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INTRODUCTION Medical Entomology (Contact) Please CLICK on underlined links for details: Arthropods & Disease Aspects
of Disease Transmission Key References Arthropoda
play a role in human welfare that is poorly understood by the general public.
Most oceanic animal life is not the larger fishes and mammals, but tiny
animals that make up the greater part of the plankton: the free-swimming, minute Crustacea on which
other inhabitants rely for food. These free-living plant-feeding scavengers
occur in vast numbers and interact with other animals to reduce the numbers
of those that expire. Similarly the insects exhibit a more dominant role.
Because of their large numbers and high adaptation for survival they outrank
in abundance other animal or plant associations. It has been impossible to estimate the number of ants that
populate fields and hillsides or the plant lice that derive sustenance from
wild and cultivated plants. The role that insects play in agriculture and
commerce is especially underestimated for the losses agriculture suffers from
their destructive feeding. But for human welfare the insects especially are
of paramount importance as they can regularly affect human's very existence
or retard advances in the development of some of the earth's most fertile
regions. Governments have fallen due
to the ravages of diseases spread by arthropods. A notable example is the defeat of the British Army during the
American Revolutionary War due to a widespread epidemic of malaria among the British
troops. The Americans were able to
rely heavily on the labors of the African population for food and supplies
because they had a built in resistance to the disease from millennia of
coexistence in Africa. Medical entomology and parasitology
are important academic fields for zoologists, physicians and the public.
There is a constant need for more knowledge of the interrelations, which
arthropods play in the spread, and maintenance of plant, animal, and human
diseases. Insects especially have gradually made governments devote resources
to long delayed studies. Some of the
prominent early researchers in this field may be viewed at <Researchers>. There are many important diseases
associated with arthropods. Some of
the more important ones include Malaria, Piroplasmosis, Trypanosomiasis, Yellow
Fever, Plague, Dengue, Phlebotomus Disease, Spirochetal Diseases,
Tsutsugamushi Disease, Kedani Fever, Flood Fever, Japanese River Fever, Rocky
Mountain Spotted Fever, Typhus Fever, Tularemia, and Onchocerciasis. It is important also to consider the
mechanical movement of pathogenic organisms by insects, especially filth
flies. Since early times ordinary people and physicians associated flies with
disease outbreaks. An abundance of flies during summer was associated with an
unhealthy autumn. There are also
animal diseases other than those of man, where insects are involved and which
influence human welfare. For example,
insects play an important role as vectors of plant diseases thereby affecting
the food supply. In the gut of many insects are found representatives of the
protozoan family Trypanosomidae, with generic names Crithidia, Herpetomonas, Phytomonas,
Leishmania, Leptomonas. The relationships of some of these forms to animal and plant
diseases are known but the majority of them remain undetermined. The problem
of isolating and culturing these forms, and of determining their relation to
the insects, to other animals, and to plants is extremely difficult. However,
progress has been accelerating with the development of DNA analyses, and we
may expect more exact information in the future. ASPECTS
OF DISEASE TRANSMISSION In the study of insect-borne disease, particularly
one in which the insect serves as the definitive or intermediate host,
certain important considerations are essential. Some of the more important features of the various factors
involved are (1) the parasite or etiological agent; (2) the definitive host.
and the definitive reservoirs or non-reservoirs; (3) the method of
transmission; (4) the intermediate host and the intermediate reservoirs or
no-reservoirs; (5) the method of transmission. There is a lack of understanding,
however, even of the better-known insect-borne diseases. For instance, in malaria is is apparent
that the only definite host reservoirs are Anopheles
spp. mosquitoes, but how long they can remain infected is still uncertain.
The number of Anopheles species
that can act and the conditions under which they may serve as definitive
hosts are still not well known, though much progress has been made toward
solving these problems. In yellow fever the parasitic agent is a virus; but
the animal reservoirs been determined only since the late 1800's. Also, not all the mosquito transmitters
have been recognized. Many problems of sleeping sickness remain
unsolved. However, data on all known
insect-borne diseases can be assembled and the numerous unsolved problems
pointed out. The literature dealing with medical entomology, parasitology,
and preventative medicine is vast, and bacteriology and veterinary medicine
should be included,
Key References: <medvet.ref.htm> Matheson, R. 1950.
Medical Entomology. Comstock
Publ. Co, Inc. 610 p. Service, M. 2008. Medical
Entomology For Students. Cambridge
Univ. Press. 289 p Legner,
E. F. 1995. Biological control of Diptera of medical
and veterinary importance. J. Vector
Ecology 20(1): 59-120. Legner, E. F.. 2000.
Biological control of aquatic Diptera. p. 847-870.
Contributions to a Manual of Palaearctic Diptera, Vol.
1, Science Herald, Budapest. 978 p. |