Ted Nugent in concert.
(Photocredit: Public Domain Graphic
via Wikimedia Commons)

Ted Nugent made Cat Scratch Fever (actually called “Cat Scratch Disease”) nearly a household name with his song in the late seventies but most people still know very little about this infection other than it involves a fever spread by cat scratches. In fact, it involves infection by bacteria of the genus "Bartonella." There are 24 Bartonella species, 14 of which can infect humans and five of which are harbored by cats. The five Bartonella species harbored by cats are spread by fleas. The most well studied and most common Bartonella organism is Bartonella henselae. Classically, cats transmit the organism when they are parasitized by fleas, scratch themselves, and get infected flea dirt (digested host’s blood excreted by fleas) in their claws, and scratch a person (or another cat) with their dirty claws.

Bartonella organism
(Photocredit: Public Domain Graphic
via Wikimedia Commons)

Flea dirt looks like black specks in the pet’s fur. On
close inspection some of the specks are comma shaped.
The “dirt” is actually flea excrement consisting of
dried blood from the host. The flea dirt drops
from the coat along with flea eggs (which are white).
The newly hatched flea larvae consume the flea dirt as food.
(original graphic by marvistavet.com)

THE HUMAN DISEASE

Infection with Bartonella henselae in the immunocompetent person (i.e., a normal person) leads to “cat scratch disease.” The inoculation site (a scratch from a claw containing bits of flea dirt) develops a small red bump (a “papule.”) About 2-3 weeks following contact with the infected cat, the lymph node in the area of the contact will swell and become painful and a fever develops. These signs generally resolve on their own and the condition is minor though lymph node enlargement can persist for several months.

If the patient does not have a competent immune system (in other words, they are very old, very young, debilitated from another condition etc.), one of several much more serious syndromes can result. The infection goes deeper into the body causing spleen enlargement, and potentially encephalitis, heart valve infection, and other conditions. These syndromes are still rare even in people who are immunocompetent but they are potentially very serious.

For more detail on the Cat Scratch Disease in humans we recommend:

• http://familydoctor.org/
• http://jaxmed.com/catscratch.htm

(photocredit: MorgueFile.com)

Since fleas carry the bacteria, cats with insufficient flea control are at highest risk. This means cats living in climates that are warm and humid (conditions where fleas thrive best) are most likely to be infected. If conditions are right, up to 40% of cats in an area may be infected. If a person is diagnosed with cat scratch disease, there is a 90% chance that the cats they own will be found infected as well.

This sounds somewhat concerning for the cat-owners in a flea area but it is important to realize that an infected cat cannot transmit the infection without a claw full of flea dirt. If the fleas are removed from the infected cat, there will be no flea dirt in the coat and no risk of disease transmission. Experimental studies have not been able to demonstrate cat to cat transmission in cats that mutually groom each other, fight with each other, mate with each other, or share food or litter with each other nor has transmission been demonstrated between infected mother cats and their kittens. Short of an actual blood transfusion with an infected cat, fleas (or ticks) are needed to spread the infection.

This is a highly controversial question. It was only relatively recently discovered (1992) that cats themselves were more than simple carriers of Bartonella henselae and that they could actually become infected themselves. Several illnesses seem to have been associated with Bartonella infection (fever, deep eye inflammation, lymph node enlargement, muscle pain, reproductive failure, and bacterial heart valve deposits called “endocarditis") but these seem to be isolated cases for the most part. The Bartonella organisms are highly adapted to live in the feline body without causing disease and it is only in rare situations that cats actually experience issues from this infection.

It has been suggested that Bartonella infection may be at the root of numerous chronic inflammatory conditions of the cat. With such high numbers of infected cats present regionally (up to 40%), it is going to be difficult to prove one way or the other whether there is a real association or just coincidence.

(photocredit: MorgueFile.com)

The short answer is: yes though the species of Bartonella they get is Bartonella vinsonii rather than Bartonella henslae. Fleas may carry the infection as they do for cats plus it appears that ticks may also be carriers. Since there are numerous infectious agents spread by ticks and it is not unusual for a dog to have multiple tick-borne infections it is very difficult to determine which infection is causing which signs.