Multi-pathogen serological survey of migratory caribou herds: A snapshot in time.

Pathogens can impact host survival, fecundity, and population dynamics even when no obvious disease is observed. Few baseline data on pathogen prevalence and diversity of caribou are available, which hampers our ability to track changes over time and evaluate impacts on caribou health. Archived blood samples collected from ten migratory caribou herds in Canada and two in Greenland were used to test for exposure to pathogens that have the potential to effect population productivity, are zoonotic or are emerging. Relationships between seroprevalence and individual, population, and other health parameters were also examined. For adult caribou, the highest overall seroprevalence was for alphaherpesvirus (49%, n = 722), pestivirus (49%, n = 572) and Neospora caninum (27%, n = 452). Lower seroprevalence was found for parainfluenza virus type 3 (9%, n = 708), Brucella suis (2%, n = 758), and Toxoplasma gondii (2%, n = 706). No animal tested positive for antibodies against West Nile virus (n = 418) or bovine respiratory syncytial virus (n = 417). This extensive multi-pathogen survey of migratory caribou herds provides evidence that caribou are exposed to pathogens that may have impacts on herd health and revealed potential interactions between pathogens as well as geographical differences in pathogen exposure that could be linked to the bio-geographical history of caribou. Caribou are a keystone species and the socio-economic cornerstone of many indigenous cultures across the North. The results from this study highlight the urgent need for a better understanding of pathogen diversity and the impact of pathogens on caribou health.

Pestivirus Infections in Semi-Domesticated Eurasian Tundra Reindeer (Rangifer tarandus tarandus): A Retrospective Cross-Sectional Serological Study in Finnmark County, Norway.

Members of the Pestivirus genus (family Flaviviridae) cause severe and economically important diseases in livestock. Serological studies have revealed the presence of pestiviruses in different cervid species, including wild and semi-domesticated Eurasian tundra reindeer. In this retrospective study, serum samples collected between 2006 and 2008 from 3339 semi-domesticated Eurasian reindeer from Finnmark County, Norway, were tested for anti-pestivirus antibodies using an enzyme linked immunosorbent assay (ELISA) and a subset of these by virus neutralization test (VNT). A seroprevalence of 12.5% was found, varying from 0% to 45% among different herding districts, and 20% in western Finnmark, as compared to 1.7% in eastern Finnmark. Seroprevalence increased with age. Pestivirus-specific RNA was not detected in any of the 225 serum samples tested by real-time RT-PCR. Based on VNT results, using a panel of one bovine viral diarrhea virus (BVDV) strain and two border disease virus (BDV) strains, the virus is most likely a reindeer-specific pestivirus closely related to BDV. A characterization of the causative virus and its pathogenic impact on reindeer populations, as well as its potential to infect other domestic and wild ruminants, should be further investigated.

Recombinant prion protein vaccination of transgenic elk PrP mice and reindeer overcomes self-tolerance and protects mice against chronic wasting disease.

Chronic wasting disease (CWD) is a fatal neurodegenerative disease that affects cervids in North America and now Europe. No effective measures are available to control CWD. We hypothesized that active vaccination with homologous and aggregation-prone recombinant prion protein (PrP) could overcome self-tolerance and induce autoantibody production against the cellular isoform of PrP (PrPC), which would be protective against CWD infection from peripheral routes. Five groups of transgenic mice expressing elk PrP (TgElk) were vaccinated with either the adjuvant CpG alone or one of four recombinant PrP immunogens: deer dimer (Ddi); deer monomer (Dmo); mouse dimer (Mdi); and mouse monomer (Mmo). Mice were then challenged intraperitoneally with elk CWD prions. All vaccinated mice developed ELISA-detectable antibody titers against PrP. Importantly, all four vaccinated groups survived longer than the control group, with the Mmo-immunized group exhibiting 60% prolongation of mean survival time compared with the control group (183 versus 114 days post-inoculation). We tested for prion infection in brain and spleen of all clinically sick mice. Notably, the attack rate was 100% as revealed by positive CWD signals in all tested tissues when assessed with Western blotting, real-time quaking-induced conversion, and immunohistochemistry. Our pilot study in reindeer indicated appreciable humoral immune responses to Mdi and Ddi immunogens, and the post-immune sera from the Ddi-vaccinated reindeer mitigated CWD propagation in a cell culture model (CWD-RK13). Taken together, our study provides very promising vaccine candidates against CWD, but further studies in cervids are required to investigate vaccine efficacy in the natural CWD hosts.

