Clearance of soluble egg antigen in schistosoma haematobium infection in children after praziquantel treatment
Schistosomiasis, a disease caused by trematode worms of the genus Schistosoma, afflicts both humans and animals. Schistosoma mansoni and Schistosoma haematobium are the two most important human species found in Africa. The schistosome life cycle involves an alteration of generations in two different hosts, with the asexual multiplying stage in the intermediate snail host (biomphalaria or Bulinus) species and a sexual non-multiplying stage in the definitive host (human). Mature adult female worms deposit eggs into the mesenteric veins of the small intestine or blood vessels around the plexus of the bladder. Diagnosis of schistosomiasis is based on microscopic detection of eggs in urine/stool or abdomen scanning using ultrasound machine or reaction of reagent strips dipped in urine. There methods are cumbersome, time consuming, inaccurate and expensive. Recently, an enzyme linked immuno-sorbent assay for detection of S.haematobium soluble egg antigen (SEA) has been developed. Detection of the antigen derived from the eggs in urine and those trapped in the tissues, is a non-invasive method that is simple, specific, reliable and gives an indication of an active infection. The objective of the study was to establish whether or not there is an age and sex-related difference in the clearance of SEA and whether SEA can serve as a maker of pathology. This study was conducted in Jimba location, Kilifi District, Coat Province of Kenya, where S.haematobium is endemic. Urine from schoolchildren aged between 4-18 years were examined for eggs of S.haematobium using urine samples filtration technique. ELISA was performed on urine samples from children examined for egg counts. The overall prevalence of S.haematobium was 92.8% with higher infection rates in males (95.45%)than in females (89.50%). All schistosome egg positive children (a total of 372) were treated with a single oral dose 40-mg of praziquantel per kg body weight. A cohort of one hundred and fifty eight pupils consistently participated in the study. Follow up was conducted over a period of 33 days. Both the clearance of SEA and egg counts showed a gradual significant decrease after praziquatel treatment. There was a significant difference in the prevalence of S.haematobium between male and female children (t=2.164, P<0.05). There was no statistical difference in the clearance of SEA and egg counts in urine between male and female children. There was also a significant difference between the egg count clearance in age groups < 5 years and 9-11years P=0.012), and 12-14 years (P=0.019 respectively. 9-11 years. Comparison of SEA clearance among the various age groups indicated a significant difference between age groups < 5 years and 6-8years (P=0.012), 9-11 years (P=0.003) and 12-14 years (P=0.006) respectively. The results showed that there was a correlation between clearance of S.haematobium soluble egg antigen and egg counts in urine of infected children (pearson's correlation coefficient) (r= 0.981, P<0.010). Also S.haematobium SEA would be detected in urine even when there were no eggs being excreted any more. The results would be helpful in the development of a SEA based assay for field diagnosis of morbidity in endemic areas. These results suggest that SEA assay can be used in S. haematobium endemic areas where prevalence is high or low and is highly sensitive irrespective of age or sex of the children.