New findings concerning the spread of natural foci of infection in the transpolar region of eastern Siberia]

New materials are presented on the presence of the foci of anthropozoonozes in the Extreme North. For the first time there was established the existence in the subarctic tundra of the Taimyr peninsula of the arbovirus foci of the tick-borne encephalitis complex. A virus of the tick-borne encephalitis complex was isolated in 1973 from the gamasida ticks Haemogamasus ambulans Thorel. and Hirstionyssus isabellinus Oudms. and the nests of the Siberian lemming Lemmus lemmus L. This pointed to the existence in the Transpolar region of the foci or arboviruses in the nest-hole biocenoses of the lemmings outside the bird colonies. Cultures of tularemia bacilli (which proved the etiology of the epizootic among the lemmings observed in 1973 and also the presence of the lemming natural foci of tularemia and their combination with the arbovirus foci) were isolated from the lemmings at the same territory. The results of serological examination of the local population and of the animals pointed to the circulation in the Transpolar region of the causative agents of leptospirosis, toxoplasmosis, Q-fever and of the Asian tick-borne rickettsiosis.     

Isolation of the causative agent of tularemia from Siberian lemmings in Eastern Taymyr]

The authors present the results of bacteriological and serological study for tularemia of 498 lemmings caught in Taimyr. Positive results were revealed in 4 out of 98 sera examined in the indirect hemagglutination test. In carrying out 67 biological tests on albino mice there were isolated for the first time in the Soviet Union 6 cultures of the causative agent of tularemia from the spleen of lemmings. By morphological, cultural and virulent properties the cultures obtained failed to differ from those isolated in other regions of the Soviet Union, and, consequently, we referred to the holoarctic race. Thus, it was established by the authors (both serologically and bacteriologically) that there existed tundra foci of tularemia.     

Preservation of the causative agent of tularemia in the external environment in eastern Taimyr]

Strains of the causative agent of tularemia were for the first time isolated by the authors from the objects of the external environment in the tundra zone of Eastern Taimir; this indicates a possibility of preservation of the microbe under conditions of the extreme north.     

Ectoparasites and phoresants of the root vole (Microtus oeconomus Pall.) in the Polesye

Drainage melioration in the Polesye resulted in a sharp increase in the number of tundra vole (Microtus oeconomus Pall.) which quickly included into the parasitocenosis of the drained land. There were found 26 parasitic and nonparasitic species of Gamasoidea, 3 species of Ixodidae and 2 species of Trombiculidae, 10 species of Aphaniptera, 3 species of Anoplura but there was found no species specific only for the tundra vole. All found parasites occur on many hosts. This explains wide parasitic links of the tundra vole with other homothermic animals which especially extensive with the bank vole and it may have important consequences for epizootiology of tularemia and tick-borne encephalitis.     

Heat increment of feeding and its thermoregulatory benefit in the muskrat (Ondatra zibethicus)

The calorigenic effect of feeding and its potential benefit in defraying thermoregulatory costs and attenuating immersion hypothermia of adult muskrats were investigated. A single session of feeding on aquatic vegetation was sufficient to raise the metabolic rate of muskrats for a period of at least 5 h. The peak postprandial rate of oxygen consumption averaged 1.42 times the level established for fasted animals, and the heat increment of feeding accounted for about 40% of the metabolizable energy intake of muskrats. There was no evidence of a postprandial rise in oxygen consumption of muskrats that entered water at 18–19°C after feeding. In aquatic trials, average and minimum steady-state oxygen consumption rates of fed muskrats were similar to, or even lower than values recorded from fasted animals, implying substitution of heat increment of feeding for thermoregulatory heat production. Our data did not support the hypothesis that heat increment of feeding retards body cooling in water. Net body temperature decline in water was actually higher in fed animals than in fasted controls. However, since previously fed muskrats also entered water at an elevated body temperature, the final body temperature (at 30 min immersion) was similar in all groups. These findings suggest that metabolic heat generated incidental to preimmersion feeding could provide a thermoregulatory benefit to muskrats by reducing the need for active thermogenesis in water.     

