Efficacy of oxfendazole against inhibited larvae of Ostertagia ostertagi acquired by calves in the spring

During the spring of 1985, 40 calves grazed pastures known to have high numbers of spring inhibition-prone, infective Ostertagia ostertagi larvae. Calves were removed from pasture and placed in outdoor pens with concrete floors from 10 days prior to treatment until necropsy 14 days after treatment. Ten calves were allocated to each of 4 treatment groups, and oxfendazole was administered to each group by intraruminal injection at dosages of 0, 2.25, 4.5, and 6.75 mg/kg of body weight. Efficacies greater than or equal to 94.6% were achieved at dosages of 4.5 and 6.75 mg/kg against adult Ostertagia spp, Trichostrongylus spp, Haemonchus placei, Cooperia punctata, Bunostomum phlebotomum, Oesophagostomum radiatum, and Dictyocaulus viviparus. Efficacy against inhibited larvae of O ostertagi was variable, with the highest efficacy (90.2%) attained at a dosage of 6.75 mg/kg.     

Evaluation of lasalocid as a coccidiostat in calves: titration, efficacy, and comparison with monensin and decoquinate

Two experiments were conducted to evaluate lasalocid as a coccidiostat in Holstein calves and to compare lasalocid with monensin and decoquinate. In experiment 1, calves in 3 groups (6 calves/group) were each inoculated with 500,000 sporulated oocysts, 88% of which were Eimeria bovis and 12% were E zuernii. Calves in each group were given lasalocid-medicated feed at 0.50 (group 3), 0.75 (group 4), or 1 mg/kg (group 5) of body weight/day for 45 days. Two control groups (6 calves/group) were also evaluated; calves in control group 2 were inoculated and nontreated, and calves in control group 1 were noninoculated and nontreated. At 0.50, 0.75, or 1 mg/kg/day, lasalocid was equally effective in preventing induced coccidiosis (E bovis and E zuernii) in calves. Compared with inoculated nontreated controls, treated calves had significantly (P less than 0.05) fewer oocysts in feces and had fewer clinical signs of coccidiosis from days 16 to 30 after inoculation. Experiment 2 was conducted to compare the effectiveness of monensin, lasalocid, and decoquinate for the prevention of experimentally induced coccidiosis. Calves (n = 48) were allotted into 4 groups (12 calves/group); each was inoculated orally with 275,000 sporulated oocysts, predominantly E bovis and E zuernii, and each was given nonmedicated feed (group 6) or feed medicated with 33 mg of lasalocid (group 7), decoquinate (group 8), or monensin (group 9)/kg of feed for 46 days. Calves given medicated rations had significantly (P less than 0.05) fewer oocysts in their feces and fewer clinical signs of coccidiosis than did calves given nonmedicated rations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Anthelmintic activities of ivermectin against immature and adult Dictyocaulus viviparus

Eighteen calves about 3 months old were inoculated with 3,000 Dictyocaulus viviparus infective larvae. Three groups of 6 calves each were formed. Thirteen days after inoculations, 3 of the 6 group 1 control calves were given vehicle subcutaneously (SC) and the group 2 calves were given ivermectin at the dose rate of 200 micrograms/kg, SC. Thirty-five days after inoculation, the remaining 3 calves in group 1 were given vehicle SC and the group 3 calves were given ivermectin at the dose rate of 200 micrograms/kg, SC. Necropsies were performed 42 days after inoculations. A total of 474 D viviparus was recovered from the group 1 control calves, whereas none was recovered from the calves treated when the nematodes were in the 4th stage of development (group 2) or adult stage (group 3).     

