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1From the Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, and the 3International Chlamydia Laboratory, Adult Infectious Diseases, Johns Hopkins University, Baltimore, Maryland; and the 2Kongwa Trachoma Project, Kongwa, Tanzania.
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METHODS. Maindi village in Tanzania received a first round of mass treatment with azithromycin after a baseline survey for trachoma and infection. All residents aged 6 months and older were offered single-dose treatment with azithromycin (excluding pregnant women with no clinical trachoma, who were offered topical tetracycline). The residents were followed over an 18-month period, and, according to similar treatment criteria, were offered retreatment at 18 months. Five years after baseline (3.5 years after the second round of mass treatment), a new census and survey of current residents for trachoma and infection was conducted. Children are the sentinel markers of infection and trachoma in communities, so data are presented specifically for ages 0 to 7 years (preschool age) and 8 to 16 years.
RESULTS. Treatment coverage was above 80% for all ages in the first round, and highest (90%) in preschool-aged children. Second-round coverage was lower, <70%, and 70% in preschool-aged children. At 5 years, trachoma rates were still lower than baseline, ranging from 45% in those aged 0 to 3 years to 8% in those aged 11 to 15 years (compared with 81% and 39% at baseline, respectively). Infection rates at baseline ranged from 71% to 57%, but were 27% to 17% at 5 years after two rounds of mass treatment. At 5 years, there were no differences in trachoma or infection rates, when comparing new residents who came after the second mass treatment with those who had been resident in the village during both rounds (P > 0.05). Infection rates were lower in those who had been treated twice or at 18 months than in those treated only at baseline or never treated.
CONCLUSIONS. Although mass treatment appears to be associated with lower disease and infection rates in the long term, trachoma and C. trachomatis infection were not eliminated in this trachoma hyperendemic village 3.5 years after two rounds of mass treatment. Continued implementation of the SAFE strategy in this environment is needed.
Studies of community-based mass treatment with a single dose of azithromycin suggest that one round with high coverage is effective in lowering infection rates.2 3 4 5 6 7 A study in small villages from a trachoma-hypoendemic area in the Gambia suggested that a single round of mass treatment would be sufficient for the virtual elimination of infection, unless the infection was introduced from outside exposure.4 In a mesoendemic village in Tanzania, a single round of mass treatment plus provision of tetracycline ointment to active cases at 6, 12, and 18 months eliminated infection.3 However, in a hyperendemic community in Tanzania (which is the subject of these analyses), a single round of mass treatment reduced infection rates but did not eliminate infection and there was evidence of re-emergence at 18 months.6 Similarly, in a study of twice-yearly targeted treatments (only school children with disease and their families were treated) with poor infection coverage in Vietnam, infection and clinical trachoma appeared to decline; but once no more antibiotic was provided, there was some evidence of re-emergence.8 In hyperendemic villages in Ethiopia, a single round of mass treatment was effective in reducing infection in eight villages, with an average coverage of more than 90% (individual village’s coverage was not provided) with evidence for return of infection by 24 months in seven of the eight villages.9 In a study in Nepal where more than 30% of children had active trachoma, three rounds of treatment directed at children age 1 to 10 years were successful in reducing infection and disease in these children up to 6 months after the last treatment.10 However, it is not clear whether 6 months is long enough to determine whether infection and disease would re-emerge.
A WHO working group on trachoma control recommended three rounds of yearly mass treatment in communities where the trachoma rate in children age 0 to 10 is greater than 10%.7 However, there are few published data on the effect of more than one round of mass treatment on infection or clinical trachoma. The purpose of this study was to determine, after two rounds of mass treatment with azithromycin spaced 18 months apart, the rate of trachoma and infection at 5 years after baseline in Maindi. The population of this village was studied at 6, 12, and 18 months after one round of mass treatment and was shown to have a decline in infection, but at 18 months, infection and infection load was starting to increase with evidence of spreading across households.5 6 At 18 months, mass treatment was again provided to the village, and the purpose of this study is to evaluate infection and clinical trachoma at 3.5 years after two rounds of mass treatment.
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No further treatment with antibiotic for trachoma was provided to the community once the previous study had ended. The Tanzania National Trachoma Control Program uses infrequent radio spots to broadcast messages about face washing and latrine construction, but no specific health education programs within Maindi were provided. At the final 18-month examination, our survey team reminded mothers of the importance of face washing to reduce trachoma. No additional water sources for the community were built in the interim between the last survey and the present study.
In 2005, the village underwent an additional census by our trained team to determine the current status of previous residents and to add persons who had moved into the village or were born since the time of the last census update 3.5 years previously. Transient visitors, defined as those who had not lived in the village for at least 1 month and who did not plan to stay for another 6 months, were not added.
After the census, a trachoma survey was conducted in May to July, targeting everyone in the current census aged 6 months and older. An experienced trachoma grader (HK) with 2.5x loupes assessed the presence of clinical trachoma using the WHO simplified grading system for presence and absence of follicular trachoma (TF) and intense trachoma (TI).12 Active trachoma is defined as anyone with either of those signs. Photographs were taken of the left eye and graded for trachoma. The comparison of photogrades and clinical grades showed high agreement (
> 0.65 for both signs). A Dacron swab was rubbed across the upper left conjunctiva and placed in a sterile, dry, vial and frozen to be analyzed for C. trachomatis. Careful techniques were used in the field to avoid contamination. At the laboratory station in the field, only the laboratory supervisor was allowed to open the vial and open the swab. He was the only one to touch the swab and take the specimen. He wore gloves that were changed between subjects, but he did not touch anyone during the entire session, not even the subject. The person who flipped lids changed gloves between persons. Once new gloves were on, he was not permitted to touch anything other than the subject’s upper eye lid. If there was inadvertent touching of surfaces or other subjects by either person, the gloves were removed and new gloves put on.
