Question: 

We recently had some cats at our shelter who had lice.  We have not ever seen this before and so understandably the staff had a lot of questions:

• How common is it?
• Is it contagious to children or dogs?
• Does the Lyme dip only kill the lice or does it also kill the eggs and larvae?
• What is the life cycle of cat lice?
• Will canine Frontline Plus kill feline lice? The packaging states kills "chewing lice".
• What advice, recommendation or precautions should we give to the potential foster home? They are in ISO now.
• Now that they have been Lyme dipped can they safely be sent for spay/neuter?
• What is the best way to treat the remainder of the cats on the property? We are waiting to find out how many are friendly vs feral. They all need spay/neuter. All live outdoors.
• What is the best way to rid the "living area" of the problem?

Answer: 

Feline lice is a rare finding and usually associated with neglected cats or those living in poor husbandry conditions.  It is very contagious between cats, so if there is one infected cat, there is a good chance the others are infected as well.  Luckily, lice are species-specific so dogs and people are safe from contracting them.

Lime sulfur dip is very effective in killing nymphs and adults, but not reliable in killing eggs.  Lice have an incomplete life cycle (unlike fleas that have a larval and pupal stage), where the eggs (nits) hatch into nymphs (mini-adults), which then go through several molts to become adults.  The complete life cycle is about 3-4 weeks depending on the environment, and occurs on the animal. I do not know of any insecticide that will effectively penetrate the eggs, so repeating treatments every two weeks for a total of 2-3 treatments is recommended. 

Precautions that a foster home should take: have their resident cats on monthly flea control (Advantage, Frontline, Revolution, etc.).  As long as there are no underlying medical conditions (e.g., anemia caused by lice infestation), a lime sulfur treated cat is okay for surgery. Lucky for us, lice are susceptible to pretty much anything that fleas are susceptible to, including Frontline.  Frontline spray (as well as Top Spot and Plus) is a very effective way to get rid of lice.  This may be an option for the remaining feral cats.  You do not necessarily have to touch the cat, but if you can get close enough to spray it, it will help. 

As far as the environment, anything that can be tossed in the laundry, should be.  Otherwise, just treating the cats every two weeks should take care of the infestation, as long as the cats are not re-infecting each other. Another option may be placing flea collars on the affected cats if you can get the collars on them.  I am not a huge fan of flea collars or using pyrethrin-based products on cats, but if the cats keep the collars on long enough (2+ weeks) to kill off the lice and newly hatched nymphs, this will take care of the problem too.  If you must use an environmental product, use one that is targeted towards fleas and that is safe for cats.

For more information on lice – please see the CAPC website.

Cristie YJ Kamiya, DVM, MBA
Resident, Koret Shelter Medicine Program
Center for Companion Animal Health
UC Davis School of Veterinary Medicine
www.sheltermedicine.com
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