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Gene R. DeFoliart
disaster struck in 1971 when epidemic Venezuelan equine encephalitis (VEE)
surged into Texas, resulting in more than 1500 equine deaths and 110 human
cases (Sudia et at., 1975). More than 3 million horses were vaccinated and more
than 8 million acres were sprayed with insecticide before this invasion was
brought under control.
The preceding are only some of the more notable examples. Tick-borne
Kyasanur Forest Disease virus and mosquito-borne West Nile virus occur in
India, and there are several important mosquito-borne encephalitis viruses in the
United States. Leishmaniasis, both visceral and cutaneous, is endemic to India,
and large-scale epidemics numbering up to 20,000 cases were not infrequent
prior to 1953. Some Indian workers predict a comeback for leishmaniasis if for
any reason intradomiciliary spraying for malaria control should cease (Shanmugham et at., 1977; Sharma et at., 1973a,b). Bubonic plague, which harassed
India until the mid-twentieth century with 12.5 million deaths between 1896 and
1948, and an outbreak of 600 cases as recently as 1962 in Mysore State (Wattal,
1971), still lurks in sylvatic foci in both countries. Although human cases are
sporadic, continued vigilance will be essential.
8.2. THE NA TURE AND DIVERSITY OF ARTHROPODBORNE DISEASE
The majority of arthropod-borne disease agents are, in Pavlovsky's
terminology, zooanthroponoses, i.e., disease agents perpetuated in wild vertebrate-arthropod cycles that infect man only incidentally. Man becomes infected
by entering the orbit of the wild cycles or occasionally they spill over in epidemic
proportions into human populations. The enzootic foci of most of these zooanthroponoses are so widely dispersed that there is little or no hope for their
elimination in the foreseeable future. The main line of defense against these
agents is good surveillance and the ability to quickly mobilize vector control
technology when an epidemic threatens.
Anthroponoses, i.e., disease agents transmissible directly from human to
human via an arthropod vector (no extrahuman reservoir) seem generally more
amenable to elimination or containment by vector control and/or other means.
Even these agents present extremely complex challenges, however, as demonstrated by the resurgence of malaria in many areas, and by the recurring epidemics
of dengue in both Eastern and Western Hemispheres.
One cannot help but marvel at the uneven state of the art in medical entomology. On the one hand we embarked on the global eradication of malaria;
on the other hand, after 100 years, we do not know how to make an imbedded
tick detach voluntarily from one of our own appendages. Undoubtedly this is
Gene R. DeFoliart
disaster struck in 1971 when epidemic Venezuelan equine encephalitis (VEE)
surged into Texas, resulting in more than 1500 equine deaths and 110 human
cases (Sudia et at., 1975). More than 3 million horses were vaccinated and more
than 8 million acres were sprayed with insecticide before this invasion was
brought under control.
The preceding are only some of the more notable examples. Tick-borne
Kyasanur Forest Disease virus and mosquito-borne West Nile virus occur in
India, and there are several important mosquito-borne encephalitis viruses in the
United States. Leishmaniasis, both visceral and cutaneous, is endemic to India,
and large-scale epidemics numbering up to 20,000 cases were not infrequent
prior to 1953. Some Indian workers predict a comeback for leishmaniasis if for
any reason intradomiciliary spraying for malaria control should cease (Shanmugham et at., 1977; Sharma et at., 1973a,b). Bubonic plague, which harassed
India until the mid-twentieth century with 12.5 million deaths between 1896 and
1948, and an outbreak of 600 cases as recently as 1962 in Mysore State (Wattal,
1971), still lurks in sylvatic foci in both countries. Although human cases are
sporadic, continued vigilance will be essential.
8.2. THE NA TURE AND DIVERSITY OF ARTHROPODBORNE DISEASE
The majority of arthropod-borne disease agents are, in Pavlovsky's
terminology, zooanthroponoses, i.e., disease agents perpetuated in wild vertebrate-arthropod cycles that infect man only incidentally. Man becomes infected
by entering the orbit of the wild cycles or occasionally they spill over in epidemic
proportions into human populations. The enzootic foci of most of these zooanthroponoses are so widely dispersed that there is little or no hope for their
elimination in the foreseeable future. The main line of defense against these
agents is good surveillance and the ability to quickly mobilize vector control
technology when an epidemic threatens.
Anthroponoses, i.e., disease agents transmissible directly from human to
human via an arthropod vector (no extrahuman reservoir) seem generally more
amenable to elimination or containment by vector control and/or other means.
Even these agents present extremely complex challenges, however, as demonstrated by the resurgence of malaria in many areas, and by the recurring epidemics
of dengue in both Eastern and Western Hemispheres.
One cannot help but marvel at the uneven state of the art in medical entomology. On the one hand we embarked on the global eradication of malaria;
on the other hand, after 100 years, we do not know how to make an imbedded
tick detach voluntarily from one of our own appendages. Undoubtedly this is