Susceptible trichostrongyloid species mask presence of benzimidazole-resistant Haemonchus contortus in cattle.

BACKGROUND: Benzimidazole (BZ) anthelmintics are widely used to control infections with parasitic nematodes, but BZ resistance is an emerging threat among several nematode species infecting humans and animals. In Sudan, BZ-resistant Haemonchus contortus populations were recently reported in goats in South Darfur State. The objective of this study was to collect data regarding the situation of BZ resistance in cattle parasitic nematodes in South Darfur using phenotypic and molecular approaches, besides providing some epidemiological data on nematodes in cattle. METHODS: The faecal egg count reduction test and the egg hatch test (EHT) were used to evaluate benzimidazole efficacy in cattle nematodes in five South Darfur study areas: Beleil, Kass, Nyala, Rehed Al-Birdi and Tulus. Genomic DNA was extracted from pools of third-stage larvae (L3) (n = 40) during trials, before and after treatment, and pools of adult male Haemonchus spp. (n = 18) from abattoirs. The polymorphisms F167Y, E198A and F200Y in isotype 1 ß-tubulin genes of H. contortus and H. placei were analysed using Sanger and pyrosequencing. RESULTS: Prevalence of gastro-intestinal helminths in cattle was 71% (313/443). Reduced albendazole faecal egg count reduction efficacy was detected in three study areas: Nyala (93.7%), Rehed Al-Birdi (89.7%) and Tulus (88.2%). In the EHT, EC50 values of these study areas ranged between 0.032 and 0.037 µg/ml thiabendazole. Genus-specific PCRs detected the genera Haemonchus, Trichostrongylus and Cooperia in L3 samples collected after albendazole treatment. Sanger sequencing followed by pyrosequencing assays did not detect elevated frequencies of known BZ resistance-associated alleles in codon F167Y, E198A and F200Y in isotype 1 ß-tubulin gene of H. placei (≤ 11.38%). However, polymorphisms were detected in H. contortus and in samples with mixed infections with H. contortus and H. placei at codon 198, including E198L (16/58), E198V (2/58) and potentially E198Stop (1/58). All pooled L3 samples post-albendazole treatment (n = 13) were identified as H. contortus with an E198L substitution at codon 198. CONCLUSIONS: To the knowledge of the authors, this is the first report of reduced albendazole efficacy in cattle in Sudan and is the first study describing an E198L substitution in phenotypically BZ-resistant nematodes collected from cattle.

Natural resistance to worms exacerbates bovine tuberculosis severity independently of worm coinfection.

Pathogen interactions arising during coinfection can exacerbate disease severity, for example when the immune response mounted against one pathogen negatively affects defense of another. It is also possible that host immune responses to a pathogen, shaped by historical evolutionary interactions between host and pathogen, may modify host immune defenses in ways that have repercussions for other pathogens. In this case, negative interactions between two pathogens could emerge even in the absence of concurrent infection. Parasitic worms and tuberculosis (TB) are involved in one of the most geographically extensive of pathogen interactions, and during coinfection worms can exacerbate TB disease outcomes. Here, we show that in a wild mammal natural resistance to worms affects bovine tuberculosis (BTB) severity independently of active worm infection. We found that worm-resistant individuals were more likely to die of BTB than were nonresistant individuals, and their disease progressed more quickly. Anthelmintic treatment moderated, but did not eliminate, the resistance effect, and the effects of resistance and treatment were opposite and additive, with untreated, resistant individuals experiencing the highest mortality. Furthermore, resistance and anthelmintic treatment had nonoverlapping effects on BTB pathology. The effects of resistance manifested in the lungs (the primary site of BTB infection), while the effects of treatment manifested almost entirely in the lymph nodes (the site of disseminated disease), suggesting that resistance and active worm infection affect BTB progression via distinct mechanisms. Our findings reveal that interactions between pathogens can occur as a consequence of processes arising on very different timescales.

Prevalence of anthelmintic resistance of gastrointestinal nematodes in Polish goat herds assessed by the larval development test.

BACKGROUND: Helminthic infections, in particular those caused by gastrointestinal nematodes (GIN), are found worldwide and are among the most economically important diseases of goats. Anthelmintic resistance (AR) in GIN of goats is currently present worldwide, and single- or multidrug resistant species are widespread. The aim of this study was to determine the prevalence of AR to benzimidazoles (BZ), macrocyclic lactones (ML) and imidazothiazoles represented by levamisole (LEV) in the Polish goat herds by using an in vitro larval development test, which is useful especially in large-scale epidemiological surveys. RESULTS: This cross-sectional study was conducted from September 2018 to June 2019 and enrolled 42 dairy goat herds scattered over the entire country. The most commonly used anthelmintic class in goat herds in Poland were BZ (92%), followed by ML (85%) and LEV (13%). BZ-resistant GIN populations were found in 37 herds (88%, CI 95%: 75 to 95%), ML-resistant GIN populations in 40 herds (95%, CI 95, 84 to 99%), and LEV-resistant GIN populations in 5 herds (12%, CI 95%: 5 to 25%). Multidrug resistance involving all three anthelmintic classes was found in 5 herds (12%, CI 95, 5 to 25%). Based on the morphological features of stage 3 larvae the main resistant GIN turned out to be Haemonchus contortus and Trichostrongylus spp. The use of BZ and frequency of anthelmintic treatments were significantly related to the presence of AR to BZ in Polish goat herds. CONCLUSIONS: This cross-sectional study demonstrates the existence of AR to BZ, ML and LEV on Polish goat farms. Resistance to BZ and ML is widespread, while AR to LEV is currently at a low level. A considerable proportion of herds harbours multidrug resistant GIN, which requires further consideration. An effective anthelmintic treatment strategy, reasonable preventive measures and better understanding of the resistance-related management practices by farmers and veterinarians may delay further development of AR.

