Investigations into the prevention of neonatal Ancylostoma caninum infections in puppies by application of moxidectin to the bitch.

The aim of this investigation was to examine whether reactivated Ancylostoma caninum larvae can be eliminated by the administration of moxidectin to pregnant bitches. Four pregnant bitches infected experimentally with 20,000 third-stage larvae of A. caninum were treated subcutaneously with 1 mg moxidectin/kg body weight on day 55 of the pregnancy (5-8 days before parturition). Another four experimentally infected pregnant bitches served as controls. The single moxidectin treatment completely prevented lactogenic infections in the puppies. Neither intestinal stages nor somatic larvae could be found. The administration of moxidectin caused no local or systemic side-effects in the bitches. All 22 puppies of the treated bitches were born healthy and remained so during the whole trial period. Beginning during the third week after birth, all 20 puppies of the untreated bitches developed a severe microcytic, hypochromic anaemia and they revealed a total of 8649 intestinal stages of A. caninum after autopsy.     

Investigations into the prevention of neonatal Ancylostoma caninum infections in puppies by application of imidacloprid 10% plus moxidectin 2.5% topical solution to the pregnant dog

The aim of the investigation was to examine whether a single topical administration of a combination of imidacloprid and moxidectin to pregnant dogs could prevent neonatal infections with reactivated Ancylostoma caninum larvae. Three pregnant beagles, infected with A. caninum, were treated topically with the combination on day 56 of pregnancy. Three further dogs served as untreated controls. Treatment appeared to prevent neonatal infections in the puppies completely. Neither intestinal stages nor somatic larvae were found in two examined puppies per litter. All puppies and dams of the treatment group remained coproscopically negative. No side-effects in dams or puppies were observed. Two of three untreated dams showed a patent infection after parturition. Necropsy of two puppies of each negative control litter revealed seven intestinal and five somatic A. caninum stages in total. One litter of the untreated dams showed a patent infection 33 days after parturition. In the other two litters, no representative sample sizes could be collected.     

Investigations into the Prevention of Neonatal Ancylostoma caninum Infections in Puppies by Application of Moxidectin to the Bitch

The aim of this investigation was to examine whether reactivated Ancylostoma caninum larvae can be eliminated by the administration of moxidectin to pregnant bitches. Four pregnant bitches infected experimentally with 20 000 third-stage larvae of A. caninum were treated subcutaneously with 1 mg moxidectin/kg body weight on day 55 of the pregnancy (5–8 days before parturition). Another four experimentally infected pregnant bitches served as controls. The single moxidectin treatment completely prevented lactogenic infections in the puppies. Neither intestinal stages nor somatic larvae could be found. The administration of moxidectin caused no local or systemic side-effects in the bitches. All 22 puppies of the treated bitches were born healthy and remained so during the whole trial period. Beginning during the third week after birth, all 20 puppies of the untreated bitches developed a severe microcytic, hypochromic anaemia and they revealed a total of 8649 intestinal stages of A. caninum after autopsy.     

Biology, pathogenicity, diagnosis and control of Ancylostoma caninum]

Infections with Ancylostoma caninum are transmitted orally or percutaneously. The transmission of infectious stages with the milk of particular importance for the distribution of the species. It occurs during the dissemination of larvae that follows every infection as well as after reactivation of resting somatic larvae in the bitch at the end of the pregnancy. The galactogenic transmission of larvae occurs even when, due to existing immunity, no patent infections develop in the bitch. Immunity does not or only to a low extent influence impatient infections or the migration of reactivated somatic larvae. It also allows a limited reestablishment of a deposit of larvae in the bitch. Following percutaneous infection dermatitis occurs in the area of larval penetration and the lung is affected by migrating larvae. Intestinal stages of Ancylostoma caninum damage the host by ingestion of the mucosa of the small intestine and withdrawal of blood. Main symptoms of ancylostomiasis are a mucous haemorrhagic diarrhoea and anaemia, that become visible 8 to 10 days post infection. The examination for impatient infections with Ancylostoma caninum can be done by immunofluorescence and ELISA. With both methods antibodies against third stage larvae can be detected from the first or second week post infection onward. Patent infections with Ancylostoma caninum can easily be detected by faecal examination for the presence of the characteristic oval, thin-walled eggs containing few blastomeres. Galactogenic infections with Ancylostoma caninum can be prevented or reduced by a regular treatment of the bitch with albendazole, fenbendazole or oxfendazole during the activation of larvae in the last third of the pregnancy or by repeated treatment with ivermectin shortly before and after birth. To prevent patent infections, galactogenic infected puppies have to be treated early and repeatedly.     

