Cat scratch disease is a relatively rare bacterial infection by the Bartonella henselae bacterium that is, as its name might suggest, transmitted by cats, who act as a carrier to the disease (meaning they show no symptoms when infected). It is spread between cats by means of fleas, and causes no harm at all to the host cat, whose body usually rids itself of the infection within a month or so. This means that a cat determined to carry the disease does not need to be put to sleep--your veterinarian may recommend a treatment (such as an antibiotic) to clear the infection more quickly, so that family members are not at risk to repeat infection. In fact, it is believed that as many as half of all cats worldwide may have been infected at some point, many of them never passing it along to a human host. If a pet is diagnosed with the infection, it may be wise to wash one's hands after contact with the pet until a reasonable period has passed.
Transmission to humans occurs via contact with cat saliva, though oral or dermal contact is not usually enough to pass it along; roughly three fourths of all human cases occur as a result of a cat scratch or bite that allows the bacterium to gain entrance to the body through an abrasion or cut in the skin. Some portion of the remaining cases likely occur through contact with the eye. Often, the site of entry (if on the skin) will show what is called an inoculation lesion, a small, usually painless bump or blister that marks the point of infection. This is part of what helps to identify the disease, along with other symptoms, especially if the cut is identified by the patient as a mark from a cat with which the person has had contact.
The main symptom, aside from the minor inoculation lesion, is a swelling of the lymph nodes near the point of entry. An infection that reaches the body through the arm will often result in a mild to moderate swelling and tenderness of the lymph nodes in the joints of the arm, namely the elbow and armpit. An infection that enters through the face or neck will probably entail some minor swelling of the glands of the throat, and so forth. The symptoms of the disease, are, by and large, not serious. A very small portion of those infected will react strongly to the infection, with symptoms that may range all the way in severity to high fever or even seizure. These symptoms do not generally last longer than the duration of the infection itself, but if such severe symptoms are noted, see a doctor immediately. Advice from a health care professional is recommended regardless of symptoms, if only to verify the diagnosis absolutely. The inoculation lesion will usually appear within a week of infection, while swelling may take another week to a month to occur. Symptoms will disappear entirely within the course of two to four months of appearance.
