Efficacy of ivermectin against the swine kidney worm, Stephanurus dentatus

Ivermectin in solution was given subcutaneously (in the neck) at the rate of 0.5 mg/kg of body weight to 5 sows naturally infected with kidney worm (Stephanurus dentatus). Six similar sows were used as nontreated controls. A total of 114 kidney worms were recovered from daily urine samples of 4 of the 5 treated sows (the 5th sow's samples were negative) during the first 4 days after treatment. Ten kidney worms were recovered from daily urine samples of 1 control sow on the 2nd and 3rd days of the post-treatment period. Examination of urine samples from treated sows for kidney worm eggs showed a precipitous numerical decrease. Treated animals became negative between the 5th and 12th days after treatment, and remained negative until necropsy on the 61st day. Compared with control sows, hatchability of eggs and survival of larvae from treated sows was reduced by 9% and 7%, respectively. Kidney worms were not recovered at necropsy from the treated sows, and a total of 392 kidney worms were recovered from the control sows (av 65).     

Efficacy of fenbendazole against the swine kidney worm Stephanurus dentatus

Fenbendazole in ground feed was fed on 3 successive days at the rate of 3 mg/kg of body weight to 15 sows naturally infected with kidney worm (Stephanurus dentatus). Fifteen similar sows were used as nontreated controls. A total of 49 kidney worms were recovered from daily urine samples collected from 10 of the 15 treated sows within 5 days after the 3rd dose of treatment. One control sow passed 10 kidney worms on the 2nd and 3rd days. Urine samples from treated sows became negative for kidney worm eggs by the 5th to 12th posttreatment days, except for urine samples from 1 sow that contained a few eggs on the 12th day and another sow that contained a few eggs on the 19th and 33rd posttreatment days. Urine samples from control sows contained approximately the same number of kidney worm eggs in the posttreatment period as earlier. Compared with that in control sows, the hatchability of the parasite eggs from treated sows was greatly reduced. Kidney worms were not recovered at necropsy from the treated sows and a total of 860 kidney worms were recovered from the control sows (57 av).     

Fenbendazole as a therapy for naturally acquired Stephanurus dentatus and gastrointestinal nematodes in feral swine

Adult feral swine, naturally infected with kidney worms (Stephanurus dentatus) and gastrointestinal nematodes, were divided into two groups of 10 pigs each. One group was treated with fenbendazole (Panacur, Hoechst AG, Frankfurt am. Main) mixed in feed at the rate of 3 mg kg-1 body weight for 3 days. The second group received feed only and was designated as non-treated controls. The animals in both groups were necropsied 3 weeks post-treatment and examined for the presence of live and dead adult kidney worms in the perirenal and ureteral area, ureteral penetration, the presence of kidney worm larvae in the liver, hepatic scars due to kidney worm larval migration, and for liver fibrosis. No live adult kidney worms were found in the perirenal and ureteral areas of treated pigs, and the non-treated pigs harbored an average of 42.8 live worms. No liver kidney worm larvae were found in the livers of treated pigs, and the non-treated pigs averaged 6.7 live larvae. At necropsy, urine samples from 8 of the 10 treated pigs contained no kidney worm eggs, and only 2 eggs were found in samples from each of the remaining 2 pigs in this group. In contrast, urine samples from 8 of the non-treated pigs contained numerous kidney worm eggs. Reductions in ascarid (Ascaris suum) and nodular worm (Oesophagostomum dentatum) egg counts were also observed in treated pigs.     

An abattoir survey of the prevalence of gastro-intestinal helminths andStephanurus dentatus in pigs in Belize

In an abattoir survey in Belize 137 pigs were examined for gastro-intestinal helminths and Stephanurus dentatus. Hyostrongylus rubidus, Physocephalus sexalatus, Globocephalus species and Trichostrongylus colubriformis were recorded for the first time. Ascarops strongylina, Ascaris suum, Macracanthorynchus hirudinaceus, Strongyloides ransomi, Trichuris suis, Oesophagostomum species and S. dentatus were also found. Oesophagostomum species (45%) and S. dentatus (42%) were the most prevalent. The prevalence of infection with different species was compared between pigs of different origin, breed and management. Differences were apparently due to management; most species were more common in poorly managed pigs. M. hirudinaceus and S. dentatus were used as "markers" to indicate poor management. The usual methods of faecal egg counting were found to be unreliable for the diagnosis of M. hirudinaceus infection.     

