Cochliomyia hominivorax

Karla Bennett May 2012

Taxonomy

Kingdom: Animalia Phylum: Arthropoda Class: Insecta Order: Diptera Family: Calliphoridae Genus: Cochliomyia Species: Cochliomyia hominivorax

Brief Information

It is called the “New World Screw-Worm Fly” It is a parasitic fly whose larvae (maggots)

feed on living tissue of warm-blooded animals. (Yes, it is a man-eating fly).

The infestation of a live vertebrate is called “myiasis”

There are 5 species of Cochliomyia but only 1 species of screw worm fly.

They are unusual because they prefer healthy tissues and not putrid tissues.

MMM! FLESH!

Distribution Range: Central and southern U.S. through mexico, Central

America, Carribean Islands, and Northern South America. U.S. and Mexico are using “sterile insect techniques”.

Now the disease border is between Mexico, Guatemala, and Belize.

The red color on the map shows the New World distribution.

Life Cycle

Life cycle overview

Definitive Host= Humans or any warm-blooded animal Intermediate Host= None Fly lays its eggs in a wound 24 hours later larvae emerge and feed and burrow

their heads into the tissue. Odor of wound attracts adult female to lay more eggs

(3000 larvae/wound 5-7 days larvae mature and drop to the ground,

burrow, and become “pupates”. Adults (8-10mm) emerge in the morning in 1-3 days. They mate within 1-3 days. Females then seek out a host to lay her eggs on (laid

in a shingle-like batch).

Symptoms

Motion inside a wound A wound becoming worse Serosanguineous discharge and odor from

the wound. Larvae can be seen in the wound after 3

days (vertical orientation in the wound) They burrow deeper if disturbed Animals with it (specifically grazing animals)

will lie down in the shade and show decrease in appetite and if milk producing will have decreased production.

Diagnosis

Identification of parasite under the microscope (can see distinctive larvae and eggs are laid in a particular pattern)

Cuticular hydrocarbon analysis Analysis of mitochondrial DNA and random amplified

DNA polymerase chain reaction (RAPD-PCR) assays. Larvae resemble a wood screw with a pointed head

and blunt back end. They have brown spines that encircle the body.

Eggs are laid in a shingle-like array near the edge of the wound.

Treatment

Wounds can be surgically excised The best treatment is the use of

larvacide. The treatment is repeated until the wound heals

Larvae must be destroyed otherwise they can leave and become adults.

Control

Reduced and then eradicated by repeatedly releasing sterilized male flies so that the flies mate and only produce unfertilized eggs.

Mini Quiz!

What phylum? What is the common name of the parasitic fly? Who is the intermediate host? How did the U.S. eradicate this fly? What stage is the fly in when it burrows into

the ground? Why shouldn’t you itch the wound being

affected by the larvae? Why are these flies so unusual as compared

with other flies? (hint: has to do with where they lay their eggs).

Citations

http://www.fao.org/ag/aga/agap/frg/feedback/war/u4220b/u4220b07.htm#geographical%20distribution%20of%20new%20and%20old%20world%20screwworm%20flies

www.cfsph.iastate.edu/Factsheets/pdfs/screwworm_myiasis.pdf

Wikipedia (for picture only) http://en.wikipedia.org/wiki/Cochliomyia

http://www.naiaonline.org/guest_editorials_and_commentary/page/suffering-to-end-suffering-the-heroic-effort-to-eradicate-the-north-america

http://www.kmle.co.kr/search.php?Search=Cochliomyia+hominivorax&SpecialSearch=HTMLWebHtdig&Page=3

http://www.sciencephoto.com/media/146978/enlarge

http://www.impactlab.net/2008/05/08/frightening-new-face-of-evil-the-screw-worm/