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



Feral swine (Sus scrofa) are highly invasive and threaten animal and human health in the Americas. The screwworm (Cochliomyia hominivorax) is listed by the World Organization for Animal Health as a notifiable infestation because myiasis cases affect livestock, wildlife, and humans in endemic areas, and outbreaks can have major socioeconomic consequences in regions where the screwworm has been eradicated. However, a knowledge gap exists on screwworm infestation of feral swine in South America, where the screwworm is endemic. Here, we report screwworm infestation of feral swine harvested in Artigas Department (Uruguay), where the Republic of Uruguay shares borders with Brazil and Argentina.


Myiasis caused by the larvae of screwworm were identified in feral swine with the support and collaboration of members of a local feral swine hunting club over a 3-year period in the Department of Artigas. Harvested feral swine were examined for the presence of lesions where maggots causing the myiasis could be sampled and processed for taxonomic identification. The sites of myiasis on the body of infested feral swine and geospatial data for each case were recorded. The sex and relative size of each feral swine were also recorded. Temperature and precipitation profiles for the region were obtained from public sources.


Myiases caused by screwworms were recorded in 27 of 618 the feral swine harvested. Cases detected in males weighing > 40 kg were associated with wounds that, due to their location, were likely caused by aggressive dominance behavior between adult males. The overall prevalence of screwworm infestation in the harvested feral swine was associated with ambient temperature, but not precipitation. Case numbers peaked in the warmer spring and summer months.


This is the first report on myiasis in feral swine caused by screwworm in South America. In contrast to myiasis in cattle, which can reach deep into host tissues, screwworms in feral swine tended to cause superficial infestation. The presence of feral swine in screwworm endemic areas represents a challenge to screwworm management in those areas. Screwworm populations maintained by feral swine may contribute to human cases in rural areas of Uruguay, which highlights the importance of the One Health approach to the study of this invasive host species–ectoparasite interaction.

Graphical Abstract


Interactions between invasive wildlife species and high-consequence zoonotic parasites or vectors can have One Health and transboundary disease implications. Multiplier effects from these interactions can exacerbate the risks to the health of human and domestic and wild animal populations, as well as the environment [1, 2]. One such interaction that has not been explored is that between feral swine (Sus scrofa) and screwworm (Cochliomyia hominivorax). Feral swine are highly invasive and threaten animal and human public health because they host parasites and vectors of zoonotic importance in the Americas [3]. Screwworm is listed by the World Organization for Animal Health as a notifiable infestation because myiasis cases affect livestock and other domestic animal species, wildlife, and humans in endemic areas [4]. Screwworm outbreaks can be of high socioeconomic consequence in regions of the Americas where this ectoparasite of warm-blooded animals has been eradicated [5, 6]. Although feral swine were known to be infested before the screwworm was eradicated from North and Central America [7], a knowledge gap exists for this invasive species in South America regarding cases of myiasis caused by screwworm.

Screwworms were originally described infesting humans in 1858 [8]. Today this parasite remains endemic in South America, where they cause myiasis, which is regarded as a neglected zoonosis. Screwworm affects domestic animals and wildlife and inflict significant loss to livestock producers [9, 10]. Similar conditions in the past triggered research in the USA that translated into the development the sterile insect technique (SIT), which was applied areawide to eventually eliminate screwworms from North and Central America, and Puerto Rico [11]. Biotechnology-based SIT approaches are under development for sustainable operations in the screwworm barrier zone maintained on the border between Panama and Colombia through bilateral collaboration between the governments of Panama and the USA [12, 13]. Screwworm control efforts related to animal health and production in countries of South America include monitoring and treatment of myiasis cases using insecticides when livestock are susceptible to infestation, such as in newborn navels, castrations, and other practices related to herd management and traceability [14]. In temperate regions of South America, additional protection from infestation can be achieved by planning livestock births, branding, castrations, or sheering to occur in months with lower screwworm abundance [15]. Surveillance in livestock is a key component of screwworm control, but monitoring and reporting of myiasis cases in wildlife is seldom practiced.

