Trichinellosis of animals in Chukotka, USSR: A general review

intematimaI Journal for Parasitology, 1971, Vol. 1, pp. 287-296. Pergamon Press. Printed in Great Britain

TRICHINELLOSIS OF ANIMALS IN CHUKOTKA, USSR: A GENERAL REVIEW N. P. LUKASHENKO, EL Martsinovsky

A. G. VOL’FSON, V. A. ISTOMIN and V. YN. CHERNOV

Institute of Medical Parasitology and Tropical Medicine; Chukotsk inter-regional for agricultural production, Chukotka, U.S.S.R.

office

(Received 14 July 1970) Abstract LUKASHENKO N. P., VOL’FSONA. G., ISTOMIN V. A. and CHERNOVV. YN., 1971. Trichinellosis of animals in Chukotka, USSR: A general review. International Journal for Parasitology, 1:

287-296. During an examination, for trichinellosis, of 1489 mammals of 12 different species, in the territory of Chukotka National district (regions of Anadyr’, Bering, Iul’tin, Chaun and Chukotka) and in the region of North-Even of klagadan province, Tr~~h~ella larvae were detected in 236 (16.4%) of these animals from 6 of the species: in 109 (44.8%) of the blue poIar foxes kept in cages, in 12 (15.8%) of the silver-black foxes kept in cages, in 84 (18.2%) of the white polar foxes, in 17 (17.5 %) of the common foxes, in 13 (12.1 ‘A) of the dogs and in the one European bear examined. Trichinella larvae were not found in 190 marine mammals examined: 178 ringed seals, 7 whales, 4 walruses, and 1 bearded seal, nor in the 8 Siberian squirrels and 159 domestic pigs examined. The high incidence of Trichinella infection amongst blue polar foxes and silver-black foxes on fur-animal farms in Chukotka, where the food ration of these animals is predominately the flesh of marine mammals (walruses and other pinnipeds), suggests that marine mammals may constitute one of the sources of infection to caged animals. In Chukotka, as in other regions of the Extreme North and North-East, the circulation of trichinae in nature may occur between two ecologically different groups of animals: terrestial and marine mammals. A wide distribution of trichinellosis among animals in nature, or kept in cages and among dogs in Chukotka National district and in the NorthEven region of Magadan province provides a constant threat of infection to man. Thus the flesh and sub-products of potential hosts of trichinae ~inclu~ng dogs, fur animals, European and polar bears, marine mammals, etc.) should undergo thorough trichinelloscopy examination before being consumed by man. The flesh of sea mammals should be examined for trichinellosis before being used as food for animals; the presence of trichinae in it requires its sterilization. INDEX KEY WORDS: Trichinelia spirals larvae; trichinellosis: bution: fox; dog; bear; seal; walrus; whale; squirrel; pig. INTRODUCTION

AND

PREVIOUS

USSR; Chukotka;

distri-

WORK

the last twenty years much data has accumulated on the large scale distribution of trichinellosis in animals and on the incidence of this disease in man in the extreme north of Eurasia and North America. The first report, of Danish workers, Thorborg, Tulinius and Roth (1948), on the outbreak of trichinellosis among the inhabitants of Greenland, due to the consumption of meat from marine mammals, favoured a more intensive study of this problem in Arctic regions. One of the co-workers of this report, Roth (1949), detected Trichinellu larvae in the bearded seal (Erignatus bar&us) for the first time; the flesh of this animal, on being consumed by man, was the source of a trichinellosis outbreak among the inhabitants of Greenland. Later, Brandly and Rausch (1950) detected Tric~i~e~lu larvae in beluga (~~Z~~~~~pte~ Zeucas), caught near the shores of Alaska. At approximately the same time, and again later, muscle trichinae were detected in walruses (Odobenus rosmarus) caught near the coast of Greenland (Roth, 1950?; Roth & Madsen, 1956; Kuitunen, 1954); in a stretch between Greenland and the Spitzbergen Islands (Thorshaug & Rosted, 1956); in the Bering Sea DURING

