Flies and MyiasisFlies 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

• 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

• 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

• 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

• 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 SpeciesControl 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.