Wildlife involvement in endemic areas maintains screwworm populations that also affect humans and livestock. Prior to eradication the USA, it was estimated that up to 2–3% of wild animals could be infested with screwworms in endemic regions [16]. White-tailed deer (Odocoileus virginianus) die-offs in parts of the USA were associated with myiasis before screwworm eradication [17, 18]. It has also been argued that the disappearance of the screwworm as a natural wildlife population control is part of the reason why white-tailed deer populations have increased markedly in those parts of the USA [17]. In the 1950s, screwworm infestations were reported in feral swine in the state of Florida (USA), and control of the swine populations was considered a priority at that time as a means to reduce the screwworm incidence in deer herds [7]. The importance of wildlife as a host for screwworm was highlighted during the outbreak in the Florida Keys (USA) in 2016, which resulted in the death of 135 endangered Key deer (Odocoileus virginianus clavium) [6]. Therefore, surveillance for myiasis cases in wildlife species, including invasive feral swine, could enhance the efficiency of areawide screwworm management programs [19].

In 1982, feral swine were officially declared a national pest in Uruguay after they were introduced to the country at the beginning of the last century for hunting purposes [20]. Females are capable of producing up to two litters of four to five piglets each year that can reach sexual maturity in less than 1 year, a reproductive output fourfold greater than white-tailed deer [21]. As is the case in other parts of their invaded range, in Uruguay, feral swine also cause extensive damage to agriculture, critical infrastructure, and private property, as well as being a public safety hazard [22, 23]. Organized hunting in Uruguay helps control feral swine and under the proper sanitary conditions provides economic opportunities to hunters and farmers. Research on the causes of myiasis in feral swine was listed as part of the activities needed to inform plans to develop a screwworm control program in Uruguay [24].

This study is the result of a public–private partnership involving an interdisciplinary project on feral swine led by the Colleges of Sciences and Veterinary Medicine of the University of the Republic of Uruguay, in collaboration with the National Association of Hunters in Uruguay, and other regional feral swine hunting and control associations referred to as ProJAB (its acronym in Spanish). In particular, myiasis cases in feral swine reported by members of the Association for the Control of Feral Swine (ACJA) in the Province of Artigas (Uruguay) provided the opportunity to investigate if screwworms were involved. The support and involvement of hunters and associated groups proved to be invaluable to obtain data on screwworm cases in feral swine of Uruguay and stresses the high impact that citizen science can have on pest management programs [25, 26].


Feral swine were harvested over a 3-year period (May 2017 to April 2020) by members of the ACJA in the Artigas and northern Salto departments of Uruguay (Fig. 1; total sampling data is available in Additional file 1: Dataset S1). Artigas department is located in the northern-most portion of Uruguay. The western portion of the department is alluvial plain, while the central and eastern parts are hill ranges. The climate is sub-tropical with an average monthly temperature of 19 °C and an average total annual rainfall of 1400 mm. The primary economic activity is raising sheep and cattle.

Fig. 1
figure 1

Map of Uruguay (left) with the sampling area in the departments of Artigas and Salto along the Brazilian border expanded (right). Locations of feral swine (Sus scrofa) capture are shown (see legend), with sites marked as swine having or not having myiasis. Darker X‘s indicate multiple swine sampled at that site. Sites with more than one myiasis case have the total number of cases given in the circle. Sex ratio is shown as a pie chart

