Editor’s Note: According to a Nov. 4 News.Discover.com article, the West Nile virus (WNV) is “decimating” U.S. native bird populations. Chicago-based bird control product manufacturer Bird-X has issued a response as follows:
The disease people typically thought of as a human and mosquito problem is in fact a much larger issue that threatens populations of birds already struggling with habitat loss and global warming. Rises in the virus also mean an escalated risk of exposure to humans due to the virus’ transmission cycle.
Wednesday’s article states that the National Academy of Studies released a study on Monday looking at the virus’ impact on 49 bird species collected from over 500 US bird banding stations from 1992 to 2007. Significant declines in survival rates were found for 23 of the 49 species, including a 29 percent decline in red-eyed vireos, making up a 30 million West Nile virus-caused population decline for that species.
The article continues, “West Nile, a mosquito-borne illness, was introduced in North America in 1989. It has drawn the most attention for its impact on humans, with 1 in 5 people who are infected developing a fever with other symptoms…. Less known has been the toll it has taken on native birds, who serve as primary host for the virus. It is believed to have killed millions of birds though this is the first study to fully document the demographic impacts of West Nile on populations across larger areas of North America.
On Bird-X’s WNV webpage, it states: “The birds cannot directly transmit the disease to humans, but their close proximity in combination with mosquitoes can be of concern.”
The Bird-X page points out that WNV’s transmission cycle typically circulates between birds and mosquitoes, and only then can it be transmitted to humans. This is because the virus incubates inside the bodies of birds to highly infectious concentrations, and when mosquitoes feed upon these infected birds again, they can then pass the virus to humans at contractible levels. This means that the more birds catch the virus, the more frequently it will be passed on to humans.
As reported on the Bird-X page by the U.S. Centers for Disease Control & Prevention (CDC), humans who develop symptoms of WNV face potentially fatal results, with symptoms including severe fever, headaches, body aches, joint pain, diarrhea, rash, meningitis, encephalitis, and more.
The News.Discovery.com article additionally points out, “land use was a factor both helping and hurting birds. Some species that lived in close proximity to humans suffered worse while others fared fine, possibly because they benefitted from the additional food sources around.” Due to habitat loss however, birds are now more confined to shared spaces more than ever, with the highly infectious virus still running rampant.
However, as Dr. Wesley Hochachka of Cornell University’s Lab of Ornithology points out, “It’s just a pity that the authors’ data ended with 2007, because it would be interesting to see if some of these effects have persisted to this day.”