Seroepidemiologic study of Cryptosporidium infection in children from rural communities of Anhui, China and Fortaleza, Brazil.

A cluster-sampling, cross-sectional study was conducted for assessing the prevalence of Cryptosporidium infection in children less than 16 years of age from three villages, Dondian, Linshan, and Fuziyin, in rural Anhui in eastern China. Among 320 apparently healthy children less than 10 years of age from Dondian who had stool specimens collected, cryptosporidial oocysts were found in stools of three children from Dondian, and no positive specimens were found in 239 children studied from Linshan. In addition, a total of 610 serum samples from children in these three villages were tested for specific IgG antibody to Cryptosporidium with an enzyme-linked immunosorbent assay (ELISA) and the prevalence rates were 42.3%, 51.7%, and 57.5%, respectively, in Dondian, Linshan, and Fuziyin. Seroprevalence increased progressively with age. No detectable antibody was found in infants between two and six months of age, and seropositivity steadily increased after one year of age. Among 36 sera from adults 15-60 years of age without diarrheal illness in Huanglu villages of rural Chaohu, 50% (18 of 36) were positive. As expected, a good correlation was found in the specific IgG antibody between the paired serum specimens from 30 matched mother-neonates who showed transplacental transfer of IgG. However, little or no IgM antibody was seen in the neonates even though several mothers had a positive anticryptosporidial IgM enzyme-linked immunoassay result. Forty randomly selected serum samples from children less than four years of age in a similarly impoverished semiurban community in Fortaleza, Brazil, where the majority of households also have pit toilets and shared community water supplies and 172 serum samples from patients one month to 29 years of age admitted to the University of Virginia Hospital without diarrhea were also examined. In Fortaleza, almost all children acquired antibody by their second year of life, demonstrating the high prevalence of this infection. In rural Anhui, only about half the children were infected by 5-7 years of age. The overall prevalence rate (16.9%) of seropositivity among children and young adults in Virginia was much lower than in China and Brazil. These results indicate that cryptosporidial infection is ubiquitous, and is highly endemic in these impoverished communities. The difference between China and Brazil may reflect earlier weaning, hygiene practices, poorer water or sanitation, multiple siblings in family and geographic environment in Brazil.

Cryptosporidiosis: Pathogenesis and immunology.

Cryptosporidium parvum is an increasingly recognized agent of intestinal infection in normal and immunocompromised humans, and in many other animals. The intraepithelial cell infection results in villous atrophy, mild submucosal inflammation, reduction of brush-border enzymes and a characteristic persistent watery diarrhea. The infection is self-limiting in immunocompetent hosts, probably because of specific acquired immunity; specific serum and secretory antibody responses develop that may be required for clearance and protection against reinfection. Passive milk antibody, especially i f in high titers, may be partially protective but severe, persistent infection in athymic rodents and humans with AIDS demonstrate that T cells are essential for controlling the infection. Specific anti-bodies and lymphocyte extracts have been tested in cases of cryptosporidiosis but the interpretation of the results remains controversial. Here, Shu-Xian Zu, Guo-Dong Fang, Ronald Foyer and Richard Guerrant emphasize that effective treatment and prevention remain dependent on advances in our understanding of the host cell-parasite relationship.

Household epidemiology of Cryptosporidium parvum infection in an urban community in northeast Brazil.

OBJECTIVE: To examine the transmission of Cryptosporidium infection in households with an identified person with cryptosporidiosis. DESIGN: Prospective cohort study. SETTING: An urban slum in Fortaleza, Brazil. PARTICIPANTS: Thirty-one households with a child less than 3 years of age (index case) who was positive for Cryptosporidium parvum using acid-fast and auramine-stained stool smears. MEASUREMENTS: Three stool samples (at 0, 2, and 6 weeks after identification of the index case) and two serum samples (0 and 6 weeks) were collected from each family member in households with an index case of Cryptosporidium infection. RESULTS: Forty-five percent of index cases of Cryptosporidium infection were associated with persistent (> 14 days) diarrhea. Secondary cases of Cryptosporidium infection were identified either by stool examination or seroconversion in 18 (58%) of 31 households involving 30 persons, yielding an overall transmission rate of 19%. Of the 202 persons in this study with at least one serum sample available for analysis, 191 (94.6%) had evidence of antibodies (either IgM or IgG) to Cryptosporidium. CONCLUSIONS: Cryptosporidium parvum is highly transmissible and infective in the family setting, with transmission rates similar to other highly infectious enteric pathogens such as Shigella species. These data are cause for added concern because of the rapidly increasing rate of seropositivity for human immunodeficiency virus.

PIP: Between December 1990 and April 1992 investigators enrolled 31 households with a less than 3-year-old child infected with Cryptosporidium parvum in a prospective cohort study to determine the infectivity of Cryptosporidium parvum in families living in crowded conditions, mainly in the Goncalves Dias slum in Fortaleza, Brazil. The median household size was 7. The median age of the 33 index cases was 11 months, while the median age of the 192 family contacts was 21 years. 94% of the index cases had diarrhea at the time Cryptosporidium infection was diagnosed. 45% of the index cases had persistent diarrhea ( 14 days). The median duration of diarrhea was 14 days (range, 1-84 days). Most index cases (83%) had at least 1 other positive stool test for Cryptosporidium. Just 1 index case shed oocysts for 6 weeks. Index cases transmitted Cryptosporidium infection to 30 (19%) of 182 household contacts as evidenced by either a positive stool examination or seroconversion. These 30 secondary cases were from 18 of the 31 households. Only 8 (27%) secondary cases had diarrhea and 25% of them had persistent diarrhea, suggesting preexisting protective immunity in this area where Cryptosporidium infection is endemic. Household contacts who were 5 years old or younger were significantly more likely to have been diagnosed with Cryptosporidium than were those older than 5 years (30% vs. 5%; p 0.001). Most persons with at least 1 serum sample available for analysis (191/202 = 94.6%) had antibodies (IgM or IgG) to Cryptosporidium. The high rate of transmission of Cryptosporidium in this population, the serious threat of persistent diarrhea among young children, and the ever increasing rate of HIV transmission in Brazil (especially among slum dwellers with no access to condoms and to education about AIDS) should raise great concern.