The hunters used several methods to harvest the feral swine, including dogs, firearms, and cage traps. Upon capture, the feral swine were euthanized, geo-referenced, and inspected to assess the general state of health and the presence of parasites (ticks, lice, dipteran larvae) as part of a comprehensive study to assess zoonosis. Size and sex were recorded for all animals, with size being categorized as < 20, 20–40 or > 40 kg (large). Harvested feral swine were inspected visually to identify wounds, which were then checked for myiasis. Upon the detection of myiasis, the site of larval infestation, larval instar, and probable cause of wound were also recorded. Probable cause of the wound was based on the location and shape of the wound and determined by the hunters who have extensive experience hunting feral swine. All larvae present were collected with a stainless tweezer and stored in 70% ethanol for transport to the laboratory where they were identified to species using a stereoscope (4× and 10× magnification). Identification of C. hominivorax larvae was based on tracheole color, spine structure and distribution, and oral hooks [27] (Fig. 2a).

Fig. 2
figure 2

Images of representative screwworm larvae samples (a, top row), myiasis of a feral swine (b), male shoulder shield that had the tusks of another male broken off and embedded (c), and shoulder shield from a large male split to show the thickness (approximately 5–6 cm) (d)

The map of hunted feral swine and myiases cases was created using the ArcGIS online application. Monthly average temperature and total precipitation data was obtained from the Artigas department meteorological station ( and accessed through Weather Underground (; this information is provided in Additional file 2: Dataset 2. Statistical analysis was conducted in the R statistical environment (v3.5.1; [28]). The Fisher’s exact test was used to test for nonrandom associations between sex and size with myiasis. Linear regressions were used to determine correlations between myiases and temperature and precipitation. Differences in hunting pressure by month was conducted using analysis of variance.


A total of 618 feral swine were examined during the study period, of which 27 were infested with dipteran larvae (Fig. 1; Table 1). Animal size, sex, location of capture, and area of body infested for the 27 feral swine with myiasis is reported in Additional file 3: Dataset 3. Microscopic examination of the larvae revealed all cases of myiasis were due to infestation by C. hominivorax. The number of infested males was significantly greater than expected by random chance (P = 0.003), with 20 of 282 males with screwworm infestation compared to seven of 336 females. In addition, the number of large adults with screwworm infestation was greater than expected (P < 0.001), with 26 of 332 large adults having screwworm infestation compared to only one of 286 small/medium swine. These data suggest that there is a greater prevalence of screwworm infestation in large adults, especially large adult males.

Table 1 Size, sex, and number of feral swine (Sus scrofa) examined in the study

Myiasis was found in 12 areas broadly distributed across the body of the swine (Table 2). Despite these infestations, the feral swine showed no signs of severe morbidity due to the myiasis and were otherwise healthy. In some cases, the site of myiasis was covered in mud to a greater extent than the rest of the body, suggesting the possibility that their wallowing behavior could provide some protection by limiting the severity of infestation.

Table 2 Locations of myiasis on the feral swine body

The hunters participating in this study proposed sources of wounds resulting in myiasis (Table 3). Across all sampled swine, it was concluded that most of the wounds detected were the result of intraspecies aggression (15/27), primarily between males (13/0). The second leading cause of myiasis was non-lethal bullet wounds (5/27). The only juvenile pig collected with myiasis had the infection in the umbilical region.

Table 3 Suspected sources of wounds resulting in myiasis

The average percentage of feral swine harvested with myiases reported is shown in Fig. 3. The number of harvested feral swine was consistent between months (F(11,25) = 1.48, P = 0.20), with an average (± standard deviation) of 16.73 ± 8.81 feral swine harvested per month. The number of myiases reported were not correlated to the number of harvested feral swine (R2 = 0.090, P = 0.179), indicating sampling depth was able to record accurate myiasis rates. Cases of myiasis were highest in the spring months September to December (6.71% feral swine with myiasis), and lowest in the winter months July and August (1.09% feral swine with myiasis). The highest percentage of myiasis cases were reported in December (12.9%) and the lowest in June (no cases). Total monthly myiasis cases were correlated to monthly average temperature, with the number of cases increasing with increasing average monthly high (R2 = 0.438, P < 0.001) and low (R2 = 0.102, P = 0.031) temperatures. Total monthly precipitation did not correlate to the presence of myiases (R2 = 0.004, P = 0.289).

