Eprinomectin pour-on: Prevention of gastrointestinal and pulmonary nematode infections in sheep.

The present study was conducted to further characterize the anthelmintic activity of the 0.5% w/v topical formulation of eprinomectin (EPRINEX® Pour-on, Merial) when administered at 1 mg/kg body weight to sheep in preventing the establishment of induced gastrointestinal and pulmonary nematode infections. Thirty-six female Merino sheep (∼4 months of age, weighing 27.0-36.0 kg) were blocked by pre-treatment body weight to form blocks of four animals. Within blocks, the animals were randomly allocated to either remain untreated (control) or be treated once with EPRINEX® either on Day 0, Day 7 or Day 14. Starting on Day 15, the sheep were given trickle infections with infective larvae of seven species of gastrointestinal nematodes and Dictyocaulus filaria lungworms daily for seven consecutive days. Five weeks after completion of the daily challenge (Day 56), the animals were necropsied for parasite recovery and count. Treatment with EPRINEX® prevented the establishment (>90%, p ≤ 0.027) of D. filaria, Teladorsagia circumcincta (pinnata/trifurcata), Cooperia curticei, Nematodirus battus, Trichostrongylus colubriformis and Oesophagostomum venulosum for at least 21 days, and of Haemonchus contortus and Trichostrongylus axei for at least 14 days. Sheep in the groups treated with EPRINEX® at Days 7 and 14 had significantly (p ≤ 0.018) higher Day -1 to Day 56 wt gains than the untreated controls. No treatment-related health problems or any other health problems were observed throughout the study.

Efficacy of oral afoxolaner plus milbemycin oxime chewables against induced gastrointestinal nematode infections in dogs.

The efficacy of oral afoxolaner plus milbemycin oxime combination chewables against induced gastrointestinal nematode infections in dogs was evaluated in six separate studies. Two studies were performed to evaluate the efficacy of the product against Toxocara canis, two studies evaluated the efficacy against Toxascaris leonina, one study evaluated the efficacy against Ancylostoma braziliense, and one study evaluated the efficacy against Ancylostoma caninum. In the A. caninum study, the efficacy of milbemycin oxime alone and afoxolaner alone was also evaluated. Dogs in all studies were inoculated with infective eggs or larvae and confirmed to have patent infections based on a fecal examination prior to allocation to study group and treatment. Each study utilized a randomized block design with blocks based on pre-treatment body weight. All dogs were assigned to blocks based on body weight, and then each dog within a block was randomly assigned to treatment group. There were two groups of 10 dogs each in the T. canis, T. leonina, and A. braziliense studies: 1) an untreated (control) group and 2) a group treated with afoxolaner plus milbemycin oxime chewables (NexGard Spectra(®), Merial). This group was treated at a dose as close as possible to the minimum effective dose of afoxolaner and milbemycin oxime (2.5mg+0.5mg per kg body weight, respectively) once on Day 0 using whole chews. There were four groups of 10 dogs each in the A. caninum study: 1) untreated (control), 2) NexGard Spectra(®) as described above, 3) milbemycin oxime alone (dose of at least 0.5mg per kg of body weight) and 4) afoxalaner alone (dose of at least 2.5mg per kg body weight). For parasite recovery and counts, dogs were euthanized humanely and necropsied seven days after treatment. The efficacy of the afoxolaner plus milbemycin oxime combination was ≥98% against T. canis, ≥95.8% against T. leonina, and 90.2% against A. braziliense. Efficacy of the combination against A. caninum was 99.7%, while the efficacy of milbemycin oxime alone was 99.6% and the efficacy of afoxolaner alone was 2.1%. Dogs treated with afoxolaner plus milbemycin oxime chewables had significantly (p≤0.0002) fewer nematodes than the untreated controls in all studies. There were no adverse events or other health problems that were related to treatment with Nexgard Spectra(®) in these studies. The results of these controlled studies demonstrate the high efficacy of the afoxolaner plus milbemycin oxime chewables against a broad range of canine intestinal nematode infections.

Humoral immunity and injection-site reactions in cattle vaccinated with a multivalent clostridial vaccine administered via subcutaneous injection or via transdermal needle-free injection.

OBJECTIVE: To evaluate injection-site reactions and serum antibody titers in cattle vaccinated with a clostridial vaccine administered SC or via needle-free transdermal injection. ANIMALS: Sixteen 11-to 12-month-old Herefords. PROCEDURES: Cattle in 2 groups were vaccinated on days 0 and 28 with a commercially available multivalent clostridial vaccine administered SC or transdermally Injection sites and serum antibody titers were evaluated at several time points after vaccination. Serum antibody titers against Clostridium perfringens beta toxin, Clostridium novyi alpha toxin, and Clostridium septicum alpha toxin were determined with an ELISA; Clostridium sordellii lethal toxin titers were determined with a toxin neutralization assay. RESULTS: Firm injection site swellings developed in cattle vaccinated via either route; however, at several observation times, swellings were significantly smaller in cattle vaccinated transdermally. Serum titers against C perfringens beta toxin and C septicum alpha toxin did not differ significantly between groups after vaccination; serum titers against C novyi alpha toxin were not significantly different between groups, except on days 10 and 56, when they were significantly higher in cattle vaccinated SC. Titers against C sordellii lethal toxin were significantly higher in cattle vaccinated SC on several days after vaccination, but titers were not significantly different after day 49. CONCLUSIONS AND CLINICAL RELEVANCE: Transdermal vaccination of cattle resulted in serum antibody titers that were similar to those induced via SC vaccination and caused injection-site reactions that were significantly smaller. Transdermal vaccination may be an effective technique for vaccinating cattle against clostridial diseases while minimizing local reactions that often develop after clostridial vaccination.

