Goat lice

photo Courtesy Jeff Johnson, Burnt Fork Veterin ry Clini Client

With spring comes lice in the goat barn

Ma ggie Hir schauer , Bitterroot Monarch Project Coordinator, MPG Ranch

If you’re lucky enough to own a goat or two, you may have recently noticed them rubbing—on everything!

They lean into fences with their shoulders and backs as they walk along. They scratch their heads and necks on barn walls or feeders. You might see this behavior in one or two animals and then suddenly, nearly everyone is joining in.

This isn’t some behavioral anomaly or a sign your goats are going stir-crazy. Late winter in the Montana goat barn is when the lice you didn’t know your goats were carrying become most active. While a new goat owner may be shocked and disgusted by this turn of events, most seasoned producers have experienced an infestation and know what to do about it. Novice producers need to educate themselves about external parasites— like lice—because they are just another aspect of goat husbandry.

The first thing that a new goat owner should know about goat lice is that they don’t like humans, and although on a rare occasion, you might find a louse crawling on you, they don’t want to be there and definitely won’t stay.

Lice are “species-specific,” meaning they can only complete their life cycle if they’re on the right

host, so your dog isn’t going to get lice from your goats and neither are you. Conversely, goats can’t get lice from your horse or your cat but generally acquire the parasite from another goat. Adult lice— if disengaged from their host—won’t survive longer than a day or two in the environment; however, the eggs can exist in bedding and continue to hatch over two to three weeks, so controlling an infestation means not only treating your animals but keeping a clean barn.

Since lice are opportunists who thrive on the easiest targets and usually show up on animals that are the most stressed—those “least thrifty” (underweight), internally parasitized, or subject to overcrowded conditions — keeping your goat herd healthy is the first step in controlling this external parasite.

There are two types of lice that infest goats: biting and sucking. Although accurate identification is only possible using a microscope to visualize the head (sucking lice have a head wider than the thorax; biting lice have a head much narrower than the thorax), goat owners can make an educated guess with careful examination of their animals.

Biting lice are light grey or tan in color and tend to be more mobile, while sucking lice bury their heads in the skin and so are more stable, their bodies darker brown from the blood they consume. In Montana, biting lice are more common than the variety that feeds on blood. They’re also more easily treated topically.

Sucking lice can be treated with external applications, but a systemic parasiticide (like Ivermectin) may ultimately be needed to clear up the infestation. Since this type of treatment entails using products that are not labeled for use in goats, you must contact a veterinarian for appropriate dosage. It’s a good idea to contact your veterinarian anyway to positively identify the louse and save you from the frustration of expending energy and expense on a treatment that doesn’t work.

Goat lice seem to be ubiquitous, but if you are lucky enough to have a herd that is free of these pests, prevention is the key to saving time and money. Newly acquired animals should be inspected for lice on arrival to the farm, treated if necessary and isolated from physical contact with other goats until a second application is effected,

usually two to three weeks later, to catch any young that may have hatched.

A single treatment—of any product—is rarely effective for stopping an infestation because no product currently available will kill louse eggs. When weather permits, shaving heavy-coated animals will minimize available habitat, since lice prefer the darkness and protection of that wooly undercoat. Shaving can also make it possible to spot an infestation at an early stage, when it’s easier to treat.

Some studies indicate that feeding a high-energy diet to your goats (without overfeeding them) can be an effective way of preventing an infestation. Lice populations are most active in winter, when daylight hours are shorter and goats tend to bed down together for warmth at night, so practicing good husbandry — keeping your barn clean, dry and warm and ensuring adequate space for the size of your herd — is another tool for controlling this pest.

Goat lice are persistent enough in the environment, however, that it is almost impossible to avoid the occasional infestation, no matter how careful the farmer. Fortunately, there are several options— both chemical and natural—for dealing with biting lice, in particular.

Two commercial chemical products, Cylence and Ultra Boss, are topical applications labeled for use against lice and other external parasites in goats. Both are approved for use on lactating and nonlactating goats; however, as with any chemical, they must be employed with care and awareness of their potential drawbacks.

