B. ranarum can also infect human skin, which is called zygomycosis. Zygomycosis can also refer to infections with other species of fungus, or infection in other parts of the body. B. ranarum is normally only a concern in tropical and subtropical regions, and even in those regions, infection is uncommon. Most often, it is children who are affected, usually after they have sustained an injury to the skin or an insect bite. Rarely, B. ranarum has also been found in the human gastrointestinal tract, a condition known as basidiobolomycosis.
Appearance In The U.S.
Since 1986, basidiobolomycosis has been diagnosed in people living outside the typical areas of Indonesia, India, and Africa, including 19 cases in the United States, primarily in Arizona, and 11 in Saudi Arabia. The appearance of this tropical fungus infecting people living in dry climates, such as the American Southwest or the Middle East, is rare.
No one is sure yet how people living in an arid zone came to be infected with B. ranarum. The current working hypothesis is that the fungus was unknowingly ingested by way of contaminated food or, as in the cases of children, in soil. B. ranarum is thought to be opportunistic, meaning that when it is ingested by a person who is already compromised with another illness, the fungus is able to proliferate and cause infection.
Because basidiobolomycosis is rare, especially in an area such as Arizona, many of the cases in the U.S. were not diagnosed immediately. Patients had often experienced abdominal pain, fever, and may have also had a mass in the abdomen that was discovered during a physical exam or a radiological test such as a CT scan. Doctors usually began the diagnostic process by looking for cancer, IBD, or diverticulitis as possible causes for the symptoms. In some cases, misdiagnosis occurred before the fungal infection was discovered.
An Emerging Infection
After 6 cases of basidiobolomycosis were treated at the Centers for Disease Control and Prevention (CDC) between 1994 and 1999, researchers at the Mayo Clinic got involved and decided to further study infection with B. ranarum.
Once patients were properly diagnosed with basidiobolomycosis, treatment included resection surgery to remove the affected parts of the large or small intestine, followed by administration of antifungal drugs on a long-term basis. In some cases, the liver and the gallbladder were also infected. Of the 44 cases described in a paper published by the medical journal Clinical Infectious Diseases, the average age of patients was 37 years (range: 2 to 81 years) and 8 patients (18%) died of the infection.
The Take-AwayEven though basidiobolomycosis is on the radar of the CDC, it is still extremely rare. Symptoms of abdominal pain, fever, and an abdominal mass are more likely due to another more common gastrointestinal disease than an infection with B. ranarum.
Centers for Disease Control and Prevention. "Gastrointestinal Basidiobolomycosis -- Arizona, 1994-1999." MMWR Morb Mortal Wkly Rep. 1999 Aug 20;48(32):710-713.
El-Shabrawi MH, Kamal NM. "Gastrointestinal basidiobolomycosis in children: an overlooked emerging infection?" J Med Microbiol. 2011 Jul;60(Pt 7):871-880. Epub 2011 May 5.
Nemenqani D, Yaqoob N, Khoja H, Al Saif O, Amra NK, Amr SS. "Gastrointestinal basidiobolomycosis: an unusual fungal infection mimicking colon cancer." Arch Pathol Lab Med. 2009 Dec;133(12):1938-1942.
Vikram HR, Smilack JD, Leighton JA, Crowell MD, De Petris G. "Emergence of Gastrointestinal Basidiobolomycosis in the United States, With a Review of Worldwide Cases." Clin Infect Dis. 2012 Mar 22. [Epub ahead of print]