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International Society for Infectious Diseases <http://www.isid.org>

Date: Fri 22 Jun 2012
Source: Hawaii 24/7 [edited]

Avian botulism kills 67 birds on Maui, claims over 300 birds on Kauai earlier in the year
Wetland biologists and others involved in managing lands with associated wetlands have been notified by the Department of Land and Natural Resources' Division of Forestry and Wildlife (DOFAW) of a recent avian botulism outbreak affecting waterbirds on Maui. In just over a week, 67 birds have been found dead at Kanaha Pond Wildlife Sanctuary in Kahului including Hawaiian stilt, Hawaiian coot, and Hawaiian ducks of adult and juvenile stages. The paralytic disease has killed adult birds on their nests, also causing the eggs to be lost.

Because botulinum toxin can be produced in most wetlands, and transported to new wetlands by dead or dying waterfowl, landowners and managers, both public and private, are being asked to frequently survey their wetlands for sick and/or dead birds, remove any dead or dying birds from the wetland, and contact local DOFAW biologists for guidance.

Earlier this year [2012] a botulism outbreak in Hanalei, Kauai resulted in over 300 sick and dead birds being collected by USFWS [US Fish and Wildlife Service] refuge staff. Additionally, numerous other botulism fatalities have also been reported at wetlands throughout the state.

Botulism is a paralytic condition brought on by the consumption of a naturally occurring toxin produced by the bacterium _Clostridium botulinum_. It is an intoxication rather than an infectious disease.
Botulism, type C is commonly found in Hawaiian soils and is NOT dangerous to humans. Particular environmental conditions in wetlands will sometimes allow this bacterium to produce botulinum toxin; the toxin is then accumulated in aquatic invertebrates. It is consumption of these toxic invertebrates by waterfowl that leads to mortality.

In Hawaii, birds commonly affected include waterfowl frequenting wetlands such as our endangered Hawaiian coots, Hawaiian ducks, Laysan ducks, Hawaiian moorhen, Hawaiian stilts, black-crowned night-herons, and various migratory waterfowl and shorebirds.

The US Geological Survey (USGS) National Wildlife Health Center Honolulu Field Station (NWHC-HFS) has been working closely with the USFWS and the State of Hawaii DLNR [Department of Land and Natural Resources] to investigate and confirm botulism as a cause of waterfowl mortality in Hanalei and Kahului. The NWHC-HFS provides technical assistance to federal, state, municipal, and non-governmental organizations on wildlife health related matters in Hawaii and the Pacific.

"Part of our role is to determine the cause of death during unusual wildlife mortality events involving native and endangered species and provide management recommendations to address and mitigate such mortalities" said Dr Thierry Work, Wildlife Disease Specialist for the USGS National Wildlife Health Center Honolulu Field Station. "For this particular event, our team first conducts necropsies of freshly dead birds here in Honolulu and then sends samples to the National Wildlife Health Center in Madison Wisconsin for confirmation of botulism."

Facts on avian botulism
Botulism is a natural toxin produced by a bacterium (_Clostridium
botulinum_) commonly found in the soil. There are several types of botulism toxin some of which can affect humans who eat improperly canned foods. Birds have their own kind of botulism (type C in Hawaii) that does not affect humans. When anaerobic conditions occur in water (low or no oxygen content) botulism type C is concentrated in aquatic invertebrates that filter feed sediments or water. When birds eat the invertebrates, they get a concentrated package of toxin. A bird-to-bird cycle can also exist where maggots feeding on dead birds can concentrate the toxin and can then be eaten by and poison other birds.

Avian botulism most often affects waterfowl. Typical clinical signs in birds with botulism include weakness, lethargy, and inability to hold up the head or to fly. For waterfowl, this can be catastrophic because inability to hold up the head leads to drowning.

In Hawaii, birds commonly affected include endangered Hawaiian ducks, Laysan ducks, Hawaiian coots, Hawaiian moorhens, and Hawaiian stilts.
Black-crowned night-herons, and various waterfowl and shorebirds are also affected.

Northern shovelers -- a common migratory duck in Hawaii -- are particularly sensitive indicators of botulism because they are efficient filter feeders and thus are most likely to accumulate sufficient toxin to kill. Avian botulism does not affect humans.

Note: although avian botulism type C does not pose a risk to humans, carcass removal should involve standard hygienic practices including gloves, boots, and coveralls.

For more information go to USGS

What can the public do?
Please report deaths of waterbirds to the District DOFAW Office on your respective island [listings available at the source URL above].
On private lands individuals are asked to take the above mentioned recommended wetland management actions to prevent further impacts of this fatal disease.

Communicated by:
ProMED-mail from HealthMap alerts

[Photos of most of these birds mentioned in this post may be viewed at <http://www.state.hi.us/dlnr/dofaw/pubs/WaterbirdCount_photoguide.pdf>

Hawaii may be found on the HealthMap/ProMED-mail interactive map at <http://healthmap.org/r/2DCr>.

This article speaks of management of this situation but it does not mention what specific steps are being taken. One of the most important steps is to remove the carcasses of the birds that have died.
Otherwise, as the maggots develop in the decomposing carcasses, they will bioaccumulate the botulism toxin. Therefore, when other birds consume the maggots, the botulism cycle will be perpetuated.

Botulism is sometimes called limberneck in ducks and other waterfowl.
Healthy birds, affected birds, and dead birds in various stages of decay are commonly found in the same area. The toxin affects the nervous system by preventing impulse transmission to muscles. Birds are unable to use their wings and legs normally or control the 3rd eyelid, neck muscles, and other muscles. Birds with paralyzed neck muscles cannot hold their heads up and often drown. Death can also result from water deprivation, electrolyte imbalance, respiratory failure, or predation.

Prompt removal and proper disposal of carcasses by burial or burning (in accordance with applicable ordinances) is highly effective in removing toxin and maggot sources from the environment. If possible, avoid altering water depth by flooding or drawing down water levels during hot weather. This may increase invertebrate and fish die-offs, a protein source for the bacteria.

Portions of this comment were extracted from <http://www.nwhc.usgs.gov/disease_information/avian_botulism/>. - Mod.TG]

[see also:
Botulism, avian - USA: (CA) 20120430.1117985
Botulism, avian - USA (05): (CA) 20111115.3369 Botulism, avian - USA (04): (NV) 20111009.3031 Botulism, avian - USA (03): (CO) 20110925.2905 Botulism, avian - USA (02): (CO) 20110924.2888 Botulism, avian - USA: (CO) 20110914.2797 2010
Botulism, avian - USA (05): (FL) susp. 20100817.2848 Botulism, avian - USA (04): (OH) 2 Botulism, avian - USA (03): (CA) 20100709.2294 Botulism, avian - USA (02): (CO) 20100627.2145 Botulism, avian - USA: (MI) susp 20100618.2047] .................................................sb/tg/mj/dk/ll
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