Possible changes in the transmissibility of trachoma following MDA and transmission reduction: implications for the GET2020 goals.
BACKGROUND
The role of mass drug administration (MDA) and the implementation of transmission reduction measures are essential to successfully control and eliminate a wide range of NTDs, including the ocular disease trachoma. Immunity to trachoma infection acts by reducing the duration of an individual's infectious period and by reducing their infectivity with each successive infection.


METHODS
In this study, we use a model of trachoma infection, which includes population immunity, to explore the impact of treatment and transmission reduction measures on trachoma prevalence. Specifically, we investigate the possibility of increasing transmissibility of trachoma arising as MDA and transmission reduction measures are scaled up in endemic settings.


RESULTS
We demonstrate this increase in transmissibility by calculating the effective reproduction number during several simulated control programmes and show that it is related to a decrease in the level of immunity in the population.


CONCLUSIONS
This effect should be studied in the field by measuring the rate of return of infection and disease in at least two separate age groups. If the decline of population immunity is operating, it should be accounted for when planning for the GET2020 goal of eliminating blinding trachoma by 2020.
Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia. manoj.gambhir@monash.edu.
Manoj
M
Gambhir
Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.
Amy
A
Pinsent
D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002692:Chlamydia trachomatis / Q000187:drug effects / Q000502:physiology; D006040:Goals; D006801:Humans; D008962:Models, Theoretical; D014141:Trachoma / Q000188:drug therapy* / Q000382:microbiology / Q000517:prevention & control / Q000635:transmission*
D000900:Anti-Bacterial Agents