The active ingredient in Ultra Boss, for example, can be extremely hazardous to the environment. According to the manufacturer’s own label, this product is a deadly toxin “…to aquatic organisms, including fish and invertebrates” and should only be applied “….in calm weather when rain is not predicted for the next 24 hours [to] help…ensure that wind or rain does not blow or wash pesticide off the treatment area…” or allow it to “…run off into storm drains, drainage ditches, gutters, or surface waters.” Ultra Boss is also “highly toxic” to bees, and the manufacturer cautions against applying in windy conditions under which it might “… drift to blooming crops or weeds while bees are

actively visiting the treatment area.” Further, the U.S. EPA has decided that permethrin, one of the active ingredients in Ultra Boss, is “…likely to cause cancer in humans if eaten.” Although anecdotal, a few goat dairy farmers have reported traces of the active ingredients in Ultra Boss showing up in laboratory tests of their milk. Even if the contamination was the result of environmental contamination from careless handling, rather than from the animal itself, users should definitely educate themselves on the potential hazards associated with this product before applying it. Also, please note that a similar product, called simply “Boss,” is NOT labeled for use in goats.

On the other hand, Cylence—the other chemical product labeled for external parasite treatment in goats—has an active ingredient (cyfluthrin) that is associated with far fewer cautions, according to the National Pesticide Information Center (http://www. npic.orst.edu).

More than half of the cyfluthrin in the application leaves the body within 24 hours and “…(a) round 98% is eliminated from the body within 1-2 days…” primarily through urine and feces. Unlike the chemicals in Ultra Boss, it is listed by the EPA as “not likely to be carcinogenic to humans,” and any residual amount of this product in the environment readily deteriorates in sunlight. It is “…immobile in soil and unlikely to leach,” nor does it dissolve easily in water, and it “…has a very low vapor pressure and is not expected to create fumes once dried.” Whereas neither the manufacturer’s label for Ultra Boss nor the NPIC fact sheets for the active ingredients in Ultra Boss expressly acknowledge its safety for use in pregnant goats, studies cited by the NPIC show cyfluthrin “…has not been found to cross the placenta in substantial amounts” or affect pregnancy rates. The use of chemicals for the treatment of lice in goats should be used not only with an awareness of environmental effects, their overuse should be avoided to prevent parasite acclimation to the active ingredients. Since pharmaceutical companies are currently devoting little or no research to the development of new parasitacides, we are limited to these two products now on the market, and acclimation to either is a possibility that should be concertedly avoided.

That means selectively treating animals only when necessary, rather than routinely treating animals as a “preventive” measure. The “80-20 Rule” states that “80% of the parasites in a herd are carried by 20% of the animals,” and this rule applies to external—as well as internal—parasites. Goat owners who wish to use one of these chemicals should positively identify those animals infected with adult lice and positively identify the species of lice before applying the treatment, and then treat only those animals who are actually infested. Some animals may be naturally more resistant while others carry a heavy infestation.

Dr. Richard Wall, a professor of Biological Sciences at the University of Bristol in the UK, points out that “…[t]he presence of at least some level of infestation may stimulate acquired immunity making the host less susceptible to future infection.”

Therefore, attempting to create an environment completely devoid of lice may actually exacerbate the herd’s susceptibility to infestation. Dr. Wall urges an integrated approach to parasite management that employs both prevention and a variety of treatments, using available chemical parasitacides only when necessary. photo Courtesy Jeff Johnson, Burnt Fork Veterin ry Clini Client

There are “natural” treatments currently in use by commercial organic producers as well as those who just wish to avoid using chemicals, although success with these methods has not been documented by scientific studies.

Historic documents from the library of the U.S. Department of Agriculture recommended the use of sulfur as a topical treatment for louse infestation in goats, and the Ohio Ecological Food and Farm Association (OEFFA) notes that “…(h)ydrated lime or sulfur dust bags are effective in killing lice.” Current USDA organic regulations “…permit the use of elemental sulfur in organic crop production as an insecticide (including acaricide or mite control)…” and suggest mixing elemental sulfur with diatomaceous earth for use as a dusting powder on louse-infested goats. Variations on the latter concoction claim the necessary additions of essential oils (e.g. tea tree, peppermint, lavender), but again, successful use

is anecdotal and without scientific evidence. The important point in using these treatments is that they can’t hurt the animal or damage the environment—they either work or they don’t. Careful monitoring of your herd is still necessary to ensure control of an infestation. If you are new to goat-ownership and your goats are doing the “infestation dance,” don’t despair, but be assertive. The longer you wait to tackle the louse-problem, the worse the infestation will become, and the more your goats will suffer.

Ask your veterinarian for advice and help in identifying the parasite, educate yourself on treatment options, and talk with other goat owners to see what works for them. Keep a clean, uncrowded barn, feed your goats appropriately, and be judicious in your use of chemical parasitacides.

Goat lice aren’t necessarily a problem; they are just another part of the experience of goat farming.

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