Screwworm infestation is caused by fly larvae that feed on living flesh of mammals and sometimes birds. The larvae are laid by screwworm flies near wounds and proceed to burrow and feed on tissue, creating large lesions. The flies prefer warm humid environments and have a life cycle that can be completed in under 20 weeks. Signs of infestation include wounds with visible maggots, licking, fever, and infected areas around common sites like heads, briskets, and navels. Diagnosis involves identifying the larvae in wounds. Treatment requires removing the larvae and cleaning the wound repeatedly with antiseptic solutions until it heals. Prevention strategies include wound cleaning and use of insecticide sprays and powders

2. Screwworm
 Screwworm infestation is a disease where fly larvae (maggots) feed on living flesh. They infest
all mammals and rarely birds.
 In the New World Screwworm is known as (Cochliomyia hominivorax) and in the old world it is
known as Chrysomya bezziana. But the disease is called Myiasis.

3. Screwworm
 Causative Agent: Caused by the larvae of Cochliomyia hominivorax the common name
for this fly is blow fly.
 Aetiological Agent: Cochliomyia hominivorax, Is found in the Western Hemisphere,
primarily in tropical areas of South America and Caribbean Islands.

4. Pathogenesis / life cycle
 Life cycle
The screwworm fly life cycle includes the eggs, larvae, pupae and adults. The life cycle can be
completed in less than 20 days under ideal environmental conditions.
 Eggs
100–200 are laid in rafts beside wounds.
 Larvae (maggots)
Hatch about 12 hours after laid.
Enter living tissue around wounds.
Create cavernous, foul smelling lesions up to 10–12cm in diameter.
Feed on host tissue until mature—about 5–7 days.
When mature they leave the wound and fall to the ground.

5. Continue...
 Pupate
Pupate for 2–60 days before the flies emerge.
Do not survive temperatures below freezing.
 Adult
Free flying.
Prefer warm humid environments.
Optimum temperature range is 20–30ºC.

6. Picture depicting screwworm lifecycle

7. Clinical Signs
 Signs of infestation of maggots in animals include:
 visible maggots in wounds
 constant licking of the wound
 restlessness
 fever
 lethargy
 infected, smelly and bleeding wounds, sometimes with pus and maggots emerging
 hard and swollen navels
 Common areas for screwworm strike include the:
 head and surrounding area
 brisket
 genital area
 navel.

8. Diagnosis
 In order to diagnosis screwworm infestation properly one must look first for the signs:
 Screwworm often exists in wounds that already exists, such as castration, dehorning, branding,
shearing, wire cuts, sore mouth in sheep, and shedding of the velvet in deer. Navels of newborn
mammals.
 Bloody discharge from the infested wounds
 Malodor
 Discomfort
 Decreased feed intake
 Decreased milk production
 The diagnosis of screwworm is based on the identification of the agent which is difficult
especially as non screwworm species may be present. Larvae and adult flies should be sent to
specialist entomologists for identification.

9. Treatment/ Correction
 Remove the larva from the wound with a
tweezer then flush the area with dilute
iodine solution. Then you would do
wound care twice daily until heal with
gentian violet solution and wound
powder which are topical antibiotics.

10. Prevention/Control:
 Prevention/ Control:
 Washing the area or the environment
where the animal is to reduce order
which may attract blow fly.
 The use of asuntal powder 1% and
sipermetrin can be use to control
screwworm.
$547.77 JMD
Spraying the navel of a calf with ectoline spray.

11. Reference
 Veterinary Division - animal health programs. (n.d.). Retrieved March 26, 2021, from
https://www.ncagr.gov/vet/Factsheets/screwworm.htm
 Disease information. (n.d.). Retrieved March 26, 2021, from
https://www.cfsph.iastate.edu/diseaseinfo/disease/?disease=screwworm-myiasis
 Screwworm flies. (2017, January 20). Retrieved March 26, 2021, from
https://www.iaea.org/topics/sterile-insect-technique/screwworm-
flies#:~:text=The%20larvae%20burrow%20through%20the,increasing%20need%20
for%20agricultural%20production.

12. Walk Good