Anthelmintic treatment of prepatent stephanuriasis with flubendazole, levamisole and disophenol and the effects on liver-specific serum enzymes

Haematological parameters and liver specific serum enzymes were examined in pigs during the first 12 weeks of liver migration of larvae following experimental infection with 1000 infective Stephanurus dentatus larvae. No significant changes in total red blood cell counts, packed cell volume, or haemoglobin content were observed. Total white blood cell counts and circulating eosinophils rose rapidly from days 5 and 19 after infection, respectively. Treatment with a mixture of levamisole (LEV) at 10 mg/kg and flubendazole (FLU) at 50 mg/kg in feed four weeks after infection halted the leucocyte response and returned values to normal in two weeks. Disophenol (DIP) at 15 mg/kg subcutaneously restricted the leucocyte response but it was only terminated following FLU treatment alone on day 61. No effects of S dentatus or either anthelmintic treatments on liver specific serum enzymes glutamate dehydrogenase, sorbitol dehydrogenase or gamma-glutamyl transpeptidase were found. Animals killed seven, 26 and 54 days after treatment showed significant resolution of fibrotic liver lesions after LEV + FLU but not after DIP. We conclude that LEV + FLU is an effective treatment for prepatent stephanuriasis but that liver damage is insufficiently traumatic to release sufficient enzymes into serum to be pathognomonic or to assess anthelmintic efficacy.     

Effect of cambendazole on swine kidneyworm,Stephanurus dentatus

Two trials were conducted to determine the effect of cambendazole against natural infections of the swine kidneyworm, Stephanurus dentatus, in sows. In the first trial, nine sows were given a single dose of 20 mg cambendazole/kg body weight, in the feed, and eight sows were not treated. In the second trial, five sows were given 40 mg cambendazole/kg body weight and four were untreated. Urine volume, S. dentatus eggs per milliliter of urine, egg hatchability, and larval survival to the third stage were determined pre and post treatment. Adult kidneyworms were counted at necropsy, 14 days after treatments. Only a temporary decline in egg hatchability was observed on the day after treatment in each trial, and cambendazole was not found to be effective against adults of S. dentatus.     

Field performance of the equine parasiticide ivermectin in an oral paste

Ivermectin, a derivative of one of the avermectin compounds, was administered at 200 mcg per kg of body weight in an oral paste formulation to 80 mixed-breed ponies of both sexes and various ages. Twenty similar ponies received oral paste vehicle. Anthelmintic activity was determined by comparing fecal egg counts taken before and 14 days after ivermectin treatment to the counts of fecal samples from vehicle-treated controls. Commonly used equine vaccines were administered at the time of treatment. Sixteen of the 20 vehicle-treated ponies had positive counts prior to treatment and 17 were positive 14 days after treatment; 66 of the 80 ivermectin-treated ponies had positive counts prior to treatment; all 80 ponies had zero counts 14 days after treatment. The eggs were identified as strongylid in all the positive ponies while three ponies also hadOxyuris equi eggs prior to treatment.No adverse reactions were attributable to ivermectin oral paste treatment or concurrent vaccine administration.     

Pig production in the Solomon Islands

In the Solomon Islands pigs grow slowly and sows have small litters. An experiment using 124 pigs in 16 litters from eight sows compared the effect of village breed, village diet and village husbandry which encouraged infection of pigs with Stephanurus dentatus, with the effect of European breed, commercial rations and a system of management which ensured freedom from S. dentatus infection on the productivity of pigs. It was shown that the village diet was markedly inferior to the commercial rations and had by far the greatest influence of any of the three factors studied on the parameters measured. The village breed was not inferior in litter size or growth rate when fed on the village diet, but was inferior in growth on the commercial diet. No harmful effects of the village husbandry system were detected on either type of pig but this may have been due to the lightness of S. dentatus infections.     

