Despite some notable successes in the control of infectious diseases, transmissible pathogens still pose an enormous threat to human and animal health. The ecological and evolutionary dynamics of infections play out on a wide range of interconnected temporal, organizational and spatial scales, which even within a single pathogen often span hours to months, cellular to ecosystem levels, and local to pandemic spread. Some pathogens are directly transmitted between individuals of a single species, while others circulate among multiple hosts, need arthropod vectors, or can survive in environmental reservoirs. Many factors, including increasing antimicrobial resistance, increased human connectivity, and dynamic human behavior, raise prevention and control from formerly national to international issues. In the face of this complexity, mathematical models offer essential tools for synthesizing information to understand epidemiological patterns, and for developing the quantitative evidence base for decision-making in global health.

No abstract

Article:Quinnell, R.J., Courtenay, O., Garcez, L.M. et al.(1 more author) (1997) The epidemiology of canine leishmaniasis: transmission rates estimated from a cohort study in Amazonian Brazil. Parasitology, 115 (02 (Received 13 June 1996 ; revised 4 February 1997 ; accepted 7 February 1997 ) We estimate the incidence rate, serological conversion rate and basic case reproduction number (R ! )ofLeishmania infantum from a cohort study of 126 domestic dogs exposed to natural infection rates over 2 years on Marajo! Island, Para! State, Brazil. The analysis includes new methods for (1) determining the number of seropositives in cross-sectional serological data, (2) identifying seroconversions in longitudinal studies, based on both the number of antibody units and their rate of change through time, (3) estimating incidence and serological pre-patent periods and (4) calculating R ! for a potentially fatal, vector-borne disease under seasonal transmission. Longitudinal and cross-sectional serological (ELISA) analyses gave similar estimates of the proportion of dogs positive. However, longitudinal analysis allowed the calculation of prepatent periods, and hence the more accurate estimation of incidence : an infection-conversion model fitted by maximum likelihood to serological data yielded seasonally varying per capita incidence rates with a mean of 8n66i10 −$ \day (mean time to infection 115 days, 95 % .. 107-126 days), and a median pre-patent period of 94 (95 % .. 82-111) days. These results were used in conjunction with theory and dog demographic data to estimate the basic reproduction number, R ! , as 5n9 (95 % ..4 n 4-7n4). R ! is a determinant of the scale of the leishmaniasis control problem, and we comment on the options for control.

No abstract