Molecular identification of natural hybrids between Trichinella nativa and Trichinella T6 provides evidence of gene flow and ongoing genetic divergence.

To date, there are no data available on the population genetics of Trichinella due to the lack of genetic markers and the difficulty of working with such small parasites. In the Arctic region of North America and along the Rocky Mountains, there exist two genotypes of Trichinella, Trichinella nativa and Trichinella T6, respectively, which are well differentiated by biochemical and molecular characters. However, both are resistant to freezing, show other common biological characters (e.g. low or no infectivity to rodents and swine) and produce fertile F1 offspring upon interbreeding. To data, these two genotypes have been considered allopatric. In this study, we detected both genotypes in wolves of the same wolf packs in Alaska, suggesting sympatry. A single GTT trinucleotide present in the ITS-2 sequence of T. nativa but not in Trichinella T6 was used as a genetic marker to study gene flow for this character in both a murine infection model and in larvae from naturally-infected Alaskan wolves. Only F1 larvae originating from a cross between T. nativa male and Trichinella T6 female were able to produce F2 offspring. Larvae (F1) originating from a cross between Trichinella T6 male and T. nativa female were not reproductively viable. As expected, all F1 larvae showed a heterozygote pattern for the GTT character upon heteroduplex analysis; however, within the F2 population, the number of observed heterozygotes (n=52) was substantially higher than expected (n=39.08), as supported by the F(is) index, and was not in the Hardy-Weinberg equilibrium. Larvae from two of the 16 Trichinella positive Alaskan wolves, showed the Trichinella T6 pattern or the T. nativa/Trichinella T6 hybrid pattern. Our data demonstrate that T. nativa and Trichinella T6 live in sympatry at least in Alaskan wolves, where T. nativa occurs more frequently (69%) than Trichinella T6 (31%). One explanation for this phenomenon is that glacial periods may have caused a geographical relocation, colonisation and independent evolution of T. nativa within the Rocky Mountains, resulting in a bifurcation of the freeze-resistant genotype. Additional studies will be required to test this hypothesis.

Serologic survey for Toxoplasma gondii in lynx from interior Alaska.

Two hundred fifty-five lynx (Felis lynx) carcasses were collected from trappers in Interior Alaska (USA). Serosanguinous fluids were collected from the chest cavity of each carcass. These fluids were tested for evidence of exposure to Toxoplasma gondii by means of a modified agglutination test using formalin fixed tachyzoites and mercaptoethanol. Thirty-nine of the samples had titers greater than or equal to the threshold (> or = 25). Antibody prevalence differed between areas, and was directly related to age of the host.

Serologic survey for canine coronavirus in wolves from Alaska.

Wolves (Canis lupus) were captured in three areas of Interior Alaska (USA). Four hundred twenty-five sera were tested for evidence of exposure to canine coronavirus by means of an indirect fluorescent antibody procedure. Serum antibody prevalence averaged 70% (167/240) during the spring collection period and 25% (46/185) during the autumn collection period. Prevalence was 0% (0/42) in the autumn pup cohort (age 4-5 mo), and 60% (58/97) in the spring pup cohort (age 9-10 mo). Prevalence was lowest in the Eastern Interior study area. A statistical model indicates that prevalence increased slightly each year in all three study areas. These results indicate that transmission occurs primarily during the winter months, antibody decay is quite rapid, and reexposure during the summer is rare.

Serologic survey for Toxoplasma gondii in selected wildlife species from Alaska.

Blood was collected from selected wildlife species in specific areas of Alaska (USA) during 1976-96. A modified agglutination test was used to test sera for evidence of exposure to Toxoplasma gondii. Serum antibody prevalence was 43% (62 positive of 143 tested) for black bears (Ursus americanus), 9% (11/125) for wolves (Canis lupus), 7% (22/319) for Dall sheep (Ovis dalli), 6% (14/241) for caribou (Rangifer tarandus), 1% (3/240) for moose (Alces alces), and 1% (2/241) for bison (Bison bison). A predictive model was developed to determine the effect of sex, age, location, and year of collection on antibody prevalence for each species. Prevalence was higher in older black bears, caribou, and wolves. For black bears, prevalence was highest in the southeast region of the state. For caribou, prevalence was lowest on the Alaska Peninsula.

Trichinella sp. in wolves from interior Alaska.

Tongue samples were collected from 148 wolf (Canis lupus) carcasses during 1993 and 1994 near Fairbanks (Alaska, USA). A standard peptic digestion procedure was used to detect Trichinella sp. larvae. Larvae were found in 54 of 148 (36%) samples. There was no significant difference in sex-specific prevalence. Prevalence was significantly related to age. There was no relationship between the number of larvae/g of host tissue and the age or sex of the host. Trichinella spp. infection may cause illness in individual wolves. However, there was no indication the parasite had any impact on the population.

Serologic survey for phocid herpesvirus-1 and -2 in marine mammals from Alaska and Russia.

