Mass Mortality of Adult Male Subantarctic Fur Seals: Are Alien Mice the Culprits?

Background

Mass mortalities of marine mammals due to infectious agents are increasingly reported. However, in contrast to previous die-offs, which were indiscriminate with respect to sex and age, here we report a land-based mass mortality of Subantarctic fur seals with apparent exclusivity to adult males. An infectious agent with a male-predilection is the most plausible explanation for this die-off. Although pathogens with gender-biased transmission and pathologies are unusual, rodents are known sources of male-biased infectious agents and the invasive Mus musculus house mouse, occurs in seal rookeries.

Methodology/ Principal Findings

Molecular screening for male-biased pathogens in this potential rodent reservoir host revealed the absence of Cardiovirus and Leptospirosis genomes in heart and kidney samples, respectively, but identified a novel Streptococcus species with 30% prevalence in mouse kidneys.

Conclusions/ Significance

Inter-species transmission through environmental contamination with this novel bacterium, whose congenerics display male-bias and have links to infirmity in seals and terrestrial mammals (including humans), highlights the need to further evaluate disease risks posed by alien invasive mice to native species, on this and other islands.     

An assessment of skin temperature gradients in a tropical primate using infrared thermography and subcutaneous implants

Infrared thermography has become a useful tool to assess surface temperatures of animals for thermoregulatory research. However, surface temperatures are an endpoint along the body's core-shell temperature gradient. Skin and fur are the peripheral tissues most exposed to ambient thermal conditions and are known to serve as thermosensors that initiate thermoregulatory responses. Yet relatively little is known about how surface temperatures of wild mammals measured by infrared thermography relate to subcutaneous temperatures. Moreover, this relationship may differ with the degree that fur covers the body. To assess the relationship between temperatures and temperature gradients in peripheral tissues between furred and bare areas, we collected data from wild mantled howling monkeys (Alouatta palliata) in Costa Rica. We used infrared thermography to measure surface temperatures of the furred dorsum and bare facial areas of the body, recorded concurrent subcutaneous temperatures in the dorsum, and measured ambient thermal conditions via a weather station. Temperature gradients through cutaneous tissues (subcutaneous-surface temperature) and surface temperature gradients (surface-ambient temperature) were calculated. Our results indicate that there are differences in temperatures and temperature gradients in furred versus bare areas of mantled howlers. Under natural thermal conditions experienced by wild animals, the bare facial areas were warmer than temperatures in the furred dorsum, and cutaneous temperature gradients in the face were more variable than the dorsum, consistent with these bare areas acting as thermal windows. Cutaneous temperature gradients in the dorsum were more closely linked to subcutaneous temperatures, while facial temperature gradients were more heavily influenced by ambient conditions. These findings indicate that despite the insulative properties of fur, for mantled howling monkeys surface temperatures of furred areas still demonstrate a relationship with subcutaneous temperatures. Given that most mammals possess dense fur, this provides insight for using infrared imaging in thermoregulatory studies of wild animals lacking bare skin.     

Response of Different Antibiotic Resistant Group of Streptococcus pyogenes to Environmental Stresses

Streptococcus species is considered as an important pathogen for human and animals. The antibiotic resistance mechanism in this species is continuously increased. On the other side, the tolerance of environmental stresses play an effective role in the severity of many streptococcal causative disease. In this study we assayed survey on the causative agents of pharyngitis and tonsillitis patients. The predominant causative strain was Streptococcus pyogenes with 93 % isolating ratio frequency. The other pathogenic species were S. agalactia 5.3 % and S. pneumonia 1.7 %. According to the antibiotic resistant test the S. pyogenes isolates were classified into six different groups. A selected strain from each antibiotic resistant group was tested for tolerance of a restrictive environmental factors. The variations of the environmental niches of isolates were in consistence with their antibiotic resistant variation.     

Molecular Detection of Circovirus and Adenovirus in Feces of Fur Seals (<Emphasis Type="Italic">Arctocephalus</Emphasis> spp.)

