Flies and Myiasis
Lecture 14
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.
Types of Myiasis
• Accidental or Pseudomyiasis
– 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.
Myiasis Producing Flies
• Three Main Families:
– (1) Calliphoridae (2) Sarcophagidae
– (3) Oestridae
• Black Blow Fly
• Livestock Myiasis causing flies
Calliphoridae: Non-Metallic Flies
• Cordylobia anthropophaga
Life-Cycle
• Eggs  Larvae  Pupae  Adult
• Females lay 100-300 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).
Medical Importance
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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
Calliphoridae: Metallic Flies
• Cochliomyia hominivorax
Life Cycle
• Eggs  Larvae  Pupae  Adult
• 10-400 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.
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.
Calliphoridae: Metallic Flies
• Lucilia
spp.
Calliphoridae: Metallic Flies
• Calliphora
spp.
Life Cycle
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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.
Medical Importance
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Facultative myiasis.
Dirty habit
Larvae feed mainly on pus, not much damage.
Occasionally intestinal myiasis is reported.
Removal is easy.
Rarely invade healthy tissue.
Maggot Therapy
• Has been used for centuries.
• American Civil War (1861-65)
• Recently rediscovered and
FDA approved for use.
• Usually Greenbottle flies are
used.
Sarcophagidae: Flesh-Flies
• Sarcophaga spp.
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.
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.
Oestridae: Bot Flies
• Dermatobia hominis
• Occurs primarily in lowland forests
Dermatobia hominis larva
Dermatobia hominis larva
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)
Medical Importance
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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.
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)
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.
Caribou throat with two
nose bots.