Tick distribution depends on the drop-off rhythm of the previous stage and on the suitability for tick survival of the environment where they are disseminated. Studies were implemented in Burkina Faso to assess detachment pattern of engorged Amblyomma variegatum nymphs. Experiments were carried out with naturally infested cattle kept in a paddock or monitored when grazing community pasture. In the pasture, 80% of the nymphs detached between 14.00 h and 17.00 h while less than 25% did so in the paddock. Further investigation was implemented to assess whether the density of adult ticks might be modified by herd management. During the early dry season, zebus grazed in 4 plots fenced in natural savannahs and fallows. Two of the plots were used in the morning and the two others in the afternoon. Six months later, zebus were put in these plots, in turn, on 9 occasions. The number of A. variegatum adults picked up by the cattle in each plot was highly variable: they captured more ticks in the plots installed on good lush savannah and 3-fold more ticks in those where the herd had grazed in the afternoon during the previous dry season. An integrated tick control strategy taking these results into account is proposed.

A drop off rhythm of engorged Rhipicephalus appendiculatus Neumann was demonstrated for females and engorged nymphs, but not for larvae. Seventy per cent of 1279 engorged R. appendiculatus females dropped off the animals between 0800 and 1000 hr, while 66% of 2736 engorged nymphs dropped between 1600 and 1800 hr.

Females which were put on the animals at night (2000 hr), started to drop-off 24 hr later, than those put on in the day (0900 hr). Ticks which were fed on tick-sensitized animals also started to drop off 24 hr later, than those on tick-naive animals.

The implications of these results on tick control management are discussed.