In some regions, little is known about exposure to viruses in coastal marine mammals. The present study aimed to detect viral RNA or DNA in 23 free-ranging fur seals on the northern coastline of Rio Grande do Sul State, Brazil. Polymerase chain reaction was used to detect nucleic acids of circoviruses, adenoviruses, morbilliviruses, vesiviruses, and coronaviruses in the feces from twenty-one South American fur seals (Arctocephalus australis) and two Subantarctic fur seals (A. tropicalis). Adenovirus DNA fragments were detected in two South American fur seals; nucleotide sequences of these fragments revealed a high degree of similarity to human adenovirus type C. Circovirus DNA fragments were detected in six animals of the same species. Two were phylogenetically similar to the Circovirus genus, whereas the other four nucleotide fragments showed no similarity to any of the known genera within the family Circoviridae. RNA fragments indicating the presence of coronavirus, vesivirus, and morbillivirus were not detected. These findings suggest that adenoviruses and circoviruses are circulating in fur seal populations found along the coast of Rio Grande do Sul State, Brazil.     

Metagenomic Survey of Viral Diversity Obtained from Feces of Subantarctic and South American Fur Seals

The Brazilian South coast seasonally hosts numerous marine species, observed particularly during winter months. Some animals, including fur seals, are found dead or debilitated along the shore and may harbor potential pathogens within their microbiota. In the present study, a metagenomic approach was performed to evaluate the viral diversity in feces of fur seals found deceased along the coast of the state of Rio Grande do Sul. The fecal virome of two fur seal species was characterized: the South American fur seal (Arctocephalus australis) and the Subantarctic fur seal (Arctocephalus tropicalis). Fecal samples from 10 specimens (A. australis, n = 5; A. tropicalis, n = 5) were collected and viral particles were purified, extracted and amplified with a random PCR. The products were sequenced through Ion Torrent and Illumina platforms and assembled reads were submitted to BLASTx searches. Both viromes were dominated by bacteriophages and included a number of potentially novel virus genomes. Sequences of picobirnaviruses, picornaviruses and a hepevirus-like were identified in A. australis. A rotavirus related to group C, a novel member of the Sakobuvirus and a sapovirus very similar to California sea lion sapovirus 1 were found in A. tropicalis. Additionally, sequences of members of the Anelloviridae and Parvoviridae families were detected in both fur seal species. This is the first metagenomic study to screen the fecal virome of fur seals, contributing to a better understanding of the complexity of the viral community present in the intestinal microbiota of these animals.     

Phenotypic and molecular characterisation of <Emphasis Type="Italic">Brucella</Emphasis> isolates from marine mammals

Background  

Bacteria of the genus Brucella are the causative organisms of brucellosis in animals and man. Previous characterisation of Brucella strains originating from marine mammals showed them to be distinct from the terrestrial species and likely to comprise one or more new taxa. Recently two new species comprising Brucella isolates from marine mammals, B. pinnipedialis and B. ceti, were validly published. Here we report on an extensive study of the molecular and phenotypic characteristics of marine mammal Brucella isolates and on how these characteristics relate to the newly described species.     

Alaskan marine mammal tissue archival project

A project to establish an archive of Alaskan marine mammal tissues was conceived in 1987 to be a part of the National Biomonitoring Specimen Bank (NBSB). Protocols and field collection of marine mammals, long-term storage, and analysis are summarized in this paper. Instrumental neutron activation analysis has been used for an initial evaluation of trace element content in samples of northern fur seal (Callorhinus ursinus) from the Pribilof Islands. The findings agree with previously observed trace element levels in northern fur seals. The archived specimens can be used in future studies when comparisons of past and present pollution levels are needed.

     

Streptococcal superantigens and the return of scarlet fever

Streptococcus pyogenes (group A Streptococcus) is a globally disseminated and human-adapted bacterial pathogen that causes a wide range of infections, including scarlet fever. Scarlet fever is a toxin-mediated disease characterized by the formation of an erythematous, sandpaper-like rash that typically occurs in children aged 5 to 15. This infectious disease is caused by toxins called superantigens, a family of highly potent immunomodulators. Although scarlet fever had largely declined in both prevalence and severity since the late 19th century, outbreaks have now reemerged in multiple geographical regions over the past decade. Here, we review recent findings that address the role of superantigens in promoting a fitness advantage for S. pyogenes within human populations and discuss how superantigens may be suitable targets for vaccination strategies.     

