Efficacy and safety of maropitant, a selective neurokinin 1 receptor antagonist, in two randomized clinical trials for prevention of vomiting due to motion sickness in dogs.

Maropitant (Cerenia), a selective neurokinin(1) receptor antagonist, was evaluated for efficacy and safety in prevention of vomiting due to motion sickness in dogs in two randomized clinical trials. One-hundred eighty-nine dogs with a history of motion sickness were enrolled at 26 veterinary clinics (across 12 US states) across the two trials; of these, 163 were fully evaluable, 19 were evaluable only for safety, and seven were not evaluable. Each trial used a two-period crossover design. Each dog was treated orally with placebo or maropitant (minimum dose of 8 mg/kg body weight using unit dosing) tablets at approximately 2 h (Trial 1) or 10 h (Trial 2) before an automobile ride of approximately 60 min, during which dogs were observed for signs of motion sickness. Following a 10-14-day washout period, each dog was administered the opposite treatment and taken for another journey (same route, driver and vehicle). Maropitant reduced the occurrence of vomiting compared to placebo by 86.1% or 76.5% when given approximately 2 or 10 h prior to travel, respectively. No significant clinical signs were observed after maropitant treatment. Maropitant was safe and effective in preventing vomiting due to motion sickness in dogs when administered at a minimum dose of 8 mg/kg body weight as oral tablets 2 or 10 h prior to travel.

Comparative efficacy of maropitant and selected drugs in preventing emesis induced by centrally or peripherally acting emetogens in dogs.

Maropitant (Cerenia; a novel, selective neurokinin(1) receptor antagonist), chlorpromazine, metoclopramide and ondansetron were compared in two randomized, placebo-controlled studies for efficacy in preventing emesis induced by emetogens acting centrally (apomorphine; Study 1) or peripherally (syrup of ipecac; Study 2) in dogs. In each study, ten male and ten female beagles were treated in a five-treatment, five-period crossover design. The five treatments were 0.9% saline (0.1 mL/kg), maropitant (1 mg/kg), metoclopramide (0.5 mg/kg), or chlorpromazine (0.5 mg/kg) all administered subcutaneously, or ondansetron (0.5 mg/kg) administered intravenously. One hour posttreatment dogs were challenged with apomorphine at 0.1 mg/kg intravenously (Study 1) or syrup of ipecac at 0.5 mL/kg orally (Study 2). Following emetogen challenge, dogs were observed for 30 min (Study 1) or 1 h (Study 2) for emesis. No clinical signs, other than those related to emesis, were observed. Efficacy of maropitant in preventing emesis induced centrally by apomorphine was not different (P > 0.05) from metoclopramide or chlorpromazine but was superior (P < 0.0001) to ondansetron. Efficacy of maropitant in preventing emesis induced by syrup of ipecac was not different (P > 0.05) from ondansetron but was superior (P

Safety and efficacy of injectable and oral maropitant, a selective neurokinin 1 receptor antagonist, in a randomized clinical trial for treatment of vomiting in dogs.

Maropitant (Cerenia), a selective neurokinin(1) receptor antagonist, was evaluated for safety and efficacy in treatment and prevention of acute vomiting due to various etiologies in dogs in a randomized clinical trial. Two-hundred seventy-eight dogs were enrolled from 29 veterinary hospitals. Two-hundred fifty-two were evaluable for efficacy, while 275 were evaluable for safety. A randomized block design was utilized (three maropitant- and one placebo-treated dog per block). Initial treatment was maropitant at 1 mg/kg body weight (0.45 mg/lb) or an equivalent volume of saline (placebo) administered subcutaneously. On the subsequent 1 to 4 days, maropitant or placebo (dependent on allocation) was administered subcutaneously or orally at approximate 24-h intervals as needed. Oral doses were administered as maropitant tablets using unit dosing to deliver a minimum dose of 2 mg/kg body weight (0.9 mg/lb) or equivalent numbers of similar placebo tablets. Dogs and housing were observed twice daily for evidence of vomiting. Emesis was significantly (P

World association for the advancement of veterinary parasitology (WAAVP): second edition of guidelines for evaluating the efficacy of anthelmintics in swine.

