Guinea Pigs Develop Cutaneous Basophilia after Repeated Infestations by Nymphs of the Tick Amblyomma triste

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

This study investigated the development of resistance in guinea pigs to nymphs of Amblyomma triste ticks after repeated infestations. Guinea pigs were infested thrice, at 30-day intervals, with 30 nymphs of A. triste per animal per infestation. Acquisition of resistance was evaluated by determining: nymph yielding rate, engorgement period, and weight. Skin biopsies of tick bite sites were collected at 24, 48, and 96 h after tick attachment for inflammatory cell counts. Engorged nymphs weighed 5.53 mg +/- 1.9 in re-infested hosts (56.6% less than in primary infestation) and took 6.9 days +/- 2.16 to feed in the third infestation (14.5% more than in the first infestation). Guinea pigs yielded 78% +/- 7.2 of nymphs in the re-infestation (11.6% less than in the primary infestation). In addition, a marked increase in basophil influx was observed from the first infestation onward; 69% of infiltrated cells were basophils in re-infested hosts 24 h after tick attachment. No basophils were seen at this time in primary infested animals. That number increased to 84.7% 48 h post attachment in re-infested hosts (73.2% more than in the primary infested ones) and decreased markedly 96 h post attachment in both groups (2.6% and 1% of basophils in the third and first infestation, respectively). We conclude that guinea pigs acquire resistance against nymphs of A. triste ticks after repeated infestations and that a cutaneous basophilia must play a crucial role in such a mechanism.