Habitat occupancy by riparian muskrats reveals tolerance to urbanization and invasive vegetation

Wildlife communities are being altered by rapid environmental change including habitat loss and fragmentation, urbanization, and spread of invasive species. To predict consequences of these anthropogenic changes to landscapes, it is necessary to identify not only species that are negatively affected, but also species that are unaffected or even thrive. We used occupancy modeling to examine the spatial distribution of muskrats (Ondatra zibethicus) in riparian habitat within an agricultural region of east-central Illinois from 2007 to 2008. We examined whether site occupancy was related to local habitat conditions and anthropogenic landscape alterations including urbanization and dominance of invasive reed canary grass (Phalaris arundinacea). We sampled 90 study sites (200-m stream segments) for occupancy by muskrats based on presence of tracks, scat, and feeding sign. Per-survey detection probability was 0.79 (SE = 0.04) in 2007 and 0.76 (SE = 0.04) in 2008. Detection was related positively to Julian date and negatively to abundance of woody debris and emergent rocks. Site occupancy by muskrats was 0.59 (SE = 0.09) in 2007 and 0.69 (SE = 0.06) in 2008, a year with above-average precipitation. Occupancy was related positively to urban land cover surrounding sites, which could reflect higher baseflows and reduced risk from predation and trapping in urban areas. Occupancy was unrelated to site dominance by invasive reed canary grass, but muskrats occurred more often at larger, deeper streams and those with greater bank heights and less sandy bank soils. Turnover between years was driven by stream size and water availability. Muskrats exhibited tolerance to key aspects of environmental change, and muskrats might even be urban adapters when occupying riparian habitat that remains adequately connected in urbanizing landscapes. © 2011 The Wildlife Society.     

Tyzzer's disease in muskrats: re-examination of specimens of hemorrhagic disease collected by Paul Errington

Organisms typical of those seen in Tyzzer's disease of muskrats (Ondatra zibethica) were found in tissue sections from two muskrats found dead in Iowa in 1947 by Paul Errington. These findings support further the hypothesis that Errington's and Tyzzer's diseases of muskrats are a single entity.     

Modeling the date of leaf appearance in low-arctic tundra

One of the reported changes of arctic ecosystems in response to warming climate is the advance of the leaf appearance in spring. Such phenological changes play a role in the structural changes within tundra ecosystem communities. Recently, we developed a model that estimates the leaf appearance date for deciduous trees in taiga. We apply this model to the whole low-arctic tundra, and we compare the simulated green-up dates with the green-up dates obtained from satellite observations and to in situ measurements of deciduous shrub leaf appearance. The model, although calibrated for taiga, performs remarkably well in tundra, with root mean square error ranging between 4 and 8 days for most of the tundra region, the same order as in taiga regions. The results seem to indicate that air temperature is the main factor controlling spring leaf phenology in tundra, just as in taiga, although these results do not permit us to reject soil temperature as the main trigger for leaf appearance in tundra. Because our model performs in tundra as well as in taiga, it can be used across the ecotone, and during a northward migration of the species from the taiga to the low-arctic region. The leaf appearance model and the satellite observations reveal that leaf appearance has tended to occur earlier by approximately 10 days both in Alaska since 1975, and in west Siberian tundra since 1965.     

Cross-species transmission of Giardia spp.: inoculation of beavers and muskrats with cysts of human, beaver, mouse, and muskrat origin

Giardia cysts isolated from humans, beavers, mice, and muskrats were tested in cross-species transmission experiments for their ability to infect either beavers or muskrats. Giardia cysts, derived from multiple symptomatic human donors and used for inoculation of beavers or muskrats, were shown to be viable by incorporation of fluorogenic dyes, excystation, and their ability to produce infections in the Mongolian gerbil model. Inoculation of beavers with 5 x 10(5) Giardia lamblia cysts resulted in the infection of 75% of the animals (n = 8), as judged by the presence of fecal cysts or intestinal trophozoites at necropsy. The mean prepatent period was 13.1 days. An infective dose experiment, using 5 x 10(1) to 5 x 10(5) viable G. lamblia cysts collected by fluorescence-activated cell sorting, demonstrated that doses of between, less than 50, and less than 500 viable cysts were required to produce infection in beavers. Scanning electron microscopy of beaver small intestine revealed that attachment of G. lamblia trophozoites produced lesions in the microvillous border. Inoculation of muskrats with G. lamblia cysts produced infections when the dose of cysts was equal to or greater than 1.25 x 10(5). The inoculation of beavers with Giardia ondatrae or Giardia muris cysts did not produce any infection; however, the administration to muskrats of Giardia cysts of beaver origin resulted in the infection of 62% of the animals (n = 8), with a prepatent period of 5 days. Our results demonstrated that beavers and muskrats could be infected with Giardia cysts derived from humans, but only by using large numbers of cysts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cross-species transmission of Giardia spp.: inoculation of beavers and muskrats with cysts of human, beaver, mouse, and muskrat origin.

