X-rays Can Hint At Crayfish-Parasite Infection

If a patient complains of fever, cough, chest pain, shortness of breath, and fatigue, and X-rays show excess fluid around the lungs, ask if he or she has been eating raw crayfish.

Crayfish—also known as crawdads and, particularly in the South, crawfish or mudbugs—commonly carry a parasite called Paragonimus kellicotti. A thorough cooking kills the half-inch oval worms. But if infected crayfish are eaten raw, the worms can travel from a person’s intestine to the lungs or to the brain, where they can cause severe headaches and vision problems. They can even migrate to just under the skin, where they appear as small, moving nodules.

Doctors at Washington University School of Medicine in St. Louis have diagnosed six cases of Paragonimus infection in the past three years, including three since September.

“The infection, called paragonimiasis, is very rare, so it’s extremely unusual to see this many cases in one medical center in a relatively short period of time,” said Washington University infectious diseases specialist Gary Weil, MD. Weil, professor of medicine and of molecular microbiology, treated some of the patients. “We’re almost certain there are other people out there with the infection who haven’t been diagnosed. That’s why we want to get the word out.”

Crayfish are freshwater creatures that resemble miniature lobsters. Boiled crayfish are considered a delicacy, especially in Louisiana. The Washington University doctors didn’t address the question of why anyone would eat them raw. Evidently some people do—though not many, because the disease is so unusual that most of the six Washington University patients had received multiple treatments for pneumonia and had undergone invasive procedures before being correctly diagnosed.

Paragonimiasis is seldom fatal and can be treated with praziquantel taken orally three times a day for just two days. All six Washington University patients recovered completely, including one man who had temporarily lost his vision because the parasites had invaded his brain.

To diagnose it, “you have to be a bit of a detective and be open to all the clues,” said Washington University infectious diseases specialist Thomas Bailey, MD, professor of medicine. Bailey diagnosed and treated the first case at the School of Medicine.

Infected patients show elevated levels of eosinophil white blood cells, and X-rays show excess fluid around the lungs and sometimes the heart.

In addition to alerting medical personnel, the Washington University doctors have a message for the public: “do not eat raw crayfish.”

Excellent advice. Boiled, however, they’re delicious. Here’s a recipe. Hurry, though; the season has just about ended.

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