RESUMEN
We used a solid-phase enzyme immunoassay to determine the age-specific rates of acquisition of antibody to Giardia lamblia in populations living in an inner city area of Baltimore, Md., on an Apache Indian reservation in Arizona, in a rural area of Panama, and in an urban area of Peru (Lima). Antibody to G. lamblia was found in a portion of the adults living in all of the study areas. Similar prevalence rates and quantitative levels of antibody were found in the adults living in Arizona (44%), Panama (48%), and Peru (46%). However, a significantly lower (P less than 0.05) percentage of the adults living in Baltimore (18%) displayed serological evidence of infection. Different patterns of age-associated acquisition of antibody were noted in the study populations. In the United States, children living in Baltimore had low levels of seropositivity throughout childhood, whereas children living on the Arizona Indian reservation showed a progressive acquisition of antibody early in childhood, with adult levels achieved by 8 years of age. In Latin America, children living in Panama attained adult levels of seropositivity between 9 and 20 years of age, whereas children in Peru displayed adult levels of seropositivity in the first 6 months of life. Our findings documented the widespread occurrence of G. lamblia infections in diverse populations. Children living in different areas and under different environmental conditions displayed widely differing rates of acquisition of antibody to G. lamblia, possibly resulting from different levels of sanitation, water contamination, and person-to-person contact. Our studies indicate that quantitative solid-phase immunoassays can be used to study the epidemiology of parasitic infections such as those caused by G. lamblia.
Asunto(s)
Anticuerpos/análisis , Giardia/inmunología , Giardiasis/epidemiología , Adolescente , Adulto , Factores de Edad , Arizona , Niño , Preescolar , Ensayo de Inmunoadsorción Enzimática , Humanos , Lactante , Maryland , Panamá , Perú , Estudios Prospectivos , Población Rural , Población UrbanaRESUMEN
We used an enzyme-linked immunosorbent assay system to compare prevalence and levels of systemic and local antibody to Giardia lamblia in different populations. Serial blood and milk samples were collected simultaneously from lactating women in Texas and Mexico. IgG antibody to G. lamblia was present in 118 (77%) of 153 sera from 27 Mexican mothers but in only 51 (24%) of 214 sera obtained from 28 Texan mothers (P less than .001). Sera positive for IgG antibody to G. lamblia revealed antibody levels that were significantly higher in Mexico than in Texas (0.325 +/- 0.076 vs. 0.219 +/- 0.079 optical density units). Secretory IgA antibody to G. lamblia was found in 121 (79%) of 153 milk samples in the Mexican population, but in only 33 (15%) of 214 samples in the Texan population (P less than .001). The levels of secretory antibody to G. lamblia also were higher in the Mexican population. The study documents a widely different antibody response to G. lamblia in individuals living in different areas. As antibodies to G. lamblia can be acquired by infants transplacentally or through breast-feeding, this difference might be important in the relative protection against giardial infection.