87. An assessment of the potential use ofCichorium intybus andLotus corniculatus to influence worm burdens in lambs (original) (raw)
Related papers
Veterinary Parasitology, 1991
Resistance to thiabendazole (TBZ), fenbendazole (FBZ) and levamisole (LVM) in naturally acquired gastrointestinal nematode parasites in sheep was investigated on a farm where anthelmintic resistance was suspected. This was measured by both the in vitro egg hatch assay, and reductions in faecal egg and worm counts in treated animals. In the egg hatch assay, nematode eggs were incubated in various concentrations of either TBZ or LVM. The level of resistance was expressed as the drug concentration inhibiting 50% of the eggs from hatching (LC50). The nematode population had LC50 values of 0.26 ltg ml-~ TBZ and 3.12/tg ml-~ LVM. In the faecal egg and worm count reduction test, naturally infected sheep were treated with either TBZ (88 mg kg-J), FBZ (10 mg kg-~) or LVM (15 mg kg-t). Faecal egg and total worm counts from these sheep were then compared with counts from untreated sheep. TBZ, FBZ and LVM failed to reduce the faecal egg counts and total worm counts by more than 90%. Based on the identification of larvae from faecal cultures, the most predominant nematode species in the resistant population were Haemonchus (62%) and Trichostrongylus (28%). TBZ reduced faecal egg counts for both species by less than 90%. FBZ and LVM also reduced Haemonchus spp. eggs by less than 90%. Other nematode species numbers did not satisfy criteria for the determination of efficacy.
Molecular and Biochemical Parasitology, 1990
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 a-and ~-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 c~-and/3-tubulin probes, 2 to 6 different fragments, depending on the restriction enzyme used. The three resistant populations showed as many fragments with the c~-tubulin probe as the susceptible populations, but when probed with ~-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 ~-tubulin probe reactive DNA fragments was reduced from 5 to !. Analysis of the DNA of individual male adults of susceptible populations indicated a heterogeneity among the individual worms regarding the number of ~-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.
In vitro detection of benzimidazole resistance in sheep nematodes of a Bulawayo farm
A study was conducted to ascertain if anthelmintic resistance was the cause of poor clinical response to drugs at a farm in Figtree, Bulawayo.Feacal samples from thirty sheep were collected and sent to the National University of Science and Technology (NUST) laboratory for processing.Coproculture was done to identify the species of parasites present in the sample. Eggs were then isolated using a flotation technique. An Egg Hatch Assay as described by Cole et al (2006) was then performed. An estimated number of eggs was incubated on a 24 well micro titre plate with concentrations of thiabendazole ranging between 0.05 to 0.5 μl/ml.The hatched eggs were then enumerated using an inverted microscope. At 0.05 μl/ml thiabendazole, 94% eggs hatched whereas at 0.5 μl/ml 54% eggs hatched. An LC50 value of 0.54 μl/ml was obtained. This indicated benzimidazole resistance at the farm which could have contributed to poor clinical response to drugs.
The Veterinary Journal, 2010
This is the first report of benzimidazole (BZ) resistance in the nematode Trichostrongylus axei in sheep. Trichostrongylus axei infects several species of herbivores including sheep, cattle and horses, and the emergence of anthelmintic resistance could lead to significant problems in its control. Benzimidazole resistance in two sheep flocks in central France was detected by post-treatment worm counts. The sequencing of a central region of the isotype 1 b-tubulin gene from adult T. axei recovered post-mortem revealed only one, non-synonymous single nucleotide polymorphism at position 200 (Phe200Tyr), which had already been reported for other nematodes. Seven years after BZ treatment ceased, T. axei helminths present were still resistant to BZ suggesting these parasites do not revert to susceptibility to this anthelmintic, even when the selection pressure had been removed for many years. The findings also highlight major changes in the make-up of the nematode burden in sheep flocks that accompanies the emergence of BZ resistance.
