An Eighteen Year Study of Intestinal Protozoans in the Los Angeles Area Between ۱۹۹۶ and ۲۰۱۳

Parasitological studies of large patient populations are rare in the United States compared to third-world countries where endemic parasitosis are more frequently reported (۱). We routinely monitor and report the patterns and trends of human parasitosis in the US at the Parasitology Center, Inc. (PCI), in Scottsdale, Arizona. It was revealed that ۹۱۶ (۳۲%) of ۲۸۹۶ examined patients from ۴۸ states were infected with ۱۹ species of intestinal parasites in the year ۲۰۰۰ (۲). In that study, ۳۱۴ of ۸۵۹ examined patients (۳۶%) from California were found to be infected (۲). Infections with helminth parasites such as Ascaris lumbricoides and non-pathogenic protozoans were rare; therefore, they were not included in the present study. The seven reported species of protozoan parasites constituted ۹۱.۵% of infections reported in the United States. Multiple infections with ۲-۴ parasitic species constituted ۱۰% of the infected cases (۲). We also investigated the epidemiology of Blastocystis hominis in ۴۸ states and the District of Columbia in ۲۰۰۲-۲۰۰۴ and included trends in annual, seasonal, geographical and host distribution and symptomology by age, gender, and season (۳). In that report, ۱۶% of ۱۰ ۵۸۲ fecal specimens from ۵۲۹۱ patients tested positive for B. hominis; in California, ۲۶۳ of ۱,۳۲۸ examined patients (۲۰%) were also positive for B. hominis. In a similar ۳-year epidemiological study of ۹۸۵۶ fecal specimens from ۴,۹۲۸ patients from all states and the District of Columbia that we tested between ۲۰۰۳ and ۲۰۰۵, ۲۷۹ (۶%) were positive for Cryptosporidium parvum infection. Studies of this magnitude have not been performed in the US. Few studies have been done on relatively large patient populations in the US (۴,۵) or more geographically limited populations, which report the prevalence of B. hominis infection only in California (۶) and Ontario (۷). The present investigation is the first to cover a span of ۱۸ years. Evaluating the patterns and trends of parasitic infections in studies of such a long duration is a great tool for understanding the epidemiological characteristics and disease burden, improving the reporting of cases, planning preventive strategies, and designing therapeutic and public health measures in the management of these infections. Nevertheless, an overview of studies of shorter duration from comparable urban/suburban area in developing and developed nations are included.