Emergency surveillance for novel influenza A(H7N9) virus in domestic poultry, feral pigeons and other wild birds in Bhutan

Abstract

Following the March 2013 outbreak of novel avian influenza A(H7N9) virus in humans and the subsequent isolation of the virus from chickens, ducks and pigeons in the People's Republic of China, concerns were raised that the H7N9 virus would spread beyond China through the poultry value chain linking to a number of bordering countries. For this reason, a rapid emergency surveillance exercise took place in Bhutan between May and July 2013 with the objective of determining whether influenza A(H7N9) virus was silently circulating in domestic poultryandwild birds in Bhutan.Atotal of 1716 oropharyngeal,tracheal and cloacal swabs together with faecal droppings were collected from poultry, wild birds and feral pigeons throughout the country; these samples included 150 that had been previously collected for surveillance of influenza A(H5N1) virus. Overall, 733 of the samples were tested. A QIAamp Viral RNA Mini K it was used to extract viral RNA from a mix of oropharyngeal, tracheal and cloacal swabs and faecal droppings. The matrix gene of avian influenza type A virus was detected using a specific real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR) assay, and positive samples were further tested in RT-PCR for simultaneous detection of the H7 and N9 genes. Among the 733 samples tested, 46 (26 prospective, 20 retrospective) were confirmed positive for influenza A, a prevalence of 6.3% (95% CI: 4.6 to 8.3). The influenza A-positive samples were from areas in the south of Bhutan that had experienced previous outbreaks of highly pathogenic influenza A(H5N1). None of the samples tested positive for H7N9 strains, providing evidence that influenza A(H7N9) virus was not present in the sampled population. A risk-based approach for surveillance of influenza A(H7N9) and H5N1 is recommended in Bhutan, based on the epidemiology of the disease in China and other countries in South and Southeast Asia.