Wohlfahrtia vigil

Wohlfahrtia vigil

<p align="CENTER"><span style="font-size: large;"><i><b>Wohlfahrtia vigil</b></i></span><span style="font-size: large;"><b> Walker</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>Wolhfartia</i></span><span style="font-size: medium;"> for Dr. Wohlfart and </span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> = keeping vigil about the host</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>SYNONYMS:</b></span><span style="font-size: medium;"><i>Paraphyto</i></span><span style="font-size: medium;"><i>chittendeni</i></span><span style="font-size: medium;"> Coquillett, </span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>HISTORY:</b></span><span style="font-size: medium;"> Walker (1920, 1922, 1931) reported the first and subsequent cases of </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> in children; Brady (1923) and Chown (1924) reported additional cases in infants. Johanssen (1926) reported this parasite in rabbits near Ithaca, New York, USA while Kingscote (1931) reported the disease in a silver fox puppy. The first documentation of this parasite in domestic cats was in a report by Kingscote (1935) who recorded it in four cats; he also recorded the parasite in mink, man, dogs, ferrets, rabbits and foxes. </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> produces an extremely rare cutaneous myiasis in cats. Only one case report of </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> in cats, a case from the Veterinary Teaching Hospital at Colorado State University could be documented using the Veterinary Medical Data Base (Purdue University, West Lafayette, Indiana, USA),. </span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>GEOGRAPHIC DISTRIBUTION:</b></span><span style="font-size: medium;"> This parasite is responsible for cutaneous myiasis in North America, particularly in southern Canada and the northern part of the United States (James, 1947). The adult flies have been recorded from the New England states to Alaska (Walker, 1931), but most records of myiasis produced by their larvae are from eastern sections of Canada and the neighboring northeastern parts of the United States. The area in which most cases have been recorded extends roughly from the 43rd parallel of latitude to the 50th and from the 74th to the 104th parallels of longitude. The most southern record is from Erie, Pennsylvania; the northern from Winnipeg, Manitoba; the eastern from Montreal, Quebec; and the western from the Dakotas (Kingscote, 1935). A case of </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"> has been reported in a cat from the Veterinary Teaching Hospital, Colorado State University (Personal communication, Nancy Hampel, DVM, 1994). </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;"> Many members of the family Sarcophaginae, the flesh flies, deposit their eggs or larvae in carrion, others in purulent wounds or sores, and others in feces. </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> is the only species for which all reports of infection are in the skin of healthy animals (Walker, 1931). Infection follows the deposition of fly larvae on the unbroken skin of young animals. The lesions in cats have been predominantly located on the head, often between the eyes (Kingscote, 1935). </span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>IDENTIFICATION:</b></span><span style="font-size: medium;"> Adult </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> are non-parasitic and as a result will probably not be observed by the client or the veterinarian. They are large, grayish flies (approximately 13 mm in length), about twice the size of the house fly, </span><span style="font-size: medium;"><i>Musca</i></span><span style="font-size: medium;"><i>domestica</i></span><span style="font-size: medium;">. The dorsal surface of the thorax is marked with three longitudinal bands, while the dorsal surface of the abdomen exhibits three, well-defined rows of oval black spots which are confluent with one another (Kingscote, 1935). </span></p> <p align="JUSTIFY"><span style="font-size: medium;"> The first larval stage will probably go unnoticed due to its small size, from 1.5 mm at its hatching to 3.5 mm at the time of its molt to the second stage. The third stage is from 7.0 to 16.5 mm in length. The second stage fills in the size gaps. All three stages are "maggot-like" in their appearance and exhibit cephalopharyngeal sclerites and posterior spiracles that are unique to the species (Walker, 1931). The third stage larva is a large larva. Its posterior end is narrow and its integument is covered with many irregular rows of small, dark pointed, posteriorly directed spines which are larger than those of the members of the genus </span><span style="font-size: medium;"><i>Sarcophaga</i></span><span style="font-size: medium;">. This larva is better adapted to maintain an attachment to living tissues. The oral hooks are strongly developed and the cephalopharyngeal skeleton is like that of the larva of </span><span style="font-size: medium;"><i>Sarcophaga</i></span><span style="font-size: medium;">. The posterior end of the larva has its spiracular plate located in a deep pit formed by the margins of the segment. The posterior spiracles have slits that are wider and a peritreme that is stronger and wider than those of </span><span style="font-size: medium;"><i>Sarcophaga</i></span><span style="font-size: medium;"> species (Kingscote, 1935, Walker, 1937). </span></p> <p align="JUSTIFY"><span style="font-size: medium;"> The second and third stage larval </span><span style="font-size: medium;"><i>Wohlfartia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> are the stages that will be usually observed in the skin of an infested cat by either the owner or the veterinarian. These stages can probably be best identified by an entomologist. Extensive descriptions and dichotomous keys for these larval stages are available (Johannsen, 1921, Walker, 1937, James and Gasser, 1947). </span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>LIFE CYCLE: </b></span><span style="font-size: medium;"> This flesh fly is larviparous; it deposits larvae instead of eggs on healthy and uninjured skin of suitable hosts (Eschle and DeFoliart, 1965). The larva penetrates the unbroken skin and forms a boil-like (furuncular) swelling through which the posterior end of the larva may be seen. Here the larva develops to the third larval stage. The larval development is usually completed in nine to fourteen days (Kingscote, 1935). The parasite then leaves the host tissue, drops to the ground and pupates. The pupation period usually lasts from eleven to eighteen days; this variation corresponds with season of the year and the temperature. When cold weather approaches, the pupation period is greatly prolonged. Under laboratory conditions, it has been observed to last seven months. The parasite survives the winter in the pupal form. The adults emerge from pupae and about three or four days later mate. About a week later, the female flies commence larviposition, depositing six to sixteen larvae at a time. The female flies live from thirty-five to forty days. The males seldom survive more than three weeks (Kingscote, 1935). Details of the life cycle of </span><span style="font-size: medium;"><i>Wohlfartia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> have been defined in the laboratory (Ford, 1932, Ford, 1936, Eschle and DeFoliart, 1965).</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>//CLINICAL PRESENTATION AND PATHOGENESIS:</b></span><span style="font-size: medium;"> The female </span><span style="font-size: medium;"><i>Wohlfartia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> deposits active larvae in the neighborhood of a suitable host or directly on the host itself. The larva penetrates the unbroken skin and forms a boil-like (furuncular) swelling through which the posterior end of the larva may be seen. In small animals, penetration may go deeper than the dermal tissue, even into the coelomic cavity.</span></p> <p align="JUSTIFY"><span style="font-size: medium;"> The first indication that an animal is infected is an exudation of serum and matting of haircoat over the site of penetration. In light skinned animals, a small inflammatory area is noticeable in the center or to one side of which a tiny opening is at times visible. As the lesions develop, they may be palpated. On the third or fourth day, the larvae are 1.5 to 2.0 cm in length and produce an abscess-like lesion resembling a warble of </span><span style="font-size: medium;"><i>Hypoderma</i></span><span style="font-size: medium;"> species in cattle. These lesions vary in size, shape, position, and the number of larvae they may contain. The haircoat often becomes parted over the summit of the lesions and reveals an opening generally 2.0 to 3.0 mm in diameter. The posterior aspect of the larvae are presented to these openings through which they breathe. These openings are circular and well-defined. If several larvae are present in a single lesion, the shape of the aperture is quite variable. Small animals infected with five or more larvae for several days become emaciated and the skin becomes dry and loses its lustre. </span></p> <p align="JUSTIFY"><span style="font-size: medium;"> The penetration of the skin by the larvae, their development in the subcutaneous tissues and the secondary bacterial infection produce intense irritation and inflammation of the tissues. Attempts by the cat to remove the larvae or relieve the irritation tend to aggravate the condition. There is fever, loss of appetite and rest, and progressive emaciation. Young animals may die from exhaustion. It