Mycoplasma bovis Infections in Free-Ranging Pronghorn, Wyoming, USA

Pathology of Chronic Mycoplasma ovipneumoniae Carriers in a Declining Bighorn Sheep (Ovis canadensis) Population

Bighorn sheep (Ovis canadensis) across North America commonly experience population-limiting epizootics of respiratory disease. Although many cases of bighorn sheep pneumonia are polymicrobial, Mycoplasma ovipneumoniae is most frequently associated with all-age mortality events followed by years of low recruitment. Chronic carriage of M. ovipneumoniae by adult females serves as a source of exposure of naïve juveniles; relatively few ewes may be responsible for maintenance of infection within a herd. Test-and-remove strategies focused on removal of adult females with evidence of persistent or intermittent shedding (hereafter chronic carriers) may reduce prevalence and mitigate mortality. Postmortem confirmation of pneumonia in chronic carriers has been inadequately reported and the pathology has not been thoroughly characterized, limiting our understanding of important processes shaping the epidemiology of pneumonia in bighorn sheep. Here we document postmortem findings and characterize the lesions of seven ewes removed from a declining bighorn sheep population in Wyoming, USA, following at least two antemortem detections of M. ovipneumoniae within a 14-mo period. We confirmed that 6/7 (85.7%) had variable degrees of chronic pneumonia. Mycoplasma ovipneumoniae was detected in the lung of 4/7 (57.1%) animals postmortem. Four (57.1%) had paranasal sinus masses, all of which were classified as inflammatory, hyperplastic lesions. Pasteurella multocida was detected in all seven (100%) animals, while Trueperella pyogenes was detected in 5/7 (71.4%). Our findings indicate that not all chronic carriers have pneumonia, nor do all have detectable M. ovipneumoniae in the lung. Further, paranasal sinus masses are a common but inconsistent finding, and whether sinus lesions predispose to persistence or result from chronic carriage remains unclear. Our findings indicate that disease is variable in chronic M. ovipneumoniae carriers, underscoring the need for further efforts to characterize pathologic processes and underlying mechanisms in this system to inform management.

A serological survey of pathogens associated with the respiratory and digestive system in the Polish European bison (Bison bonasus) population in 2017-2022

BACKGROUND

The European bison (Bison bonasus) is a near threatened species and requires health monitoring. The aim of the present study was to determine the prevalence of antibodies to pathogens known to cause respiratory and digestive illness in ruminants.

RESULTS

In the studied 328 European bison, the highest seroprevalence was observed for Bovine herpesvirus-1 (BoHV-1) (50.27%), Bovine Coronavirus (BCoV) (26.36%), and Bluetongue Virus (BTV) (12.83%). For Mycoplasma bovis strains and Bovine Viral Diarrhea Virus (BVDV), positive results were rare. Interestingly, a higher prevalence of BTV antibodies was noted in the northeastern populations and older animals.

CONCLUSIONS

Our findings indicate that the Polish European bison population appears to have considerable contact with BoHV-1; however, this does not appear to be of great significance, as clinical symptoms and post-mortem lesions are rarely noted in Polish European bison population. The high seroprevalence of BTV in the north-east of Poland is an ongoing trend, also noted in previous studies. It is possible that European bison may perpetuate the virus in this region. This is the first report of antibodies for BCoV in European bison.

SOURCE AND SEASONALITY OF EPIZOOTIC MYCOPLASMOSIS IN FREE-RANGING PRONGHORN (ANTILOCAPRA AMERICANA)

Mycoplasma bovis is an economically important bacterial pathogen of cattle (Bos taurus) and bison (Bison bison) that most commonly causes pneumonia, polyarthritis, and mastitis. It is prevalent in cattle and ranched bison; however, infections in other species are rare. In early 2019, we identified M. bovis in free-ranging pronghorn (Antilocapra americana) in northeastern Wyoming. Here, we report on additional pronghorn mortalities caused by M. bovis, in the same approximately 120-km2 geographic region 1 yr later. Genetic analysis by multilocus sequence typing revealed that the mortalities were caused by the same M. bovis sequence type, which is unique among all sequence types documented thus far in North America. To explore whether pronghorn maintain chronic infections and begin assessing M. bovis status in other sympatric species, we used PCR testing of nasal swabs to opportunistically survey select free-ranging ungulates. We found no evidence of subclinical infections in 13 pronghorn sampled from the outbreak area (upper 95% binomial confidence limit [bCL], ∼24.7%) or among 217 additional pronghorn (upper 95% bCL, ∼1.7%) sampled from eight additional counties in Wyoming and 10 in Montana. All mule deer (Odocoileus hemionus; n=231; upper 95% bCL, ∼1.6%) sampled from 11 counties in Wyoming also were PCR negative. To assess the potential for environmental transmission, we examined persistence of M. bovis in various substrates and conditions. Controlled experiments revealed that M. bovis can remain viable for 6 h in shaded water and 2 h in direct sunlight. Our results indicate that environmental transmission of M. bovis from livestock to pronghorn is possible and that seasonality of infection could be due to shared resources during late winter. Further investigations to better understand transmission dynamics, to assess population level impacts to pronghorn, and to determine disease risks among pronghorn and other ungulate taxa appear warranted.