3. Arthropods of medical importance
Class: Insecta Class: Arachnida Class: Crustacea
1. Mosquitoes:
• Anophelines
• Culicines
2. Flies:
• Houseflies
• Sandflies
• Tsetse flies
• Blackflies
3. Human lice:
• Head and body lice
4. Fleas:
• Rat fleas
• Sand fleas
5. Reduviid bugs
1. Ticks :
• Hard ticks
• Soft ticks
2. Mites :
• Trombiculd mites
• Itch mite
Cyclops
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4. Distinctive characters
Insecta Arachnida Crustacea
1. Body divisions Head
Thorax
Abdomen
Cephalothorax and
abdomen
Cephalothorax
and abdomen
2. Legs 3 pairs 4 pairs 5 pairs
3. Antenne 1 pair None 2 pairs
4. Wings One or two
pairs
None None
5. Where found On land On land On land
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7. Transmission of arthropod- borne diseases
By 3 types:-
1. Direct contact:
• Arthropods are directly transferred from man to man
through close contact, e.g. scabies and pediculosis.
2. Mechanical Transmission:
• The disease agent is transmitted mechanically by the
arthropod, e.g. diarrhoea, dysentery, typhoid, food poisoning
by the housefly.
3. Biological Transmission:
• Disease agent multiplies or undergoes some developmental
change with or without multiplication in the arthropod
host. This may be of 3 types; 7
8. Types of Biological Transmission:
a) Propagative-
• Disease agent undergoes no cyclical change, but
multiplies in the body of the vector;
e.g.- plague bacilli in rat fleas
b) Cyclo-propagative-
• Disease agent undergoes cyclical change and multiplies
in the body of the arthropod;
e.g.- malaria parasite in anopheline mosquito
c) Cyclo-developmental-
• Disease agent undergoes cyclical change but does not
multiply in the body of arthropod;
e.g.- filarial parasite in culex mosquito 8
9. Principles of Arthropod control
1. Environmental control
2. Chemical control
3. Biological control
4. Genetic control
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10. 1. Environmental control of arthropods
• Best approach, because results are likely to be permanent,
• Elimination of breeding places ( source reduction)
• Filling and drainage operation
• Carefully planned water management
• Provision of piped water supply
• Proper disposal of wastes
• Cleanliness in and around houses etc.
• Health education
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11. 2. Chemical control of arthropods
• Insecticides available for vector control-
Organo-chlorine compounds- DDT, BHC, Lindane
Organo-phosphorus compounds- Malathion
Carbamate groups- Carbaryl, Propoxur
• Insecticides alone are no longer fully effective
because resistance has appeared in over 100
species of medically important arthropods.
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12. 3. Biological control of arthropods
• By larvicidal fish ‘Gambusia’ and ‘Lebister’
• Fungi of genus Coelomomyces
This method is effective only when used in conjunction
with other methods.
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13. 4. Genetic control of arthropods
Techniques-
• Sterile male technique
• Cytoplasmic incompatibility
• Chromosomal translocation
• Sex distortion
• Gene replacement
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14. Newer methods
• Insect growth regulators
• Chemosterilants
• Sex attractants or pheromons.
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15. Present Trends
• To adopt an ‘Integrated Approach’ for vector
control.
• Combining two or more methods to obtain
maximum results with minimum efforts.
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