Feeding efficiency of larval Hyalomma truncatum (Acari: Ixodidae) on hosts previously exposed to ticks.

The effect of guinea pig response to feeding larval Hyalomma truncatum Koch ticks was studied by measuring the percentage of ticks engorging and molting, their engorged weight, and hemoglobin content. Four guinea pigs were infested with 100, 200, 400, and 1,000 larvae, respectively, on three occasions at 21-d intervals, followed by a fourth infestation with 500 larvae. During the second, third, and fourth infestations, significantly fewer ticks engorged on each guinea pig than during the first infestation. The greatest reduction in percentage molting occurred during the fourth infestation on the animal with successive exposure to 400 larvae; only 24% of the ticks that fed molted. Ticks with the lowest mean weight and hemoglobin content also engorged on this animal during the fourth infestation. Guinea pigs exposed to 200 and 400 H. truncatum larvae elicited the greatest change in feeding efficiency during the fourth infestation. However, these hosts had no effect on a single subsequent fifth infestation with Amblyomma cajennense (F.) nymphs, as greater than 95% successfully engorged.