404
The Biology of Sea Turtles, Vol. II
15.3.3.7 Assessment of Results, Amended Problems
and Differentials Lists, and Decisions
Throughout this process, decisions must be made about what additional tests to
perform, and whether to begin supportive therapy, attempt to treat and rehabilitate,
or euthanize and necropsy the animal. The goals of the investigation must be
considered; i.e., is one trying to cure the individual turtle or learn more about its
pathologic condition to help the population? These goals can be in extreme
conflict. In some cases, euthanasia of a mildly affected turtle in the early stages
of a disease can yield more information about the pathogenesis and etiology of
the disease. In some cases, treatment may eliminate the etiologic agent or introduce artifact. On the other hand, response to the specific therapy may aid in
diagnosis. Before a decision is made to treat, the investigative team should
consider whether they have performed the tests and obtained the samples needed
for further evaluation. For example, in cases of bacterial septicemia, blood microbiological culture performed on an aseptically collected blood sample is an
important diagnostic test. Administration of systemic antibiotics prior to sample
collection, however, could lead to false-negative culture results and a missed
opportunity to isolate the bacterial pathogen.
Ideally, as results are evaluated and diagnosis proceeds, the list of differential
diagnoses is amended and shortened until a definitive diagnosis is reached. In reality,
however, the process may not get this far. In single or sporadic cases and turtles that
are already dead, the stage of disease at the time of presentation may be dominated
by secondary processes and particular samples may not have been collected at the
optimal time or in the appropriate manner to achieve a diagnosis. In some cases,
resources and availability limit the extent to which a case can be worked up. In
many cases, several alternative explanations or hypotheses will remain because
various tests fail to differentiate them, such tests do not exist for turtles, or the
etiology is complex or the specific etiology is unknown.
Diseases generally fall into two broad categories. First are those that are relatively straightforward and easily elucidated. However, the elucidation may require
evaluation of a series of affected individuals, even necropsy of several animals. This
is most successful in situations where a large case series is available for examination
or where the disease process is fairly well described in the literature, and recognized
by its clinical presentation and diagnostics. In the second category are those diseases
that are complex and have several causes that may work in concert to produce the
clinical presentation seen. For many clinical problems and pathologic processes that
can be described, the causes are yet to be identified. For example, algal toxins are
suspected to cause die-offs in marine turtles, but this has not yet been substantiated
in the literature for any marine turtle. Similarly, the full range of marine toxins that
could be involved has yet to be identified.
At the very least, however, the systematic approach outlined yields a collection
of objective data and observations (including the problems list), and a list of alternate
possibilities. The descriptive or pathologic diagnosis will at least characterize the
case so that future cases can be compared to it and one can plan how to proceed
with similar case presentations in the future, so that answers that are more thorough
1123 book.book Page 404 Monday, November 11, 2002 11:11 AM
The Biology of Sea Turtles, Vol. II
15.3.3.7 Assessment of Results, Amended Problems
and Differentials Lists, and Decisions
Throughout this process, decisions must be made about what additional tests to
perform, and whether to begin supportive therapy, attempt to treat and rehabilitate,
or euthanize and necropsy the animal. The goals of the investigation must be
considered; i.e., is one trying to cure the individual turtle or learn more about its
pathologic condition to help the population? These goals can be in extreme
conflict. In some cases, euthanasia of a mildly affected turtle in the early stages
of a disease can yield more information about the pathogenesis and etiology of
the disease. In some cases, treatment may eliminate the etiologic agent or introduce artifact. On the other hand, response to the specific therapy may aid in
diagnosis. Before a decision is made to treat, the investigative team should
consider whether they have performed the tests and obtained the samples needed
for further evaluation. For example, in cases of bacterial septicemia, blood microbiological culture performed on an aseptically collected blood sample is an
important diagnostic test. Administration of systemic antibiotics prior to sample
collection, however, could lead to false-negative culture results and a missed
opportunity to isolate the bacterial pathogen.
Ideally, as results are evaluated and diagnosis proceeds, the list of differential
diagnoses is amended and shortened until a definitive diagnosis is reached. In reality,
however, the process may not get this far. In single or sporadic cases and turtles that
are already dead, the stage of disease at the time of presentation may be dominated
by secondary processes and particular samples may not have been collected at the
optimal time or in the appropriate manner to achieve a diagnosis. In some cases,
resources and availability limit the extent to which a case can be worked up. In
many cases, several alternative explanations or hypotheses will remain because
various tests fail to differentiate them, such tests do not exist for turtles, or the
etiology is complex or the specific etiology is unknown.
Diseases generally fall into two broad categories. First are those that are relatively straightforward and easily elucidated. However, the elucidation may require
evaluation of a series of affected individuals, even necropsy of several animals. This
is most successful in situations where a large case series is available for examination
or where the disease process is fairly well described in the literature, and recognized
by its clinical presentation and diagnostics. In the second category are those diseases
that are complex and have several causes that may work in concert to produce the
clinical presentation seen. For many clinical problems and pathologic processes that
can be described, the causes are yet to be identified. For example, algal toxins are
suspected to cause die-offs in marine turtles, but this has not yet been substantiated
in the literature for any marine turtle. Similarly, the full range of marine toxins that
could be involved has yet to be identified.
At the very least, however, the systematic approach outlined yields a collection
of objective data and observations (including the problems list), and a list of alternate
possibilities. The descriptive or pathologic diagnosis will at least characterize the
case so that future cases can be compared to it and one can plan how to proceed
with similar case presentations in the future, so that answers that are more thorough
1123 book.book Page 404 Monday, November 11, 2002 11:11 AM