Grazing study in Ireland using the morantel sustained release bolus for controlling nematodiasis in calves

The morantel sustained release bolus was administered at turnout to first-season grazing calves in order to assess its efficacy in the seasonal control of infection by nematode parasites in Ireland. The pastures grazed by control calves showed a marked increase in gastrointestinal trichostrongylid infective larvae by September, while numbers of infective larvae on pasture grazed by bolus-treated calves remained at a low level throughout the grazing season. In consequence, the controls showed significantly higher worm egg counts in late season and significantly higher worm burdens (mainly Ostertagia spp) at necropsy carried out in November on representative number of principal animals selected from each group. These reduced worm burdens were attributed to the suppression of egg output during the early part of the season as a result of treatment with the morantel sustained release bolus at turnout in the spring. Pasture contamination with Dictyocaulus viviparus larvae was present on all treatment pastures. The bolus-treated calves however were subjected to an increase in D. viviparus infection which occurred on their pasture in late season after the active life of the bolus had expired. It was concluded that bolus treatment delayed (rather than prevented) the buildup of D. viviparus infection on the pasture by 60-90 days.     

Efficacy of ivermectin and levamisole against immature Dictyocaulus viviparus in cattle

Eighteen calves aged approximately three months were each infected with Dictyocaulus viviparus larvae at a rate of 30/kg bodyweight. Seven days later they were randomly allocated to three groups of six animals. Calves of group 1 were controls. Calves of group 2 were given levamisole at a dose rate of 10 mg/kg and calves of group 3 were given ivermectin at a dose rate of 200 micrograms/kg. The anthelmintic activity of these two drugs was compared using clinical, functional, parasitological and pathological parameters. The results showed that the efficacy of ivermectin, given at a therapeutic dose, against immature D viviparus was higher than that of levamisole, given at double the recommended dose.     

Comparison of the persistent efficacy of the injectable and pour-on formulations of doramectin against artificially-induced infection with Dictyocaulus viviparus in cattle

The persistent efficacy of the injectable and topical formulations of doramectin was compared against experimental challenges with infective larvae of Dictyocaulus viviparus in two separate studies. Four groups of 10 randomly-assigned calves, negative for lungworm larvae by the Baermann technique, were used in each study. Calves were treated subcutaneously in the midline of the neck or poured down the midline of the back with saline (1 ml/50 kg. injection: 1 ml/10 kg. pour-on) on Day 0 or doramectin (200 microg/kg = 1 ml/50 kg. injection: 500 microg/kg = 1 ml/10 kg. pour-on) 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. Calves were inoculated daily with a gavage of approximately 100 larvae of D. viviparus from days 35 to 49 for the injectable study and days 28 to 42 for the pour-on study. The two larval viability monitor calves received approximately 3000 infective larvae in the same manner on Day 49 or 42 for the injectable and pour-on studies, respectively. Equal numbers of calves from each treatment group as well as the larval viability monitor calves were necropsied on days 14 and 15 after the last lungworm inoculation to enumerate the worm burden. The worms recovered were quantified and identified. For each study, geometric mean worm recoveries for each treatment group were back transformed from the natural log-transformed data (worm count +1) and were used to estimate percentage reduction. Doramectin injectable solution was 100.0% efficacious against lungworms for up to 49 days and the pour-on formulation was 100.0%, 93.1% and 81.5% effective in reducing lungworm infection resulting from challenge infection for up to 28, 35, and 42 days post-treatment, respectively.     

A comparison of interactions between vaccination against Dictyocaulus viviparus and anthelmintic suppression in immunised and unimmunised yearling cattle

Twenty parasite-naive calves aged approximately four months were divided randomly into four groups of five. Two groups were treated with oral lungworm vaccine. One immunised group plus another non-immunised group were put out to graze on May 1 on a pasture known to be contaminated with Dictyocaulus viviparus infective larvae during the previous autumn. All the calves both indoor and outdoor were treated with ivermectin at three, eight and 13 weeks after the first groups started to graze and again at housing at the end of September. After the winter housing period on April 27 of the following year all the calves were given an artificial challenge of D viviparus infective larvae at the rate of 15 larvae per kg bodyweight, and the clinical and parasitological reactions monitored. All the calves which had been vaccinated or exposed to field infection during year 1 reacted strongly in ELISAs using antigen prepared from fourth stage D viviparus larvae but much less strongly in similar tests using adult derived antigen. Clinically those calves exposed to previous field infections were less severely affected than the housed calves, although parasitologically all three groups with prior exposure to D viviparus appeared to have a similar functional level of immunity to the challenge infection in comparison to the unexposed calves of the same age.     

