Between 2007 and 2013 Bangladesh was a hot spot for H5N1, with nearly 550 poultry outreaks reported and millions of birds killed by the virus or culled. Since 2013, however, Bangladesh has not reported any new poultry outbreaks to the OIE.
In January of this year, the WHO reported `A 60-year-old male from Mymensing District in Bangladesh was hospitalized on 12 October 2015 with severe acute respiratory infection (SARI)' who tested positive for H5N1.
So while flying beneath the radar for a couple of years, it is apparent the H5N1 virus is still floating around Bangladesh.
Today the OIE reports that 40 dead crows, collected earlier this month from Rajshahi city, tested positive for the highly pathogenic H5N1 virus. The epidemiological source of the outbreak is somewhat enigmatically stated as `Eating of City waste'.
First some excerpts from the OIE report, then I'll be back with a bit more on previous murders of crows.
While waterfowl (ducks & geese) and gallinaceous birds (turkeys, grouse, chickens & quail) are most often associated with carriage of the H5N1 virus, terrestrial birds such as crows, starlings, pigeons, and sparrows are also known to carry, and shed, the virus as well (see 2007’s EID Journal Role of Terrestrial Wild Birds in Ecology of Influenza A Virus (H5N1).
As far back as 2008, we saw reports out of India of crows dying from the H5N1 virus. In 2012, and again in 2014 India saw numerous wild bird die offs that were blamed on the avian flu virus (see Media Report: H5N1 Killing Crows In Jharkhand).
As crows are omnivorous, they can not only contract the virus through contact with infected birds or contaminated water sources, but through the consumption of infected carrion. This may explain why crow reports are fairly common.
Because of the low expectations of finding HPAI H5 in non-aquatic birds, until the arrival of HPAI H5N2/H5N8 a year ago, passerine birds were rarely routinely tested in North America (see Surveillance Plan for the Early Detection of H5N1 Highly Pathogenic Avian Influenza Virus in Migratory Birds: 2009).
The revised plan (see APHIS/USDA Announce Updated Fall Surveillance Programs For Avian Flu) released during the summer of 2015, calls for much broader testing.
Although the incidence of terrestrial bird carriage of HPAI viruses is poorly understood and its significance remains hotly debated, recent studies and surveillance suggests their role may be greater than previously believed.
- The Survey of H5N1 Flu Virus in Wild Birds in 14 Provinces of China from 2004 to 2007, published in 2009, found 26 positive samples distributed across 9 species from among 7320 passerine samples tested, providing a very low incidence of 0.36%. However, among tree sparrows tested, the prevalence was three times higher at 1.09%.
- The 2012 PLoS One Study A Survey of Avian Influenza in Tree Sparrows in China in 2011, found serological evidence of prior H5 subtype HPAI infection in 94 of 800 (11.75%) of sparrows tested, showing that HPAI H5 infection need not always prove fatal in that species.
- In 2013, in Pathogenesis in Eurasian tree sparrows inoculated with H5N1 highly pathogenic avian influenza virus and experimental virus transmission from tree sparrows to chickens by Yamamoto Y, Nakamura K, Yamada M, Mase M., the authors found that inoculated birds lived up to 11 days and shed copious amounts of the virus during that time, and suggested that Eurasian tree sparrows could be potential vectors to housed poultry.
- And a 2015 study - Avian Path: Susceptibility of Wild Passerine Birds To HPAI H5N1 - examined the susceptibility of three passerine bird species (reed buntings, brown-eared bulbuls and pale thrushes) to HPAI H5N1, and finds that 2 out of 3 (buntings & bulbuls) sickened and died, while pale thrushes seroconverted exhibited no clinical signs of infection.
With the emergence of new avian flu viruses around the globe nearly every year, research into their interactions with thousands of non-aquatic bird species has only just begun.