Gastrointestinal nematodes in small ruminants: genus identification and evaluation of anthelmintic resistance in Misiones, Argentina

BackgroundDifferent areas of sheep infected with different types of parasites, all will cause serious harm to the local sheep, and the widespread use and repeated use of anthelmintics have produced different degrees of anthelmintic resistance (AR) in various regions. We re-investigated the infection of common parasites and AR of Gastrointestinal Nematodes (GINs) in sheep in Horqin Right Wing Front Banner, and first investigated the common parasite types and AR of GINs in sheep at other four areas in Hinggan league (city), China.ResultsA total of 1770 fecal samples were collected from 1 prefecture-level city and 4 counties in Hinggan league, in which the infection rate of Coccidia ranged from 83.3% to 96.06%, that of Ascaris ovis ranged from 10.17% to 15.19%, that of Moniezia benedeni ranged from 0.6% to 1%, that of Moniezia expansa ranged from 0.33% to 8.15%. The infection rate of GINs was 100%, and Haemonchus contortus was still the dominant species. The AR results showed that only the closantel in Horqin Right Wing Middle Banner was low resiatant, and the other three regions had been resistant. Levamisole also occurred AR in the other four regions, the widely used ivermectin and albendazole had produced serious AR in five areas. The research shows that GINs are becoming more and more resistant to various anthelmintics, which has made the problem worse.ConclusionsUnderstanding the dynamic changes of parasite infections and the development trend of AR in sheep in the region in this paper, the development trend seems to be more serious than imagined. Therefore only by deeply understanding the parasitic infections of sheep in this land can more reasonable medication guidance be carried out. It is expected to provide new ideas formore innovative, scientific and sustainable methods of preventing and controlling parasites.

Simple SummaryThe spread of helminths resistant to the most common classes of anthelmintic drugs in sheep and the presence of drug residues in the environment has prompted research to find sustainable alternative solutions for gastrointestinal nematodes control. This study reports the results of in vivo studies on the efficacy of an aqueous Punica granatum-based macerate, used in southern Italy for the control of gastrointestinal nematodes in sheep. The anthelmintic efficacy was evaluated in parallel in sheep infected with gastrointestinal nematodes, using, as a positive control, the treatment with Ivermectin and Albendazole. The results of the study show a good anthelmintic efficacy, suggesting the use of this ethnoveterinary macerate as an alternative and sustainable therapeutical remedy for the helminthiasis control in the sheep.Parasites, in particular, gastrointestinal nematodes (GINs) represent one of the main burdens affecting small ruminant farming and pose a serious threat to their health, welfare, productivity, and reproduction. The correct management of animals and the correct use of anthelmintic drugs are the pillars of the GIN control programs for small ruminants. However, globally due to the indiscriminate use of synthetic anthelmintics, there is a significant increase in anthelmintic resistance phenomena to one or more classes of drugs. Even if such a problem never represented a serious threat in southern Italy because of the favourable environmental conditions and because of the good farm management, the phenomenon is actually showing a steep increasing trend and requires alternative treatment measures and constant monitoring. The use of phytotherapies is considered a valuable alternative approach for GIN control in small ruminants and could help with reducing the amount of synthetic drugs used and the forthcoming anthelmintic resistance. From this perspective, the Calabria territory offers a wide number of plants with anthelmintic efficacy that could be helpful for this purpose. The aim of this study was to evaluate the anthelmintic efficacy of aqueous pomegranate (Punica granatum L.) macerate compared to the treatment with Ivermectin and Albendazole in sheep naturally infected with GINs. The pomegranate macerate derives from the ethnoveterinary knowledge of the Calabria region, Southern Italy. The anthelmintic efficacy was evaluated according to the faecal egg count reduction test (FECRt) using the FLOTAC techniques in two sheep farms in Southern Italy. The FECR was calculated from individual samples using the formula FECR = 100 × (1 − [T2/C2]). The treatment with Albendazole in the first farm showed an efficacy of 99.8% after 14 days and 94.8% after 21 days, while the treatment with Ivermectin in the second farm showed an efficacy of 99.9% after 14 days and 96.5% after 21 days of treatment. The pomegranate macerate, in both farms, showed a value of efficacy of around 50% from day 7 to day 21 after the treatment. Previous studies highlighted the presence of gallic acid as the main component in the pomegranate macerate, and its efficacy in nematode control has been as well previously demonstrated in other plant extracts. This in vivo study demonstrated the unequivocal efficacy of plant macerate in easily reducing 50% of the number of GIN eggs in sheep faeces. These results, obtained without the use of synthetic anthelmintics, indicate the use of green veterinary pharmacology as a sustainable alternative to the use of synthetic drugs to reduce the increase in drug resistance phenomena and the environmental impact.