Fig. 3
figure 3

Average rate of myiases in harvested feral swine presented as bars with scale on the left vertical axis. Average monthly high and low temperatures and average total precipitation during the study period are presented on the right vertical axis


To the authors’ knowledge, this is the first epidemiological report of screwworm myiasis in feral swine from South America. The myiasis cases in feral swine were reported by hunters in the Artigas and Salto provinces of Uruguay between April 2017 and April 2020. Of the 618 swine examined, 27 were infested with maggots. The screwworm infestation prevalence (4.36%) recorded in the feral swine captured in this study is relatively higher than the estimated 2–3% in wildlife reported by Lindquist in 1937 in Texas [16], and lower than the > 5% recorded in domestic pigs in 1987 in Yucatan, Mexico [29]. The prevalence reported here is similar to that reported previously in sheep (5.7%) and cattle (3.4%) in Uruguay [24].

Screwworm cases were detected primarily in large male feral swine, and primarily in wounds that the hunters suspected as being the result of fighting between males. Dominance behavior in swine includes the males lining up facing each other and pushing at the shoulders, which can leave large lacerations due to their tusks, and biting the neck, ears, and face (Fig. 2b) [30]. These opportunities to lay eggs were exploited by screwworm female flies because 41% of the myiases occurred in those body parts of the host. Wound infestation in males associated with lesions resulting from feral swine fighting was also reported to be common in this wild host before screwworm eradication in Florida was accomplished [7].

Genital myiases in post-birthing females and in juvenile navels are very common in livestock and a primary concern to ranchers [31, 32]. Of the feral swine harvested in this study, only one female with genital myiasis and one juvenile male with navel myiasis were observed. It is possible that in feral swine these are not common sources of myiases, or that these were not commonly observed because they lead to mortality. Navel myiases may have also been underreported, as more adult animals were harvested.

Hunters who participated in this study reported that although myiases are common in feral swine, they did not observe myiases causing serious morbidity or mortality (see Fig. 2b for a typical myiasis in feral swine). Physically, feral swine have thick skin that could inhibit the formation of myiasis and be inhospitable to screwworm larvae. Additionally, male swine develop thick layers of skin and cartilage near the shoulder, called shields [20], which protect males during fights for dominance and may also inhibit screwworm development (Fig. 2c, d). Feral swine behavior may also prevent or act as a treatment of myiases. Wallowing has many benefits to the animal, including thermal regulation, ultraviolet-light protection, and protection against ectoparasites and biting flies [33]. Screwworm larvae in a myiasis are surrounded by fluid, but they must be exposed to air through their terminal spiracles; thus, coating a myiasis in mud or water could suffocate larvae [34]. Coating a wound in mud could also prevent the release of odors that attract gravid female screwworm flies to a wound and stimulate oviposition. Feral swine also exhibit a rubbing behavior associated with wallowing that could remove unhatched egg masses or larvae close to the surface. They also soak or swim in water, behaviors that have been observed in deer to help clean myiases [16]. Thus, it is possible feral swine also intentionally soak to remove screwworm larvae.

Feral swine that survive infestation could play an important role in the dissemination of screwworm. The home range of a feral swine can be over 400 ha, and their territorial range is not limited by rivers [35]. In fact, some of the hunters taking part in the present study reported that during some of the hunting operations in parts of Artigas Department where the Cuareim river serves as the international boundary, feral swine escaped capture by jumping and swimming to the bank of the river on the Brazilian side of the border. It is probable that screwworm infestations acquired in Uruguay, Argentina, or Brazil could be carried to a bordering country where the larvae would crawl off and pupate. This represents a potential for a transboundary zoonotic disease issue. The results from this study highlight the ability of feral swine to act as host for screwworm populations in areas where both are endemic. If one of these three countries were to begin a control or eradication program, feral swine would be a source for re-infestation.

