Serosurvey of selected zoonotic agents in polar bears (Ursus maritimus).

Between 1982 and 1999 blood samples were collected from 500 polar bears (Ursus maritimus) captured in the Beaufort and Chukchi seas, to determine the seroprevalence of Brucella species, Toxoplasma gondii, and Trichinella species infections. The bears were classified into four age groups, cubs, yearlings, subadults and adults. Brucella and Toxoplasma antibodies were detected by agglutination (a buffered acidified card antigen and rapid automated presumptive test for brucellosis and a commercial latex agglutination test for toxoplasmosis); an ELISA was used to detect Trichinella antibodies. The overall seroprevalence of Brucella species was 5 per cent, and subadults and yearlings were 2-62 times (95 per cent confidence interval 1.02 to 6.82) more likely to be seropositive for Brucella species than adults and their cubs. The antibody prevalence for Toxoplasma gondii was 6 per cent, and for Trichinella species 55.6 per cent. The prevalence of antibodies to Trichinella species increased with age (P<0.001).

Rabies and canine distemper in an arctic fox population in Alaska.

Two oil field workers were attacked by a rabid arctic fox (Alopex lagopus) in the Prudhoe Bay oil field (Alaska, USA) prompting officials to reduce the local fox population. Ninety-nine foxes were killed during winter 1994. We tested foxes for prevalence of rabies and canine distemper. Exposure to rabies was detected in five of 99 foxes. Of the five, only one fox had rabies virus in neural tissue as determined by the direct fluorescent antibody test. The other four foxes had been exposed to rabies, but had apparently produced antibodies and did not have an active infection. No evidence of canine distemper was detected as determined by the absence of distemper antibodies in serum and distemper virus in neural tissue.

Serological evidence of morbillivirus infection in polar bears (Ursus maritimus) from Alaska and Russia.

One-hundred-and-ninety-one samples of blood serum collected from 186 polar bears (Ursus maritimus) between 1987 and 1992 were analysed for morbillivirus antibodies. The samples were collected in the Bering, Chukchi and East Siberian seas. Sixty-eight samples (35.6 per cent) had morbillivirus antibody titres > 5; the percentage of positive samples ranged from 26.2 to 46.2 per cent from year to year. The proportions of adults, sub-adults and cubs which were seropositive were 43.9, 35.7 and 37.9 per cent respectively. Some seropositive dams had seronegative young and some that were seronegative had seropositive young. One litter of two cubs, in which the dam was seronegative, had one seropositive and one seronegative cub. Seropositive bears occurred in all the areas from which the samples were collected but there was a significantly greater incidence in the bears sampled in Russia. The high prevalence of seropositive bears over the period suggests that the bear morbillivirus is endemic in these regions of the Arctic, but its source is unknown.

Evaluation of the safety of two attenuated oral rabies vaccines, SAG1 and SAG2, in six Arctic mammals.

The safety of two attenuated oral rabies vaccines was evaluated in mink and in five species of rodents which occur in the Arctic. A 0.03 ml sample of liquid vaccine was installed directly into the mouth of voles and lemmings and 0.1 ml into the mouth of Arctic ground squirrels and mink. Animals were euthanized at 36 and 46 days postexposure; brain tissue was analyzed by FAT and serum by RFFIT. No rabies deaths occurred in 47 animals tested. Four animals representing three rodent species seroconverted, the highest titer being 0.5 IU ml-1. The absence of rabies virus in brain tissue indicates the safety of these vaccines in these species. The replacement of arginine with glutamic acid at position 333 reduces the pathogenicity of these vaccines, thereby presumably preventing the deleterious effect of viral entry into CNS neurons.

Survey of fox trappers in northern Alaska for rabies antibody.

The purpose of this research was to determine whether trappers in northern Alaska acquired immunity to rabies virus from non-bite exposures while trapping and skinning arctic foxes (Alopex lagopus). In coastal Alaska recurring epizootics presumably provide trappers ample opportunity for contact with rabid animals. Serum neutralization analyses of blood samples collected from 26 individuals were conducted. All but three had negative rabies neutralizing antibody levels (< 0.05 I.U./ml). Two of these had previously received rabies vaccine but one individual who had trapped for about 47 years with an estimated harvest of over 3000 foxes and who had never received pre- or post-exposure rabies vaccination had a rabies serum neutralizing antibody concentration of 2.30 I.U./ml. This represents the first report of an unvaccinated person acquiring rabies virus antibody with a titre above the 0.5 I.U./ml level considered acceptable by the World Health Organization.

Oral rabies vaccination of arctic foxes (Alopex lagopus) with an attenuated vaccine.

Arctic foxes were immunized with the SAG1 oral rabies vaccine. The effectiveness was determined by the serological response and by the survival to a challenge dose of rabies virus from an Alaskan fox. Vaccine virus was isolated from saliva 1 h after the liquid vaccine was placed directly into the mouth but not subsequently (tested up to 1 week postvaccination). Two weeks after vaccination, protective antibody levels were present in all foxes and all vaccinated foxes survived challenge at 9 weeks postvaccination. At 26 weeks postvaccination (17 weeks postchallenge) all but one fox had detectable antibody levels. Neural tissue harvested from surviving foxes was negative for rabies virus by direct immunofluorescent testing. One of the foxes vaccinated with SAG1 seroconverted and survived challenge even though the titre of the vaccine used was almost 4 logs less than that used to vaccinate the other foxes. These results suggest that the avirulent SAG1 oral rabies vaccine is very effective in protecting arctic foxes.

Immunization of arctic foxes (Alopex lagopus) with oral rabies vaccine.

Arctic foxes (Alopex lagopus) were successfully immunized against rabies using an orally-administered, liquid SAD-BHK21 live virus vaccine in a sausage bait. Immunization was determined by serologic response and by resistance to challenge with an arctic rabies virus strain. Virus was not shed in saliva following oral vaccination, indicating that arctic foxes would not infect other foxes after ingesting this vaccine. High antibody levels were present in all experimental foxes 2 wk following initial vaccination. A booster vaccination at 56 wk induced a significant serologic response within 1 wk, suggesting an anamnestic response but titers began to decline within 8 wk in most foxes. Foxes were observed for 16 mo following the challenge and exhibited no symptoms of rabies. The SAD-BHK21 rabies vaccine in a sausage bait system has a strong potential for vaccinating wild populations of arctic fox.

Plasma marking of arctic foxes with iophenoxic acid.

Six arctic foxes (Alopex lagopus) were marked with iophenoxic acid (IA), a substance which elevates concentrations of protein-bound iodine in blood plasma. Buccal absorption of IA was determined by placing 20 mg IA dissolved in 100% ethyl alcohol on the tongue. Blood samples collected from 1 to 36 wk following exposure showed that all foxes were marked already at 1 wk and continued until 13 wk; two foxes were still marked at 36 wk. Clearance rates for iodine varied with initial dose response, and those foxes with high 1-wk iodine concentrations excreted iodine more rapidly than those with lower initial concentrations; by 13-wk excretion rates were similar.

A long-range implantable heart rate transmitter for free-ranging animals.

The design and operating characteristics of a heart rate transmitter designed for a wild grizzly bear (Ursus arctos) study is described. The rigid capsule is durable and is easily implanted in the field. The transmitter can be regularly monitored at 4-5 km and has a life expectancy of about 1 year in bears which experience winter torpor, and thus reduced heart rate, for about 7 months in northern Alaska.