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near the shores of Alaska (Fay, 1960); and also in ringed seals (Phoca hispi&), inhabiting the seas round Greenland (Roth, 1950) and Alaska (Rausch, Babero, Rausch & Schiller, 1956). Cameron (1960) reported on the finding of trichinellosis in walruses, polar bears (Ursus maritimus) and common foxes in a region of Arctic Canada. A number of workers have also reported cases of trichinellosis in man and animals in Soviet Arctic regions. Koryazhnov (1946) described, for the first time, a case of natural Trichinella infection in a young polar bear from the Kara Sea. Later Kozhemyakin (1959) reported a case of trichinellosis in a young polar bear from Rudolph Land Island. Ozeretskovskaya & Uspenskij (1957) decribed a trichinellosis outbreak in man (three polar explorers) in the Arctic region, after they had eaten the meat of a polar bear on Bennet Island in the East-Siberian Sea. TrichineZZalarvae were detected in the muscles of this bear. Brusilovskij (1957) described a mass infection of people with trichinellosis in the Extreme North regions. The disease had also set in after they had consumed the meat of a polar bear. On microscopic examination, 137 Trichinella larvae were found in 24 sections of muscles from a bear’s paw. Britov (1962) recorded, for the first time, trichinellosis cases among marine mammals of the order of Pinnipedia, which inhabited the waters of Soviet Arctic regions. When examining 210 seals (species not indicated) in Arkhangel’sk, trichinellosis was diagnosed in 5 of the animals. Most probably these seals pertained to the species of Histiophoca groenlandica. In a region of Obdor tundra on the Yamal Peninsula, Lukanshenko & Brzheskij (1963) detected trichinae in 35 (12.9 %) of the 270 polar foxes (Alopex Zagopus) that they examined and in 9 (6%) of the 150 Siberian ermines (Mustela erminea) examined. Somewhat later Luzhkov (1964) also diagnosed trichinellosis in polar foxes in this region. In the zones of Arctic tundra and forest-tundra of Krasnoyarsk territory, Lukashenko & Brzheskij (1962) detected trichinellosis in 42 wild animals of 5 species: in 16 out of 180 Siberian ermines, in 5 out of 39 Siberian weasels (Mustela nivalis), in 12 out of 125 sables (Martes zibellina), in 4 out of 15 common foxes (Vulpes vulpes), in 2 out of 15 polar foxes, in 1 out of 5 wolverines (GuZo gulo) and in a single wolf examined (Canis lupus). In the northern regions of the far east USSR, trichinellosis was recorded in mammals considerably earlier than in the abovementioned Arctic regions. As far back as 19 15 Gryuner (19 15) detected TrichineZZalarvae in rats (Ratus ratus) in Petropavlovsk on Kamchatka. Of 33 rats examined, 3 were infected with trichinae. Moreover, 1 common fox, 3 polar foxes and 1 European bear (Ursus arctos) perished in captivity from trichinellosis. These animals were fed with rats trapped in Petropavlovsk. Petrov (1941) described, for the first time, a Trichinella infection of blue polar foxes on the Komandor Islands and-in several other regions of the far east. In Sakhalin, trichinellosis was recorded in Norwegian rats in 1948 by Krotov (1959). On the Chukotka peninsula, trichinellosis in animals was recorded a comparatively short while ago. Ovsyukova (1961) detected Trichinella larvae for the first time in Siberian Squirrels (Sciurus vulgaris) in Chukotka. Then Kozlov, Ovsyukova & Radkevich (1963) also detected trichinellosis in Chukotka: in 18 out of 43 dogs examined, in 32 out of 38 blue polar foxes (from a fur-animal farm in Enurmino settlement), in 8 out of 56 silver-black foxes (from fur-animal farms in the settlements of Anadyr’ and Enurmino), in 8 out of 74 white polar foxes and in 2 out of 32 common foxes examined. The dogs examined were obtained from the settlements of Anadyr’ Enurmino and Markovo whilst the white polar foxes and common foxes came

