Arthropods

Camels with mange due to S. scabiei were treated subcutaneously with ivermectin at 200 |g kg-1 twice at a weekly interval (Njanja, 1991; Nayee et al., 1994), twice (Opferman, 1985; Hashim and Wasfi, 1986; Raisinghani et al., 1989; Makkar et al., 1991) or three times (Maqbool et al., 1996) at approximately a 2-week interval, or three times (Radwan et al., 1987; Chellappa et al., 1989) at weekly intervals. The infestations resolved and no recurrence was evident during the course of the study, 12 months following treatment in one report. Hayat et al. (1997) found that a single 200 |g kg-1 subcutaneous dose of ivermectin reduced S. scabiei numbers by 99% at 45 days post-treatment in camels; Njanja (1991) found the same presentation and dose of ivermectin to be 100% effective against mild infestations by 3 weeks post-treatment, while Hassan et al. (1989) observed that a single subcutaneous injection of ivermectin at either 100 or 200 |g kg-1 was effective in eliminating S. scabiei from infested camels by 60 days post-treatment, although the lower dose was not examined against severe infestations. Dafalla et al. (1987) cleared sarcoptic mange from six of seven camels with a single subcutaneous treatment of ivermectin at 200 |ig kg-1, but the last animal required a second treatment, which was administered 35 days after the first. In contrast, Abu-Samra (1999) reported that poor results (40% cure) were obtained against S. scabiei following two treatments with ivermectin at 200 | g kg-1 at an interval of 5 weeks, probably as a result of eggs surviving treatment and re-establishing infestation, suggesting that a second treatment is required before eggs have the opportunity to produce patent adults.

Ivermectin administered subcutaneously at 200 | g kg-1 was ineffective against Hyalomma spp. ticks on camels (Tager-Kagan and Robin, 1986; van Straten and Jongejan, 1993) and larvae of the fly Cephalopina titillator (Tager-Kagan and Robin, 1986; Robin et al., 1989). In contrast, Raisinghani et al. (1989) found the same dose and route to be effective in removing Hyalomma dromedarii by 5 days after treatment, and Sharma (1992) found this treatment to be effective against C. titillator.

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