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Strategic deworming strategies can help producers get a handle on resistance parasites

by Wyoming Livestock Roundup

In the future, producers may have to select goats that can tolerate parasites.

Brian Vander Ley, veterinary epidemiologist with the Great Plains Veterinary Education Center at the University of Nebraska, tells producers parasite resistance is here to stay.

“Timed, blanketed deworming does not work anymore. Goats cannot be cured of parasites,” he says.

Deworming products

With only two goat deworming products remaining on the market that still work to treat parasites, Vander Ley says chances are slim of another product becoming available. The parasites have become immune to many dewormers, so some of the dewormers no longer work.

“Resistance is defined as the inability of the deworming product to reduce the fecal egg population by 95 percent,” he explains.

After a deworming product is used, Vander Ley says 100 percent of the goats with resistant parasites will be left on the pasture to shed eggs from resistant worms.

  “While we still have a few products left that work, we need to use that time to develop goats that are tolerant to parasites,” he says.

Parasite infections

“Only 20 percent of the goats in a given population are infected with parasites,” Vander Ley continues. “Producers should only deworm the goats that are infected.”

Isolating infected animals is not recommended because it creates another location on the farm where animals can shed eggs and create more problems.

“Producers should leave those goats in the herd, so they can shed eggs that will mate with resistant worms and hopefully help develop animals that can tolerate parasites,” he explains.


“Don’t blanket deworm all of the animals. It only creates resistant worms, especially in a new area,” he continues. “Blanket deworming can even kill the kid goats, if they are in that area, because they are exposed to nothing but resistant worms, and they don’t have the immunity to fight such an infection.”

Vander Ley indicates to producers that deworming products should only be given to goats orally by mouth.

“Never use a pour-on or an injectable with goats,” he explains.

Using pour-ons or injectables spread out the duration of the dewormer, killing all of the worms except the resistant ones.

“The duration is so long, it actually selects for resistant worms,” he says.

The veterinarian recommends administering the dewormers in combination with one another and alternating classes for the most impact.

He also recommends putting as much selection pressure on parasite tolerance as possible.

Other diseases

When producers import goats into their herd, Vander Ley encourages them to do their research on parasites, as well as other diseases that can affect goats.

“Producers should test their current herd before they worry about what they are bringing in,” he says.

“Quarantine and test all new animals, and then monitor the herd routinely. Screen any sick animals and post any goats that have died,” he recommends.

Producers should also keep in mind that some diseases can be transmitted from goats to people.

Ringworm and sore mouth can infect humans, but the worst one, according to Vander Ley, is Q Fever. In immuno-suppressed people, it can cause heart valve disease and blood vessel abnormalities. In healthy people, it typically causes flu-like symptoms.

“A lot of goats shed this bacterium, especially at kidding time,” Vander Ley says. “Ranchers should wear gloves, especially if they are working with the placenta.”

“If producers have animals that die, keep it from being a complete loss by gathering as much information from that animal as possible,” he explains. “Get a post-mortem exam to gather as much information about disease potential, and other problems in the herd.”


By identifying susceptible populations, producers can minimize and even eliminate exposure risks. Water tanks should also be cleaned regularly, Vander Ley recommends.

“Tanks are an ideal location for disease to spread. We use tanks as a sampling area for viruses and to detect viral shedding,” he says.

Producers are also encouraged to avoid using feeding equipment for manure handling and to feed hay off of the ground.

Lastly, Vander Ley encourages fly control, because flies can spread disease.

Vaccines also need to be given at the right times.

“Do not vaccinate sick animals,” Vander Ley warns. “It can make them a lot worse.”

“Treatment decisions should be made by the producers and their veterinarian, but choose effective treatments,” he cautions.

Gayle Smith is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to

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