Dr. Sookun Rajeev K M.D Dept. Of Community Medicine
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Dr. Sookun Rajeev K
M.D
Dept. Of Community Medicine
Introduction
Medical Entomology is the science that deals with insects, arachnids and other arthropods which directly or indirectly affects the human beings
Also it is the study of the biology and control of offending arthropods and contributes to both public and individual health and well-being.
The most abundant form of animal life on earth
Out of some 1¼ 000000 known animal species, about 4⁄5th
belongs to arthropods.
The insects comprises about 70% of known species of all kinds of animals
Over 800 000 species of insects described so far.
Three quarters of a million species of insect have already been described and estimated number of about 1 million to 30 million are still pipelined.
Entomology (from Greek , entomos, "that which is cut in pieces or engraved/ segmented", hence "insect“
The term “Medical Entomology” is generally a misnomer cause not only insects but other members of phylum arthropoda are also included in the study.
Annoyance
Blood loss
Injury to sense organs
Dermatosis
Myiasis
Allergy
Anaphylactic shock
Envenomization
Entomophobia
Arthropods in relation to human health
Why are these arthropods so successful ???
Small size -there are many more niches for small organisms than for large organisms
Short life cycle - this allows many generations within a given time for selection and evolution to take place.
Large reproductive ability - large numbers of offspring support a large variation for selection and evolution to act upon.
Variation in the life style of different stages in an insect's life (e.g. caterpillar versus butterfly) reduces competition for resources within the species.
Wings-the ability to fly has allowed them to colonisefreely.
Sensory sophistication - the sensory capabilities surpasses most other organisms.
Evolutionary interactions with other organisms – co-evolution leads to greater specialisation and speciation.
Adaptation of appendages - mouthparts, wings and legs have often become highly specialised.
Modes of Disease Transmission by arthropods
1.Direct Contact-With the direct contact of hosts, the arthropod vectors gets
transferred from one host to the other.
e.g. pediculosis and scabies.
2. Mechanical transmission : The agent is mechanically transmitted by the arthropods on
the outside or inside their bodies
e.g. diseases transmitted by houseflies - diarrhoea, dysentery, cholera, hepatitis A & E etc.
3. Biological Transmission :
(a) Cyclo-developmental :
The agent undergoes cyclical changes but doesn’t multiplies in the body of arthopods, e.g. W. bancrofti (Filariasis) transmitted in Culexfemale.
(b)Cyclo-propagative :
The agent undergoes cyclical changes and also multiplies in the body of arthropods. Example is Plasmodium sp in Anopheles female.
(c)Propagative :
The agent undergoes no cyclical changes but simply grows and multiplies in the body of the vector, e.g. Plague bacilli in rat flea
Arthropods of medical importanceClass: Insecta Class: Arachnida Class: Crustacea
MosquitoesAnophelinesCulicines
TicksHard tickSoft tick
Cyclops
FliesHouseflySandflyTsese flyBlackfly
Mites (Chiggers)Leptotrombidium miteTromboculid miteItch mite
Human liceHead & body liceCrab lice
FleasRat fleaSand flea
Reduiid bug
Characteristics of Arthropods
The name arthropod actually comes from the Greek “arthro,” meaning joint, and “pod” meaning foot.
Invertebrates, Multicellular and body being bilaterally symmetrical
Body covered with hard chitinous exoskeleton
True segmentation of the body, each segment bearing a pair of joint appendages.
Have a wide range of chemical and mechanical sensors, mostly based on modifications of the many seatae (Bristles) that project through their cuticles
Muscles are straited
No ciliated epithelium.
Growth by periodical shedding of skin.
Jaws present.
Have compound eye, may be absent in some members
Sexes are separate.
The nervous system is dorsal (belly), the circulatory system is open and
ventral (back) and alimentary canal in between.
Body cavity called “Haemocele” have free communication with circulatory
system.
Characteristics of InsectsBody divided into Head, Thorax and Abdomen.
Head bears a single pair of Antenna
Have a pair of mandibles and two pairs of maxillae
Generally visual organs are compound eyes, maybe absent in some viz. fleas, pupiparan diptera
Thorax possess 3 pairs of legs and usually one or two pairs of wing.
Abdominal appendages are modified to terminal genital organs near cadual end of the body
Nervous and circulatory system of arthropods
Compound eye of arthopods Molding in arthropods
Insects of Medical Importance
Directly cause damage to human tissue
Act as Vectors for disease-causing organisms
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Provide useful medical services/drugs
Are useful model systems in genetic studies
Features of arthropods of medical importance
Insecta Arachnida Crustacea
Body division Head Thoraxabdomen
CephalothoraxAbdomen
(No division in some cases)
CephalothoraxAbdomen
Legs 3 pairs 4 pairs 5 pairs
Antennae 3 pairs None None
Wings One or two pairsSome are wingless
None
Where found On land On land In water
Class: Insecta
SAND FLY
Identifications• Like a mosquito, except its body is hairy and the wings are feathery.• Tiny insects (1-3 mm)• Smaller than mosquitoes• Hairs on body and wings• Wings rest over body like “angel’s” wings• Minute, hairy ,with wing kept erect while resting.• Large compound eyes• Hairy legs• Long slender legs• Wings are vertical and pointed• Whole body is covered with hairs• All 10 segments are abdomen are visible
Identifications
Male
• Posterior end of abdomen carries prominent claspers as stylus consisting the genitalia
Female
• Claspers absent but cercis are present which are small and round shape. Inside abdomen are a pair of spermatheca
Only females suck blood.
