Scorecard Approach to Eliminate Onchocerciasis in Venezuela

Abstract

In the Americas, onchocerciasis has been eliminated in 11 of 13 endemic foci by mass administration of ivermectin. The remaining at-risk population resides in a contiguous cross-border transmission zone located in the Amazon jungle in northwest Brazil and southern Venezuela, known as the Yanomami Focus Area. Here, we describe the development and implementation of a data-driven tool, called the Scorecard Approach (SCA), for the 393 communities that comprise the Venezuela South Focus. The SCA was first applied in 2018 and is reassessed on an annual basis. This operational strategy seeks to prioritize communities with low ivermectin coverage while taking into account the nature and variation of other epidemiological and logistical variables. Numeric scores are assigned for each factor and added together to yield a composite score for each community that is categorized as high, medium, or low priority. In this way, the SCA serves as a valuable and comprehensive strategy for planning, monitoring, and maximizing programmatic efficiency. In addition, it has allowed the country to face the main challenges of this endemic area: its remoteness, its large areas of territory to cover, the semi-nomadic nature of the Yanomami people, and their continuous cross-border movements. For 2022, the SCA categorized 54 (13.7%), 108 (27.5%), and 231 (58.8%) communities as high, medium, and low priority, respectively. The results presented here show that prioritizing communities at risk and with greatest needs increases the feasibility of interrupting the transmission of onchocerciasis by 2025 in the last endemic focus in the Americas.

Figure 1.

Geographical distribution of hypo-, meso-, and hyperendemic communities in the Venezuela South Focus as determined by the prevalence of Onchocerca volvulus microfilariae detected microscopically in superficial skin biopsies.

Figure 2.

Yanomami shapono in the Venezuelan rainforest inhabited by Yanomami people and surrounded by a plantain garden as viewed from a Program helicopter (photo by O. Noya-Alarcón).

Figure 3.

Reported semiannual ivermectin treatment coverage (%) of eligible population in the Venezuela South Focus (2001–2022). The red horizontal line at 85% indicates the target minimum coverage.

Figure 4.

Number of communities (solid bars) and population at risk (gray line) registered in the Venezuela South Focus (2006–2022).

Figure 5.

Number of communities in the South Focus receiving four annual rounds of ivermectin treatment (3-month intervals) between 2009 and 2023.

Figure 6.

Flowchart of the iterative procedure for the definition, weighing, and final selection of a score for each variable in the SCA of the Venezuelan South Focus of onchocerciasis. SCA = Scorecard Approach.

Figure 7.

Frequency histogram of SCA. The range is 1–15 (mean ±SE: 6.8 ±0.16). The SCA scores of 11–15 (13.7%) were classified as high priority for program action, 6–10 as medium priority (27.5%), and 0–5 as low priority (58.8%). SCA = Scorecard Approach; SE = standard error.

Figure 8.

Maps of the onchocerciasis endemic area in the Venezuela South Focus showing number of priority communities for 2022 according to (A) OEPA and (B) SCA schemes. Med = medium; OEPA = Onchocerciasis Elimination Program for the Americas; SCA = Scorecard Approach.