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Title: Leptospire dynamics in its reservoir host in a Brazilian slum setting
Author: Minter, Amanda
ISNI:       0000 0004 6059 4410
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2016
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In urban slums, residents often live in close proximity to reservoirs of zoonotic pathogens. Leptospirosis is a zoonosis that humans can contract via contact with animal reservoirs directly or with water contaminated with their urine. The recent population increase in Salvador, a coastal city in North East Brazil, led to the creation of slums, which are overcrowded and lack basic sanitation. The conditions of the slums favour rodent borne transmission of leptospirosis. The Norway rat (Rattus norvegicus) is asymptomatic and can transmit the infection for the entirety of its life. It is the main reservoir host for leptospirosis in Salvador. Motivated by the annual outbreaks of human leptospirosis in Pau da Lima, an urban slum community in Salvador, the within population infection dynamics of the Norway rat were investigated. A mechanistic model of the dynamics of leptospire infection was developed and explored analytically. A global sensitivity analysis of the basic reproduction number to its components was performed. Using newly obtained age-prevalence data from the field, we sought evidence that would indicate which transmission routes actually occur in the wild. By considering the survival from infection, we created risk curves of infection over time and looked for differences in risk for different demographic factors that were a proxy for transmission. There are some model parameters which we were unable to estimate and some which we expected not to vary by system. To confirm that proposed values of demographic parameters were sufficient to describe population dynamics in wild Norway rats we present a Bayesian analysis of a mathematical population dynamics model. These analyses were used to parameterise an age-structured mechanistic model for leptospire infection in the rodent population. Using the age-structured model, optimal control measures were found that would reduce the total (and infected) rat population. Costs of the controls as well as the cost of human infection were included in the analysis. We conclude that vertical and environmental transmission occurs in the wild, and that environmental transmission is the most important route for the maintenance of infection in Norway rats. To control wild Norway rats, combinations of controls are recommended but environmental control should also be investigated to reduce prevalence of infection in rats.
Supervisor: Begon, M. ; Diggle, P. J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral