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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.
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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 • 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
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.
