Effects of breastfeeding and naturally acquired immunity on infection with {\it Giardia lamblia}: A study in a cohort of Mexican infants

Giardia lamblia is one of the most common causes of gastrointestinal tract infection among young children worldwide. Yet host protection against this parasite and the effect of infection with Giardia on infant growth are poorly understood. It was hypothesized that among young children, protection against infection with Giardia is afforded by breastfeeding and previous infection with the parasite and further, that infection with Giardia decreases growth velocity. From 4/88 to 4/90, 197 infants in a poor area of Mexico City were followed from 0 to 18 months of age, with stool specimens, symptoms and feeding status data collected weekly. A total of 6,031 stool specimens were tested for Giardia antigen by enzyme-linked immunosorbent assay. There were 1.0 Giardia infections per child-year; 25% were symptomatic and 54% lasted more than 1 month; 94 infants had 1, and 33 had 2 or more infections. Breastfeeding status was coded and analyzed for each child-week of follow up. 91% of study infants were breastfed from birth, 57% at 6 months and 38% at 12 months of age. Rate ratios for non-breastfeeding adjusted for confounding factors were calculated from stratified analyses and the Cox proportional hazards model. Not breastfeeding was a significant risk factor for first infection with Giardia vs. any breastfeeding (adjusted RR = 1.8; 1.1, 2.8) at all ages; a dose response was demonstrated by degree of breastfeeding. The adjusted rate ratio for non-breastfeeding vs. partial breastfeeding was 1.6 (1.03, 2.6) and for non-breastfeeding vs. complete breastfeeding was 4.7 (1.4, 15.9). Among Giardia infected infants, breastfeeding did not protect against diarrheal symptoms or shorten the duration of carriage. First and repeat infections with Giardia did not differ in duration or the percent symptomatic. The analysis of growth and Giardia infection was inconclusive but suggested that a history of Giardia infection might be associated with decreased weight velocity, while an immediate chronic infection might be associated with increased weight velocity. In summary, these data indicate that breastfeeding protects infants against infection with Giardia; provide no evidence of protection against repeat infections resulting from a prior infection and suggest but do not establish that a history of Giardia infection might be associated with decreased growth in young children. ^

A STUDY OF ILLNESS AND RESERVOIRS ASSOCIATED WITH GIARDIA LAMBLIA IN RURAL EGYPT

A longitudinal investigation of the health effects and reservoirs of Giardia lamblia was undertaken in forty households located in a rural Nile Delta region of Egypt. Stool specimens obtained once weekly for six months from two to four year old children were cyst or trophozoite-positive in 42 percent of the 724 examined. The mean duration of excretion in all but one Giardia-negative child was seven and one-half weeks with a range of one to 17 weeks. Clinical symptoms of illness were frequently observed within a month before or after Giardia excretion in stool of children, but a statistical inference of association was not demonstrated.^ Seventeen percent of 697 specimens obtained from their mothers was Giardia-positive for a mean duration of four weeks and a range of one to 18 weeks. Mothers were observed to excrete Giardia in stool less frequently during pregnancy than during lactation.^ Nine hundred sixty-two specimens were collected from 13 species of household livestock. Giardia was detected in a total of 22 specimens from cows, goats, sheep and one duck. Giardia cysts were detected in three of 899 samples of household drinking water.^ An ELISA technique of Giardia detection in human and animal stool was field tested under variable environmental conditions. The overall sensitivity of the assay of human specimens was 74 percent and specificity was 97 percent. These values for assay of animal specimens were 82 percent and 98 percent, respectively.^ Surface antigen studies reported from the NIH Laboratory of Parasitic Diseases show that antigens of three Egyptian human isolates are different from each other and from most other isolates against which they were tested.^ The ubiquity of human and animal fecal contamination combined with estimates of ill days per child per year in this setting are substantial arguments for the introduction of a suggested mass parasite control program to intervene in the cyclical transmission of agents of enteric disease. ^

