Cochliomyia hominivorax

1. Cochliomyiahominivorax Heather Peters Amy Liberio

2. 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 Cochliomyiamacellaria, aka. Secondary screwworm

3. Comparison Secondary screwworm Feeds on dead tissue only New World screwworm Feeds on both dead and living tissue

4. Geography • Located throughout the Neotropical region • Normal range: Mexico to northern Chile and Argentina • Has been seen as far north as Minnesota and Montana

5. Hosts • Definitive hosts: humans, cattle, horses, goats, cats, dogs, along with many other warm-blooded animals • No intermediate hosts

6. Life Stages • Egg • Larva • Pupa • Adult • Entire life cycle takes place in an average of 20-21 days

7. Life Cycle

8. 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

9. 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

10. 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

11. Pathogenesis • Nasopharangealmyiasis • 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

12. 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

13. 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

14. 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

15. 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

16. Economic Importance • Before eradication of Cochliomyiahominivorax 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

17. Monsters Inside Me • http://health.discovery.com/videos/monsters-inside-me-screwworms.html

18. Review • What geographic regions are home to Cochliomyiahominivorax? • What is myiasis? • How is this parasite controlled? • What are the different life stages of this parasite?