Guidelines are provided for evaluating the efficacy of anthelmintics in swine which, in conjunction with other sets of guidance such as those of the International Cooperation on Harmonization of Technical Requirements for Registration of Veterinary Medicinal Products (VICH GL7 and VICH GL16), should encourage the adoption of uniform registration requirements globally. Testing of efficacy should be carried out according to the principles of "Good Clinical Practice" (VICH GL9, 2000). Data obtained according to these guidelines should be internationally acceptable for the registration of anthelmintics for swine. Further, the use of the guidelines should expedite development, government review, and approval of anthelmintics for swine, as well as contribute towards reducing costs and the number of experimental animals used for drug testing.

Kinetics of expulsion of Haemonchus contortus from sheep and jirds after treatment with closantel.

Experiments were conducted in sheep after intramuscular treatment with closantel and in jirds after oral treatment with closantel to determine when expulsion of established H. contortus commences. Expulsion starts at about 8 h in sheep and coincides with the onset of reduced motility in worms recovered from the abomasum. In jirds, expulsion starts by 2 h after treatment. Experiments also conducted in jirds showed that infective larvae are first killed by circulating closantel 3 days after infection, when blood feeding starts, and that by 8 days 80% of larvae are lost.

Enhanced larval cyst growth of Echinococcus multilocularis in praziquantel-treated jirds (Meriones unguiculatus).

Jirds (Meriones unguiculatus) inoculated intraperitoneally with cystic material of Echinococcus multilocularis were given daily oral treatments of praziquantel at 300 mg/kg of body weight (bw) or dimethyl sulfoxide vehicle for five-day treatment regimens starting at 29 days postinoculation (PI) up to 69 days PI. At 39 or 49 days PI, the growth of the larval cystic mass (LCM) in jirds following a single or two five-day treatment regimens was significantly enhanced (P < 0.05) by 129.0% (2.3-fold) or 102.9% (2.0-fold), respectively. At 59 or 69 days PI following three or four five-day treatments with praziquantel, LCM growth was enhanced by 47.8% (1.5-fold) and 44.1% (1.4-fold), respectively, but was no longer significantly different than that in control jirds. A single five-day treatment on 29-33 days PI (with necropsy at 69 days PI) significantly enhanced the growth of the LCM by 87.6% (1.9-fold). Parasites from praziquantel treatment regimens examined ultrastructurally showed consistent damage to the germinal membrane evidenced by vacuolization and rupture of syncytial cytoplasm, rupture and coalescence of the electron-lucent vesicles just below the microvilli of the tegumental surface, and swelling and rounding of mitochondria. At 39 days PI, increased blebbing of the germinal membrane into the lumen of the LCM in praziquantel-treated animals was observed by scanning electron microscopy. The treatment-induced blebs were identified as nucleated germinal cells by transmission electron microscopy and appeared to be responsible for metastasis and enhanced growth of the LCM. Although praziquantel damaged the ultrastructural integrity of the LCM, treatment failed to inhibit larval cyst growth or protoscolex development.(ABSTRACT TRUNCATED AT 250 WORDS)

Anthelmintic activity of dioxapyrrolomycin.

