Laboratory Tests in the Fight to Save Sight

Trachoma, a disease of the eye caused by a bacteria called Chlamydia trachomatis, is the leading infectious cause of blindness worldwide. Repeated infections cause the eyelid to turn inward, at which point the eyelashes scrape and permanently scar the cornea. At one time, trachoma was endemic in parts of Europe and the United States. Trachoma exams—flipping the eyelids and looking for the characteristics spots (or follicles) —were conducted on European immigrants passing through Ellis Island and other facilities in the early 20^th century. With development came improved sanitation, leading to the disappearance of the disease in the United States and Europe in the mid-20^th century.

Still, today, 540 million people are at risk in 55 countries, and 84 million people are already infected.

In 1997 the Global Elimination of Trachoma by 2020—GET2020—was established. Successes toward the elimination of trachoma achieved thus far can be credited to proven strategies like surgery to correct advanced disease and antibiotics donated by Pfizer to treat active infection, with over 550 million doses of the donated drug given to date. Facial cleanliness and environmental improvement campaigns are also critical to reduce disease transmission. Knowing where interventions are needed the most has been accomplished through the efforts of the Global Trachoma Mapping Project, the largest disease mapping project ever undertaken. And USAID, now celebrating the 10^th anniversary of work in Neglected Tropical Diseases (NTDs), has been a major funding partner for these programs.

While trachoma elimination is still a few years off, it is time to begin anticipating what is needed to ensure sustained elimination. There’s no doubt that new lab tools will be a key element.

Moving forward it will be critical to develop surveillance systems that identify re-emergence or re-introduction of trachoma into communities. The 2020 target for trachoma elimination is four years off, but sustaining the gains of the trachoma elimination program requires developing the information and laboratory monitoring systems now. It takes time to develop and test the laboratory tools that are needed for monitoring the success of trachoma programs. After that, these tools will need to be tested in the field before public health officials can rely on the data to detect re-emergence of disease transmission. These concerns prove to be a challenge for global health programs when prioritizing resources and in the face of more immediate needs for getting sight-saving treatment to communities.

With the support of USAID investments, scientists in CDC’s Division of Parasitic Diseases and Malaria have turned to the blood as a way to develop tools to determine how much trachoma is in a community. The scientific rationale is that when kids get infected, they should develop an antibody response. And if they get infected again, and again, and again, each of those infections should act as a sort of booster to the previous infection. When there is a lot of trachoma in a community, there should be a lot of kids with a lot of antibody, and when there is little or no trachoma in a community, the kids should have no antibodies.

So far that is exactly what we have found. The proportion of kids with antibodies to the bacteria that causes trachoma decreases as the amount of trachoma in the community decreases. And in communities where trachoma has been eliminated, the percent of kids with antibody responses is virtually zero. This laboratory tool makes it possible to monitor the impact of trachoma elimination programs and identify infections early if trachoma returns.

Using USAID funding, we developed antibody tests for trachoma surveillance at CDC and rapidly transferred the tools for use in endemic countries. CDC staff have since trained laboratory scientists in Ghana, Malawi, and Colombia to use ELISA methods for antibody testing, and we have partnered with these countries to continue testing the tool so that it will be ready for surveillance as countries move toward elimination of trachoma. We have also developed a rapid, hand-held version of the test and recently field-tested it in Nepal. Ethiopia—the country with the heaviest trachoma burden—is set to validate the new handheld test this summer.

The 2020 target for global trachoma elimination is fast approaching. CDC and our partners are committed to providing countries with the right tools to guarantee the continued control and eventual elimination of trachoma and the blindness that it may cause, continuing in our fight to save sight.