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Efficacy of ivermectin against cutaneous Draschia and Habronema infection (summer sores) in horses.

Thirty-one horses with naturally occurring summer sores were given a single IM injection of 0.2 mg of ivermectin (22,23-dihydroavermectin B1)/kg during the summer of 1980. Larvae of Draschia and/or Habronema spp were recovered from biopsy samples taken from 21 of 25 horses (84%) on the day of anthelmintic treatment. There was a marked clinical improvement in 26 horses (84%) 7 days after ivermectin was given. The typical summer sore was replaced by healthy pink granulation tissue at 7 days and this healed after 1 to 5 weeks. Biopsy samples were taken from 21 of these horses 1 to 6 weeks after treatment, and the samples in 18 horses (86%) were negative for larvae. Five of the 31 infected horses did not respond to a single dose and appeared to have become reinfected. Biopsy samples taken from 3 of these horses were positive for larvae 2 to 4 weeks after the 1st dose, but became negative and healed 1 to 2 weeks after a 2nd dose with ivermectin. Histopathologic examination of sections from lesions before anthelmintic treatment showed granulation tissue with marked eosinophilic infiltration, multiple eosinophilic abscesses, and transverse sections of nematodes. In sections examined after anthelmintic treatment, there were marked reduction in the number of eosinophils and absence of eosinophilic abscesses or nematodes, and the granulation tissue was more mature, as indicated by the appearance of dense fibrous connective tissue.

Animals↗

Infestation potential of Psoroptes ovis (Hering) from cattle injected with ivermectin.

Cattle scabies mites, Psoroptes ovis (Hering), surviving on cattle injected subcutaneously with ivermectin were capable of infesting to unprotected cattle 3, 5, 7, and 9 days after injection. All recipient cattle exposed to mites from vehicle-injected cattle developed reproductive colonies in 5 weeks. All recipient cattle exposed to mites from ivermectin-injected cattle at 3 and 5 days after injection developed reproductive colonies in 5 weeks. By 8 weeks, 3 of 4 and 2 of 4 recipient cattle exposed to mites from ivermectin-injected cattle 7 and 9 days after injection, respectively, developed reproductive colonies. To prevent the spread of mites, injected cattle should be isolated from uninfested cattle for longer than 9 days.

Animals↗

Efficacy of ivermectin in oral paste formulation against immature gastrointestinal and pulmonary nematodes in cattle.

The anthelmintic efficacy of ivermectin in oral paste formulation was evaluated against the 4th-stage larvae of 8 gastrointestinal nematodes and the common lung-worm in 14 experimentally inoculated calves. Two groups consisting of 7 calves each were formed by restricted randomization on body weight. The infective larvae were given orally to the animals on a staggered schedule so that the parasites were in the 4th larval stage when the animals were treated. One group was given vehicle paste, and the other group was treated with ivermectin in oral paste at the dose level of 200 micrograms/kg of body weight. The animals were killed 18 or 19 days after treatment. Ivermectin was 100% effective against Dictyocaulus viviparus, Oesophagostomum radiatum, Haemonchus placei, Ostertagia ostertagi, and Trichostrongylus axei and greater than 99% effective against Cooperia oncophora, C punctata, T colubriformis, and Nematodirus helvetianus.

Administration, Oral↗

Effect of ivermectin in heifers on mortality and egg production of Psoroptes ovis.

Ten stanchioned heifers, heavily infested with Psoroptes ovis (Hering), were each given a single subcutaneous injection of 200 micrograms of ivermectin/kg. Another 10 heavily infested heifers (stanchioned) were injected subcutaneously with the solvent system (vehicle) used to formulate the ivermectin. Treatment with the vehicle did not reduce mite populations or total egg counts. The 10 heifers treated with ivermectin had an immediate reduction in live mite and egg counts (an increase in the percentage of mortality of mites) and were completely free of psoroptic mites by 20 days after treatment. Ivermectin was equally effective against adult and immature psoroptic mites.

Animals↗

Efficacy of ivermectin against gastrointestinal nematodes in dromedary camels.

The anthelmintic activity of ivermectin when administered orally and subcutaneously at a dosage of 0.2 mg/kg of body weight was evaluated in 4 trials involving 20 dromedary camels (Camelus dromedarius). Fecal egg counts were made on the day of treatment and at 2, 4, and 10 weeks after treatment. Trichostrongylid egg counts were reduced by a maximum of 100% when ivermectin was administered orally and by greater than 88% when given subcutaneously. Egg counts of Trichuris spp were reduced by greater than 85% with oral administration, but increased following subcutaneous treatment. No adverse local or systemic reactions were observed following treatment with ivermectin by either route.

Animals↗

Effect of ivermectin on performance of beef cattle on Georgia pastures.