Evidence of anthropogenic trauma in marine mammals stranded along the central California coast, 2003–2015

A total of 11,162 stranded marine mammals was admitted to a rehabilitation center on the central California coast between January 2003 and September 2015. Six hundred seventeen animals (6%) had evidence of anthropogenic trauma (AT). California sea lions comprised the majority (83%) of AT cases, particularly by entanglement in marine debris (n = 277) and gunshot injuries (n = 165). Guadalupe fur seals had the highest prevalence of entanglement in marine debris. Cetaceans were primarily affected by boat collisions (n = 19). The highest numbers of overall strandings were recorded in 2009 (n = 1,690) and 2015 (n = 1,666); 2009 also had the highest total number (n = 137) and prevalence (8%) of AT cases. Prevalence of fishing tackle cases increased compared to similar data from 1986 to 1998 while prevalence of gunshot cases decreased, and other causes remained static. Cases of fisheries interactions were further examined and characterized, and when direct fisheries interactions were separated from other causes of AT, fisheries interactions accounted for 50% (n = 310) of all AT cases during the study period. Direct fisheries interactions were the most common type of AT observed among stranded marine mammals in central California. Tracking AT trends is important to further understand possible causes and inform mitigation efforts.     

Olfactory discrimination ability of South African fur seals (Arctocephalus pusillus) for enantiomers

Using a food-rewarded two-choice instrumental conditioning paradigm we assessed the ability of South African fur seals, Arctocephalus pusillus, to discriminate between 12 enantiomeric odor pairs. The results demonstrate that the fur seals as a group were able to discriminate between the optical isomers of carvone, dihydrocarvone, dihydrocarveol, menthol, limonene oxide, α-pinene, fenchone (all p < 0.01), and β-citronellol (p < 0.05), whereas they failed to distinguish between the (+)- and (?)-forms of limonene, isopulegol, rose oxide, and camphor (all p > 0.05). An analysis of odor structure–activity relationships suggests that a combination of molecular structural properties rather than a single molecular feature may be responsible for the discriminability of enantiomeric odor pairs. A comparison between the discrimination performance of the fur seals and that of other species tested previously on the same set of enantiomers (or subsets thereof) suggests that the olfactory discrimination capabilities of this marine mammal are surprisingly well developed and not generally inferior to that of terrestrial mammals such as human subjects and non-human primates. Further, comparisons suggest that neither the relative nor the absolute size of the olfactory bulbs appear to be reliable predictors of between-species differences in olfactory discrimination capabilities. Taken together, the results of the present study support the notion that the sense of smell may play an important and hitherto underestimated role in regulating the behavior of fur seals.     

Telemetry tags increase the costs of swimming in northern fur seals,Callorhinus ursinus

Animal‐borne instruments have become a standard tool for collecting important data from marine mammals. However, few studies have examined whether placement of these data loggers affects the behavior and energetics of individual animals, potentially leading to biasing data. We measured the effect of two types of relatively small data loggers (<1% of animals’ mass and front profile) on the swimming speeds and energy expenditure of four female northern fur seals (Callorhinus ursinus) while swimming at depth. Swim speeds and rates of oxygen consumption were measured as the trained fur seals repeatedly swam an underwater circuit, with or without the tags. We found the placement of either tested tag significantly affected both the behavior and energetics of the fur seals in our study. Diving metabolic rate increased an average of 8.1%–12.3% (depending on tag type) and swim speed decreased an average of 3.0%–6.0% when wearing the tags. The combined changes in velocities and metabolic rates resulted in a 12.0%–19.0% increase in the total energy required by the fur seals to swim a set distance. The demonstrated effects of tags on behavior and energy expenditure may bias data sets from wild animals and potentially incur longer‐term impacts on the studied animals.     

