Cuterebra species

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Cuterebra species
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<p align="CENTER"><span style="font-size: large;"><i><b>Cuterebra</b></i></span><span style="font-size: large;"><b> species</b></span></p> <p align="CENTER"><span style="font-size: large;"><b>(Figures 4-57 through 4-)</b></span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>ETYMOLOGY:</b></span><span style="font-size: medium;"><i>Cutis</i></span><span style="font-size: medium;"> = skin and </span><span style="font-size: medium;"><i>terebro</i></span><span style="font-size: medium;"> = to bore.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>HISTORY: </b></span><span style="font-size: medium;">The genus </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> was first described by Bracy Clark in 1815; however, the first published record is that of John Lawson (1709) in his book "A New Voyage to Carolina" (both cited in Sabrosky, 1986). The North American species of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> were described in detail by Sabrosky (1986) who provides an in-depth taxonomic description of each species that he considered valid. In this work, Sabrosky divided the genus </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> into two subgenera: </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> and </span><span style="font-size: medium;"><i>Trypoderma</i></span><span style="font-size: medium;">. </span><span style="font-size: medium;"><i>Cuterebra Cuterebra</i></span><span style="font-size: medium;"> spp. are parasites of lagomorphs while </span><span style="font-size: medium;"><i>Cuterebra Trypoderma</i></span><span style="font-size: medium;"> spp. are parasites of rodents.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>GEOGRAPHIC DISTRIBUTION:</b></span><span style="font-size: medium;"> Western hemisphere, throughout the Americas. Fossils of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> that have been dated to be from 60 million years before the present have been recovered in North America (Townsend, 1942). There are maps showing collection sites of each North American species of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> in Sabrosky (1986).</span></p> <p align="JUSTIFY"><span style="font-size: medium;"> According to Sabrosky (1986) there are 34 species of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> in North Ameria. There are 12 species in the subgenus </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> and 22 species in the subgenus </span><span style="font-size: medium;"><i>Trypoderma</i></span><span style="font-size: medium;">. Of the 12 members of the </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> subgenus parasitic on rodents, three species, </span><span style="font-size: medium;"><i>C. C. emasculator </i></span><span style="font-size: medium;">and </span><span style="font-size: medium;"><i>C.C. fontinella</i></span><span style="font-size: medium;">, and </span><span style="font-size: medium;"><i>C. C. americana, </i></span><span style="font-size: medium;">are found in the Eastern United States with the latter being more southern in distribution. Of the 22 species in the subgenus </span><span style="font-size: medium;"><i>Trypoderma</i></span><span style="font-size: medium;"> parasitic on lagomorphs, two species, </span><span style="font-size: medium;"><i>C. T. abdominalis</i></span><span style="font-size: medium;"> and </span><span style="font-size: medium;"><i>C.T. buccata</i></span><span style="font-size: medium;">, are distributed throughout the eastern United States, one species, </span><span style="font-size: medium;"><i>C. T. cuniculi</i></span><span style="font-size: medium;">, is restricted to the southeastern coastal areas, and one species, </span><span style="font-size: medium;"><i>C. T. maculosa</i></span><span style="font-size: medium;">, is restricted to Panama and Guatamala. The remaining 27 species of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> are found in the western United States and in Mexico and Central America.</span></p> <p align="JUSTIFY"><span style="font-size: medium;"> There are related genera, </span><span style="font-size: medium;"><i>Metacuterebra</i></span><span style="font-size: medium;">, </span><span style="font-size: medium;"><i>Pseudogametes</i></span><span style="font-size: medium;">, </span><span style="font-size: medium;"><i>Rogenhofera</i></span><span style="font-size: medium;"> and </span><span style="font-size: medium;"><i>Andinocuterebra</i></span><span style="font-size: medium;"> that parasitize rodents in South America. Also, the genus </span><span style="font-size: medium;"><i>Alouttamyia</i></span><span style="font-size: medium;"> is found in the necks of howler monkeys, </span><span style="font-size: medium;"><i>Alouatta</i></span><span style="font-size: medium;"> spp., and has been reported on several occasions from humans (Fraiha </span><span style="font-size: medium;"><i>et al</i></span><span style="font-size: medium;">., 1984). None of these genera have been reported from cats.