Excessive rains in many parts of the state have Texas A&M AgriLife Extension Service experts concerned about the possibility of increased parasite and pest activity with livestock.

“Wet weather creates conditions favorable for parasites to infect animals on pasture,” said Dr. Rick Machen, AgriLife Extension livestock specialist based in Uvalde.

Machen said with the recent wet weather the biggest challenge for cattle is the brown stomach worm. Affected animals lose weight and in severe cases may die of overwhelming clinical ostertagiasis, a disease characterized by severe diarrhea, edema and serious weight loss.

“The anthelmintic, or treatment, for this parasite can be used orally, topically or through injection,” Machen said. “Generally, I’ve found that for ease of application most producers prefer the topical or pour-on application.”

The pour-on application has the further advantage of providing some external control of horn flies and face flies as well as ticks.

The recent rains are also likely to create some parasite problems for sheep flocks, said Dr. Reid Redden, AgriLife Extension state sheep and goat specialist at San Angelo.

Redden said internal parasites such as roundworms and coccidia can occur in sheep during wet periods. Most flocks have some level of parasitic infection but symptoms from these infections really tend to show up during high rainfall as the amount of parasites build up and cause health issues.

Redden said the best control is preventive, but dewormers or anthelmintics can enhance control measures, especially when administered before the parasite’s eggs contaminate the pasture.

“These drugs can be a powerful tool, but for long term-parasite management, dewormers cannot be the only preventative treatment,” he said. “If using anthelmintics, treat only the animals that need treatment in order to reduce the chance of the parasites building up a resistance to the dewormer.”

He said producers can also conduct a fecal egg count reduction test to determine if the dewormer is working.

Mike Merchant, AgriLife Extension urban entomologist in Dallas, said he has been receiving inquiries about worms appearing in puddles near horses. These may or may not be feeding worms or parasites, he said.

“Horsehair worms are among the parasites that tend to be around horses and are more prevalent when there’s a lot of rain,” Merchant said. “These parasites actually infest insects like crickets and grasshoppers. Parasite eggs ingested by the insect develop inside, becoming a thin, long worm several inches long.”

 “Coincidentally, insects, including those parasitized by horsehair worms, also frequently fall into the water of horse troughs and die,” Merchant said. “Horsehair worms, which emerge from parasitized insects, are often seen swimming in water troughs and are long and thin, and that’s how they got their name.”

Several publications related to livestock parasites — internal and external – can be found at the Texas A&M AgriLife Extension Bookstore at http://www.agrilifebookstore.org/. (Enter the word “parasites” in the search field.)

Lonnie Henschke is an Erath County extension agent. His column appears weekly and online at yourstephenvilletx.com.