Evaluation of anaplasmosis on commercial beef bull breeding soundness

Purpose and Brief Explanation:

Anaplasma marginale is a tick-borne blood pathogen of cattle which causes the disease bovine anaplasmosis, a disease conservatively estimated to cost the U.S. cattle industry $300 million per year. Anemia is the hallmark clinical sign of anaplasmosis, and may lead to other clinical signs including fever, jaundice, reproductive losses, and generalized lethargy. Cattle that recover from clinical disease rarely clear this pathogen and become chronic carriers that may relapse with clinical signs in times of increased stress. Anaplasmosis is endemic in the United States (U.S.), including Kansas where approximately 50% of beef cattle herds are actively infected. Treatment and management of anaplasmosis is heavily reliant on the use of tetracycline antimicrobials and vector control products, proper disinfection of blood-contaminated processing instruments, and active biosecurity.

The impact of bovine anaplasmosis on cattle reproduction parameters is largely understudied, with the majority of available studies examining the impact of anaplasmosis on cows. Few studies have examined the effects of acute and chronic anaplasmosis on breeding soundness in bulls. Mature bulls displaying clinical signs such as pyrexia and anemia are more likely to fail breeding soundness exams (BSE). However, it is unknown whether breeding bulls persistently infected with A. marginale (not showing overt clinical signs of disease) are more likely to have reduced breeding success compared with uninfected bulls.

The objective of this study is to compare breeding soundness exam (BSE) results between bulls persistently infected with A. marginale and uninfected bulls. For this study, bulls undergoing routine BSEs will be enrolled. The following will be evaluated for each enrolled bull: i) breeding soundness exam results; ii) anaplasmosis infection status; and, iii) packed cell volume. The cost of the BSE will be subsidized for Kansas cattle producers and costs associated with anaplasmosis testing results and packed cell volume analysis will be covered by the study. The information gathered from this study will benefit cattle producers and beef cattle veterinarians alike in determining the economic and health impact of anaplasmosis carrier status on breeding bulls.

Clinical Protocol: All bulls enrolled in this study will be included in two parts:

  1. Breeding soundness examination (BSE) – All bulls will undergo BSE as part of a standardized protocol in place by the investigators as defined in the Society for Theriogenology Manual for Breeding Soundness Examination of Bulls, second edition. This includes a general physical examination, and collection of semen via electro ejaculation to determine sperm motility; morphology; and semen concentration; as well as to evaluate the characteristics of the external genitalia.
  2. Anaplasmosis carrier status – All bulls enrolled will have approximately 12 to 20 mL of blood collected via tail vessel or jugular vein. Phlebotomy site will be at the discretion of the attending veterinarian. Blood samples will be used to evaluate anaplasmosis infection status and packed cell volume.

Eligibility: Apparently healthy, beef bulls, older than 15 months of age, intended for breeding and undergoing routine breeding soundness examination are eligible for this study.

Fees for Services: The cost of the BSE will be subsidized by this study (up to $40/bull) for Kansas cattle producers. For non-Kansas residents, the cost of the BSE will be at the owner’s expense. All anaplasmosis testing and packed cell volume evaluations will be covered by this study. Owners are responsible for all other cost including, but not limited to, consultation fees, additional veterinary services not related to BSEs or the study, additional diagnostics, and treatments.

Contact for more Information: Kris Richardson, Clinical Trials Coordinator at the Veterinary Health Center. Email: ClinicalTrials@vet.k-state.edu Phone: (785)-532-3046