SURVIVAL OF UNFED RHIPICEPHALUS-APPENDICULATUS (ACARINA, IXODIDAE) IN RELATION TO HOST-RESISTANCE AND ENVIRONMENTAL-FACTORS IN KENYA

Mean survival times for unfed ticks, Rhipicephalus appendiculatus Neumann exposed initially during the hot dry season (January) in Kenya were significantly higher than those of ticks exposed during the wet season (May). This was partly due to the timing of the next hot dry season which triggered the beginning of decline in survival, and partly due to the overall severity of the weather. The implication is that the time when the ticks feed affects the survival of the subsequent instar. The mean survival times for nymphs exposed initially during the wet and the hot dry seasons were 30 weeks and 44 weeks, respectively. Those for adult ticks ranged between 59—75 weeks and 62—79 weeks, respectively. Maximum survival times were, however, similar for adults but not for nymphs. Adult ticks had an initial period of 32—48 weeks of excellent survival, apparently independent of weather factors. Thereafter, mortality rates and adverse environmental factors were correlated. The survival of ticks fed on hosts of differing resistance status was also different. The most resistant host produced the smallest adult ticks and these gave the lowest survival, and vice versa. Male and female ticks from highly resistant hosts had similar survival, but the females from a moderately resistant host survived significantly better than the males. These results indicate the importance of weather and host resistance in R. appendiculatus survival. © 1990, Cambridge University Press. All rights reserved.