Giardia cysts isolated from humans, beavers, mice, and muskrats were tested in cross-species transmission experiments for their ability to infect either beavers or muskrats. Giardia cysts, derived from multiple symptomatic human donors and used for inoculation of beavers or muskrats, were shown to be viable by incorporation of fluorogenic dyes, excystation, and their ability to produce infections in the Mongolian gerbil model. Inoculation of beavers with 5 x 10(5) Giardia lamblia cysts resulted in the infection of 75% of the animals (n = 8), as judged by the presence of fecal cysts or intestinal trophozoites at necropsy. The mean prepatent period was 13.1 days. An infective dose experiment, using 5 x 10(1) to 5 x 10(5) viable G. lamblia cysts collected by fluorescence-activated cell sorting, demonstrated that doses of between, less than 50, and less than 500 viable cysts were required to produce infection in beavers. Scanning electron microscopy of beaver small intestine revealed that attachment of G. lamblia trophozoites produced lesions in the microvillous border. Inoculation of muskrats with G. lamblia cysts produced infections when the dose of cysts was equal to or greater than 1.25 x 10(5). The inoculation of beavers with Giardia ondatrae or Giardia muris cysts did not produce any infection; however, the administration to muskrats of Giardia cysts of beaver origin resulted in the infection of 62% of the animals (n = 8), with a prepatent period of 5 days. Our results demonstrated that beavers and muskrats could be infected with Giardia cysts derived from humans, but only by using large numbers of cysts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Seroprevalence study of Francisella tularensis among hunters in Germany

In 2005 and 2006, Francisella tularensis unexpectedly reemerged in western Germany, when several semi-free-living marmosets (Callithrix jacchus) in a research facility died from tularemia and a group of hare hunters became infected. It is believed that hunters may have an elevated risk to be exposed to zoonotic pathogens, including F. tularensis. A previous cross-sectional study of the German population (n=6883) revealed a prevalence of 0.2%. Here, we investigated 286 sera from individuals mainly hunting in districts with emerging tularemia cases (group 1) and 84 sera from a region currently not conspicuous for tularemia (group 2). Methods included standard enzyme-linked immunosorbent assay (ELISA), Western blot analysis and indirect immunofluorescence assay. We found five out of the 286 hunters (1.7%; 95% CI 0.6-4.0%) in group 1 positive with standard ELISA and Western blot, but none in the Berlin area (group 2; 95% CI 0-0.04%). Group 1 showed an elevated risk for hunters to be seropositive for F. tularensis compared with the cross-sectional study (OR=7.7; P<0.001). This indicates a higher prevalence for tularemia in hunters of a suspected endemic region of Germany.     

Prevalence of Giardia spp. in beaver and muskrat populations in northeastern states and Minnesota: detection of intestinal trophozoites at necropsy provides greater sensitivity than detection of cysts in fecal samples.

Surveys of the prevalence of the intestinal protozoan Giardia spp. in animal populations have relied almost exclusively on the detection of cysts in fecal samples. We have determined the prevalence of Giardia spp. in beaver and muskrat populations in four northeastern states and Minnesota by using both the detection of trophozoites in mucosal scrapings from live-trapped animals at necropsy and the detection of cysts in fecal samples collected from kill-trapped animals. In muskrats the prevalence of Giardia infection was 36.6% by cyst detection in fecal samples (n = 790) from kill-trapped animals and 95.9% in live-trapped muskrats when the intestinal contents were analyzed for the presence of trophozoites (n = 219). Similarly, in beavers, Giardia infection was 9.2% by cyst detection in fecal samples (n = 662) from kill-trapped beavers and 13.7% in live-trapped animals examined for the presence of intestinal trophozoites (n = 302). The detection of trophozoites in mucosal scrapings from live-trapped animals consistently yielded a significantly higher prevalence for both muskrats and beavers than did the method based on detection of cysts in the fecal samples. The prevalence of Giardia infection in juvenile and adult live-trapped muskrats was similar (92.5 and 94.4%, respectively), but the prevalence in juvenile live-trapped beavers (23.2%) was significantly greater than that seen in the adult animals (12.6%). No difference in Giardia prevalence on the basis of sex was seen in either animal species. Regional variation, often statistically significant, was seen in the prevalence of Giardia in beavers in the northeastern states and Minnesota, but was not detected for muskrats.     