Experimental Parasitology, 2004
The relationship between the pharmacokinetic behaviour and the anthelmintic efficacy of albendazole (ABZ) against benzimidazole (BZD)-resistant nematodes was studied in sheep. A micronized ABZ suspension was orally administered at two different dose levels to sheep naturally infected with BZD-resistant gastrointestinal (GI) nematodes. The experimental animals were allocated into the following groups (n ¼ 8): (a) untreated control; (b) orally treated with ABZ at 3.8 mg/kg b.w.; and (c) orally treated with ABZ at 7.5 mg/kg b.w. Plasma samples were obtained serially over 72 h post-treatment from both treated groups and analysed by HPLC to measure the concentrations of ABZ and its sulphoxide (ABZSO) and sulphone (ABZSO 2 ) metabolites. Faecal egg counts were performed prior to treatment and at the necropsy day. All experimental animals were sacrificed 10 days after treatment to perform GI worm counts. While ABZ parent drug was not recovered in the bloodstream, ABZSO and ABZSO 2 were the molecules found in plasma. ABZSO was the metabolite measured at the highest concentrations in the bloodstream for up to 36 (treatment at 3.8 mg/kg) or 60 h (treatment at 7.5 mg/kg) post-administration. There was a proportional relationship between the administered ABZ dose and the measured plasma concentrations of both ABZ metabolites. Over a 100% increment on the plasma AUC values for the anthelmintically active ABZSO metabolite was observed at the 7.5 mg/kg compared to the 3.8 mg/kg treatment. The low efficacy patterns (<24%) observed against the GI nematodes investigated indicate a high level of resistance to ABZ given at 3.8 mg/kg an efficacious therapeutic dose rate recommended in some countries. However, the higher and prolonged plasma drug concentration measured after the 7.5 mg/kg treatment resulted in an improved efficacy pattern (estimated by both faecal egg and adult worm counts) against most of the GI nematodes studied compared to that obtained at the lower dose rate. A direct relationship between drug pharmacokinetic behaviour and anthelmintic efficacy against BZD-resistant nematodes in sheep was shown in the current work, although individual variation precluded the observation of statistically significant differences in worm counts.
Veterinaria México OA, 2016
Sheep production requires the constant assessment of parasitic burden and the efficacy of existing treatments for proper management. In this study, the administration of five different treatments was evaluated for the reduction of the percentage of eggs per gram of feces (EPG) shed by gastrointestinal nematodes (GIN) from sheep on three different sheep-breeding farms in Mexico (Texcoco, Estado de Mexico; Hueytamalco, Puebla; and Tlaltizapán de Zapata, Morelos). In these farms, ivermectin and benzimidazole derivatives had been routinely administered for two consecutive years. To determine whether drugs with different pharmacological properties decreased GIN fecal egg excretion, the treatments closantel (CLOS), albendazole (ABZ) and fenbendazole (FBZ) were administered alone and in combinations of CLOS + ABZ and CLOS + FBZ, to five groups of sheep, with an additional untreated control group on each farm (n = 28 per flock). Anthelmintic resistance was determined using Fecal Egg Count Reduction Tests (FECRT) as recommended in the guidelines of the World Association for the Advancement of Veterinary Parasitology. Fecal samples were collected 14 and 21 days after treatment. The anthelmintic resistance status was determined based on the reduction in the fecal egg count arithmetic mean and 95 % confidence limits. According to the FECRT, resistance developed to CLOS, ABZ, FBZ and CLOS + FBZ because the mean percentage of EPG reduction was ≤ 95 % with a lower confidence limit of ≤ 90 %. By contrast, nematode susceptibility was confirmed for the CLOS + ABZ combination, as it reduced the percentage of GIN fecal egg output by 96.46 ± 3.04 % (day 14) and 96.88 ± 3.04 % (day 21). Based on the morphometric identification of larvae, Haemonchus spp., Cooperia spp. and Teladorsagia spp. were the most abundant genera on all farms before the administration of these five treatments. In conclusion, the use of the anthelmintic combination of closantel plus albendazole may reduce the development of anthelmintic resistance in gastrointestinal nematodes.
