UW scientists investigate coccidia resistance in beef cattle

UW scientists investigate coccidia resistance in beef cattle

            “Now is the time to address the ever-present challenge of coccidiosis in cattle rearing on an evidence-based treatment regime instead of fostering resistance development by untargeted drug use,” says Berit Bangoura, assistant professor, Department of Veterinary Sciences, University of Wyoming College of Agriculture and Natural Resources.

            Bangoura and her colleagues have designed a study in hopes to bring major advancements to controlling coccidia in cattle.

            “This pilot study will deliver important insights into the efficacy of anticoccidial drugs used every day in the U.S. cattle industry,” says Bangoura. “Any resistances detected would strongly confirm prior findings of lacking drug efficacy in the field and would have a great impact on the cattle industry.”

            She continues, “Producers would have to ensure the anticoccidial treatment they apply is the right choice for the coccidia field strains on their operations.”

Coccidia in cattle

            “Coccidia represents a cluster of parasites that harm livestock including cattle, sheep, goats, poultry and rabbits,” Bangoura says. “Coccidia mostly reside in the gut of one specific animal species and damage the gut mucosa.”

            She continues, “These parasites provoke diarrhea, fluid and weight loss, and reduced animal growth and can cause death.”

            She notes the parasite is excreted with feces and can infect the next host by feed contamination.

            Bangoura explains there haven’t been any recent studies regarding coccidia presence in U.S. cattle operations. Studies in Europe showed upwards of 95 percent of cattle operations reported coccidia presence.                    

            She notes young cattle such as calves, heifers and young steers are the most prone to the disease associated with coccidia presence.

            Long-term effects like lower final adult body weight and prolonged increased feed costs occur in affected animals and herds.

Resistance

            “The cattle industry relies heavily on chemical drugs (anticoccidials) to alleviate the animal health and financial implications of coccidiosis,” Bangoura explains. “Unfortunately, all four anticoccidials available on the U.S. market have been sold and used for up to 50 years, and they are used every day on most cattle-rearing farms.”

            She continues, “This implies parasites are under constant treatment pressure not only in the U.S., but worldwide and may develop resistance.”

            She notes there are no studies investigating the current level of drug efficacy against coccidia.

            “Studies in chickens show coccidia can develop resistance within a few years, and we know that in poultry there are many multi-drug resistant strains widespread in the field,” says Bangoura. “Anecdotally, we know producers are dissatisfied with the efficacy of the anticoccidial treatment they apply to young cattle.”

            She notes there are a variety of factors contributing to resistance including under-dosing of the drug or a too-short treatment period. However, diagnostic fecal samples submitted from operations using a strict regimen of anticoccidial drug treatment often contain pathogenic coccidia, some in alarming amounts.

Study

            “In light of these field findings and the known economically threatening scenario in chickens, we developed the plan to investigate the resistance situation in cattle coccidia,” says Bangoura.

            She notes the following are major questions driving their research: Are these bovine parasites already resistant against our few available anticoccidial drugs? How widespread is the resistance? Is there any drug that should be preferably used?

            The team polled Wyoming and Colorado cattle producers using standardized questions regarding their management and husbandry conditions.

            “We visited the farms of those willing to cooperate and collected fecal samples from different age groups of young cattle,” Bangoura explains. “The feces were analyzed for coccidia, and positive samples were stored and the parasites purified from the fecal matter.”

            She notes the first important step is the development of a suitable cell culture readout assay that can serve as the basis for the drug resistance assessment in cattle coccidia. No such test system is known to be available at other laboratories.

            “The study design includes the infection of bovine cell cultures with the collected cattle coccidia strains. In the cell culture setup, the parasites will invade the bovine cells and start to multiply within them, just as they would in the gut of young cattle,” she explains. “We can develop an assay to test drug efficacy without the need of extensive animal experiments.”

            She continues, “The cell cultures are grouped in parasite-infected, untreated cultures allowing the parasites to multiply without limitations and infected and drug-treated cultures.”

            She explains from the control cultures, we can measure the parasite number formed in a given time if optimal conditions exist. In the other cell cultures, parasites are challenged with the different drugs and expected to grow and multiply much less if the drugs are effective.

            “In the end, the genetic material from each cell culture will be isolated and tested. We can calculate the number of parasites per treatment group and know if the treatment was able to reduce the parasite growth significantly,” says Bangoura.

Prevention by management

            “Hygiene is key in managing coccidia presence on an operation,” says Bangoura. “We also need to look at specific operations to see if they have a dangerous or harmless variety of coccidiosis causing pathogens.”

            She notes most management strategies will depend on the specific setup of individual operations.

            “The first step includes a lot of diagnostics to determine the root of the issue and which cattle are infected,” says Bangoura. “We don’t want to mingle infected calves with clean calves.”

            She also explains good overall health is key in cattle’s ability to fight off infections such as those caused by coccidiosis, which cannot be vaccinated for.

            She continues, “When we vaccinate against other diseases, the calves will be better able to fight off other infections because their bodies aren’t trying to deal with numerous issues at on e time.”

            This article was compiled from information in the article titled, “Scientists investigate anticoccidial drug efficacy,” which was featured in University of Wyoming Ag News on Oct. 7, 2019.

Callie Hanson is the managing editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.