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.
Ticks are among the external parasites that may be found in greater number on cattle and other livestock as a result of recent rains.
“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, he said.
“Wet weather also creates prime conditions for tick infestations and ticks are the primary vector for anaplasmosis, which causes severe anemia and can kill livestock,” Machen said. “And tick bites can cause swelling, redness and localized infections.”
He said spring-born nursing calves are the biggest benefactors of anthelmintic treatment this time of year.
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,” he said.
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.
A side-by-side view of a horsehair worm and the cricket it infested.
“This will alert the producer that it’s time to switch classes of dewormers in the event the current dewormer is losing its effectiveness,” he said. “And using multiple classes of dewormers at the same time should be avoided unless advised by a veterinarian.”
Machen and Redden emphasized grazing management is a huge part of parasite management, noting stocking rate, forage availability and other aspects of grazing management play heavily into avoiding or minimizing internal parasites.
“There is also the aspect of genetic selection and looking for animals that are more resistant to these parasites,” Redden said. “It’s also good management to pay the most attention to those animals that are the most susceptible.”
They said each property must develop its own parasite management plan and no single program is appropriate for all operations, but plans should include good rotational grazing management, smart drenching and attention to genetic selection.