Blood samples were collected from 1,042 marine mammals off the coast of Alaska (USA) and Russia during the period 1978 to 1994. Eight species of pinnipeds were represented. Sera were tested for presence of neutralizing antibodies to both the PB84 isolate of phocid herpesvirus-1 (PhHV-1) and the 7848/Han90 strain of phocid herpesvirus-2 (PhHV-2). Species-specific antibody prevalences ranged from 22% to 77% for PhHV-1 and 11% to 50% for PhHV-2. Species-specific antibody prevalences for PhHV-1 were greater than or equal to prevalences for PhHV-2. For both viruses and each host species, differences in antibody prevalences were not related to: (1) sex, (2) location of capture, or (3) year of collection. Antibody prevalence of PhHV-1 in walruses (Odobenus rosmarus) could be quantitatively predicted as a function of age. These two viruses have distinct biological properties and based on current data the epizootiology of the two viruses is different, as well. No evidence of herpesvirus-induced mortality has been detected in areas included in this survey. Based on results of this survey, neither PhHV-1 nor PhHV-2 are considered significant mortality factors in mammals which inhabit the marine environment off the coast of Alaska or Russia.

Serologic survey for Trichinella spp. in grizzly bears from Alaska.

Blood was collected from 878 grizzly bears (Ursus arctos) in seven geographic areas of Alaska from 1973 to 1987. An enzyme-linked immunosorbent assay procedure was used to test sera for evidence of exposure to Trichinella spp. Serum antibody prevalence ranged from 5% (10 positive of 196 tested) in the Southern Region of the state to 83% (355 of 430 tested) in the Northern Region. These major discrepancies may be a result of differing food habits of bears in the major geographic areas. Prevalence was higher in older age cohorts. Neither year-of-collection nor sex had a significant effect on prevalence.

Serologic survey for Toxoplasma gondii in grizzly bears from Alaska.

Blood samples were collected from 892 grizzly bears (Ursus arctos) in Alaska (USA) from 1973 to 1987. Sera were tested for evidence of exposure to Toxoplasma gondii by means of the modified agglutination test. Two hundred twenty sera (25%) had titers > or = 25, the minimum threshold titer. Six hundred seventy-two sera (75%) had titers < 25. Antibody prevalence ranged from 9% (18 positive of 196 tested) in southern areas to 37% (162 of 433 tested) in northern areas. There was no readily apparent explanation for these discrepancies in location-specific prevalence.

Antibody responses to Psoroptes sp. mites in Dall sheep (Ovis dalli).

We determined that antibody responses to Psoroptes sp. mites were not present in 403 of 407 sera samples collected opportunistically from 1979 through 1991 from Dall sheep (Ovis dalli) from five locations in Alaska, USA (Eastern Arctic, n = 61; Central Arctic, n = 15; Western Interior, n = 122; Central Interior, n = 63; Eastern Interior, n = 146). Test values for four samples exceeded the positive cutoff value for the immunoassay, but exposure to mites could not be confirmed since the 95% confidence interval for true prevalence ranged from 0 to 2.3%. Therefore, we concluded that these were probably false positive results. Our analysis, coupled with the lack of previous reports of mites or lesions in Dall sheep or other Alaskan ungulates, provided indirect evidence that Psoroptes sp. are not enzootic in Dall sheep in Alaska. In contrast, Psoroptes sp. have been reported in bighorn sheep (Ovis canadensis) and other wild ungulate populations from southern Canada to Mexico. These findings are compatible with the hypothesis that Psoroptes sp. were introduced into North America with imported domestic sheep and were not introduced by ancestral wild sheep.

Serologic survey of Toxoplasma gondii in grizzly bears (Ursus arctos) and black bears (Ursus americanus), from Alaska, 1988 to 1991.

We tested 644 serum samples from 480 grizzly bears and 40 black bears from Alaska (USA), collected between 1988 and 1991, for Toxoplasma gondii antibodies, using a commercially available latex agglutination test (LAT). A titer > or = 64 was considered positive. Serum antibody prevalence for T. gondii in grizzly bears (Ursus arctos) was 18% (87 of 480). Prevalence ranged from 9% (seven of 77) on Kodiak Island to 28% (15 of 54) in northern Alaska. Prevalence was directly correlated to age. No grizzly bears < 2-year-old had T. gondii antibody. High antibody titers were found mainly in grizzly bears captured north of the Arctic Circle. Antibody prevalence in black bears (Ursus americanus) from Interior Alaska was 15% (six of 40), similar to the prevalence in grizzly bears from the same area (13%; five of 40).

Prevalence of Trichinella nativa in lynx (Felis lynx) from Alaska, 1988-1993.

Lynx (Felis lynx) carcasses were collected during the 1989 to 1990 through 1992 to 1993 trapping seasons in Alaska (USA). Seven areas were represented. Tongue samples were removed from 1,065 carcasses. Specimens were examined for the presence of Trichinella nativa larvae by means of enzymatic digestion. Overall prevalence was 21%. Both prevalence and number of larvae per gram of host tissue were directly related to age of the host. Age-specific prevalence ranged from 4% for kittens up to 59% for lynx 5 yr of age and older. For infected lynx, intensity ranged from 0.27 larvae per gram of host tissue for kittens up to 2.35 larvae per gram for lynx 3 yr of age and older. Location-specific prevalence ranged from 19% to 27%. Year-specific prevalence ranged from 13% to 26%. Prevalence in both males and females was 21%.

