Disease Eradication in the 21st Century: Implications for Global Health

4. Onchocerciasis: From Control to Possible Eradication

4 Onchocerciasis: From Control to Possible Eradication Adrian Hopkins Abstract Our understanding of onchocerciasis has evolved over the last one and a half centuries from a description of an annoying skin disease, called aptly enough “craw craw,” to an understanding of its transmission cycle and important role in blindness. Various control measures have been instituted as new tools have become available, and these have moved the field toward elimination and possible eradication. A review of the evolution of the program and the lessons learned along the way may be beneficial to other disease programs as they begin the “long march to elimination”—a journey that seems to speed up as the end draws near, but which is made difficult by last remaining cases and the enormous efforts these require to address. Introduction The first lesson to learn in any war is to know the enemy. Onchocerciasis was first described in Ghana, where the intense itching and associated skin changes were given a local name of “craw craw” (Figure 4.1). O’Neil (1875) first described the presence of filaria in the skin of those infected. Robels (1917) described a similar disease in the Americas. The relationship with the black fly vector was demonstrated by Blacklock (1926), but the relationship to blindness was a bit more controversial. Hissette (1932) first described the effects of the microfilaria on the eye in the Belgian Congo, with Ridley (1945) fully describing the eye signs in what is now Ghana. As the basic disease pattern and method of transmission became better understood, it was clear that there were many variations. In Africa, there is a difference between the more blinding form of savannah onchocerciasis and its vectors and the forest form and its vectors (Duke and Anderson 1972; Duke and Garner 1976). In the Americas, the parasite is similar to the West African species and was probably brought over during slave trade (Zimmerman et al. 1994). However, the simulium vector is different, and it also differs between the various foci. InAfrica the vectors 36 A. Hopkins are again very different: some have potential long flight ranges while others are very short. Understanding vector movements as well as the disease foci is essential for the programs to succeed. However, understanding the disease (and its vectors) is not enough to begin a control/elimination program. This chapter reviews the evolution of the onchocerciasis program and the lessons learned along the way, which could be useful as other disease programs begin the long march to elimination or eradication where the last cases will take enormous efforts. Advocacy Creating awareness of a disease among medical and public health authorities and the general public is an essential step toward control. When Sir John Wilson (founder of the British Empire Society for the Blind, now known as Sightsavers) visited Ghana with his wife, Jean, in 1946, they realized firsthand the impact of the disease, both as a public health and a personal problem. Stuck in their vehicle in a riverbed with all the windows closed to avoid simulium bites, Jean remarked to Sir John (Coles 2006:50): You know, it’s no good calling this thing onchocerciasis. No one can pronounce it or spell it. You certainly can’t raise funds for it. Let’s call it “river blindness.” Since its establishment in 1950, Sightsavers has conducted research into onchocerciasis to back up their advocacy and to advance control (Crisp 1956). ĺ 1875 Parasite described ĺ1926 Role of vector clarified ĺ1932 Association with blindness ĺ1950s Efforts at awareness raising ĺ1950–60s First successful (vector) control efforts in Kenya ĺ1974 First program in West Africa OCP ĺ1987 The “new tool” Ivermectin and the beginning of distribution programs ĺ1991 Creation of OEPA ĺ1995 Creation of APOC ĺ1990s and 2000 New strategies for control – Epidemiological approaches – Public Health approaches – Shifting from control to elimination ĺ2012 The end game in the Americas ĺ2020 ?The end game in Africa Figure 4.1 Time line of efforts to eliminate onchocerciasis. Onchocerciasis: From Control to Possible Eradication 37 Advocacy is not a singular event to get a program going. As new tools become available, as new strategies develop, and as control changes to an elimination or eradication initiative, continuous feedback must be supplied to the political, funding, and scientific communities. The two major onchocerciasis programs—the Onchocerciasis Elimination Program for the Americas (OEPA) and the African Program for Onchocerciasis Control (APOC)—have been...