Chapter Category: Parasitic Disease

From the book Modelling Parasite Transmission and Control

Vector Transmission Heterogeneity and the Population Dynamics and Control of Lymphatic Filariasis

Edwin Michael and Manoj Gambhir

A long-standing gap in lymphatic filariasis epidemiology is quantifying the potential effect that heterogeneous infection processes occurring in the major mosquito vector genera may have on parasite transmission and control. Although previous studies have focussed on examining the forms of the density dependent mechanisms regulating larval infection in various mosquito genera, there has been little work done thus far in investigating how such differential processes might interact with density-dependent processes occurring in other stages of the parasite life cycle to influence overall transmission patterns and parasite system dynamics between areas exposed to different transmitting vector populations. Here, we explore the impact that differences in vector genus-related larval infection dynamics may have on filariasis transmission and control using newly derived parasite transmission models incorporating the forms of the density-dependent processes regulating larval infection in the two major vectors transmitting filariasis, viz. culicine and anopheline mosquitoes. The key finding in this work is that filarial infection thresholds, system resilience, transmission dynamics and parasite response to control efforts, can all be influenced by the prevailing transmitting mosquito genus. In particular, we show that infection thresholds may be raised, system resilience to perturbations lowered and effects of repeated mass treatments in eliminating infection enhanced in anopheline filariasis compared to culicine filariasis, as a direct result of the occurrence and action of multiple positive density-dependent mechanisms influencing infection in this vector-parasite system, such as the \"facilitation\" function regulating larval infection dynamics in the vector and the inverse probability function governing adult worm mating in the host. These findings indicate that anopheline filariasis may be easier to eradicate than culicine filariasis for a given precontrol infection level, although the actual intensity of interventions required to achieve eradication may in fact be similar to that for culicine filariasis because of the higher infection levels generated as a result of the \"facilitation\" process in Anopheles transmission areas.

Taken from the book

Modelling Parasite Transmission and Control

Edited by: Edwin Michael and Robert C. Spear

More chapters from the book:

Mathematical Modeling of the Epidemiology of Tuberculosis
Peter J. White and Geoff P. Garnett

Despite the infectious agent that causes tuberculosis having been discovered in 1882, many aspects of the natural history and transmission dynamics of TB are still not fully understood. This is reflected in differences in the structures of mathematical models of TB, which in turn produce...


Progress in Modelling Malaria Transmission
David Smith and Nick Ruktanonchai

Ronald Ross demonstrated that mosquitoes transmit malaria parasites. In the years that followed, malaria control programs focused on reducing mosquito densities, largely through larval vector control. Eleven years after Ross\'s seminal discovery, he wrote about malaria transmission in Report on...


Macroparasites of humans are sensitive to a variety of environmental variables, including temperature, rainfall and hydrology, yet current comprehension of these relationships is limited. Given the incomplete mechanistic understanding of environment‑disease interactions, mathematical models...


Human monocytic ehrlichiosis (Ehrlichia chaffeensis), or HME, is a tick‑transmitted, ricksettisal disease with growing impact in the United States. Risk of a tick‑borne disease such as HME to humans can be estimated using the prevalence of that disease in the tick population. A deterministic...


Mathematical models of malaria transmission have been used to inform the design of malaria control programs since the mid 20th century, and many of these models have provided useful insights into the complexity of the disease. Among developing countries, however and particularly in sub‑Saharan...


Some models are presented for the dynamics of a host population with two parasite species. The models differ in two main aspects: whether they include direct competition among parasites and whether the analysis is based on some approximation and which one. If the analysis is not constrained by a...


The purpose of infectious disease transmission modeling is often to understand the factors that are responsible for the persistence of transmission, the dynamics of the infection process and how best to control transmission. As such, there should be great potential to use mathematical models to...


The use of mathematical models for developing management options for controlling infectious diseases at a local scale requires that the structure and parameters of the model reflect the realities of transmission at that scale. Data available to inform local models are generally sparse and come...


A long-standing gap in lymphatic filariasis epidemiology is quantifying the potential effect that heterogeneous infection processes occurring in the major mosquito vector genera may have on parasite transmission and control. Although previous studies have focussed on examining the forms of the...


The number of helminths within a host can only increase by the host encountering additional infectious stages, so it is important to consider not only whether a host is infected, but also the severity of its infection. Stochastic models consider explicitly the number of parasites within the host...


Modelling Trachoma for Control Programmes
Manoj Gambhir, María-Gloria Basáñez, Isobel M. Blake and Nicholas C. Grassly

Trachoma is a major cause of blindness in the developing world and 63 million people are currently infected. Large‑scale control programmes are being implemented to clear ocular Chlamydia trachomatis infection—the causative agent of trachoma—and improve environmental conditions to reduce...


Modelling Climate Change and Malaria Transmission
Paul E. Parham and Edwin Michael

The impact of climate change on human health has received increasing attention in recent years, with potential impacts due to vector‑borne diseases only now beginning to be understood. As the most severe vector‑borne disease, with one million deaths globally in 2006, malaria is thought most...


The planning and evaluation of parasitic control programmes are complicated by the many interacting population dynamic and programmatic factors that determine infection trends under different control options. A key need is quantification about the status of the parasite system state at any one...


This chapter describes what should be an integrated approach to the genetic epidemiology and population genomics of Chagas disease. Many studies have been conducted on the genetic diversity of Trypanosoma cruzi and the various triatomine bug species able to transmit Chagas disease. Far less...


Advertisements