Hematologic and blood chemistry reference values for free-ranging muskrats (Ondatra zibethicus)

Baseline hematologic and serum chemistry values are used by veterinarians and wildlife biologists to identify abnormally high or low levels of particular blood parameters in a target species. This vital information can assist animal care providers in making informed decisions on the care of wildlife and help to determine diagnoses for certain illnesses. Published blood parameter values are not available for wild-caught muskrats (Ondatra zibethicus). We measured 27 blood parameter values from 29 free-ranging, riparian muskrats caught from June-November 2008 in east-central Illinois, USA, and compared mean values between adults and juveniles. Adult muskrats had higher levels of globulins (F(1,27)=6.394, P ≤ 0.018) and eosinophils (F(1,25)=6.883, P ≤ 0.015) than did juvenile muskrats, possibly because of increased exposure to parasites and allergens over time.     

Response of tundra ecosystem in southwestern Alaska to Younger-Dryas climatic oscillation

Climatic warming during the last glacial–interglacial transition (LGIT) was punctuated by reversals to glacial‐like conditions. Palaeorecords of ecosystem change can help document the geographical extent of these events and improve our understanding of biotic sensitivity to climatic forcing. To reconstruct ecosystem and climatic variations during the LGIT, we analyzed lake sediments from southwestern Alaska for fossil pollen assemblages, biogenic‐silica content (BSiO₂%), and organic‐carbon content (OC%). Betula shrub tundra replaced herb tundra as the dominant vegetation of the region around 13 600 cal BP (cal BP: ¹⁴C calibrated calendar years before present), as inferred from an increase of Betula pollen percentages from << 5% to >> 20% with associated decreases in Cyperaceae, Poaceae, and Artemisia. At c. 13 000 cal BP, a decrease of Betula pollen from 28 to << 5% suggests that shrub tundra reverted to herb tundra. Shrub tundra replaced herb tundra to resume as the dominant vegetation at 11 600 cal BP. Higher OC% and BSiO₂% values suggest more stable soils and higher aquatic productivity during shrub‐tundra periods than during herb‐tundra periods, although pollen changes lagged behind changes in the biogeochemical indicators before c. 13 000 cal BP. Comparison of our palaeoecological data with the ice‐core dδ¹⁸O record from Greenland reveals strikingly similar patterns from the onset through the termination of the Younger Dryas (YD). This similarity supports the hypothesis that, as in the North Atlantic region, pronounced YD climatic oscillations occurred in the North Pacific region. The rapidity and magnitude of ecological changes at the termination of the YD are consistent with greenhouse experiments and historic photographs demonstrating tundra sensitivity to climatic forcing.     

Tularemia in inactive natural foci

The data on the epidemiological and epizootological manifestations of tularemia on the territory of the Ulyanovsk region are presented. The characteristics describing the process of the of Francisella tularensis circulation as well as the environmental objects, most important for the manifestations of tularemia infection, are given.     

Long-term dynamics and prognosis for tularemia and pseudotuberculosis morbidity in the Iaroslavl region

The trends and main factors influencing the fluctuations of the levels of tularemia and pseudotuberculosis morbidity in the Iaroslavl region were revealed by the methods of mathematical statistics (regress analysis, time-series analysis, etc.). Tularemia morbidity was 0.467 +/- 0.216 cases (1950-1997) and pseudotuberculosis morbidity was 0.979 +/- 0.297 cases (1979-1997) per 100,000 of the population. The multiple regression equations permitting the prognostication of tularemia and pseudotuberculosis morbidity in the Iaroslvl region were derived.     

Prevalence of Giardia spp. in beaver and muskrat populations in northeastern states and Minnesota: detection of intestinal trophozoites at necropsy provides greater sensitivity than detection of cysts in fecal samples