Cooperation with local hunters through ProJAB enabled screwworm infestation to be assessed in feral swine in this study, stressing how research and extension efforts facilitate collaboration between groups that deal with issues at the livestock–wildlife interface. This public–private partnership also involves the education of hunters on practical aspects of veterinary public health to mitigate risks associated with exposure to zoonoses harbored by feral swine in Uruguay [20]. Hunters were made aware of measures to avoid the dispersal of screwworms and to manage the risk of human and domestic animal exposure to infestation. Hunting feral swine often occurs at night, and the hunters transport the harvested animals to their homes and leave them hanging until morning when they are cleaned and processed. During this time, the third-instar larvae would be able to crawl off and pupate near the homes of the hunters, increasing the presence of screwworm adults in the vicinity of the hunters’ homes. In Uruguay, up to 818 human cases of screwworm myiasis are recorded annually, affecting mainly rural populations [24]. This stresses the need to address the control measures of screwworm myiasis from a One Health perspective, especially since it is a neglected zoonosis in the region [36].

The ecological classification of myiasis describes screwworm as an obligate primary parasite because it is dependent on a living host and is capable of initiating the myiasis [37]. Secondary infestations, whether facultative or accidental, with myiasis-causing species in the families Calliphoridae, Sarcophagidae, and Muscidae are often associated with established screwworm infestations [37, 38]. In myiases with secondary species, the primary screwworm C. hominivorax is found feeding on living tissues, while the secondary species are at the wound periphery consuming necrotic tissues. All of the larvae collected from the myiasis cases in this study were identified as C. hominivorax, with no secondary myiasis-causing species present. The absence of secondary fly larvae in these infested feral swine could be due to the wallowing and swimming behaviors mentioned previously and account for the low reported mortality associated with myiases. If myiases are not persistent and tissues do not become necrotic, the development of secondary infestation could be less likely.

Seasonal changes in temperature were correlated with screwworm prevalence in southern Texas in cattle, sheep, and other livestock prior to eradication [39]. However, the patterns are dependent on local climates and should not be generalized. Screwworm infestation in this study correlated with higher monthly average temperatures, and fewer cases were detected in winter months with low temperatures. An increase in infestations associated with higher temperature is concerning because it has been estimated that current global change trends could result in an increase in temperatures in Uruguay of up to 3 °C by 2100 [40]. Under this scenario for other parts of the Americas [41], the risk for screwworm infestation could extend further into the year, thereby reducing the efficacy of seasonal birthing currently practiced by livestock producers in parts of Uruguay with a more temperate climate to reduce screwworm cases. In our study, total monthly precipitation was not correlated to myiases prevalence, as has been seen in screwworm surveys in tropical countries such as Panama or the Caribbean [42, 43]. However, the risk for screwworm outbreaks where domestic pigs and feral swine are present must be noted. Two pet pigs were infested during the 2016 outbreak in Florida, and feral swine also thrive in Panama where the screwworm barrier zone exists to prevent the reinvasion of Central and North America through the continental mainland [6, 44].


Efforts to manage screwworm populations need to include surveillance of myiasis in feral swine where these two high-consequence pests of zoonotic importance coexist. Feral swine in Uruguay were documented to be a common screwworm host. Additionally, feral swine populations are growing and becoming established in new areas, possibly providing additional suitable hosts for screwworm. Moreover, feral swine appear to be resilient to screwworm infestation, unlike the Key deer in southern Florida. Although precautions are taken to reduce screwworm cases in livestock, the invasive feral swine in Uruguay are common hosts to screwworm and possibly serve as a source of infestation for livestock and humans. This situation and the public–private partnership with hunters in Uruguay that facilitated this research project emphasize the relevance of taking the One Health approach to deal with invasive species and transboundary zoonotic diseases.

