Beyer, R. Scott. West Nile Virus and Chickens, Manhattan, Kansas, Kansas State University, Feb. 2003

Beyer, R. Scott

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1West Nile VirusandChickensR. Scott Beyer Poultry SpecialistAnimal Sciences and IndustryKansas State UniversityAgricultural Experiment Station andCooperative Extension ServiceSince about 1999, West NileVirus (WNV) has become apublic health concern in theUnited States. Previouslyknown to exist in Africa, Asia,and the Middle East, WNVfirst occurred on the East Coastand has spread west to otherstates, including Kansas.Since appearing in theUnited States, there have beenWNV cases in wild and exoticbirds, bats, horses, smallmammals and humans. Crowsand blue jays are particularlysusceptible to the effects ofWNV and often die. However,most healthy animals seem tobe able to overcome theinfection with no apparentillness.How the virus spreadsThe virus is spread bymosquitos. Mosquitos becomeinfected with WNV after bitingand feeding on infected wildbirds. The infection is spreadwhen the mosquitos bitepeople, animals or other birds.The virus results in encephali-tis, which is inflammation ofthe brain.Although chickens maybecome infected by the virus,they show few or no signs ofthe infection. The virus can beisolated for eight days frominfected chickens. However,the level of virus in chickenblood is low and is probablynot high enough to infect othermosquitos. Chickens developantibodies to the virus withinfive to seven days. Thus,chickens are unlikely toamplify the WNV infection inmosquitos. There is no evi-dence of animal-to-animal oranimal-to-person transmissionof WNV. People can onlybecome infected through thebite of an infected mosquito,and only a small number ofmosquitos carry the virus.Poultry as sentinelsWhen WNV came to theUnited States, researchersneeded a way to track thespread of the virus. They chosechickens because they wereinexpensive, easy to handle,would not become ill from theinfection, nor become sourcesof infection. Researcherspenned healthy birds outdoorsand monitored them for aWNV infection. When thesesentinel birds were infected,researchers knew mosquitos inthe area were capable ofspreading the disease. Becauseall types of chickens were usedas sentinels, many peoplebegan to associate the viruswith chickens and believechickens were the source ofWNV. People who believechickens cause WNV may havemisunderstood the sentinelprograms.What are the signs ofinfection?Chicken and turkeysinfected with WNV may showno signs of infection. BecauseWNV causes inflammation ofthe brain, expect clinical signsof the virus to be nervoussystem problems. Abnormalhead posture, a wobbly gait,inability to stand, staggeringand tremors are commonsymptoms. Many of thesesymptoms have been observedin birds, but not in chickens.What other commonpoultry diseases may havesimilar symptoms toWNV?As you can imagine, theclinical signs of WNV arecommon to many other poultrydiseases that may occur inKansas. Of particular impor-tance are Newcastle Diseaseand Marek’s Disease. How-ever, avian influenza, fowl2cholera and infections or injuryto the brain or spinal cord, andcertain vitamin deficienciescould have clinical signssimilar to WNV in chickens.Can I get WNV from mychickens?No. Infected mosquitostransmit the virus to birds, butthere is no evidence that directtransmission from birds tohumans can occur. Infectedchickens housed withuninfected chickens did nottransmit the virus.Can I still eat the eggsand meat?Yes, provided that yourbirds are generally healthy.Unhealthy birds or their eggsshould not be consumed.Remember to follow propercooking procedures to safelyprepare poultry meat and eggs.What should I do withbirds that have died?Always handle deadanimals with gloves fordisposal. Wash your handsafter handling. You will not beexposed to WNV, but youcould be exposed to otherharmful bacteria.How do I protect mychickens from a WNVinfection?Because most small poultryflocks are allowed access to theoutdoors, it is almost impos-sible to totally eliminate theirexposure to mosquitos. Thebest you can do is reduce thepopulation of mosquitosaround the area where thechickens are housed. Focus oneliminating standing waterwhere mosquito larvae coulddevelop. Old tires and housegutters are common sources ofstanding water. Turn overbuckets and feeders when notin use. Small pools or ponds forwaterfowl can be stocked withfish to consume mosquitolarvae.Is there a treatment forchickens that may have aWNV infection?No. Viruses are difficult totreat and must often be left torun their course. Reduce thestress on the animals as muchas possible. Some poultry flockowners will temporarilyadminister a broad spectrumantibiotic to prevent opportu-nistic bacterial infections fromtaking advantage of the bird’spoor state of health. Consultyour agriculture supply dealerfor the proper use of antibioticsin your  flocks. Remember tofollow label directions carefullywhen using antibiotics.Can I vaccinate my flockfor WNV?Not yet. A poultry vaccinefor WNV has not been ap-proved for use; however,because the virus is neutralizedby the bird’s immune system,there is hope that a vaccine canbe developed.Could my turkeys becomeinfected with WNV?Yes, but the virus appears tohave little effect. The USDAinoculated turkeys with thevirus and found that they didnot develop enough of thevirus to infect feeding mosqui-tos. They determined that wildand domestic turkeys will notbe a significant source of thevirus for infecting mosquitos.Are my game birds sus-ceptible to WNV?Little research is availablefor game birds. But it is likelythat pheasant, quail and wildturkeys could become infected.Should I worry about mywaterfowl?Ducks and geese have beeninfected with WNV, and somehave died. Because waterfowlare around water wheremosquitos are present, it maybe particularly difficult toreduce their risk. More researchis needed to  know the effect ondomestic and wild waterfowl.What about my pet birds?Less is known about WNVinfection in exotic birds.Because most pet birds, such asparrots, canaries, and cock-atiels, spend most of their timeindoors, it is likely their riskwill be low. Keeping mosquitosout of the house should protectyou and your pet birds.Should I worry aboutWNV in game birds thatI hunt?Because the virus wasshown to cause a mild reactionin turkeys, followed by a rapidimmune response, it is unlikelythat hunters will encountersignificant numbers of birdswith active infections of WNV.Hunters should use standardprecautions such as propercleaning, storage temperaturesand cooking methods to reducethe risk of foodborne patho-gens when consuming gamebirds.Kansas State University Agricultural Experiment Station and Cooperative Extension ServiceEP-117 February 2003It is the policy of Kansas State University Agricultural Experiment Station and Cooperative Extension Service that all persons shall have equal opportunity andaccess to its educational programs, services, activities, and materials without regard to race, color, religion, national origin, sex, age or disability. Kansas StateUniversity is an equal opportunity organization. Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30, 1914, as amended. Kansas StateUniversity, County Extension Councils, Extension Districts, and United States Department of Agriculture Cooperating, Marc A. Johnson, Director..Contents of this publication may be freely reproduced for educational purposes. All other rights reserved. In each case,  credit R. Scott Beyer,West Nile Virus and Chickens, Kansas State University, February 2003.

West Nile virus and chickens

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West Nile virus and chickens

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