title: Possible acquired resistance of dogs successively infested by Amblyomma cajennense (Fabricius, 1787) (Acari: Ixodidae) nymphs.
abstract: The present study aimed to evaluate the occurrence of immune resistance in dogs successively infested with Amblyomma cajennense nymphs. Five animals were submitted to four consecutive infestations with A. cajennense nymphs, at fourteen-day intervals. For each infestation, 50 nymphs were used per animal and data on the parasitic and non-parasitic periods were recorded. The average recovering rate of engorged nymphs in the successive infestations were 52.0, 29.2, 9.6 and 12.8%, respectively, with a significant reduction (p<0.05) of this parameter from the second infestation onwards. The modal drop-off day of engorged nymphs was Day 4 of parasitism in all infestations. The average mortality rates of nymphs seen on the first, second, third and fourth infestations were 3.6, 3.2, 2.0 and 2.8%, respectively, with no significant differences among them (p<0.05). In addition, no significant differences were seen among the ecdysis rates for specimens recovered from successive parasitic challenges. The study results suggest that the acquired resistance of infested dogs had a negative effect on recovery rate of A. cajennense nymphs; however, it did not affect the other biological parameters evaluated.
authors.affiliation: Laboratório de Ectoparasitoses, Escola de Veterinária-EV, Universidade Federal de Minas Gerais-UFMG, Av. Antônio Carlos 6627, CEP 30161-970 Belo Horizonte-MG, Brazil.
authors.forename: Carolina Maria Vianna
authors.initials: CM
authors.lastname: de Freitas
authors.forename: Romário Cerqueira
authors.initials: RC
authors.lastname: Leite
authors.forename: Eduardo
authors.initials: E
authors.lastname: Bastianetto
authors.forename: Arildo Pinto
authors.initials: AP
authors.lastname: da Cunha
authors.forename: Ana Cristina Passos
authors.initials: AC
authors.lastname: de Paiva Belo
mesh_terms: D056704:Adaptive Immunity; D000818:Animals; D004283:Dog Diseases / Q000276:immunology*; D004285:Dogs; D026863:Ixodidae; D009758:Nymph; D013984:Tick Infestations / Q000276:immunology / Q000662:veterinary*