Availability of data and materials

All data generated or analyzed during this study are included in this published article and its additional information files.



Asociación de Controladores de Jabalí de Artigas


Proyecto Jabalí


  1. Esteve-Gassent MD, Pérez de León AA, Romero-Salas D, Feria-Arroyo TP, Patino R, Castro-Arellano I, et al. Pathogenic landscape of transboundary zoonotic diseases in the Mexico–US border along the Rio Grande. Front Public Heal. 2014;2:1–23.

    Google Scholar 

  2. Osterhaus ADME, Vanlangendonck C, Barbeschi M, Bruschke CJM, Christensen R, Daszak P, et al. Make science evolve into a One Health approach to improve health and security: a white paper. One Heal Outlook. 2020;2:1–32.

    Article  Google Scholar 

  3. Brown VR, Bowen RA, Bosco-Lauth AM. Zoonotic pathogens from feral swine that pose a significant threat to public health. Transbound Emerg Dis. 2018;65:649–59.

    Article  CAS  Google Scholar 

  4. OIE—World Organization for Animal Health. Screwworm (Old World and New World). OIE Technical Disease Cards. 2013. Accessed 22 July 2020.

  5. Conti L. New World screwworm eradication in south Florida: a One Health success story. One Heal Platf Commun. 2018;3:6.

    Google Scholar 

  6. Skoda SR, Phillips PL, Welch JB. Screwworm (Diptera: Calliphoridae) in the United States: Response to and elimination of the 2016–2017 outbreak in Florida. J Med Entomol. 2018;55:777–86.

    Article  Google Scholar 

  7. Strode DD. The Ocala deer herd. Tallahassee: Florida Game and Fresh Water Fish Commission; 1954.

  8. Coquerel C. Note sur les larves appartenant à une espèce nouvelle de Diptère, (Lucilia hominivorax) developpées dans les sinus frontaux de l’homme à Cayenne. Ann Soc entomol Fr. 1858;3:171–6.

    Google Scholar 

  9. Grisi L, Leite RC, de Martins JRS, de Barros ATM, Andreotti R, Cançado PHD, et al. Reassessment of the potential economic impact of cattle parasites in Brazil. Rev Bras Parasitol Vet. 2014;23:150–6.

    Article  Google Scholar 

  10. Bernhardt V, Finkelmeier F, Verhoff MA, Amendt J. Myiasis in humans—a global case report evaluation and literature analysis. Parasitol Res. 2019;118:389–97.

    Article  Google Scholar 

  11. Vargas-Terán M, Hofmann HC, Tweddle NE. Impact of screwworm eradication programmes using the sterile insect technique. In: Dyck VA, Hendrichs J, Robinson AS, editors. Sterile insect technique. Principles and practice in area-wide integrated pest management. Dordrecht: Springer; 2005. p. 629–50.

    Google Scholar 

  12. Concha C, Palavesam A, Guerrero FD, Sagel A, Li F, Osborne JA, et al. A transgenic male-only strain of the New World screwworm for an improved control program using the sterile insect technique. BMC Biol. 2016;14:1–13.

    Article  CAS  Google Scholar 

  13. Paulo DF, Williamson ME, Arp AP, Li F, Sagel A, Skoda SR, et al. Specific gene disruption in the major livestock pests Cochliomyia hominivorax and Lucilia cuprina using CRISPR/Cas9. Genes Genomes Genet. 2019;9:3045–55.

    CAS  Google Scholar 

  14. Reichard R. Case studies of emergency management of screwworm. Rev Sci Tech. 1999;18:145–63.

    Article  CAS  Google Scholar 

  15. Parish HE. Factors predisposing animals to screwworm infestation in Texas. J Econ Entomol. 1942;35:899–903.

    Article  Google Scholar 

  16. Lindquist AW. Myiasis in wild animals in southwestern Texas. J Econ Entomol. 1937;30:735–40.

    Article  Google Scholar 

  17. Novy JE. Screwworm control and eradication in the southern United States of America. FAO World Animal Review. 1991. Accessed 2020 May 27.