Surveys of the prevalence of the intestinal protozoan Giardia spp. in animal populations have relied almost exclusively on the detection of cysts in fecal samples. We have determined the prevalence of Giardia spp. in beaver and muskrat populations in four northeastern states and Minnesota by using both the detection of trophozoites in mucosal scrapings from live-trapped animals at necropsy and the detection of cysts in fecal samples collected from kill-trapped animals. In muskrats the prevalence of Giardia infection was 36.6% by cyst detection in fecal samples (n = 790) from kill-trapped animals and 95.9% in live-trapped muskrats when the intestinal contents were analyzed for the presence of trophozoites (n = 219). Similarly, in beavers, Giardia infection was 9.2% by cyst detection in fecal samples (n = 662) from kill-trapped beavers and 13.7% in live-trapped animals examined for the presence of intestinal trophozoites (n = 302). The detection of trophozoites in mucosal scrapings from live-trapped animals consistently yielded a significantly higher prevalence for both muskrats and beavers than did the method based on detection of cysts in the fecal samples. The prevalence of Giardia infection in juvenile and adult live-trapped muskrats was similar (92.5 and 94.4%, respectively), but the prevalence in juvenile live-trapped beavers (23.2%) was significantly greater than that seen in the adult animals (12.6%). No difference in Giardia prevalence on the basis of sex was seen in either animal species. Regional variation, often statistically significant, was seen in the prevalence of Giardia in beavers in the northeastern states and Minnesota, but was not detected for muskrats.     

Habitat suitability in muskrats: a test of the food limitation hypothesis

Data on habitat selection, overwinter survival, and litter survival rate of muskrats indicate that fitness differs among habitats in marsh environments. We measured nine nutrient-dependent phenotypic variables of muskrats and one independent assessment of forage quality during the ice-free period (May-October) from 1992 to 1994. Data were used to test the hypothesis that differences in food resources limit the demographic performance of muskrats in marginal versus prime habitats (food limitation hypothesis, FLH). None of the null predictions relating habitat quality with reproductive parameters could be rejected statistically. Adult body mass and length were greater in prime habitats, but fat content did not differ, which suggested that the difference was associated with larger structural size of dominant animals in prime habitats. Growth rate of weaned juveniles was not different among habitats, which represented the strongest evidence for rejecting the FLH. Faecal crude protein content, which was used as an index of quality of food ingested, was marginally different between the two most suitable habitats, but the direction of the difference did not support our prediction. Overall, the temporal variation in faecal crude protein content was similar among habitats. We conclude that food is not a key factor limiting the demographic performance of muskrats among habitats during the ice-free season.     

Genetics Reveal the Origin and Timing of a Cryptic Insular Introduction of Muskrats in North America

The muskrat, Ondatra zibethicus, is a semiaquatic rodent native to North America that has become a highly successful invader across Europe, Asia, and South America. It can inflict ecological and economic damage on wetland systems outside of its native range. Anecdotal evidence suggests that, in the early 1900s, a population of muskrats was introduced to the Isles of Shoals archipelago, located within the Gulf of Maine, for the purposes of fur harvest. However, because muskrats are native to the northeastern coast of North America, their presence on the Isles of Shoals could be interpreted as part of the native range of the species, potentially obscuring management planning and biogeographic inferences. To investigate their introduced status and identify a historic source population, muskrats from Appledore Island of the Isles of Shoals, and from the adjacent mainland of Maine and New Hampshire, were compared for mitochondrial cytochrome b sequences and allele frequencies at eight microsatellite loci. Appledore Island muskrats consistently exhibited reduced genetic diversity compared with mainland populations, and displayed signatures of a historic bottleneck. The distribution of mitochondrial haplotypes is suggestive of a New Hampshire source population. The data presented here are consistent with a human-mediated introduction that took place in the early 1900s. This scenario is further supported by the zooarchaeological record and island biogeographic patterns. This is the first genetic study of an introduced muskrat population within US borders and of any island muskrat population, and provides an important contrast with other studies of introduced muskrat populations worldwide.     

Frequent fires in ancient shrub tundra: implications of paleorecords for arctic environmental change

Understanding feedbacks between terrestrial and atmospheric systems is vital for predicting the consequences of global change, particularly in the rapidly changing Arctic. Fire is a key process in this context, but the consequences of altered fire regimes in tundra ecosystems are rarely considered, largely because tundra fires occur infrequently on the modern landscape. We present paleoecological data that indicate frequent tundra fires in northcentral Alaska between 14,000 and 10,000 years ago. Charcoal and pollen from lake sediments reveal that ancient birch-dominated shrub tundra burned as often as modern boreal forests in the region, every 144 years on average (+/- 90 s.d.; n = 44). Although paleoclimate interpretations and data from modern tundra fires suggest that increased burning was aided by low effective moisture, vegetation cover clearly played a critical role in facilitating the paleofires by creating an abundance of fine fuels. These records suggest that greater fire activity will likely accompany temperature-related increases in shrub-dominated tundra predicted for the 21(st) century and beyond. Increased tundra burning will have broad impacts on physical and biological systems as well as on land-atmosphere interactions in the Arctic, including the potential to release stored organic carbon to the atmosphere.