title: Guinea pigs develop cutaneous basophilia after repeated infestations by nymphs of the tick Amblyomma triste.
abstract: 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.
authors.affiliation: Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista, Jaboticabal, Brazil.
authors.forename: Flávio S
authors.initials: FS
authors.lastname: Otávio
authors.forename: Gervásio H
authors.initials: GH
authors.lastname: Bechara
mesh_terms: D000818:Animals; D001491:Basophils / Q000166:cytology / Q000276:immunology*; D005260:Female; D006168:Guinea Pigs; D012871:Skin Diseases / Q000276:immunology* / Q000473:pathology; D013987:Ticks / Q000502:physiology*