Table 2 Impact of ivermectin distribution on four aspects of onchocerciasis infection and transmission.
River Basin | Intervention Strategy | Impact of ivermectin treatment (Status in 2001) | |||
|---|---|---|---|---|---|
PH problem eliminated (CMFL= 0) | Prevalence of infection very low (< 10%) | Transmission interrupted (Rx ongoing) | Elimination (control ceased) | ||
Ivermectin only: | |||||
- River Gambia focus (A) | 6-Monthly ivm.1 since 1989 | √ | √ | ? | – |
- R. Corubal (B) (up to 1996) | 3-Monthly ivm. 1991–1996 | √ | √ | ? | – |
- R. Corubal (B) (from 1996 onwards) | No ivm. since 1996 | ? | Increasing prevalence | Transmission ongoing | – |
- Rio Gêba (C) | 6-Monthly ivm. since 1989 and no treatment since 1996 | √ | √ | ? | ? |
- Falémé (D), Bafing (E), Bakoye (F), Baoulé (G) | Annual ivm. since 1989 | √ | √ | ? | – |
- Vina Valley (Cameroon) | Annual ivm. since 1987 | √ | Prev. mf ≈ 20% in 1999 | Transmission ongoing | – |
Ivermectin + vector control: | |||||
- Tienfala focus (H) | Annual ivm. since 1987, and (ground) larv.2 since 1994 | √ | √ | ? | – |
- Bui Gorge focus (I) | Annual ivm. since 1987 (3-monthly from 1994–1996), and larv. from 1975–1996 | √ | Prev. mf up to 55% in 1998 | ? | – |
- Titira and Kouporgou focus (J) | Annual ivm. since 1988, and larv. since 1977 | √ | Prev. mf up to 50% in 1998 | Transmission ongoing | – |
- Milo and Sankarani (K) | Annual ivm. since 1989, and larv. since 1989 | √ | √ | √ | – |
- Asubende focus (L) | Annual ivm. since 1987, and larv. since 1990 | √ | √ | Transmission ongoing | – |
- Dienkoa (M) | Annual ivm. since 1988, and larv. since 1975 (with interruptions) | √ | √ | √ | – |
Ivermectin treatment after vector control: | |||||
- Bougouriba (N) | 4-Monthly ivm. since 1996, and larv. from 1975–1990 | √ | √ | Transmission ongoing | – |