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>LOCATION IN HOST:</b></span><span style="font-size: medium;"> The larval stages of this parasite are commonly found in furuncular lesions in the skin of the rodent host. In the cat, these furuncular lesions may appear on the cheek, neck, top of the head, or on the thorax (Fischer, 1983). Larvae have also been reported from the nasal pharynx (Thirloway, 1982; Wolf, 1979), from the pharyngeal area (Kazacos </span><span style="font-size: medium;"><i>et al.</i></span><span style="font-size: medium;">, 1980), and from the orbit (Fischer, 1983) and anterior chamber of the eye (Johnson </span><span style="font-size: medium;"><i>et al.</i></span><span style="font-size: medium;">, 1988). Intracranial myiasis due to larval </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> has been reported in cats on several occasions (Hendrix </span><span style="font-size: medium;"><i>et al.</i></span><span style="font-size: medium;">, 1989).</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>IDENTIFICATION: </b></span><span style="font-size: medium;">The adults are about the size and shape of bumble bees (Fig. 5-57). If one wants to identify the adult fly from a bot recovered from a warble, it will be necessary to allow the bot to pupate in some soil in a jar covered with a bit of screen or mesh; however, it has been found that bots from aberrant hosts often do not successfully pupate to the adult stage even under the best of conditions (Catts, 1982) The mature larva is characterized by its large size (about 3 cm) and the large spines on the segments (Fig. 5-59). These larvae also have spiracles that are distinctive of the genus with three serpentine openings forming what appears as three pie-shaped slices tracts within each spiraclular opening (Fig. 5-59) The spines on the anterior and posterior bands can be used to determine whether or not the larva is of the "rodent" or "lagomorph" subgenera (Sabrosky, 1986). The "rodent" bots have somewhat flattened, platelike spines, occasionally somewhat conical, usually bifid to many pointed in the anterior and posterior bands of spines on each segment. The mature larvae of the "rabbit" bots have conical, single-pointed spines, especially in the anterior and posterior bands on most segments (Fig. 5-60). The first and second instar larvae of the rodent and rabbit bots can be recognized by the large bands of dark spines that are present on the body segments (Fig. 5-61). These larvae have spiracles that are different from the mature third instar (Fig. 5-62).</span></p> <p align="JUSTIFY"><span style="font-size: medium;"> In histological sections, the larvae of Cuterebra can be recognized by their large size and the spines on the surface of the body. Baird </span><span style="font-size: medium;"><i>et al</i></span><span style="font-size: medium;">., 1989, describe the features that can be used to distinguish between the gnerea </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;">, </span><span style="font-size: medium;"><i>Dermatobia</i></span><span style="font-size: medium;">, and </span><span style="font-size: medium;"><i>Cordylobia</i></span><span style="font-size: medium;"> in tissue sections.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>LIFE CYCLE: </b></span><span style="font-size: medium;">Adult bot flies live only a few weeks, during which they mate and lay eggs (Figs. 5-63 &amp; 5-64). Each day, male rodent botflies find and defend lek territories within botfly aggregation sites (Catts, 1994). When virgin females enter the area of congregation, they become conspicuous by making multiple flights over the summit. They are they chased by a male who will grab the female in midair with copulation being completed on land. Once the female has mated she then goes off to lay her eggs. The female bot fly lays her eggs in different locations depending on the species. The typical female will lay one to several thousand eggs, in groups of around 5-15 per site. Some species lay the eggs on grass stems, wood chips, and bark along narrow trails or rodent runs near the opening to the rodent burrow (similar methods are employed by the horse bots, </span><span style="font-size: medium;"><i>Gasterophilus</i></span><span style="font-size: medium;"> spp. when they attach eggs to the hairs of the face and legs of the horse), while other species actually enter the rodent burrow and lay their eggs within it.