2019 Flea & Tick Survival Guide

4 Surprising Flea Diseases You Need to Know

7 min read

By Lynne Miller


It’s easy to dismiss fleas. Unlike ticks, which are famous for causing Lyme disease in dogs and people, fleas don’t seem all that threatening. Mostly, we see the tiny bloodsuckers as a nuisance for pets and for us, not a serious threat to anyone’s health.


However, fleas can transmit a surprising number of diseases to animals and humans. Fleas can cause serious harm to you and your pet’s health through their bites and when they are ingested (such as when self-grooming) by the animals they target.


Here are four flea diseases you need to be aware of:


Murine Typhus


Rats are the main carrier for the type of flea that carries Murine typhus, but cats that come into contact with infected fleas can bring these disease vectors home. According to the Texas Department of State Health Services, humans usually get typhus from a flea bite. When the bugs bite, they usually defecate at the same time.


A type of bacteria found in the feces, Rickettsia typhi, enters the body through the bite wound or from a person scratching the bite area.


Signs of typhus include headache, fever, nausea, and body aches. Five or six days after the initial symptoms, you may notice a rash that starts on the trunk of your body and spreads to your arms and legs. If you think you have murine typhus, see a doctor as soon as possible, the Texas Department of State Health Services says. The disease can be treated with antibiotics, but if you wait too long, you may need to be hospitalized. If left untreated, the disease may linger for several months.


Cases of murine typhus are found in hot, humid areas with large rat populations. Texas health authorities saw 324 cases in 2015, including one death, said Chris Van Deusen, press officer for the Texas Department of State Health Services. At least one death from murine typhus has occurred in Texas each year since 2012.


“A delay in seeking treatment can lead to worse outcomes, which can happen since the symptoms are pretty general,” Van Deusen said. “Other conditions, like diabetes, kidney disease, and a history of alcohol abuse are associated with more severe” cases.


To date this year, the California Department of Public Health has received reports of 14 cases of murine typhus, none fatal, from four counties, a spokesman for the department said. In a typical year, the state sees about 50 cases, primarily in the suburbs of Los Angeles and Orange counties.


Elsewhere, murine typhus is rare.


“In the Pacific Northwest, it’s almost nonexistent,” says Dr. Lee Herold, chief medical officer for the DoveLewis Emergency Animal Hospital in Portland, Oregon.


Mycoplasma haemofelis


Mycoplasma haemofelis (M. haemofelis) is a parasitic bacterial disease that is transmitted to cats through flea bites, as well as tick and mosquito bites. An infection of the red blood cells, M. haemofelis can cause fever and anemia in cats, Herold says. There is also some evidence that M. haemofelis can infect humans, especially those with compromised immune systems. Because fleas are equal opportunity feeders, an infected flea can transmit the parasite to both you and your pet.


M. haemofelis attaches to the infected cat’s red blood cells, which leads to the body’s immune system treating the red blood cells as foreign, marking them for destruction. This destruction of large numbers of red blood cells frequently leads to anemia, Herold says.   


Veterinarians often prescribe antibiotics to treat the affected animals. In severe cases, cats may require a blood transfusion followed by antibiotics.


“Some cats need steroid medications to prevent the immune system from attacking its own red blood cells,” Herold says. Treatment can take four to six weeks.




One of the most loathsome parasites, tapeworms make themselves at home in the intestines of dogs, cats, and humans. Pets can get tapeworms by swallowing infected adult fleas, which can occur when animals groom themselves or other animals. Cats can also get the disease by eating infected mice, Herold says.


While extremely uncommon in adults, children may get infected by accidentally swallowing an infected flea, which they can encounter while playing outdoors, according to the Centers for Disease Control and Prevention (CDC). Children and pets pass segments of tapeworms, known as proglottids, during bowel movements.


Treating tapeworms in pets and humans is easy. For both species, a drug called praziquantel is given either orally or, for pets only, by injection, according to the CDC. The medication causes the tapeworm to dissolve within the intestine.


Cat Scratch Disease


This disease is interesting. Bartonella henselae (B. henselae), the bacteria that causes cat scratch fever, is fairly common in felines. According to the CDC, about 40 percent of cats, especially kittens, have the bug at some point in their lives.


Some cats develop serious symptoms. The CDC recommends taking your cat to the veterinarian if it is vomiting, seems lethargic, has red eyes, swollen lymph nodes, or a decreased appetite.


Many cats never get sick and those that do typically have a fever for two or three days and then recover completely. So your cat may seem perfectly healthy, but can still make you sick. “A human might get cat scratch fever even if the cat doesn’t present symptoms,” Herold says.


Cats pass the disease on to humans by biting or scratching a person hard enough to break the skin, or by licking on or near wounds or scabs, the CDC says.


In an unusual case covered by several media outlets last year, Janese Walters of Toledo, Ohio, woke one morning to blindness in one eye. After a month of tests, doctors couldn’t determine what caused the blindness—until the woman told them about her cat. They were then able to trace the infection to the B. henselae bacteria and concluded she had cat scratch disease, and that she had lost her sight in one eye after her cat licked her eye.


In rare cases of human infection, the disease can affect the brain, eyes, heart, or other internal organs, though these complications are more likely to occur in children under the age of five and in people with compromised or weakened immune systems, the CDC says.


Next: How to Keep Fleas Away from Your Home