Dioxapyrrolomycin, pyrrolomycin C, pyrrolomycin D, and piericidin C2 produced by UC 11065 were evaluated as anthelmintics. Assays used to examine these compounds included effects on the free-living nematode Caenorhabditis elegans, ability to clear target nematodes (Haemonchus contortus and Trichostrongylus colubriformis) from jirds, and clearance of Haemonchus contortus from lambs. A crude extract of UC 11065 containing dioxapyrrolomycin, pyrrolomycin C, pyrrolomycin D, and piericidin C2 was active against C. elegans and against H. contortus in the jird. Purified and/or synthetic samples of dioxapyrrolomycin, pyrrolomycin C, pyrrolomycin D, and piericidin C2 were tested in the jird model; only dioxapyrrolomycin exhibited appreciable activity against H. contortus (greater than or equal to 90.9% clearance at 0.33 mg/jird), while none of the compounds showed appreciable activity against T. colubriformis. Dioxapyrrolomycin cleared 99.9% of H. contortus from lambs at 12.5 mg/kg. An in vitro migration study using susceptible and closantel-resistant H. contortus showed there is cross-resistance between dioxapyrrolomycin and closantel. Dioxapyrrolomycin appears to be a narrow-spectrum anthelmintic which works through a closantel-like mode-of-action.

Anthelmintic profile of the cyclodepsipeptide PF1022A in in vitro and in vivo models.

A novel cyclodepsipeptide of fungal origin, PF1022A, recently was reported to have anthelmintic activity. To supplement published reports and determine potential utility of PF1022A as a ruminant anthelmintic, the compound was examined in in vitro and in vivo models. Assays used measured motility of Haemonchus contortus (intrinsic drug potency), ATP levels (parasite death), and activity against H. contortus, Ostertagia ostertagi, and Trichostrongylus colubriformis in the jird (spectrum, potency, and efficacy by various routes). The potency of PF1022A in reducing motility is greater than commercial anthelmintics. Examination of ATP levels in PF1022A-paralyzed H. contortus indicates that worms are not killed, suggesting the compound acts as a neurotoxin in nematodes. In the jird, PF1022A has activity orally against each of the parasites studied and at doses comparable to all commercial anthelmintics, except the macrocyclic lactones which are more potent. Unfortunately, for some nematode species, parenteral delivery is ineffective at realistic doses.

Anticoccidial evaluation of halofuginone, lasalocid, maduramicin, monensin and salinomycin.

The activities of five anticoccidials were compared against Eimeria species in/of chickens, in controlled in vivo and in vitro laboratory studies. Two more recent and potent market entries (maduramicin and halofuginone) were compared with three older polyether antibiotic anticoccidials (monensin, lasalocid and salinomycin). Halofuginone, lasalocid, maduramicin, monensin and salinomycin were evaluated at 3, 125, 5, 120 and 66 ppm, respectively, of active drug in the diets. At these levels, all five drugs demonstrated significant activity against Eimeria tenella, E. maxima, E. necatrix, E. brunetti and E. acervulina (in vivo). Monensin was least effective against E. tenella, and one of the lesser efficacious drugs against E. necatrix, maduramicin, was least effective against E. maxima. In studies of single Eimeria species infections, comparable weight gains were noted for the drugs. In the mixed Eimeria species infections, however, birds treated with maduramicin had significantly higher weight gains than did birds medicated with monensin. Unlike in vivo potencies, titration in vitro indicated that monensin was most potent (active at 10(-6) mcg ml-1), and maduramicin and lasalocid least potent (inactive at less than or equal to 10(-3) mcg ml-1).

Precluding coccidiosis with an anti-coprophagia drug.

Floor-pen studies were conducted to ascertain whether coccidiosis could be prevented by using a drug added to the litter to preclude coprophagia and ingestion of infective oocysts. An experimental drug (1-pyrrolidinebutyramide, 2-methyl-alpha,alpha-diphenyl) was added to litter contaminated with sporulated Eimeria tenella oocysts. Thereafter 7-day-old broiler chicks were reared on the litter for a nine-day period. Mortality, lesion scores and dropping scores were the criteria selected to determine efficacy. Treatment of the litter at the lowest level (2.3 g kg-1) did not reduce the incidence or severity of the disease, whereas treatment at two higher levels (11.5 and 23.0 g kg-1) significantly reduced both (incidence and severity). The highest level was the most efficacious; however, drug toxicity was also encountered at this level.

