An old man walking in Lushoto, Tanzania

Onchocerca volvulus, the parasite that causes onchocerciasis, currently infects 37 million people worldwide as Aimée Peck explains

This summer I filmed a documentary in Tanzania to help draw attention to the burden of onchocerciasis, a parasitic disease that causes debilitating blindness and dermatitis.  In the aftermath of a highly effective control campaign initiated in the late 1980’s, the overwhelming perception of onchocerciasis today is that it is a disease of the past.  In fact, onchocerciasis continues to be a very real problem in endemic communities, accounting for the annual loss of 1 million disability-adjusted life-years. (1)  It is imperative that control programs continue to receive the support they need in order to protect the nearly 100 million people who remain at risk of infection. (2) What follows is a discussion of our main findings in Tanzania.  In the spirit of this project, I have used quotations taken from our film to introduce the main issues covered.

“You know, onchocerciasis is one of the neglected tropical diseases, and because it is not a well-publicized disease, sometimes people do not find it necessary to do anything ing about it…” 
John Kilimunana, District Onchocerciasis Coordinator, Muheza District

Onchocerciasis is grouped with schistosomiasis, leprosy, filariasis and a number of other diseases as one of the neglected tropical diseases (NTDs). An estimated one billion people, one-sixth of the world’s population, suffer from these diseases which most often strike the poorest and most vulnerable individuals in tropical and sub-tropical areas. 

Onchocerca volvulus, the parasite that causes onchocerciasis, currently infects 37 million people worldwide (3) and is transmitted from person to person via female blackflies of the genus Simulium.  Although onchocerciasis is endemic in parts of Latin America and Yemen, the African continent carries the greatest disease burden by far.  It is estimated that 300,000 people are blind from onchocerciasis, with 40,000 new cases of onchocercal blindness occurring each year. (4) There is an effective medical treatment for onchocerciasis, ivermectin (Mectizan^TM), which has been available for free since 1987 through the pharmaceutical company Merck & Co., Inc as part of the Mectizan Donation Program. 

“People could not work, could not sleep…they do not sleep during the night, and when they wake up in the morning, they cannot do anything…”
Harrieth Hamis, Field Coordinator for Tanga CDTI Project

Before mass treatment with ivermectin campaigns began in 1987, onchocerciasis was seen as a significant challenge to development in endemic areas areas.  Blindness and skin disease caused depopulation of fertile land near rivers and in the 1970’s onchocerciasis was presumed to be responsible for annual economic losses of US$ 30 million. 

With the commencement of control strategies in onchocerciasis-endemic areas, prevalence of onchocerciasis was drastically reduced. Populations began reclaiming fertile land and productivity increased accordingly.An estimated US$ 3.7 billion in increased labor and agricultural productivity was observed in participating countries, (5) and the decline in onchocerciasis cases was heralded as one of the greatest success stories in modern medicine.

            “…many people are sick, many others are infected, and the burden of the disease, it is big - but I do not know whether many people know this or not…”
Abdul Daffa, District Onchocerciasis Coordinator, Lushoto District

Community-Directed Treatment with Ivermectin (CDTI) is currently regarded as the most effective long-term treatment solution for onchocerciasis.  It is hoped that after 20-25 years of once-yearly treatment, ivermectin, which kills the infective stage of O. volvulus, will interrupt transmission and onchocerciasis will be eliminated - although some experts believe onchocerciasis will never be eliminated with ivermectin alone and call for research into additional pharmaceuticals. (2)

During our time in Tanzania we uncovered several challenges that threaten the sustainability of CDTI programs.  For example, the work of getting ivermectin to people in endemic villages is carried out by a small number of individuals who receive very little compensation for their essential services. At the village level, two Community Drug Distributors (CDDs) from each village travel to a district drug dispensary to pick up their village’s supply of ivermectin, most times on foot.They are then responsible for personally witnessing the ingestion of ivermectin tablets by every eligible member of their village.  In exchange for this work, the CDDs are compensated roughly what it costs to purchase one soda, per day, for seven days. 

 Many times it takes CDDs more than seven days to complete distribution to the entire village. Once their meager food stipend runs out, they either complete their distribution activities going without food all day, or depend on the generosity of people in the village to feed them. Although their services are greatly appreciated by the other members of the village, we heard many CDDs tell us that more often than not, families simply do not have food or other means of compensation to spare for the CDDs. 

