Drop-off rhythms and survival periods of Hyalomma dromedarii (Acari: Ixodidae) fed on camels (Camelus dromedarius) in the Sudan

Flat larvae and adult Hyalomma dromedarii (Acari: Ixodidae) were fed on camels' ears. Feeding periods and drop-off rhythms of engorged females and nymphs together with engorgement weights of females were recorded. Newly hatched larvae and newly moulted adults were released in nylon mesh bags at the base of a tree. Their survival periods were seasonally monitored. H. dromedarii behaved exclusively as two-host ticks under field conditions. Larval-nymphal feeding periods ranged between 16 and 27 days according to the season, whereas females fed for 6-9 days. The peak drop-off rhythms of nymphs and females occurred between 18:00 and 20:00 h. Engorgement weights of females at dropping ranged between 0.84 g on day 6 and 0.60 g on day 9 of attachment. Survival duration of the flat adults showed that 18.4%, 5.3% and 4.8% of ticks released in January, April and July, respectively, survived for 1 month. A very few number of ticks survived for extra periods of 3 months, 2 months and 1 month in January, April and July, respectively. Increased air temperature and lower humidity decreased survival duration. Larvae released in February, May, June and August died within 1 week, although they survived under laboratory conditions (35 °C and 49-90% Relative Humidity (RH) for 49-60 days.