Immune function in arctic mammals: Natural killer (NK) cell-like activity in polar bear, muskox and reindeer.

Natural killer (NK) cells are a vital part of the rapid and non-specific immune defense against invading pathogens and tumor cells. This study evaluated NK cell-like activity by flow cytometry for the first time in three ecologically and culturally important Arctic mammal species: polar bear (Ursus maritimus), muskox (Ovibos moschatus) and reindeer (Rangifer tarandus). NK cell-like activity for all three species was most effective against the mouse lymphoma cell line YAC-1, compared to the human leukemia cell line K562; NK cell response displayed the characteristic increase in cytotoxic activity when the effector:target cell ratio increased. Comparing NK activity between fresh and cryopreserved mouse lymphocytes revealed little to no difference in function, highlighting the applicability of cryopreserving cells in field studies. The evaluation of this important innate immune function in Arctic mammals can contribute to future population health assessments, especially as pollution-induced suppression of immune function may increase infectious disease susceptibility.

Non-invasive determination of the immune physiological state of reindeer (Rangifer tarandus) in the Greater Khingan Mountains, China.

Immunoglobulin and cortisol levels are good indicators of well-being and living status in animals. In this study, the concentrations of fecal immunoglobulins A ([IgAF]), G ([IgGF]), and M ([IgMF]), and cortisol ([cortisolF]) were examined by enzyme-linked immunosorbent assay in reindeer of the Greater Khingan Mountains of Inner Mongolia, China. [IgAF] was significantly higher than [IgGF] and [IgMF], and [IgGF] was significantly higher than [IgMF] (P < 0.05). Both [IgAF] and [IgGF] were higher in the Adult group than in Aged or Infant groups, and higher in the Young than Infant group (P < 0.05). The four age group [IgMF]s were not significantly different (P > 0.05). [IgAF], [IgGF], and [IgMF] in each age group were higher in females than in males, with a significant difference in the Young group (P < 0.05). The Infant group had the highest [cortisolF], and the Adult group the lowest; [cortisolF] was significantly higher in the Infant group than in other age groups (P < 0.05). In each age group, [cortisolF] was higher in females than males, and there were significant differences among the Infant, Young, and Aged groups (P < 0.05). A significant negative correlation was observed between [cortisolF] and [IgAF] and [IgGF] (P > 0.05). Overall physical condition was better in the Adult and Young groups than in the Aged and Infant groups as determined by the comprehensive analysis of fecal Ig levels in the four age groups, with the Infant group the worst.

Filter-paper blood samples for ELISA detection of Brucella antibodies in caribou.

