Can Fleas Make My Cat Sick?

Fleas – What Are They?

white cat scratching itself
Itching may be a sign your cat is sick with fleas

Fleas are an external parasite that can infect cats and make them sick. They are small, blood-sucking parasites that jump from the environment to the host or from host to host. There are many species of fleas, and each species often prefers to infect a specific type of animal. Although each species prefers a specific host, that does not prevent them from infecting and biting other animals. The common cat flea (Ctenocephalides Felis) is the most common type of flea found on cats. This flea will infect cats, dogs and even humans. Fleas are very hardy parasites. They can live for months without eating and are able to survive in harsh environmental conditions. The cold winters in Alberta make it difficult for fleas to thrive, buttalk to your veterinarianabout regional differences in flea populations.

How do Fleas Make Cats Sick?

Fleas can make your cat sick in two ways. The flea infection itself can make a cat sick, or the flea can be carrying something that is transmitted to the cat, which can also make the cat sick:

Cat Illnesses due to Fleas


Fleas are blood-sucking parasites. The flea inserts it’s mouthparts into the skin and feeds off of blood from capillaries. If a cat or kitten has a severe infestation of fleas, there can be significant blood loss. Blood loss results in anemia. Anemia causes weakness and poor oxygen supply to vital organs. You can see organ failure and death in severe cases of anemia.

Flea Allergy Dermatitis

Flea saliva contains an anticoagulant to prevent blood from clotting. Fleas will introduce saliva into their bite wound to help in the feeding process. Some cats have an allergy to the saliva, which causes an intense itching. Cats can get sick from flea saliva due to skin inflammation, scabbing, and hair loss. Symptoms can be triggered by just one or two flea bites, so even mild infestations can be a problem.

common cat flea
The common cat flea

Illnesses Transmitted by the Flea


Fleas can carry tapeworms and transmit them to your cat. A cat will often ingest fleas or flea larvae when they groom themselves. If those fleas are infected with tapeworms, your cat then becomes infected with a tapeworm. Tapeworms are intestinal parasites that can make your cat sick from weight loss and perianal itching. Tapeworms can potentially be transmitted to humans. If you are concerned your cat has tapewormsplease contact your veterinarian.

Bartonellosis and Cat Scratch Fever

Fleas can transmit multiple species of the bacteria Bartonella, most commonly Bartonella henselae. This bacteria can make you and your cat sick. Most cats infected with this bacteria do not have any symptoms, but in rare cases can show fever, anemia, enlarged lymph nodes, and neurological signs. Cats become carriers and then risk passing the bacteria on to humans causing Cat Scratch Fever. The claws of a carrier cat can transmit the bacteria to humans through a scratch. Findmore information on Cat Scratch Fever.

close up of cat paw with claws out
Cat claws can carry Bartonella bacteria, which cause Cat Scratch Fever

How to Prevent Flea-Related Sickness in Cats

The best way to prevent flea-related illnesses in cats is to prevent the flea infection. It is important totalk to your veterinarian about flea preventionbecause there are many options available and not all are safe for use in cats. If you are concerned your cat may have fleas or a flea related illness and you want todiscuss treatment options, please contact our clinic. We would be happy to help.


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