Evidence of long term benefit of morbidity reduction due to praziquantel treatment against schistosoma mansoni in Kigungu fishing village in Entebbe, Uganda

Praziquantel (PZQ) is efficacious against Schistosoma mansoni. This was prospective cohort study. This study was carried out at Kigungu fishing village, Entebbe, Uganda. The goal of the study was to establish cost effective regiment for mass drug administration (MDA) of Praziquentel in the morbidity reduction of S.mansoni infection. In January 2004, nine hundred and forty five (945) participants were registered in this study. Our analysis was based on examining microscopically three slides prepared from each of 945 stool specimens delivered by each of the participant using modified Kato/Katz method. These included male and female, children and adults living in Kigungu fishing village in Entebbe Uganda. In total 901, cohorts were re-examined for infections clearance six months later in July 2004 and 18 months later in June 2005, 625 cohorts were again re-evaluated for S.mansoni infections after the baseline study. At baseline, (448) of 945 (47.5%) cohorts were S. mansoni positive. All these participants were treatment with a single oral dose of praziquantel at 40mg/kg. At the same time, 495 (52.5%) were S. mansoni negative. Of the 625 (66.3%) cohorts who came back for final review, 80 (12.8%) were still positive for S. mansoni while 210 (33.6%) remained negative after the base line treatment with praziquantel. On the other hand 103 (16.3%) of cohorts who were initially negative at the base line became S.mansoni positive after 18 months and 213(34.1%) remained negative for S.mansoni. The force of re-infection after six months was significant {(P=0.0001),(OR 0.47) CI at 95% (0.31-0.71)}. Nevertheless the force of reinfection was not significant after 18 months {(P=0.766), (OR 0.95) CI at 95% (0.68-1.34)}.The geometric mean eggs excretion of the 80 cohorts who were S.mansoni positive at 18 months was 151.967.This did not reach the geometric mean egg excreted by the same cohorts at baseline which was 285.05. The egg excretion was reduced by 46.8%. Similarly there was marked decrease in clinical symptoms amongst the cohorts. Our study suggests evidence of long-term benefit of praziquantel in Kigungu and that a yearly administration of praziquantel to the community could be a regiment for mass drug administration (MAD) for this community to control schistosomiasis morbidity

Effect of seasonal rainfall and other environmental changes, on snail density and infection rates with Schistosoma mansoni fifteen years after the last snails' study in Kigungu, Entebbe, Uganda.

BACKGROUND: The last study on snail population density in relation to rainfall pattern in Kigungu canoe landing and recreational sites on Lake Victoria shore was earlier carried out about fifteen years ago. This study also reviewed the influence of other environmental factors on the snails' infection rate. OBJECTIVE: To reassess the density dynamic of Biomphalaria (B) choanomphala and Biomphalaria (B) pfeifferi, which act as the intermediate host for S. mansoni and Bulinus (B) globosus, and Bulinus (B) tropicus, which act as intermediate host for S. haematobium. DESIGN: Retrospective study. SETTING: Busy canoe landing sites along Lake Victoria in Kigungu fishing village were selected for the snail sampling. RESULTS: Nine thousand one hundred and ninety four B. choanomphala were collected over the study period. The numbers of B. choanomphala collected in each yearwas 4742 (51.6%) and 4452 (48.4%) in 2004 and 2005 respectively. Of the 4742 B. Choanomphala collected in 2004, 82 (1.7%) shed human cercariae and 329 (6.7%) shed non-human cercariae. Whereas in 2005, out of 4452 B. choanomphala collected 302 (6.85%) shed non-human cercariae and 82 (1.8%) shed human cercariae. Similarly, 4173 B. pfeifferi were also collected in the same period. Out of which 2224 (53.3%) were collected in 2004 and 1949 (46.7%) in 2005. For B. pfeifferi, 42 (1.9%) out of 2224 snails collected in 2004 shed human cercariae and 246 (11.1%) shed non-human cercariae. While in 2005, 33 out of 1949 snails (1.7%) shed human cercariae and 159 (8.2%) shed non-human cercariae. Other snails of medical importance collected included 292 B. globosus and 3094 B. tropicus. None of the Bulinus spp. collected shed any human cercariae but 37 (2.1%) and 30 (2.3%) B. tropicus shed non-human cercariae in 2004 and 2005 respectively. In 2004 and 2005, the area received, 1729mm and 1959mm of rainfall respectively, The mean rainfall during the year was 144.05 mm and 163.3 mm in 2004 and 2005 respectively. There was a negative correlation between rainfalls and snail density dynamic. CONCLUSION: We have found in this study that in spite of the bush clearing of the papyrus swamps which originally was the major habitats for B. choanomphala, B. pfeifferi and the Bulinus spp the intermediate host for schistosome at all canoe landing sites at Kigungu, these snails are still present. Moreover, that their population density dynamic and infection rate are inversely proportional to the rainfall pattern.