</span></p> <p align="JUSTIFY"><span style="font-size: medium;"> Eggs of these bots hatch in response to sudden rises in temperature. The newly hatched larvae are moist and stick to the fur coats of passing rodents and lagomorphs. Hosts typically become infected by larvae entering some natural body opening (e.g., mouth, nose, eyes, or anus). It had been reported that larvae can enter through unbroken skin (Beamer and Penner, 1942; Penner, 1958), but this could not be repeated by other workers (Catts, 1982). Once within the rodent host, the larvae remain as first stages within the nasopharyngeal region for 6 to 8 days (Baird, 1975; Catts, 1967) where the small transparent larvae are found at the posterior end of the soft palate in the nasal passages of experimentally infected house mice and woodrats (Neotoma fuscipes). In these mice, the larvae remained quite small and transparent being only 2 to 3 times larger than the larvae that hatch from eggs. Work with other species of bots has shown that there may be a migration to the area of the trachea, migration through the tracheal wall into the thoracic cavity followed by migration through the diaphragm into the abdominal cavity prior to movement to their subcutaneous positions in the inguinal and thoracic areas (Gingrich, 1981). Once within the subcutaneous site, the larvae molt to the second instar and continue to grow within the developing warble. The molt to the third stage occurred around 17 to 19 days after infection in the case of </span><span style="font-size: medium;"><i>C. latifrans</i></span><span style="font-size: medium;"> (actually occurring about two days earlier in the house mouse). During the last 4 or 5 days of development, the larva enlarges the pore of the warble to make exit possible. It takes about 10 hours for the active larva to back out of the warble once the segments posterior to the spiracles are exposed. The time of larval maturation, from infection to when the larva leaves the warble, ranges from slightly less than 3 to over 8 weeks. The maturation time of the rodent bots seems to be on the average more rapid than that of the rabbit bots; the rodent bots tend to develop in three to four weeks while the rabbit bots tend to require 4 to 6 weeks.</span></p> <p align="JUSTIFY"><span style="font-size: medium;"> Once the fully developed third-stage larva leaves the host, it burrows into the soil where pupation occurs. It may be anywhere from a month to several years before the adult fly emerges from the pupal case. Also, if larvae have developed in less than adequate hosts, there is a good chance that adult flies will not develop from the mature larvae, even after pupation (Catts, 1982).</span></p> <p align="JUSTIFY"><span style="font-size: medium;"> The seasonality of infection is due to the timing of adult emergence in the late spring. Then, after 1 to 2 weeks for mating, the eggs are laid by the fertilized females. It then typically takes approximately 3 to 4 weeks for the warbles to become apparent. In the cooler climates, there is typically only one hatching of adults each year; however, in warmer climates, there is likely to be less ordered hatching of adult flies (Catts, 1982). There may be an occasional infection observed in winter in colder climates due most likely to eggs maintained within some protected location within the environment.</span></p> <p align="JUSTIFY"><span style="font-size: medium;"> Cats probably become infected as they prowl in areas frequented by rodents and rabbits. It is possible for very young kittens to be infected with larvae crawling about on the queens fur. It is not known how the larvae enter the cat, but it would be assumed that they enter through the mouth, nose, or anus as they do in the rodent and lagomorph hosts.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>CLINICAL PRESENTATION &amp; PATHOGENESIS:</b></span><span style="font-size: medium;"> Clinical signs depend largely on where the larvae have migrated. Cases tend to be more common during the mid-summer to fall months. The most common presentation is that of a subcutaneous warble (a 2 to 4 mm opening with well defined margins through the skin with a serosanguinous discharge). In these cases, the mature third-stage larva with its pair of large spiracles can be observed moving within the pore of the warble (Fig. 5-65). Most warbles occur around the face or neck; rarely, larvae may enter the globe of the eye causing chemosis, blepharospasm, serous occular discharge, and exudative uveitis with blindness. The larvae may be observed within the anterior chamber of the eye (Johnson </span><span style="font-size: medium;"><i>et al</i></span><span style="font-size: medium;">, 1988; Fischer 1983). Some owners may observe the warble earlier in its development when the larva is smaller and often white to light cream colored. On these larvae, the dark body spines are clearly visible (Fig. 5-61). When extracted, the larva is found to be several centimeters long and often quite dark (Figs. 5-58 and 5-66). Typically, there are no signs of disease or distress in cats. </span></p> <p align="JUSTIFY"><span style="font-size: medium;"> Those cats in which larvae migrate through the brain develop neurologic disease, the clinical signs of which depend on the migratory path of the larva. Clinical signs vary from acute onset of status epilepticus with no recovery, to multiple signs (head tilt, unilateral or bilateral central blindness, head pressing, dementia, continuous vocalization, abnormal placing reflexes, circling) designating multifocal CNS lessions, to only severe depressed mentation (Hendrix </span><span style="font-size: medium;"><i>et al.</i></span><span style="font-size: medium;">, 1989; McKenzie </span><span style="font-size: medium;"><i>et al.</i></span><span style="font-size: medium;">, 1978; Bennett </span><span style="font-size: medium;"><i>et al.