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Bovine anaplasmosis is an economically significant disease of cattle, with impacts including weight loss, spontaneous abortions, and death. Contemporary information about the epidemiology of this disease in Missouri is limited. Here, we present the preliminary results of an ongoing prospective serosurvey to evaluate the period prevalence of antibodies against Anaplasma marginale in serum from apparently healthy adult beef cows in Missouri. Given the lifelong persistence of most A marginale infections, seroprevalence is a reliable estimate of the proportion of carrier cattle within a population. Samples were collected from November 2021 through June 2022. Serum was collected with client consent by each herd's local veterinarian during a routine visit. Samples were tested at the University of Missouri Veterinary Medical Diagnostic Laboratory using a commercially available A marginale competitive ELISA (cELISA). A positive result was defined as ≥30% inhibition. Of the 509 individual cattle that were tested, 243 (47.7%) were seropositive. Thirty-two of 33 tested herds (97.0%) had at least one positive animal. Herds are located in 19 counties throughout Missouri. Participating clients completed a questionnaire which included 38 questions on herd characteristics, management practices, and client perceptions of anaplasmosis disease risk. Questionnaire responses indicated that most producers own cow-calf operations (93.5%) and describe their cattle as "commercial" or "a mixture of commercial and purebred" (90.3%). The median herd size in the survey was 58 cows. Of the 29 producers with open herds, 27.6% reported testing new cattle for infectious diseases before they were introduced to the herd. None reported testing for anaplasmosis. Eighteen producers (58%) reported seasonal feeding of chlortetracycline in a medicated mineral mixture for the control of anaplasmosis. One producer reported current use of the anaplasmosis vaccine, with a perceived reduction in clinical cases; however, only 4 of 15 cows tested in this herd had a positive antibody titer according to the cELISA. Eight producers (25.8%) reported changing needles between every animal, which is higher than expected and likely reflects selection bias (i.e., producers who volunteer for the study are likely to be concerned about anaplasmosis and may be attempting to reduce transmission in their herds). Results from the serosurvey confirm that bovine anaplasmosis is prevalent and widespread in Missouri. This serosurvey will continue through the fall of 2022. [ABSTRACT FROM AUTHOR]

Bovine anaplasmosis is an economically significant disease of cattle, with impacts including weight loss, spontaneous abortions, and death. The primary arthropod vector of anaplasmosis in the Midwest is the American dog tick, Dermacentor variabilis. Our research seeks to determine the prevalence of Anaplasma marginale, the causative agent of bovine anaplasmosis, among host-seeking D variabilis ticks in Missouri. To this end, ticks are collected at regular intervals from pastures on four beef grazing operations, each in a separate geographic region of Missouri. Pastures in our study are actively grazed by cattle and consist primarily of open grassland, with areas of grassland-woodland edge habitat. Ticks are collected with flannel drags over 750-meter transects, according to previously published methods. Following 38 collection attempts on 10 days in May and June 2022, 166 ticks have been collected. The most frequently encountered species during these attempts is the lone star tick, Amblyomma americanum (69.9%), followed by D variabilis (30.1%). Collected A americanum include 6 adult females, 12 adult males, and 98 nymphs. Collected D variabilis include 28 adult females and 22 adult males. Tick host-seeking behavior is influenced by a variety of factors including climatic and weather conditions, land cover, and host density. From each study site, hourly measures of precipitation, air temperature, relative humidity, and wind speed are recorded from onsite data loggers to identify abiotic drivers of tick abundance and phenology at these sites. In our study, D variabilis represents 30.1% of ticks collected thus far, whereas previous studies in north-central Missouri report D variabilis accounted for only 1% to 14% of ticks collected. This may be an effect of collecting from open grassland, instead of primarily forested areas as in the previous studies. Our findings indicate substantial local variation in tick composition depending on the site sampled. The site in north-central Missouri has yielded almost exclusively D variabilis, while sites in eastern and southwestern Missouri have yielded almost exclusively A americanum. To determine the prevalence of A marginale in host-seeking D variabilis ticks, our next steps involve nucleic acid extraction from collected ticks and real-time PCR to detect A marginale. Tick collection will continue until a sufficient sample size has been achieved. [ABSTRACT FROM AUTHOR]

Bovine respiratory disease (BRD) is one of the most important health conditions of beef cattle. Most research on BRD is focused on feedlots, but this disease is an important challenge to cow-calf producers as well. Missouri is one of the top cow-calf producing states in the U.S. This report describes viral and bacterial pathogens recovered from BRD cases diagnosed at the University of Missouri Veterinary Medical Diagnostic Laboratory (VMDL) from January 1, 2019 to December 31, 2021. During this three-year period, 386 cases of bovine pneumonia were diagnosed by a pathologist or identified as such by the referring veterinarian with subsequent detection of a primary BRD pathogen. Primary BRD pathogens were defined as Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, bovine viral diarrhea virus (BVD), bovine respiratory syncytial virus (BRSV), bovine parainfluenza virus 3 (PI3), or bovine herpesvirus 1 (BHV-1). Cases were only included if postmortem lung tissue was evaluated. Swabs were not considered in this analysis. Aerobic culture of lung was performed in 382 of 386 cases. In 27.5% of cultured cases, no significant pathogens were isolated. Significant bacterial isolates included M haemolytica alone in 25.1%, H somni alone in 12.6%, and P multocida alone in 8.9%. In 17.8% of cases, two or more of M haemolytica, P multocida, and/or H somni were isolated concurrently. The remaining 8.1% of cases were consistent with systemic infections (e.g., septic calves with Salmonella spp. isolated from multiple organs) or with secondary opportunists such as Trueperella pyogenes, Bibersteinia trehalosi, and/or Fusobacterium necrophorum. A complete respiratory PCR panel for BVD, BRSV, PI3, and BHV-1 was performed on 340 of 386 cases. In 80.6% of cases, no virus was detected. The most commonly detected viruses, either alone or in combination, were BRSV (12.1%) and BVD (7.6%). Additionally, Mycoplasma bovis was detected in 55.4% of the 112 cases in which PCR was performed. This should be interpreted with caution as M bovis PCR is typically requested at the pathologist's discretion and is not automatically included in the standard respiratory panel. During the same period, the detection rate of BVD persistent infections was 0.3% among 4,371 ear notches tested via immunohistochemistry or antigen capture ELISA, depending on the client's request. These numbers include out-of-state submissions and generally reflect previously reported industry averages. Etiologies of BRD detected in bovine lung submissions to the VMDL, which overwhelmingly represent cow-calf operations, are broadly similar in relative proportions to those previously reported in feedlot cattle. [ABSTRACT FROM AUTHOR]