Efficacy of a new fixed-dose combination injectable (0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride) in Australian cattle against artificial infections of gastrointestinal nematodes.

We describe a new fixed-dose combination injectable (FDCI) formulated with doramectin and levamisole hydrochloride (HCl) to target broad and overlapping spectra of gastrointestinal nematodes (GINs) through two distinct modes of action. Here, we demonstrate the superior efficacy of the FDCI against mixed populations of cattle GINs in two dose confirmation studies conducted in Australia using artificially induced adult (Study 1) and immature (Study 2) GIN infections. Artificial infections consisted of Cooperia spp., Haemonchus placei, Ostertagia ostertagi, and Trichostrongylus axei. In both studies, cattle were inoculated with third-stage larvae and infections were confirmed by fecal egg count (FEC). Treatment groups in both studies were as follows: (1) negative control (saline, 0.9% sodium chloride), (2) positive control injectable endectocide (Study 1-0.2 mg/kg ivermectin; Study 2-0.2 mg/kg doramectin), (3) positive control injectable anthelmintic (7.5 mg/kg levamisole HCl), and (4) FDCI (0.2 mg/kg doramectin + 6.0 mg/kg levamisole HCl). Cattle were treated either 28 days (Study 1) or 6 days (Study 2) post-infection. On Days 14-16 (Study 1) or Days 20-21 (Study 2) post-treatment, cattle were euthanized and necropsied for the recovery, identification, and enumeration of worms. Treatment efficacy was calculated as reduction in worm burdens of treated cattle compared to saline-treated cattle, and treatments were considered effective if the geometric mean worm burden in the treatment group was reduced by ≥ 95% compared to the negative control group. In both studies, saline-treated cattle remained positive for GIN infections for the study duration. Ivermectin was less than 95% effective against Cooperia spp. (80.2%) and H. placei (24.8%) in Study 1, and levamisole HCl was less than 95% effective against Ostertagia spp. (47.1%) in Study 2. In contrast, the novel FDCI was 100% effective in treating adult and immature life stages of all cattle GINs included in the artificial infections, with no worms recovered at necropsy from doramectin + levamisole HCl-treated cattle. These data show a single administration of the FDCI provides broad-spectrum treatment of economically important cattle GINs.

Effectiveness of a fixed-dose combination injectable (0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride) against Rhipicephalus microplus and sucking lice infesting cattle.

Unmanaged tick and sucking lice infestations negatively impact the health and production potential of cattle. Described herein are two non-interference dose confirmation studies evaluating the efficacy of a single administration of a new fixed-dose combination injectable (FDCI) endectocide consisting of 0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride, against either laboratory-induced Rhipicephalus microplus infestations in Australia or naturally acquired sucking lice (Linognathus vituli) infestations in the US. This FDCI is available as Dectomax V® in Australia and New Zealand and as Valcor® in the United States. To evaluate therapeutic efficacy against R. microplus, 12 calves were each exposed to 10 infestations of ∼5000 larvae per infestation between Days -24 and -2. Calves were either treated on Day 0 with the FDCI or left untreated (control). Additional R. microplus infestations of ∼5000 larvae were conducted on Day 2 and then three times weekly to also evaluate persistent efficacy of the FDCI. Tick collections were conducted daily from Day -3. Group mean live tick counts, egg production, and egg viability were analyzed for significant differences between the two groups. To determine efficacy of the FDCI against lice, 24 cattle with active sucking lice infestations based on Day -7 counts were allocated to two groups and treated on Day 0 with either saline (control) or the FDCI. Lice counts were conducted weekly from Day 14 through 42 and again on Day 56. Mean group lice counts on each count day were compared between treatment groups. In the R. microplus study presented here, cattle in Queensland, Australia treated with the FDCI (Dectomax V®) showed > 90 % reduction in tick counts based on arithmetic means within 48 h of treatment when compared to untreated cattle, and counts were > 95 % reduced from post-treatment Day 5 through Day 30. In the sucking lice study conducted in the US, the FDCI (Valcor®) displayed 100 % efficacy against sucking lice infestations (L. vituli) from first count day (Day 14 post-treatment) through Day 35 and then 99.9 % efficacy through Day 56 post-treatment. No treatment-related adverse events were reported for cattle in either study. Using R. microplus and sucking lice as representative ectoparasites, these studies demonstrate the ectoparasite activity of doramectin is retained in the new FDCI.

Efficacy of a fixed-dose combination injectable (0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride) in Australian cattle against naturally acquired gastrointestinal nematode infections.

