By David Douglas

NEW YORK (Reuters Health) - Cryptosporidiosis -- an illness characterized by diarrhea, fever, and chills -- appears to be under-reported in the U.S. elderly population, Massachusetts-based researchers report.

Cryptosporidiosis, caused by the waterborne parasite Cryptosporidium, is associated with dehydration and poor health outcomes, including death. As Dr. Siobhan M. Mor told Reuters Health, "The elderly may have co-existing conditions, such as heart or renal failure, which can be aggravated by the fluid and electrolyte imbalances caused by cryptosporidiosis diarrhea."

She added, "The current healthcare and surveillance systems pick up a minority of cases of cryptosporidiosis, and they do not provide sufficient information about vulnerable populations, such as the elderly."

In order to gain more information, Mor, of Tufts Cummings School of Veterinary Medicine, North Grafton, and colleagues identified 1304 people elderly people who had a cryptosporidiosis-related illness between 1991 and 2004.

Hospitalizations rose yearly at a rate of 0.15 to 0.39 cases per 100,000 elderly subjects. However, the researchers attribute this mainly to increased awareness and testing.

There were considerable state-by-state variations in hospitalizations. Furthermore, of 178 hospitalizations in 1993, 65 percent involved Wisconsin residents and more than 80 percent of these were Milwaukee residents hospitalized during the large-scale cryptosporidiosis outbreak in that city.

People aged 85 and older were more than twice as likely to be hospitalized as patients aged 65 to 74 years. They were also more likely to die.

The researchers call for strengthened surveillance systems and increased screening and testing for cryptosporidiosis in the elderly. "Testing and reporting practices such as those used in Wisconsin," they conclude, "may serve as an example to health practitioners and authorities in all US states."

SOURCE: Clinical Infectious Diseases, March 15, 2009.

Related MedlinePlus Pages:

• Cryptosporidiosis
• Seniors' Health