Trachoma continues to be the leading cause of infectious blindness. Mass administration of
antibiotics is part of the current control effort, an approach which is costly when drugs are
not donated.
Trachoma has been shown to cluster by household and therefore this unit could be a means
to target treatment. This thesis shows that active inflammatory disease is a more sensitive
marker of infection within an individual’s household than just in that individual. The
potential impact of a more efficient, targeted treatment of households with at least one
member with active disease depends on the relative contributions of community and
household transmission of infection.
A mathematical model of the household transmission of ocular Chlamydia trachomatis was
fitted to detailed demographic and prevalence data from four endemic populations, two in
The Gambia and two in Tanzania. Maximum likelihood estimates of the household and
community transmission coefficients were obtained. The estimated household transmission
coefficient exceeded both the community transmission coefficient and the rate of clearance
of infection by individuals in three of the study populations, indicating persistent
transmission of infection within households. Allowing children and adults to have a different
duration of infection improved the fit of the model to the data in three populations.
For a given level of treatment coverage, targeting antibiotics to households with active
disease was predicted to have similar post‐treatment dynamics to those observed after
mass treatment but to be much more drug sparing. Using available cost data this approach
was shown to be more cost effective when antibiotics are not donated. If targeting
increases treatment coverage of diseased households, it was found to be more effective and
more cost‐effective than mass treatment even if antibiotics are donated. Further work is
now required to explore the feasibility of incorporating household targeted treatment into
trachoma control programmes.