We found that children aged 0–5 years who present earlier for examination and testing prior to treatment for trachoma have higher odds of ocular Chlamydia
than those who present later, in 4 villages in trachoma-endemic Niger. The odds of ocular Chlamydia
dropped with each successive quartile of presentation. Researchers and program managers have been concerned that children in more disadvantaged families are more likely to harbor ocular Chlamydia
and less likely to be brought earlier for examination. Here, we found the opposite—children with ocular Chlamydia
are more likely to be brought earlier. Even if the WHO 80% treatment coverage goals are not reached in certain settings, the children who form the known reservoir of infection have higher odds of receiving attention because they are the first to present. There are several potential reasons to explain why early presenters have higher odds of harboring active trachoma and ocular Chlamydia
than late presenters. Although active trachoma is believed to be a relatively mild or asymptomatic condition, parents and guardians may identify factors in their children such as intermittent ocular discharge or conjunctivitis which make them more likely to be brought for attention 
. Active trachoma is spread within families and schools and can be exacerbated by overcrowding 
. It is reasonable to assume that children who are more social are more likely to be brought early for examination in a group setting where examinations are performed in Niger.
The extra effort required to locate individuals who are absent for examination may not be as important as had previously been thought. It may be practical to forgo pursuing difficult to reach children because the critical ‘core or herd’ group is present in the earlier quartiles, and coverage of infected persons is achieved prior to achieving coverage of the overall population.
Mathematical models and empirical studies suggest that disease elimination can be achieved even without treating all infected individuals in a community over time 
. If a core group of infected individuals are repeatedly treated, then a degree of herd protection can be offered even to those who have not received treatment. Models assume that those untreated are no more likely to be infected than those treated. Here we find that those last to be examined are not more
likely to be infected— they're less
likely to be infected.
Although this study does not include data about expenses, it suggests an alteration of the cost-benefit equation in that the benefit of pursuing the final quartile of ‘hard-to-reach’ children has diminished value because it contains fewer infected children. Delivery of mass antibiotic treatment is expensive, especially in areas that are hard to reach 
. Even if oral azithromycin is donated, the extra effort required to locate absent individuals may be considerable. Our report supports results from an Ethiopian study that showed children examined on subsequent days after the initial monitoring day were less likely to have ocular Chlamydia
than children seen on the initial day in an area hyperendemic for trachoma 
. Antibiotic coverage is an important short-term predictor of ocular Chlamydia
but may not be as important by six months after treatment, calling into question the necessity of achieving high coverage at all costs 
This study has some limitations. First, only 4 villages were included in the analysis of infection, and these villages may not be representative of the larger population in Niger or other trachoma-endemic countries. However, we found similar results in the 4 villages for rank order and infection as we did in the 48 villages for rank order and clinical disease. Second, only children aged 0–5 years were included, and there are children older than 5 years or adults in the communities who harbor infection. However, young children are known to be the most important reservoir of ocular Chlamydia
in communities so exclusion of older children is unlikely to affect our estimates 
. Third, this study was performed in a research setting which may not be generalizable to trachoma treatment programs that do not have the same resources. Finally, this was a study of the association of order of presentation with active trachoma and ocular Chlamydia
PCR, not antibiotic treatment coverage. It is not unreasonable to assume that children who present earlier for examination are more likely to present earlier for treatment, but this was not measured in this study.
In summary, we found that children 0–5 years who have ocular Chlamydia have higher odds of presenting early for ocular examination than children who do not have ocular Chlamydia in Niger where trachoma is endemic. The added effort required to reach the last infected individuals in a community may provide diminishing returns. We suggest thoughtful use of limited health-care resources in trachoma programs, perhaps to reach more villages, rather than excessive efforts to attain high coverage in individual villages. Efficient use of limited resources is critical for the WHO to achieve their trachoma elimination goals by the year 2020.