226
Gene R. DeFoliart
or O.lImin? Is either of these rates acceptable in the situation pertaining? For
what period of time does the target species ordinarily occur at densities above
the tolerance limit, thereby dictating the number of applications necessary and
the seasonal cost of the procedure per unit of area?
Similarly with larvicides, if a larvicide at a range of dosage rates produces
high mortality for 7, 14, and 21 days, respectively, what does this mean relative
to its possible utilization against specific targets having, for example, synchronous or asynchronous broods? Again, depending on the biology of the target
species, how many applications will be needed per season, so that comparative
costs of treatments can be estimated? A high proportion of our published technology testing is largely a comparison of mortalities achieved at a range of
dosage rates with little attempt to describe how the results might be useful in
relation to a real problem that exists.
The tolerance limit in the case of vectors is more difficult to define. But
the critical initial question is not whether a vector population can be reduced by
80-90% using a particular control method, but to what level must the population
be reduced in order to interrupt transmission in endemic foci, or lacking that,
to prevent or reduce transmission to human populations at risk. More, and more
precise, epidemiological models are needed from which critical vector population
levels can be predicted and, therefore, the degree of control that must be exerted.
Disease Control through Public Education. A recently launched program
in South Carolina (Burgdorfer et al., 1975) is a good example of an effort to
apply existing knowledge, imperfect as it may be, to reduce the incidence of
human cases of a zoonotic disease. Rocky Mountain spotted fever (Rickettsia
rickettsii), the major tick-borne disease in the United States, is a disease that is
benefiting from new technology, but in addition requires management beyond
scientific endeavor. Like most arthropod-borne diseases of importance in the
United States, it is a zooanthroponosis and there is no chance that it can be
eradicated. The rickettsia is maintained in nature in cycles involving several tick
vectors and their host mammals (Burgdorfer, 1975).
In the eastern United States increased suburbanization and recreation have
brought people into closer contact with the zoonotic foci with the result that the
annual number of reported cases increased from fewer than 200 in 1959 to 1118
in 1977. Despite the fact that cases recover when treated properly with broadspectrum antibiotics, the yearly case fatality rates have varied between 3% and
10% since 1948 (Hattwick, et al., 1973). Deaths result because people fail to
seek proper medical care and because physicians are not familiar with the disease
and do not recognize it, particularly in its early stages, thereby delaying specific
treatment.
Research advances hold promise in the future for development of effective
vaccines. In the meantime, the hemolymph test, in conjunction with direct ftu-
Gene R. DeFoliart
or O.lImin? Is either of these rates acceptable in the situation pertaining? For
what period of time does the target species ordinarily occur at densities above
the tolerance limit, thereby dictating the number of applications necessary and
the seasonal cost of the procedure per unit of area?
Similarly with larvicides, if a larvicide at a range of dosage rates produces
high mortality for 7, 14, and 21 days, respectively, what does this mean relative
to its possible utilization against specific targets having, for example, synchronous or asynchronous broods? Again, depending on the biology of the target
species, how many applications will be needed per season, so that comparative
costs of treatments can be estimated? A high proportion of our published technology testing is largely a comparison of mortalities achieved at a range of
dosage rates with little attempt to describe how the results might be useful in
relation to a real problem that exists.
The tolerance limit in the case of vectors is more difficult to define. But
the critical initial question is not whether a vector population can be reduced by
80-90% using a particular control method, but to what level must the population
be reduced in order to interrupt transmission in endemic foci, or lacking that,
to prevent or reduce transmission to human populations at risk. More, and more
precise, epidemiological models are needed from which critical vector population
levels can be predicted and, therefore, the degree of control that must be exerted.
Disease Control through Public Education. A recently launched program
in South Carolina (Burgdorfer et al., 1975) is a good example of an effort to
apply existing knowledge, imperfect as it may be, to reduce the incidence of
human cases of a zoonotic disease. Rocky Mountain spotted fever (Rickettsia
rickettsii), the major tick-borne disease in the United States, is a disease that is
benefiting from new technology, but in addition requires management beyond
scientific endeavor. Like most arthropod-borne diseases of importance in the
United States, it is a zooanthroponosis and there is no chance that it can be
eradicated. The rickettsia is maintained in nature in cycles involving several tick
vectors and their host mammals (Burgdorfer, 1975).
In the eastern United States increased suburbanization and recreation have
brought people into closer contact with the zoonotic foci with the result that the
annual number of reported cases increased from fewer than 200 in 1959 to 1118
in 1977. Despite the fact that cases recover when treated properly with broadspectrum antibiotics, the yearly case fatality rates have varied between 3% and
10% since 1948 (Hattwick, et al., 1973). Deaths result because people fail to
seek proper medical care and because physicians are not familiar with the disease
and do not recognize it, particularly in its early stages, thereby delaying specific
treatment.
Research advances hold promise in the future for development of effective
vaccines. In the meantime, the hemolymph test, in conjunction with direct ftu-