Ivermectin distribution is often scheduled during harvest time to avoid the rainy season, and during distribution the CDDs are taken away from their own fields.  Every CDD we spoke to asked that the government furnish some additional support to balance the costs of distributing ivermectin. Lymphatic filariasis, another neglected tropical disease, is endemic in parts of northeastern Tanzania and the pharmaceutical company GlaxoSmithKline currently donates albendazole for its treatment.  Recently albendazole has been added to the CDTI program for distribution with ivermectin.  One CDD mentioned that a pair of rain boots would help him do his job faster because delays in the arrival of ivermectin or albendazole to the district dispensaries have caused him to have to distribute ivermectin during the rainy season. 

At the district level, the problem of inadequate support is also apparent. Essential duties of the District Onchocerciasis Coordinators (DOCs) include educating communities about onchocerciasis and the importance of taking ivermectin, training of CDDs, procurement of ivermectin, and periodical surveying of onchocerciasis disease burden in their district. When asked what would be the one thing he would ask for that would help him do his job better, a DOC in Muheza told us exasperatedly, “four wheel drive!” Currently, DOCs travel on African Programme for Onchocerciasis Control (APOC)-issued motorbikes.  A four-wheel drive vehicle would significantly improve the ability of the DOCs to reach communities and establish a good working relationship, resulting in greater efficiency of the program.

It has been recognized in the context of onchocerciasis control that involving communities in the management of CDTI is critical for establishing and maintaining program sustainability.(1) (6) These communities are highly sensitized and become extremely efficient at distributing ivermectin; they have achieved treatment coverage rates above 85% in even the most remote areas.  However, these positive outcomes come at a significant cost to the people forming the core of the program who find themselves with more responsibilities but less resources with which to carry out those responsibilities.  This problem will only get worse if a decision is made in the future to include other drugs in addition to albendazole for distribution with ivermectin.  Essential individuals at the district and community levels are not receiving the support they need to continue to distribute ivermectin, and this must change if we hope to continue with CDTI until O. volvulus is eliminated.

            “Sometimes we focus on the killing diseases because we see people being killed     instantly or the disease shows us that the people are dying.  But disease like onchocerciasis, they kill people slowly, and it leaves them more prone to malaria,  HIV, and TB…”
Dr. Grace Saguti, Program Manager, National Eye Care and Onchocerciasis Control Program

Neglected tropical diseases like onchocerciasis cannot be ignored.  Not only do they maim, disfigure, and cause significant mortality in their own right, they can also increase the likelihood that a person will succumb to one of the “faster” killers like malaria, tuberculosis, or HIV/AIDS.  By interfering with an individual’s ability to work and generate income, NTDs chip away at the social safety nets that protect community members from other acute, preventable, or treatable illnesses. If due attention is paid to diseases like onchocerciasis that slowly weaken populations, perhaps we might see an associated reduction in morbidity and mortality from the “big killers” as the ability of the population to cope increases.

Onchocerciasis can teach us much about what can happen when a disease comes close to elimination after a reportedly successful and well-publicized control campaign.  It is a common observation among epidemiologists that the last steps towards elimination of a disease that has been drastically reduced from a formerly pervasive level often becomes paradoxically difficult. With today’s burden of O. volvulus infection at 37 million people, the response to the great successes of the Mectizan Donation Program must be met with a movement to increase support for the types of grass roots drug distribution strategies that have proven to be so successful in Tanzania and elsewhere.

Aimée Peck
97 Kellogg Building
Dartmouth Medical School
Hanover, New Hampshire 03766
Aimee.R.Peck@Dartmouth.Edu

 

(1) World Development Report: Investing in Health. 1993 New York, NY: Oxford University Press.  

(2)African Programme for Onchocerciasis Control.  Final communiqué of the 11^th session of the Joint Action Forum of APOC, Paris, France, 6-9 December 2005.   

(3)Basanez MG, Pion SDS, Churcher TS, Brietling LP, Little MP, Boussinesq M. River Blindness: A Success Story under Threat? 2006 PLoS Medicine, Vol 3 Issue 9.

(4)Hopkins AD.  Ivermectin and onchocerciasis: is it all solved?  2005 Eye, No 19 p1057-1066.

(5)Richards FO, Boatin B, Sauerbrey M, Seketeli Azodoga. Control of onchocerciasis today: status and challenges.  2001 Trends in Parasitology, Vol 17 No 12.

(6) Thylefors B, Alleman M.  Towards the elimination of onchocerciasis.  2006 Annals of Tropical Medicine and Parasitology, Vol 100 No 8.

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This entry was posted on Friday, October 26th, 2007 at 2:12 pm and is filed under Communicable Diseases, NTD, Articles. You can follow any responses to this entry through the RSS 2.0 feed. You can trackback from your own site.