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from the environs of these settlements. Later, Ovsyukova (1965) published summarized results of her observations in the above-mentioned Chukotka regions. According to her data, trichinellosis was detected in 244 out of 419 dogs, in 197 out of 350 silver-black foxes, in 32 out of 48 blue polar foxes, in 23 out of 202 white polar foxes, in 2 out of 12 wolves, in 11 out of 19 European bears, in one out of 19 polar bears, in 2 out of 24 Siberian squirrels, in 2 out of 41 house mice, in one out of 33 Siberian ermines, in 10 out of 56 minks (from a fur-animal state farm) and in the only 2 wolverines examined. The author believed that the main source of infection to animals was the flesh of marine animals. However, attempts made by Ovsyukova (1963) to detect trichinellosis in 64 ringed seals, 56 bearded seals and 61 whales (species of whales not indicated by the author), caught in the waters of the Chukotka Sea, were in all cases unsuccessful. In contrast to the findings of Ovsyukova, positive results which did detect trichinellosis in Pinnipedia were obtained by Kozlov (1966). He found Trichinellu larvae in one walrus on examining the muscles of 144 animals (60 walruses, 70 ringed seals and 14 bearded seals) caught near Enurmino settlement on the northern shore of the Chukotka peninsula.* In this settlement, too, (as was recorded above) trichinellosis in animals on a fur-animal farm had been recorded somewhat earlier. On the basis of his observations, Kozlov emphasised again his earlier suggestion that the infection of caged animals on fur-animal farms occurred through consumption of the flesh of marine mammals. Nadtochij, Tsimbalyuk & Surkova (1966) made a study of trichinellosis in murine rodents in Chukotka and detected Trichinellu larvae in 2 out of the 13 long-tailed squirrels (Citellus undulutus) and in 1 out of the 3 voles (Cletrionomys rutilus) that were examined. The ground squirrels and voles were trapped in Wellen settlement. In the opinion of these authors, the sources of infection to rodents were either the carcasses of infected dogs or the remnants of flesh, left on shores after hunting, of Trichinellu-infected marine animals. Thus the above workers were of a single opinion: that in the infection of fur animals kept in cages, and of dogs, rodents, and other terrestrial mammals in Chukotka, a certain role could be played by the flesh and remnants of the carcasses of marine mammals, infected with Trichinellu larvae. Moreover, the data published in the literature on the infection of marine mammals with Trichinellu larvae gave a sound basis to the belief that these animals were amongst the most important sources of trichinellosis infection in man in the far northern regions, where the population widely consumes the meat of marine animals, A unfortunate example of this is the outbreak of trichinellosis in Greenland, mentioned above, which occurred as a result of the consumption of seal meat. More than 300 persons fell ill, showing serious clinical symptoms of the disease, and 33 deaths were recorded. In the light of the above data, the importance of carrying out purposeful studies on trichinellosis in various species of terrestrial and marine mammals in Chukotka and other regions of the far north clearly became evident. The results of long term studies on trichinellosis in various species of mammals in Chukotka, including marine mammals, are set forth in the present paper. Amongst domestic animals, dogs and pigs were also examined for trichinellosis. MATERIALS

AND

METHODS

Studies of trichinellosis were carried out during the years 1960-1968. In all, muscle samples from 1439 animals, representing 12 species, were examined for trichinae. These comprised 97 common foxes, 460 white polar foxes, 243 caged blue polar foxes, 77 caged * A descriptionof the results of histologicalfindingsof Trichinella larvae in the meat of a walrusis given in the report of Kozlov & Berezantsev(1968). I.J.P.1/3-F

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siIver-black foxes, 8 common squirrels, 1 European bear, 107 domestic dogs, 259 domestic pigs, 178 ringed seals, 7 whales, 1 walrus and 1 bearded seal. The fur animals (silver-black foxes and blue polar foxes) were kept in cages on furanimal farms in Anadyr’ city (collective farm), in the settlements of Wel’kal’, NovoChaplino, Konergino, Ingoum and Lorino. Of the 259 pigs examined, 230 were from Anadyr’ city and 29 from the settlements of Bilibino and Lavrentiya. The common foxes and white polar foxes were shot or trapped in the main hunting regions of Chukotka National district (namely regions of Bering, Iul’tin, Anadyr’, Chukotka and Chaun) and in the North-Even region of Magadan province. The squirrels were obtained near Markovo settlement and the European bear from the environs of Bilibino settlement. In settlements along the shores of the Arctic Sea and the Pacific Ocean, muscle samples were taken from carcasses of marine animals with the purpose of detecting Trichinella larvae. Thus the seal carcasses were examined in the settlements of Wel’kal’, Konergino and Lorino, the whale carcasses in Konergino settlement, the walrus carcass in Krestovoe settlement and the bearded seal carcass in Lorino settlement. Samples of diaphragmatic peduncles, masticatory, intercostal and extremities muscles, tongue etc., were taken for examination from all animals. During the first years, muscle samples were examined only by compression glass-slide method, but during the last 3 yr an additional method was used: artificial digestion of muscle samples. As a rule the latter method was used when studying muscle samples from Pinnipedia. The digestion of muscles tissues was carried out by using artificial gastric juice (1% of IX1 and O-7% of commercial pepsin) in accordance with the procedure used by us earlier (Lukashenko, 1958, 1962). INVESTIGATION

RESULTS

The overall results of examination, for Trichinell~ larvae, of muscle samples from various animals are shown in Table 1. The data in Table 1 show that trichinellosis was detected in 6 out of the 12 species of animal examined, namely the bIue polar foxes, silver-black foxes, white polar foxes, common foxes, European bears and domestic dogs. The highest infection rate was detected in animals kept in cages, namely the blue polar foxes and silver-black foxes, in which it reached 44.8 per cent and 15.5 per cent respectively. A high rate of infection was afso found in white polar foxes, common foxes and dogs: 18.2, 17.5 and 12.1 per cent respectively; thus the differences between the infection rates of polar foxes, common foxes and dogs were insignificant. Trichinae were detected in the one European bear examined. Trichinellosis was not diagnosed in sea mammals (ringed seals, walrus, bearded seal and whales), nor in squirrels nor in domestic pigs. DISCUSSION