A total of 469 cows and calves from 2 herds, each on 6 pastures, was used to evaluate the anthelmintic efficacy and animal-performance benefits of ivermectin given subcutaneously at a dosage of 200 micrograms/kg to nursing beef calves and their dams during a grazing season. Pastures were paired across the 2 herds. Three pasture groups from 1 herd were randomly assigned to either a nonmedicated control or to a medicated group. Treatment assignments were reversed in the other herd. The control groups comprised 110 cows and 108 calves, whereas 127 cows and 124 calves were treated with ivermectin (200 micrograms/kg). The cows were treated once, in late spring, and the calves were treated twice, once in late spring and again in midsummer. Cattle from one herd were weighed on days - 12, 21, 49, 77 (day of 2nd treatment for calves), and 105, and the other herd was weighed on days - 6, 23, 57, 86 (day of 2nd treatment for calves), and 113. Rectal fecal samples for nematode egg counts were obtained from approximately 25% of the cattle in each pasture on weighing days; usually, the same cattle were sampled each time. Calves treated with ivermectin gained (P less than 0.05) more weight than control calves up to the 2nd treatment date and up to the termination of the study. There was no significant difference between treated and control cows, with regard to weight gain over either interval. Treated calves had fewer positive fecal egg counts (P less than 0.01) and passed fewer eggs (P less than 0.05) after both treatments than did control calves. There were no differences in either number of eggs or number of negative cows between treatment groups. Adverse reactions attributable to treatment were not seen.

Animals↗

Anthelmintic activity of ivermectin in pigs naturally infected with Ascaris and Trichuris.

The anthelmintic efficacy of ivermectin administered by subcutaneous (SC) injection or orally via the drinking water was investigated in feeder pigs naturally infected with Ascaris suum and Trichuris suis. Group 1 pigs (n = 5) were given drinking water as a placebo, group 2 pigs (n = 5) were given ivermectin by SC injection (300 micrograms/kg of body weight), and group 3 pigs (n = 5) were given ivermectin in water also at a dosage rate of 300 micrograms/kg of body weight. At necropsy 11 days later, the mean worm counts in group 1 pigs were 4 for Ascaris and 50.2 for Trichuris. All adult and juvenile ascarids were removed from the intestine in groups 2 and 3 pigs. Compared with the number of Trichuris in group 1 pigs, the number of Trichuris was reduced by 91.2% and 78.1%, respectively, for the orally and SC treated pigs.

Animals↗

Persistent anthelmintic effect of ivermectin in cattle.

The persistent anthelmintic effect of ivermectin given subcutaneously at 200 mcg/kg was evaluated against induced infections of Haemonchus placei, Ostertagia ostertagi, Cooperia spp. (C. pectinata and C. punctata), Bunostomum phlebotomum and Oesophagostomum radiatum in cattle. Forty-four Friesian bull calves raised under worm-free conditions were restrictively randomized to one untreated control group and 3 ivermectin treated groups of equal size according to mass. Animals in the different treated groups were treated either 9, 7 or 5 d before infestation, which was induced in all animals on the same day. The results are presented as percentage reduction and Non Parametric claims. Nine days after treatment the effect of ivermectin was virtually undiminished against O. ostertagi and B. phlebotomum and 7 d after treatment against Cooperia spp. Counts of all worms were reduced by 99% or more following the treatment given 5 d before infection. According to the Non Parametric Method, "A" claims (i.e. 80% effective in 80% of the treated animals) were achieved against all 5 worms up to 7 d after treatment and against O. ostertagi and B. phlebotomum up to 9 d after treatment.

Animals↗

The efficacy of ivermectin against helminth and arthropod parasites of impala.

The efficacy of ivermectin, injected subcutaneously at a dosage rate of 200 mcg/kg live mass, was determined against nematodes, ixodid ticks and lice infestations acquired by free-living impala, Aepyceros melampus, in the Kruger National Park. Although the parasite burdens of the untreated control animals varied considerably, ivermectin appeared to be highly effective against 7 nematode species and effective against 3 others. Of the 4 tick species recovered, only Boophilus decoloratus appeared to have been affected. In the case of the lice infestations, ivermectin was highly effective against 3 species of Linognathus, but ineffective against the 2 Damalinia species present.

Animals↗

Anthelmintic activities of ivermectin against gastrointestinal nematodes of cattle.

