Robert L. Rausch

Studies on the helminth fauna of Alaska. XXV. The ecology and public health significance of Echinococcus sibiricensis Rausch & Schiller, 1954, on St. Lawrence Island.

According to Eguchi (1934), two species of salmon (Oncorhynchus) serve as a source of human infection by a cesode indentified as Diphyllobothrium latum (Linnaeus, 1758), in Japan. The possible role of these fishes in the transmission of cestodes to man and other animals has not been investigated in North America, nor, apparently, on the Eurasian mainland. However, Ward (1930) reported unidentified Diphyllobothrium-like plerocercoids from Alaskan salmon; Simms and Shaw (1931) collected plerocercoids identified as D. cordiceps (Leidy, 1871) from Oncorhynchus kisutch (Walbaum) from lakes in Oregon; and Wardle (1932) reported plerocercoids of Diphyllobothrium spp. from 0. kisutch and 0. nerka (Walbaum) in western Canada. Cestodes of the genus Diphyllobothrium Cobbold, 1858, are commonly harbored by bears on Kodiak Island, in the Gulf of Alaska. During the months of summer and early fall, these mammals feed largely upon salmon, which spawn in great numbers in the streams of the island. Since fishes of other species are rarely obtainable, with the exception of a herring, Clupea pallasii Valenciennes, which spawns along the coast in early spring, the circumstances strongly suggest that the bears are infected through ingesting plerocercoid larvae in salmon. Five species of Oncorhynchus occur in the waters of Kodiak Island, and all are important as human food. Aboriginal methods of preparing fishes for human consumption are such that cestode larvae might remain viable for some time. Localization of plerocercoids in parts of the fish used for food would provide opportunity for human infection.

A PHYLOGENETIC HYPOTHESIS FOR SPECIES OF THE GENUS TAENIA (EUCESTODA: TAENIIDAE)

Cladistic analysis of a numerical data matrix describing 27 characters for species of Taenia resulted in 4 most parsimonious phylogenetic trees (174 steps; consistency index = 0.28; homoplasy index = 0.72; retention index = 0.48). Monophyly for Taenia is diagnosed by the metacestode that is either a cysticercus or a form derived from a bladder-like larva; no other unequivocal synapomorphies are evident. Tree structure provides no support for recognition of a diversity of tribes or genera within the Taeniinae: Fimbriotaeniini and Taeniini have no phylogenetic basis. Hydatigera, Fimbriotaenia, Fossor, Monordotaenia, Multiceps, Taeniarhynchus, Tetratirotaenia must be subsumed within Taenia as synonyms. Taenia saginata and Taenia asiatica are sister species and distantly related to Taenia solium. Cospeciation with respect to carnivorous definitive hosts and Taenia appears to be limited. Although felids are putative ancestral hosts, contemporary associations appear to have resulted from extensive host-switching among felids, canids, hyaenids, and others. In contrast, relationships with herbivorous intermediate hosts are indicative of more pervasive coevolution; rodents as intermediate hosts are postulated as ancestral for the Taeniidae, Taenia + Echinococcus. Patterns appear consistent with rapid shifts between phylogenetically unrelated carnivores but among those that historically exploited a common prey resource within communities in specific biogeographic regions.

Studies on the helminth fauna of Alaska. XXVII. The occurrence of larvae of Trichinella spiralis in Alaskan mammals.

An effort was made to obtain a series of each species of mammal occurring in Alaska, with exception of the ungulates. Such specimens were collected over the entire Territory, but most originated above the Arctic Circle. Many mammals were secured through the cooperation of Eskimo and Indian trappers, who held the frozen carcasses of animals taken for their fur until they could be brought to the laboratory in Anchorage. In some instances, only muscle tissue of animals, with collecting data, was preserved. The personnel of the Zoonotic Disease Section also collected large numbers of mammals. Dogs were generally obtained when those no longer serviceable were destroyed, but some were purchased for this study. Although some autopsies were performed in the field, most of the animals were brought entire to the laboratory. For the purposes of this work, several grams of striated muscle were taken, routinely from the diaphragm, at the autopsy of each animal. These samples were frozen and stored for later processing. The larvae were usually dead when isolated. The presence of Trichinella larvae was determined through the artificial digestion of tissue samples. For this purpose, the tissue was chopped with a knife into small pieces, placed in a solution of pepsin and hydrochloric acid, and incubated at 37? C. with constant agitation for 24 hours. The resulting fluid was poured through a fine-mesh screen to remove any undigested material and was allowed to stand in graduated cylinders until any larvae present settled out. The supernatant fluid was siphoned off, the residue placed in watch glasses with a few drops of 10 percent

