Lice Treatments in the Fall

In the last couple years across Western Canada there has been a “ large increase in lice issues especially sucking lice. With increasing lice detection producers are searching to find a new strategy that is effective yet doesn’t involve running cattle through the chute. “

By Roy Lewis DVM

There has been lots of talk and questions from producers and large animal veterinarians regarding the strategy to get better effective lice and internal parasite control. Especially in the last couple years across western Canada there has been a large increase in lice issues especially sucking lice. With increasing lice detection producers are searching to find a new strategy that is effective yet doesn’t involve running cattle through the chute. I hope this article may give you several options.

We know lice prefer the cooler temperatures of fall and winter to multiply and be evident and seen on the common locations of cattle. We also know how quickly in the spring lice can transfer to the calves and cause the irritation and blood loss to calves trying to nurse and grow. Timing of treatment has improved our results. Over time I believe we have gotten away from the very late fall and winter treatment. Cattle if processed early in the fall when temperature were often warm were treated out of convenience and we seemed to get away with it because of the residual properties of the ivermectin type products. On the flip side the freezing rate on these products is slightly below minus 10 degrees so applying slush affects absorption and perhaps efficacy. All things to consider when applying pour on products such as the macrocyclic lactones. Researchers are checking into an actual resistance developing but it is appearing that is possibly the case. One improvement will be to get the timing right moving from late summer or early fall treatment to late fall should improve things somewhat. This should apply to feedlot cattle as well so maybe summer placed cattle need to be lice treated at first implant as an example. More to keep track of from a management perspective.

Alternate products such as the Group 3 insecticides with names such as Boss, Saber, De-Lice or Cylence can be used effectively. Again timing is critical and they are all pour on products with slight differences is formulation. Basically, they are lower volume pour-ons and are not systemic products. They have no effect on internal worms so only effective for external parasites that being lice, but some are effective on ticks and mange as well. Ticks and mange mites are rarer but follow your veterinarian’s recommendations if these parasites are encountered. Some people are combining the late fall treatment of the ivermectin products together with an oral internal dewormer such as safeguard or another in the benzimidazole class. One then follows up with the other insecticide pour-ons later in the winter if see any clinical signs developing or as a routine to get a good treatment into them prior to calving. The other alternative is to go with the

category three insecticides twice as you need to get the eggs later when they hatch as they don’t have a long residual property. Either way should work fine but does involve most likely another treatment through the alleyway to apply products properly and get the best results. Others treat and watch for reoccurrence in the form of itching and hairloss.

You want to treat the whole herd as a unit at the right time so don’t leave any group untreated as a source of contamination and spread to the others. New introductions or purchases don’t forget to treat them on entry into the herd.

Other options include using cattle oilers and the products in them that are approved for cattle oilers. There are a few on the market with names like ectiban, pounce and others most having a pymethrin base. Many other products which were approved have been pulled from the market. I would use either canola oil or mineral oil in them to mix with the product. If use the oilers in the summer for fly control I would pulse treat in the oilers at the times when they are present and pulse treat in the late fall or early winter for lice. Then don’t treat until the time when lice stat to come back which has been January to February generally in Western Canada . Even the brushes in the pens are used by cattle and physically remove the lice and keep debris out of the hair. There is the issue of transmission, but lice spend their entire life cycle on the host so physically removing is a good thing.

Going forward we will find this two pronged approach to lice control is probably going to be necessary. Keep in mind with insecticides one must follow the label recommendations as unlike antibiotics prescriptions cannot be written by veterinarians for species not on the label. This makes if difficult for species like sheep or goats or bison where almost no insecticides have this species on the label. I am mentioning this in case any cattlemen also have these species on their farms and ranches

We have gone a long time really not having to deal with lice issues, but we need to address timing, alternating products and examining to see which lice are causing us problems in order to better determine the optimal treatment strategy.