Echinococcus multilocularis in Wisconsin

Abstract

The known geographic range of Echinococcus multilocularis is extended to include southern Wisconsin. E. multilocularis was reported from the arctic fox, Alopex lagopus L., on the mainland of Alaska by Rausch (1956, Am. J. trop. Med. Hyg. 5: 1086-1092) as the etiological agent of Alveolar Hydatid Disease on the North American Continent. Various workers (as reviewed by Ballard and Vande Vusse, 1983, J. Parasit. 69: 790-791) have reported this cestode from Canada and the contiguous United States. Previous reports have shown this cestode in Iowa, Illinois, Minnesota, Montana, Nebraska, North Dakota, South Dakota and Wyoming. The finding of E. multilocularis in Illinois and Nebraska (Ballard and Vande Vusse, 1983, loc. cit.) and the proximity to regions of high human population, prompted investigation of southern Wisconsin. One hundred and three red and gray foxes from 11 counties were obtained from fur buyers and trappers during the winter of 1982-83. Foxes were collected from Crawford, Dane, Grant, Green, Iowa, La Crosse, La Fayette, Richland, Rock, Sauk and Vernon counties. The small intestines were examined for parasites. Six of 72 (8.3%) red and 0 of 31 gray foxes were infected with E. multilocularis. Two males and 0 females of 8 red foxes from Green County, 1 female and 0 males of 7 red foxes from Iowa County, 2 females and 0 males of 8 red foxes from La Fayette County, and 1 male and 0 females of 4 red foxes from Vernon County were found to be infected with E. multilocularis. For those counties having foxes positive for E. multilocularis, the prevalence was 6 of 27 (22%). Infection of 3 of 38 and 3 of 34 males and females respectively would demonstrate no significant difference in prevalence between host sexes. Excluding 1 fox with a worm burden of 1,860, the average intensity of infection was 20 (range 10-1,860). There was no significant difference in intensity between host sexes. Fixed, gravid worms ranged in size from 1.3 to 3.4 mm (x = 2.06) in length. The number of testes ranged from 13 to 25 (x = 20) and most were posterior to the genital pore; the latter was located in the anterior one-half of the proglottid. The uterus was typically sacculate. A voucher specimen has been deposited in the USNM Helminthological Collection, accession number 78163. Boundaries of this potential health hazard to man have been fairly well delineated to include the prairie areas of Iowa, Illinois, Minnesota, Montana, Nebraska, North Dakota, South Dakota, Wyoming and now Wisconsin. Geographical expansion of this cestode's range is certainly a possibility and must be monitored in Illinois, Missouri and Nebraska. The assistance of Dr. Terry Amundson of the Wisconsin Department of Natural Resources in obtaining names of fur buyers and trappers is gratefully acknowledged. This investigation was supported in part by funds from a Faculty Research Grant from Mankato State University.