A comparison of the efficacy of four different long-acting boluses to prevent infections with Dictyocaulus viviparus in calves

A field study of calves in their first grazing season tested the efficacy of four long-acting devices--a morantel sustained-release bolus, a levamisole sustained-release bolus, an oxfendazole interval bolus, and an albendazole interval bolus--against Dictyocaulus viviparus. The pasture had been previously contaminated by four calves orally inoculated with infective lungworm larvae. The calves were grazed together with four bolus-treated groups, each comprising four calves. Lungworm infection became patent in the experimentally inoculated calves between 22 and 26 days. Infection in the bolus-treated groups became patent after 54 days. The morantel bolus group excreted the most larvae, followed by the albendazole bolus group, and the levamisole bolus group. The oxfendazole bolus group excreted by far the least larvae. Eosinophil curves and ELISA titres showed that treated groups had essentially the same course of infection. The heavy infection to which the treated calves were exposed produced complete immunity in all groups. Challenge infection of 10,000 larvae at housing did not change any of the test parameters. Post-mortem examination showed only one positive calf with few worms. We concluded that when pastures are heavily infested with lungworm larvae, all boluses prevent severe clinical signs and allow build up of solid immunity, although none completely prevent excretion of larvae.     

Ostertagia ostertagi in neonatal calves: establishment of infection in ruminating and non-ruminating calves

An experiment was carried out to study the role of the ruminal function in the establishment of Ostertagia ostertagi in neonatal calves. Three groups of calves were fed either milk only (groups A and C), or hay and concentrate in addition to milk (group B) from birth. At the time of infection, ruminal function was negligible in groups A and C, whereas it was well developed in group B. Calves of groups A and B were each given 25,000 normal ensheathed infective larvae of O ostertagi and those of group C were given 25,000 infective larvae exsheathed in vitro. Daily faecal egg output and post mortem worm counts 28 days after infection were higher in calves with well developed ruminal function than those having only negligible ruminal function. In the latter group, exsheathed larvae established at a lower rate than did ensheathed larvae. The results suggest that the degree of development of the ruminal function influences the establishment of O ostertagi.     

Prophylactic efficacy of an ivermectin sustained-release bolus against challenge exposure with gastrointestinal and pulmonary nematode infective larvae in calves

Twelve Holstein calves were used to determine the prophylactic efficacy of ivermectin against challenge exposure with gastrointestinal and pulmonary nematodes. Two groups of 6 calves (mean body weight, 205 kg) each were formed by restricted randomization according to body weight. Group-1 calves served as nonmedicated controls. Each calf of group 2 was orally given one prototype sustained-release bolus designed to deliver ivermectin at a continuous daily dose of 8 mg. Third-stage nematode infective larvae were given to the calves on posttreatment days 28 and 42. The calves were euthanatized 77 or 78 days after treatment. Ivermectin was 100% effective (P less than 0.05) in preventing the establishment of infection by Haemonchus placei, Ostertagia ostertagi, Cooperia spp (C punctata, C oncophora, C surnabada), Nematodirus helvetianus, Oesophagostomum radiatum, and Dictyocaulus viviparus and was greater than 99% effective against Trichostrongylus axei. Incidental infection by Trichuris spp was reduced by 94% (P = 0.08).     

Efficacy of salinomycin in treatment of experimental Eimeria bovis infections in calves