</i></span><span style="font-size: medium;">, 1985; Cook </span><span style="font-size: medium;"><i>et al.</i></span><span style="font-size: medium;">, 1985). Many cats present in states of dementia, disorientation, and inappropriate responses to external stimuli Glass et al., 1998). After an acute onset, signs are usually rapidly progressive with a fatal outcome; more rarely, some cases may linger for weeks or months. Some cases bare a strinking similarity to the syndrome of feline ischemic encephalopathy (Cook </span><span style="font-size: medium;"><i>et al.</i></span><span style="font-size: medium;">, 1985; Summers </span><span style="font-size: medium;"><i>et al.</i></span><span style="font-size: medium;">, 1995). Although reported, it is uncommon for cats that develop neurologic disease to initially present with the cutaneous manifestations (warble) of infection (Hendrix </span><span style="font-size: medium;"><i>et al</i></span><span style="font-size: medium;">, 1989). At necropsy, larvae may be observed intracranially (Fig. 5-67) or within the spinal cord (Figs. 5-68 and 5-69).</span></p> <p align="JUSTIFY"><span style="font-size: medium;"> Some cats, after an acute onset of cerebral signs, recover and are left with residual signs of abnormal behavior, e.g., constant pacing or circling, abnormal mentation, or seizures. Occasionally spontaneous recovery appears to be complete. </span></p> <p align="JUSTIFY"><span style="font-size: medium;"> Another typical presentation in cats can be signs of respiratory distress or upper respiratory disease. Some present with a history of sneezing and nasal discharge (sometimes for up to a weeks duration), unilateral facial swellings especially over the nose, extreme respiratory dyspnea sometimes with a bloody nasal discharge, and soft palate and pharyngeal swelling (Kazacos </span><span style="font-size: medium;"><i>et al</i></span><span style="font-size: medium;">, 1980; Thirlaway, 1982; Wolf, 1979). Laryngeal edema resulting in laryngeal obstruction and respiratory arrest due to migration of a larvae in the cervical neck has been reported in a snow leopard (Ryan </span><span style="font-size: medium;"><i>et al</i></span><span style="font-size: medium;">, 1990). Unlike cutaneous lesions, respiratory signs more often precede the development of neurologic signs (Cook </span><span style="font-size: medium;"><i>et al</i></span><span style="font-size: medium;">., 1985; Personal Communication - SC Barr and A de Lahunta). Typically, if neurologic signs develop, they do so 1 to 2 weeks after respiratory signs, although respiratory signs may occur as long as 4 to 10 weeks before the onset of neurologic disease (Cook </span><span style="font-size: medium;"><i>et al</i></span><span style="font-size: medium;">, 1985). </span></p> <p align="JUSTIFY"><span style="font-size: medium;"> There seems to be a good indication that cerebrospinal cuterebriasis in cats is associated with or the cause of feline ischemic encephalopathy (Williams et al., 1998). This disease is not known to occur in areas where </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> is not present, and it occurs most commonly at the same time of the year as cases of cuterebriasis. It is postulated that the vascular spasm associated with feline ischemic syndrome may be due to some toxin elaborated by the circulating fly larva.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>DIAGNOSIS:</b></span><span style="font-size: medium;"> Infections with </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> in cats are typically observed in the late summer and early fall in those parts of North America that have cold enough winters to prevent year-round fly activity on a regular basis. A </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> bot in a warble in the back of a cat is distinctive and diagnostic. Larvae migrating to cause neurologic or respiratory signs represent more of a challenge. The clinician should be suspicious of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> infection in cats developing severe upper respiratory disease (especially with unilateral signs of nasal discharge or nasal/facial swellings) during the late summer or fall months. Acute onset of neurologic disease sometimes preceded by a upper respiratory signs 1 to 2 weeks previously should provide strong suspicion of intracranial cuterebral myiasis. In some cats with upper respiratory signs, a leukocytosis with eosinophilia is pressent on peripheral hemograms. However, hemotology and serum biochemistry findings are usually nonspecific and but might help to rule out other diseases. If neurologic signs are present, cerebrospinal fluid analysis may show an elevation in protein, and pleocytosis with either neutrophils, mononuclear cells, or eosinophils. A CAT scan of an affected cat revealed a mottled appearance to the brain consistet with encephalitis, but no conclusive evidence of infection. Magnetic resonence immaging toreveal larvae or their migration tracks in the brain of affected animals appears to show promise, but as of yet images have not yet been published or the details of the observed