Ask the Veterinarian/Fleas


QUESTION: Why do horses and cows not have a flea problem?
I know fleas will bite people, birds, rodents and reptiles, but I have never seen a horse or cow with fleas.
Iíve had horses all my life, and know that flies, ticks are a problem but why donít they get fleas?

Thanks Dennis

ANSWER: Most pests are "host-specific" and they only can live on those animals that are their natural hosts.

Some pests do cross lines however. Sea Lions in California have been found with heartworm infections and while scientists are not really sure how they are getting them, they are suspecting a mite that seals carry. Normally, the infective larvae of the heartworm is only found in Mosquitoes.

And while fleas are geared toward dogs and cats, they live very happily on Opossums. Ticks bother everything from mice to deer.

Lice can live on your horse, but you won't get them. However, cat scabies can be spread to humans, but demodectic mange, which is another mite, cannot be spread to humans.

So there you have it. And of course, is there ANYTHING a fly won't bother??

---------- FOLLOW-UP ----------

QUESTION: Thanks for the reply but I am more interested in the specifics. I know fleas will feed on dogs, catís rats, people, birds but not on horses.
Is there something in there blood that they donít like or canít tolerate.
Mosquitoes I know will feed on just about anything that has blood.
I know ticks, will get on horses, but I was just wondering why fleas donít.
Can you be more specific please?

Thanks Dennis

As I said, parasites are host-specific." That means that they only feed on the species that they were "born" to feed/live/breed or be parasitic on.

That's pretty specific. It's how they are created as it were.
Cat and dog fleas are driven to feed on the animal that they were coded to feed on, that is cats and dogs. But they WILL feed on other animals. There are over 200 species of fleas alone.

When they are only found on certain animals, then they are considered host-specific.

So not all of them are, but obviously they don't like horses and cows or they would be as covered with fleas as stray cats and dogs are.

This will help you understand fleas better:

and the above link:

Hopefully this will answer your question better than I can!

Ask the Veterinarian

All Answers

Answers by Expert:

Ask Experts


Jana Connell RVT, CVT


PLEASE READ BEFORE SUBMITTING TO ME: I am NOT a vet and do NOT diagnose diseases. That is only for a licensed Veterinarian to do. I will give you suggestions and steer you toward calling your vet for help. You can call the vet's office and talk to the technician there or the vet at times. Don't be afraid to call them! If you have a serious issue with your pet please post it to one of the veterinarians in here- I will tell you the same thing in my answer. IF your pet is injured or in an emergency situation, CALL YOUR VET- Do not wait and post in here. Just call the vet's office and get them in to see the vet right away. Critical treatment time is lost if you seek answers here when you should have your precious pet at the vets!! Don't sit at home waiting for an answer when your pet is critically ill or injured!! I can answer most questions about small animal and wildlife care as well as small animal nutrition. I can also answer questions about all phases of dental care for small animals. I DO NOT answer questions about birds (unless it is wildlife or songbirds) or HAMSTERS/GERBILS/CHINS/GUINEA PIGS/REPTILES/FROGS/RABBITS/PET BIRDS OF ANY KIND so please submit these questions to the appropriate sections. I, as well as other experts in here, do NOT do homework questions- that is for YOU to do! Please respect these rules for all of us. Thanks!


I have over 42 years experience in the field of veterinary medicine. I specialized in small animals and did wildlife rehab for over 25 years, mostly raptors, squirrels and opossums. I am a Small Animal Nutritional Consultant with 6 certificates from Hills Pet Foods, CNM and Purina. I also specialized in Small Animal Dentistry which is a field I truly love. I also Teach Veterinary Technology to working technicians who are studying to take their California Tests to become Licensed Technicians. They have to take both the VTNE (Veterinary Technician National Exam) and the California boards.

Audubon,World Wildlife Federation, American Society of Veterinary Dental Technicians.


Licensed with California and Oregon, RVT and CVT. Certified Veterinary Dental Technician Have over 1500 logged hours of Continuing Education Credits(that means I keep up to date!).

Awards and Honors
Nominated for Expert of the Month for the last 5 years.

©2017 All rights reserved.