Intestinal parasitism in the United States: update on a continuing problem

Area of Science:

• Medical Parasitology
• Public Health Surveillance
• Epidemiology

Background:

• Intestinal parasitic infections are a significant public health concern in the United States.
• Previous data indicated lower prevalence rates for certain parasites, necessitating updated surveillance.

Purpose of the Study:

• To document the patterns and prevalence of intestinal parasitism across the U.S. using state diagnostic laboratory data.
• To analyze trends in specific parasitic infections, focusing on Giardia lamblia and hookworm, between 1987 and 1991.
• To identify geographical and seasonal patterns of these infections.

Main Methods:

• Analysis of stool specimen results from state diagnostic laboratories in 1987 (216,275 specimens) and 1991 (178,786 specimens).
• Categorization of identified parasites into protozoans and helminths, with specific species quantified.
• Comparison of prevalence data between the two survey years and examination of geographical and seasonal variations.

Main Results:

• In 1987, 20.0% of specimens were positive for parasites, with protozoans like Giardia lamblia (7.2%) being most common. Nematodes such as hookworm (1.5%) were the most frequent helminths.
• Giardia lamblia identification increased significantly from 4.0% in 1979 to 7.2% in 1987 and 5.6% in 1991, with notable increases in the Midwest and Northwest.
• Cryptosporidium, not previously surveyed, was identified in 25 states in both 1987 and 1991, indicating widespread presence.

Conclusions:

• Intestinal parasitism remains an important, often overlooked, cause of gastrointestinal illness in the U.S.
• The prevalence of Giardia lamblia appears to be increasing, warranting continued monitoring and public health attention.
• The widespread identification of Cryptosporidium suggests its growing importance in the U.S. parasitic disease landscape.