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Diarrhea in patients with acquired immunodeficiency syndrome (AIDS) may cause malabsorption of medications and failure of antiretroviral therapy (ART). We prospectively evaluated human immunodeficiency virus-1 (HIV-1)-infected patients with and without chronic diarrhea initiating ART in Haiti. We report mean plasma antiretroviral concentrations at 2 and 4 weeks. We measured plasma HIV-1 RNA levels at four points. Fifty-two HIV-1-infected patients (26 matched pairs) were enrolled. No differences in antiretroviral concentrations were detected. At week 24, 18/25 (72%) cases and 16/24 (68%) controls had undetectable plasma HIV-1 RNA levels (P = 0.69). Patients with plasma HIV-1 RNA levels > 50 copies/mL at week 24 had lower early efavirenz concentrations than patients with undetectable HIV-1 RNA (2,621 ng/mL versus 5,278 ng/mL; P = 0.02). Diarrhea at ART initiation does not influence plasma concentrations of the medications evaluated. Virologic outcome at Week 24 does correlate with efavirenz concentrations early in therapy but not with the presence of chronic diarrhea.

Infection with the human pathogenic parasite Entamoeba histolytica has not been well-characterized in northeastern Brazil. In this study, the prevalence of E. histolytica infection in a slum in northeastern Brazil was assayed using an enzyme-linked immunosorbent assay (ELISA) for antibodies against the galactose/N-acetyl-D-galactosamine (Gal/GalNAc)-inhibitable adherence lectin of E. histolytica. Sera from a total of 335 individuals were examined for anti-Gal/GalNAc lectin antibodies. The overall seropositivity was 24.7%; 29.4% of females and 19.4% of males were positive. Among different age groups there was a peak of 40% positivity in the 6-14-year-old age group. There was also familial clustering of seropositivity. To examine colonization, stool samples from 155 people were examined microscopically for the presence of the parasite. Fourteen of 155 stools (9.0%) were identified as containing E. histolytica or nonpathogenic E. dispar. These 14 positive stools were analyzed with an ELISA that detects Gal/GalNAc lectin antigen and can distinguish between E. histolytica and E. dispar. Four stools (29%) were positive for E. histolytica and the remaining 10 were identified as E. dispar-positive. Although the overall colonization rate by microscopy was only 9%, with a third identified as E. histolytica, up to 40% of older children develop serologic evidence of having experienced pathogenic E. histolytica infection. The results of this study demonstrate that this community in northeastern Brazil is highly endemic for E. histolytica with infection rates similar to other developing nations.

The mean +/- SEM duration of diarrheal episodes decreased from 7.1 +/- 2.2 days to 4.3 +/- 0.9 days (P < 0.05) while the incidence of diarrheal episodes remained steady (2.2 +/- 0.3 versus 2.4 +/- 0.5 episodes; P = not significant) between two three-month periods before and after the oral administration of a single large age-adjusted dose of vitamin A among children at historical risk for persistent diarrhea in an impoverished Brazilian community.

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.

Diarrheal diseases hold profound messages as well as opportunities that range from public health to basic science. From the spread of cholera around the world, we are reminded of the global impact of tropical diseases, that disease may provide a litmus test for poverty to drive a sanitary revolution, that disease spread may be worsened by political denial, and that many ecologic and epidemiologic secrets such as interepidemic microbial niches remain poorly understood. Diarrheal diseases other than cholera teach us that heavy disease burdens do not control population growth but are associated with population overgrowth (i.e., improved health is key to controlling the population explosion), the societal impact of diarrhea morbidity may exceed even that of its mortality, that new agents continue to emerge, and that nosocomial diarrhea is an underrecognized threat in our hospitals. Finally, from the laboratory of the developing world also come messages for basic science. Microbial toxins continue to elucidate a new understanding of cell signaling, and mechanisms once thought to be clear (such as that of cholera toxin) now appear much more complex. Traditional remedies hold new pharmacologic secrets, e.g., such as gingko extracts that inhibit platelet-activating factor. Finally, from basic physiology can come widely applicable practical solutions such as oral rehydration therapy and simplified diagnostics for inflammatory diarrhea. Health problems such as diarrheal diseases that plague the disadvantaged are linked to population overgrowth and provide some of the greatest challenges to modern science and the industrialized world.

Cryptosporidium is an important cause of diarrheal disease in children worldwide. To elucidate the environmental sources of this parasite, we selected an urban slum in Fortaleza, Brazil, a community with a known high incidence of cryptosporidiosis, and examined both stool smears from household animals (n = 127) and filtrates from local water sources (n = 18) for Cryptosporidium oocysts. Because previous work in this community has demonstrated the seasonal nature of human infection with Cryptosporidium, collections were made separately for the dry and rainy seasons. Of the 64 stools collected during the dry season (September-December 1990), four (6.3%) were positive by acid-fast staining for Cryptosporidium. Of the 63 rainy season samples (March-May 1991), nine (14.3%) were positive. Overall, oocysts were detected in 13 (10.2%) of 127 animal stool samples. Freshwater samples were obtained from a variety of sources including open and closed wells, and running city water and then processed. Four of 18 samples (22.2%), including a sample from city water were positive by at least one of two staining techniques (acid-fast and immunofluorescence). In summary, animals may serve as a reservoir of Cryptosporidium, with potential for the contamination of immediate household water sources. These findings may help to explain the high incidence of cryptosporidiosis among infants in this impoverished community.