  18. Marburger RG, Thomas JW. A die-off in white-tailed deer of the central mineral region of Texas. J Wildl Manage. 1965;29:706–16.

    Article  Google Scholar 

  19. Miller RS, Sweeney SJ, Slootmaker C, Grear DA, Di Salvo PA, Kiser D, et al. Cross-species transmission potential between wild pigs, livestock, poultry, wildlife, and humans: implications for disease risk management in North America. Sci Rep. 2017;7:1–14.

    Article  CAS  Google Scholar 

  20. Lombardi R, Geymonat G, Berrini R. Jabalí en el Uruguay: Problema, desafío y oportunidad. Montevideo: Forestal Atlántico Sur/Weyerhaeuser Productos; 2015.

    Google Scholar 

  21. Taylor RB, Hellgren EC, Gabor TM, Ilse LM. Reproduction of feral pigs in southern Texas. J Mammal. 1998;79:1325–31.

    Article  Google Scholar 

  22. Campbell TA, Long DB. Feral swine damage and damage management in forested ecosystems. For Ecol Manage. 2009;257:2319–26.

    Article  Google Scholar 

  23. Iglesias D. Los accidentes de tráfico contra jabalíes en España se disparan un 47%. El Mundo. 2019. Accessed 22 July 2020.

  24. Marques L, Fernandez F, Iriarte MV. Estudios epidemiológicos de las miasis cutáneas a Cochliomyia hominivorax en el Uruguay. Ser. Fondo de Promoción de Tecnología Agropecuaria-Instituto Nacional de Investigación Agropecuaria (FPTA-INIA) 82. 2019.

  25. Ryan SF, Adamson NL, Aktipis A, Andersen LK, Austin R, Barnes L, et al. The role of citizen science in addressing grand challenges in food and agriculture research. Proc R Soc B Biol Sci. 2018;285:20181977.

    Article  Google Scholar 

  26. Caley P, Welvaert M, Barry SC. Crowd surveillance: estimating citizen science reporting probabilities for insects of biosecurity concern: implications for plant biosecurity surveillance. J Pest Sci. 2020;93:543–50.

    Article  Google Scholar 

  27. Valledor MS, Petraccia L, Décia L, Cabral P. Diagnosticado y descripcion de las caracteristicas morfologicas de los instar 1, 2 y 3 de Cochliomyia hominivorax en el departamento de Artigas. Jornadas Uruguayas de Buiatría. 2010;38:163–5.

    Google Scholar 

  28. R Core Team. R: A language and environment for statistical computing. Vienna: R Foundation for Statistical Computing; 2016.

  29. Thomas DB. Incidence of screwworm (Diptera: Calliphoridae) and torsalo (Diptera: Cuterebridae) myiasis on the Yucatan Peninsula of Mexico. J Med Entomol. 1987;24:498–502.

    Article  Google Scholar 

  30. Signoret JP, Baldwin BA, Fraser D, Hafez ESE. The behaviour of swine. In: Hafez E, editor. Behavior of domestic animals. London: Baillière Tindall; 1975. p. 295–329.

    Google Scholar 

  31. Muniz RA, Anziani OS, Ordoñez J, Errecalde J, Moreno J, Rew RS. Efficacy of doramectin in the protection of neonatal calves and post-parturient cows against field strikes of Cochliomyia hominivorax. Vet Parasitol. 1995;58:155–61.

    Article  CAS  Google Scholar 

  32. Chapter 2.1.10. New World screwworm (Cochliomyia hominivorax) and Old World screwworm (Chrysomya bezziana). In: OIE terrestrial manual. Paris: World Organisation for Animal Health (OIE); 2013.

  33. Bracke MBM. Review of wallowing in pigs: description of the behaviour and its motivational basis. Appl Anim Behav Sci. 2011;132:1–13.

