1. Flies and Myiasis
Lecture 14

2. Myiasis Defined
The invasion of organs and tissues of humans or other vertebrate animals with dipterous larvae, which for at least a period feed upon the living or dead tissue or, in the case of intestinal myiasis, on the host’s ingested food.

3. Types of Myiasis Accidental or Pseudomyiasis Facultative Obligatory
Insects in the family Muscidae
Larval stage is the problem stage
Enteric, accidental, rectal, and urinary
Facultative
Maggot therapy
Maggots free-living, attack carcasses, may attack living host.
Obligatory
Maggots live on a live host for part of their life.

4. Myiasis Producing Flies
Three Main Families:
(1) Calliphoridae (2) Sarcophagidae
(3) Oestridae
Black Blow Fly
Livestock Myiasis causing flies

5. Calliphoridae: Non-Metallic Flies
Cordylobia anthropophaga

6. Life-Cycle Eggs  Larvae  Pupae  Adult
Females lay eggs. (1-3 days)
Larvae attach to host or washed clothing placed on ground.
1st instar
2nd instar
3rd instar (11-15 mm)
8-12 days larvae wriggle out of boil to ground.
Larvae bury themselves and then pupate
Adults emerge (feed on rotting fruit, carrion, and feces).

7. Medical Importance Traumatic or nasopharyngeal myiasis.
Cause boil-like swellings
Usually 1 or 2 larvae are found in a patient.
Infections prevented by not spreading clothes on the ground.
Dogs and rats are commonly infected.
To Remove:
Cover the small hole with med. Liquid paraffin.
Gently press around the swelling

8. Calliphoridae: Metallic Flies
Cochliomyia hominivorax

10. Life Cycle Eggs  Larvae  Pupae  Adult
eggs on wounds, scabs, sores, etc.
3rd instar is formed in 2-3 days and is maggot-shaped.
Mature larvae wriggle out after 4-12 days, drop to ground.
Pupate in soil
Adults emerge after 7-12 days.

11. Medical Importance
Often results in considerable damage and disfigurement, esp. if face is attacked.
When invade nose, mouth, eyes they can cause severe pain.
Larvae may eat their way through the palate.
Putrid-smelling discharges and ulcerations.
Treatment should be immediate!
Irrigate infested areas with ethanol + Veggie oil
Some forms of myiasis may require surgery.

12. Calliphoridae: Metallic Flies
Lucilia spp.

13. Calliphoridae: Metallic Flies
Calliphora spp.

14. Life Cycle Eggs laid on meat, fish, carrion, occasionally on wounds.
Eggs hatch 8-12 hours.
Larvae are maggot-shaped, period lasts 4-8 days.
Mature larvae bury into soil and pupate.
Puparial period (6-14 days).
Adults emerge and begin feeding and laying eggs.
Similar for both the Green and Bluebottle flies.

15. Medical Importance Facultative myiasis. Dirty habit
Larvae feed mainly on pus, not much damage.
Occasionally intestinal myiasis is reported.
Removal is easy.
Rarely invade healthy tissue.

16. Maggot Therapy Has been used for centuries.
American Civil War ( )
Recently rediscovered and FDA approved for use.
Usually Greenbottle flies are used.

17. Sarcophagidae: Flesh-Flies
Sarcophaga spp.

18. Life Cycle Larvae are scavengers Development is rapid (3-4 days)
Pupate in soil (7-12 days)
Adults emerge and go to carrion to feed.

19. Medical Importance Facultative myiasis
Cause little to no damage as they feed on necrotic tissue.
Accidental intestinal myiasis.
Most enteric myiasis are Sarcophagidae or Muscidae.

20. Oestridae: Bot Flies Dermatobia hominis
Occurs primarily in lowland forests

22. Dermatobia hominis larva

23. Dermatobia hominis larva

24. Life Cycle 1st instar (4-11 days) Drop into host skin
2nd instar- bottle w/neck (pear).
3rd instar – oval w/spines.
Pupate in soil
Adults emerge (4-11 wks)

25. Medical Importance
Invade subcutaneous tissues in various parts of body.
Produce boil-like swellings.
Lots of discomfort and pain.
See in U.S as people bring back from other countries.
Difficult to remove by squeezing out.
Surgery may be required.
Place meat or medicinal liquid paraffin.

26. Control of Myiasis Species
Control or eradication of the fly population - through environmental sanitation or chemical control.
Avoidance of infestation- do not sleep outdoors or on the ground during fly activity, dress or cover wounds to avoid fly strikes, use screening
Treatment of infestation (remove larvae - antibiotic follow-up)

27. Other Myiasis Causing Flies
Black Blow Fly
Breeds mainly on carrion
Several species of flies cause myiasis in livestock.
Occasionally humans become infected.
Several species of flies cause myiasis in wildlife.

29. Caribou throat with two nose bots.