Possible acquired resistance of dogs successively infested by Amblyomma cajennense (Fabricius, 1787) (Acari: Ixodidae) nymphs

C M V De Freitas,A P Da Cunha,A C P De P Belo,R C Leite,E Bastianetto

doi:10.4322/rbpv.018e1007

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.

Highlights

In tropical regions, a vast variety of ticks infest dogs living either in urban areas, where Rhipicephalus sanguineus is the predominant species (SZABÓ et al, 2001; OYAFUSO et al, 2002), or in peri-urban and rural areas, where dogs are frequently infested with Amblyomma species, including Amblyomma cajennense (LABRUNA et al, 2000)
The present study aimed to evaluate the occurrence of immune resistance in dogs successively infested with Amblyomma cajennense nymphs
The study results suggest that the acquired resistance of infested dogs had a negative effect on recovery rate of A. cajennense nymphs; it did not affect the other biological parameters evaluated

Summary

Introduction

A vast variety of ticks infest dogs living either in urban areas, where Rhipicephalus sanguineus is the predominant species (SZABÓ et al, 2001; OYAFUSO et al, 2002), or in peri-urban and rural areas, where dogs are frequently infested with Amblyomma species, including Amblyomma cajennense (LABRUNA et al, 2000). The present study aimed to evaluate the occurrence of immune resistance in dogs successively infested with Amblyomma cajennense nymphs. 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.

Results

Conclusion