The efficacy of salinomycin for treatment of experimental Eimeria bovis infections was evaluated. In experiment 1, 18 calves were placed into four groups. Group 1 calves were nonmedicated controls; groups 2, 3, and 4 calves were given salinomycin (0.33, 0.66, and 1.00 mg/kg of body weight, respectively) in daily oral divided doses starting 2 or 3 days prior to E bovis inoculations and continuing until postinoculation day (PID) 21. Calves treated with 0.66 and 1.00 mg/kg (groups 3 and 4) passed substantially fewer oocysts than did control calves (group 1) or calves treated with 0.33 mg/kg (group 2). Group 1 control calves had typical signs of severe E bovis infections, whereas signs of infection in medicated calves were almost nonexistant. Experiment 2 was conducted as before, with 15 calves. Group 5 calves were nonmedicated controls; groups 6, 7, and 8 calves were treated with 0.5, 1.0, and 2.0 mg/kg, respectively. All group 8 calves and three of four group 7 calves had nearly complete suppression of oocyst excretions. The severity of the disease in the group 5 control calves was not as extensive as it was in group 1 control calves. In experiment 3, 16 calves were used. Group 9 calves were nonmedicated controls, whereas other calves were given salinomycin (2.0 mg/kg) during PID 3 to 7 (group 10), PID 8 to 12 (group 11), and PID 13 to 17 (group 12). Salinomycin therapy in group 2 calves resulted in substantial reductions in oocyst excretions and clinical signs.     

Comparison of the efficacy of dermal formulations of ivermectin and levamisole for the treatment and prevention of Dictyocaulus viviparus infection in cattle

Four groups of six parasite-naive calves were infected at seven day intervals with three doses of infective larvae of Dictyocaulus viviparus. Twenty-one days after the first dose three of the groups were treated either with an injectable formulation of ivermectin at a dose rate of 200 micrograms/kg bodyweight, or with pour-on preparations of levamisole at 10 mg/kg or ivermectin at 500 micrograms/kg. On day 28 two calves from each group were slaughtered and their burdens of lungworms counted. On day 35 the remaining calves were reinfected with D viviparus infective larvae at a rate of 80 L3/kg. The levamisole preparation was 94.6 per cent effective and both ivermectin preparations were 100 per cent effective against the initial infections. The ivermectin-treated calves were protected from the reinfection which subsequently became patent in the levamisole-treated and control calves.     

Effect of repeated doses of levamisole on grazing cattle infected with Dictyocaulus viviparus

Seventy-one worm-free Friesian calves were allocated by weight to three trial groups (1, 3 and 4) of 18 and a control group (2) of 17 animals. Calves in group 1 were vaccinated with a bovine lungworm oral vaccine on days 0 and 28, and on day 42 all groups were turned out to graze together on pasture known to be infected with Dictyocaulus viviparus larvae. Twenty-eight days after first exposure to infection one control calf died of parasitic bronchitis. Anthelmintic medication consisting of two doses of levamisole (7 . 5 mg/kg) at 14 day intervals was promptly administered to group 3 calves and three doses at the same intervals to group 4 calves. All calves were challenged with 20,000 infective D viviparus larvae on day 147. Calves were weighed every 14 days throughout the trial which ended 42 days after challenge. Pasture contamination and infectivity were monitored by pasture larval counts and tracer calves. Statistically there was no significant difference between the performances of treated and vaccinated groups before challenge but all were significantly superior to the control group. After challenge the productivity of all experimental groups was temporarily depressed but the levamisole treated cattle recovered more rapidly becoming significantly heavier than the vaccinates at the end of the trial. The mean group weight gains over the trial period were 89 . 92, 63 . 87, 88 . 67 and 98 . 70 kg in groups 1, 2, 3 and 4 respectively.     

Efficacy of ceftiofur for treatment of experimental salmonellosis in neonatal calves

