For decades, screwworm was eliminated in North America, but containment efforts in Panama failed. Now, cattle smugglers are helping the parasite move north.
Recently, the United States Department of Agriculture temporarily suspended imports of cattle from Mexico after a carnivorous parasite have been detected in animals in the south of the country.
Until the recent discovery of fly larvae parasitic in cattle (Cochliomyia hominivorax), at an inspection point in the State of Chiapas, the species had been eliminated in North America at the end of the 19th century.
The border between the United States and Mexico remains closed to cattle and may not reopen before the new year, says .
The parasitic worm is the larva of a metallic blue-green fly which spends the first part of its life cycle devour the living flesh of mammals. Infestations can be fatal.
Cows are the caterpillar’s favorite feast, but the larvae can also feed on other domestic animalsas well as wild and pet animals.
Flies often lay their eggs near open wounds and, if the larvae can find a hole in the skin to place their sharp hooks in their mouths, they bury themselves in the animal’s flesh and devour it.
The discovery in Mexico follows the recent reappearance of the parasite in other South American countries: Costa Rica, Nicaragua, Honduras and Guatemala.
Faced with the reappearance of the parasite, Mexico is intensifying sanitary measures, requiring the treatment of wounds in cattle, larvicidal baths and deworming of cattle.
The Mexican-American Commission for the Eradication of the Screwworm
Specimen of fly of the species Cochliomyia hominivorax
However, conservationists from the Wildlife Conservation Society and Mexican farmers warn that illegal livestock trade will be the true gateway for the disease into North America.
Before the closure of the border with the United States, the National Confederation of Livestock Organizations of Mexico had asked the government to crack down on cattle smuggling across the country’s southern border.
If the parasite re-infests Mexican cattle, the cost of eliminating it will not be high — and the interruption of trade with the US will be highly expensive. In 2023 alone, Mexican exports of live cattle and beef to the US were worth 3 billion dollars.