TRANSMISSION DYNAMICS OF ENTERIC BACTERIA IN DAY-CARE CENTERS, HOUSTON, TEXAS

An investigation was undertaken to evaluate the role of fomites in the transmission of diarrhea in day-care centers (DCC) and to elucidate the paths by which enteric organisms spread within this setting.^ During a nine-month period (December 1980-August 1981) extensive culturing of inanimate objects, as well as children and staff was done routinely each month and again repeated during diarrhea outbreaks. Air was sampled from the classrooms and toilets using a Single-Stage Sieve Sampler (Ross Industries, Midland, VA.). Stool samples were collected from both ill and well children and staff in the affected rooms only during outbreaks. Environmental samples were processed for Shigella, salmonella and fecal coliforms while stools were screened for miscellaneous enteropathogens.^ A total of 11 outbreaks occurred in the 5 DCC during the study period. Enteric pathogens were recovered in 7 (64%) of the outbreaks. Multiple pathogens were identified in 3 outbreaks. The most frequently identified pathogen in stools was Giardia lamblia which was recovered in 5 (45%) of the outbreaks. Ten of the 11 (91%) outbreaks occurred in children less than 12 months of age.^ Environmental microbiology studies together with epidemiologic information revealed that enteric organisms were transmitted from person-to-person. On routine sampling, fecal coliforms were most frequently isolated from tap handles and diaper change areas. Contamination with fetal coliforms was wide-spread during diarrhea outbreaks. Fecal coliforms were recovered with significantly greater frequency from hands, toys and other classroom objects during outbreaks than during non-outbreak period. Salmonella typhimurium was recovered from a table top during an outbreak of Salmonellosis. There was no association between the level of enteric microbial contamination in the toilet areas and the occurrence of outbreaks. No evidence was found to indicate that enteric organisms were spread by the airborne route via aerosols.^ Toys, other classroom objects and contaminated hands probably play a major role in the transmission of enteropathogens during day-care center outbreaks. The presence of many enteric agents in the environment undoubtedly explains the polymicrobial etiology of the day-care center associated diarrhea outbreaks. ^

Is H. pylori infection associated with diarrhea in a cohort of 3- to 8-year-old Colombian children?

The Estudio Comunitario sobre la Salud del Niño cohort study followed 326 3- to 8-year-old Colombian children for 4 years to observe the natural history of Helicobacter pylori infection and identify risk factors for acquisition, recurrence and persistence. Acute H. pylori infection during childhood may predispose to other enteric infections and therefore increase the risk of diarrheal disease. This dissertation aimed to estimate the effect of H. pylori infection on the occurrence of diarrhea and parasitic co-infections. The analysis used Generalized Estimating Equations to obtain odds ratios to estimate relative risks for diarrhea and the Zhang-Yu algorithm to estimate relative risks for on parasitic infections. Andersen-Gill models were used to estimate rate ratios for the effect of H. pylori status on the recurrence of parasitic infections. H. pylori status was classified for the entire follow-up duration in 1 of 3 categories: persistently positive, intermittently positive, and persistently negative. Multivariable models included child’s sex, age, symptoms, medication use, and socio-environmental factors. H. pylori infection was weakly and imprecisely associated with diarrheal disease, which occurred at an unexpectedly low frequency in this study. Persistently H. pylori-positive children had a somewhat higher incidence of reported diarrhea than intermittently positive or persistently negative children. Stratified analysis revealed that the presence of specific helminthes modified the effect of persistent H. pylori infection on diarrhea. The incidence of any parasitic infections was higher in children with persistent H. pylori infection relative to those with intermittent or persistently negative status, but this association did not hold when adjusted for the full set of selected covariates. The effects of H. pylori persistent status were similar for the occurrence or recurrence of Giardia duodenalis, Entamoeba histolytica, and Ascaris lumbricoides. These results show that H. pylori frequently co-exists with other parasites in Andean children and suggest that intermittently H. pylori–positive children might be at a lower risk of parasitic infections than persistently positive children. The relationship of H. pylori infection, helminthic infection and diarrheal disease should be further explored in studies that devote more intensive resources to accurate ascertainment of diarrhea.^