OBJECTIVE: To evaluate therapeutic efficacy of a high extralabel dose of ceftiofur for treatment of experimental salmonellosis in neonatal calves. ANIMALS: Forty-two 1- to 4-day-old Holstein bull calves. PROCEDURE: 36 calves were orally challenged with Salmonella enteritica serovar Typhimurium (6.5 x 10(8) colony-forming units). Six additional calves were retained as nonmedicated nonchallenged control calves. Four days following Salmonella challenge, surviving calves were randomly allocated to ceftiofur-treated (5 mg/kg, IM, q 24 h) or nonmedicated control groups. Calves assigned to the treated group were medicated daily for 5 days starting on day 4 after challenge. Calves were monitored for 18 days following Salmonella challenge. Outcome assessments included clinical parameters (attitude, appetite, fecal characteristics, and rectal temperature), mortality rate, and quantitative Salmonella culture of fecal samples, mesenteric lymph nodes, and cecal contents. RESULTS: Ceftiofur treatment was associated with a significant decrease in rectal temperature and diarrhea. Three of 15 medicated calves and 4 of 14 non-medicated calves died or were euthanatized between days 4 and 18. A significant decrease in fecal shedding of Salmonella organisms was observed in treated calves, compared with nonmedicated calves. Salmonella organisms were isolated from all 10 non-medicated calves at necropsy, whereas no Salmonella organisms were isolated from 5 of 12 medicated calves. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment of salmonellosis in neonatal calves with a high extralabel dose of ceftiofur (5 mg/kg, IM, q 24 h) promotes animal welfare, reduces fecal shedding of Salmonella organisms, and may promote clearance of Salmonella infections when plasma ceftiofur concentrations are maintained above minimal inhibitory concentrations.     

The residual effect of treatment with ivermectin after experimental reinfection with nematodes in calves

The residual effect of treatment with ivermectin after experimental reinfection in calves was tested. Twenty-four calves were divided into 6 groups of 4 calves each. All calves received a primary infection of 50,000 larvae of both Ostertagia ostertagi and Cooperia oncophora and 1000 Dictyocaulus viviparus larvae. Calves of group 1 remained untreated, and all other calves were treated 21 days after primary infection (0.2 mg/kg injected subcutaneously). Calves of groups 1 and 2 were slaughtered 7 days later. Calves of groups 3-6 were reinfected with the same number of larvae 3 days, 1, 3 and 6 weeks after treatment respectively. Slaughter was 21 days after reinfection. Based on post-mortem worm counts the efficacy of ivermectin after primary infection was 99.7% for O. ostertagi, 95.1% for C. oncophora and 100% for D. viviparus. A residual effect was present for at least one week, but could not be observed 3 weeks after treatment.     

Anthelmintic activities of B1a fraction of avermectin against gastrointestinal nematodes in calves

Anthelmintic activities of the B1a fraction of avermectin were evaluated in a controlled experiment. Twenty 12-week-old calves artificially infected with gastrointestinal nematodes were allotted to four groups. Calves in group 1 were used as nonmedicated controls; other calves in groups 2, 3, and 4 were given (orally) B1a avermectin at dosage levels of 50, 100, and 200 microgram/kg of body weight, respectively. These treatments were given 35 days after calves were inoculated with infective nematode larvae. In groups 2, 3, and 4, overall reductions (based on geometric means) were 98.6%, 98.7%, and 98.4%, respectively. These reductions were highly significantly different (P less than 0.01) from the control calves. Nematodes in the calves were Haemonchus contortus. Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia oncophora, C punctata, and Oesophagostomum radiatum.     

Induction of protective immunity to Dictyocaulus viviparus in calves while under treatment with endectocides

Three groups of five parasite-naive calves were used. The treatments were: (a) Group 1 calves were weighed on Day 0 and injected with doramectin at 200 microg/kg. From Day 1 to 19 they were dosed orally with 2000 infective larvae of Dictyocaulus viviparus. On Day 28 they were again injected with doramectin, and infected with D. viviparus larvae from Days 33 to 41. They were then left untreated until Day 81 when they were infected with 20 infective larvae of D. viviparus per kg body weight. They were killed on Day 110 and lungworms were counted; (b) Group 2 calves were immunised with oral lungworm vaccine on Days 0 and 28, and infected and slaughtered as Group 1 on Days 81 and 110, respectively; (c) Group 3 calves acted as infection controls. Blood samples were taken at Days 0, 21, 49, 77 and 110 for antibody tests to D. viviparus. At autopsy there were no significant differences between the number of lungworms from Groups 1 and 2 (Means 17.4 and 31.3, respectively); Group 1 had significantly less value than Group 3 (Mean 228) (p < 0.05). Increased antibody titres to the larval sheath of the infective larvae were observed from Groups 1 and 2, showing that the larvae in Group 1 had penetrated the intestine before being killed by the circulating anthelmintic. This experiment shows that if calves are exposed to infective larvae while under systemic endectocide cover, an immune reaction is stimulated.     