Live in warm climates.
Breed in crack of soil and wall, rubbish heaps.
Move in hops rather than fly.
Nocturnal ,during day time rest in cool damp places.
Vector of leishmaniasis, sand fly fever.
Sand Fly
Genitalia
Male Female
Diseases Transmitted
• The sandflies are responsible for the transmission of:
1. kala- azar (P. argentipes),
2. oriental sore (P. papatasii and P. sergenti)
3. sandfly fever (P. papatasii and P. punjabensis).
Control Measures
•Breeding is prevented by filling cracks and cervices on the walls and removing any stone or rock piles.
•The adults are killed by indoor residual spray insecticides like DDT and lindane in concentrations of 1-2 and 0.25 g per square metre respectively.
•Repellents used on clothes or applied to skin such as deet, DMP, etc. are effective against
ANOPHELES
The Anopheles Mosquito• About 380 species of Anopheles occur around the world
• Some 60 species are sufficiently attracted to humans to act as vectors of malaria
• A number of Anopheles species are also vectors of filariasis and viral diseases.
• Female Anopheles mosquito spread the disease. 27
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• The anophelines that enter houses to feed often rest indoors for a few hours after feeding.
• They may then leave for outdoor sheltered resting sites, among them vegetation, rodent burrows, cracks and crevices in trees or in the ground, caves and the undersides of bridges.
• Many Anopheles species feed on both humans and animals.
• They differ, however, in the degree to which they prefer one over the other.
• Some species feed mostly on animals while others feed almost entirely on humans.
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• The most preferred breeding sites are pools, seepages, quiet places in slow-running streams, rice fields, leaf axils of certain epiphytic plants and puddles of rainwater.
• Artificial containers, such as pots, tubs, cisterns and overhead tanks are not usually suitable.
• Anopheles mosquitos are active between sunset and sunrise.
• Each species has specific peak biting hours, and there are also variations in their preference for biting indoors or outdoors.
Identifications
Male Anophelene
• Maxillary palpi is equal in length to proboscis.
• Palpi are club shape at the tip
• Antenna are hairy
• Clasper or style is the terminalia
Female Anophelene
• Maxillary palpi is equal in length to proboscis
• Palpi are not club shaped but straight
• Antenna are sparsely hairy or even absent
• Palps are as long as their proboscis
• Cerci is the terminalia
Diseases Transmitted
1. Malaria – P.Vivax, P.Falciparum, P.Malariae
2. Black water fever – P.Vivax, P.Falciparum, P. Malariae
3. Cerebral Malaria –P.Falciparum
Control Measures1. Anti-Larval measures
a)Environmental control:
Eliminating breeding places and reducing source of transmission (e.g. by filling, leveling, drainage of breeding places and water management.
b)Chemical control :
Use of mineral oils (diesel, fuel oil, kerosene), paris green, synthetic insecticides (Fenthion, chlorpyrifos).
c)Biological control:
Use of Gambusia Affinis (mosquitofish) and Lebistes Reticulatus in pits, sewage ponds, farm ponds etc…
2. Anti-Adult measures:
a) Residual Sprays : Malathion, DDT, Propoxur
b) Space Sprays : Pyrethrum , fenitrothion.
c) Genetic control : Sterile male technique, sex distortion, gene replacement, cytoplasmic Incompatibility etc..
3. Protection against mosquito bites:
a) Mosquito nets
b) Screening with copper or bronze gauze
c) Repellant : Diethyltoluamide, Indalone, dimethyl carbate
CULEX MOSQUITO
The Culex Mosquito•Culex sp is a markedly domestic species
• The adult females bite people and animals throughout the night, indoors and outdoors
• During the day they are inactive and are often found resting in dark corners of rooms, shelters and culverts
• They also rest outdoors on vegetation and in holes in trees in forested areas
Identifications
Male
• Maxillary palps is larger than proboscis. They are bent outward with pointed tips.
• The antenna are hairy
• Claspers or style is the terminalia.
Female
• Maxillary palps are 1/3 of proboscis.
• The antenna are small and little hairy
• Cerci is the terminalia.
Male Female
Culex Mosquito Heads
Diseases Transmitted
• Arbovirus infections
• West Nile Virus
• Filariasis
• Japanese Encephalitis
• St. Louis Encephalitis
• Avian Malaria
Control Measures1. Anti-Larval measures
a)Environmental control:
Eliminating breeding places and reducing source of transmission (e.g. by filling, leveling, drainage of breeding places and water management.
b)Chemical control :
Use of mineral oils (diesel, fuel oil, kerosene), paris green, synthetic insecticides (Fenthion, chlorpyrifos).
c)Biological control:
Use of Gambusia Affinis (mosquitofish) and Lebistes Reticulatus in pits, sewage ponds, farm ponds etc…
2. Anti-Adult measures:
a) Residual Sprays : Malathion, DDT, Propoxur
b) Space Sprays : Pyrethrum , fenitrothion.
c) Genetic control : Sterile male technique, sex distortion, gene replacement, cytoplasmic Incompatibility etc..
3. Protection against mosquito bites:
a) Mosquito nets
b) Screening with copper or bronze gauze
c) Repellant : Diethyltoluamide, Indalone, dimethyl carbate
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