has also been suggested that the larvae may produce toxic secretions (Kingscote, 1935). </span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>DIAGNOSIS:</b></span><span style="font-size: medium;"> The presence of a dermal swelling with a central opening may lead to a tentative diagnosis of myiasis due to </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;">. A definitive diagnosis can be made only after extraction and identification of a typical larva. Extensive descriptions and dichotomous keys for the three larval stages are available (Johannsen, 1921, Walker, 1937, James and Gassner, 1947). </span></p> <p align="JUSTIFY"><span style="font-size: medium;"> A tentative diagnosis may often be made by a history of either residence in or travel to a geographic area endemic for </span><span style="font-size: medium;"><i>Wohlfartia</i></span><span style="font-size: medium;">. </span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;">. There are other flies from different areas throughout the world which might produce a lesion similar to </span><span style="font-size: medium;"><i>Wohlfartia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;">. These should also be considered in a differential diagnosis. These myiasis-producing flies include: </span><span style="font-size: medium;"><i>Cordylobia</i></span><span style="font-size: medium;"><i>anthropophaga</i></span><span style="font-size: medium;">, the African Tumbu fly; </span><span style="font-size: medium;"><i>Dermatobia</i></span><span style="font-size: medium;"><i>hominis</i></span><span style="font-size: medium;">, the South American tórsalo fly; </span><span style="font-size: medium;"><i>Chrysomyia</i></span><span style="font-size: medium;"><i>bezziana</i></span><span style="font-size: medium;">, the Oriental fly; </span><span style="font-size: medium;"><i>Cochliomyia</i></span><span style="font-size: medium;"><i>hominivorax</i></span><span style="font-size: medium;">, the primary screwworm, and </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> species, the rabbit botfly. The obligatory myiasis-producing flies should be considered in the differential diagnosis in cats with an appropriate residence or travel history.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>TREATMENT: </b></span><span style="font-size: medium;">The larva must be extracted from the skin of the feline host. As with all flies that localize in subcutaneous tissues, treatment is based on the requirement of the larvae for communication with the outside environment. Air exchange is accomplished via the larva's posterior spiracles. The airway may be occluded using heavy oil, liquid paraffin, pork fat or petroleum jelly. </span></p> <p align="JUSTIFY"><span style="font-size: medium;"> Surgical intervention involves the injection of lidocaine hydrochloride into the furuncular lesion. This anesthetizes both the cat and the larva, allowing the larva to be manually extracted using thumb forceps. Antibiotics should be prescribed. </span></p> <p align="JUSTIFY"><span style="font-size: medium;"> Great care should be taken during the extraction process to avoid rupturing the larva </span><span style="font-size: medium;"><i>in situ</i></span><span style="font-size: medium;">, although no mention is made in the literature of anaphylaxis as occurs when larvae of </span><span style="font-size: medium;"><i>Cuterebra</i></span><span style="font-size: medium;"> species are ruptured during the extraction process. In suspect cases, the extracted larva should be submitted to an entomologist for definitive diagnosis.</span></p> <p align="JUSTIFY"></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>EPIZOOTIOLOGY:</b></span><span style="font-size: medium;"> There is evidence that adult rabbits and rodents may be implicated in maintaining populations of the fly other than in the whelping season of the carnivore host. It appears that the combination most conducive to a severe outbreak of myiasis in mink is warm temperatures in May and June following a winter with good snow cover and a decline in the rabbit population (Eschle and DeFoliart, 1965). Children and young mink, ferrets, dogs, cats, foxes and rabbits may become infected from the beginning of June until the end of September. Adult animals are seldom affected (Kingscote, 1935). </span></p> <p align="JUSTIFY"><span style="font-size: medium;"><b>HAZARDS TO OTHER ANIMALS:</b></span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> is a pest of fox and mink ranches in parts of the United States and Canada. Young, newborn animals are attacked, usually fatally. Dogs, rodents and rabbits may be attacked (Kingscote, 1935,). Craine and Boonstra (1986) described myiasis by </span><span style="font-size: medium;"><i>Wohlfartia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> in nestling </span><span style="font-size: medium;"><i>Microtus</i></span><span style="font-size: medium;"><i>pennsylvanicus</i></span><span style="font-size: medium;">. Although birds, mice, and other small mammals may be suitable hosts for </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;">, it has been observed that the cottontail rabbit, </span><span style="font-size: medium;"><i>Sylvilagus</i></span><span style="font-size: medium;"><i>floridanus</i></span><span style="font-size: medium;"><i>mearnsii</i></span><span style="font-size: medium;">, is an especially suitable host and perhaps the major host (Johannsen, 1926, Eschle and DeFoliart, 1965).