An analysis of the results of our investigations and of information available in the literature enables us to make certain speculations regarding the sources of trichinellosis infection in animals in Chukotka and regarding the circulation routes of trichinae in nature. Firstly let us examine the sources of infection to fur animals kept in cages. Blue polar foxes as well as silver-black foxes on fur-animal farms (Anadyr’, Wel’kal’, Novo-Chaplino,

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TRICHINELLOSIS IN CHUKOTKA, USSR

TABLE~-TOTAL RESULTS OF

IZXAMINATION FOR TRICHINELLOSJS OF AMMALS IN CHUKOTKA,

USSR During the years Total number Animal species Examined

1963-1964 Examined

1. Blue polar fox 243 kept in cages (Alopex alopex) 2. Silver-black fox 77 kept in cages 3. White polar fox 460 (Alopex lagopus) 4. Common fox 97 ( Vulpes m&es) 5. Domestic dog 107 (Canis familiaris) 6. European bear 1 (Urus arctos) 7. Siberian squirrel 8 (Sciurus vulgaris) 8. Ringed seal 178 (Phoca hispiaiz) 9. Whale 7 10. Walrus 1 (Odobenus rosmarus) 11. Beardedseal 1 (Erignatus barbatur) 12. Domestic pig 259 Total

1439

Infected (“/,I

Examined

Infected (%I

Examined Infected (%I

(8.3 k)

(18+‘)

0

3

-

417

43

-1

(19.;;)

(2.3 i) 7

89

23

73

1

(17.91;)

(17*51?$ 11 (12.1%) 1 0

Infected (%I

(52.6;)

(3:;)

74 (16.21;) -

Examined

171

60

12

(15.5;)

1967-1968

1965-1966

(18.1;) -

-

0

-

-

2

(26.4 4) -

-

0

(5.4;) 1

-

157

8

0

0

19

0

0

-

-

0 0

-

-

-

-

1

0

0

-

-

-

-

1

0

0

37

0

70

0

152

0

236 (16*4’%)

137

16

370

26

932

194

7

Note: According to the archival data of the district veterinary bacteriological laboratory of the years of 1950-1960 the trichinelloscopic method was used in Anadyr’ to examine 316 pigs. Not in a single case were any Trichinella larvae found.

Konergino, Ingoun and Lorino) were fed mainly on the flesh of marine mammals (ringed seals, walruses, bearded seals, killer whales and belugas), with visceral organs of reindeer, and partly with fish. The feeding of carcasses of free-living polar foxes and common foxes to farm, fur animals was not usually practised. Rodents could not get into the food of animals due to the maintenance of the latter in specially equipped cages with elevated floors. If the possibility of feeding carcasses of wild animals to caged animals is excluded, then the infection of the latter could get in only through the consumption of flesh from marine mammals since it is hardly probable that the infection of farm, fur animals could take place through consumption of slaughter-house wastes of reindeer or of fish. The negative results of our searches for trichinellosis in ringed seals, whales, walruses and bearded seals may be partly explained by the small number of potential hosts of trichinae examined by us, such as one walrus and one bearded seal. The case of trichinellosis detected by Kozlov (1966) in a walrus, caught near Enurmino,