Parasitologic, clinical, hematologic and serologic findings in puppies after lactogenic infection with Ancylostoma caninum ERCOLANI 1859 (Ancylostomidae)]

The correlation between intensity of Ancylostoma caninum infections in bitches and the intensity of lactogenic infections and clinical signs of their puppies was investigated. On average, 825, 1,867 or 2,125 specimens were observed in litters of two bitches inoculated with 5,000, 10,000 or 20,000 third stage larvae (LIII) respectively, at the day of conception. Adverse effects of the infection on the growth and behaviour of the puppies were observed after onset of their second week of life: 11/27 puppies died during the fourth week. The body weight of puppies surviving 28 days was up to 750 g less than that of uninfected controls. Eosinophilia, erythroblastosis and microcytic, hypochromic anemia developed in all puppies during their first four weeks. The IFA test (LIII antigen) was positive for only 5/18 heavily infected puppies after uptake of colostrum.     

Dose-titration studies of ivermectin against experimental Ancylostoma caninum and Uncinaria stenocephala infections

Dose-titration trials of ivermectin were conducted on pups with dual experimental infections of 4th-stage larvae or adult Ancylostoma caninum and Uncinaria stenocephala. Ivermectin was administered orally or subcutaneously at dosages of 0.006, 0.012, or 0.024 mg/kg of body weight. Maximal or near maximal (greater than or equal to 96% to 100%) anthelmintic effect was observed for both stages of development for each hookworm species by either route of administration at a dosage of 0.024 mg/kg. Responses for all of the aforementioned categories were linearly related to increasing log dosage of ivermectin, with common slopes (regression coefficients). Regression analysis also provided estimates of the minimal dosages required to produce maximal reduction in worm burden for each stage, species, and route of administration. The estimated ivermectin dosages for maximal efficacy ranged from a low of 0.014 mg/kg for adult A caninum by oral treatment to 0.044 mg/kg for 4th-stage larvae of U stenocephala by oral treatment.     

Investigations into the prevention of prenatal and lactogenic Toxocara canis infections in puppies by application of moxidectin to the pregnant dog

Aim of the investigation was to examine whether two administrations of moxidectin to pregnant dogs could prevent pre-natal and lactogenic infections of puppies with reactivated Toxocara canis larvae. Four pregnant beagles, infected experimentally with 20 000 embryonated eggs of T. canis, were treated subcutaneously with 1 mg moxidectin per kg body weight on days 40 and 55 of pregnancy (5-13 days before parturition). One further dam and its puppies served as untreated control. Two applications of moxidectin completely prevented pre-natal and lactogenic infections in the puppies. Neither intestinal stages nor somatic larvae were found in the dams or their corresponding puppies. All puppies and dams of the treatment group remained coproscopically negative until 42 days after parturition. The administration of moxidectin did not show any side effects in the dams. None of the puppies of the treated dams showed any pathological abnormalities. In the untreated dam one adult and 26 somatic larvae of T. canis were detected at necropsy. All puppies of the untreated dam showed a patent T. canis infection from day 28 post-natum (p.n.); 296 pre-adult and adult stages of T. canis were spontaneously eliminated and 51 intestinal stages and five somatic larvae of T. canis were recovered at necropsy. In contrast to the puppies of the treated dams all negative control puppies showed blood eosinophilia after parturition and elevated liver enzyme levels.     

Prenatal and transmammary infections of Toxocara canis in dogs: effect of benzimidazole-carbamate anthelmintics on various developmental stages of the parasite

Fenbendazole and albendazole, given at a dose rate of 150 mg/kg for 3 days, produced a 90 per cent reduction in the numbers of second stage larvae of Toxocara canis present in the tissues of dogs although no reduction in the number of larvae found in the brains of infected dogs occurred with this treatment. The results suggest that a course of 3 day therapy with these anthelmintics should prevent prenatal infections in puppies. However, if infection is acquired by bitches during late pregnancy or early lactation, the transmammary route of infection becomes important. Therefore, anthelmintic treatment of the bitch prior to pregnancy will not prevent transmission of infection to her puppies should the bitch acquire a new infection of T. canis during pregnancy or early lactation. Alternatively, infection with T. canis can be controlled through the treatment of neonatal puppies for migrating larvae of T. canis. Treatment of newborn puppies with fenbendazole, albendazole or oxfendazole at a dose of 100 mg/kg for 2–3 days produced a 91–99 per cent reduction in the number of adult parasites found. In addition, a single dose of fenbendazole, given at a dose rate of 40 mg/kg, eliminated 93–96 per cent of adult T. canis from the intestines of 4–5-week-old puppies. These latter treatments would need to be repeated to eliminate completely the infection from puppies.     