Transmissible cancer in Tasmanian devils: localized lineage replacement and host population response

Tasmanian devil facial tumour disease (DFTD) is a clonally transmissible cancer threatening the Tasmanian devil (Sarcophilus harrisii) with extinction. Live cancer cells are the infectious agent, transmitted to new hosts when individuals bite each other. Over the 18 years since DFTD was first observed, distinct genetic and karyotypic sublineages have evolved. In this longitudinal study, we investigate the associations between tumour karyotype, epidemic patterns and host demographic response to the disease. Reduced host population effects and low DFTD infection rates were associated with high prevalence of tetraploid tumours. Subsequent replacement by a diploid variant of DFTD coincided with a rapid increase in disease prevalence, population decline and reduced mean age of the population. Our results suggest a role for tumour genetics in DFTD transmission dynamics and epidemic outcome. Future research, for this and other highly pathogenic emerging infectious diseases, should focus on understanding the evolution of host and pathogen genotypes, their effects on susceptibility and tolerance to infection, and their implications for designing novel genetic management strategies. This study provides evidence for a rapid localized lineage replacement occurring within a transmissible cancer epidemic and highlights the possibility that distinct DFTD genetic lineages may harbour traits that influence pathogen fitness.     

Inhibitory activity of probiotics <Emphasis Type="Italic">Streptococcus phocae</Emphasis> PI80 and <Emphasis Type="Italic">Enterococcus faecium</Emphasis> MC13 against Vibriosis in shrimp <Emphasis Type="Italic">Penaeus monodon</Emphasis>

Occurrence of widespread epizootics among larval and cultured shrimp has put on viable preventive approaches such as application of probiotics on a high priority in aquaculture. In the present study, four probiotics bacteria were isolated from marine fish and shrimp intestine based on the antagonistic activity and nonpathogenic to the host. The isolates of probiotics strains Streptococcus phocae PI80, Enterococcus faecium MC13, Lactococcus garvieae LC149, B49 and one commercial probiotics (ECOFORCE) were fed to post larvae of Penaeus monodon obtained from two different hatcheries to analyze the growth and protection against Vibrio harveyi and V. parahaemolyticus. Growth of P. monodon post larvae fed with probiotic strain S. phocae PI80 was significantly (P < 0.001) higher when compared with control and other three strains in both experiments. The treatment of post larvae with B49 reduced the growth as well as Specific growth rate. Among the three probiotic strains S. phocae PI80 and E. faecium MC13 have effectively inhibited the pathogens. In experiment I high survival (92%) were observed in S. phocae PI80 treated post larvae when challenged with Vibrio harveyi followed by E. faecium MC13 (84%), B49 (76%) and ECOFORCE (68%) but PI80 did not protect the post larvae in the same experiment when they were exposed to V. parahaemolyticus. The probiotic isolate of MC13 has protected the post larvae against V. parahaemolyticus when compared to other probiotics and control. Similarly in the second experiment feeding of S. phocae enhanced the survival of larvae when challenged with V. harveyi. The laboratory studies proved that bacterial probionts S. phocae and E. faecium isolated from shrimp and brackishwater fish has potential applications for controlling pathogenic vibriosis in shrimp culture.     

The fur of mammals in exposed environments; do crypsis and thermal needs necessarily conflict? The polar bear and marsupial koala compared

The furs of mammals have varied and complex functions. Other than for thermoregulation, fur is involved in physical protection, sensory input, waterproofing and colouration, the latter being important for crypsis or camouflage. Some of these diverse functions potentially conflict. We have investigated how variation in cryptic colouration and thermal features may interact in the coats of mammals and influence potential heat inflows from solar radiation, much of which is outside the visible spectral range. The coats of the polar bear (Ursus maritimus) and the marsupial koala (Phascolarctus cinereus) have insulative similarities but, while they feature cryptic colouration, they are of contrasting colour, i.e. whitish and dark grey. The reflectance of solar radiation by coats was measured across the full solar spectrum using a spectroradiometer. The modulation of incident solar radiation and resultant heat flows in these coats were determined at a range of wind speeds by mounting them on a heat flux transducer/temperature-controlled plate apparatus in a wind tunnel. A lamp with a spectral distribution of radiation similar to the solar spectrum was used as a proxy for the sun. Crypsis by colour matching was apparent within the visible spectrum for the two species, U. maritimus being matched against snow and P. cinereus against Eucalyptus forest foliage. While reflectances across the full solar spectrum differed markedly, that of U. maritimus being 66 % as opposed to 10 % for P. cinereus, the heat influxes from solar radiation reaching the skin were similar. For both coats at low wind speed (1 m s^?1), 19 % of incident solar radiation impacted as heat at the skin surface; at higher wind speed (10 m s^?1) this decreased to approximately 10 %. Ursus maritimus and P. cinereus have high and comparable levels of fur insulation and although the patterns of reflectance and depths of penetrance of solar radiation differ for the coats, the considerable insulation limited the radiant heat reaching the skin. These data suggest that generally, if mammal coats have high insulation then heat flow from solar radiation into an animal is much restricted and the impact of coat colour is negligible. However, comparisons with published data from other species suggest that as fur insulation decreases, colour increasingly influences the heat inflow associated with solar radiation.     

