• Detection and control of brucellosis in reindeer vaccinated with Brucella suis biovar 3

      Bevins, Julia Stahmann (1993)
      The objective of this research was to provide a vaccine for the control of brucellosis in reindeer, that allows serologic discrimination between vaccinated and infected animals. Three vaccines were tested: (1) Brucella suis 1, (2) B. suis 3, and (3) A rough mutant of the infective strain, B. suis 4. All were heat-killed and prepared in Freund's incomplete adjuvant. Each vaccine was administered to four animals. All vaccines stimulated the production of high levels of antibody in Rangifer that were maintained for the 483-day experiment. Significant delayed-type hypersensitivity reactions were seen in all vaccinated Rangifer. Both B. suis 1 and B. suis 3 vaccines allowed serologic discrimination between vaccinated and infected Rangifer. This was accomplished by means of an indirect ELISA (enzyme-linked immunosorbent assay). This test used whole cell B. melitensis and B. abortus as A and M-dominant antigens. Distinction could be made between vaccinated and infected reindeer based on a percentage difference in spectrophotometric abosorbance values obtained with these antigens. The B. suis 3 vaccine provided the best discrimination. Eighty-nine percent of 117 reindeer were correctly classified as either B. suis 3-vaccinated or B. suis 4-infected. Discrimination between vaccinated and infected reindeer was sufficient to allow assessment of the prevelance of brucellosis and vaccinated herds. In addition, the ELISA was more sensitive than standard agglutination tests in identifying reindeer with exposure to B. suis. The B. suis 3 vaccine was further evaluated in a challenge of 7 vaccinated reindeer. The vaccinated group consisted of 5 pregnant adults and 2 8-month-old female calves. These reindeer were challenged with $3.16\times10\sp7$ colony forming units of B. suis 4 at 63 days post-vaccination. Five pregnant adults and 1 female calf served as experimental controls. B. suis 4 was isolated from 3 of 7 vaccinated reindeer (43%) at the time of necropsy. B. suis 4 was isolated from the aborted fetus of 1 of the infected vaccinates. Another infected vaccinate bore a healthy calf for which B. suis 4 could not be isolated. All control reindeer were infected and all 5 adults aborted. B. suis 4 was isolated from all 5 fetuses. The B. suis 3 vaccine provided significant protection against infection and abortion in reindeer challenged with B. suis 4.
    • Investigations of health status and body condition of harbor seals (Phoca vitulina) in the Gulf of Alaska

      Fadely, Brian Scott; Castellini, Michael A. (1997)
      Harbor seal (Phoca vitulina) declines during the past 20 years in the Kodiak Island and Prince William Sound regions contrast with stable or slightly increasing populations in southeastern areas of Alaska. Aspects of health status and body condition were investigated to test the hypothesis that these declines were driven by nutritional limitation, and to determine whether recent differential population trajectories among Kodiak Island, Prince William Sound, and southeast Alaska could have health-related components. For comparisons between 1992-96, three aspects of health status were examined; blood chemistry, blubber distribution and quantity; and blubber quality. Clinical ranges of plasma chemistries and hematologies were established for free-ranging seals in the Gulf of Alaska. Significant handling, individual, and seasonal effects were found on many blood parameters that could bias interannual and interregional comparisons if not incorporated in models. Based on statistical modeling, some seals showed more clinically aberrant values than expected by chance, but these were not clumped among regions or years. Differences existed in interannual blood chemistry and hematology patterns between juveniles and adults. Likewise, there were regional differences in blood chemistries of unknown significance. Morphometric indices were poor indicators of condition defined as size-at-age or blubber content. This was related to patterns of blubber distribution and variability, which differed between males and females. Blubber quality, measured as lipid content, did not substantially vary seasonally or between geographic regions, but blubber from Prince William Sound was less hydrated than blubber from non-declining areas. There were no detectable differences in body condition of seals from the Gulf of Alaska sampled during 1963/64 (pre-decline), 1976-78 (during decline) and 1995-96. However, sample sizes were small and patchily distributed throughout locations and years. Thus, the likelihood of detecting body condition changes in response to environmental conditions was poor. Body condition was not substantially different among seals from Prince William Sound, Kodiak Island and southeast Alaska measured during 1993-96. However, interannual blood chemistry and body condition patterns were evident among Prince William Sound seals that may have been associated with environmental conditions.
    • Pathophysiology of infections by the gastric trichostrongylid Obeliscoides in a rabbit model system

      Nielsen, Carol A.; White, Robert G.; Dieterich, Robert A. (1991)
      The gastric trichostrongylid parasite Obeliscoides sp. was isolated from Alaskan snowshoe hares (Lepus americanus) and passaged 3 times in laboratory rabbits (Oryctolagus cuniculus). Despite its low fertility, the isolate persisted, often as occult infections, for up to 45 weeks and produced physiologic effects in clinically normal rabbits. Prominent eosinophilic and hyperplastic lesions of the gastric mucosa occurred during post-inoculation weeks (PIW) 2-15, while mononuclear aggregations were seen in older infections. Gastric lesion severity was directly related to size of the Obeliscoides population, which declined over time and was smaller in secondary infections. Anorexia occurred within 3 weeks of infective larval inoculation in 12 (of 21) primary and 2 (of 10) secondary infections. Serum total protein, albumin, and the A/G ratio were significantly reduced in anorectic infected rabbits compared to fasted uninfected rabbits. Fecal N excretion was significantly increased between PIW 1 and 5 in rabbits with primary infections, and during PIW 1 and 2 for those with secondary infections. Nitrogen absorption was enhanced during PIW 5-15 of primary infection. Serum gastrin concentrations, determined for the first time in Obeliscoides-infected rabbits by radioimmunoassay, were significantly elevated in primary infections during PIW 6 and 7, while hypokalemia was apparent during PIW 5. Hypermagnesemia occurred in both primary and secondary infections between PIW 8 and 15. Other serum constituents and concentrations of N, Ca and P in the gastrointestinal tract and feces remained largely unchanged. Total mean retention time (TMRT), 31.8 h, and GI turnover time (GITT), 26.3 h, of the fiber component (determined with Ce-141-marked fiber $>$355 microns) were significantly prolonged in secondary infections during PIW 16 to 26. TMRT (53.0 h) and GITT (57.0 h) of the liquid component (using Cr-51 EDTA), were determined for the first time in rabbits, and were not significantly changed by Obeliscoides infection. Persisting populations of this Obeliscoides isolate caused physiologic and pathologic alterations in clinically healthy rabbits. Because these effects were similar to those seen in ruminant Ostertagia spp. infections, this laboratory model could be useful in understanding the pathophysiology of costly production losses that occur in parasitized commercial livestock.