Flea (Ctenocephalides felis) control efficacy of topical indoxacarb on dogs subsequently bathed with a chlorhexidine-ketoconazole shampoo.

OBJECTIVE: An evaluation of the effect of chlorhexidine/ketoconazole shampoo baths on the flea control efficacy of indoxacarb applied topically to dogs. METHODS AND RESULTS: We randomly allocated 18 healthy mixed-breed dogs to 3 groups: shampoo only; indoxacarb treated and medicated shampoo; and indoxacarb treated but not shampooed. Indoxacarb was administered on day 0 and dogs were shampooed on days 9 and 23. Dogs were infested with 100 adult Ctenocephalides felis initially 2 days before treatment and then weekly from days 7 to 28. Fleas were removed and counted 48 h post-infestation. CONCLUSION: Medicated shampoo use did not significantly reduce indoxacarb efficacy against C. felis.

Dose confirmation of moxidectin pour-on against natural nematode infections in lactating dairy cows.

The nematocidal effectiveness of moxidectin, administered topically at the rate of 500 mcg/kg BW, was determined for lactating dairy cows. Naturally infected animals were given either topical vehicle or moxidectin (Cydectin Pour-On Fort Dodge Animal Health) at the rate of 1 ml/10 kg BW (10 animals per treatment group), and sacrificed 14-18 days post-treatment for nematode enumeration. 100% efficacies were recorded for Ostertagia lyrata males, Cooperia punctata males and Oesophagostomum radiatum L4, with treatment group differences in geometric means significant (P < 0.05) for all. Populations of Trichostrongylus L4 and adult O. radiatum were also reduced by 100%, but low prevalence rates in the control animals precluded meaningful statistical inference. Nematode populations for which efficacies ranged from 96.7 to 99.6% (based on geometric means) and for which treatment group differences were significant (P < 0.05) included Ostertagia spp. adult females, inhibited L4 and developing L4, O. ostertagi adult males, Trichostrongylus axei adults and Cooperia spp. adult females. For all nematodes combined, moxidectin was 98.9% efficacious. In addition to exhibiting excellent nematocidal effectiveness, topical moxidectin was demonstrated to be safe, with animal health and milk production unaffected during the study.

A comparison of persistent anthelmintic efficacy of topical formulations of doramectin, ivermectin, eprinomectin and moxidectin against naturally acquired nematode infections of beef calves.

Persistent anthelmintic efficacy of topical formulations (all at a dosage of 500 microg/kg) of doramectin (DOR), ivermectin (IVM), eprinomectin (EPR) and moxidectin (MOX), in comparison with untreated control cattle (CONT), was observed in stocker beef calves during a 112-day winter-spring grazing trial. Five groups of 15 calves per group were grazed on 15 separate 2 ha pastures following random assignment of animals to specific pastures and then to treatment groups. All of the 5 treatments were represented in each of the 15 pastures. All cattle were weighed on study Days 1, 0, 28, 56, 84, 111 and 112. Fecal samples for nematode egg counts were collected on Days 7, 0, at 7 day intervals through Day 56 and at 14 day intervals to Day 1 12. Pooled group fecal cultures for determining generic composition of nematode infections were prepared at 14 day intervals throughout the study. As based on fecal egg counts, anthelmintic activity of EPR and MOX was greater (p < 0.05) than values for IVM or CONT through Day 28. Activity of DOR was greater (p < 0.05) than that of IVM on Days 7 and 14 only. Although significance levels varied little among treated groups from Day 42 to the end of the study, egg counts and percent reduction values of EPR and MOX remained consistently lower numerically than egg counts and higher than reduction values respectively, of DOR and IVM through Day 70. From Day 70 on, IVM counts were numerically, but not significantly higher than values of CONT. Based on larval culture, Cooperia predominated from Day 0 through 28 and again from Days 70 to 98; Ostertagia was second in prevalence with highest percentages, which exceeded those of Cooperia, between Days 42 and 70. Bodyweights of all treated groups, with exception of IVM, were always significantly greater (p < 0.05) than weights of CONT. Weights of IVM were numerically greater, but not significantly greater than CONT only on Days 84 and 112. From Day 56 on, there were no significant differences between weights of DOR, EPR and MOX, however, numerical values for MOX were consistently higher than values for the other two. Final average total bodyweight gains were: 153.7 kg for MOX, 148.5 kg for EPR, 146.9 kg for DOR, 139.7 kg for IVM and 127.7 kg for CONT.

