Circumpolar Health 84:245-24?

THE CURRENT STATUS OF ALVEOLAR HYDATID DISEASE IN NORTHERN REGIONS ROBERT L. RAUSCH and JOSEPH F. WILSON The genus Echinocoeaus, in the family The cestode has not been recorded in Taeniidae, includes four species of very Greenland, to which arctic foxes periodical­ sma 11 tapeworms that occur as adults in ly migrate from eastern Canada (2). Its carnivores. The life cycles of these range is extensive in the Soviet Union, cestodes are completed by means of the where the distribution of cases of alveolar natural predator-prey relationship that hydatid disease has been defined by exists between the respective final and Lukashenko (3). A single case has been intermediate hosts, but when eggs of the reported in northern In di a ( 4) , and more adult parasites expelled by the final host than 100 cases have been diagnosed recently are ingested incidentally by man, the on the mainland of China (5). Numerous resulting larval stages of three of the cases have been found in northern Japan known species cause distinctive forms of (Hokkaido), where the cestode is extending hydatid disease. its range. Robbana et al. (6) reported a Two of these cestodes have extensive singe case also from northern Tunisia, in geographic ranges ir arctic and subarctic Africa. In North America, Echinocoecus regions, where infections in man have been muZtiZocuZaris was first recorded beyond the diagnosed predominantly among indigenous 1 imits of the zone of tundra in 1964, when populations. In northern regions, cystic Leiby and Olsen (7) found infected hydatid disease, caused by the larval stage in North Dakota. Since that time, it has of the northern form of Eehinocoeaus been reported in seven additional states, granuZosui Batsch, 1786, typically takes a and in the three adjacent provinces of benign course, and surgical intervention or Canada. The establishment of the cestode in other treatment is rarely necessary. In that region appears to be attributable to contrast, alveolar hydatid disease, caused the dispersal of eggs by arctic foxes that by the larval stage of Eehinocoeaus periodically migrate southward from the multiloau"la.ris Leuckart, 1863, is a serious tundra west of Hudson Bay (8). Continuing health problem in northern Eurasia and spread of Echinococcua rrrultilocuiaris in the northern North America. United States is predictable, since suitable In the circumpolar zone of tundra, maRJTialian hosts are widely present. Echinoaocaus 1'11UZtiZoauZaz'is occurs C011111only With reference to human disease in the in the arctic fox, but the red fox also Arctic and Subarctic, the highest rates have serves as final host. The larval stage of been recorded in the Iakut Autonomous the parasite develops in small rodents of Republic, northeastern Siberia. According the family Arvicolidae, which make up a high to Martynenko et al. (1), 604 primary cases proportion of the diet of foxes. In and of alveolar hydatid disease were diagnosed around settlements, dogs may capture and eat in the principal hospitals in Iakutia during rodents harboring the larval stage of this the period 1971 to 1980. Nemirovskaia et cestode. In settlements where such rodents al. (9) stated that rates of infection in take up a co11111ensal existence, and where hunters, trappers, and herders in the same dogs are numerous, hyperendemic foci may region ranged as high as 50 to 70 cases per exist. We consider that dogs are the usual 1,000. source of infection for the human popul a­ The pathogenesis of the larval stage of tion. When dogs are numerous, their feces EchinoeoC!cus rrruUiiocuZaris in man is grossly contaminate inhabited areas. In attributable to a high degree of incompati­ Iakutia, Martynenko et al. (1) found a bility between the parasite and the host. significant correlation between prevalence The larval cestode remains in the early, of alveolar hydatid disease and the use of proliferative phase of development, gradual­ potentially contaminated lakes for water ly infiltrating adjacent hepatic tissue. supply. Whether wild foxes are a signifi­ Very large hepatic lesions may develop over cant source of human infection has not been a period of years, and encroachment on major clearly established. Most human infections hepatic vessels is not unusual. Metastasis are evidently acquired early in life, but to the lungs or brai11 may occur in patients alveolar hydatid disease usually does not with advanced hepatic disease. become clinically apparent before middle In Alaska, alveolar hydatid disease is age. a serious health problem among Eskimos multiZocularis has an living on St. Lawrence Island and along the holarctic distribution in the northern western coast of the mainland. Only 37 hemisphere. In the Arctic and Subarctic, it cases have been diagnosed in Alaska, with occurs from Latvia east to the Bering Sea, about one new case per year. Nonetheless, and from western Alaska at least to Hudson's this disease causes far more morbidity and Bay. It is present on islands in the Bering mortality than does, for example, a disease Sea, and in the Canadian Arctic Archipelago. such as rabies, which receives much greater ______245 246 Infeatious Disease

