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Abstract. One-third of 5,792 fecal specimens from 2,896 patients in 48 states and the District of Columbia tested positive for intestinal parasites during the year 2000. Multiple infections with 2−4 parasitic species constituted 10% of 916 infected cases. Blastocystis hominis infected 662 patients (23% or 72% of the 916 cases). Its prevalence appears to be increasing in recent years. Eighteen other species of intestinal parasites were identified. Cryptosporidium parvum and Entamoeba histolytica/E. dispar ranked second and third in prevalence, respectively. Prevalence of infection was lowest (22−27%) in winter, gradually increased during the spring, reached peaks of 36−43% between July and October, and gradually decreased to 32% in December. A new superior method of parasite detection using the Proto-fix™-CONSED™ system for fixing, transport, and processing of fecal specimens is described. In single infections, pathogenic protozoa caused asymptomatic subclinical infections in 0−31% of the cases and non-pathogenic protozoa unexpectedly caused symptoms in 73−100% of the cases. The relationship between Charcot-Leyden crystals and infection with four species of intestinal parasites is examined and the list of provoking parasitic causes is expanded.

A key to the classes, orders, families, and subfamilies of Acanthocephala based on the Meyer-Van Cleave system as presented by Amin (1985) is provided. A new class (Polyacanthocephala) and a new order (Polyacanthorhynchida) are erected to accommodate members of the monogeneric family Polyacanthorhynchidae Golvan, 1956.

Neoechinorhynchus Stiles & Hassall, 1905 is revised based on both bibliographic studies and the examination of material. The evolution of the concept of the genus is discussed. The concept of Hebesoma Van Cleave, 1928 is also commented upon. The synonymy of the two genera is accepted, with Neoechinorhynchus having priority, and a new diagnosis for Neoechinorhynchus is provided. However, Hebesoma is recognised as a subgenus of Neoechinorhynchus, being differentiated from the nominal subgenus primarily on features of the egg. Of the 109 species studied, seven are transferred to other genera and 14 are considered invalid. Eleven species are assigned to the subgenus Hebesoma and 48 to the subgenus Neoechinorhynchus. Twenty-nine species were not assigned because of incomplete or absence of descriptions of adult females. Keys to assigned and non-assigned species are provided. Notes on the zoogeography of the 88 accepted species are also included.

Over 700 specimens of Corynosoma strumosum (Rudolphi, 1802) Lühe, 1904 were collected from one young male Caspian seal, Pusa caspica (Gmelin) in the southern land-locked Caspian Sea in April, 2009. Collected worms showed consistent variations from those reported by other observers using light microscopy especially in proboscis hook and trunk spine patterns. SEM images revealed many features that have not been previously reported including the shape and distribution of trunk spines, dorsoventral differences in proboscis hooks and their organization, the baldness of anterior proboscis, the rough egg topography, epidermal micropores, and variations in the female gonopore. This isolated population of C. strumosum from the land-locked Caspian Sea is distinguished from others reported from open waters elsewhere by the distribution of trunk spines, consistently smaller size of trunk and testes, larger eggs, and fewer proboscis hooks. Histopathological sections reveal the invasive path of worms in host tissue with damage to intestinal villi and worm encapsulation. Information obtained from SEM studies and histopathological sections is reported for the first time.