Field efficacy of ivermectin plus praziquantel oral paste against naturally acquired gastrointestinal nematodes and cestodes of horses in North America and Europe

The efficacy of an oral formulation of ivermectin plus praziquantel in the reduction of nematode and cestode egg counts in horses was assessed in 273 horses under field conditions at 15 sites in North America (n = 6) and Europe (n = 9). Horses were confirmed by fecal examination to have natural infections of strongyles (100%) and tapeworms (76%). Replicates of four horses were formed at each site, and in each replicate three animals received ivermectin (0.2 mg/kg body weight) plus praziquantel (1 mg/kg body weight) oral paste and one animal remained untreated or received vehicle paste. Fecal samples were collected for fecal nematode and cestode egg counting before and 7, 8, 9, 14, 15, and 16 days after treatment. Horses treated with ivermectin plus praziquantel oral paste had significantly (P <.01) lower posttreatment strongylid and cestode egg counts (reductions of 98% or more) than controls. Combined site analyses revealed that 95% or 96% of the horses positive for cestode eggs before treatment that were treated with ivermectin plus praziquantel were negative for cestode eggs at each posttreatment fecal examination. No adverse reactions attributable to ivermectin plus praziquantel oral paste treatments were observed. The results of the studies demonstrated that ivermectin plus praziquantel paste was highly effective in reducing egg shedding by gastrointestinal nematodes and cestodes, and no adverse reactions were observed in horses treated under field conditions.     

Effect of fenbendazole and ivermectin on development of strongylate nematode eggs and larvae in calf feces.

Thirty-nine weaned steer calves (mean weight 284 kg) were maintained under dry-lot conditions and assigned (based on fecal nematode egg count) to one of three treatment groups of 13 animals each as follows: control (no treatment), fenbendazole (5 mg kg-1), and ivermectin (0.2 mg kg-1). Fecal samples were collected 12 h before treatment, at treatment, and 12, 24, 48 and 72 h after treatment for determination of nematode eggs per gram, and (after culture) infective larvae per gram and population distribution. The effect of treatment on egg development was observed in feces collected 12 and 24 h after treatment. There was essentially no difference in efficacy, based on egg counts, of fenbendazole and ivermectin. Egg count was reduced 100% by both anthelmintics at 72 h after treatment. Viability, based on percent of eggs reaching the infective larval stage, of developing stages at 12, 24, and 48 h after fenbendazole treatment was 0.1%, 1.1%, and 0%; after ivermectin treatment the corresponding values were 23.7%, 30.1%, and 28.6%, respectively. Fenbendazole treatment resulted in little or no development of eggs and/or larvae in feces deposited 12 and 24 h after treatment, whereas development proceeded normally (compared with the control group) in ivermectin treated feces. Population distribution of infective larvae was predominantly Haemonchus and Cooperia with some Ostertagia and Oesophagostomum.     

Parascaris equorum in foals and in their environment on a Swedish stud farm, with notes on treatment failure of ivermectin

Environmental contamination and the egg excretion pattern of the ascarid Parascaris equorum (Nematoda) was investigated in relation to anthelmintic treatment on a Swedish stud farm. Faecal samples from 15 foals, dewormed every 8th-week with a paste formulation of ivermectin at the standard dose rate of 0.2 mg/kg bodyweight, were collected at five sampling occasions between August and November 2006. In addition, soil samples were obtained from four paddocks used by these foals in November 2006. The number of eggs per gram (epg) was counted in both faeces and soil. Egg excretion started when the foals were 3-4 months, and reached the highest levels when they were approximately 5-month-old, and was then followed by a decline. Egg excretion seemed to be unaffected by ivermectin despite these foals were dewormed at regular intervals. In four out of five foals examined 10 days after treatment, epg actually increased. In contrast, when either fenbendazol or pyrantel embonate were used instead of ivermectin, treatments were effective. The number of eggs in soil was significantly higher in the permanent paddock compared to in the temporarily used soil paddock and in the summer paddocks.     

