[Lung worm control in calves during the 1996 pasture season].
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Animals↗
Biomedical subjects
F H Borgsteede
Publications and source records attributed to F H Borgsteede.
Coccidial and helminth infections in goats kept indoors in the Netherlands.
An investigation was carried out on coccidial and helminth infections in goats kept indoors on five farms in the Netherlands. The goats were individually sampled. Coccidial oocysts were identified and nematode eggs counted. Larval cultures were made and infective larvae identified to the generic or species level. The goats were divided into three groups according to their age: kids, those weaned but not served, and older goats. Oocysts were found in 26 out of 27 kids (96.3%), in 52 out of 55 weaned but not served goats (94.5%), and in 72 out of 110 older goats (65.5%). Eimeria ninakohlyakimovae was the most common species in all groups with an overall prevalence of 82%, followed by Eimeria arloingi (78%) and Eimeria aspheronica (53.3%). Other species present were Eimeria alijevi (50%), Eimeria christenseni (39.3%), Eimeria caprina (38.7%), Eimeria hirci (28.7%) and Eimeria jolchijevi (7.3%). Nematode eggs were seen on four of the five farms. It appeared that on two farms some goats, although now kept indoors, had been on pasture in the past. These goats excreted low numbers of eggs of Ostertagia and/or Trichostrongylus, Strongyloides papillosus, Haemonchus contortus, Trichuris spp. and larvae of Muellerius capillaris. In goats that were kept exclusively indoors, infections with Strongyloides papillosus were found on two farms in the older group and on one farm also in the group weaned but not served. On two farms Skrjabinema ovis was incidentally observed by the farmer in older goats. This was confirmed by faecal examinations on one farm. All kids were free of nematode infection.
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Workshop summary: anthelmintic resistance.
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Animals↗
Data on the prevalence of tapeworm infestations in horses in The Netherlands.
The prevalence of tapeworm infestations was investigated in 70 horses slaughtered in the period February 1994-July 1994. Most horses were half-breed, young (1.5-3 years), and in good condition. They were bought for slaughter by dealers on local markets, and their treatment history was therefore unknown. Tapeworm infestations were seen in 16 horses (23%). Fifteen (21%) had an infection with Anoplocephala perfoliata. One horse had a single specimen of Paranoplocephala mamillana. The average number of A. perfoliata was 45 and the highest number was 508.
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The effect of parasites on wildlife.
Populations of animals which live in the wild are regulated by many biotic and abiotic factors. Parasites are one of the biotic factors. Parasites may influence their hosts in different ways. They may cause the death of the host due to a direct lethal effect or an indirect effect. Direct lethal effects may occur if killing is a part of the life cycle of the parasite or if hosts and parasites have not developed an equilibrium. The introduction of hosts or parasites into a new environment with suitable hosts or parasites is an example. Death by parasitism may also be caused by a combination of the emaciating effects of parasites combined with factors such as bad weather conditions, environmental pollution or human handling. Parasites may also influence the behaviour of their hosts. If the hosts are intermediate hosts in the life cycle of the parasites, the alterations in behaviour may make them an easier prey for their predators, the final hosts. Parasites may also influence the reproductive success of the hosts. In this respect the relationship between the red grouse (Lagopus lagopus scoticus) and the caecal nematode Trichostrongylus tenuis has been well worked out.
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[Anthelmintic resistance in sheep nematodes in The Netherlands].
The prevalence of anthelmintic resistant nematodes in sheep was investigated in 1994 with a faecal egg count reduction test (FECRT) and an egg hatch assay (EHA) on 71 farms in the Netherlands. A benzimidazole (oxfendazole) was tested on 70 farms, ivermectin on 51 farms, and levamisole on 35 farms. Based on the FECRT benzimidazole resistance was present on 56 farms, 2 were suspected, on 9 no resistance was observed, while 3 farms could not be tested due to a too low egg output before treatment. No clear indications for resistance to ivermectin and levamisole were found. Benzimidazole resistance was demonstrated in Haemonchus contortus, Cooperia curticei, Ostertagia spp. and/or Trichostrongylus spp. No resistance was seen in species from the genus Nematodirus, Chabertia ovina and/or Oesophagostomum spp. De results of the EHA confirmed the results of the FECRT. On 59 farms the ED50 value was > 0.12 microgram ml-1 thiabendazole.
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The reappearance of strongyle eggs in faeces of horses treated with pyrantel embonate.
