AN EIGHTEEN YEAR STUDY OF INTESTINAL PROTOZOANS IN THE LOS ANGELES AREA BETWEEN 1996 AND 2013

Abstract

Seasonal and annual prevalence of intestinal protozoans were studied for a period of 18 years in an urban/suburban Los Angeles area. This is the first such study anywhere in the world. A total of 7766 fecal specimens from 3883 patients in the Los Angeles County, from 1996 to 2013 were tested at Parasitology Center, Inc. (PCI), Scottsdale, Arizona. During this period, 1629 (41%) of patients were found infected with one or more protozoan parasites. The most prevalent parasites were Blastocystis hominis (19%), Entamoeba histolytica/E. dispar (6%) E. hartmanni (6%), and Cryptosporidium parvum (5%). Blastocystis hominis made up 45% of all infections. Infections with Blastocystis hominis progressively declined through 2013 while those of C. parvum increased. Infections with B. hominis were more prevalent in colder weather and lowest in August and September. Infections with C. parvum were most prevalent from March to June and lowest in August. The overall monthly prevalence for all protozoan parasites varied between 34% in August and 51% in February. The composition of the parasitic fauna diagnosed, annual prevalence rates, and seasonality were discussed in
comparison with other studies.