Lessons learned treating outbreaks valuable to others

Treatment plan for condition includes vaccines and antibiotics in feed, despite veterinarian’s concern about introducing antibiotic resistance

A perplexing case of calves suffering from swollen joints on an Alberta purebred operation required some serious detective work for the herd veterinarian.

Contagious polyarthritis was the diagnosis, but the treatment plan was devised through experimentation and extensive consultation, said veterinarian Todd Gunderson.

“The chances that you are going to see this particular disease in your herd is pretty slim,” he said at a beef cattle conference organized by the University of Calgary faculty of veterinary medicine June 18-19.

“The tools that we used could be applied to any outbreak situation.”

The condition is also known as joint ill. Bacteria enter the body through the naval of young calves, and infection moves to areas of the body with slow blood flow and settle in joints.

In March, the producer noticed six, 10- to 14-day-old calves with swollen joints and severe lameness.

He tried a variety of treatments, and while some calves were eventually able to move, others had to be euthanized. Laboratory analysis de-tected mycoplasma bovis, a bacterium that is resistant to many products and difficult to culture.

Euthanized calves showed severe damage to the growth plates, but the lungs had no evidence of mycoplasma pneumonia.

Enhanced naval hygiene practices were introduced, and vaccines for IBR and bovine respiratory disease were recommended.

Tetracycline was added to the cows’ feed to reduce dam-to-calf transmission. This decision was not made lightly because there was concern about killing bacteria in the cows’ rumens and introducing antimicrobial resistance on the farm.

The cows were fed three grams of antibiotic each per day: two weeks before calving and two weeks after the last calf was born in the spring of 2015. No swollen joints, scours or respiratory diseases were seen that year.

Gunderson did not favour feeding antibiotics but decided this might be the best approach to save a calf crop.

“There is a cost to everything you do, and there comes a point where we reach the end of the positive cost benefit ratio,” he said.

“We are putting on the pressure to extend life and improve quality of life, but there are going to be some costs when it comes to antibiotic resistance,” said Trish Dowling of the Western College of Veterinary Medicine at the Calgary conference.

Resistant bacteria showed up almost as soon as antibiotics were introduced 60 years ago. The episodes of resistance are increasing.

Bacteria such as mannheimia haemolytica, which is responsible for bovine respiratory disease, are showing resistance, she said.

“What is really concerning is that multi-resistant Mannheimia isolates are showing up across the spectrum of antibiotics we use in cattle.”

A published study from Kansas State University said about five percent of the bugs were resistant to several drugs in 2009. By 2011, 35 percent showed resistance and by 2014 it was 70 percent.

High levels of resistance to Nuflor have appeared in the last couple years, but ceftiofur (Excenel) has shown no evidence of resistance at this time, she said.

It is common practice to give new feedlot arrivals a shot of a long lasting antibiotic to prevent BRD, but that may have to be revisited.

“We have used these drugs as a management tool, and it looks like we’re not going to be able to do that anymore. We can only use them as an intervention,” Dowling said.

Dorothy Erickson, manager of veterinary services for cattle at Zoetis, said manufacturers realize the consequences of antibiotic use.

Animal agriculture has a role in using antibiotics responsibility.

“Sick animals deserve treatment as well,” she said.

Zoetis tracks resistance levels of bacteria that are responsible for bovine respiratory disease. Data collected from 2000-14 show resistance levels within the Mannheimia community are increasing each year.

New Health Canada rules that will be introduced next year stipulate growth promotion claims must be removed from drug labels.

Some products only have growth promotion claims, so those will be removed unless the company can prove the drug has other values.

Veterinary oversight for any antibiotics used in feed and water will also be required.

Canada has not been as strict as some other countries.

“There is more talk about Canada having to play catch up in its regulations for antibiotic use and prescribing,” Erickson said.

Rules governing prescriptions, prophylactic treatment, importation of own use products and extra label use are all coming under more scrutiny.

This means producers must look for alternatives to antibiotics, better vaccine programs and more diligent biosecurity to keep out disease.

“We cannot count on continuous development of new products as resistance occurs,” Erickson said.

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