Persistent efficacy: importance and impact of trial design.

The persistent efficacy of some anthelmintics brings advantages in nematode control in domestic animals. However, scientific assessment of persistent efficacy is relatively new, and a feature of published data has been variability in the reported endpoint for this activity. Trial design and method of calculating efficacy have a large bearing on the results obtained. Three types of studies used to evaluate the persistent efficacy of anthelmintics are briefly discussed and compared. In the first type of study, animals are treated followed by a single infection at 7, 14 or more days after treatment. The reduction in worm counts compared to an untreated control group gives a good indication of the persistent efficacy of the product at each time point. One control group can be used for several time points. In the second type of study, the animals are treated and then infected daily from day 1 until 7 days, 14 days or longer after treatment. The animals are slaughtered approximately 3 weeks after the last infection. This approach may better mimic a natural infection but the results obtained are an average reduction over the whole infection period. At the end of the evaluated period, the actual protection may be considerably lower than the average. From this test, it is difficult to define when the protection decreases or disappears. In this test, a control group is required for each period. In the third type of study, a modification of the second, the animals are treated and infected as before but animals are slaughtered soon (2-5 days) after the last infection. Based on the reduction of, for example, the different Ostertagia stages a more specific determination of the persistent efficacy 0-3 days (L3), 3-7 (EL4), 7-14 (LL4 + EL5) and more than 14 days (LL5 + adults) before slaughter can be obtained. Only two groups of animals are required to cover a 3 week period and the average efficacies can be reduced to about one week.

Efficacy of moxidectin 0.5% pour-on against naturally acquired nematode infections in cattle.

The efficacy of 0.5% moxidectin pour-on at two dosages was evaluated in 30 cattle with naturally acquired gastrointestinal nematode infections. The cattle were ranked according to pretreatment fecal egg counts and body weights, and were randomly assigned from replicates to three treatment groups. The mean number of trichostrongyle eggs in pretreatment fecal samples did not differ among the groups. Groups I and II received 0.5% moxidectin pour-on at dosages of 0.25 mg moxidectin per kg body weight and 0.5 mg moxidectin per kg body weight, respectively, and Group III cattle received moxidectin-free vehicle (control cattle). The cattle were euthanized by complete replicate 14 or 15 days posttreatment for recovery of nematodes and examination of the pour-on sites. Treatment with moxidectin was associated with a significant reduction in fecal trichostrongyle egg counts compared with the control cattle; efficacy was 99.7% and > 99.9% for cattle in Groups I and II, respectively. Eleven species of adult nematodes (Haemonchus contortus, Haemonchus placei, Ostertagia ostertagi, Trichostrongylus axei, Trichostrongylus colubriformis, Bunostomum phlebotomum, Cooperia oncophora, Cooperia punctata, Nematodirus helvetianus, Oesophagostomum radiatum and Trichuris ovis) and 4th stage larvae of Ostertagia spp. and Trichostrongylus spp. were present in sufficient numbers in control cattle to evaluate the efficacy of moxidectin 0.5% pour-on. In all cases, treatment was associated with a significant reduction in the number of nematodes recovered at necropsy, with the efficacy of both dosages exceeding 99.9%. There were no significant differences in mean worm burdens or fecal egg counts between the two treated groups, and no adverse reactions were observed.

The effects of abomasal casein infusions in growing beef steers on portal and hepatic flux of pancreatic hormones and arterial concentrations of somatomedin-C.

