The New York Times - April 10, 1984
Lawrence K. Altman, M.D.

It has, for example, inflicted a devastating complication upon at least 112 patients with acquired immune deficiency syndrome, or AIDS, which destroys the human body's ability to ward off infections.

The parasite has also been found among a small but growing number of healthy individuals who have suffered so-called traveler's diarrhea, and also among those who have suffered chronic diarrhea, according to Dr. Dennis D. Juranek of the Federal Centers for Disease Control in Atlanta. Although the parasite has caused distressing symptoms among these people, they have recovered without incident after the infection ran its course. It is not known how humans acquire the parasite.

New tests to detect the cryptosporidia were developed as a result of the surge of infections among AIDS patients. And once the tests were available, doctors began using them among patients without AIDS who had unexplained causes of diarrhea. To their surprise, they have found the parasite with increasing frequency.

But most experts do not believe an epidemic of cryptosporidiosis has suddenly appeared in the world for the first time. Rather, they suspect the parasite has been causing disease for decades and is only now being recognized for the first time.

Dr. Harley Moon, a veterinarian at the National Animal Disease Center in Ames, Iowa, and a specialist in intestinal diseases, said he doubted that cryptosporidiosis had become more common. "Veterinarians have just missed it," he said, "and I suspect physicians have been missing it in people for decades as well."

Cryptosporidia are easy to overlook because they are among the tiniest parasites, and small parasites are extremely difficult to diagnose correctly through a microscope.

The newer diagnostic tests are based on immunological methods, and one bacteriologist who has developed proficiency in them is Dr. Pearl Ma of St. Vincent's Hospital in New York. Since 1981 she has diagnosed 82 cases, half of them in 1983 alone. The overwhelming number have been among AIDS patients. But in recent months Dr. Ma said she had been recognizing the parasite among travelers who returned from Egypt and the Cameroons in Africa and St. Lucia in the Caribbean. She has also found the organism among nurses who seem to have acquired cryptosporidiosis from patients.

Cryptosporidia cysts can survive in the environment for months, but no one is sure for how many months. It may take only one cyst to cause disease, and after it enters the human body the parasite typically infects the intestines. But Dr. Ma has found six cases of respiratory infection seemingly caused by the parasite.

Studies indicate the parasite is ubiquitous. Dr. Juranek, the Atlanta epidemiologist, said he expected that in time cryptosporidia would be found to be spread through contamination of municipal water supplies, in day- care centers and in other previously unsuspected places. But, Dr. Juranek said, "it remains to be seen just how frequently it occurs."

Perhaps the biggest problem in cryptosporidiosis is the lack of effective therapy. Doctors at the disease centers and others are planning studies to evaluate the effectiveness of a drug called spiramycin, which is not licensed in the United States but has shown limited promise in treating cryptosporidiosis among severely infected AIDS patients in other countries. The drug has been used in Canada and Europe for many years to treat other infections.

If spiramycin and other drugs do not prove successful in treating cryptosporidiosis, knowledge that the parasite causes a patient's symptoms would still be valuable. Accurate diagnoses would save unnecessary, costly and uncomfortable tests and would stop prescriptions of drugs that might prove dangerous.

Cryptosporidiosis has drawn keen interest from veterinarians and biologists, who have described the infection among a wide variety of animals.

Although there is agreement that the parasite should be a major area of research, there is sharp controversy over the extent of the parasite's importance to industry. The parasite has been detected frequently among calves in the first month of life and most veterinarians believe the organism can cause disease in other animals. However, Dr. Ronald Fayer of the Animal Parasitology Institute of the Federal Department of Agriculture in Beltsville, Md. has seriously questioned the ability of the parasite to cause disease without such co-factors as stress and coincidental infection with other organisms.

"Just because you find cryptosporidia in an animal with diarrhea doesn't mean the parasite is the cause," Dr. Fayer said.

A major scientific mystery about cryptosporidiosis is how humans and animals come in contact with the parasite. "Solving that problem is what makes it a challenging disease," Dr. Philip H. Klesius, who directs the Agriculture Department's regional parasite laboratory in Auburn, Ala., said. "We thought maybe dams were shedding enough cryptosporidia at the end of term to contaminate the newborn either as it passes through the birth canal or shortly thereafter," Dr. Klesius said. "We surveyed 19 dams for 6 weeks 3 times a week and we could never find the organism. Yet their calves got cryptosporidiosis." The survey was not the final word but it added to the mystery of how animals get the disease.

Most scientists have speculated that humans acquire the parasite from animals. But Dr. Ma, the New York bacteriologist, said she had been unable to detect the parasite among pets of patients in whom she had diagnosed cryptosporidiosis.

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