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.     

Fenbendazole treatment of pregnant bitches to reduce prenatal and lactogenic infections of Toxocara canis and Ancylostoma caninum in pups

A granulated formulation of fenbendazole was tested in a total of 23 treated and control, pregnant, parasite-free Beagle bitches experimentally infected with Toxocara canis and Ancylostoma caninum. The drug was administered to each treated bitch once daily in canned dog food at a dosage of 50 mg/kg body weight. Each of 2 treatment regimens tested was initiated on the 40th day of pregnancy. One regimen involved daily treatment continuing through the 14th postpartum day, and it resulted in 89% fewer ascarids and 99% fewer hookworms in pups born to medicated bitches, as compared with pups born to unmedicated controls. The other regimen of treatment, which was stopped on the day of parturition, was less effective in reducing ascarid and hookworm burdens (64% and 88% reductions, respectively). Three to 5 bitches from each of the treatment and control groups were allowed to whelp a 2nd litter without further treatment or further exposure to parasite infections. Hookworm burdens in 2nd-litter pups born of bitches that had initially received fenbendazole through the 14th postpartum day were significantly lower (P < 0.01; 85% reduction), when compared with the 2nd-litter control pups. All other parasite burdens were not significantly different. It was concluded that granulated fenbendazole is effective in reducing burdens of Ancylostoma caninum and Toxocara canis in newborn pups when the bitch is treated during the last third of pregnancy, especially when treatment (50 mg/kg/day) extends from the 40th day of pregnancy through the 14th postpartum day.     

Efficacy of ivermectin against induced gastrointestinal nematode infections in goats

The efficacy of ivermectin (0.08 per cent w/v oral solution) at different dose levels was evaluated against induced infections of adult Haemonchus contortus (21 days old) and Trichostrongylus colubriformis (21 days old) and fourth stage larvae of Oesophagostomum columbianum (17 days old), Ostertagia circumcincta (five days old) and Strongyloides papillosus (five days old). Twenty-five Boergoats (mutton goats) were randomly allocated by bodyweight within each sex to an untreated control group and four ivermectin treatment groups; ivermectin was administered at either 25, 50, 100 or 200 micrograms/kg orally, once. The goats were killed and processed for worm recovery 25 to 27 days after treatment. At 25 micrograms/kg the efficacy of ivermectin varied from 43 per cent for adult T colubriformis to more than 99 per cent for fourth larval stage O columbianum. Ivermectin at 50 micrograms/kg or higher was 99 per cent or more effective against all induced parasite infections with the exception of ivermectin at 50 micrograms/kg against S papillosus (97 per cent). For all parasites there was a statistically significant (P less than 0.05) difference between the control group and the pooled treated groups. No adverse reactions to ivermectin treatment were observed in the goats.     

Nitroscanate A new broad spectrum anthelmintic against nematodes and cestodes of dogs and cats.

SUMMARY: The efficiency of the broad spectrum anthelmintic nitroscanate against tapeworm and nematode infections of dogs was tested in artificially or naturally infected dogs. The safety of the compound was also evaluated in acute, subacute and chronic toxicity tests. At the recommended single dose rate of 50 mg/kg given to the dogs with food, nitroscanate was 98% efficient against Taenia hydatigena, T. ovis and T. pisiformis. The drug was highly efficient against Echinococcus granulosus only at the dose rate of 200 mg/kg given twice but total elimination of worms was not achieved. Natural infections of Dipylidium caninum, Ancylostoma spp and Uncinaria stenocephala were totally eliminated from all dogs at the dose rate of 25 mg/kg or higher. Nitroscanate was 97% efficient against adult Toxocara canis at a single dose of 50 mg/kg. When the dose was repeated 24 hours later total elimination of both mature worms and immature worms in puppies aged 2 weeks was achieved. The repeated dose of 100 mg/kg removed 98% of early immature worms from puppies aged 3 days. The drug was 100% efficient against adult Toxascaris leonina at a single dose of 50 mg/kg and 90.5% efficiency was achieved against early 4th stage larvae by two doses of 50 mg/kg. Nitroscanate was not efficient against Trichuris vulpis. The drug was efficient for the removal of Toxocara cati and Ancylostoma tubaeforme from cats. Nitroscanate caused no serious symptoms of toxicity at dose rates up to 10,000 mg/kg in single or repeated doses in young or older adult dogs. The drug was safely given to dogs during pregnancy, to young puppies and to cats. The regular use of nitroscanate as a broad spectrum anthelmintic for the prevention and control of parasitic infections of dogs is discussed.     