The net release of insulin, glucagon and somatostatin by the portal-drained viscera (PDV) and their net uptake by the liver in response to 3-d abomasal infusions of casein were measured in seven multicatheterized beef steers. The steers were fed 4.3 kg DM/d of a high-concentrate diet in 12 equal meals (13.1 Mcal ME/d and 95 g N/d). In two separate experiments, the abomasal infusion of 300 g casein/d (300C) or 150 g casein/d (150C) was compared to a water infusion. Plasma flow was measured by indicator dilution and net flux by venoarterial concentration difference x plasma flow. Arterial plasma concentrations of insulin were increased (P less than .02) by either 300C or 150C. The 300C increased (P less than .03) PDV insulin release but did not affect hepatic uptake, resulting in an increased (P less than .03) total splanchnic (TSP) insulin flux. The 300C increased (P less than .05) plasma concentrations of glucagon as the result of decreased (P less than .06) hepatic extraction ratio and not as the result of increased portal release. The portal and hepatic flux of somatostatin measured as somatostatin-like immunoreactivity (SLI) were highly variable and not affected by casein infusions. Arterial plasma concentrations of somatomedin-C were not responsive to abomasal casein infusions. The abomasal infusion of 300C resulted in increased plasma concentrations of insulin via increased PDV release and increased plasma glucagon via decreased hepatic extraction ratio.

The net portal and hepatic flux of metabolites and oxygen consumption in growing beef steers given postruminal casein.

Changes in net portal and hepatic nutrient flux and oxygen consumption in response to 3-d abomasal casein infusions were studied in seven multicatheterized beef steers. Steers were fed 4.3 kg DM/d of a high-concentrate diet in 12 equal meals. Blood flow (para-aminohippurate dilution) and net flux (venoarterial concentration difference x blood flow) across portal-drained viscera (PDV) and hepatic tissues were measured on d 3 of the abomasal infusions. In two experiments, the response to 300 (300C) and 150 (150C) g casein/d were compared, respectively, to a control water infusion. The 300C increased (P less than .05) arterial blood concentrations of alpha-amino N (AAN), urea N and ammonia; 150C increased (P less than .05) arterial urea N. Urinary urea N excretion was increased (P less than .01) by 300C and 150C. Although 300C increased net PDV release of AAN (P less than .07) and alanine (P less than .10), there was no net change in total splanchnic (TSP) flux due to an increased net hepatic uptake of AAN (P less than .01) and alanine (P less than .05). Net PDV glucose flux was decreased (P less than .05) by 300C, but net hepatic glucose flux was not affected by either level of casein. The 150C increased TSP oxygen consumption (P less than .05) and hepatic oxygen extraction (P less than .10). Approximately 26 and 30% of the casein N infused abomasally appeared in the portal blood as AAN for 150C and 300C, respectively. The sum of net PDV ammonia and AAN fluxes accounted for 47 and 88% of the N infused for 150C and 300C, respectively. These data emphasize the importance of intestinal and liver tissues in regulating the flux of nitrogenous compounds absorbed from the diet.

Methionine and lysine uptake by cattle small intestine in vitro.

Incubations of bovine intestinal mucosa were characterized for location of maximal uptake of amino acid, steady-state accumulation time of the amino acids, methionine and lysine. Photomicrographs validated that cattle intestinal mucosa was isolated by the technique described. Methionine and lysine uptake was expressed as micromoles of amino acid per milliliter of cell water. The most active site of methionine and lysine uptake was the mid-ileum, while the proximal jejunum was the least active site. Both methionine and lysine uptake showed high correlation relative to intestinal region. Methionine uptake was shown to be saturated with concentrations greater than 1 mM. Lysine transport appeared to be approaching saturation at concentrations between .5 mM to 1 mM, revealing that cattle intestinal mucosa has a lower transport capacity for lysine than methionine. These results indicate the usefulness of a technique through which substrate uptake (amino acid, carbohydrate, etc.) can be characterized in cattle small intestine.

Identification of methionine and lysine transport systems in cattle small intestine.

Incubations of bovine ileal mucosa were used to identify the amino acid transport systems responsible for methionine and lysine uptake in cattle small intestine. Uptake was expressed as micromole per milliliter of cell water. Lysine uptake was shown to be sodium (Na) independent. Specific transport components of lysine uptake were estimated to be: 63% occurring through the cationic (Y+) system, 17% via the neutral alanine (A) and alanine, serine, cysteine (ASC) amino acid transport systems, and 20% through nonsaturable processes. Physiological concentrations of competitive inhibitors altered (P less than .05) lysine uptake. Methionine uptake was shown to occur by both Na-independent and Na-dependent transport systems. The specific transport components of methionine uptake were estimated as 54% occurring through the neutral branched chain leucine (L) systems, 28% through the ASC system, 15% through the A system and 25% through nonsaturable processes. Physiological concentrations of competitive inhibitors did not inhibit (P greater than .05) methionine uptake.