Efficacy of parenteral administration of ivermectin in the control of strongylidosis in donkeys

Investigations into the efficacy of parenteral ivermectin (Pandex) administration for strongylidosis control in donkeys were carried out. The preparation was applied subcutaneously at a dose of 0.2 mg/kg (1 ml/50 kg body weight). One day prior to the treatment and 14 days post-treatment, individual coprological samples were obtained for faecal nematode egg counts and larval culture. The study was performed on 263 donkeys originating from different regions of Bulgaria. Prior to the treatment and 20 days after that, blood samples were obtained from 64 previously infected animals for monitoring of changes in eosinophil leukocyte counts. The subcutaneous application of ivermectin had an efficacy of 96% in terms of reduction of faecal egg counts. In 92.2% of infected donkeys, a complete reduction of faecal eggs count occurred (0 eggs per gram of faeces epg), whereas in the remaining 7.8% of the infected donkeys, the egg counts were reduced by 72%. The reduction in faecal egg counts did not result in changes in eosinophil counts. The results obtained as well as the lack of local changes after the subcutaneous application of ivermectin in donkeys allow us to recommend its use for control of strongyles in donkeys.     

Identification of foals infected with Parascaris equorum apparently resistant to ivermectin

During September 2002, routine fecal examinations performed on 16 Thoroughbred foals residing on a farm outside Toronto, Ontario, Canada, revealed low to moderate numbers of Parascaris equorum eggs in feces from 9 of the 16. All foals were then treated with ivermectin at a dose of 220 to 280 microg/kg (100 to 127 microg/lb), p.o., and fecal egg counts were repeated 12 days later. Fecal P. equorum egg counts increased between the first and second fecal examination in 7 foals, were unchanged in 1, and decreased in 5. Fecal samples were collected 13 days after treatment from 21 additional foals that had been treated with ivermectin at the same dose, and P. equorum eggs were detected in 12 of the 21. For all 37 foals, high P. equorum egg counts (> or = 100 eggs/g of feces) 12 to 13 days after ivermectin treatment were significantly more likely in foals that had been regularly treated with ivermectin since birth and permanently resided on the farm, compared with foals that had been treated with other anthelmintics or had an unknown deworming history. Collectively, these data suggested that P. equorum in these foals was resistant to ivermectin administered at the recommended dose.     

Prevalence of benzimidazole resistance on horse farms in Germany

Faecal egg counts (FECs) were made on samples from 1383 horses on 64 farms in northern Germany between August 2000 and November 2001. There were significant differences between the mean FECs in the two years; in 2000, 59.6 per cent of 369 samples were positive and in 2001, 32.6 per cent of 1014 samples were positive for strongyle eggs. The results of a FEC reduction test indicated that resistance to fenbendazole was present on all 10 farms where it had been used, including in 33 of 60 horses tested. In contrast, treatment with ivermectin resulted in the complete elimination of nematode eggs in all the 77 horses tested. The mean LD50 values of the egg hatch test for thiabendazole indicated resistance on all 20 farms investigated and in 94 of 134 samples (70 per cent).     

Effectiveness of an ivermectin liquid formulation given by nasogastric tube against strongyles in horses

Twenty horses were treated with ivermectin either by nasogastric tube with a liquid formulation for sheep or per os with a paste formulation for horses at a dosage of 200 μg/kg of body weight. Fecal samples were collected from these horses and from ten untreated horses at the time of treatment and every 2 wk thereafter for up to 10 wk. The samples were examined for nematode eggs using the Cornell-McMaster dilution and the Cornell-Wisconsin Double Centrifugation procedures.

There were no signs of toxicosis in horses treated with ivermectin. Strongyle eggs were found in the feces of all horses before treatment. Subsequently, they were found in untreated horses, but not in treated horses at 2 wk nor in most of them for up to 8 wk after treatment. At 10 wk most of these horses had strongyle eggs in their feces, but in general fewer than at pretreatment.

     

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.     

