Efficacy of the Bm86 antigen against immature instars and adults of the dog tick Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae)

Abstract

The Bm86 antigen has been used to control ticks of the Boophilus genera in integrated programs that also include the use of acaricides. Because of recent phylogenetic studies have lead to the inclusion of all Boophilus species within the Rhipicephalus genera, we aimed to investigate the efficacy of the Bm86 antigen on the biotic potential of Rhipicephalus sanguineus. Domestic dogs were vaccinated with Bm86 and challenged with the three instars of R. sanguineus. Male and female mongrel dogs were divided into two groups of four animals each, comprising non-vaccinated and vaccinated animals. Immunized dogs were given two doses of an experimental formulation containing 50mug of recombinant Bm86, at 21 days interval while the other group was given placebo, consisting of the same preparation without Bm86. Each dog was challenged 21 days after the last dose with 250 larvae, 100 nymphs and 55 adults (25 females and 30 males) released inside feeding chambers (one per instar) glued to their shaved flank. The effect of the vaccination was evaluated by determining biological parameters of ticks including the yield rates of larvae, nymphs and adult females. Adult females engorged weight, egg mass weight, efficiency rate of conversion to eggs (ERCE) and hatchability. In addition, sera were collected from dogs at 0, 21, 36, 45 and 75 days after the vaccination and used for the detection of specific antibodies by ELISA. Collection rates of larvae, nymphs and adult females fed on vaccinated dogs were significantly (p<0.05) reduced by 38%, 29% and 31%, respectively, as compared with non-vaccinated controls. Significant reductions were also observed in weight of engorged females and egg mass, in ERCE, but not in the hatch rate of ticks fed on immunized dogs. ELISA data revealed a marked and significant increase in optical densities of sera from vaccinated animals after the second dose of Bm86. We concluded that the Bm86 antigen used as a vaccine for dogs reduced the viability and biotic potential of the R. sanguineus.

Efficacy of rBm86 against Rhipicephalus (Boophilus) microplus (IVRI-I line) and Hyalomma anatolicum anatolicum (IVRI-II line) infestations on bovine calves

“…Early experiment with Bm86-based vaccines demonstrated cross-protection against Rhipicephalus (Boophilus) annulatus and Rhipicephalus (Boophilus) decoloratus infestations and conferred partial protection against Hyalomma and Rhipicephalus spp. (de la Fuente et al 2000;Fragoso and Hoshmand 1998;de Vos et al 2001;Perez-Perez et al 2010). However, immunization with Bm86 failed to protect animals against Amblyomma spp.…”

“…(B.) microplus de la Fuente et al 1995;Fragoso and Hoshmand 1998;de Vos et al 2001) and cross-protective against other ticks species (de Vos et al 2001;Perez-Perez et al 2010). The Indian cattle tick, R.(B.)…”

Lack of acquired resistance in dogs to successive infestations of Rhipicephalus sanguineus ticks from Brazil and Argentina

“…As described elsewhere (Perez-Perez et al 2010), blood for serologic analysis was collected by cephalic venal puncture and kept in vials without anticoagulant during 3 h at room temperature. The serum was then collected and frozen at -20°C until used for the ELISA test.…”

Formula to evaluate efficacy of vaccines and systemic substances against three-host ticks

“…This formula calculates the efficacy (E%) based on three variables: number of detached engorged adults (CRT), egg mass weight (CRO) and fertility of eggs (CRF) as follows (Canales et al, 1997;Andreotti, 2007;Miller et al, 2012): E% ¼ 100 Ã ½1 À ðCRT Ã CRO Ã CRFÞ: At the same time, control of the three-host tick species, such as Rhipicephalus sanguineus, Amblyomma variegatum and Ixodes scapularis, is also on the research agenda but a standard formula has not yet been established. In the last few years it has been proposed to validate vaccine efficacy by correlating antibody titers in individual animals with some of the tick parameters, which we included in the formula discussed below (Szabó and Bechara, 1997;Almazán et al, 2003Almazán et al, , 2005Trimnell et al, 2005;Pérez-Pérez et al, 2010;Anisuzzaman et al, 2012). Almazán et al (2005) calculated the efficacy of an antigen against the three-host tick I. scapularis, based only on its effect against larvae.…”

“…Trimnell et al (2005) tested a cement antigen as a vaccine in guinea pigs against R. sanguineus and in hamsters and rabbits against Ixodes ricinus, however, in all cases the final efficacy was not calculated and only some life cycle parameters were compared using ANOVA. Pérez-Pérez et al (2010) inoculated dogs with Bm86 antigen (Hebercani, Heber Biotec) to evaluate its efficacy against R. sanguineus; nevertheless they only compared some parameters with means comparison using a Student's t-test. Similar analysis has been done previously when R. sanguineus gut extract was tested as a vaccine in guinea pigs against this tick (Szabó and Bechara, 1997).…”