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 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.

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 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.