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1 December 2007 Cuterebrosis in a Florida Horse: First Equid Record for North America
Frank Slansky
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Larvae of Cuterebra spp. (Diptera: Oestridae) typically infest mice, rats, chipmunks, rabbits, hares, and certain other rodents or lagomorphs native to the Americas (Sabrosky 1986). However, non-native members of these orders, as well as mammals in other orders such as artiodactyls (e.g., deer and pigs), carnivores (raccoons, domestic cats and dogs, etc.), and primates (humans), can be parasitized by these bot flies (Hall 1925; Sabrosky 1986; Baird et al. 1989; Glass et al. 1998; Harris et al. 2000; Suedmeyer et al. 2000; Safdar et al. 2003; Slansky & Huckabee 2006; Slansky 2007a). Infestation of these atypical or accidental hosts, an affliction termed cuterebrosis or cuterebriasis, occurs when they contact first instars of Cuterebra spp. newly hatched from eggs oviposited in the habitats of the typical hosts (Catts 1982; Slansky & Kenyon 2003).

Published cases of cuterebrosis in perissodactyls (donkeys, horses, zebras, etc.) are few and mostly unsubstantiated. Knipling & Bruce (1937) reported that a second instar of Cuterebra buccata (Fabricius), a lagomorph-infesting species, was removed from a mule in South Carolina (16-VII-1935), but they provided no justification for this species assignment. Second instar Cuterebra spp. are very difficult to identify visually to species (even currently) and there were no descriptions of second instars of other Cuterebra spp. for comparison at the time of Knipling & Bruce's (1937) report. Thus, I consider the assignment of C. buccata for their specimen as unsubstantiated. Dalmat (1942) indicated that asses (donkeys) were atypical hosts of Cuterebra spp., but no details were given. Similarly, Sabrosky (1986) mentioned mules as atypical hosts of these bot flies, but supportive information was not provided.

During curation of the immature insect collection in the Department of Entomology & Nematology at the University of Florida, an isopropanol-preserved larva that appeared to belong to a Cuterebra species was encountered. This specimen had been collected from beneath the hide of a horse in Marion Co., Florida (11-VII-1991). This specimen possesses characteristics typical of a third instar Cuterebra spp., including dark brown cuticular platelets covering its body (Fig. 1a), 2 pair of sensory tubercles and 2 sharply pointed mouth hooks on its head (Fig. 1b) and on its anal segment (Fig. 1c), 2 kidney-shaped spiracular plates, each containing 3 wedge-shaped sections with serpentine spiracular slits (Fig. 1c inset). The larva is coated with a substantial amount of white material, which most likely is purulent matter from the host, as is often seen when these larvae infest atypical hosts (Slansky 2007b).

The species of Cuterebra that this specimen belongs to is unclear, as there are no taxonomic keys for species identification of larvae in this genus. However, the platelets covering its exterior either are ovoid, have blunt, single tips, or are multipointed, indicating this is a larva of a rodent-infesting Cuterebra species rather than that of a lagomorph-infesting species, third instars of which lack flattened, multipoint platelets and have many single-pointed, spine-like platelets (Knipling & Brody 1940; Dalmat 1942; Bennett 1955; Haas & Dicke 1958; Baird & Graham 1973; Slansky 2007a). There are three rodent-infesting species of Cuterebra in Florida: C. americana (Fabricius) (its main typical hosts are Neotoma woodrats), C. fontinella (Clark) (Peromyscus mice) and C. emasculator Fitch (Sciurus squirrels) (Slansky 2006). Cuticular platelet patterns are available only for the latter two species (Bennett 1955; Slansky & Huckabee 2006), and of these, this specimen more closely resembles C. fontinella (F.S., unpublished observations). However, determining the species of this specimen must await a morphological description of the third instar of C. americana, knowledge of intraspecific variation in morphological characteristics of these larvae (see Slansky & Huckabee 2006), and/or molecular analyses (Otranto et al. 2003; Noel et al. 2004) of the candidate species.