Experimental Brucella suis biovar 4 infection in a moose.

A moose (Alces alces gigas) was inoculated with Brucella suis biovar 4 to better understand the effects of brucellosis in this species. Serum antibody titers increased rapidly and peaked within 21 to 56 days. Fever, leukocytosis, recumbency, anorexia and depression were observed starting 42 days post inoculation. Brucella suis biovar 4 was isolated from blood, lymph nodes, liver and spleen.

Serologic survey for Actinobacillus capsulatus in free-ranging snowshoe hares (Lepus americanus) from Alaska and Alberta.

A plate agglutination method was developed to test sera from free-ranging snowshoe hares (Lepus americanus) captured in Alaska (USA) or Alberta (Canada) for antibody against Actinobacillus capsulatus. Antiserum against A. capsulatus was prepared in a domestic rabbit. A concentrated suspension of formalin-killed A. capsulatus was prepared for use as an antigen. Serum antibody prevalence for hares was 98 of 239 (41%) in Alaska and 51 of 111 (46%) in Alberta. Prevalence in Alaska peaked in 1981 corresponding to a peak in hare population density. Seasonal prevalence peaked in May in Alaska. Prevalence at one capture site in Alaska was significantly higher than at four other sites. There was no difference in sex-specific prevalence for either Alaska or Alberta.

Factors influencing the potential establishment of the winter tick (Dermacentor albipictus) in Alaska.

The winter tick (Dermacentor albipictus) is not known to occur in Alaska. Survival and development of free-living (i.e., non-host-associated) stages of the tick were studied at three sites in central and southern Alaska. Female ticks survived, oviposited, and eggs hatched at all sites. Hatch success was low at one site where summer temperatures were low. Results suggest that establishment of winter ticks in Alaska following accidental translocation is possible, but several factors would affect such establishment.

Serum antibody prevalence of parainfluenza 3 virus in a free-ranging bison (Bison bison) herd from Alaska.

Serum antibody prevalence of parainfluenza 3 virus in the free-ranging Delta bison (Bison bison) herd which is found near Delta Junction, Alaska (USA), increased from 0% to 100% during the period 1977 to 1984. Domestic cattle are hypothesized as the source for the infection. There has been no clinical disease or decrease in productivity in this bison herd since establishment of the infection.

Serologic survey for Mycoplasma ovipneumoniae in free-ranging dall sheep (Ovis dalli) in Alaska.

Indirect hemagglutination tests on sera from 251 Dall sheep (Ovis dalli) from interior Alaska collected during the period 1979 to 1987 revealed no evidence of exposure to Mycoplasma ovipneumoniae. Apparently, this potentially fatal disease agent has not been introduced into free-ranging Dall sheep populations. In the interest of continued health of such Dall sheep, strict enforcement of domestic animal health regulations and prudent land use practices are clearly indicated.

Serologic survey for infectious canine hepatitis virus in grizzly bears (Ursus arctos) from Alaska, 1973 to 1987.

Serum antibody prevalence of infectious canine hepatitis virus was 12% (90 of 725) for grizzly bears (Ursus arctos) from Alaska (USA) during the period 1973 to 1987. Prevalence was highest on Kodiak Island at 29% (37 of 127). Prevalence of exposure at individual collection areas did not change significantly over time. There were no significant sex-specific differences in prevalence. Prevalence was directly related to age, but it was 0% for bears less than 2-yr-old. Young bears which are exposed to the virus may develop clinical disease and die as a result of the infection. This disease may be a factor affecting grizzly bear population dynamics.

Actinobacillosis in free-ranging snowshoe hares (Lepus americanus) from Alaska.

Actinobacillus capsulatus was isolated from lung, liver, and/or spleen tissue of three snowshoe hares (Lepus americanus) in Alaska. This is the first report of the isolation of this bacterium from free-ranging hares. Actinobacillus capsulatus may have a negative impact on the population density of hares.

Serologic survey for selected microbial pathogens of wolves in Alaska, 1975-1982.

Serum samples were collected from 116 wolves which were captured in southcentral Alaska during 1975 through 1982. Antibodies to the following infectious disease agents were found: infectious canine hepatitis virus-72 of 87 (81%), canine parvovirus type 2-0 of 55 (0%) through 1979 and 10 of 32 (31%) after 1979, Francisella tularensis-16 of 67 (25%), canine distemper virus-10 of 83 (12%), Coxiella burnetti-5 of 95 (5%), rabies virus-1 of 88 (1%), Brucella spp.-1 of 67 (1%), Leptospira interrogans-1 of 82 (1%). Apparently rabies, brucellosis, and leptospirosis were rare and had little effect on the wolf population. Conversely, the other five infections were comparatively common and may have had a negative impact on the health of specific individual wolves, but did not appear to influence the health of the population.