Ability of an oral formulation of afoxolaner to protect dogs from Borrelia burgdorferi infection transmitted by wild Ixodes scapularis ticks

Abstract

A randomized, blinded, negative controlled study was conducted to determine whether treatment with afoxolaner (NexGard, Merial, Inc.) would prevent the transmission of Borrelia burgdorferi to dogs by wild caught Ixodes scapularis ticks. Twenty healthy dogs were randomly assigned to two groups of ten dogs each. Ten dogs were treated orally on Day 0 at a dose near the minimum recommended dose of afoxolaner of 2.5mg/kg (actual doses 2.5-3.1mg/kg) and ten control dogs were not treated. On Day 28, each dog was infested with approximately 50 adult unfed wild caught I. scapularis that had a 67% B. burgdorferi infection rate (determined by polymerase chain reaction). On Day 33, live ticks were counted and removed. No ticks were found on treated dogs while control dogs had an average of 21.4 ticks. To detect infection, the B. burgdorferi-specific C6 antibody SNAP 4Dx test (IDEXX) was performed on serum collected before infestation (all dogs seronegative on Days -6 and 27) and on Days 48, 63, 77 and 92. The ten treated dogs remained seronegative through the end of the study (Day 92), while nine out of the ten control dogs were infected, as demonstrated by their seroconversion to being positive for the presence of the B. burgdorferi-specific C6 antibody starting on Day 48. In this study, all dogs treated with NexGard 28days prior to challenge with wild caught I. scapularis ticks were protected from B. burgdorferi infection, while nine out of the ten untreated control dogs were infected.

ACVIM consensus update on Lyme borreliosis in dogs and cats

“…Whether this finding related to lack of efficacy or failure of compliance could not be determined from the study. In dogs, use of tick control products appropriately can lessen the risk of developing antibodies against Bb and A. phagocytophilum , and this is likely to occur in cats as well if the products are used as directed Statement: Whether Bb vaccines are used or not, there is strong consensus that tick control must be used not only to help prevent LB but also to prevent many other TBDs for which there are no vaccines available [EBM‐C].…”

“…The efficacy of tick control products is excellent, as proven by prevention of seroconversion after tick exposure challenge . However, compliance for using these products properly is an ongoing problem, and many veterinarians in Bb‐endemic areas also recommend Bb vaccinations, although the latter are not as efficacious when used alone.…”

“…The efficacy of tick control products is excellent, as proven by prevention of seroconversion after tick exposure challenge. 135,137,143 However, compliance for using these products properly is an ongoing problem, and many veterinarians in Bb-endemic areas also recommend ability of the spirochete to "hide" from the immune system in synovial membranes, down-regulating their immunogenic surface proteins, 152 and because of the existence of many strains for which there is no cross-reacting immunity. 99 The 3/6 panelists who dissented cited inconsistent efficacy and duration of immunity (see above), cost, need for proper tick control, lack of controlled studies with respect to tick control when assessing vaccines in the field, theoretical concerns for immune-mediated sequelae, 1,153…”

Evaluation of fluralaner as an oral acaricide to reduce tick infestation in a wild rodent reservoir of Lyme disease

“…More specifically, isoxazolines mostly act on the GABACl channel by blocking ion channel opening [17][18][19][20]. Isoxazolines, like sarolaner and afoxolaner, have been shown to kill adult ticks and prevent B. burgdorferi transmission in dogs [21,22]. Fluralaner, another member of this new family, is noted for its ability to kill ticks rapidly and for its long efficacy period following a single oral administration, when used in dogs [23,24].…”

Prevention of transmission of Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum by Ixodes spp. ticks to dogs treated with the Seresto® collar (imidacloprid 10% + flumethrin 4.5%)

“…Concerning the pathogens in focus of the reported studies, Bbsl and Ap, various actives and formulations have been tested regarding their capacity to prevent microorganism transmission from I. scapularis to dogs (Baker et al 2016;Blagburn et al 2004;Elfassy et al 2001;Honsberger et al 2016;Hunter et al 2002;McCall et al 2011;Spencer et al 2003), but according to the authors' knowledge, one of the reported studies is the first to test the prevention of pathogen transmission for up to 7 months after a single treatment (collar application).…”