</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;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> has been recovered from the skin of young children, particularly infants. The tender skin of young children may prove to be a route of easy penetrati`</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;">Brady MJ. 1923. Cutaneous myiasis in an infant-</span><span style="font-size: medium;"><i>Wohlfahrtia vigil</i></span><span style="font-size: medium;"> (Walker) infection. Arch Pediat 40:638-640.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Chown G. 1924. Report of a case of cutaneous myiasis in an infant. </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> (Walker) Infect 14:967-968.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Craine ITM, Boonstra R. 1986. Myiasis by </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> in nestling </span><span style="font-size: medium;"><i>Microtus</i></span><span style="font-size: medium;"><i> pennsylvanicus</i></span><span style="font-size: medium;">. J Wild Dis 22:587-589</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Eschle J.L., DeFoliart G.R. 1965. Rearing and biology of wohlfahrtia vigil (Diptera; Sarcophagidae). Ann Entomol Soc Am 58:849-855.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Ford N. 1932a. Observations on the behaviour of the sarcophagid fly, </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> (Walker). J Parasitol 19:106-111.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Ford N. 1936. Further observations on the behaviour of </span><span style="font-size: medium;"><i>Wohlfartia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> (Walk.) With notes on the collecting and rearing of the flies J Parasitol 22:309-328.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Holmes PR and KellM. 1922. Some cases of cutaneous myiasis, with notes on the larvae of </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> (Walker). J Parasitol 9:1-5.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">James MT. 1947. The flies that cause myiasis in man. USDA Misc Pub No. 631; 175 pp.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">James M.T., Gassner F.X. 1947. The immature stages of the fox maggot, </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>opaca</i></span><span style="font-size: medium;"> Cog. J Parasitol 33:241-252.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Johannsen OA. 1921. The first instar of </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> (Walker). J Parasitol 7:154-155.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Johannsen OA. 1926. </span><span style="font-size: medium;"><i>Wohlfahrtia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> a parasite upon rabbits. J Parasitol 13:156.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Kingscote AA. 1931a. A case of myasis in silver black fox produced by </span><span style="font-size: medium;"><i>Wohlfartia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> (Walker). Ont Vet Coll, pp 38-39.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Kingscote AA. 1935. Myiasis in man and animals due to infection with the larvae of </span><span style="font-size: medium;"><i>Wohlfartia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> (Walker). Ontario Vet Col Rep 51-69.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Walker EM. 1920. </span><span style="font-size: medium;"><i>Wohlfartia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> (Walker) as a humjan parasite (Diptera-Sarcohagidae). J Parasitol 7:1-77</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Walker EM. 1922. Some cases of cutaneous myiasis with notes on the larvae of </span><span style="font-size: medium;"><i>Wohlfartia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> (Walker). J Parasitol 9:1-5.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Walker EM. 1931. Cutaneous myiasis in Canada. Can Pub Hlth J 22:504-508.</span></p> <p align="JUSTIFY"><span style="font-size: medium;">Walker EM. 1937. The larval stages of </span><span style="font-size: medium;"><i>Wohlfartia</i></span><span style="font-size: medium;"><i>vigil</i></span><span style="font-size: medium;"> Walker. J Parasitol 23:163-174.</span></p>