New Collection of Publications

In October 2015, members of the NTD Modelling Consortium published a collection of papers in Parasites and Vectors. This collection contains novel analyses on the dynamics of nine NTDs, ranging from model comparisons to new estimates of key parameters. 

Preventive chemotherapy diseases

Preventive chemotherapy and transmission control (PCT) is the main strategy for control of onchocerciasis, lymphatic filariasis, schistosomiasis, soil-transmitted helminthiasis and trachoma. The strategy involves regular provision of preventive treatment (in the form of mass drug administration (MDA) campaigns) to entire populations or targeted risk groups (e.g. schoolchildren). This strategy reduces disease progression in treated individuals and prevents transmission of infection to others. Mass drug administration (MDA) programmes are rapidly expanding, although important questions remain. For example, will the planned MDA programmes be sufficient to achieve elimination in all epidemiological settings? To what extent is successful elimination jeopardized by low coverage and systematic non-adherence? When, and on the basis of what criteria can MDA be safely interrupted?  Each of the modelling analyses highlight the importance of groups who systematically, or semi-systematically do not access MDA programs in sustaining transmission. This potential for undermining program success is particularly acute if groups of the population who are most at risk through their behaviours (e.g. those who most frequently go to the river) are also those who are most difficult to access through an MDA campaign. The results support previous analyses that increased coverage, across different age groups, or through general coverage, may be more important than frequency of treatment. 

Publications

Required duration of mass ivermectin treatment for onchocerciasis elimination in Africa: a comparative modelling analysis

Modelling strategies to break transmission of lymphatic filariasis - aggregation, adherence and vector competence greatly alter elimination

Bayesian calibration of simulation models for supporting management of the elimination of the macroparasitic disease, Lymphatic Filariasis

Mathematical modelling of lymphatic filariasis elimination programs in India: required duration of mass drug administration and post-treatment level of infection indicators

Modelling control of Schistosoma haematobium infection: predictions of the long-term impact of mass drug administration in Africa

What is required in terms of mass drug administration to interrupt the transmission of schistosome parasites in regions of endemic infection?

What impact will the achievement of the current World Health Organisation targets for anthelmintic treatment coverage in children have on the intensity of soil transmitted helminth infections?

Feasibility of controlling hookworm infection through preventive chemotherapy: a simulation study using the individual-based WORMSIM modelling framework

Possible changes in the transmissibility of trachoma following MDA and transmission reduction: implications for the GET2020 goals

Short-term forecasting of the prevalence of clinical trachoma: utility of including delayed recovery and tests for infection

 

Intensified disease management diseases 

A number of neglected tropical diseases are controlled by increased diagnosis and management of cases (intensified disease management, IDM). The four IDM diseases in this study are Chagas disease, the Gambian form of human African trypanosomiasis, leprosy globally and visceral leishmaniasis on the Indian sub-continent. Whilst these diseases cause significant morbidity and mortality, the disease courses are quite long, the epidemic growth rate is slow and the transmission is usually highly focal. They are often associated with disadvantaged populations and hard-to-reach groups. Given this concentration of disease in populations with poor access to care, and the potentially long time periods over which their disease course and dynamics occur, these diseases have been difficult to study and so quantitative estimates of key parameters are scarce. In the model analyses of these diseases the authors have aimed to provide novel estimates of key parameters and provide both qualitative and quantitative insights on the dynamics of these infections and their consequences for control.

Publications

Broad patterns in domestic vector-borne Trypanosoma cruzi transmission dynamics: synanthropic animals and vector control

Evaluating long-term effectiveness of sleeping sickness control measures in Guinea

Quantitative evaluation of the strategy to eliminate human African trypanosomiasis in the Democratic Republic of Congo

Global elimination of leprosy by 2020: are we on track?

Spatial heterogeneity in projected leprosy trends in India

Back-calculating the incidence of infection of leprosy in a Bayesian framework

Quantification of the natural history of visceral leishmaniasis and consequences for control

Feasibility of eliminating visceral leishmaniasis from the Indian subcontinent: explorations with a set of deterministic age-structured transmission models