We evaluated blood collected on Nobuto filter-paper (FP) strips for use in detecting Brucella spp. antibodies in caribou. Whole blood (for serum) and blood-saturated FP strips were obtained from 185 killed arctic caribou (Rangifer tarandus groenlandicus). Sample pairs (serum and FP eluates) were simultaneously tested in duplicate using competitive enzyme-linked immunosorbent assay (c-ELISA) and indirect ELISA (i-ELISA) for Brucella spp. Prior work based on isolation of Brucella spp. revealed sensitivity (SE) and specificity (SP) of 100% and 99%, respectively, for both these serum assays in caribou. Infection status of the animals in the current study was unknown but recent sampling had revealed clinical brucellosis and >40% Brucella antibody prevalence in the herd. To assess the performance of FP relative to serum in these assays, serum was used as the putative gold standard. On both assays, the findings for duplicate runs (A and B) were similar. For c-ELISA run A, the FP Brucella prevalence (47%) was lower than serum prevalence (52%), with SE 89% (95% confidence interval [CI]: 82-95%) and SP 99% (97-100%). For i-ELISA run A, serum and FP Brucella prevalence rates were identical (43%), and the SE and SP of FP testing were 100% and 99% (97-100%), respectively. The findings suggest better FP test performance with i-ELISA than with c-ELISA; however, i-ELISA does not distinguish cross-reacting antibodies induced by Brucella vaccination or exposure to certain other Gram-negative pathogens. Results for duplicate FP eluates (prepared using separate FP strips from each animal) were strongly correlated for both protocols (r=0.996 and 0.999 for c-ELISA and i-ELISA, respectively), indicating minimal variability among FPs from any individual caribou. Dried caribou FP blood samples stored for 2 mo at room temperature are comparable with serum for use in Brucella spp. c-ELISA and i-ELISA. Hunter-based FP sampling can facilitate detection of disease exposure in remote regions and under adverse conditions, and can expand wildlife disease surveillance across temporospatial scales.

Experimental infection of reindeer with cervid herpesvirus 2.

Cervid herpesvirus 2 (CvHV2) has been isolated from reindeer (Rangifer tarandus tarandus), and serological data indicate that in reindeer this virus is endemic in Fennoscandia, Alaska, Canada, and Greenland. CvHV2 has been described as a cause of subclinical genital infections in reindeer, but little information on primary infections exists. In this study, six seronegative and presumably pregnant reindeer were allocated to one of two groups. Two animals were inoculated with CvHV2 intratracheally, and two animals intravaginally, with one control animal in each group receiving sterile water. Mild hyperthermia and serous discharges from the vagina and nose were observed. No abortions were recorded, but one calf died shortly after birth. Inoculated animals seroconverted and had neutralizing antibodies after days 7 to 10 postinfection. CvHV2 was detected by PCR in nasal and vaginal swabs from animals in both groups but could be isolated only from nasal swabs in the respiratory group and from vaginal swabs in the genital group. CvHV2 was detected by PCR in various organs and tissues postmortem. In control animals, the virus could not be isolated in spite of PCR-positive nasal and vaginal swab samples and some degree of positive immunostaining. One of the animals that were inoculated intratracheally developed a hemorrhagic, necrotizing bronchopneumonia, which was CvHV2 positive by PCR and immunohistochemistry. We conclude that CvHV2 can cause systemic infection, that both genital and respiratory inoculations can lead to virus shedding, and that the virus can infect the fetus in utero.

Reindeer beta-defensin-1: full-length cDNA cloning and tissue expression.

Defensins are members of a large diverse family of cationic antimicrobial peptides that share a signature pattern consisting of six conserved cysteine residues. Here we report the identification of a novel beta-defensin, reindeer beta-defensin-1 (reBD-1), from reindeer tissues with a pair PCR primers according to the conserved cDNA sequences of known ruminant beta-defensins. Total RNA was extracted from the tongue epithelia of a reindeer and the 372bp cDNA encoding reBD-1 was amplified by the reverse transcription PCR (RT-PCR), 5'- and 3'-RACE. The cDNA contained a open reading frame (ORF) of 192 bases which encoded a 64 amino acid prepro-peptide and the prepro-peptide contained the beta-defensin consensus sequence of six invariantly spaced cysteine residues. The sequence homology shows that reBD-1 has 68.8-87.5% amino-acid identity and 76.6-90.9% cDNA identity with other ruminant beta-defensins, sharing the greatest identity with buffalo enteric beta-defensin in both amino acid and nucleotide sequences. The reBD-1 mRNA was detected throughout the digestive tracts and also in trachea, lung, kidney, urinary bladder, testis, epididymis, heart, liver, spleen by RT-PCR. The wide expression of reBD-1 indicates that this endogenous peptide may contribute to both mucosal and systemic host defenses in reindeers.

Blood culture and stimulation conditions for the diagnosis of tuberculosis in cervids by the Cervigam assay.