Diarrhea and malnutrition, alone or together, constitute major causes of morbidity and mortality among children throughout the tropical world. Data from northeast Brazil, taken with numerous other studies, clearly show that diarrhea is both a cause and an effect of malnutrition. Diarrheal illnesses impair weight as well as height gains, with the greatest effects being seen with recurrent illnesses, which reduce the critical catch-up growth that otherwise occurs after diarrheal illnesses or severe malnutrition. Malnutrition (whether assessed by impaired weight or height for age) leads to increased frequencies and durations of diarrheal illnesses, with a 37% increase in frequency and a 73% increase in duration accounting for a doubling of the diarrhea burden (days of diarrhea) in malnourished children. A multi-pronged approach focusing on those with prolonged diarrhea and severe malnutrition is suggested.

In order to develop an experimental model of symptomatic cryptosporidiosis in an immunosuppressed mammal, we investigated the pathophysiology of infection with Cryptosporidium and the humoral and cellular host responses in rnu/rnu (athymic) rats and their heterozygous (rnu/+) littermates by challenging suckling rats with greater than or equal to 2.5 x 10(6) Cryptosporidium oocytes oro-gastrically. Normal and immunodeficient animals were followed for onset and duration of infection (fecal oocysts), physiologic consequences (diarrhea, impaired weight gain, brush-border enzyme activities), and immunologic response (both B- and T-lymphocyte-mediated). Homozygosity for the rnu gene was associated with protracted cryptosporidial infections; shedding for up to 52 days occurred, and delay in weight gain was noted in rnu/rnu-infected compared with rnu/rnu-uninfected rats (p less than 0.05). In contrast, cryptosporidial challenge of rnu/+ rats resulted in self-resolving infections, occasionally with transient diarrhea lasting four days or less occurring 10-15 days after oro-gastric challenge. The latter animals mounted a cell-mediated immune response to Cryptosporidium: three months after challenge, five of five rnu/+ rats demonstrated positive skin test responses to a subcutaneous 3.5 micrograms dose of cryptosporidial antigen. Further, sera from 6 rnu/+ rats taken two to three months after oro-gastric oocyst challenge exhibited specific anticryptosporidial immunoglobulin binding (A405 = 0.96), compared to that of seven uninfected rnu/+ controls (A405 = 0.09, P less than 0.02). Macromolecules of 150, 105, and 88 kD in the Cryptosporidium antigen preparation were bound by serum immunoglobulin from previously infected, recovered rnu/+ rats. Two brush-border enzymes (lactase and alkaline phosphatase) were markedly reduced in the ileum 8-10 days after oro-gastric challenge in rats with diarrhea and oocyst shedding. We find the rnu/rnu (athymic, nude) rat provides a useful model for study of prolonged cryptosporidial infection with impaired weight loss, brush-border enzyme alteration and intermittent diarrhea. These studies further suggest that a T-lymphocyte population is involved in recovery from Cryptosporidium infection and that this recovery is associated with both cellular and humoral immune responses to specific cryptosporidial antigenic macromolecules. This model should open further avenues for the study of the pathogenesis and protective immunity in cryptosporidial infection.

The etiology of diarrhea in children and adults on the Navajo Indian Reservation was investigated in August 1975. Fifty-six ill individuals and 37 controls were included in the study. Shigella was most commonly associated with diarrhea, and was isolated from 32% of ill children and adults. Fifty percent of Shigella isolates tested were resistant to ampicillin. Heat-stable enterotoxin-(ST)-producing organisms were associated with noninflammatory diarrhea in adults (27% of these cases had ST-producing strains) but not in children. Heat-labile enterotoxin-producing organisms were found among controls as well as individuals with diarrhea. No children had evidence of rotavirus infection. These findings suggest that ST-producing organisms are important causes of sporadic cases of noninflammatory summer diarrhea among Navajo adults and confirm the importance of Shigella in inflammatory diarrhea among adults and children in this setting.

Fecal specimens from 101 patients with diarrhea were cultured and also examined with methylene blue for leukocytes. Thirty-six patients had leukocytes in their stools and 29 had culture-proven shigellosis. The sensitivity of fecal leukocytes in shigellosis was 95% (19/20) when cup specimens were obtained, and 44% (4/9) when swab or diaper specimens were examined. Only 45% of the patients with shigellosis who provided cup specimens had grossly bloody dysentery. Twelve other patients had fecal leukocytes but no demonstrable invasive bacterial pathogens. Methylene blue examination was useful in identifying motile trophozoites of Giardia lamblia and eggs or larvae of other heavy intestinal paraistic infections. Among patients with naturally-acquired acute diarrhea, methylene blue examination of stools for leukocytes is much more sensitive than examination for blood in predicting a positive culture for Shigella spp. It is also of value in detecting parasites.