The New World screwworm (NWS) (Cochliomyia hominivorax) is an obligate parasite that requires a living host for larval development (1). NWS is endemic in countries in the Caribbean region and in South America, and cases have spread north to Central America (https://www.aphis.usda.gov/livestock-poultry-disease/cattle/ticks/screwworm). Thus, risk for re-introduction of NWS from South America to NWS-free areas in Central and North America is constant (2). Because of its substantial effects on livestock, wildlife, and human health, NWS infection is reportable in Colombia (1,3). However, reports of this parasite affecting the mountain tapir (Tapirus pinchaque), an endangered species on the International Union for Conservation of Nature Red List (https://www.iucnredlist.org), have only been anecdotal. Here, we describe 2 cases of myiasis caused by NWS infestation in mountain tapirs in a protected area of the Central Andes of Colombia.

Figure 1

Figure 1. Myiasis in cases of New World screwworm infestation in wild mountain tapirs, Central Andes Mountains, Colombia. Myiasis and active larvae can be seen in large, 8–10-cm wounds on left side...

We collected NWS larvae from 2 adult mountain tapirs, 1 female on October 19, 2024, and 1 male on January 28, 2025, in Ucumari Regional Natural Park (4°42′14″N, 75°32′14″W) at an altitude of 2,097 meters. Both tapirs had deep, 8–10-cm long wounds with exposed muscles in their hindquarters, consistent with myiasis caused by NWS larvae feeding on living tissues (Figure 1). Neither tapir received prior treatment or was subsequently monitored, making determination of the cause or progression of their injuries impossible. To collect larvae, the local environmental authority, Corporación Autónoma Regional de Risaralda, chemically restrained the female tapir, but the male tapir exhibited docile behavior in its interactions with the local community and did not require restraint.

Figure 2

Figure 2. Cochlyiomia hominivoraxlarvae collected from a case of New World screwworm infestation in wild mountain tapir, Central Andes Mountains, Colombia. The larvae were collected from a male tapir and depict...

We collected 2 larvae directly from the female tapir’s wound with tweezers and placed larvae in a box until they pupated; after 12 days, they emerged as adult flies (both male) (Appendix Figure 1), which we photographed then stored in 96% ethyl alcohol. We collected 20 larvae from the male tapir and stored larvae in 70% ethyl alcohol. We also photographed phenotypic traits of maggots from the male tapir to enable taxonomic identification and confirm NWS (Figure 2) (4).

Our assessment of wild mammals in the area that have potential to host NWS indicated that other threatened species are also at risk, including the clouded tiger-cat (Leopardus pardinoides), little red brocket (Mazama rufina), northern pudu (Pudela mephistophiles), Andean bear (Tremarctos ornatus), mountain coati (Nasuella olivacea), and Andean squirrel (Leptosciurus pucheranii) (Appendix Figure 2). NWS infestations have been documented in several threatened neotropical mammals in the Caribbean and the Americas, including the giant armadillo (Prionodon maximus), maned wolf (Chrysoscyon brachyurus), jaguar (Panthera onca), giant anteater (Myrmecophaga tridactyla), lowland tapir (Tapirus terrestris), and giant otter (Pteronura brasiliensis) (Appendix Table). Humans and domestic animals are also at risk for NWS infestation.

Although often overlooked, myiasis has been linked to severe population declines in wild ungulates, raising conservation concerns for species with low reproductive rates and population sizes, such as mountain tapirs (5). For instance, in October 2016, NWS myiasis led to the loss of 14% of the total Key deer (Odocoileus virginianus clavium) population in Florida in the United States (2). In addition, myiasis resulted in mortality rates of white-tailed deer fawns (O. v. texanus) that ranged from 25% to 80% across different regions of the United States (6). The proximity of livestock has been associated with NWS outbreaks, and climate change could contribute to expansion of NWS into new areas (7).

Factors associated with the emergence of NWS in mountain tapirs remain unclear. Although livestock production in the local area is minimal, contact between livestock and tapirs might exist. Free-ranging dogs, known carriers of NWS (3), also have been documented negatively interacting with mountain tapirs (5). In addition, intraspecific aggression among tapirs and prolonged use of radio collars also can cause wounds promoting myiasis development, as observed in collared peccaries (Pecari tajacu) (8) and lowland tapirs (9). The parasite also affects humans, and a case of umbilical myiasis was reported in a 7-day-old infant in La Virginia, Risaralda, Colombia, in 2020 (10).

To mitigate the threat from NWS, Colombia should consider implementing a biological control program using the sterile insect technique, similar to eradication efforts in North and Central America (1). Implementing such a program in Colombia would require studies to assess technical, political (intergovernmental cooperation), economic (cost-sharing), and environmental feasibility. Integrated control measures at smaller scales could help reduce NWS populations to nonthreatening levels (1). Threat mitigation strategies should include medical care for infested wildlife and community outreach to raise awareness about the effects of the parasite on humans, domestic animals, and wildlife.

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