A Randomized Trial to Assess the Effect of Fluoroquinolone Metaphylaxis on the Fecal Prevalence and Quinolone Susceptibilities of Salmonella and Campylobacter in Feedlot Cattle.

The study objective was to determine effects of fluoroquinolone metaphylaxis on fecal prevalence of Salmonella and Campylobacter and fecal prevalence of quinolone-resistant Salmonella and Campylobacter in feedlot cattle. On Day 0, cattle (n = 288) at risk for bovine respiratory disease (BRD) were randomly assigned to either a nontreated control pen (12 pens) or a fluoroquinolone-treated (enrofloxacin; Baytril® 100) pen (12 pens). Rectal fecal samples were collected from cattle on days 0, 7, 14, 21, and 28. Feces were cultured for Salmonella enterica and Campylobacter spp. using enrichment and selective isolation methods, and confirmed by serology and PCR. Susceptibilities to nalidixic acid and ciprofloxacin were determined using microbroth dilution methods. Data analyses were performed using linear mixed models. Overall, Salmonella sp. and Campylobacter spp. were recovered from 10.2% (139/1,364) and 12.4% (170/1,364) of the fecal samples, respectively. Campylobacter species included hyointestinalis, jejuni, and coli. Neither Salmonella sp. nor Campylobacter spp. prevalence was significantly impacted by fluoroquinolone treatment (p = 0.80, p = 0.61, respectively). However, Salmonella prevalence differed between study weeks (p < 0.01) with prevalence decreasing over time. Before treatment, 98.9% (91/92) of Salmonella isolates were susceptible to nalidixic acid and ciprofloxacin. All Salmonella recovered posttreatment (n = 43) were susceptible to both antimicrobials. The majority of Campylobacter spp. recovered before treatment were resistant to nalidixic acid (23/35; 65.7%) and ciprofloxacin (21/35; 60.0%). There was no significant treatment by week interaction (p = 0.85) or treatment effects (p = 0.61) on the posttreatment prevalence of Campylobacter resistance. There was, however, a significant week effect (p = 0.05), with Campylobacter resistance prevalence decreasing over time. In this 28-day study, we found no evidence that a fluoroquinolone used for metaphylaxis significantly impacts fecal prevalence of Salmonella sp. or Campylobacter spp. or the fecal prevalence of nalidixic acid or ciprofloxacin resistance.

Efficacy of 10% imidacloprid + 2.5% moxidectin topical solution (Advantage Multi® for Dogs) for the prevention of heartworm disease and infection all month long.

BACKGROUND: Prior work has shown that the levels of moxidectin in dogs treated with Advantage Multi® for Dogs (Bayer Animal Health) remain at a high plasma concentration for the full month after application. The objective of this study was to demonstrate the efficacy of 10% imidacloprid + 2.5% moxidectin topical solution (Advantage Multi® for Dogs, also known as Advocate® for Dogs) for the prevention of heartworm infection and disease 30 days after just one application. METHODS: Two groups of eight dogs each were included. Dogs in Group 1 received the product (Advantage Multi® for Dogs) while those in Group 2 remained as nontreated controls. All dogs entering the study completed a physical examination including examination for Dirofilaria immitis antigen and circulating microfilariae. Dogs in Group 1 were treated on Study Day (SD) -30 as per the label recommendation. Thirty days later (SD 0) dogs in Groups 1 and 2 were subcutaneously infected in the inguinal region with approximately 50 infective third-stage D. immitis larvae ("Missouri" isolate). Blood was collected on SDs 120 and 147 for examination for D. immitis antigen and circulating microfilariae. On SD 148, all animals were euthanized and necropsied for recovery of adult heartworms. All procedures were performed in accordance with the VICH GL9 guidelines. RESULTS: Examination and worm counts made at necropsy showed no heartworms in the treated dogs (Group 1) compared with six of eight nontreated dogs (Group 2) with heartworms (range of 2-33). The treated dogs (Group 1) had significantly fewer heartworms (p < 0.05) compared with the nontreated controls (Group 2). CONCLUSION: The results demonstrated that 10% imidacloprid + 2.5% moxidectin topical solution (Advantage Multi® for Dogs) is efficacious for the prevention of heartworm infection and disease all month long with no observation of treatment-related adverse events.