The spleen is an important part of the immune system. It is especially important for fighting off certain types of infections. People who have had their spleen removed or whose spleen is not working properly are therefore at greater risk of some infectious diseases. The risk of infection is highest in the first few years after the spleen is removed or stops functioning, but the risk remains increased for life. In general, people who are immunocompromised (i.e. have a weakened immune system (including lack of a working spleen)) can get sick from microorganisms that would not usually cause illness in other people, and bugs that would only make most people mildly ill can cause severe infections in immunocompromised individuals.  This is a particular problem in children.  Kids that have their spleen removed are often treated with antibiotics for a few years to help prevent infections.

Infection with Streptococcus pneumoniae and Haemophilus influenzae, which are both common  pathogens of humans, are two of the major concerns in people without a functioning spleen.  The most commonly discussed zoonotic disease threats in these individuals are the bacterium Capnocytophaga canimorsus and Salmonella.  Capnocytophaga lives in the mouth of a large percentage of healthy dogs.  Infection in immunocompromised people typically occurs as the result of a bite, but is very rare in other people.  There is no indication to test dogs for Capnycytophaga, because it is difficult to identify and we do not know how confident we can be about a negative result (e.g. it may be in the dog’s mouth even though it doesn’t grow from a sample in the lab).

Here’s some general advice for individuals who don’t have a working spleen:

• Talk to your physician or an infectious disease specialist about the risks associated with animal contact (including pets).
• In general, you do not need to give up your pets. The risk of infection may be increased, but the risks can be minimized in most situations, and the risks are often outweighed by the beneficial aspects of pet ownership.
• Be wary of any possible exposure to an infectious disease, and be diligent about infection control precautions. If you are bitten by an animal (of any kind), see a doctor as soon as possible.
• Make sure your pets do not touch any open wounds you may have.  In particular, do not let a dog lick skin that is damaged in any way.  Since Capnycytophaga is commonly carried in the mouths of healthy dogs, licking in general should be discouraged.
• Don’t feed your pet raw meat or raw treats, because this increases the risk exposure to Salmonella from your pet’s stool.
• Be very careful when handling stool to avoid contaminating yourself or other objects/surfaces. If you have a cat, ideally its litterbox(es) should be changed by someone else.
• Always wash your hands well (and frequently) after contact with pets and pet foods, including dry commercial pet food (kibble).