Brucellosis in free-ranging bison (Bison bison) from Teton County, Wyoming

Divergent impacts of warming weather on wildlife disease risk across climates

Disease outbreaks among wildlife have surged in recent decades alongside climate change, although it remains unclear how climate change alters disease dynamics across different geographic regions. We amassed a global, spatiotemporal dataset describing parasite prevalence across 7346 wildlife populations and 2021 host-parasite combinations, compiling local weather and climate records at each location. We found that hosts from cool and warm climates experienced increased disease risk at abnormally warm and cool temperatures, respectively, as predicted by the thermal mismatch hypothesis. This effect was greatest in ectothermic hosts and similar in terrestrial and freshwater systems. Projections based on climate change models indicate that ectothermic wildlife hosts from temperate and tropical zones may experience sharp increases and moderate reductions in disease risk, respectively, though the magnitude of these changes depends on parasite identity.

When to vaccinate a fluctuating wildlife population: Is timing everything?

Wildlife vaccination is an important tool for managing the burden of infectious disease in human populations, domesticated livestock and various iconic wildlife. Although substantial progress has been made in the field of vaccine designs for wildlife, there is a gap in our understanding of how to time wildlife vaccination, relative to host demography, to best protect a population.We use a mathematical model and computer simulations to assess the outcomes of vaccination campaigns that deploy vaccines once per annual population cycle.Optimal timing of vaccination is an important consideration in animals with short to intermediate life spans and a short birthing season. Vaccines that are deployed shortly after the birthing season best protect the host population.The importance of timing is greater in wildlife pathogens that have a high rate of transmission and a short recovery period. Vaccinating at the end of the birthing season best reduces the mean abundance of pathogen-infected hosts. Delaying vaccination until later in the year can facilitate pathogen elimination. Policy Implications. Tuning wildlife vaccination campaigns to host demography and pathogen traits can substantially increase the effectiveness of a campaign. Our results suggest that, for a fluctuating population, vaccinating at, or shortly after, the end of the birthing season, best protects the population against an invading pathogen. If the pathogen is already endemic, delaying vaccination until after the birthing season is over can help facilitate pathogen elimination. Our results highlight the need to better understand and predict host demography in wildlife populations that are targeted for vaccination.

HEALTH STATUS OF REINTRODUCED WOOD BISON ( BISON BISON ATHABASCAE): ASSESSING THE CONSERVATION VALUE OF AN ISOLATED POPULATION IN NORTHWESTERN CANADA

A central goal for reintroduced populations of threatened wood bison ( Bison bison athabascae) is to maintain them free of diseases of concern, particularly bovine tuberculosis (caused by Mycobacterium bovis) and brucellosis (caused by Brucella abortus). A wood bison population in southwestern Yukon, Canada was reintroduced into the wild in 1988, but no health assessment has been done since then. To provide an initial assessment of the health status and, hence, the conservation value of this population, we serologically tested 31 wood bison (approximately 3% of the population) for pathogens of interest and obtained histopathology results for select tissues. We found no evidence of exposure to M. bovis or Brucella spp., but antibodies were present to bovine parainfluenza virus 3, bovine coronavirus, Leptospira interrogans, and Neospora caninum, with seroprevalences of 87, 7, 61, and 7% of the tested animals, respectively. Reintroduced wood bison in southwestern Yukon may be of high value for wood bison recovery because it is a large and geographically isolated population with no bacteriologic, histopathologic, or serologic evidence of exposure to Brucella spp. or M. bovis.

Genomics reveals historic and contemporary transmission dynamics of a bacterial disease among wildlife and livestock

Whole-genome sequencing has provided fundamental insights into infectious disease epidemiology, but has rarely been used for examining transmission dynamics of a bacterial pathogen in wildlife. In the Greater Yellowstone Ecosystem (GYE), outbreaks of brucellosis have increased in cattle along with rising seroprevalence in elk. Here we use a genomic approach to examine Brucella abortus evolution, cross-species transmission and spatial spread in the GYE. We find that brucellosis was introduced into wildlife in this region at least five times. The diffusion rate varies among Brucella lineages (∼3 to 8 km per year) and over time. We also estimate 12 host transitions from bison to elk, and 5 from elk to bison. Our results support the notion that free-ranging elk are currently a self-sustaining brucellosis reservoir and the source of livestock infections, and that control measures in bison are unlikely to affect the dynamics of unrelated strains circulating in nearby elk populations.

Live RB51 vaccine lyophilized hydrogel formulations with increased shelf life for practical ballistic delivery

Ballistic delivery capability is essential to delivering vaccines and other therapeutics effectively to both livestock and wildlife in many global scenarios. Here, lyophilized poly(ethylene glycol) (PEG)-glycolide dimethacrylate crosslinked but degradable hydrogels were assessed as payload vehicles to protect and deliver a viable bacterial vaccine, Brucella abortus strain RB51 (RB51), ballistically using commercial thermoplastic cellulosic degradable biobullets. Degradable PEG hydrogel rods loaded with ∼10(10) live RB51 bacteria (CFUs) were fabricated using three different polymerization methods, cut into fixed-sized payload segments, and lyophilized. Resulting dense, glassy RB51 vaccine-loaded monoliths were inserted into thermoplastic biobullet 100-μL payload chambers. Viability studies of lyophilized formulations assessed as a function of time and storage temperature supported the abilities of several conditions to produce acceptable vaccine shelf-lives. Fired from specifically designed air rifles, gel-loaded biobullets exhibit down-range ballistic properties (i.e., kinetic energy, trajectory, accuracy) similar to unloaded biobullets. Delivered to bovine tissue, these hydrogels rehydrate rapidly by swelling in tissue fluids, with complete hydration observed after 5h in serum. Live RB51 vaccine exhibited excellent viability following carrier polymerization, lyophilization, and storage, at levels sufficient for vaccine dosing to wild range bison, the intended target. These data validate lyophilized degradable PEG hydrogel rods as useful drug carriers for remote delivery of both live vaccines and other therapeutics to livestock, wildlife, or other free-range targets using ballistic technologies.

Brucellosis in the United States: role and significance of wildlife reservoirs

Regulatory programs for brucellosis in domestic livestock have been active in the U.S. for almost 80 years. Wildlife reservoirs of brucellosis include bison (Bison bison) and elk (Cervus elaphus nelsonii) for Brucella abortus whereas Brucella suis is the predominant species infecting feral swine. The persistence of brucellosis in wildlife reservoirs poses a risk for reintroduction of Brucella into domestic livestock. Reducing the prevalence of brucellosis in wildlife reservoirs is anticipated to be complicated and costly, and the problem is unlikely to be quickly resolved. Although some tools are currently available for use in the wildlife reservoirs, development of new vaccines, diagnostics, and management procedures will most likely be needed for effective control of brucellosis.

Historical perspective and future directions in training of veterinary pathologists with an emphasis on zoo and wildlife species

This article discusses the history of the field of zoo and wildlife pathology, training opportunities for veterinary students and graduate veterinarians, and current and future job opportunities. The niches occupied by veterinarians in this field and their contributions to animal and human health are also highlighted. The field of zoo and wildlife, or "non-traditional" species, pathology has its roots in comparative anatomy, zoology, wildlife biology, and medical pathology in the mid- to late nineteenth century. The initial emphasis was on comparisons between animal and human diseases or on management of game animals. Veterinarians became increasingly involved during the twentieth century, gradually changing the emphasis to improvement of conservation strategies, captive care, and elucidation of diseases of concern for the animals themselves. Currently there are several zoos and wildlife agencies in the United States employing full-time veterinary pathologists. Private and government diagnostic laboratories, veterinary schools, and other academic institutions in the United States with pathology departments are other employers. The field requires post-DVM training by means of a residency program leading to board certification, graduate school (MS or PhD degrees), or both. Veterinary students can gain valuable experience in the field through externships and, at some schools, through elective courses in the curriculum. Current concerns about ecosystem health, bioterrorism, and the recognition that captive and free-ranging wildlife can serve as sentinel species will increase the demand for veterinary pathologists choosing this very rewarding career path specializing in non-traditional species.

Brucella vaccines in wildlife

Brucellosis has been known to exist in populations of wildlife since the early part of the 20th century. At the beginning of this century in the US, Brucella abortus is a problem in elk and bison in the Greater Yellowstone Area, B. suis is prevalent in millions of feral swine in most of the southern states, and caribou/reindeer in Alaska are infected with B. suis biovar 4. Brucellosis has been virtually eliminated in domestic livestock in the US after decades of expensive governmental disease prevention, control and eradication programs. Now the most likely source of transmission of brucellosis to humans, and the risk of reintroduction of brucellosis into livestock is from infected populations of free-ranging wildlife. Brucellosis was eradicated from livestock through a combination of testing, vaccination, and removal of infected animals. The use of vaccines to control brucellosis in populations of wildlife and therefore reducing the risk of transmission to humans and livestock has been proposed in several instances. This manuscript reviews research on the use of Brucella vaccines in species of wildlife with emphasis on safety and efficacy.

Seminal vesiculitis and orchitis caused by Brucella abortus biovar 1 in young bison bulls from South Dakota

Specimens of blood, lymph nodes, spleens, and genitalia were collected at slaughter from seven 3- and 4-year-old male bison that had recently become seropositive for brucellosis. The animals were from a captive herd of approximately 3,500 bison located in central South Dakota. Brucella abortus biovar 1 was isolated from 2 or more specimens from each of 6 bison. Severe necrotizing and pyogranulomatous orchitis was present in 1 testicle from 1 bull, and 4 animals had mild to marked seminal vesiculitis. Immunohistochemical staining labeled organisms in seminal vesicles and the testicle with orchitis. Ultrastructurally, intact bacilli were present in cytoplasmic vacuoles of some macrophages; other macrophages contained intracytoplasmic aggregates of calcified coccobacilli.

Immune responses and resistance to brucellosis in mice vaccinated orally with Brucella abortus RB51

Immune responses and resistance to infection with Brucella abortus 2308 (S2308) were measured in mice following oral or intraperitoneal (i.p.) vaccination with strain RB51 (SRB51). Bacteria persisted in the parotid lymph node for 4 weeks following oral vaccination of mice with 5 x 10(8) or 5 x 10(6) CFU of SRB51. Bacteria did not appear in the spleen during 12 weeks after oral vaccination, whereas they did appear in the spleen for 8 weeks following i.p. vaccination of mice with SRB51 (5 x 10(8) or 5 x 10(6) CFU). Increased resistance to S2308 infection occurred at 12 to 20 weeks in mice vaccinated i.p. with SRB51 (5 x 10(8) or 5 x 10(6) CFU) but occurred at 12 weeks only in mice vaccinated orally with SRB51 (5 x 10(8) CFU). Oral SRB51 vaccination induced lower levels of antibodies to the surface antigens of intact SRB51 bacteria than did i.p. vaccination. However, neither route of vaccination induced anamnestic antibody responses to the surface antigens of intact S2308 bacteria after challenge infection of the vaccinated mice with S2308. Mice vaccinated orally with SRB51 and challenged with S2308 at 12 to 20 weeks had lower and less persistent spleen cell proliferation and production of gamma interferon in response to S2308 and certain immunodominant S2308 proteins (32 to < or = 18 kDa) than did mice vaccinated i.p. with SRB51. However, mice vaccinated orally or i.p. with SRB51 and challenged with S2308 had similar spleen cell tumor necrosis factor alpha production. These results indicate that oral vaccination of mice with SRB51 was effective in inducing protective immunity to S2308 infection, although the immunity was lower and less persistent than that induced by i.p. vaccination. The lower protective immunity induced by oral vaccination may have resulted from lower and less persistent cell-mediated immunity and gamma interferon production in response to S2308 and S2308 proteins.

Determination of stability of Brucella abortus RB51 by use of genomic fingerprint, oxidative metabolism, and colonial morphology and differentiation of strain RB51 from B. abortus isolates from bison and elk

Brucella abortus RB51 and isolates from cattle, bison, and elk were characterized by pulsed-field gel electrophoresis and standard techniques for biotyping Brucella species, which included biochemical, morphological, and antigenic techniques, phage susceptibility, and antibiotic resistance. The objectives were to ascertain the stability of RB51 and to differentiate RB51 from other brucellae. Genomic restriction endonuclease patterns produced by pulsed-field gel electrophoresis demonstrated a unique fingerprint for RB51 relative to other brucellae. Comparisons of the oxidative metabolic profiles of RB51 after time in vivo (14 weeks) and in vitro (75 passages) showed no change in characteristic patterns of oxygen uptake on selected amino acid and carbohydrate substrates. Strain RB51 was biotyped as a typical rough B. abortus biovar 1 (not strain 19) after animal passage or a high number of passages in vitro and remained resistant to rifampin or penicillin and susceptible to tetracycline. No reactions with A or M antiserum or with a monoclonal antibody to the O antigen of Brucella lipopolysaccharides were detected; however, RB51 agglutinated with R antiserum. The results indicate that the genomic fingerprint and rough colonial morphology of RB51 are stable characteristics and can be used to differentiate this vaccine strain from Brucella isolates from cattle, bison, and elk.