Despite many current interventions against neglected tropical diseases (NTDs) being highly cost-e... more Despite many current interventions against neglected tropical diseases (NTDs) being highly cost-effective, new strategies are needed to reach the WHO's control and elimination goals. Here we argue for the importance of incorporating economic evaluations of new strategies in decisions regarding resource allocation. Such evaluation should ideally be conducted using dynamic transmission models that capture inherent nonlinearities in transmission and the indirect benefits ('herd effects') of interventions. A systematic review of mathematical models that have been used for economic analysis of interventions against the ten NTDs covered by the London Declaration reveals that only 16 out of 49 studies used dynamic transmission models, highlighting a fundamental--but addressable--gap in the evaluation of interventions against NTDs.
Mathematical modelling of helminth infections has the potential to inform policy and guide resear... more Mathematical modelling of helminth infections has the potential to inform policy and guide research for the control and elimination of human helminthiases. However, this potential, unlike in other parasitic and infectious diseases, has yet to be realised. To place contemporary efforts in a historical context, a summary of the development of mathematical models for helminthiases is presented. These efforts are
Transactions of the Royal Society of Tropical Medicine and Hygiene, 2009
As part of a 4-year control programme beginning in 2003 and entitled Piga Vita Kichocho, around 1... more As part of a 4-year control programme beginning in 2003 and entitled Piga Vita Kichocho, around 140,000 school-aged children on Unguja Island, Zanzibar were treated annually with a combination of praziquantel and albendazole. To provide information on the impact of this intervention, a subset of children, originating from 24 sentinel schools, were monitored in 2004, 2005 and 2006 using both parasitological and behavioural questionnaire methods. Overall, prevalence of urinary schistosomiasis fell by 52%, intensity by 55% and gross haematuria by 82%. There was a positive and statistically significant correlation between areas of elevated disease prevalence and areas of predicted high transmission based upon local occurrence of the permissive intermediate snail host. In areas of low transmission, urinary schistosomiasis was greatly reduced, but, by contrast, other intervention strategies are needed to complement and synergise with chemotherapy in high transmission areas. Whereas significant reductions were documented in the prevalence of both Trichuris trichiura and hookworm, prevalence of Ascaris lumbricoides significantly increased over the monitoring period. Through a detailed analysis of named child records, evidence of predisposition to helminth (re)infection and individual bias towards polyparasitism was detected, highlighting the often overlapping distribution of these parasites within the school-aged child.
To evaluate micro-haematuria, detected by Haemastix reagent strips, for diagnosis of urinary schi... more To evaluate micro-haematuria, detected by Haemastix reagent strips, for diagnosis of urinary schistosomiasis during a 3-year period of school-based control on Zanzibar. A sub-set of school children, from a total of 135,000 who were receiving treatment for urinary schistosomiasis and soil-transmitted helminthiasis, were monitored by parasitological and questionnaire methods for Schistosoma haematobium infections: at treatment baseline in 2004 (n=2002), follow up with re-treatment in 2005 (n=3278) and further follow up with re-treatment in 2006 (n=3993). Standard diagnostic scores for micro-haematuria were calculated against parasitological assessment. Diagnostic scores of Haemastix remained strong throughout the 3-year period. In 2006, scores were: sensitivity (SS)=0.86 (95% CI: 0.86-0.88), specificity (SP)=0.99 (0.98-1.00), positive predictive value (PPV)=0.90 (0.88-0.91), negative predictive value (NPV)=0.98 (0.98-0.99) in boys; and SS=0.84 (0.82-0.86), SP=0.98 (0.98-0.99), PPV=0.77 (0.75-0.79) and NPV=0.99 (0.99-1.00) in girls. By comparison, reported blood in urine and pain upon urination were much lower and not as informative. At a cost of approximately pound sterling 0.20/test, further use of reagent strips for monitoring of urinary schistosomiasis during ongoing control programmes should be advocated as a rapid, cost-effective and informative disease surveillance tool.
