Cochliomyia hominivoraxHeather PetersAmy Liberio

Aka. New World Screwworm This species is the most important cause of

myiasis (infection by fly larvae) in the world Adult flies are a deep, greenish-blue metallic

color with a yellow, reddish, or orange face, and 3 stripes on the thorax

Adults are about twice the size of a common house fly (between 20-25mm long)

Adult often confused with Cochliomyia macellaria, aka. Secondary screwworm

Comparison

Secondary screwwormFeeds on dead tissue onlyNew World screwworm

Feeds on both dead and living tissue

Geography Located throughout

the Neotropical region

Normal range: Mexico to northern Chile and Argentina

Has been seen as far north as Minnesota and Montana

Hosts Definitive hosts: humans, cattle, horses,

goats, cats, dogs, along with many other warm-blooded animals

No intermediate hosts

Life Stages Egg Larva Pupa Adult Entire life cycle

takes place in an average of 20-21 days

Life Cycle

Life Cycle Females will lay their eggs (100-350) at the

edge of an open wound, since larvae cannot penetrate intact skin

The larvae will hatch from the eggs and will embed themselves in the host’s tissue and begin to feed on both dead and living tissue

Life Cycle After a few days of gorging themselves, the

larvae will drop off of the host and bury themselves in the soil

They then develop a dry shell around themselves and enter the pupal stage

During this stage they will undergo metamorphosis and become mature adult flies

Once development is complete, the flies will emerge from their pupae and begin to mate

Males will mate many times, whereas females will only mate once

Pathogenesis Cutaneous myiasis Often seen in cattle

and other warm-blooded animals

As higher numbers of cattle become infected, chances of humans becoming infected are greatly increased

Pathogenesis Nasopharangeal myiasis This type of myiasis is more common in humans Eggs will be deposited near nasal opening, and

larvae will migrate into nasal cavities and pharynx

Symptoms Formation of wounds Enlargement of

existing wounds Decaying flesh Wound discharge Secondary bacterial

infections

Pain in infected area Edema Fever Lethargy Loss of appetite

Diagnosis Visualization of

larvae in or around wounds

In cattle, infected individual will often separate self from group, display discomfort and depression

No serologic tests available

Treatment Killing and manual

removal of larvae from infected site

Treatment of cutaneous wounds with approved pesticide (Spinosad-aerosol)

Administration of antibiotics to treat secondary bacterial infections

Control Sterile Insect Technique (SIT)- a process where adult

males are raised in a lab and sterilized via radiation and are released into the environment Since females only mate once, if they mate with a

sterile male then females will produce sterile eggs and this will break the cycle

Injections of doramectin has been shown to give some protection to cattle against New World Screwworm infections

Detection of wounds on cattle and other animals, and immediate treatment of the wound with an approved insecticide

Wash and keep any wounds clean No vaccine available

Economic Importance Before eradication of

Cochliomyia hominivorax an average of 180,000 livestock deaths occurred yearly in Texas alone

Since eradication in the mid-1950s, the United States saves $900 million yearly that before would have been lost due to this parasite

Monsters Inside Me http://health.discovery.com/videos/mons

ters-inside-me-screwworms.html

Review What geographic regions are home to

Cochliomyia hominivorax?

What is myiasis?

How is this parasite controlled?

What are the different life stages of this parasite?