Screwworm (Diptera: Calliphoridae) in the United States: Response to and Elimination of the 2016–2017 Outbreak in Florida

Abstract

Eradicating screwworm, Cochliomyia hominivorax (Coquerel), from continental North American via the sterile insect technique has provided huge economic benefit to livestock producers by eliminating screwworm myiasis. After confirmatory identification of fly samples from infested deer by the USDA National Veterinary Services Laboratory on September 30, 2016, an alert was issued that screwworm myiasis was discovered in the Florida Keys. Personnel from USDA Animal and Plant Health Inspection Service, Agricultural Research Service, the State of Florida, U.S. Fish and Wildlife Service and local officials responded to the outbreak focus on Big Pine Key. After witnessing infested Key deer (Odocoileus virginianus clavium Barboyr & Allen), screwworm adult sampling was initiated at 0930 h on October 5, 2016 using nets to collect flies arriving at putrid liver, with the first female collected within 1 h. Larval samples were collected from infested animals for DNA analyses and to develop a "Florida outbreak" colony to test mating compatibility with the mass-produced strain used for sterile fly releases. Ground release chambers for sterile screwworm releases were placed in favorable habitats based on satellite image analyses. Sterile pupae were first placed in the chambers on October 11, 2016. Further liver trapping showed that 13 Keys were infested. One case, presumably through animal movement, occurred near Homestead on the Florida mainland. Ultimately there were 35 sterile fly release stations, including 4 located around Homestead, but no further cases were identified. About 188 million sterile flies were released until successful eradication was declared on March 23, 2017. Containing the outbreak prevented economic losses to livestock producers and other wildlife on the mainland and kept eradication costs to a minimum.

Deconstructing the eradication of new world screwworm in North America: retrospective analysis and climate warming effects

“…Screwworm is endemic to the Caribbean and South America, and periodic cases of myiasis occur in North America (Alexander, ) as exemplified by the severe outbreak of myiasis in deer ( Odocoileus virginianus clavium ) populations in the Florida Keys in 2016. This infestation was eradicated by releasing 188 million sterile flies (USDA‐APHIS, United States Department of Agriculture – Animal and Plant Health Inspection Service, ; Skoda et al ., ). SIT containment of the fly continues in Panama, and the early detection and control of sporadic infestations in North America remains the mainstay of screwworm management.…”

New World screwworm (Cochliomyia hominivorax) myiasis in feral swine of Uruguay: One Health and transboundary disease implications

“…However, the risk for screwworm outbreaks where domestic pigs and feral swine are present must be noted. One pet pig was infested during the 2016 outbreak in Florida [18], and feral swine also thrive in Panama where the screwworm barrier zone exist to prevent the reinvasion of Central and North America through the continental mainland [41].…”

“…In the 1950s, screwworm infestations were reported in feral swine in the state of Florida, U.S.A., and control of the swine populations was considered a priority to be able to reduce the screwworm incidence in the deer herd [6]. The importance of wildlife as a host for screwworm was highlighted during the outbreak in the Florida Keys of the U.S.A. in 2016, which resulted in the death of 135 endangered key deer [18]. Therefore, surveillance for myiasis cases in wildlife species including invasive feral swine could enhance the e ciency of areawide screwworm management programs [19].…”

Rift Valley Fever Virus, Japanese Encephalitis Virus, and African Swine Fever Virus: Three Transboundary, Vector-Borne, Veterinary Biothreats With Diverse Surveillance, and Response Capacity Needs

“…Veterinary surveillance is and will be very important for early detection of invasive vectors and pathogens. As an example, observations of Myiasis in Florida key deer populations in 2016 led to the discovery of an invasion of the screw worm fly, Cochliomyia hominivorax (Coquerel), which had been eradicated from the US since 1959 (55). Re-eradication of this fly was declared in March of 2017, after 35 releases of sterile flies (55).…”

“…As an example, observations of Myiasis in Florida key deer populations in 2016 led to the discovery of an invasion of the screw worm fly, Cochliomyia hominivorax (Coquerel), which had been eradicated from the US since 1959 (55). Re-eradication of this fly was declared in March of 2017, after 35 releases of sterile flies (55). Participants of the RVF Working Group recommended training relevant professionals "to recognize the early signs of an RVF epizootic or epidemic, " and identified a shortage in high containment biosafety laboratories to safely conduct the necessary research (53).…”