Despite many current interventions against neglected tropical diseases (NTDs) being highly cost-e... more Despite many current interventions against neglected tropical diseases (NTDs) being highly cost-effective, new strategies are needed to reach the WHO's control and elimination goals. Here we argue for the importance of incorporating economic evaluations of new strategies in decisions regarding resource allocation. Such evaluation should ideally be conducted using dynamic transmission models that capture inherent nonlinearities in transmission and the indirect benefits ('herd effects') of interventions. A systematic review of mathematical models that have been used for economic analysis of interventions against the ten NTDs covered by the London Declaration reveals that only 16 out of 49 studies used dynamic transmission models, highlighting a fundamental--but addressable--gap in the evaluation of interventions against NTDs.
Mathematical modelling of helminth infections has the potential to inform policy and guide resear... more Mathematical modelling of helminth infections has the potential to inform policy and guide research for the control and elimination of human helminthiases. However, this potential, unlike in other parasitic and infectious diseases, has yet to be realised. To place contemporary efforts in a historical context, a summary of the development of mathematical models for helminthiases is presented. These efforts are
Transactions of the Royal Society of Tropical Medicine and Hygiene, 2009
As part of a 4-year control programme beginning in 2003 and entitled Piga Vita Kichocho, around 1... more As part of a 4-year control programme beginning in 2003 and entitled Piga Vita Kichocho, around 140,000 school-aged children on Unguja Island, Zanzibar were treated annually with a combination of praziquantel and albendazole. To provide information on the impact of this intervention, a subset of children, originating from 24 sentinel schools, were monitored in 2004, 2005 and 2006 using both parasitological and behavioural questionnaire methods. Overall, prevalence of urinary schistosomiasis fell by 52%, intensity by 55% and gross haematuria by 82%. There was a positive and statistically significant correlation between areas of elevated disease prevalence and areas of predicted high transmission based upon local occurrence of the permissive intermediate snail host. In areas of low transmission, urinary schistosomiasis was greatly reduced, but, by contrast, other intervention strategies are needed to complement and synergise with chemotherapy in high transmission areas. Whereas significant reductions were documented in the prevalence of both Trichuris trichiura and hookworm, prevalence of Ascaris lumbricoides significantly increased over the monitoring period. Through a detailed analysis of named child records, evidence of predisposition to helminth (re)infection and individual bias towards polyparasitism was detected, highlighting the often overlapping distribution of these parasites within the school-aged child.
To evaluate micro-haematuria, detected by Haemastix reagent strips, for diagnosis of urinary schi... more To evaluate micro-haematuria, detected by Haemastix reagent strips, for diagnosis of urinary schistosomiasis during a 3-year period of school-based control on Zanzibar. A sub-set of school children, from a total of 135,000 who were receiving treatment for urinary schistosomiasis and soil-transmitted helminthiasis, were monitored by parasitological and questionnaire methods for Schistosoma haematobium infections: at treatment baseline in 2004 (n=2002), follow up with re-treatment in 2005 (n=3278) and further follow up with re-treatment in 2006 (n=3993). Standard diagnostic scores for micro-haematuria were calculated against parasitological assessment. Diagnostic scores of Haemastix remained strong throughout the 3-year period. In 2006, scores were: sensitivity (SS)=0.86 (95% CI: 0.86-0.88), specificity (SP)=0.99 (0.98-1.00), positive predictive value (PPV)=0.90 (0.88-0.91), negative predictive value (NPV)=0.98 (0.98-0.99) in boys; and SS=0.84 (0.82-0.86), SP=0.98 (0.98-0.99), PPV=0.77 (0.75-0.79) and NPV=0.99 (0.99-1.00) in girls. By comparison, reported blood in urine and pain upon urination were much lower and not as informative. At a cost of approximately pound sterling 0.20/test, further use of reagent strips for monitoring of urinary schistosomiasis during ongoing control programmes should be advocated as a rapid, cost-effective and informative disease surveillance tool.
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