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as well as the discovery of a high infection rate among animals kept in cages (with the knowledge that the flesh of marine mammals features highly in their diet) lead us to believe that marine mammals constitute one of the possible sources of trichinellosis infection to farm, fur animals. It must be kept in mind that even one Trichinellu-infected walrus or seal may serve as a source of infection to hundreds of fur animals, or even more. The possibility of blue polar foxes and silver-black foxes being infected after eating carcasses of fur animals from the wild or kept in cages is not excluded. This source of infection must particularly be taken into account in areas of wide distribution of trichinellossis among wild, fur animals--the carcasses of which are frequently used as food for caged animals (Lukashenko & Brzheskij, 1959). A real source of infection to blue polar foxes and silver-black foxes could be the meat of European bears which is sometimes fed to these animals. As to the sources and routes of infection of marine mammals, this question is still debatable at present. In the opinion of Madsen (1961), the routes of infection of beluga remain unexplained as this large mammal from the order of Cetacea is particularly a fish-eater. Vibe (1950), for the first time, expressed a view on the possibility of infection of marine mammals through benthic invertebrates, particularly Gammarus and other crustaceans, which make up a significant part of the nutrition of walruses, bearded seals, narwhals and others. The infection of Gammarus according to this same author and other investigators (Abs 8z Schmidt, 1954; Rausch et al., 1956) may occur from the infected carcasses of terrestrial mammals which have somehow gained the sea. The above workers (Rausch et al., 1956; Madsen, 1961, 1962; and others) point out that the walruses are animals of prey and not infrequently prey on seals, which could be infected with trichinellosis. More frequent cases of trichinae in walruses than in other species of Pinnipedia would be explained by the above, Moreover, Madsen (1961) suggests the possibility of infection of walruses and other mammals through the consumption of Tricinellu-infected carcasses of dogs and other terrestrial mammals which have, in some way, gained the sea. The above arguments may to some extent be accepted as convincing, although they are based on speculative conclusions and thus require experimental confirmation. Some workers (Vibe, 1950; Merkushev, 1960, 1963; Britov, 1962, 1966) have expressed the idea that birds may play a certain role in the infection of marine-mammals by consuming the carcasses of Trichinella-infected animals and then discharging trichinae with their droppings into the sea. This is less probable as a route of infection of marine animals as in these environmental conditions (outside the hosts’ organism) trichinae perish quite quickly. The routes of transmission of T. spiralis among terrestrial carnivorous mammals can be explained more easily. In Chukotka territory, as well as in other regions of the far north, the circulation of trichinae among carnivores is performed mainly by smaller and weaker animals being devoured by larger and stronger ones. Besides these cases of prey, a significant role in the transmission of infection is played by the consumption of the carcasses of carnivores trapped by hunters, particularly when it is remembered that carcasses may remain well preserved for a long time in tundra conditions. The role of cannibalism in the circulation of trichinae in nature is also not excluded, cannibalism being prevalent in arctic and subarctic regions. Periodic outbreaks of rabies and other epizootics have a certain significance in the

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distribution of trichinellosis among animals such as polar foxes, common foxes and wolves (Lukashenko, 1962?; Lukashenko & Brzheskij, 1962). The possibility is not excluded of wild animals, as well as caged animals, being infected to the same extent as bears (European or polar) through consumption of the flesh of Trichinellu-infected marine mammals. This is particularly probable in areas of hunting on Pennipedia, the flesh of which is sometimes consumed as additional food by fur animals in nature. One must take into account a possibility of wild carnivores (particularly wolves and foxes) becoming infected through feeding on Trichinella-infected carcasses of dogs or of their fellow animals, since the flesh of these is not infrequently fed by hunters to other, more valuable and stronger dogs, for example hounds and draught dogs. The role of rodents

When analysing the sources of infection of wild carnivores of the families Canidae and Mustelidae and the circulation routes of trichinae in Chukotka territory, one cannot underestimate the role of murine rodents. The role of this prolific group of mammals in the distribution of trichinae is evident: they form the greater part of the food ration of fur animals and for some carnivores (e.g. polar and common foxes, ermines) they serve as a main source of nutrition. The question which remains is: how often are these rodents infected with trichinellosis in natural conditions ? The data available in the literature show only rare cases of trichinae detected in field rodents. Thus, for example, among 6589 murine rodents of 18 species examined by us in Western Siberia (Barabin forest-steppe) trichinellosis was diagnosed only in a single field mouse (out of 512 examined) while among 493 animals of 6 species trapped in the same places trichinellosis was recorded in 90 animals (18.2 per cent) of all 6 species (Lukashenko, 1961, 1962). A low infection rate of murine rodents was also noted by Rausch and his co-workers (1956) in Alaska. Here squirrels were an exception as their infection intensity reached 4 per cent. As has been already noted, trichinellosis in rodents has been recorded in single cases in Chukotka: in a single Siberian squirrel (Ovsyukova, 1961), in 1 narrow-craned vole and in 2 long-tailed ground squirrels (Nadtochij et al., 1966). The comparative rarity of cases detecting trichinellosis in murine rodents may be explained by the specific character of their feeding habits as the overwhelming majority of this group of mammals feeds mainly on plants. As regards the sources of infection of murine rodents, we are inclined to think that the main and permanent sources of infection to rodents in natural conditions are the carcasses of TrichineZZu-infected carnivores including dogs. Here cannibalism may play a widely distributed role. Moreover, man himself can become an indirect transmitter of infection from carnivores to rodents. An example of this may be the use of carcasses of fur animals by hunters as bait for trapping polar and common foxes, wolves and other animals. In such cases an infected carcass of one animal may serve as a source of infection not only to the trapped animals but also, and to a greater extent, to murine rodents. If one takes into account the fact that murine rodents are the main source of nutrition of fur animals, and even allowing for the fact that infection of rodents is very rare, it would