lesions described (deLahunta, personal communication). In cases presenting with upper respiratory disease, examination of the pharynx, larynx, and nasal passages under general anesthesia may reveal a larvae. </span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>TREATMENT:</b></span><span style="font-size: medium;"> Treatment of cuterebriais currently requires the surgical extraction of the bot or bots. When mature bots are present within a warble, they are probably going to extract themselves very shortly, but they can be assisted in their leaving of the warble by the expansion of the pore and extraction with forceps, using care not to crush the bot. Squashing the larvae within the warble may result in a severe tissue reaction resulting from a Type I hypersensitivity-like reaction. Smaller and less developed larvae within the skin will require removal by careful dissection. Similarly, larvae within the soft tissues of the mouth, nasal sinus, larynx, or eye will require surgical extraction.</span></p> <p align="JUSTIFY"><span style="font-size: medium;"> When larvae are present intracranially or within the spinal cord, the treatment of choice is likely to remain the extraction of the larva. As methods or radiographic imaging are improving, it may become possible to localize the developing larva and extract it. As of this time, however, no such success has been reported. </span></p> <p align="JUSTIFY"><span style="font-size: medium;"> Ivermectin has been shown to be effective against </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> species at 0.1 mg/kg, and is well tolerated when given at 0.3 mg/kg. Ivermectin (0.3 mg/kg subcutaneously on alternate days for 3 treatments) in association with corticosteroids has been reported in 2 cats with neurologic signs; in both cats the eventual outcome of the infection was not improved, although the larvae in 1 case at necropsy was decomposing (Hendrix </span><span style="font-size: medium;"><i>et al.</i></span><span style="font-size: medium;">, 1989). </span></p> <p align="JUSTIFY"><span style="font-size: medium;"> At Cornell Veterinary College, a limited number of cats with the upper respiratory syndrome during late summer and fall have responded to the above regimen of ivermectin treatment (but given orally) combined with prednisone (1 mg/kg, PO, q 12 h for 3 weeks, then 1 mg/kg, PO, q 24 h for 3 weeks). Although the diagnosis has been presumptive, these cases improve and none to date have developed neurologic disease. </span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>EPIZOOTIOLOGY:</b></span><span style="font-size: medium;"> In the northern United States, most cases are observed in late summer and early fall; this is due to the univoltine life cycle of flies in these latitudes, i.e., flies only mate and lay eggs once a year. Thus, most rodents, rabbits, and cats are being infected at about the same time in the summer. Work at an aggregation site in Marin County, California, revealed that the most males of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> latifrons were present at the site around the end of August, although males were present from the beginning of June through the end of October (Catts, 1967). At an aggregation site in Pennsylvania, the most males of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> fontinella were present in the first haft of August, with males being present from mid to late June through the first half of september (Schiffer , 1983). The appearance of warbles in the late summer and early fall would coincide with the three to six weeks required for the larvae to reach the stage where they are ready to leave the host and pupate. In climates where the flies are multivoltine, there is the likely possibility that the seasonality of bot appearance would be less dramatic than in the cooler climes.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>HAZARDS TO OTHER ANIMALS:</b></span><span style="font-size: medium;"> The larva in the back of the cat is no hazard to either the handler or the other animals that may share the hospital areas. </span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>HAZARDS TO HUMANS:</b></span><span style="font-size: medium;"> The larva in the cat is not a hazard to humans. There have been reports, however, of the recovery of larvae of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> from humans who have become infected in much the same manner as cats (Baird </span><span style="font-size: medium;"><i>et al.</i></span><span style="font-size: medium;">, 1989; Schiff, 1993). Most human cases have been reported in the northeastern United States within late August and early September. In humans most larvae have been recovered from the head, neck, shoulders and chest. There have been rare cases of ocular and upper respiratory involvement. It does not appear that central nervous system disease happens in humans as it does in cats.