Cystic Echinococcosis in the Arctic and Sub-Arctic

The northern biotype of Echinococcus granulosus occurs throughout the holarctic zones of tundra and taiga, from eastern Fennoscandia to the Bering Strait in Eurasia and in North America from arctic Alaska approximately to the northern border of the United States. The cycle of the cestode is complex in taiga at lower latitudes, because of the greater diversity of potential hosts. In the Arctic and Subarctic, however, four patterns of predator/prey relationships may be discerned. Two natural cycles involve the wolf and wild reindeer and the wolf and elk (moose), respectively. Where deer of the two species coexist, both are prey of the wolf; the interactions of the wolf and elk are here described on the basis of long-term observations made on Isle Royale (in Lake Superior near the southern limit of taiga), where only the wolf and elk serve as hosts for E. granulosus. A synanthropic cycle involving herding-dogs and domesticated reindeer caused hyperendemicity of cystic echinococcosis in arctic Eurasia, mainly in northeastern Siberia. The 4th pattern, a semi-synanthropic cycle, formerly existed in Alaska, wherein sled-dogs of the indigenous hunters became infected by consuming the lungs of wild reindeer. The sequence of changes in life-style inherent in the process of acculturation affected the occurrence of cystic echinococcosis among nomadic Iñupiat in arctic Alaska. When those people became sedentary, the environs of their early villages soon became severely contaminated by faeces of dogs, and cases of cystic echinococcosis occurred. Compared to cystic echinococcosis caused by E. granulosus adapted to synanthropic hosts (dog and domestic ungulates), the infection produced by the northern biotype is relatively benign. Nearly all diagnosed cases of cystic echinococcosis (> 300) in Alaska have occurred in indigenous people; only one fatality has been recorded (in a non-indigenous person). After sled-dogs were replaced by machines, cases have become rare in Alaska. A similar effect has been observed in Fennoscandia, in the Saami and domesticated reindeer. Recent records indicate that the prevalence of cystic echinococcosis is increasing in Russia, suggesting that dogs are used there in herding.

New Aspects of Neotropical Polycystic (Echinococcus vogeli) and Unicystic (Echinococcus oligarthrus) Echinococcosis

SUMMARY Of the four species of the genus Echinococcus (Cestoda) distinguished by biological and morphological characteristics, two species, E. vogeli and E. oligarthrus, occur widely in the Neotropics. Approximately 200 cases of polycystic echinococcosis (PE) have been recorded from 12 countries in South America. Following early proliferation of E. vogeli in the human host, typically in the liver, the metacestode usually spreads in the peritoneal and pleural cavities, and numerous organs may be invaded. The clinical characteristics of PE in 81 patients with sufficient information are reviewed. Type I disease consists of polycysts in the liver and abdominal cavity (37% of the patients had this characteristic); type II is similar to type I but also includes hepatic insufficiency (26%); type III consists of cysts in liver and chest (14%); type IV consists of cysts only in the mesenteries (16%); and type V consists of cysts calcified in liver and lung (4%). The percentage of patients with polycysts in the liver was 81%, and the percentage of patients with polycysts in the chest was 14%. PE is most ready diagnosed by geographic origin of the patient and by means of ultrasound or computerized tomography scanning showing cysts and calcifications. The highest mortality was for patients with type II disease, due to hepatic failure and its complications. There were five patients who died due to surgical accidents, whereas 35 cases had uncomplicated surgery. Twenty-three patients died of PE, making the total mortality 29% (23 of 78 cases). None of the 13 patients treated only with albendazole, the most efficacious treatment, was completely cured. PE represents a severe medical problem in South America. A reevaluation of the characteristics of the metacestode of E. oligarthrus indicated that it is unicystic. Only three human cases are known (two with infection in the orbit and one with infection in the heart). The metacestode of E. oligarthrus, in contrast with that of E. vogeli, consists of a spherical, fluid-filled vesicle that enlarges concentrically and is not known to undergo exogenous proliferation.

A programme to reduce the risk of infection by Echinococcus multilocularis : the use of praziquantel to control the cestode in a village in the hyperendemic region of Alaska

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.

Echinococcus Infections in Man and Animals in Kenya

More than 30 per cent. of the cattle, sheep and goats slaughtered in the central abattoir of the Kenya Meat Commission have hydatid cysts in either the liver or the lungs; the rate is even higher in animals slaughtered in the rural abattoirs (Ginsberg, 1958; Froyd, 1960). In spite, however, of the wide distribution in livestock, hydatids are rarely seen in man, except in the northern desert region of Turkana where the disease is particularly prevalent (Wray, 1958). Both Ginsberg and Wray suggested that this limited distribution might be explained if the main hosts of the parasite were hyaenas and jackals, not dogs. This hypothesis was supported by the absence of previous records of Echinococcus in dogs in East Africa. In the present study on hydatid disease in Kenya, special emphasis was given to an assessment of the role of wild animals as reservoirs of the parasite. More than 100 carnivores were examined for the adult worms and nearly 2,000 miscellaneous animals were examined for the larval stages. Several wild animals were found to be lightly infected, but the main cycle of transmission was between dogs and domestic livestock. A few minor morphological differences were seen in the Kenya material, but it was concluded that the species in dogs and wild carnivores was Echinococcus granulosus.