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appear that rodents may play a role, far from unimportant, in the infection of carnivores and certainly participate in the circulation of the infection.

wild

The role of insectivores

The role of insectivores in the transmission of trichinae in nature is not excluded. Thus, in 1960, in Novosibirsk province we detected Trichinella larvae in 3 (1.2 per cent) shrews (1 Sorex minutus and 2 S. araneus) out of 238 examined (Lukashenko, 1960, 1961). Karpinski & Kaminska (1948) and Belyaeva (1957) reported that trichinae were detected in insectivores on the territory of Polish and Soviet Belovezh National Park. Proceeding from the elementary relationships of insectivores, particularly the representatives of the genus Sorex, which to a certain extent are animals of prey, one may suppose that the infection occurs through consumption of Trichinella-infected carcasses of small rodents and carnivores, although the possibility of infection of insectivores through cadavereating insects is not excluded. The insects here are considered as short-term reservoir hosts and as an additional link in the transmission of the infection from carcasses to carnivores, omnivores and insectivores in natural foci (Merkushev, 1960). As regards the sources of infection recorded by us in white polar foxes, common foxes and a bear, we must note that infection of the first two species of animals could be a result of devouring weaker brother animals or murine rodents on the one hand and of feeding on carcasses of infected animals on the other. The infection of a bear could occur mainly by devouring a number of other animals of prey, as this beast is unrivalled in Chukotka. The possibility of infection of polar and common foxes as well as of a bear, through consumption of the meat of marine mammals is not excluded, but this source of infection to wild animals apparently does not play a significant role, because terrestrial animals of prey have little chance of feeding on the flesh of Pinnipedia and whales or their remnants. Circulation in nature

In the light of an analysis of the circulation routes of trichinae from natural foci to sinantropic ones, the determination of the sources of Trichinella infection recorded by us in dogs (in 13 out of 107) is of interest. Taking into account the specific character of nutrition of dogs in the severe conditions of Chukotka, it can be concluded that their infection occurred either by devouring their Trichinella-infected fellow animals (when the flesh of dogs’ carcasses was administered to them) or, by analogy with fur animals, by feeding on the carcasses of polar and common foxes and other animals and also by hunting and devouring murine rodents. Moreover one should take into account a real possibility of infection of dogs through the flesh of walruses and other Pinnipedia, particularly in the coastal regions and on fur-animal farms where dogs receive a sufficient quantity of flesh from marine animals to cause infection. In its turn, a dog infected with Trichinella larvae may serve as a source of infection to terrestrial mammals from the orders of Carnivora, Rodentia, Insectivora and Artiodactyla (domestic pig) as well as marine mammals from the order of Pinnipedia and Cetacea. In the first case, the dog may become a victim of large carnivores (bear, wolf and lynx) or its fellow-animals, and its carcass may be eaten by terrestrial animals of the above orders. In the second case, a Trichinella-infected dog may become a source of infection of marine animals provided that its carcass gets down to the sea and is eaten either directly by pinnipeds of prey, or by potential mediators in infection transmission, marine invertebrates. A wide distribution of trichinellosis among animals of Chukotka indicates a constant threat of infection to man.

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A certain source of infection is thus likely to be the meat of marine mammals frequently consumed by the populations of the coastal regions of Magadan province which includes the Chukotka National district. The above data illustrate the diversity of sources and routes of infection of trichinellosis in Chukotka and, apparently, in other regions of the far north where the circulation of trichinae in nature may occur between two ecologically different groups of animals: terrestrial mammals and marine mammals. Thus the natural foci in coastal regions (in the basins of the Arctic Sea and the Pacific Ocean) differ in this respect from the foci of a “continental” ecological system, in which the transmission of trichinellosis is only possible between terrestrial animals. Acknowledgements-The assistance of Dr Z. I. Rybakova in making this material available is gratefully acknowledged. We should also like to express our gratitude to Dr A. D. Kashinsky who kindly checked this manuscript and translated it into English.

