[Epidemiology of Cowdria infection in Senegal. I. Study of the transmission and infection level in Amblyomma variegatum (Fabricius, 1794) in the Niayes region].

The authors report the results of research on infection rates of Amblyomma variegatum nympha and imago populations by Cowdria ruminantium in the Niayes region as well as on the transmission rates of A. variegatum by the various stases. The experiments were carried out on sheep from the Sahelian zone where the vector tick is not endemic. The infection rate, estimated by inoculating sheep with ground ticks, gave the following prevalences: t = 13.3% for nymphae and t = 1.2% for adults. The transmission rates calculated on the basis of a daily count of nymphae and adults (which were marked), gave the following minimum values: 11.1% for nymphae and 9.5% for imagos. In-station studies, using nymphae and imagos gorged at their larval or nymphal stase on infected sheep, showed infection rates of 100%. The transmission by nymphae and imagos originating from the same groups amounted to 80%. Intrastadial transmission assays by males and females previously gorged on sheep in hyperthermia, were unsuccessful.