The reappearance of strongyle eggs in the faeces of horses treated with pyrantel embonate was studied. The horses (103) were divided in 11 groups on 8 different farms. The efficacy of pyrantel embonate against strongyles, based on egg count reduction tests, was 99.8%. Mean weekly egg counts performed between week 2 and week 9 after treatment showed that 5 weeks after treatment the egg output passed the 90% reduction level. It is concluded that strategic treatments of horses with pyrantel embonate for the prevention of strongylosis should be administered with intervals of 6 weeks.
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Recommendations for the control of anthelmintic resistant nematodes of farm animals in the EU.
As a result of a recent European Union meeting on anthelmintic resistant nematodes of farm animals, a list was made of nine proposals for research and five to control anthelmintic resistance. The most important were the need to have standardised and new tests to monitor the development and spread of resistant nematodes in sheep, goats, horses, cattle and pigs, and for education of veterinary surgeons and farmers in the optimal control strategies to be used to delay the development of anthelmintic resistance in nematodes.
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The efficacy and persistent anthelmintic effect of ivermectin in sheep.
The direct efficacy and the long-term persistent anthelmintic effect of an oral suspension and an injectable formulation of ivermectin at a dose rate of 0.2 mg kg-1 was studied in sheep. Lambs were infected experimentally with Haemonchus contortus, Trichostrongylus vitrinus and Cooperia curticei. After 3 weeks they were treated with an oral suspension or with an injection, and reinfected with the same dose of larvae 3, 6 or 10 days after treatment. Post-mortem worm counts showed no persistent effect of the oral suspension. The injectable formulation showed an excellent persistent effect for up to 10 days against H. contortus. Reinfection with C. curticei 3 days after treatment resulted in a 64% reduction of the worm burden, but reinfection after 6 and 10 days was 100% reduced. The reduction of T. vitrinus was 46% after 3 days and 92% after 6 and 10 days.
Administration, Oral↗
The reappearance of eggs in faeces of horses after treatment with ivermectin.
The reappearance of nematode eggs in faeces after ivermectin treatment was studied in 104 horses on 10 farms during the stabling period. Faecal samples were taken at weekly intervals. Sampling was discontinued when the mean egg output per farm was > 10% of the pre-treatment egg output. This point was reached after 63 days, when the mean output of eggs had decreased to 70.3%. Before treatment, 95.9% of the cultured larvae were of the cyathostome type, the others belonged to Gyalocephalus capitatus, Strongylus vulgaris, S. edentatus, Oesophagodontus/Poteriostomum spp., Triodontophorus spp. and Trichostrongylus axei. After treatment, the cultures nearly always produced 100% cyathostome larvae, although occasionally low numbers (< 1%) of larvae of large strongyles (mainly S. edentatus, rarely S. vulgaris and Oesophagodontus spp.) and T. axei were seen.
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[Ascaris suum infection as a cause of clinical problems in cattle?].
A sudden decrease in milk yield, increased respiratory rate and occasional coughing were observed in dairy cows on two farms in spring 1991. Pigs were also kept on these farms, and pastures grazed by the cattle had been fertilised with pig slurry. Laboratory investigations of some of the cattle showed eosinophilia and high ELISA titres of antibodies against Ascaris suum. On one farm the clinical symptoms disappeared after the animals had been treated with oxfendazole and on the other farm the symptoms disappeared spontaneously with time.
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Studies on an Ostertagia ostertagi strain suspected to be resistant to benzimidazoles.
Four calves were infected with a susceptible (laboratory) strain of Ostertagia ostertagi and four with a field strain suspected to be resistant to benzimidazoles. After 25 days two calves from each group were treated with 3.5 mg kg-1 fenbendazole. Egg output fell to zero in all treated calves. Treated calves did not harbour worms at slaughter 35 days after infection. Significant differences between the strains were shown for ED50 values for thiabendazole in the egg hatch assay, but not in the tubulin binding assay. It is concluded that benzimidazole resistance in the suspected strain cannot be confirmed.
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World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) methods for the detection of anthelmintic resistance in nematodes of veterinary importance.
Methods have been described to assist in the detection of anthelmintic resistance in strongylid nematodes of ruminants, horses and pigs. Two tests are recommended, an in vivo test, the faecal egg count reduction test for use in infected animals, and an in vitro test, the egg hatch test for detection of benzimidazole resistance in nematodes that hatch shortly after embryonation. Anaerobic storage for submission of faecal samples from the field for use in the in vitro test is of value and the procedure is described. The tests should enable comparable data to be obtained in surveys in all parts of the world.