Serologic survey for potential pathogens and assessment of disease risk in Australian fur seals

The introduction of pathogens into populations of animals with no previous exposure to them and, therefore, no immunologic protection, can result in epizootics. Predicting the susceptibility of populations to infectious diseases is crucial for their conservation and management. Australian fur seals (Arctocephalus pusillus doriferus) have a relatively small population size, a restricted range, and form dense aggregations. These factors make this species vulnerable to epizootics of infectious diseases that spread by direct animal-to-animal contact. Blood samples were collected from 125 adult female Australian fur seals between 2007 and 2009 and tested for exposure to selected pathogens. The testing protocol was based on pathogens important to marine mammal health or those significant to public and livestock health. No antibodies were detected to morbilliviruses, influenza A viruses, six Leptospira serovars, Mycobacterium tuberculosis-complex species, or Toxoplasma gondii. Overall antibody prevalence to an unidentified Brucella sp. was 57% but varied significantly (P<0.02) between 2007 (74%) and 2008 (53%). The findings indicate Brucella infection may be enzootic in the Australian fur seal population. Further investigations are required to isolate the bacteria and establish if infection results in morbidity and mortality. Australian fur seals remain vulnerable to the threat of introduced disease and should be managed and monitored accordingly.     

Biopreservation of Sardinella longiceps and Penaeus monodon Using Protective Culture Streptococcus phocae PI 80 Isolated from Marine Shrimp Penaeus indicus

The influence of Streptococcus phocae PI80 on the shelf life of Sardinella longiceps and Penaeus monodon was investigated by measurement of microbial and chemical analysis after appraising the safety of the protective probiotic culture in wistar rat’s model. The results of this safety assessment indicate that oral administration of protective culture does not demonstrate any toxicological effects. Consumption of this LAB strain had no adverse effects on animal’s general health status, hematology, blood biochemistry, histology parameters, or on the incidence of bacterial translocation. The effect of Streptococcus phocae is very evident with the reduction of Listeria monocytogenes, Vibrio parahemolyticus, and coliforms. During storage, a marked decline in total volatile base and peroxide value was observed in protective culture-treated samples than the control. This strain looks promising as a protective culture for the preservation of fish products.     

The use of non destructive biomarkers in the study of marine mammals

Marine mammals have been subject to heavy anthropogenic pressure by direct killing and chemical pollution all over the world. Most studies of contamination and biomarker responses in marine mammals have been conducted using animals killed by hunting out of a total of 12 cetacean species studied, 45 of the specimens were obtained by sacrificing the animal; out of a total of eight pinniped species studied, 40 of the specimens were obtained by killing. The development of a series of non destructive techniques to evaluate biomarker responses and residue levels is recommended for the hazard assessment and conservation of endangered species of marine mammals. Here we review the current status of the non destructive biomarker approach in marine mammals, describing the biological materials available for non destructive tests in stranded brain, liver, blood, skin, subcutaneous blubber, muscle and fur and free ranging animals blood, skin biopsy, fur and faeces and the respective biomarker techniques mixed function oxidase activity and DNA damage in skin biopsy samples; porphyrins in faeces and fur; esterases, porphyrins, clinical biochemical parameter, vitamin A and micronuclei in blood samples. Residue analysis can be carried out in the various biological materials. We also report the results of applying this methodological approach to cetaceans minke whale Balaenoptera acutorostrata, fin whale-- Balaenoptera physalus, beluga whale-- Delphinapterus leucas, short finned pilot whale-- Globicephala macrorhynchus, harbour porpoise -- Phocoena phocoena, Rissos dolphin-- Risso s Grampus griseus, Dall s porpoise-- Phocoenoides dalli dalli, melon headed whale-- Peponocephala electra, bottlenose dolphin -- Tursiops truncatus, striped dolphin-- Stenella coeruleoalba, spinner dolphin-- Stenella longirostris, killer whale-- Orcinus orca and pinnipeds northern fur seal- Callorhinus ursinus, hooded seal-- Cystophora cristata, grey seal-- Halichoerus grypus, harbour seal-- Phoca vitulina, ringed seal-- Phoca hispida, harp seal-- Phoca groenlandica, ribbon seal-- Phoca fasciata, largha seal- Phoca largha, southern sea lion-- Otaria flavescens in field studies for prognostic and diagnostic purposes.     

