Trachoma Eradication – A failed target by 2020

Trachoma is considered the leading cause of blindness, endemic in most of the countries as a tropical disease and ranked second to cataract. Sporadic cases are still seen in our country especially in patients coming from remote areas where health services and civic amenities are either meager or not available. In fact, the disease thrives in them through contact with hands, clothes, infected flies or bedding of infected persons. About 84 million people worldwide suffer from C. trachomatis eye infection and 8 million are blind. It is a primary source of blindness (19%) in some parts of rural Africa and some Asian countries as a neglected tropical disease i.e., inclusion conjunctivitis. WHO initiated a program in 1990 to control the disease by 2020.

Trachoma is considered the leading cause of blindness, endemic in most of the countries as a tropical disease and ranked second to cataract. Sporadic cases are still seen in our country especially in patients coming from remote areas where health services and civic amenities are either meager or not available. In fact, the disease thrives in them through contact with hands, clothes, infected flies or bedding of infected persons. About 84 million people worldwide suffer from C. trachomatis eye infection and 8 million are blind. It is a primary source of blindness (19%) in some parts of rural Africa and some Asian countries as a neglected tropical disease i.e., inclusion conjunctivitis. WHO initiated a program in 1990 to control the disease by 2020. Globally speaking, there are 44 countries which account trachoma as a public health problem and 142 million people are at risk of going blind while 1.9 million people are either blind or visually handicapped. Why not more enthusiasm for trachoma eradication? Why its eradication is impossible? While infection has already been eliminated in some countries. Some argue that the eradication is not possible due to a low level of infection, which never causes enough scarring leading to blindness. It may well be true. However, if enthusiasm for another decade of the program wanes, it could result in resurgence of infection. Global eradication of Chlamydia trachomatous can be achieved if health authorities intensify their collective efforts in the most affected areas. It is hard to blame WHO as failures to reach overly ambitious goals like Malaria and Leprosy. Smallpox remains the only infectious disease eradicated so far. C. trachomatis is thought to have diverged from 6 million years ago and was first described in 1907 by Stanislaus von Prowazek named it “Chlamydozoa” (in Greek), thought to be a virus. However, in 1966 electron microscopy studies showed C. trachomatis to be a bacteria, as it was found to possess DNA, RNA, and Ribosomes like other bacteria and classified as gram-negative. It was first cultured and isolated in the yolk eggs by Tang Fei-fan et al. in 1957. This was a significant milestone for future genomic and phylogenetic studies.

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In summary, The cornerstone of the WHO
program is the mass treatment with a single-dose
of oral Azithromycin. Tetracycline is also the
most preferred antibiotic to treat C. trachomatis
and has the highest success rate.

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To recapitulate briefly, its life cycle consists of two morphologically distinct stages i.e., elementary bodies and reticulate bodies. The organism can replicate only within a host cells. Elementary bodies are small spore-like form 200 to 400 nanometers, surrounded by a rigid cell wall that allows them to survive outside of a host cell. Reticulate bodies are 600 to 1500 nanometers and are found only within host cells. The reticulate bodies modify as inclusion bodies for rapid replication in 30 to 72 hours before causing the cell to rupture and being released into the environment. These new elementary bodies may shed in the semen or epithelial cells of the female genital tract attacking to new host cells. Risk factors for genitor-urinary infections are unprotected sex and living in areas with limited health facilities. Pulmonary infections can occur in infants born to women with active chlamydia infections. Recent research has found that a pair of disulfide bond proteins, which are necessary for C. trachomatis to be able to infect host cells, is very similar to a homologous pair of proteins found in Escherichia coli (E. coli), though the reaction is slower in C. trachomatis. There have been over 220 Chlamydia vaccine trials yet difficult to achieve results from human species. Future trials are being undertaken with closer related species to the human, but it appears to be very difficult to create a fully effective or even partially effective vaccine since the host’s response to infection involves complex immunological pathways. Laboratory tests are: Nucleic acid hybridization tests (DNA probe test) which is very accurate, but is not as sensitive as NAATs. Enzymelinked immuno-sorbent assay (ELISA, EIA) finds substances (Chlamydia antigens) that trigger the immune system to fight Chlamydia infection. Chlamydia Elementary body (EB)-ELISA could be used to stratify different stages of infection based upon Immunoglobulin-γ status of the infected individuals. Direct fluorescent antibody test also finds Chlamydia antigens. Most trachoma programs follow strategy to bring infection to a lowest level. However, it has several characteristics that make eradication feasible due to its zoonotic transmission affecting pelvic inflammatory and respiratory infection. Humans are the only host and the antibiotics like Azithromycin is most effective against Chlamydia as its resistance has not yet emerged. Trachoma has disappeared in many regions without specific trachoma programs and active intervention. In summary, The cornerstone of the WHO program is the mass treatment with a single-dose of oral Azithromycin. Tetracycline is also the most preferred antibiotic to treat C. trachomatis and has the highest success rate. Azithromycin and doxycycline have equal efficacy to treat C. trachomatis with 97 and 98% success. Azithromycin is dosed as 1 gram tablet taken by mouth as a single dose, doxycycline 100 mg twice a day or 200 mg once a day for 7 days. If treatment is necessary during pregnancy, azithromycin, amoxicillin are the recommended medication and is taken as a 1 gram tablet by mouth as a single dose. Tetracycline is not used because it causes harm to the mother and the fetus. Antibiotic resistance is rare in C. trachomatis compared to other infectious bacteria. Mass Drug Administration’s (MDAs) in community-randomized trials confirmed efficacy of mass distribution with a single dose of Azithromycin. They are encouraged about the importance of face washing, hygiene and sanitation. Circumstantial evidence has suggested that hygiene measures are complementary to MDA as seen in endemic countries such as Nepal, Mexico, Ghana, Uganda, and the Gambia in a recently performed population-based surveys. If the infection is not controlled, damage to the fallopian tubes may have already occurred, Biannual distributions may reduce infection more rapidly than annual distributions and have completely eliminated infection from some of the most severely affected communities. It is usually repeated annually for up to five years.

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