This appears to be the first record for Florida of cuterebrosis in a horse or other perissodactyl, and the first such record for a horse in North America. Based on the scarcity of published reports, infestation of these animals by larvae of Cuterebra appears to be a very rare phenomenon that should pose little concern to horse owners. This contrasts with the common occurrence of larvae of Gasterophilus spp. bot flies, which use horses and other perissodactyls as typical hosts and can require treatment to avoid pathological effects (Wall & Shearer 1997; Catts & Mullen 2002). One might expect that these animals would be exposed to Cuterebra spp. larvae both while grazing, especially lagomorph-infesting species that likely oviposit in grassy areas (e.g., Suedmeyer et al. 2000), and in their stalls, especially rodent-infesting species that may inhabit barns (F. S., unpublished observations). Thus, the rarity of published reports of cuterebrosis in perissodactyls may indicate that these atypical hosts exhibit resistance to parasitism by Cuterebra spp. larvae. Laboratory studies involving controlled infestations have shown that certain mammals outside the typical host spectrum of the Cuterebra spp. being tested can exhibit partial to complete resistance (reviewed in Slansky 2007b). Of course, failure in publishing cases of cuterebrosis involving these animals could also contribute to the scarcity of reports. A survey of large-animal veterinarians would be required to investigate the prevalence of cuterebrosis in these animals.

I thank Dr. Dale Habeck for bringing this specimen to my attention, Dr. Craig Welch for taking the photomicrographs used in this study, and Douglas Beckner for assistance in preparing the images. This work was supported in part by an instructional improvement grant from the College of Agricultural and Life Sciences at the University of Florida.


A third instar of a rodent-infesting Cuterebra spp. removed from under the hide of a horse in Marion Co., Florida, is described and illustrated. This appears to be the first record for Florida of cuterebrosis in a horse or other perissodactyl, and the first such record for a horse in North America.

References Cited


C. R. Baird and C. L. Graham . 1973. Cuterebra tenebrosa: Description of immature stages and a redescription of the adult (Diptera: Cuterebridae). Canadian Entomol 105:1281–1293. Google Scholar


J. K. Baird, C. R. Baird, and C. W. Sabrosky . 1989. North American cuterebrid myiasis. J. American Acad. Dermatol 21:763–772. Google Scholar


G. F. Bennett 1955. Studies on Cuterebra emasculator Fitch 1856 (Diptera: Cuterebridae) and a discussion of the status of the genus Cephenemyia Ltr. 1818. Canadian J. Zool 33:75–98. Google Scholar


E. P. Catts 1982. Biology of New World bot flies: Cuterebridae. Annu. Rev. Entomol 27:313–338. Google Scholar


E. P. Catts and G. R. Mullen . 2002. Myiasis (Muscoidea, Oestroidea). pp. 317-348 In G. Mullen and L. Durden [eds.], Medical and Veterinary Entomology. Academic Press, San Diego. 597 pp. Google Scholar


H. T. Dalmat 1942. A new parasitic fly (Cuterebridae) from the northern white-footed mouse. J. New York Entomol. Soc 50:45–59. Google Scholar


E. N. Glass, A. M. Cornetta, A. Delahunta, S. A. Center, and M. Kent . 1998. Clinical and clinicopathologic features in 11 cats with Cuterebra larvae myiasis of the central nervous system. J. Veterin. Intern. Med 12:365–368. Google Scholar


G. E. Haas and R. J. Dicke . 1958. On Cuterebra horripilum Clark (Diptera: Cuterebridae) parasitizing cottontail rabbits in Wisconsin. Parasitology 44–527–540. Google Scholar


M. C. Hall 1925. The occurrence of cuterebrid larvae in dogs and cats, and the possible modes of infection. J. Econ. Entomol. 18:331–335. Google Scholar