Demonstration of β-glucan receptors in the skin of aquatic mammals—a preliminary report

Using immunohistochemistry, the study clearly demonstrates three important β-glucan receptors (Ficolin/P35, MBL, Dectin-1; members of the lectin-complement pathway of innate immunity) in the integument of six marine and freshwater aquatic mammals (Northern fur seal, Common seal, Walrus, Coypu, Capybara, Otter), but only weakly in two dolphin species. Most of the non-dolphin mammals exhibited strong reactions, especially with regard to the skin glands (tubular apocrine glands, sebaceous glands), for L-Ficolin/P35 and MBL. Distinct reaction staining could also be observed in the epidermis and the outer epithelial sheath of primary hair follicles. Positive Dectin-1 staining was limited to secretory cells of the apocrine tubular glands, and to peripheral and central cells of sebaceous glands of the seals. The Capybara was the only animal to show a clear Dectin reaction in the epidermis (stratum granulosum). The findings are discussed with regard to the constant and high microbial challenge of the skin in the aquatic medium, and variations in hair density of the animals.     

The use of non destructive biomarkers in the study of marine mammals

Marine mammals have been subject to heavy anthropogenic pressure by direct killing and chemical pollution all over the world. Most studies of contamination and biomarker responses in marine mammals have been conducted using animals killed by hunting out of a total of 12 cetacean species studied, 45 of the specimens were obtained by sacrificing the animal; out of a total of eight pinniped species studied, 40 of the specimens were obtained by killing . The development of a series of non destructive techniques to evaluate biomarker responses and residue levels is recommended for the hazard assessment and conservation of endangered species of marine mammals. Here we review the current status of the non destructive biomarker approach in marine mammals, describing the biological materials available for non destructive tests in stranded brain, liver, blood, skin, subcutaneous blubber, muscle and fur and free ranging animals blood, skin biopsy, fur and faeces and the respective biomarker techniques mixed function oxidase activity and DNA damage in skin biopsy samples; porphyrins in faeces and fur; esterases, porphyrins, clinical biochemical parameter, vitamin A and micronuclei in blood samples . Residue analysis can be carried out in the various biological materials. We also report the results of applying this methodological approach to cetaceans minke whale Balaenoptera acutorostrata, fin whale-- Balaenoptera physalus, beluga whale-- Delphinapterus leucas, short finned pilot whale-- Globicephala macrorhynchus, harbour porpoise -- Phocoena phocoena, Rissos dolphin-- Risso s Grampus griseus, Dall s porpoise-- Phocoenoides dalli dalli, melon headed whale-- Peponocephala electra, bottlenose dolphin -- Tursiops truncatus, striped dolphin-- Stenella coeruleoalba, spinner dolphin-- Stenella longirostris, killer whale-- Orcinus orca and pinnipeds northern fur seal- Callorhinus ursinus, hooded seal-- Cystophora cristata, grey seal-- Halichoerus grypus, harbour seal-- Phoca vitulina, ringed seal-- Phoca hispida, harp seal-- Phoca groenlandica, ribbon seal-- Phoca fasciata, largha seal- Phoca largha, southern sea lion-- Otaria flavescens in field studies for prognostic and diagnostic purposes.     

Trichinellosis of animals in Chukotka, USSR: A general review

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 Magadan province, Trichinella larvae were detected in 236 (16·4%) of these animals from 6 of the species: in 109 (44·8%) of the blue polar 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%) 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 North-Even region of Magadan province provides a constant threat of infection to man. Thus the flesh and sub-products of potential hosts of trichinae (including 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.