Common Mites of Your Rabbit and Small Animal Part II: Cavy Lice

Cavy lice, sometimes referred to as "running lice", are host specific to guinea pigs (cavy) to survive. These lice are considered chewing lice, not sucking lice, and abrade the skin to obtain fluid.

Types

The most common type of louse is Gliricola porcelli. This is a slender, flattened, light colored (white to pale) insect about 1 to 1.5 mm in size with no wings. The lice can be seen moving through the fur near the skin and, in heavy infestations, around the eyes. Gyropus ovalis is less common and, but is also flattened, with no wings, and from 1 to 1.2 mm in size.

A third, and very rare species of louse, is Trimenopon hispidium. Light infestations are very easily missed because the lice are white and small. While heavy infestations are easily seen as they cause hair loss (alopecia), heavy scratching, and a rough coat.

Transmission

Lice seldom leave a host, and transmission normally happens through direct contact with another guinea pig or contaminated bedding or other equipment. A person carrying an infested animal can also transfer eggs or lice from their clothing to another animal.

Life Cycle

The life cycle of lice is about three weeks. Eggs attach to the hairs of the host, and a nymph will hatch three to 14 days later. Next, it will go through three nymph stages, each stage lasts one week and then molt into an adult and begin to mate continuing the cycle. Lice have no free-living stages and will die quickly in the absence of a host.

Symptoms

Lice are typically found around the head, neck, ears, and rump. Some infestations go unnoticed until the animal begins to exhibit physical signs that include:

1. Excessive scratching
2. Hair loss
3. Sores and scabs
4. Scaly, dry, and thickened skin

Lice are not normally life threatening, but young, elderly, and weakened animals will suffer more because their immune systems are not able to recover as quickly. A heavy infestation may be a symptom of some other underlying condition, including malnutrition, chronic disease, or immune deficiency. Debilitated animals often do not groom themselves, leaving the lice undisturbed causing severe infestation.

While G. porcelli and G. ovalis are specific only to guinea pigs, they are highly contagious between guinea pigs. It's important when introducing new pigs into an existing group that they are quarantined for at least 2-3 weeks and examined for lice.

Treatment

To positively identify an infestation, your veterinarian should perform skin scraping, combing, or acetate tape to confirm a microscopic diagnosis of the lice or eggs.

Since lice are transmitted by direct contact with the host, it is important to clean and treat both the environment while treating the animal. Other guinea pigs should be treated that may have come in contact with the infested animal even if they are not showing any signs.

Before any application, ensure that all cleaning supplies are safe for guinea pigs or ensure that the cleaning product doesn't come in contact with the animal(s) while in use.

Thoroughly clean and treat the areas where the animal(s) sleep and roam. This includes bedding, carpets, sofas, chairs and cushions, stuffed toys, etc. Make sure to vacuum all carpets and cushions with proper cleaning supplies to increase penetration of the powder carpet cleaner. Be sure to wash bedding, toys, and all cloth materials that may come in contact with animal(s). All clothes should be changed or laundered between handling guinea pigs.

Always consult with your veterinarian before beginning any treatment. Topical treatments of ivermectin or imidacloprid can easily kill lice, since they are biting not sucking pests. Treatment with imidaclopid is by weight, usually at 10 mg per pound or 0.1 cc per pound. An application will usually last for up to 30 days. Since ivermectin is a strong drug and absorbed through the skin, an accurate dose is required to avoid side effect—including death.

Insecticides in the class of benzoylphenylureas, such as diflubenzuron and triflumuron, have also been found to be effective in controlling chewing lice. Always carefully read labels to make sure it is appropriate for your animal and for proper dosage. It is always recommended to consult your veterinarian.

The best practice to prevent an infestation is to consistently clean the bedding, pens and cages, handwashing, and not sharing items that other guinea pigs (grooming equipment, toys, or bedding). To ensure safety for all your household animals, follow a regular grooming schedule, and consult with a veterinarian for regular health checks.

Cavy lice, sometimes referred to as running lice, are host specific and need a guinea pig to survive. These lice are considered chewing lice, not sucking lice, and actually abrade the skin to obtain fluid.

References

• Reeves, W. and Miller, M. Spot-on treatments of diflubenzuron and permethrin to control a guinea pig louse. Journal of Entomological Science, 44, 410-411.
• Scott, D., Miller, W., and Saunders, W.B. (2001). Dermatoses of pet rodents, rabbits and ferrets. Muller & Kirk's Small Animal Dermatology, (6th ed., pp. 1415-1453). Philadelphia, Pennsylvania: C E. WB Saunders Company.

Specialist Review

• Changlu Wang, Extension Specialist in Urban Entomology, Department of Entomology, School of Biological and Environmental Sciences, Rutgers, The State University of New Jersey

Based on the work of Deborah Cole, 4‑H Agent, Atlantic County, Jeannette Rea-Keywood, 4‑H Agent, Department of 4‑H Youth Development, and Mary Ann Metz, 4‑H Program Assistant

July 2025