Activity of ivermectin against canine intestinal helminths

The anthelmintic activity of ivermectin was tested in 98 dogs against adult ascarids (Toxocara canis, Toxascaris leonina), hookworms (Ancylostoma caninum, A braziliense), and whipworms (Trichuris vulpis), and against experimentally induced infections (4th-stage larvae) of T canis and A caninum. Dosage levels tested were single subcutaneous injections of 50, 100, 200, or 400 micrograms/kg of body weight with appropriate vehicle-treated controls. A minimum of 4 (usually 5) dogs were tested with each parasite and dosage level. The lowest dosage level, 50 micrograms/kg, and all higher dosage levels expelled greater than 99% of the adult forms of both species of hookworms and intestinal larval forms of A caninum, as determined by worm counts at necropsy. A dosage level of 100 micrograms/kg was required to expel greater than 99% of whipworms and 200 micrograms/kg was necessary to expel adult (91%) and larval (97%) stages of T canis. Ivermectin was only marginally effective (34.2%, 46.2%, 69.2%, and 53.8%) against Toxascaris leonina at 50, 100, 200, and 400 micrograms/kg, respectively, and had no effect against occasional infections with the tapeworms, Dipylidium caninum (14 dogs) and Taenia spp (3 dogs).     

Efficacy of ivermectin against benzimidazole-resistant nematodes of sheep

Two trials involving a total of 36 Dorset horn lambs were conducted to assess the anthelmintic efficacy of ivermectin against experimental infections of benzimidazole-resistant strains of Haemonchus contortus and Ostertagia circumcincta. Two resistant strains of each of the two species were used and in each trial the lambs were allocated to three groups. One group was given 200 micrograms ivermectin/kg bodyweight orally, the second group was given 5 mg oxfendazole/kg bodyweight orally and the third group remained untreated as controls. Fourteen days after treatment the lambs were necropsied. Ivermectin was found to be more than 99 per cent to 100 per cent effective against all four benzimidazole-resistant strains, whereas oxfendazole was 78.6 per cent and 83.8 per cent effective against the H contortus strains, and 25.6 per cent and 39.8 per cent effective against the O circumcincta strains.     

Efficacy, safety and palatability of a new broad-spectrum anthelmintic formulation in dogs

The efficacy, safety and palatability of a new flavoured chewable anthelmintic tablet were investigated in dogs. The efficacy, based on worm counts, of a single recommended therapeutic dose (RTD) of 5 mg pyrantel + 20 mg oxantel + 5 mg praziquantel/kg bodyweight was assessed in experimental infections (EI) and natural infections (NI) with Trichuris vulpis, Echinococcus granulosus and Toxocara canis. For T vulpis, the efficacy of the treatment was 99.3 per cent in EI (comparing groups of six treated and six control dogs) and 100 per cent in NI (nine treated and nine control dogs). For E granulosus, the efficacy was more than 99.9 per cent in EI (11 treated and 11 control dogs). For T canis, the efficacy was 94.3 per cent in EI (10 treated and 10 control dogs) and 100 per cent in NI (12 treated and 13 control dogs). In a field study, Ancylostoma caninum (11 dogs) and T canis (11 dogs) faecal egg counts were reduced by more than 99 per cent, and in eight dogs with Dipylidium caninum proglotides in the faeces the efficacy was 100 per cent. The tablets were readily consumed by 56 of 64 (87.5 per cent) privately owned dogs. Safety was assessed in groups of six dogs treated either once with twice the RTD, once with six times the RTD, with twice the RTD on three consecutive days, or untreated. There were no significant differences in blood parameters between the groups, and no abnormal clinical findings. Two dogs treated with six times the RTD vomited, but no vomiting was observed when administration was repeated two days later.     

Efficacy of ivermectin and pyrantel pamoate combined in a chewable formulation against heartworm, hookworm, and ascarid infections in dogs.

