The Facts About West Nile Virus
(that relate to wildlife rehabilitation in Maine)

Prepared by Dave Phillips, Wildlife Biologist, MDIFW

12 confirmed avian cases in Maine in 2005.

Although crows and blue jays account for between 50 and 90 percent of reported avian cases, WNV infection has been identified in over 130 native North American birds and nearly 40 exotic and zoo species. During the summer of 2002, significant numbers of raptor species (owls, hawks, eagles and vultures), especially in the midwestern United States, were found to be infected with the virus.

Research has shown that it is possible for bird-to-bird transmission to occur as a result of oral and cloacal secretions contaminating water and food. There may be a direct bird-to-bird transmission but the cause is unknown. Research has also shown that the virus may be passed to raptors by eating infected birds. However, the most likely route of transmission is still the mosquito. Experimental evidence of direct transmission among corvids and gulls exists, but whether this occurs in nature is unknown.

Certain species of birds, in particular corvids (e.g., crows and jays) experience high clinical attack rates. Most infected corvids die within 3 weeks of infection. Clinical signs prior to death may include uncoordinated flying or walking, weakness, lethargy, tremors, and abnormal head posture. Not all species of birds die or are negatively affected by WNV.

Maine is on the edge of where this disease is common, although it appears that in some years it can be more common and widespread in the state than in other years. Moving any bird (especially Corvids) from any area to your facility involves the risk of translocating the virus and introducing it into the mosquito population of your area. The mosquito is the vector and generally accepted mode of transmission between individuals. A potential and perhaps likely result of bringing WNV to you facility would be the introduction of WNV to birds housed at your facility and wild birds in the area. If birds rehabilitating at your facility become infected and are released prior to showing symptoms, WNV would be spread through your actions, magnifying the impact of WNV on bird populations and susceptible humans. Although this is hypothetical and possibly alarmist, such potentially human cased dispersal of the virus should be avoided.

If infected, many species of birds die within 1-3 weeks and thus can serve as a "canary in a coal mine" for WNV in your area.

Recommendations:

Be aware of this disease and the related implications for translocating birds. Make informed decisions regarding WNV exposure and release of wild birds.

Rehabilitators should consider mosquito-proof facilities to avoid introducing WNV to their local mosquito population.

Transport distances should be kept to a minimum by bringing birds to the nearest qualified rehabilitator.

Rehabilitators should consider a mosquito-free quarantine for 2 weeks prior to releasing birds, or postpone releases until no new birds have been accepted for 2 weeks.

All birds should be released in the same general area where they were initially found.

Please contact us if you suspect WNV in your area. Realize that not all bird species are adversely affect by the virus.

Q. What should I do if I find a dead bird?

A. The usual bird surveillance season in Maine is from June through October. If you find a dead bird in these months, call the Maine CDC Dead Bird Reporting Line at 1-888-697-5846, and you will be provided with further instruction. Testing of dead birds in 2006 will limited to corvids (ravens, crows, and blue jays), unless there are unusual circumstances.Captive pheasants and emus are notable exceptions, and owners of these species or veterinarians providing care for these species are also encouraged to call the Bird Reporting Hotline if they detect severe illness or death in their birds. Even though not all dead birds will be collected or tested, all reports will be recorded; this information can be very useful in detecting clusters of dead birds that occur over time, and can indicate if and when the testing protocol should be modified.


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