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West Nile Virus


West Nile….what is that? West Nile is a virus that, at its worst causes encephalitis, which is a dangerous swelling of the brain. Although most of those infected with the virus suffer mild flu-like symptoms it can be fatal in the elderly and those with deficient immune systems.

West Nile first appeared in the United States in 1999, concentrated in the Queens section of New York City and then spread to a few other contiguous Northeast states. That year there were 62 confirmed cases in humans with seven deaths. The virus also attacks pets, horses and other mammal species as well as 56 avian species 48 which are native to the United States. The primary bird species to carry and succumb to the virus is the American and Fish Crow. The humans and animals were all infected with the virus by various species of mosquitoes, primarily the Culex pipiens mosquito.Since 1999 the virus has been identified in New Hampshire, Massachusetts, Rhode Island, Connecticut, New York, New Jersey Pennsylvania, Maryland, District of Columbia, Virginia, North Carolina, Alabama, Georgia, Florida, Arkansas, Illinois, Delaware, Ohio, Missouri and as far north as Ontario. The Center for Disease Control and Prevention (CDC) scientists expects the virus to spread into Central America and California by this year and will eventually spread across the entire United States. It was previously an international problem with many deaths occurring in Israel and Jordan last year. The virus was first documented in Africa.

west nile life cycle

Public health officials in many of the aforementioned states have been attacking the problem by trying to kill mosquito populations with extensive pesticide spraying programs which are very expensive and worry citizens about their effects on human populations. This year most states are taking more of an "educate the public" approach in trying to reduce mosquito-breeding areas especially around population centers. Some of the things we CROW BUSTERS can do in our communities are: clean rain-gutters so they can flow freely, remove old tires and/or play equipment that hold water or drill drainage holes in them, replace water in bird baths twice a week and, in general, remove standing water that mosquitoes lay their eggs in.

The best precaution persons can take to reduce bites are to wear clothing that covers the skin, use mosquito repellants and curtail outside activity in the early mornings and late evenings when mosquitoes are the most active.

As for us CROW BUSTERS, the CDC has no evidence that the virus can be obtained by handling live or dead, infected birds. With this, we still recommend handling your kills with rubber gloves. As far as eating them, the jury is still out. We have suggested that folks should refrain from eating crows in, at least, the states where positive cases have been discovered because the CDC has not made any definitive statements concerning this matter.

If you would like to find out more about the West Nile virus go to the Centers for Disease Control.

Its Impact on Crow Hunting

Many of you have asked, “I haven’t seen as many crows…has West Nile taken a heavy toll on their numbers?” The crow is certainly a sentinel species but we had not heard of any studies being conducted to answer the question. Mortality has probably increased because of it, though.

A project detailed in the October 2003 issue of the Wildlife Society Bulletin that may shed some light on the West Nile mortality question. Since the fall of 1997, a few researchers were studying social organization, dispersal patterns and cooperative nesting attempts of common (American) crows in and around Stillwater, Oklahoma. The crows were captured with a rocket net and marked with wing tags and colored leg bands. Family groups were marked and classified as breeders, auxiliaries which were offspring from previous years and individuals that had moved in with the families from other areas. Morphological data was taken from each individual before being released.

The crows were monitored continuously throughout the year from 1997 through 2002. Of importance for this article was that in August of 2002, 120 of 145 individual crows in approximately 28 family groups were marked. It was during the fall of 2002 that West Nile was first confirmed in the Stillwater area and in mid September a marked individual in the study died. In the next 30 days 8 more carcasses were found and 37 other marked crows were missing and presumed dead. Some of these were observed staggering clumsily prior to their disappearance.

Some of the individuals that disappeared during the fall of 2002 dispersed out of the population that is normal. Yet 40% (48 of 120 marked individuals) within 2 months of the arrival of the West Nile Virus in the area, died. One other observation was referred to in the article. In Ithaca, New York, 25 of 68 crows (37%) in 10 contiguous crow families disappeared between July and October 2002. 21 were found dead, and of these, 19 were known or suspected to have died from West Nile Virus.

These numbers of individuals are not great but the data suggests that mortality in wild crow populations may approach 40% within 2 months of exposure to the West Nile Virus.

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