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>CONTROL/PREVENTION:</b></span><span style="font-size: medium;"> Owners could be advised of the life cycle, but it would be difficult to prevent a cat with a desire to hunt from visiting potential sites of egg deposition. Thus, it is important to make owners in areas where the neurologic disease occurs to be aware that the signs of respiratory infection in late summer and early fall would warrant a veterinary consultation and the potential need for careful monitoring.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>REFERENCES:</b></span></p> <p align="JUSTIFY"><span style="font-size: medium;">Baird CR. 1975. Larval development of the rodent bot fly, </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"><i>tenebrosa</i></span><span style="font-size: medium;">, in bushy-tailed wood rats and its relationship to pupal diapause. Can J Zool 53:1788-1798.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Baird JK, Baird CR, Sabrosky CW. 1989. North American cuterebrid myiasis; report of seventeen new infections of human beings and review of the disease. J Am Acad Dermatol 21:763-72.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Beamer RH, Penner LR. 1942. Observation on the life history of a rabbit cuterebrid, the larvae of which may penetrate the human skin. J Parasitol 28(supl):25.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Bennett RA, Lowrie CT, Bell TG. 1985. An intracranial Cuterebra sp larva in a cat. Calif Vet 39:13-14,49</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Catts EP. 1967. Biology of a California rodent bot fly </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"><i>latifrons</i></span><span style="font-size: medium;"> Coquillett (Diptera: Cuterebridae). J Med Ent 4:87-101.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Catts EP. 1982. Biology of new world bot flies: Cuterebridae. Ann Rev Entomol 27:313-338.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Catts EP. 1994. Sex and the bachelor bot (Diptera: Oiestridae). Amer Ent ???Fall 1994???: 153-160.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Cook JR, Levesque DC, Nuehring LP. 1985. Intracranial cuuterebral myiasis causing acute lateralizing meningoencephalitis in two cats. JAAHA: 21:279-284.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Fischer K. 1983. </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> larvae in domestic cats. Vet Med, Sm Anim Clin 78:1231-1233.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Gingrich RE. 1981. Migratory kinetics of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"><i>fontinella</i></span><span style="font-size: medium;"> (Diptera: Cuterebridae) in the white-footed mouse, </span><span style="font-size: medium;"><i>Peromyscus leucopus</i></span><span style="font-size: medium;">. J Parasitol 67:398-402.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Glass EN, Cornetta AM, deLahunta A, Center SA, Kent M. 1998. Clinical and clinicopathologic features in 11 cats with </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> larvae myiasis of the central nervous system. J Vet Int Med 12:365-368.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Hendrix CM, Cox NR, Clemons-Chevis CL, DiPinto MN, Sartin EA, 1989. Aberrant intracranial myiasis caused by larval </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> infection. Comp cont ed Pract Vet 11:550-559.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Johnson BW, Helper LC, Szajerski. 1988. Intraocular Cuterebra in a cat. JAVMA 193:829-830.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Kazacos KR, Bright RM, Johnson KE, Anderson KL, Cantwell HD. 1980. </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> sp. as a cause of pharyngeal myiasis in cats. JAAHA 16: 773-776.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">McKenzie BE, Lyles DI, Clinkscales JA. 1978. Intracerebral migration of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> larva in a kitten. JAVMA 172:173-175.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Penner L.R. 1958. Concerning a rabbit cuterebrid, the larvae of which may penetrate the human skin (Diptera, Cuterebridae). J Kans Ent Soc. 31:67-71.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Ryan JA, Roudebush P, Shores JA. 1990. Laryngeal obstruction associated with cuterebrosis in a snow leopard (</span><span style="font-size: medium;"><i>Felis uncia</i></span><span style="font-size: medium;">). J Zoo Wild Med 21:351-352.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Schiff TA. 1993. Furuncular cutaneous myiasis caused by </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> larva. J Am Acad Dermatol. 28:261-263.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Shiffer CN. 1983. Aggregation behaviour of adult </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"><i>fontinella</i></span><span style="font-size: medium;"> (Diptera: Cuterebridae) in Pennsylvania, USA. J Med Entomol 20:365-370.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Summers BA, Cummings JF, de Lahunta A. 1995. Feline ischemic encephalopathy. </span><span style="font-size: medium;"><b>In:</b></span><span style="font-size: medium;"> Chapter 5. Degenerative diseases of the central nervous system, </span><span style="font-size: medium;"><span style="text-decoration: underline;">Veterinary Neuropathology</span></span><span style="font-size: medium;">. pages 242-244.