REFERENCES Aas 0. & SCHMIDTH. W. 1954. Wie inhzieren sich arktische Tiere mit Trichinen; vorkiufige Mitteilung. Zeitschrif fur die Gesamte Innere Medizin und ihre Grenzgebiete 9: 758-760. BELYAEVA M. JA. 1957. Trichinellez dikikh zhivotnykh BSSR. Byulleten’ Nauchno- Technicheskoi Inforrnatsii Vsesoyuznogo Instuta Gel’mbttologii im. K.I. Skryabina 1: 4-5. BRANDLYP. J. & RAUSCH R. 1950. A preliminary note on trichinosis investigations in Alaska. Arctic 3: 105-107. BRITOV V. A. 1961. 0 roli ryb i rakoobraznykh v peredache trikhinelleza morskim mlekopitaiushchim. Zoologicheskii Zhurnal41: 776-777. Barrov V. A. 1966. 0 prirodnoi i sinantropnoi ochagovosti trikhinelleza. Voprosy prirodnoi ochagovosti bolesnei. Alma-Ata. 9-l 1. BRUSILOVSKU T. V. 1967. Gruppovoe zabolevanie trikhinellezom na krainom severe. Meditsinskaya Parazitologiya i Parazitarnye Bolezni 7: 161-165. CAMERONT. W. M. 1960. Trichinosis in Canada. Wiadomosci Parazytologicnze 6: 304. CAMERONT. W. M. 1962. Trichinellosis in Canada. Proceedings of the 1st International Conference on Trichinellosis. Warsaw, September 1960. pp. 76-79. FAY F. H. 1960. Carnivorous walrus and some arctic zoonoses. Arctic 13: 111-122. GRUNERS. A. 1915. Trikhinellez dikikh zverei soderzhimykh v nevole. Archiv veterinarnykh nauk 7: 745-752 KARPINSKIJ. J. & KAMINsKAL. 1948. Przyczynek do ekologii Trichinella spiralis Owen i innych endopasozylow drobuych ssakow Bialowieskiego Parku Narodowego. Annales Universitatis Mariae CurieSklodowska 3: 427-437. KOZHEMYAKINN. G. 1959. K voprosu o trikhinelloze belykh medvedei. Sbomik Rabot. Leningradskogo Veterinarnogo Instituta 16: 76-79. KOZLOV D. P. 1966. Trikhinellez u morzhei v Sovetskoi Arktike. Materialy k nauchnym konferentsiiam vsesoiuznogo obshchestva gel’mintologov. December 1968.1: 131-133. KOZLOVD. P. & BEREZANT~EV Ju.A. 1968. Obnaruzhenie trikhinelleza u morzha na territorii Sovetskogo Soiuza. Trudy Gel’mintologicheskoi Laboratorii. ANSSSR. Hogi deiatel’n. i ochered. zadachi 19: 86-89. KOZLOV D. P., OVSYUKOVAN. I. & RADKEVICHN. P. 1963. K poznaniu gelmintofauny promyslovykh mlekopitaishchich i sobak Chukotskogo poluostrova. Sb. rzbot po gelminthol. posviaschcehn 85- let. akad. K. I. Skryabina. 66-70. KORYAZHNOV V. P. 1946. Trikhinellez u belogo medvedia. Veterinariya 12: 18-19. KROTOV A. I. 1959. Gelmintofauna pozvonochnykh na ostrove Sakhaline. Raboty po gelminthologii. lzd. MSH SSSR. 1: 98-105. KLJIT~JNENE E. 1954. Walrus meat as a source of trichinellosis in Eskimos. Canadian Journal of Public Health 45: 3cLOO. LUKA~HENKON. P. 1958. K izucheniiu antigennych svoistv gelmintoantigenov iz trikhinell. Meditsinskaya Parasitologiya i Parazitarnye Bolezni 2: 82-86. LUKASHENKON. P. 1960. K poznaniiu prirodnykh ochagov trikhinelleza v svete ekologicheskogo analiza. Wiadomosci Parazytologicnze 6: 313-315. LUKASH~NKON. P. 1961. K ekologicheskomu analizu prirodnych ochagov trikhinelleza. Vtoraia respub. mezhved. nauch. -pract. Konf. poparazitol. iprirodnoochagov. zabolev. g. Tallin. December 1961. 107-109. LUKA~HENKON. P. 1962a. 0 lokalizatsii lichinok Trichinella spiralis. Acta Veterinaria Academiae Scientiarum Hungaricae 12: 269278.