Eight trials were conducted in dogs to document the efficacy of ivermectin (6 micrograms/kg of body weight) and pyrantel pamoate (5 mg of active pyrantel/kg) in a beef-based chewable formulation against Dirofilaria immitis, Ancylostoma caninum, Uncinaria stenocephala, Toxocara canis, and Toxascaris leonina. Three studies involved induced infection with D immitis, and 5 studies involved induced or natural infection with hookworms and ascarids. In 3 intestinal parasite trials, the efficacy of the combination chewable tablet was compared with each of its components. Results indicated that 1 component did not interfere with the activity of the other. In 1 heartworm and 2 intestinal parasite trials, the efficacy of pyrantel, ivermectin/pyrantel combination, or ivermectin with pyrantel dosage of 10 mg/kg was evaluated. The ivermectin/pyrantel combination was 100% effective in preventing development of D immitis larvae. Efficacy of the combined product against T canis, Toxascaris leonina, A caninum, and U stenocephala was 90.1, 99.2, 98.5, and 98.7%, respectively. In the intestinal parasite trials, each individual component was found not to interfere with the anthelmintic action of the other. Increasing the dosage of pyrantel to 10 mg/kg (2 x that in the combination) did not interfere with the efficacy of ivermectin against heartworm or increase the activity of pyrantel against intestinal parasites.     

Efficacy of a chewable formulation of ivermectin against a mixed infection of Ancylostoma braziliense and Ancylostoma tubaeforme in cats.

The efficacy of a beef-based, chewable formulation of ivermectin against a mixed infection of Ancylostoma braziliense and A tubaeforme was determined in cats. Ivermectin administered orally at approximately 24 micrograms/kg of body weight was 92.8% effective against adult A braziliense and 90.7% effective against adult A tubaeforme. The number of eggs per gram of feces had decreased 98.1% by 7 days after treatment. Clinical signs of hookworm disease also decreased after treatment. Location of adult parasites within the small intestine, percentage of infecting larvae that developed to the adult stage, and egg size in cats with infections of A braziliense and A tubaeforme were similar to those reported for cats with separate infections of either species.     

Efficacy of oxfendazole against inhibited larvae of Ostertagia ostertagi in naturally infected calves in the southern USA

Forty yearling calves were assigned to four equal groups; three of the groups were treated with oxfendazole at dose rates of 6.75 mg/kg, 4.50 mg/kg, or 2.25 mg/kg bodyweight while the fourth group served as an untreated control. The calves were native to north-east Mississippi, USA, and harboured natural infections of gastrointestinal nematodes. The study was conducted during July when inhibited early fourth-stage larvae may be found in large numbers after their acquisition in the spring. The calves were maintained in separate groups on concrete-floored pens for 17 days before the intraruminal administration of oxfendazole. Seven days after treatment, the calves were slaughtered and the gastrointestinal parasites counted. At all the dose rates examined oxfendazole exhibited an efficacy of at least 99.4 per cent against adults of Haemonchus placei, Trichostrongylus axei, Bunostomum phlebotomum, Cooperia species, T colubriformis, Oesophagostomum radiatum, and Trichuris ovis. The efficacy against adult Ostertagia ostertagi was at least 99.4 per cent at dose rates of 6.75 and 4.50 mg/kg bodyweight, but decreased to 93.7 per cent at 2.25 mg/kg. The efficacy of oxfendazole against inhibited larvae of O ostertagi decreased with dose rate from 78.8 per cent at 6.75 mg/kg, to 58.9 per cent at 4.50 mg/kg and 20.3 per cent at 2.25 mg/kg bodyweight.     

Efficacy of nemadectin, a new broad-spectrum endectocide, against natural infections of canine gastrointestinal helminths

Nemadectin, a new broad-spectrum endectocide, was highly efficacious against natural infections of all the major canine gastrointestinal helminths. At single oral dosages of 0.2-0.4 mg kg-1 body weight (BW), a liquid formulation administered in gelatin capsules was 100% effective in eliminating natural infections of Toxocara canis, Toxascaris leonina, Ancylostoma caninum and Uncinaria stenocephala. Tablets (267 mg) containing 4.6% nemadectin given at a rate of 1/3 tablet per 20 kg BW (0.2 mg nemadectin kg-1) were 100% active against T. canis, A. caninum and U. stenocephala. With both formulations, an increase in the dose rate to 0.6-0.8 mg kg-1 BW resulted in 99-100% elimination of Trichuris vulpis infections. No adverse reactions were observed in any of the treated dogs.     

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.