Bird-feeding probably not to blame for outbreak of bacterial disease,experts say
ITHACA, N.Y. -- Until laboratory tests identify sources of a bacterialdisease killing songbirds in the East and Midwest, Cornell Universityscientists say people who feed birds should not blame themselves for therecent outbreak of salmonellosis in redpolls and other flocking species.
Nevertheless, three precautions are in order, say experts at the CornellLaboratory of Ornithology and the College of Veterinary Medicine:
-- Clean bird feeders with a 10 percent bleach solution or stop feedingaltogether now that warm weather is here.
-- Do not try to rehabilitate sick birds without the legally requiredpermits from federal and state authorities.
-- When handling dead birds, remember that the bacterial disease may turnout to be transmissible to humans.
"In fact, we don't know which of the 2,000 or so possible strains ofsalmonella is killing songbirds," says Patrick McDonough. Thebacteriologist in Cornell's Veterinary Diagnostic Laboratory says there issome concern that the recent epidemic of salmonellosis could be due to themulti-antibiotic resistant "Salmonella Typhimurium" DT104. Tests now underway at the USDA's National Veterinary Services Laboratory in Ames, Iowa,are trying to identify the salmonella strain affecting songbirds, McDonoughnotes.
"We started getting reports of dying birds in late January from someparticipants in Project FeederWatch," says Margaret Barker, educationcoordinator at the Cornell Laboratory of Ornithology, where the13,500-member citizen-science project is headquartered. "Then it was quiet-- until late February and March, when we heard many more reports ofbacterial disease in flocking birds," she says, referring to species suchas pine siskins, evening grosbeaks, American goldfinches and commonredpolls.
The National Wildlife Health Center in Madison, Wis., has confirmedsalmonella as the cause of songbird sickness or mortality in Arkansas,Illinois, Indiana, Michigan, Missouri, New Hampshire, New York,Pennsylvania, Vermont and Wisconsin.
"We'd like to know what stressors are making birds so susceptible this yearto bacterial disease," says Cornell wildlife veterinarian Barry K. Hartup.He notes that affected parts of the United States had a mild winter withfew severe storms, which sometimes stress birds and other wild animals.
However, one possible cause of stress could be unaccustomed, long-distanceflights to the United States by birds that normally winter in Canada.Participants in Project FeederWatch, who count feeder birds throughoutNorth America, are reporting "irruptions" of redpolls and other flockingspecies into the United States Regional food shortages in Canada arebelieved by some ornithologists to be the cause for the unusual migration.
Hartup, who also studies conjunctivitis in house finches, says wild birdsfrequently carry one or more forms of salmonella without becoming ill --unless their immune systems are stressed or unless a particularly virulentstrain of salmonella comes along. He recommends against medicating sickbirds by the general public for two reasons: Holding or rehabilitatingmigratory birds requires a federal license. And treating birds withantibiotics can appear to cure the illness while making the birds"carriers" and potentially infecting many others.
At the Cornell Laboratory of Ornithology, coordinator Barker says somededicated bird-feeders are blaming themselves because they see sick birdsat their bird-feeding stations. In fact, the disease, which is transmittedby infected fecal matter, probably occurs wherever flocking species gathertogether -- in the woods, fields or barnyards.
"If the only place you see birds is in your backyard, and birds there aresick, you might think bird feeders are a reservoir of bacterial disease,"Barker says. "That's not necessarily so. But it's always been a good ideato clean feeders on a regular basis and to provide several feeders so thebirds aren't competing for the same food."
Or taper off feeding for this season, suggests bacteriologist McDonough.He points out that, like most bacteria, salmonella thrives in warm, wetconditions and "El Nino "so far has been responsible for plenty of both.Spring, he says, could bring more of the same.
The Cornell scientists agree on one thing: Dead birds should "not" be sentto the university. They suggest that people with suspected salmonellosiscases contact the wildlife conservation office in their home states fordirections. In New York state, for example, that would be the wildlifepathology division of the Department of Environmental Conservation at (518)478-3032.
New York state wildlife pathologist Ward Stone says his office is gettingbirds from most areas of the state, with the exception of the Buffalo area,and welcomes more. And he advises people in areas affected by songbirdsalmonellosis to stop feeding birds until the disease is more preciselyidentified.
Wildlife veterinarian Hartup recommends careful handling of dead birds inthe event that the disease can be transmitted to humans or pets. Glovesshould be worn, and birds should be securely wrapped, he says, and placedin outdoor garbage containers for disposal or buried in ground that willnot be disturbed.
Songbird Salmonella Q&A
Source: Cornell Laboratory of Ornithology
WHAT IS CAUSING MY BIRDS TO GET SICK AND DIE? I'VE FOUND DEAD REDPOLLS UNDER MY FEEDERS.
We can't be certain what might be the cause, but we can tell you thatcurrently there is an outbreak of the salmonella bacteria among songbirdsin Eastern and Midwestern states. The bacteria is fast-acting and spreadsrapidly throughout the body. Birds can die quickly.
WHAT SYMPTOMS DO BIRDS WITH SALMONELLOSIS SHOW?
