Screwworms infest warm-blooded animals, including humans, when a female screwworm fly lays eggs on fresh open wounds or mucous membranes. The wounds can be as small as a scratch, insect bite, or surgical cut. The eggs hatch into larvae (maggots) that then burrow into and feed on the living flesh of the host, causing a serious and often painful infestation known as myiasis.
How Screwworms Infest
- Female screwworm flies seek out open wounds or exposed skin on warm-blooded animals to deposit their eggs.
- Eggs are typically laid on or around the dry perimeter of the wound.
- The eggs hatch within 24 hours, and the larvae immediately begin feeding on live flesh.
- Larvae grow for 1 to 2 weeks, causing tissue damage.
- They can infect wounds from minor scratches, insect or tick bites, to larger cuts or surgical wounds, including the umbilicus of newborn animals or animals undergoing procedures like castration or branding.
- The maggots burrow into living tissue and may deepen the wound, making infestations painful and potentially fatal if untreated.
Risk to Humans and Animals
- Screwworms primarily infest livestock but can also infest humans.
- Humans are at risk if they have open wounds and are exposed to screwworm flies, particularly in endemic regions such as parts of South America and the Caribbean.
- Traveling to these regions or contact with livestock in infested areas increases risk.
In summary, screwworms are acquired by warm-blooded animals, including humans, through the laying of eggs by female screwworm flies on open wounds or mucous membranes, leading to maggots feeding on living flesh and causing myiasis.
