386
The Biology of Sea Turtles, Vol. II
15.3.3.6 Specialized Examinations, Procedures,
and Secondary Tests ........................................................403
15.3.3.7 Assessment of Results, Amended Problems
and Differentials Lists, and Decisions ............................404
15.4 Costs–Benefits .............................................................................................405
15.5 Conclusion ..................................................................................................408
References ............................................................................................................408
15.1 INTRODUCTION AND BACKGROUND
Interest in health and disease of sea turtles has increased along with a general interest
in wildlife and environmental health. Dramatic epizootic events such as marine turtle
fibropapillomatosis (FP), regional coral die-offs, toxic algal blooms, and amphibian
population declines as well as concern for the effects of pesticides, industrial contaminants, and climate change on human and wildlife populations have spurred an
interest in incorporating health assessment and disease surveillance into population
monitoring programs.
As these programs are developed and implemented, it will be important to gain
an appreciation of the potential role that pathogens and infectious diseases may have
as primary mortality factors in the population ecology of these species. For some
wildlife ecologists, the concept of infectious disease is traditionally understood as
an epiphenomenon or secondary process that follows a primary environmental stressor, such as resource depletion. The presumption is that through host–parasite (pathogen) coevolution, a normal unstressed host will tend to be resistant to disease from
infectious agents.
Although this conceptual view may hold true for diseases caused by opportunistic pathogens, a broader understanding of host–pathogen interactions recognizes
that there are theoretical conditions under which natural selection would not drive
host and parasite coadaptations toward a less antagonistic relationship (Ewald, 1993;
May and Anderson, 1983). Furthermore, even in situations where selection does
drive the relationship toward low virulence, the relationship is probably not an
evolutionarily stable strategy in that the system remains susceptible to invasion by
highly virulent strains that gain a tremendous short-term fitness advantage (MaynardSmith, 1976). Given that new and highly virulent strains can evolve and spread
rapidly at a higher rate than a vertebrate host’s ability to respond, there will always
be the possibility that an infectious agent is a primary morbidity–mortality factor,
stressing and killing otherwise healthy sea turtles. Furthermore, the human impact
on our environment is greater today than ever before, and in both subtle and not
such subtle ways, humans may be affecting the spread of pathogens throughout the
world. Thus, it should be assumed that new diseases may appear and a condition
that is sporadic one year may become catastrophic the next. Consequently, there is
value in investigating the pathophysiology of disease (disease research), in monitoring for disease and health problems, and in preparing at some level to cope with
disease outbreaks.
1123 book.book Page 386 Monday, November 11, 2002 11:11 AM
The Biology of Sea Turtles, Vol. II
15.3.3.6 Specialized Examinations, Procedures,
and Secondary Tests ........................................................403
15.3.3.7 Assessment of Results, Amended Problems
and Differentials Lists, and Decisions ............................404
15.4 Costs–Benefits .............................................................................................405
15.5 Conclusion ..................................................................................................408
References ............................................................................................................408
15.1 INTRODUCTION AND BACKGROUND
Interest in health and disease of sea turtles has increased along with a general interest
in wildlife and environmental health. Dramatic epizootic events such as marine turtle
fibropapillomatosis (FP), regional coral die-offs, toxic algal blooms, and amphibian
population declines as well as concern for the effects of pesticides, industrial contaminants, and climate change on human and wildlife populations have spurred an
interest in incorporating health assessment and disease surveillance into population
monitoring programs.
As these programs are developed and implemented, it will be important to gain
an appreciation of the potential role that pathogens and infectious diseases may have
as primary mortality factors in the population ecology of these species. For some
wildlife ecologists, the concept of infectious disease is traditionally understood as
an epiphenomenon or secondary process that follows a primary environmental stressor, such as resource depletion. The presumption is that through host–parasite (pathogen) coevolution, a normal unstressed host will tend to be resistant to disease from
infectious agents.
Although this conceptual view may hold true for diseases caused by opportunistic pathogens, a broader understanding of host–pathogen interactions recognizes
that there are theoretical conditions under which natural selection would not drive
host and parasite coadaptations toward a less antagonistic relationship (Ewald, 1993;
May and Anderson, 1983). Furthermore, even in situations where selection does
drive the relationship toward low virulence, the relationship is probably not an
evolutionarily stable strategy in that the system remains susceptible to invasion by
highly virulent strains that gain a tremendous short-term fitness advantage (MaynardSmith, 1976). Given that new and highly virulent strains can evolve and spread
rapidly at a higher rate than a vertebrate host’s ability to respond, there will always
be the possibility that an infectious agent is a primary morbidity–mortality factor,
stressing and killing otherwise healthy sea turtles. Furthermore, the human impact
on our environment is greater today than ever before, and in both subtle and not
such subtle ways, humans may be affecting the spread of pathogens throughout the
world. Thus, it should be assumed that new diseases may appear and a condition
that is sporadic one year may become catastrophic the next. Consequently, there is
value in investigating the pathophysiology of disease (disease research), in monitoring for disease and health problems, and in preparing at some level to cope with
disease outbreaks.
1123 book.book Page 386 Monday, November 11, 2002 11:11 AM