Winter weather brings us an annual reprieve from many of the pests that damage our crops and infest our livestock. We often believe that extended cold will reduce potential insect pest populations later in the year.
In truth, these pests have adapted to overwinter in the soil or as egg masses on host plants, while some will retreat to a more temperate region of the country only to return once temperatures warm.
While these traditional pests have taken a brief break, there are others that are entering a season where they move to the top of the concern list.
The most significant winter pest of livestock is lice. Lice are species-specific, meaning that humans should not be concerned that they will be infested by lice from cattle, sheep, goats or poultry.
Life cycle
Lice can be classified as blood feeders (sucking lice) or biting lice that scrape material from the skin and base of hairs. They exist in three life stages: egg, nymph and adult.
Eggs are attached at the base of hairs and hatch after about two weeks. The nymphs take another three weeks to mature into adults.
An adult female will attach one to four eggs per day at the base of the hairs and live another three weeks. The time needed to move between growth stages and the average lifespan will vary between species.
The warmth provided by an animal’s body provides an ideal environment for the lice to thrive. As animals group together for added warmth, it is easy for lice to move from animal to animal.
While we can easily see the distress created by infestations with the continuous scratching resulting in hair loss and irritated skin, it is difficult to determine the economic impact of lice infestations. Cattle that experience infestations will have reduced performance, general unthriftiness and anemia.
Common lice of cattle
The department of entomology at the University of Kentucky, has a factsheet that provides a description of lice that commonly infest cattle (ETNFACT-512). They provide details on four species that are most prevalent in cattle, which include:
The shortnosed cattle lice is the largest of the common sucking lice species. Adults are about 2/10 of an inch long. They are found more frequently on mature animals where they prefer to feed along the top of the neck and around to the dewlap and brisket. As numbers increase, these lice can be found from the base of the horns to the base of the tail.
The longnosed cattle louse is more commonly seen on calves and dairy stock and rarely occurs in large numbers on mature animals. This louse is usually most abundant on the dewlap and shoulders but will spread over the entire body when animals become heavily infested. As the weather warms in the spring and numbers drop, they are usually seen last on the shoulders.
The little blue cattle lice are found most often in small clusters on the muzzle, neck and dewlap of mature cattle. Clusters of lice around the eyes cause heavily infested animals to look as if they are wearing glasses.
The cattle biting louse is most commonly found in colonies or “patches “ at the base of the tail, shoulders and top line of the back. Skin around colonies of this louse can have the appearance of mange lesions.
Prevention and treatment
Sound management practices are the base for lice control. It is always the first recommendation for all producers to have a valid Client-Veterinary-Patient-Relationship with their local veterinarian to assist with development and implementation of a herd specific animal health program.
Furthermore, animals that have all their nutritional needs met have been shown to better withstand infestations and respond to treatments. The added stress of winter requires an increase in energy and protein for livestock and these need to be considered in your winter-feeding programs.
Management of treatment and prevention options should be similar to controlling flies. It is best to implement preventative treatments in advance of infestation periods to limit population explosions and the subsequent animal health issues.
The specific products available to chose from will be dependent on the production status of the animals.
In nonlactating dairy cattle, you can use the organophosphates phosmet and chlorpyrifos as well as tetrachlorvinphos, coumaphos and diazinon. The macrocyclic lactones moxidectin, ivermectin, eprinomectin and doramectin can be used in all classes of cattle.
These products can be an injectable or pour-on formula. Most pour-ons will be effective against both biting and bloodsucking lice, and injectables primarily target bloodsucking species. You will need to consult the product label to determine if it is an option for your intended use.
Biosecurity practices will also assist in control. If you introduce new animals into the herd, you should consider them infested and quarantine the new arrivals separate from your resident livestock for a minimum of 30 days.
The trailer and all animal handling equipment should be sanitized after use.