The anthelmintic efficacy of ivermectin, a combined solution of the B1a and B1b fractions of avermectin, was assessed in a controlled trial. Twenty-four yearling calves experiencing naturally acquired, clinical gastrointestinal helminthiasis were evenly divided on the basis of weight into two 12-animal groups. The medicated group was given (subcutaneously) ivermectin at the dose rate of 200 microgram/kg of body weight. The control animals were given the vehicle alone, at an equivalent rate. All animals were killed 14 days later. At necropsy of the calves, gastrointestinal helminth arithmetic means were 178,626 and 575 for the control and the treated groups, respectively, an overall reduction of 99.7%. Nematodes which were present at substantial levels were Ostertagia ostertagi, O lyrata, Trichostrongylus axei, Cooperia punctate, C oncophora, C mcmasteri, and Oesophagostomum radiatum. Anthelmintic activity of ivermectin was excellent regardless of nematode species, sex, or stage of development.

Animals↗

Efficacy of injectable and oral paste formulations of ivermectin against gastrointestinal parasites in ponies.

A controlled test was used in ponies to compare the antiparasitic efficacy of ivermectin (22,23-dihydro-avermectin B1) in an injectable micelle solution administered IM with the efficacy of the same drug in an oral paste formulation. Parasite infections were naturally acquired in southern Louisiana. The drug was tested in both formulations at a dosage level of 0.2 mg/kg of body weight. Ivermectin in both formulations tested had an efficacy greater than 98% against Gasterophilus intestinalis and G nasalis larvae. Trichostrongylus axei, Habronema spp, Strongylus vulgaris, S. edentatus, and species of small strongyles present. Efficacy of ivermectin against Oxyuris equi larvae was 100% in the paste formulation and 93% in the injectable formulation. The ponies were less uniformly infected with S equinus, Draschia megastoma, Parascaris equorum, O equi adults, Anoplocephala perfoliata, and A magna. However, observations indicated that the drug in either formulation was also effective against these parasites, except Anoplocephala spp.

Administration, Oral↗

Effectiveness of ivermectin against later 4th-stage Strongylus vulgaris in ponies.

Twelve pony foals were reared worm-free and inoculated with Strongylus vulgaris. Approximately 8 weeks after they were inoculated, 6 foals were given ivermectin IM at a dosage rate of 200 micrograms/kg of body weight and 6 were given a placebo. All foals were necropsied 35 days after treatment. Ivermectin was 98.9% effective in eliminating later 4th-stage S vulgaris larvae located near the origin of major intestinal arteries and in reducing clinical signs and permitting resolution of lesions associated with verminous arteritis. One pony foal reared on pasture and with evidence of arteritis of the cranial mesenteric and ileocolic arteries on arteriography was treated with ivermectin at a dosage rate of 200 micrograms/kg of body weight. On arteriographs taken subsequently, there was evidence of regression of the lesion, and at necropsy 9 weeks after treatment, there was no arteritis or larvae in those arteries.

Angiography↗

Efficacy of ivermectin against third-stage Dirofilaria immitis larvae in ferrets and dogs.

Ivermectin prevented maturation of Dirofilaria immitis when given per os to ferrets at a dosage of 0 X 1 mg ivermectin per kg bodyweight two days after inoculation with third stage heartworm larvae. Similar results were found in dogs treated one day after infection at a dosage of 0 X 05 mg ivermectin per kg. No heartworm were found in the hearts and lungs of five treated dogs compared to an average of 11 worms per dog in five control animals.

Animals↗

Effect of repeated treatments with ivermectin on the incidence of onchocerciasis in northern Cameroon.

Mass treatments with ivermectin have been undertaken each year since 1987 in an area hyperendemic for onchocerciasis in northern Cameroon. The impact of these successive treatments on the incidence of infection in humans was evaluated by comparing the prevalence of skin microfilariae (PMF) and the mean microfilarial skin densities (MFD) observed in 1987 and 1992 in 5-7-year-old children who had never taken the drug but who were members of the treated communities. In 1992, the PMF and the MFD in children in this age group who never received ivermectin were reduced by 55% and 77%, respectively, in comparison with the values observed in 1987, before the first treatment round. These results reflect a pronounced reduction in the intensity of the transmission of Onchocerca volvulus in the treatment zone. The influence of the ivermectin treatment coverage in the human population, as well as the vectorial capacity and the dispersal of the vector blackflies, on the transmission of onchocerciasis is discussed.

Adolescent↗

Effect of semiannual treatments of ivermectin on the prevalence and intensity of Onchocerca volvulus skin infection, ocular lesions, and infectivity of Simulium ochraceum populations in southern Mexico.

