Deworming Feral Cat Colonies

Treating an individual cat for multiple days is not easy, and it's nearly impossible to do effectively in a cat colony! The feral cat colony is a herd, and cats are very social with each other. Therefore, when one cat has an infection or parasite, the rest have been exposed to it. This is true for ear mites, mange, lice, intestinal parasites and respiratory infections! Some or most cats cannot be handled, and medicating only the individual and leaving the herd untreated won't be effective because the issue will return. Success is achieved by effectively treating all of the cats through their diet and getting all to take the medication.


Parasites are the first place to start because they do the most damage and removing them is where you get the most results for your money! Parasites eat the cat's necessary nutrition, and they beat down the immune system, making respiratory infections more prevalent. The result is rough hair coats and skinny cats.


Most ear mite treatment programs fail because of the mite eggs, not because the adults were not killed. Mites and ear mites are easy to kill in the adult stage, but it's nearly impossible to get the egg. The eggs hatch in 7-10 days and start reproducing.

Ivomec 1% is very effective at getting rid of ear mites, mange mites and lice. The key is getting one good dose in them and repeating in 7-10 days. It is essential to get the mites that hatch before they can start reproducing. If you don’t, the mites will repopulate and be just as bad in 6 weeks.

Ivomec is also excellent at killing roundworms and helping with hookworms. These feral cats are carrying lots of roundworms, the #1 intestinal parasite issue from hunting mice and birds. (Ivomec often sees resistance issues in our house pets where low dose Ivomec is used. Routine deworming as kittens by breeders and heartworm meds is the usual cause. Neither of these are a worry in feral cats that have never seen Ivomec.)


Treating and deworming in milk replacer is inexpensive and cats seem to like it. If a cat has never had milk replacer given to them in the past, it can take a little time for them to warm up to the idea. Most cats have a built-in trust “issue” that helps them to be such good survivors. It takes about 3 days of tasting something new for a cat to trust it. Start the process with unmedicated milk replacer to establish trust (most will drink it after 3 days of sniffing, testing, and looking at it).

The next step is to establish a count of how many cats are going to be treated. After feeding milk replacer (All Star) in several pans at the same time for three days and all the cats are coming up for milk, get a count of how many cats are in the colony. Next, establish how much medication to add to the milk. The average feral cat weighs eight pounds, so multiply the number of cats by eight to get total weight. (For example, if there are 20 cats, then the needed dose of dewormer is for 160 pounds. We add that total dose to the milk replacer.)

Use 1% (Ivomec) - orally at 1 cc per 40 lbs of body weight in the milk for three days in a row to be sure you get everyone at least once (Plumb). Bigger cats drink more and little cats less, so this dose has worked well. Be sure to use multiple pans if you have a large colony, or some might not get a chance to drink. If a cat does not get a drink or does not come up today, then make sure they get it tomorrow.

On your first time deworming, repeat in 7-10 days to completely remove the external parasites—eggs and all. Feral cat colonies get dewormed spring and fall in this manner but only do one 3-day course, unless there is an issue with ear mites.

If you have a cat that will not drink the medicated milk, you can use Ivomec Pour-On topically between the shoulders. You need to treat each cat, even if you have to trap them; otherwise the untreated cat will keep sharing his ear mites. One good dose is all you need so put the Ivomec on and release. Repeat in 10 days to get the eggs that hatch.


If you are adding to a confined cat colony, be sure you treat before mixing. The last thing you want is to bring anything in once the colony issues are controlled! Topical Ivomec, 10 days apart, works well here. The advantage of topical Ivomec is knowing the correct dose is in the cat—put it between the shoulder blades on the skin and you're done.

The key to healthy feral cats is to treat all of the cats, and this can be done effectively and easily. This same milk treatment has been used for farm cat colonies and has had great results in getting them healthy.

If you need help, call us at 1-800-786-4751.

-Dr. B
Don Bramlage, DVM, Director of Veterinary Services at Revival Animal Health

The materials, information and answers provided through this website are not intended to replace the medical advice or services of a qualified veterinarian or other pet health care professional. Consult your own veterinarian for answers to specific medical questions, including diagnosis, treatment, therapy or medical attention.

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