In cats and other species, these proteobacteria infect red blood cells and can cause immune-mediated thrombocytopenia, a blood disorder that occurs when platelets in the blood stream become decreased. The most common rickettsial infection in cats is cat flea rickettsiosis caused by Rickettsia felis (R.felis) and transmitted by Ctenocephalides felis (cat fleas) in domestic cats. Feline rickettsial infection has been reported in Europe, North and South America, Africa, Australia and Asia. Cases are more common in the spring and summer when fleas are more active. In cats, the infecting organism, R.felis, does not usually cause active disease, although serious disease occurs rarely in cats, there is a zoonotic potential as the infecting organism can be spread to other animals, including humans, causing serious disease. 

Rickettsial infection describes a number of infections caused by proteobacteria that are transmitted primarily through fleas or ticks when they feed. There is a wide variety of rickettsial organisms causing a variety of diseases including typhus, spotted fever and Rocky Mountain fever in a variety of species.

Usually, infection is asymptomatic in cats but infection does cause symptoms and illness in humans. A small percentage of infected cats may show symptoms such as fever and other indications of illness, although this is rare. Symptoms of immune-mediated thrombocytopenia, a blood disorder of red blood cells resulting in low platelet count, can occur in cats. 

In cats, the primary organisms causing rickettsial infection transmitted through cat fleas (Ctenocephalides felis) is Rickettsia Felis (R. felis)

Rickettsia typhi (R. typhi) the organism primarily found in wild animals and dogs can also occur in cats which infected with canine fleas. This bacteria may be transmitted when the flea is blood feeding or when flea bites are scratched and the flea bite wound is contaminated with flea feces left on the skin.

Some types of rickettsial organisms (Rickettsia salmincola) may be transmitted through ingestion of an infected host (salmon flukes).

Ticks also carry several types of Rickettsia bacteria, causing a variety of diseases that affect various species including humans and dogs. Although these illnesses are rarely seen in cats, transmission and disease in cats is possible.

Your veterinarian will perform a physical exam and ask for a complete medical history of your cat, taking note especially of exposure to fleas or ticks if rickettsial infection is suspected. Your veterinarian will need to rule out other causes for your cat’ symptoms and routine blood and urinalysis tests may be taken for this purpose. Diagnosis of rickettsial infection is difficult as the infecting organism occurs at a low ratio in the bloodstream and its population fluctuates in the host animal. Usually, multiple diagnostic methods are required to reach a diagnosis of rickettsial infection. Diagnostic methods used, often in combination, include stained blood films or tissues examined under a microscope to locate infecting organism, serological tests, and molecular detection assays. Diagnosis is further complicated by the fact that multiple infectious organisms are often present with Rickettsia infections. 

If rickettsial infection is suspected, treatment with antibiotics should be started immediately before test results confirming diagnosis are received, as cats that display symptoms have a life-threatening condition and early treatment will result in a more favorable outcome. Antibiotics such as doxycycline and tetracycline are commonly used to treat rickettsial infections. Supportive care such as intravenous treatment and possibly blood transfusion for symptoms will be administered by your veterinarian with caution, due to the vascular disorder that often results from rickettsial infection. Removal of fleas or ticks that transmitted the disease will also be necessary. 

A cat that has experienced serious illness due to rickettsial infection will require recuperation including rest and continued monitoring by a veterinarian until recovered. Antibiotics to combat the infection will need to be continued. Due to the risk of infection in humans, pet owners should be aware of possible transmission and be vigilant for signs of infection in themselves and their family.

The best way to prevent rickettsial infection is by limiting your pet's exposure to fleas. You can prevent fleas in your pet by using prophylactic treatment such as a flea collar or topical medication; talk to your veterinarian about options. Removal of fleas from your environment is also important in preventing rickettsial infection in yourself and your pets. This may include rodent control, keeping your cat indoors, vacuuming, removing debris in your yard, washing bedding and using flea control methods available with adulticide and insect growth regulators. Flea control methods are available in the form of foggers, sprays and carpet powders for use in your home.