Does Larry Hawkins find any humor when it comes to lice and livestock?
“I guess it would be easy for me to start scratching my head and say something like, ‘Lice are an itchy topic.’ Is that humorous enough?” he asked.
“If not, what about: ‘A lice louse is lousy.’ Yes, that might sound kind of corny, but I believe it’s true. They can cause some pretty bad problems.”
Beef and dairy cattle operators along with horse owners who don’t want lousy lice to cause lousy problems for their animals and their bank accounts can take a variety of steps to control this pesky parasite.
Hawkins, senior technical services veterinarian for Bayer Animal Health, said that good lice control starts with good cattle health.
“If your cattle are receiving proper nutrition and if they are in good health overall, that helps to protect them from a variety of diseases, flies and insects, including lice,” Hawkins said.
But no matter how healthy your cattle and horses are, they are susceptible to lice because of the parasite’s lifecycle (see October post titled “Battle lice by knowing their lifecycle”), and also because lice are so difficult to control.
Since lice spend most or all of their lifecycle on a host animal, it seems that control efforts would be easy. In part, they are, but the lifecycle can make it difficult unless operators get a jump on the parasites early in the season and then stay on top of things.
Hawkins said that early in fall, cattle often do not show indications of lice, even though the parasites are typically present in small numbers.
“Populations often begin to build in late October, November and December, then you start seeing severe outbreaks in January,” he noted. “Knowing this can help you get on top of problem outbreaks. It can help you eliminate the high numbers that you often see in January and February.”
Hawkins said that it’s typically easy to kill adults and nymphs but much more difficult to kill eggs.
“Louse control often takes at least two treatments. The first treatment kills the adults and nymphs. But most pour-on products registered for louse control, including pyrethroids, do not kill
the eggs, so you have to come back in about two weeks with another treatment after the eggs hatch,” he said.
If you wait more than three weeks, however, your cattle will not only have adults and nymphs, which can be controlled by this second treatment, but also another batch of eggs, and these eggs will produce yet another generation of lice.
“Then it potentially becomes an exponential population increase through the fall and winter,” Hawkins said.
Doug Ross, senior technical services entomologist for Bayer Animal Health, explained that eggs hatch in about eight to 12 days, and the newly hatched nymphs become egg-laying adults in another one to two weeks.
Knowing this gives you a window of opportunity for good control, but pay close attention to timing.
“It is critical to make a second application after eggs that survived the initial treatment have hatched, but before nymphs hatching from these eggs become egg-laying adults. The second application should be made no later than two to three weeks after the first treatment,” Ross said.
Hawkins emphasized: “If you don’t follow this timing and if you don’t treat all animals, you potentially lose all the value of a double treatment.”
Producers can take additional steps to protect their cattle from lice, and new technology is also available that will allow them to better control lice by killing adults, nymphs and eggs with one treatment (see article “Technology aids in lice control”).