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Concern about disease and toxic contamination as causes of amphibian declines has increased considerably in recent years (Carey and Bryant, 1995; Daszak and others, 1999). A corollary of this concern is the need for field workers to avoid becoming vectors for transmitting disease organisms or toxic chemicals to and among study sites. The Declining Amphibian Populations Task Force (DAPTF) has developed a standard protocol for use by anyone conducting fieldwork at amphibian breeding sites or in other aquatic habitats. These procedures should be used for all routine surveys, but more stringent measures are necessary in areas with known diseases.
1Only vinyl gloves should be used when handling amphibians. Some people are allergic to latex gloves,
The best diagnostic specimen is the live, sick amphibian. Live amphibians are necessary to obtain meaningful bacterial cultures and most types of fungus cultures. In addition, blood for various blood tests can be obtained only from live amphibians. Dead amphibians have limited usefulness because aquatic animals decompose much more rapidly than terrestrial animals which means amphibian carcasses nearly always will have large numbers of decompositional bacteria and fungi throughout their bodies. This rapid decomposition (autolysis) makes it very difficult to obtain meaningful or useful bacterial and fungal cultures, but dead amphibians may still have usefulness for virus cultures, histology and toxicological tests, if promptly and properly preserved.
If the amphibians will be captured and euthanized as part of other studies, then first observe and record their behavior. Blood should be collected and saved prior to euthanasia. If the euthanized amphibians will be preserved in a fixative, then collect swabs for bacterial, viral and fungus cultures from the mouth, vent, skin, and any skin abnormalities (lesions) prior to emersion of the animal in the fixative.
At a casualty site, the priority specimens for diagnostic examinations are live, sick amphibians. Divide dead amphibians into two groups: promptly preserve about half the carcasses (preferably the most recently dead amphibians) in 10 percent formalin (or 70-75 percent ethanol); promptly freeze the other dead amphibians (for virus cultures and possible poison tests). In cases involving less well known species, submission of live healthy amphibians as control or baseline specimens will be necessary to assist in the interpretation of findings in the sick or dead animals.
More than one lethal disease may affect a population simultaneously, so submission of multiple animals is always encouraged. Collect specimens that represent the species that are affected and the geographic areas. Do not place live and dead animals in the same container, and do not put multiple species in the same container (except, it is acceptable to put dead animals of multiple species in one container of formalin or ethanol).
If possible, submission of invading (alien or introduced) amphibians from the casualty site is desirable, even if they appear healthy or unaffected, because invasive species can be the vectors of infectious diseases. If any other endemic amphibians, fish, or reptiles are present at the casualty site, these animals also may need to be examined as part of a wider epizootiologic investigation into the cause of the casualties.
Many amphibian die-offs are fleeting. This means the casualties must be collected the hour and day they are found. Returning to the casualty site the next day to collect sick amphibians and carcasses invariably fails because of the highly efficient activity of scavengers during the night and rapid autolysis of carcasses.
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