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N. P. LUKASHENKO,A. G. VOL’FSON,V. A. ISTOMINand V. YN. CHERNOV

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1971

LUKA~HENKON. P. 1962b. Natural foci of trichinellosis in the light of an ecological analysis. Proceedings of the 1st International Conference on Trichinellosis. Warsaw. September 1960. 149-151. LUKASHENKO N. P. and BRZHE~KIJW. W. 1959. K poznaniiu prirodnych ochagov trikhinelleza v Barabinskoi lesostepi Novosibirskoi oblast. Meditsinskuyu Paruzitologiya i Puruziturnye Bolenzi 28: 415418. LUKASHENKON. P. & BRZHE~KIJW. W. 1962. Trichinellosis in wild animals in Siberia, Arctic and Far East USSR. Wiadomosci Parazytologicnze 8: 586-597. LUZHKOV A. D. 1964. Gel’mintozy golubykh pestsov. Krolikovodstvo i Zverovodstvo 12: 21-29. MADSEN H. 1961. The distribution of Trichinella spiralis in sledge dogs and wild mammals in Greenland, under a global aspect. A monographic study. Meddelelser om Gronlund 159: 124 pp. MADSEN H. 1962. On trichinae in wild-living carnivores. Proceedings of the 1st International Conference on Trichinellosis. Warsaw, September 1960. 87-93. MERKUSHEVA. V. 1960a. 0 roli ptits v tsirkulatsii Trichinellu spiralis v prirode. Zoologicheskii Zhurnal39: 161-164. MERKUSCHEVA. V. 1960b. 0 roli nasekomykh v rasprostranenii trikhinelleza. Wiudomosci Puruzytologicnze 6: 319-320. MERKUSHEVA. V. 196oC. Rol’ ptits v tsirculatsii Trichinellu spirulis v prirode. Wiudomosci Parazytologicnze 6: 161-164. MERKUSHEVA. V. 1963. 0 trikhinelleze v Sovetskoi Arktike. Wiudomosci Puruzytologicnze 9: 493-495. NADTOCHIJE. V., TSIMBALYUKA. K. & SURKOVA V. S. 1966. Rasprostranenie Trichinella spiralis i Echinococcus multilocularis u gryzunov na Dal’nem Vostoke. Meditsinskuya Paruzitologiya i Paraziturnye Bolenzi 6: 733-734. OVSYUKOVAN. I. 1961. Sluchai obnaruzheniia trikhinelleza u belki na Chukotskom poluostrove. Meditsinskuyu Purazitologiya i Parazitarnye Bolezni 2: 226. OVSYUKOVA N. I. 1963. K izucheniiu gelminthofauny mlekopitaius shchikh Chukotskogo poluostrova. Trudy Vsesoyuznogo Znstituta Gel’mintologii im K.I. Skryabina 10: 13-15. OVSYUK&A N. i. 196% Rasprostranenie trikhinelleza sredi zhivotnykh Chukotskogo poluostrova. Muteriuly k nuuchnym konferentsiiam vsesoiuznogo obshchestva gel’mintologov. December 1965. 2: 178-182. OZERETSKOVSKAYA N. N. & USPENSKIJS. M. 1967. Gruppovoe zarazhenie trikhinellezom ot miasa belogo medvedia v sovetskoi arktike. Meditsinskuvu Puruzitologiyu i Puruziturnye Belezni 2: 152-157. PETROVA. M. 1941. Glistnye boleznipushnykh zverei. 227 pages. RAUSCH R. 1962. Trichinellesis in the Arctic. Proceedings of the 1st International Conference on Trichinellosis. Warsaw, September 1960.80-86. RAUSCH R., BABEROB. B., RAUSCII R. V. & SCHILLERE. L. 1956. Studies on the helminth fauna of Alaska. XXVII. The occurrence of larvae of Trichinella spirulis in Alaskan mammals. Journal of Parasitology 42: 259-271. ROTH H. 1949. Trichinosis in arctic animals. Nature 163: 805-806. (Reprinted in full in Canadian Journal of Comparative Medicine 13: 227-228). ROTH H. 1950a. Nouvelles experiences sur la trichinose, avec considCrations spkiales sur son existence dans les rtgions arctiques. Bulletin de L’Office International des &pizooties 34: 197-220. ROTH H. 1950b. Trikhinosen in Grenland. Grenlundske Selskabs Aarsskrift 57-68. ROTH H. & MADSEN H. 1956. Die Trichinose in GrGnlands, abschliessender Bericht der Jahre 1948-1953. Proceedings of the 14th International Congress on Zoology. Copenhagen. 1953. 10: 340-341. THORBORGN. B., TULINIUSS. & ROTH H. 1948. Trichinosis in Greenland. Actu Pathologica et Microbiologicu Scandinuvica 25: 778-794. THORSHAUGK. & ROSTEDA. F. 1956. Researches into the prevalence of trichinosis in animals in arctic and antarctic waters. Nordisk Veterinaermedicin 8: 115-129. VIBE C. 1950. The marine mammals, and the marine fauna, of the Thule district (north-west Greenland) with observations on the conditions in 193941. Meddelelser om Grmdand 150: l-116.