Anti-coccidial activity of human milk.

Sporozoites of Eimeria tenella, an important pathogen of poultry, were killed in vitro in a time- and concentration-dependent manner by exposure to diluted concentrations of normal human milk. Sodium cholate (bile salt stimulator) potentiated the anti-coccidial activity. The anti-coccidial activity was not found in the milk of lower mammals (cow, sheep, goat, dog). The component in human milk showing the activity was initially hypothesized to be a bile salt-stimulated lipase. However, testing of purified lipase (with or without sodium cholate) indicated no anti-coccidial activity. Consequently, we theorize that the active component may be a free fatty acid.

Detecting in vitro anthelmintic effects with a micromotility meter.

An in vitro target parasite anthelmintic assay utilizing a micromotility meter has been developed and validated. Haemonchus contortus, an economically important ruminant helminth with worldwide distribution, was the parasite used in the model. Four commercially available ruminant anthelmintics (albendazole, ivermectin, levamisole hydrochloride and coumaphos) were initially evaluated at concentrations of 200, 150, 100 and 50 micrograms ml-1. All four significantly affected helminth motor activity and were active at 200 and 150 micrograms ml-1, and three of the four were active at 100 and 50 micrograms ml-1. An Upjohn compound (p-toluoyl chloride phenylhydrazone) was also assayed and was significantly active at all four levels. In a subsequent titration study, albendazole, levamisole hydrochloride, ivermectin and the hydrazone were significantly active at 100 and 10 micrograms ml-1; only levamisole hydrochloride and the hydrazone were active at 1.0 microgram ml-1. None of the drugs were active at 0.1 microgram ml-1. The data indicate that the in vitro H. contortus assay utilizing the micromotility meter is sensitive, accurate, rapid, repeatable, and inexpensive. With additional effort, this model can be extended to incorporate other target helminth parasites and stages of development. This in vitro assay system should be a valuable addition to the battery of tests used to identify anthelmintic candidates, monitor drug resistance, and define the kinetics and mode of action of drugs.

Field efficacy of doramectin pour-on against naturally-acquired, gastrointestinal nematodes of cattle in North America.

Seven studies were conducted under field conditions in North America to evaluate the therapeutic efficacy of doramectin in a pour-on formulation at a dosage of 500 microg/kg (1 ml/10 kg) for cattle harboring naturally-acquired infections of gastrointestinal nematodes, including species of Haemonchus, Ostertagia, Trichostrongylus, Bunostomum, Cooperia, and Oesophagostomum. In each study, 40 to 100 cattle were randomly allocated to a saline- or doramectin-treated group in a tiered manner based on Day -7 bodyweight. On Day 0, the cattle received either saline or doramectin topically, according to their treatment group. Weather and safety observations were made following treatment. No adverse reaction to treatment was observed at any time during these studies. Fecal egg count (FEC) determinations were carried out on each animal on Days -7, 0, 7, 14, and 21. Reductions in FEC for the doramectin-treated animals compared to saline-treated cattle were > or = 96.0% by Day -7 and > or = 99.0% on Days 14 and 21 for each study. Across all studies regardless of weather conditions, the reduction by Day 21 for the doramectin-treated animals compared to saline controls was 99.7% (p < or = 0.0001) and compared to pretreatment levels in doramectin-treated cattle was 99.9% (p < or = 0.0001). Doramectin pour-on should provide a useful new treatment for controlling nematode parasites of cattle.

Persistent efficacy of doramectin pour-on against artificially induced infections of nematodes in cattle.