Mitogen- and antigen-induced interferon-gamma (IFN-gamma) responses of peripheral blood leucocytes from cervids were evaluated by a commercial whole-blood assay. The assay was applied to Mycobacterium bovis-infected white-tailed deer and reindeer, M bovis BCG-vaccinated white-tailed deer and elk, and unvaccinated, uninfected white-tailed deer, fallow deer, elk and reindeer. The responses of the M bovis-infected white-tailed deer to pokeweed mitogen (PWM) varied with time and between individuals. The responses of the M bovis-infected reindeer to PWM and M bovis purified protein derivative (PPD) were positively associated. Samples from tuberculosis-free captive herds in various parts of the USA were also evaluated. Four per cent of fallow deer, 20 per cent of elk, 44 per cent of white-tailed deer, and 91 per cent of reindeer had responses to PWM exceeding 0.25 Delta optical density, that is, PWM stimulation minus no stimulation. The specificity of the responses to M bovis PPD and a Mycobacterium tuberculosis complex-specific antigen rESAT-6:CFP-10, excluding animals not responding to PWM, ranged from 78 per cent to 100 per cent and was dependent upon the species and the positive response cut-off value. The results show that the commercial assay is valid for the detection of TB in reindeer; however, further development of the assay will be required before it is used in surveillance programmes for white-tailed deer, fallow deer, and elk.

IgE cross reactivity between reindeer and bovine milk beta-lactoglobulins in cow's milk allergic patients.

BACKGROUND: Allergic reactions to cow's milk are common in small children. One of the main protein allergens found in cow's milk is beta-lactoglobulin (beta-Lg). Reindeer and bovine milk both contain related beta-Lg proteins, but the allergenicity of reindeer beta-Lg has not previously been studied. The purpose of this study was to analyze the immunological cross-reactivity of IgE antibodies from children with cow's milk allergy to reindeer and bovine beta-Lg. METHODS: Sera from 17 children and a serum pool of 4 patients with elevated cow's milk-specific IgE were investigated. Beta-Lg from bovine and reindeer milk was isolated in native form and an enzyme-linked immunosorbent inhibition assay was developed. Bovine beta-Lg was used as a capturing antigen and the inhibiting effects of reindeer and bovine beta-Lg on the IgE binding were measured. RESULTS: Cross-reactivity patterns of bovine milk beta-Lg specific IgE to reindeer beta-Lg varied among patients. In general, reindeer beta-Lg showed significantly lower inhibition (mean 43%) of IgE binding to the capturing antigen than did bovine beta-Lg (mean 89%). In some patients, even high concentrations of reindeer beta-Lg only partly eliminated the IgE binding to bovine beta-Lg. CONCLUSIONS: The partial cross-reactivity of human anti-bovine IgE with reindeer beta-Lg suggests that it lacks important bovine epitopes and those that are recognized are only weakly bound.

Antigen-specific proliferation and activation of peripheral blood mononuclear cells from Mycobacterium bovis-infected reindeer.

To evaluate antigen-specific proliferative and activation-associated responses from Mycobacterium bovis-infected reindeer, blood mononuclear cells from M. bovis- (n = 10) and non-infected reindeer (n = 4) were stimulated with a recombinant early secretory antigenic target-6 and culture filtrate protein-10 fusion protein (rESAT6:CFP10), M. bovis purified protein derivative, pokeweed mitogen, or medium alone and evaluated by flow cytometry using dye tracker analysis and cell surface marker staining. gammadelta TCR+ and CD8+ cells, but not CD4+ cells, from M. bovis-infected reindeer proliferated in response to specific antigen stimulation. Expression (i.e., mean fluorescence intensity) of CD44 was increased and CD62L decreased on proliferative as compared to non-proliferative fractions in antigen- and mitogen-stimulated cultures. In response rESAT6:CFP10 stimulation, MHC II fluorescence intensity was increased on CD4+, gammadelta TCR+, CD172a+, and IgM+ cells from infected reindeer as compared to that of non-stimulated cells from the same reindeer. Recombinant ESAT6:CFP10 stimulation also induced expansion of a CD172a+, MHC II+ population within mononuclear cell cultures from M. bovis-infected reindeer. Despite a moderate challenge dose and extended duration of incubation, experimental infection of reindeer was generally limited to lymph nodes draining the inoculation site, suggestive of host resistance to progressive disease. Present in vitro findings, therefore, may be predictive of host responses by reindeer that limit progression to disseminated disease.