The threat of reduced efficacy of anthelmintics against gastrointestinal nematodes in sheep from an area considered anthelmintic resistance-free.

BACKGROUND: The worldwide increased difficulty to combat gastrointestinal nematode (GIN) infection in sheep, due to progressing anthelmintic resistance (AR), calls for an enhanced and standardized implementation of early detection of AR. This study provides a snapshot of the current AR status against benzimidazoles and macrocyclic lactones in southern Italy, generated with standardized techniques. METHODS: On 10 sheep farms, the efficacy of albendazole (ALB) and either eprinomectin (EPR) or ivermectin (IVM) was evaluated based on the faecal egg count reduction test (FECRT) performed with the Mini-FLOTAC. For each tested drug, 40 sheep were rectally sampled at D0 and sampled again 14 days after the treatment (D14). The FECRT was calculated from individual samples and pooled samples which consist of 5 individual samples. Efficacy was classified as 'reduced, 'suspected' and 'normal'. Coprocultures were set for D0 and D14 faecal samples of each group. From farms with FECR < 95%, an in vitro egg hatch test (EHT) and a follow-up FECRT using fenbendazole (FBZ) were conducted. RESULTS: Based on the FECR, high efficacy (from 95.7% to 100%) was observed for ALB and IVM in eight farms (Farms 3-10). On Farm 1 and Farm 2, the efficacy for the macrocyclic lactones was classified as 'normal', but 'reduced' efficacy was observed for ALB on Farm 1 (FECR = 75%) and 'suspected' efficacy on Farm 2 (FECR = 93.3%) with the predominant GIN genus Trichostrongylus followed by Haemonchus at D14. The FEC results of pooled samples strongly correlated with those of individual samples, for FEC at D0 (rs = 0.984; P < 0.0001) and at D14 (rs = 0.913; P < 0.0001). The classifications of efficacy in Farm 1 (FECR = 86.0%) and Farm 2 (FECR = 93.0%) in the follow-up FECRT with FBZ coincide with the main FECRT trial. The in vitro EHT confirmed AR in both farms (Farm 1: 89%; Farm 2: 74%). CONCLUSIONS: In regions like southern Italy, where the negative impacts from AR have played a minor role, efficient monitoring of AR is important in order to evaluate potential risks and being able to promptly respond with countermeasures.

Chemical characterization and in vitro biological activity of Cymbopogon citratus extracts against Haemonchus spp. and Trichostrongylus spp. nematodes from sheep.

Medicinal plants have been the focus of several studies due to their nematicide properties which can be used to control nematodes in sheep. No study has examined the morphological effects of Cymbopogon citratus on nematodes. Thus, this study evaluated the chemical composition, nematicidal activity and effects of C. citratus extracts on the morphology of eggs and infective larvae (L3) of sheep. Aqueous and methanolic extracts and fractions of C. citratus were obtained and analysed in vitro. The C. citratus extracts were effective against Haemonchus spp. and Trichostrongylus spp. larvae and eggs. Ten fractions were obtained from C. citratus, six of which had high ovicidal activity at 1000 µg mL-1, and two fractions had high activity at all tested concentrations. The phytochemical analysis identified the presence of compounds such as terpenoids, various ketones, esters, and fatty acids. The ultrastructural analysis showed deformations of the cuticle and wilting along the body of the nematodes at all concentrations. The muscular layer, intestinal cells and the mitochondria profile showed damage compared to the typical pattern. Ultra-thin sections of eggs treated with methanolic fractions of C. citratus presented modifications. This study showed the biological activity and effects of C. citratus on the gastrointestinal nematodes in sheep.

Ellagitannins Inhibit the Exsheathment of Haemonchus contortus and Trichostrongylus colubriformis Larvae: The Efficiency Increases Together with the Molecular Size.

Worldwide, parasitic gastrointestinal nematodes continue to threaten animal health, welfare, and production in outdoor breeding systems of small ruminants. For more than 50 years, the control of these parasitic worms has relied on the use of commercial synthetic anthelmintics. However, anthelmintic resistance in worm populations is nowadays widespread and requires novel solutions. The use of tannin-rich plants has been suggested as an alternative to synthetic anthelmintics to control gastrointestinal nematodes. The majority of previous studies have focused on the activity of proanthocyanidins (syn condensed tannins), and less is known about ellagitannins. In this study, the effects of 30 structurally unique ellagitannins on the exsheathment of third-stage infective larvae were examined on Haemonchus contortus and Trichostrongylus colubriformis by the in vitro larval exsheathment inhibition assay. Ellagitannins were found to be promising natural anthelmintics as they showed direct inhibition on larval exsheathment for both nematode species. In general, ellagitannins were more efficient at inhibiting the exsheathment of H. contortus larvae than those of T. colubriformis. The efficiency of inhibition increased as the degree of oligomerization or the molecular weight of the ellagitannin increased. