Abstract. 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.Brucella abortus produces abortion in cattle, bison, 9,19,23 and elk. 21 Additionally, metritis and retained placentas are associated with the infection in cattle and bison. 7,23 In male cattle, brucellosis typically is associated with seminal vesiculitis, orchitis, and epididymitis. There are few reports of similar lesions in the genitalia of B. abortus-infected bison bulls. 7,8,22,23 The purpose of this report is to describe the sites of bacterial localization and lesions associated with natural infection by B. abortus in 3-and 4-year-old bison bulls from a large captive herd in South Dakota. Materials and methodsBlood and tissue specimens including lymph nodes, spleen, and genitalia were collected from seven 3-and 4-yrold bison bulls at slaughter (Table 1). The bulls were from a herd of 3,500 bison located in central South Dakota. The herd was under state quarantine and had been engaged in a whole-herd test and slaughter program since 1990. In December 1994, 80, 3-and 4-yr-old bulls and 4 adult cows were seropositive on standard serologic tests for brucellosis. These animals had been seronegative on all previous tests; the last test had been in the spring of 1994. All of the seropositive animals were slaughtered for meat.Portions of testicles, epididymides, and seminal vesicles were removed and placed in 10% neutral buffered formalin.
From December 1998 through February 1999, a study was conducted in a Brucellainfected bison herd to evaluate the safety of booster vaccination of adult bison (Bison bison) with 6ϫ10 9 colony forming units (CFU) of Brucella abortus strain RB51 (SRB51) that had previously been vaccinated as yearlings with 1ϫ10 10 CFU of SRB51. Abortions or other adverse effects were not observed after SRB51 booster vaccination. At 10 wk after adult vaccination, pregnant and nonpregnant bison (nϭ65) were randomly selected for bacteriologic sampling of targeted maternal tissues during abattoir processing. Fetal tissues were also sampled in pregnant bison. The SRB51 vaccine was recovered from tissue samples of eight of 48 pregnant bison and none of 17 nonpregnant bison. In three of the eight culture-positive bison, SRB51 was recovered from fetal tissues. In three additional bison, one pregnant and two nonpregnant, B. abortus biovar 1 field strain was recovered from internal iliac or supramammary lymphatic tissues. Results of this study suggest the possibility that the SRB51 vaccine can be safely used to booster vaccinate pregnant bison in a Brucella-infected bison herd. Our data also reaffirms the potential for B. abortus field strains to persist in bison until attainment of reproductive age, despite extensive use of vaccination and serologic testing.
In early 2019, four stallions in the south of England tested positive for equine viral arteritis following routine prebreeding screening. Here, a team from Defra and the APHA describe the epidemiological investigation that was carried out to determine the origin of infection and the potential for its transmission across the country.
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