Theory: Human West Nile Virus Infections Are Related to Bird Feeders

Theory: Human West Nile Virus Infections Are Related to Bird Feeders

On 18 Aug 2012 Steve L. Shepard happened to mention that birds were not as concentrated in his yard as when he was feeding them (they are now spread out more). His words, plus the ongoing West Nile crisis in Dallas, gave me the idea for this theory: Human West Nile Virus Infections Are Related to Bird Feeders.

We know/believe:

--- Mosquitoes get West Nile virus from infected birds, or give virus to uninfected birds.

--- Mosquitoes that get the virus from an infected bird can bite humans and infect them with the virus.

--- Birds are closer together (more concentrated) and present themselves as more targets near feeders (than in areas with no feeders) to nearby mosquitoes.

--- Birds, like most animals, will not travel far from their "free lunch," or bird feeders, so they will rest/roost/stay/nest near the feeders.

--- Infected birds, possibly not feeling too well, will hang around bird feeders because they do not have to expend much energy in getting food. Bird feeders will draw the sick birds into the area around feeders more.

---Really sick birds that are no longer feeding, or moving much, will likely be close to the place of their last meal, which could be a bird feeder, and present themselves as easy targets for mosquitoes.

--- With bird feeders nearby birds do not have to work/fly/forage much to get their food, and rest more than birds having to hunt for their food. When they rest more, probably near the feeders, they present themselves as targets for mosquitoes a higher percentage of the day than foraging birds, and I would thus expect there to be a higher percentage of birds around bird feeders to be infected than those birds out foraging (it is harder for a mosquito to bite a moving/flying bird).

--- The mosquitoes near the bird feeders will have a greater chance of picking up the virus from the nearby birds than those mosquitoes out in "the sticks" that must prey on the fewer numbers, and/or more widely separated, of the more active birds out foraging (except near a large roost).

--- Various bird diseases can be encountered at, or even caused by, birdfeeders
http://wildlife.utah.gov/diseases/songbird_diseases.php and http://www.nwhc.usgs.gov/publications/pamphlets/coping_with_birdfeeder_diseases_pamplet.pdf , so it is not unusual to expect to find more birds, and thus more sick birds, around feeders.

Thus, some possible conclusions to my theory for humans are:

--- Bird feeders attract birds, which then attract mosquitoes that prey on the birds, which then increase the chances of birds/humans nearby getting infected with West Nile virus.

--- People who have bird feeders (or a feeder nearby in another yard) are subjecting themselves to a greater risk of getting West Nile virus than people who do not have bird feeders (or feeders nearby).

--- People who live near areas where large numbers of birds roost, or feed (garbage dumps), are at greater risk for West Nile virus infections.

Studies needed: 

It would be nice to see virus researchers study aspects of the above to prove, or not, if my theory is correct (I suspect it is correct.).

It would be interesting to see a map overlay of Dallas noting all houses where people lived that got West Nile virus infections in Dallas AND locations of active bird feeders (garbage dumps, and roosts) within a half mile (+ or -) of those houses.

It would also be interesting to see if fatter, lazier, less active birds near feeders are easier to infect with the virus, and have a greater incidence of infection, than leaner, more active foraging birds.

Comments: 

My present theory is but one factor of several that determine the spread of the West Nile virus. Probably the most important factor is the various waters of the area in question in which the mosquitoes reproduce. One must totally control mosquito reproduction to totally control West Nile virus. To decrease the number of human West Nile infections one must decrease the mosquito population, decrease the bird population, decrease or eliminate "hot spots" where birds concentrate near feeders, garbage dumps, and roosts, and/or have the humans change their habits so they get less mosquito bites (stay inside near dawn and dusk, use repellant, wear long clothing, dump standing water, etc.). Also see my previous proposal on mosquito control at: http://www.aquarticles.com/articles/management/Lawler_Mosquitoes.html
and the CDC Fact Sheet: http://www.cdc.gov/ncidod/dvbid/westnile/wnv_factSheet.htm .


West Nile virus has been shown to also infect horses, cats, bats, chipmunks, skunks, squirrels,
domestic rabbits http://www.cdc.gov/ncidod/dvbid/westnile/qa/transmission.htm and dogs
http://www.cdc.gov/ncidod/dvbid/westnile/qa/wnv_dogs_cats.htm , so it may also be
possible that people having a large number of dogs, cats, or squirrels around them may
possibly be at a greater risk for getting the virus. But the CDC presently believes that dogs
and cats do not develop enough virus to infect mosquitoes biting them http://www.cdc.gov/ncidod/dvbid/westnile/qa/wnv_dogs_cats.htm . Every possible
means of control of the West Nile virus should be practiced to keep the infections down.

Theory: People with bird feeders should stop feeding birds during the West Nile infection season each year to lessen their chances of getting the virus disease.


　
Adrian R. Lawler, Ph.D., retired, Aquarium Supervisor, J L Scott Aquarium, Biloxi
(C) 2012 --


Some more references on diseases at bird feeders:
http://birding.about.com/od/birdconservation/a/spreadillness.htm
http://www.birdfeeding.org/best-backyard-bird-feeding-practices/bird-safety/prevent-disease-at-your-bird-feeders.html
http://www.nwhc.usgs.gov/publications/fact_sheets/coping_with_diseases_at_birdfeeders.jsp
http://www.birds.cornell.edu/pfw/AboutBirdsandFeeding/FAQsBirdFeeding.htm
http://www.birds.cornell.edu/pfw/AboutBirdsandFeeding/DiseasedBirds.htm