A review of the genus Echinococcus Rudolphi, 1801.

During a recent investigation in Kenya, Echinococcus adults were obtained from 25 domestic dogs (Canis familiaris), three hyaenas (Crocuta crocuta), three wild hunting dogs (Lycaon pictus), and a jackal (Thos mesomelas) (Nelson and Rausch, 1963). In view of the occurrence of several species of Echir.JCOCCUS reported from South Africa by Cameron (1926) and by Ortlepp (1934, 1937), a detailed study was necessary before the specific status of the Kenya material could be determined. We were fortunate in having available reference material from various parts of the world. As a result of this study it is concluded that only three of the I I named species of Echinococcus can be distinguished by purely morphological criteria, six are regarded as synonyms of E. granulosus (Batsch, 1786), and the status of two is uncertain. was not discussed. More recent studies indicate that some of these earlier conclusions were erroneous. This species has become widely distributed as a result of the extensive movement of domesticated animals. It is indigenous at high latitudes on the North American and Eurasian continents, where the life-cycle involves the wolf (Canis lupus) and various species of deer. A variable anatomy has been observed in both adults and larvae. Some of the variations recorded in the strobilar stage may have resulted from different methods of collection and preservation, and those in the larval stage are partly due to the effect of different host species. Among the possibly existing biological strains of E. granulosus only now being investigated, one, E. granulosus canadensis Cameron, 1960, has been named on the basis of its peculiar host-parasite relationships and possible serological differences. Measurements and morphological data for E. granulosus are summarized in Table 1. Further data are to be found in the comparative study of material from Kenya (Nelson and Rausch, 1963). In the strobilar stage this species is distinguished by the number and distribution of the testes, by the position of the genital pore, and by the form of the gravid uterus

Hydatid disease (Echinococcosis) in Alaska and the importance of rodent intermediate hosts.

Hydatid disease, caused by the larval form of a tapeworm, Echinococcus granulosus (Batsch, 1786), is of circumpolar distribution, but has not previously been considered to be of much public health significance in North America. It is the purpose of this paper to present observations on this disease in Alaska, with special reference to its transmission to man. Magath (1) reviewed all known North American cases and concluded that most of these had been contracted abroad. Infections in dogs have likewise been considered rare; in his review of the literature, Riley (2) could find but one North American record and concluded that wild carnivora and herbivora serve to maintain this parasite in the United States and Canada. Subsequent work has borne out this conclusion. The occurrence of E. granulosus in wild animals in North America has been reviewed by McT. Cowan (4). The data derived from intensive parasitological investigations of the mammalian fauna of Alaska, carried on by us over the past two years, indicate that E. granulosus is well established in the Territory, in both dogs and wild canids. In arctic Alaska, particularly, where dogs are commonly very closely associated with man, there is unusual opportunity for human exposure to this parasite. The finding of infected dogs in several arctic Eskimo villages (Barrow, Kotzebue, Wainwright, Unalakleet, Anaktuvuk Pass) indicates that potentially, if not actually, a serious human health problem is involved. In addition, we have recorded this parasite from both red and arctic foxes in northern Alaska, and from the wolf over the greater part of the Territory. Moose and caribou apparently serve as the essential intermediate hosts on the mainland, since the examination of several hundred mammals of other species has failed to disclose the larval infection. The practice of the natives of feeding dogs the discarded parts from moose and caribou enhances the possibilities for canine infection. Although the status of hydatid disease in Alaska is in general poorly known, preliminary studies on St. FIG. 1. Specimen of Microtus oeconomus showing location and appearance of larval cysts of E. granulosus.

Transberingian dispersal of cestodes in mammals

During Pleistocene glaciations, eustatic lowering of sea-level exposed the continental shelf between northeastern Eurasia and northwestern North America. That land in combination with unglaciated areas on the adjacent continents formed a vast region open to the west but bounded on the east by continental ice. Organisms from Eurasia spread into the unglaciated Beringian refugium, which was biotically an eastward extension of the Palaearctic. With rising sea-levels following glacial periods, the Bering Strait was formed and organisms of Eurasian origin were left within the nearctic sector of Beringia. As the continental ice disappeared, plants and animals spread eastward and southward from Beringia, while organisms from beyond the southern margins of the ice extended their ranges northward. The significance of Beringia is discussed with reference to the dispersal of host-specific cestodes in mammals that attained holarctic status during the late Pleistocene.