The plague, fevers, tularemia: The diseases fleas can carry and how to treat them
There are more than 2,000 species of tiny (0.04 to 0.15 inches), wingless, blood-sucking fleas that live on the body of the host they infest. Although fleas cannot fly, they have developed powerful legs and are famous for being able to jump quite high in proportion to their tiny bodies — more than 100 times their body length, up to a foot or more. Between 1830 and the 1960s, flea circuses were popular in certain European countries.
Tiny chariots, carts, musical instruments and other "equipment" were glued to fleas so they could "entertain" paying customers who would have to buy a magnifying glass to watch them.
The bubonic plague was spread by fleas, not rats
The most infamous flea-to-human transmitted disease is the bubonic plague, which was caused by the bacterium Yersinia pestis. It was called the Black Death in the mid-1300s when it caused an epidemic in Europe and Asia that killed 50 million to 200 million people, including over half of Europe's population. The plague was thought to be spread by rats, but it was actually bites from fleas on the rats (and then fleas spread from human to human) that spread the infection.
Black death still around today
The bubonic plague still exists, but because it's treatable with antibiotics and its spread can be limited by rodent and flea control, it has become a rare condition — fewer than 20 cases reported annually in the U.S. Symptoms from bubonic plague may include headache, fever, weakness, swollen lymph nodes (called "buboes," hence the name bubonic plague) and other nonspecific symptoms. It can progress to infect the lungs or even get into the blood stream (septicemic plague). Mortality from bubonic plague today is between 1% and 10%, whereas septicemic plague may have mortality as high as 50% — and if untreated, it's over 90%.
Fleas can spread other diseases too
Other flea-borne bacterial diseases may cause fever, body aches, nausea/vomiting, cough, rash, swollen lymph nodes, skin lesions/rashes, and/or other symptoms. Some examples include:
Murine typhus, a rare infection (20-100 cases a year in the U.S.) caused by the bacterium Rickettsia typhi and transmitted by the feces of cat or rat fleas coming in contact with a break in the skin (such as from the flea bite itself).
Cat scratch disease (CSD) is from the scratch of a cat that has been infected from a flea bite with the bacterium Bartonella henselae. In addition to the symptoms noted above, there may also be formation of a pustule at the scratch site, and/or tender/swollen lymph nodes most commonly under the armpit — the arm is the most common place for the cat scratch to occur. CSD is the most common flea-associated bacterial disease in the U.S., with more than 25,000 cases annually.
Flea-borne spotted fever (due to Rickettsia felis, about 300 cases a year in the U.S.), which in addition to the symptoms above may also cause a rash that starts on the body and spreads to the arms, and which can look "spotted."
Tularemia, a disease caused by the bacterium Francisella tularensis and commonly transmitted by a tick, deerfly and/or handling the body of a sick or dead infected animal. It may also be transmitted by fleas (for a total of about 200 cases a year in the U.S.), and may have the above symptoms as well as mouth ulcers, pneumonia, other symptoms.
The diagnosis of a flea-transmitted bacterial infection may be suspected based on specific symptoms and a history of exposure to fleas. For some cases, specialized cultures, polymerase chain reaction (PCR) and/or other tests may be indicated to confirm the diagnosis.
Prevention is best, since few vaccines exists for these illnesses
There are no vaccines to prevent these illnesses, so avoiding flea bites by using insect repellents such as DEET is recommended. Antibiotic treatments (doxycycline is a good choice for many of these infections) are typically effective.
Besides bacterial conditions, certain parasites may also be transmitted by fleas. This includes flea-borne tapeworms, which can infect pets and rarely humans, and occurs if the flea is ingested. It may cause stomach ache, loss of appetite, stool changes, gas, weight loss, hunger pains and nausea. The diagnosis is made by microscopic analysis of the stool, and anti-parasitic medications are usually effective at eradicating the condition.
Cutaneous leishmaniasis (CL), is caused by the protozoan parasite of the genus Leishmania, spread by sand fleas. Uncomplicated cases manifest as a single or a few skin lesions that are less than half an inch in diameter. These usually resolve on their own or with topical antiparasitic cream. Complicated cases may involve the mucosa (ML), have more/larger lesions, cause swelling of the lymph nodes, and/or cause a more systemic inflammatory response.
The diagnosis of CL or ML is made based on clinical suspicion, and verified as needed by a PCR test of a sample of infected skin. Complicated cases may require treatment with an oral or even intravenous antiparasitic medication. Years ago, all cases of CL and ML in the U.S. were in travelers who acquired the condition abroad. More recent data suggests some cases have been contracted within the U.S., so it looks like this "tropical disease" has made its way here.
People can be allergic to flea bites
A flea bite and/or flea embedded in the skin may cause allergic and/or other skin reactions. For example, tungiasis is a skin condition caused by the adult female sand flea Tunga penetrans embedding itself in the skin, causing itching, inflammation and/or pain, and may have certain systemic symptoms as well. Extraction of the embedded flea may be complicated by a bacterial infection of the wound, so it's recommended that sterile technique be used by an appropriately trained clinician.
There are many diseases transmitted by fleas, so letting your clinician know if you have had contact with them and/or have traveled to areas where flea-borne diseases are common is important. Then you can be diagnosed correctly and have appropriate treatment prescribed.
Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com.
This article originally appeared on MetroWest Daily News: Bubonic plague is one of the flea-to-human transmitted diseases