A bird with salmonellosis appears tame. It might sit quietly for days in asheltered spot. Often, its feathers are fluffed out, and you might see ithold its head under its wings. As the disease progresses, the bird mightexhibit a wobbly head and staggering walk. You might witness shivering orconvulsions, and the bird might have trouble swallowing. Within a few hoursafter the symptoms show strongly, the bird simply falls over and dies.
HOW IS THE DISEASE SPREAD? IS MY BIRD FEEDER KILLING MY BIRDS?
Salmonella is shed in feces. The National Wildlife Health Center adds itcan also be spread bird-to-bird via direct contact or through ingestion offood or water contaminated with "nfected avian or mammalian fecal matter."Birds pick up the salmonella bacteria at places other than bird feeders.But human observers most easily and usually see birds at feeders. Yourfeeders are probably not killing your feeder visitors; there are someprecautions you can take to keep your feeders clean, however, to help yourest assure that you are doing what you can to prevent the spread ofdisease.
WHAT CAN I DO TO HELP PREVENT THE SPREAD OF THE DISEASE?
Temporarily take down your feeders. This gives you time to clean up underthe feeders and allows the birds that are used to feeding there totemporarily disperse. Before replacing the feeders, clean with a 10percent bleach solution: one part household chlorine bleach to nine partsof water. Avoid crowding at feeders. Provide lots of feeder space.Several feeders are better. This helps decrease the bacteria load. Storeseed in rodent-proof containers. This helps prevent rodent droppings in theseed. Replenish food often. Practice good sanitation and common sensewhen cleaning to minimize the risk of spreading the disease to humans orpets. Wear rubber gloves if you handle sick or dead animals or fecalmaterial. Wash hands well after. Clean feeder in a bucket, for example,rather than the kitchen sink. Discourage pets from feeding on sick and deadbirds.
DO BIRDS WITH SALMONELLOSIS ALWAYS DIE? WHAT CAN I DO TO HELP THEM INADDITION TO KEEPING MY FEEDERS CLEAN?
Birds infected with the bacteria do not always die. Some studies show thatinfected birds can remain healthy, even as they pass the disease to otherbirds. Many birds become sick only if they are under stress -- from severeweather or other causes. A Cornell veterinarian says what infected birdsneed most is water. The disease causes dehydration. But water must be keptextremely clean and fresh to stop spread of the disease. Only federallylicensed rehabilitators or veterinarians can legally administerantibiotics. The National Wildlife Health Center staff are concerned thatuse of antibiotics on wild birds will create a highly resistant strain ofalmonella that could impact poultry, pets, humans.
WHAT SHOULD I DO WITH MY DEAD BIRDS? CAN LABS OR VETS USE THEM?
Dead birds should be disposed of by wrapping tightly and putting in outdoorgarbage containers with tight lids. Some state wildlife agencies orresearch veterinary colleges might want the birds for study. Call thoseinstitutions for instructions on how to keep the birds-- usual instructionsare for the birds to be kept cool or frozen in a tightly-closed plasticbag. Be sure to include data such as the location and date you found thebird.
WHERE IS THE DISEASE?
As of March 19, 1998, the National Wildlife Health Center in Madison, Wis.,had received reports of sick or dead birds at bird feeders in 13 Midwesternand Eastern states. Specifically, salmonellosis is now confirmed as thecause of songbird sickness or mortality in the following ten states:Arkansas, Illinois, Indiana, Michigan, Missouri, New Hampshire, New York,Pennsylvania, Vermont, and Wisconsin. Similar incidents of passerinemortality without lab confirmation are reported in Connecticut, Ohio andMassachusetts. FeederWatchers began reporting the disease to Lab staff asearly as late January. The disease seemed to retreat but is now spreadingagain.
HOW UNUSUAL IS THIS DISEASE IN THE EAST AND MIDWEST? IS THIS OUTBREAK DUETO EL NINO?
A major outbreak of salmonellosis was reported in the Northeastern UnitedStates in the spring of 1988. It is a more common occurrence in the Westand Northwest, where every few years a die-off occurs, usually involvingPine Siskins. This West/Northwest outbreak has been documented by ProjectFeederWatch participants. We cannot at this time determine if thesalmonella outbreak is due at least in part tothe milder-than-usual winterin the East and Midwest. But, this is an interesting question.
WHICH BIRD SPECIES ARE HARDEST HIT?
During the current outbreak, most reports of mortality include pinesiskins, american goldfinches and common redpolls. New York birds hardesthit by the outbreak are Common Redpolls.
IS THE OUTBREAK CONNECTED TO THE WINTER FINCH INVASION?
We can't say that there is a connection to the high numbers of finches andred-breasted nuthatches reported in the Northeast this year.
CAN I GET SALMONELLA FROM MY BIRD FEEDERS? WHAT ABOUT MY PETS?
The National Wildlife Health Center reports that there are more than 2,000strains of salmonella bacteria; many different birds and mammals can beinfected. Specific strains usually affect specific animals. However, it ispossible that the strain typically seen in songbirds could cause illness inhumans and domestic animals. Act on the side of caution: Use common senseand practice good sanitation. Repeating from above: Wear rubber gloves ifyou handle sick or dead animals or fecal material. Wash hands well after.Clean feeder in a bucket, for example, rather than the kitchen sink.Discourage pets from feeding on sick and dead birds.
Materials provided by Cornell University. Note: Content may be edited for style and length.
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