Incidence and detection of Blastocystishominisamong the infants in Dhaka

Abstract

In the present study, three techniques: Direct microscopy, in vitro culture and PCR methods were applied to detect Blastocystis hominis. Multiple stool samples of 406 children were collected from Mirpur, Dhaka and 118 children from Mohammadpur slum area, Dhaka. The whole work was done in the Parasitology Laboratory, icddr,b, Mohakhali, Dhaka-1212. During the study period (from January 2012 to December 2013), in Mirpur area, out of 9322 stool samples, 8601 samples were observed on monthly basis called Monthly Stool (MS) samples and remaining 721 samples were Diarrheal Stool (DS) samples. In Mohammadpur area, out of 3218 stool samples, 2704 samples were MS samples and remaining 514 samples were DS samples. By microscopy, the prevalence of B. hominis in MS and DS samples were 3.72% and 5.83% in Mirpur area and 7.25% and 9.73% in Mohammadpur area respectively. According to culture examination, the prevalence of B. hominis in MS and DS samples were 34.25% and 27.32% in Mirpur area and 42.60% and 40.47% in Mohammadpur area respectively. It was observed that prevalence found higher by in vitro culture method than direct microscopy in all types of samples of both areas. According to age groups of children, it was observed that prevalence was higher among 37-48 and 49-60 months age groups in MS and DS samples of both areas. Statistical analysis exhibited that there was no significant relationship between sexes in children for B. hominis infection. It was observed that female were more infected, by microscopy (4.16%) and by in vitro culture (35.07%) collected from Mirpur area. While, by in vitro culture method, female was more prevalent (42.79%) than male (41.59%) in overall samples from Mohammadpur area. By the analysis of variance it was revealed that there was a significant association between age groups of children for B. hominis infection. Four morphological forms of B. hominis: cyst, vacuolar, amoeboid and granular, which were clearly distinguished by in vitro culture method. Prevalence of cyst, vacuolar, amoeboid and granular forms were 31.09%, 13.63%, 11.50% and 5.88% respectively in stool samples of Mirpur area, while comparatively higher prevalence 38.66%, 29.58%, 18.09% and 2.89% were observed respectively in stool samples of Mohammadpur area. To observe seasonal variation, by microscopy and in vitro culture method, in MS and DS samples of both areas, prevalence of B. hominis were higher both in summer and rainy seasons than winter. The seasonal variation (F-test), were significant (P=0.05* and p=0.000**) in DS samples of Mirpur and Mahammadpur areas. Monthly incidence of B. hominis in stool samples of study areas showed positive correlation with climatic factors (temperature, humidity and rainfall). It was observed that in DS samples of both areas, incidence were significantly correlated with temperature (p=0.004** and p=0.000**) and rainfall (p=0.004** and p=0.001**). The prevalence of B. hominis by direct microscopy was 4.50%, by in vitro culture method was 29.86% while by Real-time PCR method was 42.42% respectively in stool samples of Mirpur area, while these were 9.44%, 39.44% and 53.33% respectively in samples of Mohammadpur area. Comparisons among three methods, showed that the mean difference were highly significant (p=0.013** and p=0.000*) in stool samples of both areas. The main goal of the present investigation was to prove the perfect technique for maximum detection of B. hominis. As a result the Real-time PCR is the gold standard as it showed highest sensitivity than direct microscopy and in vitro culture method.