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For more detailed information, please contact the Mectizan Donation Program for a copy of the newly published brochure "Enabling Access to Health in Latin America: Mectizan for Onchocerciasis", which is available in print and in pdf format on the website in Spanish and English.

Eliminating Onchocerciasis in Latin America Using Mectizan:
A Goal Within Reach

Onchocerciasis is endemic in six countries in Latin America: Brazil, Colombia, Ecuador, Guatemala, Mexico, and Venezuela. Before Mectizan™, onchocerciasis control in Latin America was focused on surgical removal of nodules containing adult worms, occasional use of insecticides against black fly larvae, and the use of two drugs, diethylcarbamazine (DEC) and suramin.1 While these control efforts had some benefit, mostly at the individual level, they were of little value in reducing the transmission of onchocerciasis on a wide scale. Moreover, the use of DEC and suramin for the treatment of onchocerciasis was never widespread. These drugs are no longer recommended for onchocerciasis control because of the potential for serious side effects in onchocerciasis patients particularly irreversible eye damage and damage to the kidneys. ^1,2

The discovery and donation of Mectizan renewed interest in the control of onchocerciasis in the Americas. Widespread community-based mass treatment programs with Mectizan in Latin America began shortly after the announcement of the donation by Merck & Co., Inc. in 1987. Because of Mectizan's potential and availability free of charge, in 1991 the 35th Directing Council of the Pan American Health Organization passed Resolution XIV calling for the elimination of morbidity due to onchocerciasis in the Americas by 2007. The following year, the Onchocerciasis Elimination Program for the Americas (OEPA), a multi-national and multi-agency coalition, was established to realize Resolution XIV and to work towards the elimination of infection where feasible. ¹

Experimental data from Guatemala indicated that two doses of Mectizan given at seven-month intervals result in almost complete suppression of transmission from humans to black flies lasting six months after the second dose. Data from subsequent field studies in Guatemala have supported these observations. The observations have also been supported by experience within community-based mass treatments programs. In Ecuador, seven years of twice-annual mass treatment with Mectizan given consistently to more than 80% of the eligible population resulted in an interruption of transmission, which was evidenced by an absence of infection in children born after the initiation of distribution. Prior to distribution, more than 60% of children one to five years old were infected with O. volvulus. In addition, interruption of transmission after community-based mass treatment with Mectizan may have occurred in two additional foci -- one in Mexico and the other in the single endemic focus in Colombia.^3-7

Based on these data, the six endemic countries in Latin America have adopted a twice annual treatment strategy for at least 85% of all people at-risk of infection. This strategy, applied under circumstances unique to Latin America such as:

· the geographically localized nature of onchocerciasis
· the relatively small numbers of communities and people at risk for infection
· the presence of Simulium flies in much of the region that are relatively inefficient in transmitting infection

Makes elimination of onchocercal morbidity from the Western Hemisphere a feasible and realistic goal. ^8-9

In 2003, all six countries treated >90% of their ultimate treatment goals (range 90-100%) (Figure 1). This is a remarkable accomplishment considering that as recently as 2000, treatment ranged from 41-99% with four of the six countries treating less than 75% of the UTG.⁹

1. World Health Organization. Criteria for certification of interruption of transmission/elimination of human onchocerciasis. Geneva: World Health Organization; 2001. Document No.: WHO/CDS/CEE/2001.18a.

2. World Health Organization. Onchocerciasis and its control, report of a WHO Expert Committee on Onchocerciasis Control. Geneva: World Health Organization; 1995. Technical Report Series No.: 852.

3. Cupp E, Ochoa A, Collins RC, Ramberg FR, Zea-Flores G. The effect of multiple ivermectin treatments on infection of Simulium ochraceum with Onchocerca volvulus. Am J Trop Med Hyg 1989; 40(5): 501-506.

4. Cupp E, Ochoa A, Collins RC, Cupp MS, Gonzales-Peralta C, Castro J, Zea-Flores G. The effects of repetitive community-wide ivermectin treatment on transmission of Onchocerca volvulus in Guatemala. Am J Trop Med Hyg 1992; 47(2): 170-179.

5. Collins RC, Gonzales-Peralta C, Castro J, Zea-Flores G, Cupp MS, Richards FO, Cupp EW. Ivermectin: reduction in prevalence and infection intensity of Onchocerca volvulus following biannual treatments in five Guatemalan communities. Am J Trop Med Hyg 1992; 47(2): 156-169.

6. Guderian RH, Anselmi M, Espinel M, Mancero T, Rivadeneira G, Proaño R, Calvopiña HM, Viera JC, Cooper PJ. Successful control of onchocerciasis with community-based ivermectin distribution in the Rio Santiago focus in Ecuador. Trop Med Intl Health 1997; 2(10): 982-988.

7. World Health Organization. Onchocerciasis (river blindness). Wkly Epidemiol Rec 2002; 77(30):249-256.

8. The Carter Center. Final Report of the Conference on the Eradicability of Onchocerciasis. Atlanta: The Carter Center; 2002.

9. Data provided by OEPA during the 32nd Mectizan Expert Committee/Albendazole Coordination.