Norovirus classification and proposed strain nomenclature.

Without a virus culture system, genetic analysis becomes the principal method to classify norovirus (NoV) strains. Currently, classification of NoV strains beneath the species level has been based on sequences from different regions of the viral genome. As a result, the phylogenetic insights of some virus were not appropriately interpreted, and no consensus has been reached to establish a uniform classification scheme. To provide a consistent and reliable scientific basis for classifying NoVs, we analyzed the amino acid sequences for the major capsid protein of 164 NoV strains by first using an alignment based on the predicted 3D structures. A Bayesian tree was generated, and the maximum likelihood pairwise distances of the aligned sequences were used to evaluate the results from the uncorrected pairwise distance method. Analyses of the pairwise distances demonstrated three clearly resolved peaks, suggesting that NoV strains beneath the species level can be classified at three levels: strain (S), cluster (C), and genogroup (G). The uncorrected pairwise distance ranges for S, C, and G were 0-14.1%, 14.3-43.8%, and 44.9-61.4%, respectively. A scheme with 29 genetic clusters [8 in genogroup 1 (G1), 17 in G2, 2 in G3, and 1 each in G4 and G5] was defined on the basis of the tree topology with the standards provided and was supported by the distance analysis. Of these, five clusters in G2 and one in G1 are newly described. This analysis can serve as the basis for a standardized nomenclature to genetically describe NoV strains.

Genogroup I and II noroviruses detected in stool samples by real-time reverse transcription-PCR using highly degenerate universal primers.

Genogroup I noroviruses from five genetic clusters and genogroup II noroviruses from eight genetic clusters were detected in stool extracts using degenerate primers and single-tube, real-time reverse transcription-PCR (RT-PCR) with SYBR Green detection. Two degenerate primer sets, designated MON 431-433 and MON 432-434, were designed from consensus sequences from the major clusters of norovirus based on the RNA-dependent RNA polymerase region of the norovirus genome. Viruses were extracted from stool samples within 20 min using a viral RNA extraction kit. Real-time RT-PCR for noroviruses generated semiquantitative results by means of the cycle threshold data and dilution endpoint standard curves. Presumptive product verification was achieved by evaluation of first-derivative melt graphs. Multiple clusters of noroviruses were identified simultaneously in a multiplex fashion by virtue of slight differences in melting temperature. The detection of 13 different genetic clusters suggests that the MON primers may serve as universal primers for most, if not all, of the noroviruses in a multiplex assay. Our technique provides a framework for broad application of real-time RT-PCR in clinical, environmental, and food testing laboratories for a wide range of noroviruses.

Prevalence of rotavirus and norovirus antibodies in non-human primates.

Rotavirus and norovirus are associated with a substantial burden of diarrheal disease in humans and some animals, but their role in acute viral gastroenteritis in non-human primates has not been established. We examined sera from five species of Old and New World monkeys and chimpanzees for antibodies to rotavirus and norovirus by enzyme immunoassays using RRV and three recombinant human norovirus capsid proteins, respectively. Most (88%) of the 3 Old World monkey species (mangabey, pigtail, and rhesus) and apes were seropositive for rotavirus. Norovirus antibody was prevalent in the three monkey species, with 53% (44/83) and 58% (48/83) seropositive for GI and GII strains, respectively. Eleven (92%) of the 12 chimpanzees tested were seropositive for GI norovirus. Given the high rate of infection with both viruses, the role of these agents in causing acute gastroenteritis in non-human primates and the value of these animals as models of infection and disease need to be assessed.

Epidemiologic and molecular trends of "Norwalk-like viruses" associated with outbreaks of gastroenteritis in the United States.

Between July 1997 and June 2000, fecal specimens from 284 outbreaks of nonbacterial gastroenteritis were submitted to the Centers for Disease Control and Prevention for testing for "Norwalk-like viruses" (NLVs). Specimens were examined by reverse-transcription polymerase chain reaction and direct electron microscopy for the presence of NLVs. Adequate descriptive data were available from 233 of the outbreaks, and, of these, 217 (93%) were positive for NLVs. Restaurants and events with catered food were the most common settings, and contaminated food was the most common mode of transmission. Genogroup II (GII) strains were the predominant type (73%), with genogroup I strains causing 26% of all NLV-positive outbreaks. Certain GII clusters (GII/1,4,j) were more commonly associated with outbreaks in nursing home settings than with outbreaks in other settings. Strain diversity was great: one potential new sequence cluster was implicated in multiple outbreaks, and strains belonging to a tentative new genogroup were identified.