The swabs were stored in a –20° freezer until they were shipped to the International Chlamydia laboratory at Johns Hopkins for processing.
A C. trachomatis qualitative PCR assay (Amplicor; Roche Molecular Systems, Indianapolis, IN) was used to identify samples positive for organism DNA. In essence, PCR was performed on eluted samples according to the manufacturer’s instructions. Testing for PCR inhibition was also performed according to the manufacturer’s directions. If there was evidence of inhibition, samples were retested by diluting 1:5 with a 50:50 mixture of lysis buffer (Amplicor CT/NG; Roche Molecular Systems) and specimen diluent. A positive test was defined, as per the manufacturer, as an optical density >0.7. Equivocal samples were those in which the optical density was between 0.2 and 0.7 in two replicates.
For the purposes of this study, we show data from children aged less than 15 years, because there was very little trachoma or infection in persons aged 16 and older at either the 18-month time point (trachoma rate of 10% and infection rate of 5%) or the 5-year follow-up (3% and 9%). We concentrated on children as the sentinel markers of disease and infection in communities, similar to other studies and to WHO Guidelines for Ultimate Intervention Goals. However, we show antibiotic coverage data for the entire community, consistent with national treatment reporting guidelines. The data analyses considered both the treatment and an age effect. That is, the residents of the village at baseline who were exposed to both rounds of treatment were all 5 years older by the time of this follow-up, and it is particularly children 3 years of age and younger who have high rates of trachoma and infection.6 Thus, it was important to compare children by age groups at the time of the various surveys, for proper interpretation. At each survey time—baseline, 18 months, and 5 years—there are different denominators, depending on the changing census. For this reason, we did not try to compare the same people over time, but rather compared the cross-sectional prevalences in the relevant groups, testing significance by using probabilities adjusted for age, gender, and clustering within children in the same household.
The research adhered to the tenets of the Declaration of Helsinki. All procedures received ethics approval by the Tanzania National Institute for Medical Research and the Institutional Review Board of Johns Hopkins University. Pfizer International had no role in the study design, protocols, data collection, or data analyses or in the preparation of this report.
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We expected, compared to residents, that new arrivals to the village after the last round of mass treatment would have higher rates of infection and disease as they did not have the benefit of previous treatment. However, new arrivals did not have disease or infection rates that were significantly different from those who had been in the village. Possible explanations for this finding include the following: First, we do not have data on the actual arrival dates of the new persons, except the births. Those "new" to the village may have in fact been there for, on average, 2.5 years since baseline. Thus, it is not unexpected that the trachoma and infection rates in this group would equilibrate to those persons already in the village. We have previously demonstrated that spread of infection across households occurs within 12 months.11 This explanation is supported by the finding at 5 years that the 0- to 3-year-olds, who were born into the village after the last treatment, were not protected from incident infection but rather have rates of disease and infection similar to the 4- to 7-year-olds with whom they doubtlessly mingle. Second, we do not know from which villages the new arrivals came—whether it was from other program villages—the new arrivals may have had equally low or lower rates of infection and trachoma when they arrived, comparable to those in the village. Finally, the village had high rates of in and out migration, and we have shown that those who left the village after the 18-month survey were less likely to have trachoma and infection compared with those who stayed. Thus, if there had been less migration, the rates in the village residents may have been lower than were observed at the 5-year survey. However, migration is a factor that national trachoma control programs will have to contend with in planning coverage of villages and districts.
We feel our findings of sustained low rates of infection likely reflect the antibiotic mass treatment coverage. As we have reported previously, the first round of mass treatment had very high antibiotic coverage, which resulted in a dramatic drop in infection, but did not eliminate either trachoma or infection by 18 months.6 In hyperendemic villages, there will be persons with very high loads for whom a single dose may be insufficient to clear infection. We previously reported re-emergent infection within families by 6 months, from family members who had not cleared infection despite treatment.6 The second round of mass treatment had much lower coverage, although more than 70% of the highest risk group, preschool-age children, was treated. These coverage rates are lower than ideal, but may be more typical of what programs providing multiple rounds of mass treatment are able to achieve. We can speculate that if coverage of the second round had been especially high, the rates observed at 5 years may have even been lower. Solomon et al.,3 in another village with lower rates of trachoma and infection at baseline, achieved virtual elimination of infection 2 years after mass treatment, with very high coverage rates (98%) plus interim (2, 6, 12, and 18 months) treatment of trachoma cases with antibiotic ointment. Even though our coverage for the second round was less than the 80% target, at 3.5 years after treatment, the infection and trachoma rates were not back to pretreatment levels, suggesting a long-term benefit of two rounds of mass treatment even at <80% in the second round.
However, to reach the Ultimate Intervention Goal of WHO of trachoma in less than 10% of children younger than 10 years and to be certain the low rate of infection will be sustainable, more must be done. Attaining the goal may require more than two rounds of mass treatment, probably spaced closer together, as projected by a model of infection elimination,14 and more improvements in the environment and hygiene, as recommended by the WHO SAFE strategy approach.
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Acknowledgements |
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Footnotes |
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Submitted for publication June 8, 2006; revised November 10 and December 8, 2006; accepted February 20, 2007.
Disclosure: S.K. West, None; B. Munoz, None; H. Mkocha, None; C. Gaydos, None; T. Quinn, None
The publication costs of this article were defrayed in part by page charge payment. This article must therefore be marked "advertisement" in accordance with 18 U.S.C. 
1734 solely to indicate this fact.
Corresponding author: Sheila K. West, Wilmer Room 129, Wilmer Eye Institute, Johns Hopkins Hospital, 600 N. Wolfe Street, Baltimore, MD, 21205; shwest{at}jhmi.edu.
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