Diagnostic implications of antigen-induced gamma interferon production by blood leukocytes from Mycobacterium bovis-infected reindeer (Rangifer tarandus).

The only approved method of tuberculosis (TB) surveillance of reindeer within the United States is tuberculin skin testing; however, skin testing has an apparent lack of specificity, since numerous reindeer are classified as reactors, yet Mycobacterium bovis is not isolated from tissues upon necropsy. The objective of this study was to evaluate the ability of an in vitro assay (the Cervigam assay) to detect gamma interferon (IFN-gamma) produced by blood leukocytes in response to mycobacterial antigens from M. bovis-infected reindeer. Thirteen male reindeer approximately 9 months of age were inoculated with 10(5) CFU M. bovis in their tonsillar crypts. Stimulation of whole-blood cultures with a mitogen resulted in significant production of IFN-gamma compared to that by nonstimulated samples. Responses by infected reindeer to M. bovis purified protein derivative (PPD) were as much as 3.5-fold higher than those by noninfected reindeer (n = 4). Despite differences in responses to PPD by the two groups, reindeer within the noninfected group had responses of >0.1 change in optical density (DeltaOD) (a level generally considered positive) to PPD. Mean responses by infected reindeer to a rESAT-6-CFP-10 fusion protein (Mycobacterium tuberculosis complex specific) were as much as 20-fold higher than respective responses by noninfected reindeer at all time points. Additionally, responses by 3/4 noninfected reindeer were <0.1 DeltaOD (considered negative) at each time point. To further evaluate the specificity of the assay, samples were collected from reindeer in a TB-free herd. All reindeer had responses to mitogen; however, only 1 of 38 had a response to PPD, and none of the reindeer responded to rESAT-6-CFP-10. Together, these findings indicate that IFN-gamma-based tests may prove useful for TB surveillance of reindeer.

Antibody responses in reindeer (Rangifer tarandus) infected with Mycobacterium bovis.

Despite having a very low incidence of disease, reindeer (Rangifer tarandus) are subject to tuberculosis (TB) testing requirements for interstate shipment and herd accreditation in the United States. Improved TB tests are desperately needed, as many reindeer are falsely classified as reactors by current testing procedures. Sera collected sequentially from 11 (experimentally) Mycobacterium bovis-infected reindeer and 4 noninfected reindeer were evaluated by enzyme-linked immunosorbent assay (ELISA), immunoblotting, and multiantigen print immunoassay (MAPIA) for antibody specific to M. bovis antigens. Specific antibody was detected as early as 4 weeks after challenge with M. bovis. By MAPIA, sera were tested with 12 native and recombinant antigens, which were used to coat nitrocellulose. All M. bovis-infected reindeer developed responses to MPB83 and a fusion protein, Acr1/MPB83, and 9/11 had responses to MPB70. Other antigens less commonly recognized included MPB59, ESAT-6, and CFP10. Administration of purified protein derivatives for skin testing boosted serum antibody responses, as detected by each of the assays. Of the noninfected reindeer, 2/4 had responses that were detectable immediately following skin testing, which correlated with pathological findings (i.e., presence of granulomatous lesions yet the absence of acid-fast bacteria). The levels of specific antibody produced by infected reindeer appeared to be associated with disease progression but not with cell-mediated immunity. These findings indicate that M. bovis infection of reindeer elicits an antibody response to multiple antigens that can be boosted by skin testing. Serological tests using carefully selected specific antigens have potential for early detection of infections in reindeer.

Dynamics of antibodies against hypodermin C in reindeer infested with the reindeer warble fly, Hypoderma tarandi.