Worm burdens in cows: the effect of anthelmintic treatment on the parasite egg output
Veterinary Parasitology, 1982
. Worm burdens in cows: the effect of anthelmintic treatment on the parasite egg output. Vet. Parasitol., The effect on the nematode egg output of anthelmintic treatment with levamisole after parturition was studied in a group of 298 cows on four farms in the province of Groningen, and three farms in the province of Noord-Brabant (The Netherlands). Two faecal samples were taken, the first within 48 h post partum, and the second 14 days later. Half the number of cows were treated after the first sampling. Faecal examinations were made by culturing a fixed amount of faeces, counting the larvae, calculating an LPG (number of larvae per g of faeces) and making a larval differentiation. From the first sampling it became clear that with some exceptions egg output was generally low (mean LPG 7.9). Most of the cows (87.9%) were positive for Ostertagia spp. Of the other species, Trichostrongylus spp. were found in 47.7% of the samples and Cooperia puncatata in 30.5%. Less frequent were Bunostomum phlebotomum (13.1%), Oesophagostomum spp. (9.4%), Cooperia oncophora/surnabada (8.7%) and Haernonchus contortus (7.7%). The latter species was only found on farms in Noord-Brabant and was related to the grazing of sheep on the cattle pastures. In more than 60% of the cows in both provinces with an LPG-value above 20, C. oncophora/surnabada larvae were present, while H. contortus larvae were found in 50% of those cows in Noord-Brabant. Highest counts were generally observed in cows lactating for the first time,,but sometimes individual cows of older age showed a high egg output. The highest LPG-value found in this study was 228, in a first-lactating cow. The second sample of treated animals, 14 days after the first, showed that the LPG was significantly reduced from 7.6--1.4 (P < 0.001 ), while in the non-treated cows the reduction of the LPG was from 6.7--6.1, which proved to be not significant. However, all species seen prior to treatment were still present after treatment. 0304-4017/82/0000--0000]$02.75
Journal of Helminthology, 2001
The occurrence of benzimidazole (BZ) and levamisole resistance was investigated in 18 randomly selected dairy goat herds located in southwestern France and characterized by extensive management. On each of the 18 farms, 45 adult goats were randomly allocated into three groups of 15 animals each: an untreated control group, a group that was orally administered fenbendazole (10 mg kg-1 body weight) and a group that received orally a levamisole drench (12 mg kg-1 body weight). Individual faecal egg counts and pooled larval cultures were done 10 days after anthelmintic treatment. Naive lambs were infected with larvae obtained from control and fenbendazole treated groups and were necropsied 35 days after infection for worm recovery. Faecal egg count reductions (FERC) were calculated for fenbendazole and levamisole and, when less than 95 per 100, were considered as indicative of anthelmintic resistance. An in vitro egg hatch test (EHT) was conducted with thiabendazole on eggs isolated fro...
Veterinary Research, 2004
In an experiment lasting 4 years, changes in the Teladorsagia circumcincta and Trichostrongylus colubriformis populations were compared in lambs and adult sheep with differing resistance statuses. Two flocks of 30 rams (resistant R and susceptible S) grazed separate pastures and 8 rams were slaughtered in the middle and at the end of each grazing season. Five groups of tracer lambs were added each year to estimate the pasture infectivity and were killed for worm counts. The availability of animals with differing resistance statuses (rams and tracer lambs) and differing levels of infection made it possible to investigate the number, size and fecundity of worms of these two species. The inflammatory response was measured in the rams by counting the globule leukocytes, mast cells and eosinophils in the fundic, pyloric and intestinal mucosa. In the tracer lambs, the daily egg production by the female worms of both species was negatively correlated with the worm burden. Worm length accounted for 60 and 70% of the variation in the number of eggs in utero for T. circumcincta and T. colubriformis respectively. Worm length was closely associated with the resistance status of the host; there were greater differences between lambs, and S and R rams for T. colubriformis. T. circumcincta worm lengths were not affected by the worm number. Globule leukocyte counts were related to the worm burdens, and mast cell counts to worm length in the R and S rams. The number, size and fecundity of the worms may well be regulated by similar mechanisms in both species, but T. colubriformis seemed to be more intensively regulated than T. circumcincta. This finding could be useful in devising more effective methods of parasite control.