To understand the transmission of Cryptosporidium infection in children, fecal specimens from 62 Kuwaiti children with gastrointestinal symptoms found to be positive by microscopy were genotyped and subtyped with a small subunit rRNA-based PCR-restriction fragment length polymorphism analysis and a 60-kDa glycoprotein-based DNA sequencing tool. The median age of infected children was 4.5 years, and 77% of infections occurred during the cool season of November to April. Fifty-eight of the children (94%) had Cryptosporidium parvum, three (5%) had Cryptosporidium hominis, and one (1%) had both C. parvum and C. hominis. Altogether, 13 subtypes of C. parvum (belonging to four subtype allele families) and C. hominis (belonging to three subtype allele families) were observed, with 92% of specimens belonging to the common allele family IIa and the unusual allele family IId. Thus, the transmission of cryptosporidiosis in Kuwaiti children differed significantly from other tropical countries.Cryptosporidiosis is a significant cause of diarrheal diseases in both developing and industrialized nations. Recent molecular epidemiologic studies of cryptosporidiosis have helped researchers to better understand the transmission of cryptosporidiosis in humans and the public health significance of Cryptosporidium spp. in animals and the environment. Using genotyping tools, five species of Cryptosporidium (C. hominis, C. parvum, C. meleagridis, C. felis, and C. canis) have been shown to be responsible for most human infections. Of these five species, C. hominis and C. parvum are the two most common species (34). Because these five human pathogenic Cryptosporidium species have different spectrums of host specificity, the characterization of Cryptosporidium at the species level is useful in investigating infection and contamination sources. Recently, a number of subtyping tools have been developed and used to characterize the population structure and transmission dynamics of C. parvum and C. hominis (2, 8, 17, 18, 24-26, 29, 30).Although cryptosporidiosis is prevalent in tropical regions, limited studies have been conducted to characterize Cryptosporidium spp. from humans at the molecular level. Several studies have examined the transmission of human cryptosporidiosis in South Africa, Malawi, Kenya, Uganda, Peru, and Thailand, all of which have shown a predominance of C. hominis in humans, indicating anthroponotic transmission plays a major role in the epidemiology of cryptosporidiosis in most tropical countries (7,17,25,(31)(32)(33). Only two of the studies subtyped small numbers of Cryptosporidium spp. (17,25). In the present study, 62 Cryptosporidium-positive specimens were collected from children in Kuwait City between 1997 and 2004 and examined by a small subunit (SSU) rRNA-based PCR-restriction fragment length polymorphism (PCR-RFLP) analysis and a 60-kDa glycoprotein (GP60)-based PCR sequencing tool (2, 33). Results of the study have shown a predominance in children of C. parvum, which traditionally is associated with farm animal...

To address the source of infection in humans and public health importance of Giardia duodenalis parasites from animals, nucleotide sequences of the triosephosphate isomerase (TPI) gene were generated for 37 human isolates, 15 dog isolates, 8 muskrat isolates, 7 isolates each from cattle and beavers, and 1 isolate each from a rat and a rabbit. Distinct genotypes were found in humans, cattle, beavers, dogs, muskrats, and rats. TPI and small subunit ribosomal RNA (SSU rRNA) gene sequences of G. microti from muskrats were also generated and analyzed. Phylogenetic analysis on the TPI sequences confirmed the formation of distinct groups. Nevertheless, a major group (assemblage B) contained most of the human and muskrat isolates, all beaver isolates, and the rabbit isolate. These data confirm that G. duodenalis from certain animals can potentially infect humans and should be useful in the detection, differentiation, and taxonomy of Giardia spp.

Cryptosporidium parvum and Cryptosporidium hominis isolates from human immunodeficiency virus-infected patients, cattle, and wild ruminants were characterized by PCR and DNA sequencing analysis of the 60-kDa glycoprotein gene. Seven alleles were identified, three corresponding to C. hominis and four corresponding to C. parvum. One new allele was found (IId), and one (IIb) had only been found in Portugal. Isolates from cattle and wild ruminants clustered in two alleles. In contrast, human isolates clustered in seven alleles, showing extensive allelic diversity.