Serum samples from 25 reindeer (Rangifer tarandus tarandus) were assayed for antibody against hypodermin C (HyC) using an ELISA. Nineteen animals were calves (born in 1998, 1999 or 2001) and six were adults (3-10 years old at first blood collection). The samples were collected over periods of 4 months (calves born in 2001) or 27 months (adults and calves born in 1998 and 1999), the latter encompassing three Hypoderma tarandi infestation seasons. The calves received antibodies against HyC from their mothers, either by placental transfer or through the ingestion of colostrum. The low level at 3 h postpartum compared to the high level 3 days after birth in one calf suggests that the antibodies are transferred through colostrum. The levels of antibody of maternal origin decreased rapidly and reached low levels by mid-July, which coincides with the onset of the major Hypoderma ovipositioning season in this region. The calves thus did not appear to be protected by antibody against HyC when they were exposed to H. tarandi infestation for the first time. Antibody levels increased following infestation and reached a maximum during November or December, which coincides with when the H. tarandi larva stops migrating after it has reached the site under the skin of the back of the host and develops further. Levels declined thereafter and reached a nadir during the following summer. After the subsequent re-infestation, the increase in levels occurred at least 1 month earlier than with the first infestation. Levels remained elevated throughout the year after repeated infestations. This implies that the antibodies persist after the annual exit of mature larvae from the animal, and after larvae have been killed by application of ivermectin. Levels in adults, however, declined significantly with age, and levels were significantly lower in animals that were 4-11 years old than in 1-year-old animals during the same 1-year period. This supports the contention that the functional capacity of the immune system declines gradually with age. The study demonstrated that HyC is potentially useful for serological diagnosis of hypodermosis in reindeer, but the persistence of antibodies complicates interpretation of antibody-based surveillance programme data in all cases other than first-time exposure.

Acute phase response in reindeer after challenge with Escherichia coli endotoxin.

The serum concentrations of two acute phase proteins (APPs), haptoglobin (Hp) and serum amyloid-A (SAA), were monitored in reindeer after challenge with endotoxin. Four adult female reindeer received either 0.1 microg/kg Escherichia coli 0111:B4 lipopolysaccharide B or saline solution intravenously. At the second challenge, the treatments were reversed. In addition to the APPs, changes in blood chemistry and rectal temperature were monitored. The endotoxin challenge caused a significant increase in SAA (peak 48 h) and a sharp decrease (8-12 h) of serum iron concentrations in all animals. The mean Hp concentration increased at 8 h and remained elevated until 48 h, but no statistically significant differences were found. This investigation demonstrates that challenge with a single-bolus dose of E. coli endotoxin can activate the acute phase response (APR) and SAA appears to be a more sensitive indicator of the APR than Hp during bacterial infection in reindeer.

Induction of neutralizing antibodies in reindeer (Rangifer tarandus) after administration of a killed West Nile virus vaccine.

In 2002, West Nile virus (WNV) infection with clinical neurologic disease and encephalomyelitis was described in reindeer (Rangifer tarandus). The susceptibility of reindeer to WNV prompted questions concerning vaccination of reindeer to prevent WNV infection. Between January and April 2003, eleven 2-4-yr-old, castrated male reindeer, some of which had antibody titers suggestive of prior exposure to WNV, were vaccinated three times at 4-wk intervals with a commercially available vaccine approved for use in horses. No adverse reactions to vaccination were noted. All vaccinated reindeer developed high neutralizing antibody titers to WNV, as determined by the plaque reduction neutralization test. Reindeer without antibody titers from previous natural exposure to WNV required a primary vaccination and one or two booster vaccinations for development of neutralizing antibody to WNV. Protective efficacy of vaccination was not evaluated. Vaccination of reindeer for WNV may be warranted in certain circumstances combined with management practices to limit exposure to potential vectors.

Serological differentiation of Brucella-vaccinated and -infected domesticated animals by the agar gel immunodiffusion test using Brucella polysaccharide in mongolia.