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Thirloway L. 1982. Aberrant migration of a </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> larva in a cat. Vet Med/Sm Anim Clin 77:619-620.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Townsend CHT. 1942. Manual of Myiology, part 12. Sao Paulo, Brazil.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Williams KJ, Summers BA, de Lahunta A. 1998. Cerebrospinal cuterebriasis in cats and its associationwith feline ischemic encephalopathy. Vet Pathol 35:330-343.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Wolf AM. 1979. </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> larva in the nasal passage of a kitten. Feline Pract 9:25-26.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-57. </b></span><span style="font-size: medium;">Adult </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> sp. Typically, the living fly holds its wings along the body when at rest.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-58. </b></span><span style="font-size: medium;">Third-stage larva of a </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> sp. removed from a cat. This larva is about 3 cm in length.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-59. </b></span><span style="font-size: medium;">Spiracles on the posterior of the mature </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> sp. removed from a cat.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-60.</b></span><span style="font-size: medium;"> Spines on the body of a third-stage larva of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> recovered from a rabbit. They are conical with single points.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-61</b></span><span style="font-size: medium;"> Second instar larva surgically removed from a subcutaneous lesion on a cat.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-62</b></span><span style="font-size: medium;">. Spiracles of a second-instar larval </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> recovered from a cat.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-63. </b></span><span style="font-size: medium;">Diagram of the life cycle and pathology caused by </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> spp. in cats. The adult female fly lays its eggs on grass, plant stems, bark, or wood chips around the entrance to a rodent burrow. After several days, the larvae have matured and hatch from the eggshell in response to increases in temperature; some larvae can persist within the eggs for months. The hatched larvae attach to a passing host and then enter the body of the host through a opening such as the mouth or nose. In the rodent and rabbit hosts, the larvae migrate first to areas associated with the lungs or pharynx, and then migrate to the subcutaneous site where the larva matures within the warble. Once the larva has matured, it drops to the ground where it wriggles into the soil to pupate. Typically, the pupal stage is the stage in which the fly overwinters, with the adults emerging from the pupal case in the spring. The most common presentation in the cat is to have the larvae developing in a warble much like they do in the rodent or rabbit with the posterior end of the bot with its large paired spiracles protruding from the opening in the warble. In the cat, neurologic manifestations of infection can be caused by early stage larvae migrating into the spinal cord or brain and amy produce lesions similar to those seen in feline ischemic encephalopathy with appreciable asymmetry of the cerebral hemispheres.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-64. </b></span><span style="font-size: medium;">The major life stages of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"><i>cuniculi</i></span><span style="font-size: medium;">.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-65. </b></span><span style="font-size: medium;">A warble in the back of a cat with a mature third-instar larva.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-66. </b></span><span style="font-size: medium;">The larva removed the warble in the back of the cat in Figure 8.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-67. </b></span><span style="font-size: medium;">Exposed larva within a cat that was euthanatized with severe neurologic signs. [Photo courtesy of Dr. A de Lahunta]</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-68. </b></span><span style="font-size: medium;">The spinal cord of a cat showing a </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> sp. </span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>Figure 5-69. </b></span><span style="font-size: medium;">A histological section of a spinal cord of a cat showing the aposition of the </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> larva to the cord material. The larva can be recognized by the large black triangles which represent sections through the large body spines presnet on the developing bot's surface.</span></p>
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