Aim: The present study was aimed to determine the resistance against albendazole, fenbendazole, levamisole and closantel in gastrointestinal (GI) nematodes of sheep. Introduction: Anthelmintics are used traditionally as an integral part of helminthic control strategies for grazing livestock to prevent production losses from parasitic infections. The continuous and indiscriminate use of the same anthelmintics over years together as the sole means of control are now failing due to the emergence of resistance strains of helminths. Resistance to the commonly used anthelmintics in GI nematodes of sheep has become an increasingly widespread problem throughout the world. Materials and Methods: Fifty-five naturally infected Madras Red lambs of 6-12 months of age were selected and distributed randomly into five treatment groups of 11 animals each. Four groups were treated orally with albendazole (5 mg/kg), fenbendazole (7 mg/kg), levamisole (7.5 mg/kg) and closantel (10 mg/kg) respectively, whereas the fifth group served as untreated control. Fecal samples were collected per rectum of each lamb just prior to treatment (pre-treatment) and on 7, 14, 21 and 28 days post-treatment. The anthelmintic resistance was evaluated by in vivo fecal egg count reduction test (FECRT), post-treatment larval culture and in vitro egg hatch assay. Results: In the FECRT, albendazole reduced the faecal egg count by 86.50%, 84.81%, 85.28% and 84.47% respectively for 4 weeks after treatment. Fecal egg count reduction using fenbendazole was 92.64, 93.04, 90.80 and 90.06% respectively for 4 weeks after treatment. The percent efficacy for levamisole and closantel was more than 95%. The post-treatment larval culture contained only Haemonchus contortus. In the in vitro egg hatch assay, the ED50 value for benzimidazole was 0.299 μg albendazole/ml and levamisole showed an ED50 value of 0.283 μg/ml. Conclusion: Our study confirmed the resistance of H. contortus to benzimidazole in sheep.

A systematic review and meta-analysis of factors associated with anthelmintic resistance in sheep

Detection of benzimidazole resistance in gastrointestinal nematodes of sheep and goats of sub-Himalyan region of northern India using different tests

Simple SummaryDifferent types of endoparasites are present in small ruminants, especially in sheep. One of the most important parasites are the gastrointestinal nematodes (Trichostrongylidae). Emaciation, anorexia, decreased productivity, and diarrhea are observed in infected animals. These infections cause great economic damage to sheep owners through production losses and treatment costs. In connection with the frequent treatment of sheep against endoparasite infections, anthelmintic resistance has developed. Due to the global anthelmintic resistance situation, the principles of parasite control have changed. New alternatives have been sought, and one of the most researched alternatives is phytotherapy. Different plants with anthelmintic activity would be valuable for the control of ruminant helminths. Phytotherapy would reduce the use of synthetic drugs and reduce treatment costs.Due to the high prevalence of gastrointestinal nematodes in sheep, the growing anthelmintic resistance, and the development of organic farming systems, sustainable alternatives are being sought. One such method is phytotherapy. This study aimed to evaluate the in vitro ovicidal and larvicidal activity of extracts of tansy (Tanacetum vulgare L.) growing in Latvia on gastrointestinal nematodes (Trichostrongylidae) in sheep. The leaves and flowers of the tansy were extracted separately in 70%, 50%, and 30% ethanol and acetone. Six concentrations were prepared from each extract 500 mg/mL, 200 mg/mL, 100 mg/mL, 50 mg/mL, 20 mg/mL, and 10 mg/mL. In vitro egg hatching test and micro-agar larval development test were performed. Extracts of tansy have strong larvicidal activity. The highest percentage of larvae inhibition for most of the extracts was 100%, but for egg inhibition, it was 95.8% for the 200 mg/mL concentration of 50% acetone and 93.3% for the 500 mg/mL concentration of 50% ethanol leaf extracts. All tansy extracts had ovicidal and larvicidal activity against Trichostrongylidae in sheep.