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Increase of anthelmintic resistance in sheep in The Netherlands.
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Animals↗
Further studies with a strain of Ostertagia ostertagi resistant to morantel tartrate.
Two experiments with a morantel resistant strain of Ostertagia ostertagi were carried out. In the first experiment five groups of five calves were infected with 60,000 larvae of this resistant strain. Calves of one group remained untreated, calves of the other groups were treated with morantel tartrate, oxfendazole, levamisole or ivermectin in the recommended doses. It was demonstrated that there was side resistance to levamisole, but not to oxfendazole or ivermectin. Compared with the untreated controls the reduction percentages of the worm burdens were 45.3 (morantel tartrate), 99.7 (oxfendazole), 83.5 (levamisole) and 100 (ivermectin). In the second experiment a comparison was made between the effect of levamisole against a morantel susceptible strain of O. ostertagi and the resistant strain. Two groups of five calves were infected with the susceptible strain and two groups with the resistant one. One group of each pair remained untreated, the other was treated with levamisole. The reduction percentages of the worm burdens were 99.6 (susceptible strain) and 63.6 (resistant strain). This result confirms the efficacy of levamisole to susceptible O. ostertagi and the side resistance of the morantel resistant strain.
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The prevalence of anthelmintic resistance of horse strongyles in The Netherlands.
A survey to determine the prevalence of anthelmintic resistance of horse strongyles was carried out with 616 horses on 22 farms. The tested drugs were cambendazole, pyrantel pamaote and ivermectin. Based on egg count reduction tests the efficacy of cambendazole varied from 0% to 93% and of pyrantel from 93% to 100%. Ivermectin treatments were 100% effective on all farms. Larval cultures after cambendazole treatments revealed exclusively cyathostome larvae. After pyrantel treatments besides cyathostome larvae other types of larvae were also found. After ivermectin treatments only a few cyathostome larvae were observed. It can be concluded that benzimidazoleresistance of cyathostomes is very common and widespread in the Netherlands. This means that benzimidazoles and pro-benzimidazoles should be excluded for strategic use in horses.
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[Dictyocaulus species, lungworms in cattle and deer in The Netherlands].
Using recent descriptions of Dictyocaulus species, all samples of lungworms in cattle were identified as D. viviparus, and all samples from roe deer, red deer and reindeer being identified as D. eckerti by the present authors. Although cross infections between cattle and cervids are reported in the literature, these are not readily established. Because of the different species and the small likelihood of cross infections cattle and cervids are not regarded as serious sources of lungworm infections for each other. As the description of D. noerneri is based on very scanty information and it is not entirely impossible that it could have been D. viviparus, it is regarded as a species inquirenda. The correct name of the large lungworm of cervids is D. eckerti.
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Molecular analysis of selection for benzimidazole resistance in the sheep parasite Haemonchus contortus.
The molecular basis for the resistance of the sheep parasitic nematode Haemonchus contortus to the benzimidazole (BZ) group of anthelmintics was investigated. Three BZ-susceptible and three resistant populations from different geographical locations were characterized with respect to the egg-hatch assay with thiabendazole (TBZ), mebendazole (MBZ) binding tests and restriction fragment length polymorphism (RFLP) after Southern blotting. Cloned H. contortus alpha- and beta-tubulin genes were used as probes to analyze the RFLPs of genomic DNA prepared from mixtures of infectious larvae (L3) or adults. The susceptible populations showed, with both alpha- and beta-tubulin probes, 2 to 6 different fragments, depending on the restriction enzyme used. The three resistant populations showed as many fragments with the alpha-tubulin probe as the susceptible populations, but when probed with beta-tubulin only 1 or 2 fragments were visible, but always less than in the susceptible populations. An in vitro selection experiment was carried out using a susceptible population that was isolated in the laboratory before BZ came on the market. The results showed that after two selections with increasing amounts of TBZ, the population had become resistant, according to the egg-hatch assay values and MBZ binding assay. Using RFPL, the number of beta-tubulin probe reactive DNA fragments was reduced from 5 to 1. Analysis of the DNA of individual male adults of susceptible populations indicated a heterogeneity among the individual worms regarding the number of beta-tubulin probe reactive fragments (1 to 4) and frequency of the specific fragments. Usually, only one specific fragment (9 kb) was found in the resistant individuals. This 9-kb fragment was already present in some individuals in the susceptible population although it was in combination with other fragments. This would imply that genes conferring BZ resistance were present in H. contortus populations before BZ came on the market, and could explain the fast selection for BZ resistance in the field.
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