The effects of ivermectin and moxidectin on egg viability and larval development of ivermectin-resistant Haemonchus contortus

The in vivo effects of ivermectin and moxidectin on egg viability and larval development of ivermectin-resistant Haemonchus contortus were examined over time after anthelmintic treatment of sheep. Twenty merino sheep, (12 months old) were allocated to five treatment groups and infected with ivermectin-resistant H. contortus. Thirty one days later, the sheep were treated with intraruminal ivermectin capsules, oral ivermectin, oral moxidectin or injectable moxidectin at the manufacturer's recommended dosages, or left untreated. At various times up to 112 days after treatment, faecal egg counts (FEC) were determined and development rates of infective larvae (L3) cultured in faeces or on agar were measured. Eggs in faecal cultures from ivermectin capsule treated sheep showed reduced L3 development percentages in comparison to faecal cultures from untreated sheep. Eggs from ivermectin capsule treated sheep, isolated from faeces, and cultured on agar showed similar L3 development to eggs from control sheep. These results demonstrate an inhibitory effect of excreted ivermectin in faeces on larval development of ivermectin-resistant H. contortus. L3 development in faecal culture from animals receiving oral ivermectin were reduced for only 3 days after treatment. Faecal egg counts and development of L3 larvae in both culture systems from moxidectin treated sheep were low, due to the high efficacy of the drug. Egg counts in moxidectin treated sheep were reduced by approximately 90% 24h after treatment, before decreasing to almost 100% at 48h, suggesting that the current quarantine recommendation of holding sheep off pasture for 24h after treatment may still lead to some subsequent pasture contamination with worm eggs.     

Efficacy of albendazole and moxidectin and resistance to ivermectin against Libyostrongylus douglassii and Libyostrongylus dentatus in ostriches

Anthelmintic resistance has emerged globally as a problem amongst nematode of livestock and has been particularly well documented in equine and small ruminants. There are no studies regarding the efficacy of anthelmintics against the hematophagous nematodes in ostriches, Libyostrongylus dentatus; and just a few on L. douglassii. Here the efficacy of albendazole, ivermectin and moxidectin were evaluated against these two species in an ostrich farm in Minas Gerais state, Brazil. The feces were collected on the day of treatment and after 13days of an oral dose of albendazole (6mg/kg), or an injected dose (0.2mg/kg) of ivermectin or moxidectin. The fecal egg count reduction test and coprocultures were performed to determine possible resistance against the drugs used. An efficacy of 60% was found for ivermectin, while albendazole and moxidectin were 100% effective. Both worm species appeared to have reduced sensitivity to ivermectin.     

Persistent activity of doramectin and ivermectin against Ascaris suum in experimentally infected pigs.

A study was conducted to investigate the persistent nematocidal activity of two avermectins against experimentally-induced infections of Ascaris suum in swine. Seventy-two nematode-free cross-bred pigs of similar bodyweight were randomly allotted to nine treatment groups of eight pigs each. Eight of the groups were treated with injectable solutions containing 300 microg of doramectin/kg (IM) or 300 microg of ivermectin/kg (SC) either 0 (same day), 7, 14, or 21 days prior to an oral challenge of 50000 embryonated A. suum eggs. The ninth group (control) was challenged in parallel without any avermectin treatment. At 41 or 42 days after challenge, pigs were euthanatized and adult and larval stages of A. suum were collected from the gastrointestinal tract of each pig and counted. Both avermectins significantly (P < 0.0002) reduced nematode counts when given on the day of challenge (0 days prior), and the efficacy was 100% and 97.5% for doramectin and ivermectin, respectively. Doramectin given 7 days prior to challenge significantly (P < 0.0001) reduced nematode counts, and the efficacy was 98.4%. For all other avermectin-treatment groups, nematode counts were not significantly reduced compared to those in control pigs. These data indicated that anthelmintic activity of ivermectin against A. suum persisted for less than 7 days and the activity of doramectin persisted for more than 7, but less than 14 days.     

Losses to internal parasites in swine production

Experimental infections of pigs with Strongyloides ransomi, Stephanurus dentatus, Ascaris suum, Oesophagostomum spp. or Trichuris suis at increasing levels generally decrease daily gain and increase feed to gain ratio linearly. At lower, subclinical levels of infection, the feed to gain ratio typically is increased 3% to 6% by an infection. Based on low-level experimental infections with A. suum, the economic loss to producers in the U.S. from increased feed to gain ratio is estimated at $155 million annually.