Two studies were conducted to determine the persistent efficacy of doramectin pour-on against an artificial, trickle challenge of mixed nematodes in calves. In each study, 42, 4-8 months old calves were randomly assigned into four groups of 10 animals each (T1-T4), plus two larval-viability monitor animals. All animals were treated with fenbendazole (10 mg kg(-1)) 14 days prior to the start of the study to clear any existing infection. Doramectin pour-on at 500 microg kg(-1) was used on each animal in Groups T2, T3, and T4 with intervals of 1 week (Day 0, 7, and 14, respectively). Calves in Group T1 were treated with saline solution on Day 0 and at the same volumetric rate (1 ml 10 kg(-1)) as the doramectin treated animals. All treatments were applied in a single passage along the midline of the back, from the withers to the tailhead. Subsequently, trickle inoculations with infective larvae were administered to all calves for 22 consecutive days (Days 14-35). Doramectin pour-on provided > or = 91.9% efficacy against challenge with Dictyocaulus viviparus, Haemonchus spp., and Ostertagia ostertagi for up to 35 days post-treatment and against challenge with Cooperia oncophora, Cooperia punctata, and Oesophagostomum radiatum for up to 28 days post-treatment.

Persistent efficacy of doramectin against experimental challenge with Ostertagia ostertagi in cattle.

Two studies were conducted in North America to evaluate the persistent efficacy of doramectin injectable solution against experimental challenge with infective larvae of Ostertagia ostertagi. In both studies, four groups of 10 randomly-assigned calves, negative for trichostrongyle-type eggs on fecal examination, were treated subcutaneously in the midline of the neck with saline (1 ml 50 kg-1) on Day 0 or doramectin (200 micrograms kg-1 = 1 ml 50 kg-1) on Day 0, 7, or 14. Two additional calves from the same pool of animals were randomly assigned as larval-viability monitors and received no treatment. Beginning on Day 14 and continuing through Day 28, the 40 treated calves each were given approximately 1000 infective larvae of O. ostertagi by gavage daily; the two larval-viability monitors were inoculated in a similar manner with approximately 30,000 larvae as a single dose on Day 28. Animals were slaughtered on Day 42 in one study and on Days 42, 43, or 46 in the second. The abomasum from each calf was harvested and processed for worm recovery. A 2% aliquot of abomasal contents plus wash was examined for worm quantification and identification. Geometric mean O. ostertagi burdens were calculated from the log (O. ostertagi count + 1) and were used to estimate percentage reduction. In both studies, doramectin injectable solution was > or = 99.6% efficacious in reducing infection resulting from challenge with infective larvae of O. ostertagi for at least 21 days posttreatment; by 28 days posttreatment, efficacy was 87.3% in one study and 99.7% in the other.

Persistent efficacy of doramectin injectable against artificially induced infections with Cooperia punctata and Dictyocaulus viviparus in cattle.

Three studies were conducted to evaluate the persistent efficacy of doramectin injectable solution against experimental challenges with infective larvae of Cooperia punctata and Dictyocaulus viviparus. In each study, four groups of ten randomly-assigned calves, negative for trichostrongyle-type eggs on fecal examination, were treated subcutaneously in the midline of the neck with saline (1 ml/50 kg) on Day 0 or doramectin (200 microg/kg = 1 ml/50 kg) on Day 0, 7, or 14. Two additional calves from the same pool of animals were randomly assigned as larval-viability monitors and received no treatment. On Days 14-28, approximately 1000 and 50 infective larvae of Cooperia spp. and D. viviparus, respectively, were administered daily by gavage to each animal in Groups T1-T4. On Day 28, the two larval-viability monitor calves were inoculated in a similar manner with a single dose of approximately 30000 and 2000 larvae of Cooperia spp. and D. viviparus, respectively. Equal numbers of calves from each treatment group were killed on Days 42-45, as well as the two viability monitor animals to enumerate worm numbers. A 2% or 5% aliquot of small intestinal contents and washings were examined for worm quantification and identification, while 100% of the lung recoveries were quantified and identified. For each study and across the three studies, geometric mean worm recoveries for each treatment group were calculated from the natural log transformed data (worm count + 1) and were used to estimate percentage reduction. In the three studies, doramectin injectable solution was 97.5% efficacious against lungworms for up to 28 days and was 99.8% efficacious in reducing infection resulting from challenge with infective larvae of C. punctata for at least 28 days post-treatment.