Australian producers have long used macrocyclic lactones (MLs) to successfully control cattle gastrointestinal nematodes (GINs) and consequently improve production parameters. However, the trajectory of ML resistance development in cattle GINs is following that of small ruminant nematode populations, highlighting a need for novel treatment options to provide efficacy in the current environment and interrupt the long-term establishment of ML-resistant GIN populations in Australian cattle. Here, we describe three field studies conducted in Australia to evaluate the efficacy of a single administration of a novel fixed-dose combination injectable (FDCI) endectocide against naturally acquired infections of cattle GINs. The FDCI is administered subcutaneously to deliver 0.2 mg/kg doramectin and 6 mg/kg levamisole hydrochloride (HCl). Study sites consisted of three farms in New South Wales (n = 2) and Victoria (n = 1). At each site, cattle were randomly allocated into one of three treatment groups: (1) untreated control (saline), (2) FDCI (0.2 mg/kg doramectin, 6 mg/kg levamisole HCl) or (3) positive control (0.2 mg/kg ivermectin). All treatments were administered on Day 0. Fecal samples were collected prior to treatment on Days -1 (Study 3) or 0 (Studies 1 and 2) and again on Day 14 (post-treatment) to evaluate efficacy via fecal egg count (FEC) and for coproculture. Adequacy of infection was confirmed at all three study sites, with Day 14 geometric mean (GM) FECs for saline-treated cattle ranging from 32.5 eggs per gram (EPG) to 623.7 EPG. FECs for FDCI-treated cattle were significantly reduced compared to saline-treated cattle (p ≤ 0.0001) on Day 14, with GM-based efficacy ≥ 99.7% at all three study sites. In contrast, ivermectin was 97.4% effective against cattle GINs in Study 1 but was only 47.2% and 39.8% effective at study site 2 and 3, respectively. Genus-specific efficacies suggest the presence of ivermectin-resistant Cooperia spp. (Study 1), Haemonchus spp. (Study 2) and Ostertagia spp. (Study 3) populations in the naturally infected cattle used in these studies. The post-treatment FEC and genus-specific efficacy estimations indicate the doramectin + levamisole HCl FDCI was highly efficacious against cattle GINs even in the face of ivermectin LOE at study sites 2 and 3. The efficacy of the new FDCI against both ML-susceptible and ML-resistant economically important cattle GINs in Australia affirms it is a valuable treatment option for producers operating in an environment of ML loss of efficacy.

Efficacy of a fixed-dose combination injectable (0.2 mg/kg doramectin + 6.0 mg/kg levamisole hydrochloride) in New Zealand cattle against naturally acquired gastrointestinal nematode populations with demonstrated resistance to doramectin.

Intensive farming practices and heavy reliance on anthelmintics have contributed significantly to the problem of macrocyclic lactone (ML) resistance in New Zealand. Farmers now have few options for effectively controlling cattle gastrointestinal nematodes (GINs) and regularly experience sub-optimal efficacy against economically important species. We present a novel fixed-dose combination injectable (FDCI) that simultaneously delivers 0.2 mg/kg doramectin and 6 mg/kg levamisole hydrochloride (HCl) to target a broad spectrum of cattle GINs in a single dose, providing an additional solution to endoparasite control in an environment of anthelmintic resistance. A dose confirmation study was conducted using naturally acquired infections of GINs in beef cattle in New Zealand. Cattle with GIN infections confirmed by fecal egg count (FEC) were randomly allocated (n = 12 per group) to the control (saline-treated), FDCI-treated or doramectin-treated group. On Day 0, cattle were weighed and administered a single subcutaneous injection of saline or endectocide. Rectal fecal samples were collected from each animal on Day 7 for individual duplicate fecal egg count (FEC) analysis, and coprocultures were conducted on pooled fecal samples within each treatment group. All animals were euthanized and necropsied for worm recovery on Days 14 through 16. Treatment efficacy was calculated based on reduction in FECs and worm burdens. All enrolled cattle were positive for GINs based on Day -5 FECs, with geometric mean (GM) FECs ranging from 337 to 521 eggs per gram (EPG). All saline-treated cattle remained positive for GIN infections for the study duration (Day 7 GM FEC = 427 EPG). Necropsy and worm recoveries revealed the presence of doramectin-resistant Cooperia oncophora, C. surnabada and Trichostrongylus longispicularis, as evidenced by ≤ 72.3 % efficacy of doramectin against these species. The new FDCI was ≥ 99.8 % effective against all GIN species, including ML-resistant C. oncophora, C. surnabada and T. longispicularis, providing broad-spectrum efficacy and eliminating economically important cattle GINs, including ML-resistant populations.

Reproductive and margin of safety of a fixed-dose combination injectable endectocide (0.2 mg/kg doramectin; 6.0 mg/kg levamisole hydrochloride) in cattle.

We present a fixed-dose combination injectable (FDCI) solution for cattle formulated for a single subcutaneous administration at a dose rate of 1 ml/25 kg of body weight to deliver a dose of 0.2 mg/kg of doramectin and 6.0 mg/kg of levamisole hydrochloride (5.1 mg/kg base equivalent). This drug product is marketed in the United States under the tradename Valcor® and in Australia and New Zealand under the tradename Dectomax V®. Both levamisole and doramectin have histories of safe and effective use in ruminants, with safety margins of 3X and 25X, respectively. Three studies were conducted to demonstrate the safety of the new FDCI: margin of safety (Study 1), and reproductive safety in sexually nulliparous beef heifers (Studies 2 and 3). In Study 1, 3-month-old sexually intact male and female calves were given either saline (control) or 1X, 2X, or 3X FDCI on Days 0, 14, and 28. General health, clinical, and neurological observations were made throughout the study, and clinical and pathology evaluations were made at study end. Studies 2 and 3 demonstrated the reproductive safety of the FDCI on sexually nulliparous beef heifers using estrus synchronization and timed artificial insemination. Treatments of either saline (control) or 3X FDCI were administered to coincide with either folliculogenesis, implantation, organogenesis, early gestation, or late gestation. Reproductive safety was demonstrated by evaluating rates of conception, calving, abortion, and stillbirth, dystocia scores, and calf health. In all studies, the FDCI at 1X, 2X, or 3X dosages was well tolerated. In the margin of safety study, 3X calves showed increased incidence of salivation for up to 8 h post-dosing compared to other groups. Injection sites were palpable post-dosing in all three FDCI groups but resolved by Day 28 in all but one animal each in 2X and 3X. In the reproductive safety studies, the FDCI had no effect on conception, pregnancy, fetal development, or postnatal viability. Injection site swelling was increased in frequency and duration compared to controls. The studies demonstrate the safety of the new FDCI in cattle from 3 months of age and in reproducing heifers during all reproductive stages from folliculogenesis through gestation and up to a month post-partum.