Mar. 31, 1998 Bird-feeding probably not to blame for outbreak of bacterial disease, experts say
ITHACA, N.Y. -- Until laboratory tests identify sources of a bacterial disease killing songbirds in the East and Midwest, Cornell University scientists say people who feed birds should not blame themselves for the recent outbreak of salmonellosis in redpolls and other flocking species.
Nevertheless, three precautions are in order, say experts at the Cornell Laboratory of Ornithology and the College of Veterinary Medicine:
-- Clean bird feeders with a 10 percent bleach solution or stop feeding altogether now that warm weather is here.
-- Do not try to rehabilitate sick birds without the legally required permits from federal and state authorities.
-- When handling dead birds, remember that the bacterial disease may turn out to be transmissible to humans.
"In fact, we don't know which of the 2,000 or so possible strains of salmonella is killing songbirds," says Patrick McDonough. The bacteriologist in Cornell's Veterinary Diagnostic Laboratory says there is some concern that the recent epidemic of salmonellosis could be due to the multi-antibiotic resistant "Salmonella Typhimurium" DT104. Tests now under way at the USDA's National Veterinary Services Laboratory in Ames, Iowa, are trying to identify the salmonella strain affecting songbirds, McDonough notes.
"We started getting reports of dying birds in late January from some participants in Project FeederWatch," says Margaret Barker, education coordinator at the Cornell Laboratory of Ornithology, where the 13,500-member citizen-science project is headquartered. "Then it was quiet -- until late February and March, when we heard many more reports of bacterial disease in flocking birds," she says, referring to species such as pine siskins, evening grosbeaks, American goldfinches and common redpolls.
The National Wildlife Health Center in Madison, Wis., has confirmed salmonella 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 year to bacterial disease," says Cornell wildlife veterinarian Barry K. Hartup. He notes that affected parts of the United States had a mild winter with few severe storms, which sometimes stress birds and other wild animals.
However, one possible cause of stress could be unaccustomed, long-distance flights to the United States by birds that normally winter in Canada. Participants in Project FeederWatch, who count feeder birds throughout North America, are reporting "irruptions" of redpolls and other flocking species into the United States Regional food shortages in Canada are believed by some ornithologists to be the cause for the unusual migration.
Hartup, who also studies conjunctivitis in house finches, says wild birds frequently carry one or more forms of salmonella without becoming ill -- unless their immune systems are stressed or unless a particularly virulent strain of salmonella comes along. He recommends against medicating sick birds by the general public for two reasons: Holding or rehabilitating migratory birds requires a federal license. And treating birds with antibiotics 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 some dedicated bird-feeders are blaming themselves because they see sick birds at their bird-feeding stations. In fact, the disease, which is transmitted by infected fecal matter, probably occurs wherever flocking species gather together -- in the woods, fields or barnyards.
"If the only place you see birds is in your backyard, and birds there are sick, 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 idea to clean feeders on a regular basis and to provide several feeders so the birds 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, wet conditions 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 sent to the university. They suggest that people with suspected salmonellosis cases contact the wildlife conservation office in their home states for directions. In New York state, for example, that would be the wildlife pathology division of the Department of Environmental Conservation at (518) 478-3032.
New York state wildlife pathologist Ward Stone says his office is getting birds from most areas of the state, with the exception of the Buffalo area, and welcomes more. And he advises people in areas affected by songbird salmonellosis to stop feeding birds until the disease is more precisely identified.
Wildlife veterinarian Hartup recommends careful handling of dead birds in the event that the disease can be transmitted to humans or pets. Gloves should be worn, and birds should be securely wrapped, he says, and placed in outdoor garbage containers for disposal or buried in ground that will not 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 that currently there is an outbreak of the salmonella bacteria among songbirds in Eastern and Midwestern states. The bacteria is fast-acting and spreads rapidly 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 a sheltered spot. Often, its feathers are fluffed out, and you might see it hold its head under its wings. As the disease progresses, the bird might exhibit a wobbly head and staggering walk. You might witness shivering or convulsions, and the bird might have trouble swallowing. Within a few hours after 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 it can also be spread bird-to-bird via direct contact or through ingestion of food 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. Your feeders are probably not killing your feeder visitors; there are some precautions you can take to keep your feeders clean, however, to help you rest assure that you are doing what you can to prevent the spread of disease.
WHAT CAN I DO TO HELP PREVENT THE SPREAD OF THE DISEASE?
Temporarily take down your feeders. This gives you time to clean up under the feeders and allows the birds that are used to feeding there to temporarily disperse. Before replacing the feeders, clean with a 10 percent bleach solution: one part household chlorine bleach to nine parts of water. Avoid crowding at feeders. Provide lots of feeder space. Several feeders are better. This helps decrease the bacteria load. Store seed in rodent-proof containers. This helps prevent rodent droppings in the seed. Replenish food often. Practice good sanitation and common sense when cleaning to minimize the risk of spreading the disease to humans or pets. Wear rubber gloves if you 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.
DO BIRDS WITH SALMONELLOSIS ALWAYS DIE? WHAT CAN I DO TO HELP THEM IN ADDITION TO KEEPING MY FEEDERS CLEAN?
Birds infected with the bacteria do not always die. Some studies show that infected birds can remain healthy, even as they pass the disease to other birds. Many birds become sick only if they are under stress -- from severe weather or other causes. A Cornell veterinarian says what infected birds need most is water. The disease causes dehydration. But water must be kept extremely clean and fresh to stop spread of the disease. Only federally licensed rehabilitators or veterinarians can legally administer antibiotics. The National Wildlife Health Center staff are concerned that use of antibiotics on wild birds will create a highly resistant strain of almonella 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 outdoor garbage containers with tight lids. Some state wildlife agencies or research veterinary colleges might want the birds for study. Call those institutions for instructions on how to keep the birds-- usual instructions are for the birds to be kept cool or frozen in a tightly-closed plastic bag. Be sure to include data such as the location and date you found the bird.
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 Midwestern and Eastern states. Specifically, salmonellosis is now confirmed as the cause 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 passerine mortality without lab confirmation are reported in Connecticut, Ohio and Massachusetts. FeederWatchers began reporting the disease to Lab staff as early as late January. The disease seemed to retreat but is now spreading again.
HOW UNUSUAL IS THIS DISEASE IN THE EAST AND MIDWEST? IS THIS OUTBREAK DUE TO EL NINO?
A major outbreak of salmonellosis was reported in the Northeastern United States in the spring of 1988. It is a more common occurrence in the West and Northwest, where every few years a die-off occurs, usually involving Pine Siskins. This West/Northwest outbreak has been documented by Project FeederWatch participants. We cannot at this time determine if the salmonella outbreak is due at least in part tothe milder-than-usual winter in 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 pine siskins, american goldfinches and common redpolls. New York birds hardest hit 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 and red-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 2,000 strains of salmonella bacteria; many different birds and mammals can be infected. Specific strains usually affect specific animals. However, it is possible that the strain typically seen in songbirds could cause illness in humans and domestic animals. Act on the side of caution: Use common sense and practice good sanitation. Repeating from above: Wear rubber gloves if you 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.
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