    Article  Google Scholar 

  34. Laake EW, Cushing EC, Parish HE. Biology of the primary scew worm fly, Cochliomyia americana, and a comparison of its stages with those of C. macellaria. USDA Tech Bull. 1936;500(1):24.

    Google Scholar 

  35. Gaston W, Armstrong J, Arjo W, Stribling H. Home range and habitat use of feral hogs (Sus scrofa) on Lowndes County WMA, Alabama. Natl Conf Feral Hogs. 2008;2011:1–18.

    Google Scholar 

  36. de Barros GP, Bricarello PA. Myiasis by Cochliomyia hominivorax (Coquerel, 1858): a neglected zoonosis in Brazil. Open J Vet Med. 2020;10:80–91.

    Article  Google Scholar 

  37. Francesconia F, Lupi O. Myiasis. Clin Microbiol Rev. 2012;25:79–105.

    Article  Google Scholar 

  38. Hall MJR. Screwworm flies as agents of wound myiases. FAO World Animal Review. 1991. Accessed 27 May 2020.

  39. Readshaw JL. The influence of seasonal temperatures on the natural regulation of the screw worm, Cochliomyia hominivorax, in the southern U.S.A. Med Vet Entomol. 1989;3:159–67.

    Article  CAS  Google Scholar 

  40. Preve M. Designing plans to withstand climate change in Uruguay. United Nations Development Program. 2019. Accessed on 22 July 2020.

  41. Gutierrez AP, Ponti L. The New World screwworm: prospective distribution and role of weather in eradication. Agric For Entomol. 2014;16:158–73.

    Article  Google Scholar 

  42. Phillips PL, Welch JB, Kramer M. Seasonal and spatial distributions of adult screwworms (Diptera: Calliphoridae) in the Panama Canal Area. Republic of Panama. J Med Entomol. 2004;41:121–9.

    Article  Google Scholar 

  43. Rawlins SC. Current trends is screwworm myiasis in the caribbean region. Vet Parasitol. 1985;18:241–50.

    Article  CAS  Google Scholar 

  44. Salvador CH, Fernandez F. Biological invasion of wild boar and feral pigs Sus scrofa (Suidae) in South America: review and mapping with implications for conservation of peccaries (Tayassuidae). In: Meijaard E, Melletti M, editors. Ecology, conservation and management of wild pigs and peccaries. Cambridge: Cambridge University Press; 2017. p. 313–24.

    Chapter  Google Scholar 

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We thank the Asociación de Controladores de Jabalí de Artigas (ACJA) for evaluating the harvested feral swine for myiasis, sending larvae for microscopic examination, and providing the coordinates for the harvest sites. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA. This research was supported in part by the U.S. Department of Agriculture, Agricultural Research Service. The U.S. Department of Agriculture prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C.20250-9410, or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer.


This study was supported through funding from USDA-ARS project 3094-32000-038-00D.

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BPL, APA, and PVH conducted statistical tests and drafted the manuscript. MA, GC, SM collected and identified the specimens. All authors contributed to editing and content of the manuscript. All authors read and approved the final manuscript.

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Correspondence to Alex P. Arp.

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Supplementary information

Additional file 1: Dataset S1.

Data for all feral swine collected in the study. Data contains: date of sample, sex and size of captured feral swine, coordinates of capture, and if the swine had myiasis.

Additional file 2: Dataset S2.

All weather data used for correlations with temperature and precipitation.

Additional file 3: Dataset S3.

Data for all myiasis cases. GPS coordinates, location of sample, body location of myiasis, reported probable cause of myiasis.

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Altuna, M., Hickner, P.V., Castro, G. et al. New World screwworm (Cochliomyia hominivorax) myiasis in feral swine of Uruguay: One Health and transboundary disease implications. Parasites Vectors 14, 26 (2021).

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