public attention. During the past four muUi7..ocu7..aris is not feasible. In Alaska, years, patients with alveolar hydatid prevention of infection in man would seem to disease have required 361 days of hospital­ depend on public education and improved ization, at a cost of about $157,750 per sanitation. Whereas numbers of sled dogs year, at one hospital alone. have been markedly reduced in many villages The diagnosis of alveolar hydatid during recent yea rs, the po ten ti a 1 benefit disease is usually made when patients of that reduction seems to have been offset present with an abdominal mass, or a posi­ by the growing popularity of maintaining tive serological titer. Serological surveys dogs as pets. have been increasingly important, and Measures for the prevention and treat­ diagnoses of 9 cases have been made primari­ ment of alveolar hydatid disease require ly by this means. In an additional 10 further definition. Of high priority is the cases, serological findings were important need to establish better methods in the in conjunction with other tests in estab­ medical management of nonresectable lesions. lishing the clinical diagnosis. Through cooperation with the Department of In alveolar hydatid disease, the Chemistry, University of Alaska (Anchorage), preclinical period may be prolonged, perhaps we have assessed serum levels of mebendazole as much as 10 to 25 years. Detection of under different modes of administration and early cases while the lesion is small and dosage. Results to date indicate that serum more amenable to surgical resection has been levels are usually quite low, probably below emphasized in our work. A program for the effective therapeutic level. Available identifying patients at risk of having information suggests that albendazole may early-stage lesions by means of serological give improved therapeutic levels, and we surveys has been conducted by us for a plan to include this drug in chemothera­ number of years. Thus far in this effort, peutic trials as soon as it becomes avail­ we have failed to identify patients at an able for use. Broader based serological early stage of infection. We are continuing surveys of populations in the endemic this work, with the hope that more refined regions are being conducted this year (1984) diagnostic techniques, such as more sophis­ in conjunction with the Alaska state hepat­ ticated CT-scans, will give better results. itis s tu di es. The need for more effective Surgical resection of the lesion screening tests for laboratory use is re­ remains the treatment of choice, but only cognized. 19% of our cases have been resectable for The establishment of better diagnostic cure. These seven patients are all living, methods, the implementation of effective with an average surviva 1 time post-surgery programs of control of the cestode in dogs, of 19 years (range: 10 to 31 years). One and improved chemotherapy of alveolar has evidence of recurring disease. In the hydatid disease present some difficult but management of nonresectable lesions, we have promising challenges for future investiga­ been engaged in a clinical trial of tions. Any success in these efforts in mebendazole therapy since 1974. Results in Alaska can be expected to have important these patients are still being assessed. implications in other regions of the Arctic On the one hand, it appears that the drug and Subarctic, as well as in endemic regions has had a beneficial effect, since it has at lower latitudes. prolonged survival time, given symptomatic improvement, and shown a possible arrest of REFERENCES metastasis. On the other hand, the parasite 1. Martynenko VB, Maiorova LA, Zorihina tissue in the lesions seems usually to VI, Suvorina VI. Epidemiologiia remain viable, probably because of difficul­ al' veokokkoza v taezhnoi zone Iakuti i. ties in obtaining sufficiently high serum Med Parazit 1983; 61:38-40. levels of the drug. 2. Rausch RL, Fay FH, Williamson FSL. Traditionally, it has been shown that Helminths of the arctic fox, AZopex hydatid disease, in the broad sense, can be lagopus (L.), in Greenland. Can J Zool controlled by appropriate measures to 1983; 61:1847-1851. disrupt the life cycle of the cestode. But 3. Lukashenko NP. Al'veokokkoz (al'veoli­ prevention of alveolar hydatid disease and arnyi ekhinokokkoz). Moskva: Medit­ the control of the etiologic agent are much sina, 1975. (See map, Figure 49). more difficult than, for example, the 4. Aikat BK, Bhusnurmath SR, Cadersa M, control of cystic hydatid disease. This has Chhuttani PN, Mitra AK. 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