The microwave oven: a novel means of decontaminating parasitological specimens and glassware.

This study was conducted to determine the effects of microwave radiation on developmental and infective stages of Eimeria nieschulzi, Strongyloides ratti, and Taenia taeniaeformis. Fecal samples and laboratory preparations containing these three parasites were subjected to microwave radiation for brief periods in a microwave oven, and then in vitro and/or in vivo assessments of viability were made for each organism and preparation. Our results showed that microwave irradiation is extremely effective in killing or preventing development of helminth and protozoan parasites without unduly distorting eggs or developmental stages. Therefore, microwaves may prove useful for decontaminating diagnostic samples or sterilizing contaminated materials in the laboratory and thus for reducing risk to laboratory personnel from parasites of public health importance.

The immunizing potential of sporulated oocysts of Eimeria nieschulzi exposed to heat and Co-60 gamma-radiation.

Sporulated oocysts of Eimeria nieschulzi Dieben 1924, a rat coccidium, were exposed to radiation, heat, or both in an effort to attenuate the parasite. Moderate levels of each treatment or combination thereof attenuated the parasite, reduced pathogenesis (as judged by oocyst discharge during primary infection), and produced immunity to challenge when the oocysts were subsequently inoculated into rats. Thus, heat- and/or radiation-treated E. nieschulzi oocysts fed to rats could reduce pathogenesis during a primary infection and yet give good homologous protection.

Viability of infective larvae of Haemonchus contortus, Ostertagia ostertagi, and Trichostrongylus colubriformis following exsheathment by various techniques.

Various techniques were examined to determine optimum conditions for exsheathing infective larvae of 3 important ruminant parasites (Haemonchus contortus, Ostertagia ostertagi, and Trichostrongylus colubriformis). In repeated experiments, aliquots of 10(5)-10(6) infective larvae, 1-2 mo old, of each parasite were incubated in each of 4 exsheathing media (distilled water, Earle's balanced salt solution + carbon dioxide, nematode washing buffer + carbon dioxide, or sodium hypochlorite) for 1 or 18 hr. In each case, the percentage of larvae exsheathed and infectivity for jirds was determined. Results of these studies indicate that no single exsheathing technique of those studied is optimum for every parasite. In addition, caution must be used in drawing conclusions from in vitro studies using exsheathed larvae because techniques that routinely provide high percentages of exsheathment also appear to reduce viability.

Infectivity of Hymenolepis diminuta for the jird, Meriones unguiculatus, and utility of this model for anthelmintic studies.

The jird (Meriones unguiculatus) has been shown to be a useful model host for the cestodes Taenia crassiceps and Echinococcus multilocularis. This report outlines a novel model in which hydrocortisone-treated jirds (0.02% in the feed) are infected with another cestode, Hymenolepis diminuta. Jirds were inoculated with 5 freshly harvested cysticercoids of H. diminuta prior to (day 0, -1, or -5) or after (day 1 or 5) switching to medicated feed; in some cases, jirds were never medicated. On days 7, 14, 21, or 28 postinoculation (PI), jirds were killed by CO2 inhalation and their small intestines were examined for tapeworms. Hymenolepis diminuta established, grew, and developed to the gravid adult state in jirds. They persisted longer in medicated (21 days) than in nonmedicated (7 days) animals, and generally higher levels of infection were obtained when jirds were inoculated immediately prior to switching to medicated feed. Treatment of infected jirds on day 4 or days 4, 5, and 6 PI with selected anthelmintics followed by necropsy on day 7 PI discriminated drugs with known activity against tapeworms from those with little or no activity. This rodent in vivo model should provide a useful adjunct for anthelmintic studies.