The effect of semiannual ivermectin treatment along with nodulectomy on filarial transmission levels were estimated during the three dry seasons of 1991-1993 in a hyperendemic village in southern Mexico. Parasitologic and ophthalmologic examinations were carried out every six months until five drug treatments were completed. Ivermectin mass treatment with a coverage of approximately 80% had a significant impact (P < 0.05) on the prevalence of skin infection and the mean microfilarial skin density (CMFL), which were reduced 38% and 89%, respectively. A gradual and significant (P < 0.05) decrease in the mean microfilariae number in the anterior chamber of the eye and in corneal opacities was also observed as the CMFL was reduced. After three treatments, these were reduced 84% and 69%, respectively. However, after two years of continuous intervention, no significant differences (P > 0.05) were observed in either the daily mean infective biting density and the daily mean transmission potential. This was probably due to the remaining microfilarial load provided by the untreated resident population and migrant groups. On the whole, our results confirm both the efficacy of ivermectin to alleviate the clinical manifestations of the disease and its minimal impact on Onchocerca volvulus transmission, and indicate the need both to achieve higher levels of drug coverage and to incorporate other measures to stop transmission until a macrofilaricide drug is found.

Adolescent↗

Macrofilaricidal activity of albendazole-ivermectin combination: histopathological evaluation of adult Molinema dessetae.

The macrofilaricidal effect of albendazole in association with ivermectin was assessed in the rodent Proechimys oris, infected with Molinema dessetae. The drug combination was given to five rodents 190 days after infection. A similar group was used as control. The doses administered were 10 mg per kg for albendazole and 0.04 mg per kg for ivermectin over five days. The histological examination of intra-peritoneal nodules done six weeks after therapy revealed a clear-cut macrofilaricidal effect. The number of dead worms was significantly higher in the treated group. The histological examination revealed a lesion pattern that was related to the drug exposure. This consisted of nodules, each containing a necrotic worm that had its morphology preserved and was surrounded by a foreign body granuloma. This lesion was only seen in the treated group. A pattern related with the spontaneous death of worms was also observed. The results obtained here show the importance that albendazole-ivermectin combination could have in human filariasis therapy. Further studies in man should be done to confirm the macrofilaricidal effect of this drug combination in human filariasis.

Albendazole↗

[Efficacy of ivermectin in preventing Dirofilaria repens infestation in dogs naturally exposed to contagion].

The ability of ivermectin to control canine dirofilariosis in naturally infected dogs was tested. Two studies were carried out in the coast line of Grosseto district (Italy), where D. repens infection is endemic. A sample of 384 dogs from the area was examined as background controls and we found D. repens in 21.1%, D. immitis in 7.8% and both species in 6.5%. In the first study we used 72 privately-owned dogs, of varying sex, breed and age; all animals were negative to Knott's modified test for microfilariae and to CITE test for the adult antigens. All the dogs were treated monthly per os with tablets of ivermectin (> or = 6 mcg/kg) seven times from May 1991. All dogs were found negative for microfilariae 6-8 months after the last treatment. The second experiment was carried out on 16 Beagles aged 5.5-7 months (8 control dogs and 8 treated dogs). The dogs lived in a semi-open kennel in the selected area. We treated 8 dogs--8 times at monthly intervals, starting in June--with ivermectin tablets per os (> or = 6 mcg/kg). The monthly examination for circulating microfilariae (Knott's modified test) showed D. repens in two control dogs 7 months after the beginning of the experiment, one month later in 6 control and in another control animal also positive for D. immitis between the 10th and 11th month. Treated dogs were always negative. At the necropsy of all the dogs, about 11 months after the beginning of the experiment, we found adults or pre-adults of filariae in all the control dogs. Four animals had a double infection, 3 with D. repens and one with D. immitis. We never found adults or pre-adults of filariae in treated dogs.

Animals↗

Effects of ivermectin in canine blood on Anopheles quadrimaculatus, Aedes albopictus and Culex salinarius.

Blood from ivermectin-treated dogs was tested against adult mosquitoes. Mosquitoes were allowed to bloodfeed on mixed breed dogs 4 h after dogs were given oral dosages of ivermectin. In test 1, Anopheles quadrimaculatus and Aedes albopictus fed on dogs that had been given ivermectin dosages of 0, 6, 12, and 24 micrograms/kg. In test 2, Culex salinarius and Ae. albopictus fed on dogs that had been given dosages of 0, 15, 30, 60, and 120 micrograms/kg. In both tests, mosquitoes were observed for mortality at 1, 12, and 24 h postfeeding. Surviving mosquitoes were observed for oviposition and egg hatching. In the first test, there was a significant increase in mortality and a significant decrease in number of eggs/female and egg hatchability in An. quadrimaculatus but not in Ae. albopictus (P < 0.05). An LD50 of 9.9 micrograms/kg (95% FL 6.0-13.8) was determined for An. quadrimaculatus. In the 2nd test, there were no significant differences in any variable for Cx. salinarius or Ae. albopictus, except that eggs from Ae. albopictus had reduced hatching at all dosages.

Aedes↗