As one of 12 veterinary student research fellows, Kansas State University second-year veterinary student Lauren Herd is conducting a research project focused on anaplasmosis and effective dosing of chlortetracycline.

The Foundation for Food & Agriculture Research, in partnership with the Association of American Veterinary Medical Colleges, launched the Veterinary Student Research Fellowship to Address Global Challenges in Food & Agriculture in 2019 to encourage veterinary scientists to explore and better understand the complexities of animal production, improve animal welfare and enhance human health. The three-month fellowship creates opportunities for veterinary students to pursue research related to global food security and sustainable animal production, Kansas State said in an announcement.

Herd's research mentor is Kathryn Reif, assistant professor of diagnostic medicine and pathobiology in the College of Veterinary Medicine.

"Cattle that survive initial infection with Anaplasma marginale, the bacterial pathogen that causes anaplasmosis, become chronic carriers of the pathogen and can serve as future transmission reservoirs," Reif said. "Chlortetracycline is the only [Food & Drug Administration]-approved antimicrobial indicated for the control of active anaplasmosis in carrier cattle."

Reif said clinical anaplasmosis can reoccur in carrier animals if they become immunocompromised and their immune system isn't able to keep the pathogen under control. Cattle often experience transient periods of immunosuppression in a normal production season during estrus, calving, harsh weather conditions or concurrent infections.

For her project, Herd assessed whether chlortetracycline protects transiently immunosuppressed calves from developing clinical anaplasmosis. Reif said the results of Herd's research could affect the way producers manage this disease and will provide data related to the efficacy of the current legal dose.

"I am excited to be a part of this project because anaplasmosis has such a large economic impact on the U.S. cattle industry," Herd said. "Tetracycline antimicrobials, including chlortetracycline, are commonly used in cattle production. If chlortetracycline is not effectively controlling anaplasmosis at the current legal dose, it would need to be re-evaluated. It is important to assist producers in making the best economical decision for their herds as well as maintaining the efficacy of these medically important antimicrobials by ensuring they are used judiciously."

A conservative estimate is that anaplasmosis costs the U.S. cattle industry $300 million annually, Reif said.

"Use of chlortetracycline-medicated feed products is one of the most common ways producers control anaplasmosis in their herds; however, data from our lab demonstrate that there are many strains of Anaplasma marginale circulating in Kansas, and not all strains may be equally susceptible to chlortetracycline," Reif said.

"To be most effective, use of chlortetracycline should protect carrier animals from redeveloping clinical disease during times of transient immunosuppression," Reif said. "Lauren's project will directly evaluate this using two different A. marginale strains: one a historic strain isolated over 30 years ago, and a second strain isolated from a Kansas beef cattle herd two years ago that is still actively infecting cattle. We are excited to be doing research that contributes needed information to support U.S. -- and especially Kansas -- cattle producers."