Diagnosis is crucial for controlling giardiasis. We determined the prevalence and genetically characterize isolates of Giardia duodenalis of children and dogs from rural communities in northeastern Brazil. G. duodenalis cysts were concentrated by centrifugal flotation/sedimentation. Molecular characterization was carried out using the loci ssu-rRNA, bg, tpi, and gdh. By parasitological techniques, Giardia spp. infection was detected in 72/192 children (37.5%; 95% CI: 30.6%-44.7%) and 24/139 dogs (17.3%; 95% CI: 11.4%-24.6%). By molecular analysis, infection was detected in 60/141 children (42.5%; 95% CI: 34.3%-51.2%) and 26/92 dogs (28.3%; 95% CI: 19.4%-38.6%). The total prevalence of giardiasis was 54.9% in children (106/193; 95% CI: 47.1%-61.6%) and 32.9% in dogs (47/143; 95% CI: 25.2%-41.2%). Zoonotic assemblages A and B of G. duodenalis were detected in children, and assemblage E of G. duodenalis was detected in one child and two dogs. Parallel use of parasitological and molecular techniques proved to be a more effective strategy for detecting giardiasis in children and dogs from endemic areas.

Diagnosis is crucial for the control and prevention of diarrheal diseases such as giardiasis and cryptosporidiosis. The aim of this study was to determine the prevalence and genetically characterize isolates of Giardia duodenalis and Cryptosporidium spp. of 143 children and 193 dogs from 40 rural communities in northeastern Brazil. G. duodenalis cysts were concentrated by centrifugal-flotation/sedimentation. Molecular characterization of the isolates was carried out using the loci small subunit ribosomal RNA, beta-giardin, triosephosphate isomerase, and glutamate dehydrogenase for Giardia and with the locus 60-kDa glycoprotein for Cryptosporidium. By parasitological techniques, Giardia was detected in 72/192 (37.5%; 95% CI: 30.6%-44.7%) children and 24/139 (17.3%; 95% CI: 11.4%-24.6%) dogs. By molecular analysis, infection was detected in 60/141 children (42.5%; 95% CI: 34.3%-51.2%) and 26/92 dogs (28.3%; 95% CI: 19.4%-38.6%). The total prevalence of giardiasis, considering the result of parasitological and molecular techniques, was 54.4% (105/193; 95% CI: 47.1%-61.6%) in children and 32.9% (47/143; 95% CI: 25.2%-41.2%) in dogs. Zoonotic assemblages A and B of G. duodenalis were detected in children, and assemblage E of G. duodenalis was detected in one child and two dogs. Cryptosporidium was detected in 36/191 children (25.5%; 95% CI: 13.6%-25.1%) and 4/92 dogs (4.4% 95% CI: 1.2%-10.7%). Cryptosporidium parvum was detected in one children. The parallel use of parasitological and molecular techniques proves to be a more effective strategy for detecting giardiasis in endemic areas. This study is the first report of assemblage E in dogs from northeastern Brazil.