This study compared results obtained with five different fecal egg count reduction (FECR) calculation methods for defining resistance to ivermectin, fenbendazole, and levamisole in gastrointestinal nematodes of sheep in a temperate continental climate: FECR1 and FECR2 used pre-and posttreatment fecal egg count (FEC) means from both treated and control animals, but FECR1 used arithmetic means, whereas FECR2 used geometric means; FECR3 used arithmetic means for pre- and posttreatment FECs from treated animals only; FECR4 was calculated using only arithmetic means for posttreatment FECs from treated and control animals; and FECR5 was calculated using mean FEC estimates from a general linear mixed model. The classification of farm anthelmintic resistance (AR) status varied, depending on which FECR calculation method was used and whether a bias correction term (BCT, i.e., half the minimum detection limit) was added to the zeroes or not. Overall, agreement between all methods was higher when a BCT was used, particularly when levels of resistance were low. FECR4 showed the highest agreement with all the other FECR methods. We therefore recommend that small ruminant clinicians use the FECR4 formula with a BCT for AR determination, as this would reduce the cost of the FECRT, while still minimizing bias and allowing for comparisons between different farms. For researchers, we recommend the use of FECR1 or FECR2, as the inclusion of both pre- and posttreatment FECs and use of randomly allocated animals in treatment and control groups makes these methods mathematically more likely to estimate the true anthelmintic efficacy.

This study compared results obtained with five different fecal egg count reduction (FECR) calculation methods for defining resistance to ivermectin, fenbendazole, and levamisole in gastrointestinal nematodes of sheep in a temperate continental climate: FECR1 and FECR2 used pre- and posttreatment fecal egg count (FEC) means from both treated and control animals, but FECR1 used arithmetic means, whereas FECR2 used geometric means; FECR3 used arithmetic means for pre- and posttreatment FECs from treated animals only; FECR4 was calculated using only arithmetic means for posttreatment FECs from treated and control animals; and FECR5 was calculated using mean FEC estimates from a general linear mixed model. The classification of farm anthelmintic resistance (AR) status varied, depending on which FECR calculation method was used and whether a bias correction term (BCT, i.e., half the minimum detection limit) was added to the zeroes or not. Overall, agreement between all methods was higher when a BCT was used, particularly when levels of resistance were low. FECR4 showed the highest agreement with all the other FECR methods. We therefore recommend that small ruminant clinicians use the FECR4 formula with a BCT for AR determination, as this would reduce the cost of the FECRT, while still minimizing bias and allowing for comparisons between different farms. For researchers, we recommend the use of FECR1 or FECR2, as the inclusion of both pre- and posttreatment FECs and use of randomly allocated animals in treatment and control groups makes these methods mathematically more likely to estimate the true anthelmintic efficacy.

Anthelmintic resistance in sheep in the semiarid region of Minas Gerais, Brazil.

