The leading causes of preventable blindness world-wide are cataracts, glaucoma, trachoma, and onchocerciasis. We do not see the latter two much, if at all, in the United States; they are prevalent primarily in less developed areas, where there are also specific environmental hazards (1).
TRACHOMA
Trachoma is the world’s leading infectious cause of preventable blindness. Eight million world-wide are visually impaired as a result of trachoma (2). It is caused by a bacteria, Chlamydia trachomatis, and typically spreads by contact with an infected person’s hands or clothing, or can be transmitted by flies who have had contact with discharge from an infected person’s nose or eyes. Trachoma is endemic in the poorest, most rural parts of Africa, Asia, the Middle East, South and Central America, and Australia (3), where lack of access to water and sanitation play a role in the disease’s proliferation.
 |
| Trachoma grading card (image: WHO) |
- Surgery to correct trichiasis. As discussed earlier, trichiasis is the precursor to blindness.
- Antibiotics to treat active disease. Single dose azithromycin, donated by Pfizer in the 1990s, is the treatment of choice (5).
- Facial cleanliness and Environmental improvement. While the former two points of the SAFE strategy target treatment of the disease, the latter two focus on prevention. Facial cleanliness reduces disease transmission. Better environmental sanitation and proper waste disposal helps control the fly population (6).
ONCHOCERCIASIS
Onchocerciasis causes inflammation in the eyes (uveitis, keratitis, chorioretinitis, optic neuritis (8)) and the skin (itchy rash, nodules under the skin). The disease’s toll extends into the social and economic realm as well. Once blind, affected individuals have a life expectancy of only one third that of the sighted, and most die within 10 years (9). There is also a social stigma attached to the skin lesions and disfigurement associated with this disease.
 |
|
Sclerosing keratitis in Onchocerciasis (image: CEH Journal)
|
Control: Onchocerciasis elimination strategy involves vector control and/or large scale ivermectin chemotherapy (10).
-
- In terms of vector control, regular aerial spraying of Similium breeding sites for at least 14 years is recommended (until the infection has died out of the human population).
-
- A single dose of ivermectin (Mectizan), donated by Merck in the 1980s, is effective for up to a year. It has the added benefit of helping with intestinal worms, scabies, and head lice, which are common problems in the areas where this disease is endemic. Ivermectin must be given yearly for 12-15 years.
Hey Doc! In your research did you come across the cost of Ivermectin or Azithromycin for these treatments in some of these seriously impoverished countries? Do the individuals that are most likely to become infected have the resources to pay for the yearly Ivermectin treatment when some of them make the equivalent of $1-$5 US dollars daily? I know there are government programs that pay for these, but am unsure of how widespread they are. Thanks for the great article, I cant wait to read your next one!
Hello!Thanks for the comment- those are great questions! I can't speak to what is involved in the actual distribution of the drugs, but let me share what I do know. Two pharmaceutical companies donate the drugs in question for use in eliminating these diseases; Pfizer donates Zithromax® (azithromycin) for trachoma and Merck donates Mectizan® (ivermectin) for onchocerciasis. Pfizer co-established the International Trachoma Initiative (ITI), which is the organization that manages the distribution of Pfizer's Zithromax donations. The ITI works with several health organizations- both governmental and non-governmental- to help achieve the WHO goal of eliminating blinding trachoma via the SAFE strategy. More information from Pfizer here: http://www.pfizer.com/responsibility/global_health/international_trachoma_initiativeMerck has developed the Mectizan Donation Program, through which they have pledged to donate Mectizan “to all who need it, for as long as needed.” Similar to Pfizer, Merck partners with various organizations to get the drug to those who need it. More information from Merck here: http://www.merckresponsibility.com/access-to-health/key-initiatives/merck-mectizan-donation-program/I hope that helps!