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Objective: The authors reviewed the pathophysiology and clinical management of endemic alveolar hydatid disease in Alaskan Eskimos, incorporating recent developments in diagnosis and treatment., Summary Background Data: Alveolar hydatid disease is a highly lethal zoonotic infection caused by the larval stage of Echinococcus multilocularis. This cestode is restricted geographically to northern climates, where foxes and small rodents represent the natural hosts. Domestic dogs also may serve as definitive hosts, and thus, transmit the parasite to humans. Human infection is characterized by the development of a cancer-like hepatic mass, which may extend to adjacent structures or metastasize to distant sites. If the infection goes untreated, mortality reaches 80%., Methods: The medical records of all patients with alveolar hydatid disease diagnosed or treated at the Alaska Native Medical Center between 1951 and 1993 were reviewed. Forty-two cases of active disease are presented., Results: Nine patients underwent resection of hepatic lesions with intent to cure, and each had a favorable result. Average post-diagnosis survival of those patients was 22 years; six still are living and free of disease. Partial resections or drainage procedures were performed in ten patients. Chemotherapy was used to augment the surgical treatment of eight patients, and four received chemotherapy alone, resulting in improved outcomes compared with historic controls. Late complications included hepatic abscess, biliary obstruction, and portal venous hypertension., Conclusions: Whereas alveolar hydatid disease rarely is encountered in other areas of North America, the biologic potential for spread of the disease may be increasing because of illegal importation of infected foxes to the Eastern seaboard. Therefore, the surgical community should maintain an awareness of the diagnosis and management of this potentially devastating parasitic infection.

Evidence that the larval stage of Echinococcus multilocularis in humans is killed by chemotherapy is presented in a review of our 17-year experience with treatment of alveolar hydatid disease in Alaska. The efficacy of chemotherapy was assessed with use of an in vivo assay of parasite viability by means of inoculation of voles, immunohistochemical tests, and histopathologic findings. Of 14 tests performed for nine patients, 12 in vivo assays (86%) were negative after chemotherapy, while only two (17%) of 12 vole tests for seven untreated patients were negative. Regression of arrest of growth of metastatic and primary hepatic lesions, together with their partial-to-complete calcification and prolonged survival times has been observed among patients treated with the benzimidazole compounds. For six who received appropriate chemotherapy, treatment has been discontinued for an average of 4.6 years (range, 3-7 years) without an increase lesion size or other evidence of reactivation.

This paper reports the results of a 10-year field trial designed to reduce the risk of infection by Echinococcus multilocularis to residents of a village in a hyperendemic area (Savoonga, St. Lawrence Island). The objective was to prevent dispersal of infective eggs of the cestode within the village by means of monthly treatments of dogs with praziquantel. Northern voles, Microtus oeconomus, present in the village as commensals, served as an index of risk, as the incidence of infection in the voles provides information about the availability of eggs within the confines of the inhabited area. Voles were examined annually during early June before the population of overwintering voles was diluted by the first annual litters. The pretreatment infection-rate within the village was 29% (range 22-35%), and in control areas at some distance from the village for the entire study period it averaged 53% (284 infected voles from a sample of 533). Some fluctuation in incidence of infection in village voles occurred, apparently depending on the extent to which the residents kept their dogs chained and thus available for treatment. The success of the programme was demonstrated by the reduction in prevalence of infection to about 1% of voles in 1985, and an average infection rate during the last five years of the study of 5% (29 infected voles in a sample of 582). This 83% average reduction in the prevalence of the larval cestode within the village reflects a corresponding reduction in the risk of acquiring by the residents of the village. The method would be applicable for the control of E. multilocularis in most hyperendemic regions. Success depends, however, on elimination of unrestrained dogs and a precise schedule of treatment.

Forty-two patients with oesophageal cancer were identified among Alaskan Natives from 1955 through 1981. Based on rates for US whites, there were 1.3 and 3.8 times the number of Native men and women diagnosed with oesophageal cancer as expected. Forty of the patients were Eskimo or Aleut, resulting in an incidence for Eskimo-Aleuts of 10.9 for males and 8.3 for females per 100 000 adjusted to the world standard population. The distribution of cancer patients by residence at diagnosis showed marked regional clustering, which has been observed among oesophageal cancer patients in several other areas of the world.

We studied 19 Eskimo patients with alveolar hydatid disease from the north-western coast of Alaska for risk factors for infection with Echinococcus multilocularis. Each case-patient was matched by age and sex with 2 unrelated controls who had no clinical or serologic evidence of infection with E. multilocularis and who resided in three villages endemic for alveolar hydatid disease. Behaviors thought to increase exposure to E. multilocularis and the chronologic occurrence of these behaviors in the participant's life were assessed by a standardized questionnaire. Case-patients were more likely than controls to have owned dogs for their entire lives (odds ratio 6.00, P less than 0.05), tethered their dogs near the house (odds ratio 8.50, P less than 0.05), and lived in houses built directly on the tundra rather than on gravel or a permanent foundation (odds ratio 11.00, P less than 0.01). Case-patients were not more likely to have owned sled dogs, trapped or skinned foxes, or engaged in other outdoor activities away from home. These findings suggest that controlling the parasite in the domestic dog population, as well as controlling the dog population itself, are important aspects of preventing alveolar hydatid disease in the northwestern Native Alaskan population.

The clinical features of 33 cases of alveolar hydatid disease (AHD) in Alaskan Eskimos and a review of the surgical experience with this disease are presented. Among untreated patients, progression of the disease to a fatal outcome was observed in 70%. The primary hepatic lesion resembles cancer, and errors in diagnosis by both the surgeon and pathologist are common. Although surgical resection of the entire primary hepatic lesion offers the only proven curative treatment, only 26% of those explored were resectable. All seven patients resected for cure are alive 6-27 years post-operatively (average survival, 14.7 years). A 5-year experience with continuous mebendazole therapy in the management of five nonresectable cases of AHD indicates that a favorable effect of this drug is being observed. It now appears that Echinococcus infections are no longer the sole province of the surgeon. Although the role of medical therapy is not yet clearly defined, it must be considered in the management of all cases of AHD. The first reported locally-acquired case of AHD in the conterminous United States, and the widespread occurrence and expanding range of E. multilocularis in the north-central United States and south-central Canada, point to the increasing public health importance of alveolar hydatid disease.