B. P. Harris, P. E. Miller, J. R. Bloss, and P. J. Pellitteri . 2000. Ophthalmomyiasis interna anterior associated with Cuterebra spp. in a cat. JAVMA 216:352–355. Google Scholar


E. F. Knipling and A. L. Brody . 1940. Some taxonomic characters of cuterebrine (Diptera) larvae, with larval descriptions of two species from Georgia. J. Parasitol 26:33–43. Google Scholar


E. F. Knipling and W. G. Bruce . 1937. Three unusual host records for cuterebrine larvae (Diptera: Oestridae). Entomol. News 48:156–158. Google Scholar


S. Noel, N. Tessier, B. Angers, and F-J. Lapointe . 2004. Molecular identification of two species of myiasis-causing flies (Cuterebra) by multiplex PCR and RFLP. Med. Veterin. Entomol 18:161–166. Google Scholar


D. Otranto, D. Traversa, B. Guida, E. Tarsitano, P. Fiorente, and J. R. Stevens . 2003. Molecular characterization of the mitochondrial cytochrome I gene of Oestridae species causing obligate myiasis. Med. Veterin. Entomol 17:307–315. Google Scholar


C. W. Sabrosky 1986. North American Species of Cuterebra, the Rabbit and Rodent Bot Flies (Diptera: Cuterebridae). Entomol. Soc. Amer. Thomas Say Foundation Monograph, College Park, MD. 240 pp. Google Scholar


N. Safdar, D. K. Young, and D. Andes . 2003. Autochthonous furuncular myiasis in the United States: case report and literature review. Clinical Infect. Dis 36:73–80. Google Scholar


F. Slansky 2006. Cuterebra bot flies (Diptera: Oestridae) and their indigenous hosts and potential hosts in Florida. Florida Entomol 89:152–160. Google Scholar


F. Slansky 2007a. Feline cuterebrosis caused by a lagomorph-infesting Cuterebra spp. larva. J. Parasitol 93:959–961. Google Scholar


F. Slansky 2007b. Insect/mammal associations: Effects of cuterebrid bot fly parasites on their hosts. Annu. Rev. Entomol 52:17–36. Google Scholar


F. Slansky and J. Huckabee . 2006. First records of rodent-infesting Cuterebra bot flies parasitizing raccoons (Procyon lotor) in North America. J. Parasitol 92:126–130. Google Scholar


F. Slansky and L. R. Kenyon . 2003. Cuterebra bot fly infestation of rodents and lagomorphs. J. Wildlife Rehab 26:37–16. Google Scholar


W. K. Suedmeyer, E. P. Catts, and E. Greiner . 2000. Cuterebra myiasis in a group of red kangaroos (Megaleia rufa), a Bennett's wallaby (Macropus rufogriseus fruticus) and a Gunther's dik dik (Maloqua guentheri smithi). J. Zoo Wildlife Med 31:124–128. Google Scholar


R. Wall and D. Shearer . 1997. Veterinary Parasitology. Chapman & Hall, London. 439 pp. Google Scholar


Fig. 1.

Third instar Cuterebra spp. removed from a horse in Marion Co., Florida. (A) Entire larva (ventral; anterior to left); the white coating likely is purulent matter from the host. (B) Head (dorsal toward top), with 2 pairs of sensory tubercles (white arrows indicate 1 of each pair) on the 2 anterior lobes, and the 2 sharply pointed mouth hooks (black arrow indicates 1 of these). (C) Posterior end (dorsal toward top), with the 2 centrally located, kidney-shaped spiracular plates (the white box surrounds 1 of these) in the anal segment, which is retracted within the penultimate segment. Each spiracular plate contains 3 wedge-shaped sections with serpentine spiracular slits (inset). Arrow indicates 1 of the flat, multipoint cuticular platelets that are visible on the penultimate body segment.

Frank Slansky "Cuterebrosis in a Florida Horse: First Equid Record for North America," Florida Entomologist 90(4), 795-797, (1 December 2007).[795:CIAFHF]2.0.CO;2
Published: 1 December 2007
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