Transmission of Onchocerciasis in Wadelai Focus of Northwestern Uganda Has Been Interrupted and the Disease Eliminated

Abstract

Wadelai, an isolated focus for onchocerciasis in northwest Uganda, was selected for piloting an onchocerciasis elimination strategy that was ultimately the precursor for countrywide onchocerciasis elimination policy. The Wadelai focus strategy was to increase ivermectin treatments from annual to semiannual frequency and expand geographic area in order to include communities with nodule rate of less than 20%. These communities had not been covered by the previous policy that sought to control onchocerciasis only as a public health problem. From 2006 to 2010, Wadelai program successfully attained ultimate treatment goal (UTG), treatment coverage of ≥90%, despite expanding from 19 to 34 communities and from 5,600 annual treatments to over 29,000 semiannual treatments. Evaluations in 2009 showed no microfilaria in skin snips of over 500 persons examined, and only 1 of 3011 children was IgG4 antibody positive to the OV16 recombinant antigen. No Simulium vectors were found, and their disappearance could have sped up interruption of transmission. Although twice-per-year treatment had an unclear role in interruption of transmission, the experience demonstrated that twice-per-year treatment is feasible in the Ugandan setting. The monitoring data support the conclusion that onchocerciasis has been eliminated from the Wadelai focus of Uganda.

Transmission of Onchocerca volvulus by Simulium neavei in Mount Elgon Focus of Eastern Uganda Has Been Interrupted

“…The capacity of CDTI to incorporate (without collapsing) a 6-month treatment strategy in Africa has been debated (Boatin and Richards, unpublished data). This study, however, is the second report from Uganda that documents the ability of a CDTI program to rapidly expand from annual to 6-month treatments (the first being from Wadalai 21 ). The debate about two times per year treatment should move away from asking the research question about whether CDTI can tolerate two times per year to an operational/epidemiological question of when and where two times per year treatment needs to be implemented to advance the elimination agenda.…”

“…With institution of two times per year treatment in 2007, the UTG under annual treatment doubled (hence, UTG2, which is number of treatments but not individual persons). 21 National criteria for interruption of transmission. As part of the new elimination policy, the Ministry of Health (MOH) established the Uganda Onchocerciasis Elimination Expert Advisory Committee (UOEEAC) in 2008.…”

“…The UOEEAC unanimously recommended to stop interventions in Mount Elgon, despite the one positive child in the survey, while also urging any subsequent serosurveys to sample only children less than 10 years of age so as to avoid this problem in future. 21,33 The national guidelines now require the seroprevalence of children under 10 years of age to be less than 0.1%. 21 It was evident that deforestation rendered a large area unsuitable for S. neavei breeding and survival, resulting in progressive shrinking of the Mount Elgon focus from 1,500 km 2 in the 1950s to the current 250 km 2 .…”

“…21,33 The national guidelines now require the seroprevalence of children under 10 years of age to be less than 0.1%. 21 It was evident that deforestation rendered a large area unsuitable for S. neavei breeding and survival, resulting in progressive shrinking of the Mount Elgon focus from 1,500 km 2 in the 1950s to the current 250 km 2 . 15,16 In fact, tree felling and bush clearing was used in the 1940s and early 1950s successfully to control S. neavei in the Nyanza region of Kenya.…”

Interruption of Onchocerca volvulus Transmission in the Abu Hamed Focus, Sudan

“…The cutoff was chosen as 40 arbitrary units as previously reported. 24,26 A sample was reported positive only after a second independent positive repeat from the same stored specimen.…”