The article investigates into the species composition of agents causing gastrointestinal tract nematodes in sheep. It determines the forms of nematodes communities. For this purpose, 710 sheep were examined, 79.58% of which were infected. The fauna of nematodes was represented by 15 species of helminths from 12 genera: Bunostomum, Oesophagostomum, Nematodirus, Chabertia, Cooperia, Trichostrongylus, Ostertagia, Haemonchus, Тrichuris, Aonchotheca, Strongyloides, and Skrjabinema. The indicators of infestation intensity in sheep ranged from 1 to 93 specimens per animal, and the abundance index ranged from 0.01 to 16.96 specimens per animal. The most common nematodes are H. contortus (prevalence, 61.97%), O. circumcincta (59.58%), T. colubriformis (57.35%), Т. оvis (55.21%), N. spathiger (49.01%), Oe. venulosum (42.54%), S. ovis (41.13%), Ch. оvina (36.76%), and T. skrjabini (26.34%). Gastrointestinal nematodes in the body of 99.12% of the infected sheep proceeded as parasitic communities. Most frequently, coinvasions were represented by parasitic communities which consisted of five (prevalence, 14.51%), six (19.44%), or seven (15.92%) species. The study revealed 361 varieties of mixed coinvasions. The most frequent comembers were H. contortus, O. circumcincta, T. colubriformis, Т. оvis, N. spathiger, S. ovis, and Ch. оvina. The data obtained provide an opportunity to increase the effectiveness of measures to combat and prevent gastrointestinal tract nematodes in sheep farms.

The study was conducted to investigate the status of anthelmintic (AH) efficacy and associated risk factors for AH resistance in sheep. Questionnaire surveys were undertaken to establish the AH utilization practices of sheep owners at the study area and identify risk factors. Four hundred fourteen sheep were sampled of which 180 sheep were selected based on their higher egg count for the fecal egg count reduction test (FECRT) to assess the efficacy of albendazole, tetramisole and ivermectin against gastrointestinal nematode parasites prevailing in sheep. Fecal culture and postmortem examination techniques were used to identify the species of nematode parasites prevalent before and after treatment. The results show that: 1) albendazole and tetramisole were the most frequently used AH in the area, 2) farmers get the drugs with or without prescription from various sources (10% open markets, 18% private drug stores and 72% government animal health clinics and 3) the prevalence of gastro-intestinal nematode infection in the study areas was 72%. 4) The FECRT revealed all the three tested AH were effective with egg count reduction levels of 96%, 99% and 97% respectively for albendazole, tetramisole and ivermectin. However, post-treatment fecal cultures and postmortem adult worm recovery showed that some Haemonchus contortus worms have escaped the treatments. In conclusion, no anthelmintic resistance was detected from clinical cure point of view but the population of H. contortus that has escaped the treatments deserves further scrutiny as this parasite is the most prolific and highly pathogenic in sheep.Key words: Anthelmintic efficacy, FECRT, Gastrointestinal Nematodes, Risk Factors, Sheep.

A systematic review-meta-analysis of primary research investigating the effect of selected alternative treatments on gastrointestinal nematodes in sheep under field conditions

Gastrointestinal nematodes (GINs) are serious issue for health of wild sheep kept in captivity. Chemically synthesized anthelmintics are regularly used to control these parasites. In recent years anthelmintic resistance and remnant of drugs in animal products leads to use of medicinal plants as alternative to anthelmintics. In current study, the efficacy of aqueous, methanolic and ethanolic dried leaf extracts of medicinal plants Moringa oleifera and Azadirachta indica were tested for in vitro ovicidal and larvicidal activities against Haemonchus, Trichuris, Coccidia and Trichostrongylus; naturally acquired nematodes isolated from wild sheep (Ovis orientalis orientalis). Six concentrations of these plants extract (1.56, 3.13, 6.25, 12.5, 25 and 50 mg/ml) were evaluated using egg hatching assay (EHA) and larval development assay (LDA) in three replicates. To compare treatment effects, untreated and treated (0.1% ivermectin) controls were used. The aqueous, methanolic and ethanolic leaf extracts showed anthelmintic activities against isolated genera of nematodes but the inhibition was maximum (99%) in ethanol extract of M. oleifera followed by methanol extract (97%) at maximum concentration tested at (50mg/ml). The overall findings of this study shows that Moringa oleifera and Azadirachta indica leaf extracts possess significant anthelmintic efficacy against GINs of sheep and these could be a natural alternative to synthetic anthelmintics to treat the worm infections in animals.

Anthelmintic resistance and multidrug resistance in sheep gastro-intestinal nematodes in France, Greece and Italy

Randomized controlled trials—the problem of clinical trials in veterinary science