Download House fly and other flies

House fly and other flies
SESSION24
Introduction
House fly and other flies belong to order Diptera.
Many species are disease transmitters to human via
- mechanical (eg: house fly)
- biological (eg: sand fly)
Dipterous larvae cause internal infestation (myiasis)
by invasion of mammalian tissue.
Classification
- Phylum – Arthropoda
- Class - Insecta
- Order - Diptera
Flies can be divided into two categories.
1. Non blood sucking flies
2. Blood sucking flies
Flies of medical importance
Non blood sucking flies
Blood sucking flies
-Musca domestica
-Sarcophaga
-Chrysomia
-Phlebotomus (sand fly)
-Simulium (black fly)
-Chrysops (deer fly)
-Glossina spp. (tsetse fly)
Non blood sucking flies
- Mouth parts are adapted for sucking liquids or minute
particles
- Live under filthy conditions
Medical importance of flies
- Mechanical transmission of pathogens
- Parasitic activities of larvae
1. Musca domestica (house fly)
Widely spread all over the world.
Morphology
- A medium size fly but varies according to the region of
the world
- The body comprised of head, thorax and abdomen
- The size is 6-9mm
- Light or dark grey colored body
- Thorax has 4 longitudinal lines
- It has 3 pairs of legs ending in a pair of claws and pads
with sticky glandular hair
- Musca domestica has a characteristic wing venation
House fly (Musca domestica)
House fly leg
House fly wing
Life cycle of Musca domestica
-
Life cycle has 4 stages (egg, larva, pupa and adult)
-
Breeds in domestic and garden refuse, animal dung, garbage bumps, rotting
vegetable matter and night soil.
-
Eggs hatch within 12-24 hours depending upon the environmental conditions
-
There are three stages of larvae as L1, L2 and L3
-
Larvae live 3-7 days
-
The fully grown 3rd stage larvae move away from the breeding material to ground
(dry area) to become the pupae.
-
The pupal stage lasts only 4-6 days and the adult fly emerge from it.
-
The time taken for the completion of the life cycle from egg to adult varies (3-26
days) , but it may be as short as 8-19 days.
Life cycle of house fly
Musca domestica eggs
- Adults lay eggs on decaying organic matter or rotting
material
- Eggs are creamy white in colour
- They look like rice grains
- Eggs are laid in batches of 100-200
Musca domestica larvae (maggots)
- Larvae have a white, segmented body
- The body is conical in shape with a pointed anterior end
and a broad posterior end
- The 1st body segment bears a pair of mouth hooks
- Last segment of the body consists of a pair of spiracles with
a characteristic pattern in cross section (helps for
identification)
Musca domestica Pupa
- Colour of the pupa is brown or black
- It is barrel shaped
Musca domestica habits
- Live with close proximity to human habitats.
- House fly has the habit of cleaning the head and proboscis with
legs after feeding.
- They also regurgitate and vomit on to the surface they land and
constantly defecate on food.
- House flies feed on human and animal food.
Medical importance
1. Mechanical vector of pathogenic bacteria, virus, protozoa,
helminth eggs and larvae
eg: - Bacteria – typhoid, cholera
- Virus – polio, hepatitis
- Protozoa – amoebic dysentry, giardiasis
- Helminths – Necator, Ascaris
2. Myiasis by larvae
Musca domestica control
- prevent contamination of food
- Eliminate breeding places
- Residual insecticides
- Biological control
- Health education
2. Sarcophaga (Flesh fly)
Adult
- Medium to large slender grey fly
- Sarcophaga (flesh fly) is commonly found in meat stalls
- Has a pair of very large compound eyes
- They have stiff transparent wings
- The thorax has 3 longitudinal lines
- Abdomen has chess board appearance
- Adults lay larvae not eggs (larviparous)
Larvae
- Larvae are similar to other fly species maggots in the
appearance
- Larvae has anterior and posterior spiracles
- The spiracles are located in a deep pit and in the cross
section it has the appearance of 3 slits covering on a button.
3. Chrysomia (blue bottle fly)
- Found in Asia and Africa
- It is a large metallic green or blue greenfly with a bright
green thorax.
- Larvae have anterior and posterior spiracles
Chrysomia (blue bottle fly)
Medical importance
- helps in deciding the time of death for forensic
pathologists.
- The adult fly lay eggs when the host is alive and hence
depending in the stage of life cycle found on the dead body,
the time of the death of the host can be decided.
- Forensic pathologists also decide whether the dead body
has been moved from the site of killing.
Myiasis
- Myiasis defined as invasion of mammalian tissue by dipterous larvae.
- The association may from complete endoparasitism to predation on
human body by free living larvae.
- A wide range of larvae belonging to various fly families are
implicated.
- Some of them are specialized endoparasite while others are
scavengers or carrion feeders.
- The larvae may be found in any natural
- orifices (A body orifice is any opening in the body of an animal)
- wounds
- in the gastrointestinal tract
- tissues in the body
Classification
- Clinical classification (depending on the tissue
they invade
- Parasitological classification (type of host
parasitic relationship)