Medical entomology focuses on the role of arthropods in public health, particularly as vectors for diseases. This document explores various types of vectors, including mosquitoes, flies, and fleas, detailing their life cycles and the diseases they transmit. It provides insights into vector dynamics, transmission methods, and effective control measures for managing infestations. The content is essential for public health professionals and students studying entomology and disease prevention. It covers breeding habits, anti-larval and anti-adult measures, and personal protection strategies against vector-borne diseases.

Key Points

  • Explains vector dynamics and types of transmission in medical entomology
  • Details the life cycles and breeding habits of mosquitoes and other vectors
  • Covers mosquito-borne diseases prevalent in India, including malaria and dengue
  • Discusses effective control measures for managing vector populations
Sasi Tharoor
13 pages
Language:English
Type:Textbook
Parasitology
Sasi Tharoor
13 pages
Language:English
Type:Textbook
Parasitology
173
/ 13
MEDICAL ENTOMOLOGY
Entomology is the study of arthropods. There importance in public health are:
They act as vectors to spread diseases
They may themselves cause disease (lice, scabies mite)
They destroy crops and reduce food production.
Vector dynamics
A ‘vector’ is an organism which transmits disease
1. By inoculation into or through the skin/mucous membranes by biting
2. By depositing the agents on skin/food fomites.
Types of transmission
1. Direct contact—Scabies, pediculosis (lice).
2. Indirect contact—Scabies and lice may spread through fomites.
3. Mechanical transmission—Houseflies transport many pathogenic agents
over their body.
4. Biologic transmission— When the disease agent multiplies or undergoes
some developmental change with or without multiplication in the arthropod
host, it is called biological transmission.
This may be of three types :
(a) Propagative : When the disease agent undergoes no cyclical change, but
multiplies in the body of the vector, e.g., plague bacilli in rat fleas
(b) Cyclopropagative : The disease agent undergoes cyclical change, and
multiplies in the body of the arthropod, e .g., malaria parasite in anopheline
mosquito
(c) Cyclo-developmental : When the disease agent undergoes cyclical
change but does not multiply in the body of the arthropod, e.g., filarial
parasite in culex mosquito and guinea worm embryo in cyclops.
Extrinsic incubation period ; The time required for the infective form to
develop within the vector (i.e. sporozoites of Plasmodium develop inside
mosquito in about 10 days).
Vector ‘infestation’: This is distinct from a parasitic infestation. A vector is
infested when it lodges and multiplies in a surface, be it body or clothing, etc.
Class Insecta Class Arachnida Class Crustacea
MOSQUITOES
Anophilies
Aedes
Culex
M
ansoni
TICKS
Hard ticks
Soft ticks
CYCLOPES
FLIES
Houseflies
Sandflies
Tsetse flies
Black flies
MITES
Leptotrombidium and
trombiculid mites
Itch mite
HUMAN LICE
Head and body lice
FLEAS
Rat flea
Sand flea
Reduvid bug
Distinctive characters of arthropods of medical importance
Class Insecta Class Arachnida Class Crustacea
Body
divisions
Head thorax
abdomen
Cephalothorax and
abdomen (no division )
in some case
Cephalothorax
and abdomen
Legs 3 pair 4 pairs 5 pairs
Antenna
1 pair None 2pairs
Wings 1 or 2 pairs; some
are wingless
None None
Found in On land On land In water
MOSQUITO
The four important groups of mosquitoes in India are :
Anopheles
Culex
Aedes
Mansonia.
The body of a mosquito consists of three parts:
(a) HEAD : The head is semi-globular in outline, and bears the following
structures :-
1) a pair of large compound eyes
2) a long proboscis (needle-like structure) with which the mosquito bites
3) a pair of palpi on either side of the proboscis
4) a pair of antennae or feelers. (male- bushy, female-less bushy)
(b) THORAX: The thorax is large and rounded in appearance and bears :-
(i) a pair of wings dorsally.
(ii) three pairs of legs ventrally.
(c) ABDOMEN : composed of 10 segments, the last two are modified to form
the external genitalia.
Four stages of development of mosquitos are;
/ 13
End of Document
173

You May Also Like

FAQs

What are the types of transmission for disease vectors?
Disease vectors transmit diseases through various methods, including direct contact, where diseases like scabies and lice spread directly between hosts. Indirect contact can occur through fomites, such as clothing or bedding. Mechanical transmission involves organisms like houseflies transporting pathogens on their bodies, while biological transmission occurs when the disease agent multiplies or undergoes changes within the vector. Biological transmission can be further classified into propagative, cyclopropagative, and cyclo-developmental types, depending on the relationship between the vector and the disease agent.
What are the four important groups of mosquitoes in India?
The four significant groups of mosquitoes in India are Anopheles, Culex, Aedes, and Mansonia. Each group has distinct breeding habits and is associated with various mosquito-borne diseases. For instance, Anopheles is primarily known for transmitting malaria, while Aedes is linked to diseases like dengue and chikungunya. Understanding these groups is crucial for implementing effective control measures against the diseases they spread.
How do Anopheles mosquitoes breed?
Anopheles mosquitoes prefer to breed in clean, oxygenated water, which is essential for their larvae. Unlike other mosquito groups, Anopheles larvae do not require a siphon tube to breathe, as they can obtain oxygen directly from the water. This preference for clean water sources highlights the importance of habitat management in controlling their populations and preventing the spread of diseases like malaria.
What control measures are effective against mosquito larvae?
Effective anti-larval measures include the use of mineral oils, which create a barrier over water surfaces to block oxygen entry. Chemicals such as Paris green are particularly useful for targeting Anopheles mosquitoes, while insecticides like abate and malathion have proven effective against various mosquito larvae. Additionally, introducing predatory fish, such as Gambusia affinis, can naturally reduce mosquito larvae populations in breeding sites.
What diseases are caused by Culex mosquitoes?
Culex mosquitoes are responsible for transmitting several diseases, including Bancroftian filariasis, Japanese encephalitis, West Nile fever, and viral arthritis. These diseases can have significant public health implications, making it essential to understand the breeding habits and control measures for Culex mosquitoes to reduce their impact on communities.
What are the life cycle stages of houseflies?
Houseflies undergo four stages in their life cycle: egg, larva, pupa, and adult. The female lays approximately 120 to 150 eggs in moist organic matter, which hatch into larvae or maggots. These larvae are footless and segmented, feeding on organic debris. After a period of development, they pupate into dark brown, barrel-shaped pupae before emerging as adult flies. The entire life cycle can be completed in 5 to 6 days during summer.
What are the control measures for rat fleas?
Control measures for rat fleas include insecticidal treatments, such as 10 percent DDT dust, which is applied to floors and walls. This method targets fleas that infest rodents. In cases of resistance, alternatives like carbaryl or diazinon can be effective. Additionally, treating animal hosts, such as cats and dogs, with insecticidal dusts or sprays is crucial for comprehensive flea management.

Related