Evaluation of lasalocid and decoquinate against coccidiosis resulting from natural exposure in weaned dairy calves

Eighteen female Holstein calves, raised as natural herd additions under conditions typical of a well-managed midwestern United States dairy farm, were used in a natural-exposure study to determine the anticoccidial efficacies of lasalocid and decoquinate. Calves were allotted to 6 treatment blocks of 3 calves each as they were weaned. Within each block, calves were randomly assigned to be given either lasalocid or decoquinate or to remain as a nonmedicated control. Calves were given medication for 90 days and remained separated from other calves for 120 days. Adjusted weight gains were consistently greater in calves that were given medication; however, differences were not statistically significant. Fecal specimens were obtained from calves at weekly intervals during the study. Overall, oocyst shedding was low. During the medication period, quantitative mean fecal shedding of oocysts was reduced eightfold in calves given decoquinate and four-fold in calves given lasalocid, as compared with nonmedicated control calves. During the period following the medication period, calves that had been controls shed fewer oocysts than did calves that had previously been given medication. A pairwise comparison of the proportion of specimens that were oocyst-positive was made to assess qualitative oocyst shedding among treatment groups. During the medication period, qualitative oocyst shedding (all species, Eimeria bovis, E zuernii, species other than E bovis and E zuernii) was greater in controls than in either lasalocid-or decoquinate-treated groups. Like-wise, lasalocid-medicated calves shed oocysts more frequently than did the decoquinate-medicated group. After medication, qualitative findings were reversed. Little diarrhea was noticed in treatment or control calves during the study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of intermittent and continuous administration of decoquinate on bovine coccidiosis in male calves

Male Holstein calves were each inoculated with 350,000 sporulated oocysts of Eimeria bovis. Two calves were given decoquinate (0.5 mg/kg of body weight) continuously in dry feed for 29 days, and 2 calves each were given 0.5, 1, or 1.5 mg of decoquinate/kg on an every 2nd-or 3rd-day schedule for 29 days. Calves given decoquinate continuously did not discharge oocysts but had slightly loose feces. In general, the number of oocysts discharged increased and fecal consistency decreased as the time between feeding of medicated feed increased. Calves given 0.5 or 1.5 mg of decoquinate/kg every 3rd day discharged more oocysts and had more diarrhea than did calves given 1 mg of decoquinate/kg every 3rd day. At postinoculation day 29, calves were euthanatized. At necropsy, intestinal tissues of calves given decoquinate were mostly normal. Apparently, reduced infections along with the elapsed time were sufficient to resolve most intestinal lesions caused by the coccidia. Decoquinate was most effective when fed continuously at 0.5 mg/kg. However, when fed at 1 or 1.5 mg of decoquinate/kg every 2nd day or 1.5 mg of decoquinate/kg every 3rd day, oocyst production was reduced and clinical coccidiosis was prevented.     

Comparison of vaccination and ivermectin treatment in the prevention of bovine lungworm

Three groups of calves were put out to graze on separate paddocks within a field known to be infected with Dictyocaulus viviparus and were also given a small initial trickle infection of the parasite. The first group were untreated controls, the second were immunised with live irradiated lungworm vaccine and the third were injected three times with ivermectin; the injections taking place after they had grazed for three, eight and 13 weeks. The subsequent infections of D viviparus were estimated by grazing a series of parasite-free tracer calves in the paddocks used by each group. The first group of such calves grazed from July 17 until August 7, the second from August 22 to September 29. During the first half of the grazing season all the untreated and three of the six immunised calves were observed to excrete D viviparus larvae, in contrast to none of the ivermectin-treated group. As a result all the tracer calves on the areas occupied by the untreated and immunised calves became infected with the parasite whereas only one worm was found in one of the 10 tracer calves grazing the area occupied by the ivermectin-treated calves.