Presentation on theme: "Cochliomyia hominivorax Screwworm MAN eater Allaa` Hassan."— Presentation transcript:
Cochliomyia hominivorax Screwworm MAN eater Allaa` Hassan
Parasitic fly Known for the way its larvae(maggots) eat the living tissue of warm blooded animals.
Causes Myiasis: damage of animal tissues (by larva) Infestation causes serious loss of livestock production
Geography “New world” tropics and Neoartic regions of western hemisphere Eradicated in the United States, (except Southern Texas) Mexico, Guatemala, Belize, El Salvador, Honduras., and Libya. Throughout Africa, ME, India, and SE Asia. Central and South Americas.
Definitive Host All warm blooded animals Including livestock, wildlife, pets, zoo animals, & even humans! Cattle, sheep, and goats Experience the greatest economic losses No intermediate host
Morphology Adults Dark, shiny, bluish green 10mm long Reddish yellow face & 3 black stripes on upper thorax between the wings. Larva 17mm resembles the spiraled “screw” – shape their common name is based on cranial end of the larvae has two sharply-curved hooks, – generally dark in color caudal end: distinctive spiracle patterns distinctly pigmented tracheal trunks
Life cycle ~20 days Females lay 250-500 eggs on edge of exposed flesh of an animal. Eggs are in a tight row that overlap on the edge of the wound, resembling shingled roof. Egg mass is characteristically white and compact. After 12-21 hours, larva hatches, crawls into wound, and burrow into surrounding tissue as they feed first stage They get their name “screwworms” because if the wound is disturbed during their burrow and feeding time, they burrow or “screw” deeper into the flesh. Larva feeds on wound fluids and live tissue
Life cycle contd Within 24 hours of hatching: – larvae penetrate wound and molt into second stage. 42-45 hours after hatching: – larvae enter third and final stage ~7 days after hatching: – the grown larva exit from the wound and fall to the ground They burrow in the soil and pupate (7-10 days) depending on the temperature – Form hard sclerotised pupal case – Freezing /sustained soil temperatures <46 F kills the pupa After they pupate, the adult stage develops Females mate 4-5 days after hatching Females can lay up to 3,000 eggs and fly up to 125 miles during her life time.
Clinical signs May be readily missed – Even with close examination With suitable environment and host circumstances; – Infestations can be dramatic and devastating Enlarging the wound makes the host vulnerable to bacterial infections – Screwworm fly is an obligate wound parasite and requires soft tissue of living warm-blooded animal to develop its larva. – Related to the site and severity of infestation – Severe infestation will cause systematic disease – Light infestation may go unnoticed – They infest umbilical regions of newborn animals. – Infestations are associated with traumatic injury, erosive or ulcerative lesions of the skin, or hemorrhage – In sheep Strikes the inner corner of the ye and perineal region of ewes without obvious trauma
Signs of infestation Foul –smelling lesion containing larval screwworm flies Frequent licking of the lesion by an animal Restlessness of affected animal Fever Lethargy Loss of appetite Debilitation Decreased growth rate Anemia Hypoproteinanemia Peritonitis following navel infestation Sinusitis following dehorning Pleuritits following thoracic infestation Restricted movement following muscle infestation Tissue irritation Procedures like: dehorning castration branding tail docking ear tagging can lead to infestation.
Screwworm maggots have toxic saliva which promotes infection of wounds and thus the cause of foul smelling pus The pus is what attracts more screwworm flies and other species of flies. – If tissue is necrotic, it attracts even MORE flies! – This increased level of infestation becomes greatly enlarged unless treated. If untreated, results in death of animal.
Prevention Early detection Public awareness Widespread targeted surveillance – Concentrate on areas at higher risk Like: ports of entry for returning livestock vessels Traps – Sticky boards Regularly inspect animals for wounds
Treatment Chemical pesticide to treat infestations and to protect animals from a strike by the screwworm flies. Myiasis(humans and animals) – Clean the wound and surroundings with warm water – Remove (using forceps) as many larva as possible – Collect and destroy removed larva using hot water or insecticide – (may or may not retain larva for identification) – Apply topical treatment to the wound to kill any remaining larva – Treat animal with longer acting systemic insecticide for prophylaxis – For animal: Invermectin is administered by subcutaneous injection and is the only active constituent of any product with claim against Old World SWF. Provides protection against new infestations in cattle for 16-20 days. – No vaccine
Human infestations Rare but very common in endemic areas. Causes Myiasis that usually occurs on the neck or scalp. Serious complications including death – Resulted from infestation of the nose, eyes, ears, and mouth. Tissue inflammation
Control & Eradication (SIT) – Sterile Insect Technique – U.S officially eradicated the Screwworm in 1982. – Method of biological control – Mass number of sterile males are released. – Why males? – Overwhelming number of sterile males and they compete with the wild males for female kissy time. – What happens when a female mates with a sterile male? Keep in mind that the screwworm fly only mates once during her life time while the men are a bit more…promiscuous.
Why is this technique so successful if the female can only mate once during her life time? This is quiet possibly the most ingenious technique because it reduces the next generation’s population. When it’s repeated, you can eventually have a strong control or fully eradicate a species in a location.
Problems with technique Species specific. If you eradicate one species that is in a genus that contains 25 species, you must do every single species separately. Cost involved in producing large number of sterile insects, especially in poorer countries
Why get rid of it? NUISANCE! These “man-eaters” prey on warm blooded animals, especially cattle and are capable of killing a full grown cattle within 10 days of infection. In the 1950’s, screwworms caused lots of loss to American meat and dairy supplies that were projected at above $200 million!