To investigate Brucella infection in cattle, sheep, goat, reindeer and yak in Mongolia, serological reactions of Brucella-infected and -vaccinated domestic animals were compared by the agar gel immunodiffusion (AGID) test with a polysaccharide (poly-B) of the B. Abortus strain S-19. The sensitivity and specificity were compared with conventional serological tests that are commonly used in Mongolia, such as the rose Bengal test, the tube agglutination test and the compliment fixation test. A total of 73.3, 100, 100, 95.8 and 61.9% of the sera from suspected cattle, yak, goat, sheep and reindeer, respectively, that were positive in the compliment fixation test, were also positive in the AGID test. Sera from vaccinated cattle, sheep and goat were positive over 90% by conventional tests 3 months after vaccination, but were negative by the AGID. These results suggest that the AGID test may be useful to differentiate infected and vaccinated animals in the field.

Prevalence of Toxoplasma gondii antibodies in barren-ground caribou (Rangifer tarandus groenlandicus) from the Canadian Arctic.

Prevalence of antibodies to Toxoplasma gondii was determined in 147 barren-ground caribou (Rangifer tarandus groenlandicus) from 5 herds in the Northwest Territories and Nunavut, northern Canada, by the modified agglutination test (MAT). In the mainland herds (Bluenose, Bathurst, and Beverly), antibodies were found in 43 (37%) of 117 caribou, and MAT titers were 1:25 in 10, 1:50 in 24, and 1:500 in 9. In the island herds, only 1 (4.3%) of 23 animals sampled from the North Baffin Island herd was positive (titer = 1:25) and no antibodies were detected in 7 caribou from the Dolphin and Union herd. The high prevalence of antibodies to T. gondii in the mainland caribou herds indicates that caribou meat may contain viable T. gondii.

No interspecific covariation in intensities of macroparasites of reindeer, Rangifer tarandus (L.).

The macroparasites Cephenemyia trompe (Modeer) and Hypoderma (= Oedemagena) tarandi (L.) (Diptera: Oestridae), Linguatula arctica Riley, Haugerud and Nilssen (Pentastomida: Linguatulidae), Elaphostrongylus rangiferi Mitskevich (Nematoda: Protostrongylidae), and abomasal nematodes (Nematoda: Trichostrongylidae) were sampled in semidomestic reindeer calves (Rangifer tarandus (L.)) (ca. 8 months of age) in northern Norway in 1988 (n = 160) and 1989 (n = 191). Each parasite showed an aggregated (clumped) distribution among the hosts and fitted the negative binomial distribution. Analyses of interspecific associations in intensities showed that there was no consistent covariation among the parasites apart from a weak correlation (Kendall's tau 0.104, P = 0.007) between the 2 oestrids C. trompe and H. tarandi. This lack of covariation reveals that the parasites were distributed independently of each other, and suggests that innate host resistance is not a dominant factor that has a significant simultaneous effect on all parasites. The aggregated distribution of each parasite species is hypothesized to be caused by (1) random events and heterogeneities in host behaviour that create unequal transmission (exposure) rates, or (2) by heterogeneities in parasite specific immunocompetence among host individuals. Factors in hypothesis (1) are probably the most important at low transmission rates.

Increase in gamma delta T cells in the ruminal mucosa of reindeer calves (Rangifer tarandus tarandus L.) induced by baled grass silage.

Leukocytes in the forestomach mucosa of reindeer (Rangifer tarandus tarandus L.) were investigated by immunoperoxidase staining of cryostat sections, using monoclonal antibodies against antigens on sheep leukocytes. Mucosal samples from three free-ranging reindeer calves were compared with samples from three calves fed baled grass silage previously shown to induce increased frequency of lesions in the ruminal epithelium. In both groups, MHC-II + cells and gamma delta T cells were observed, located within or just below the basal layer of the stratified epithelium. Computer-assisted morphometric analysis showed that the number of gamma delta T cells in the ruminal mucosa was higher in the silage-fed than in the free-ranging animals. No marked difference in number of MHC-II + Langerhans cells was observed between the groups.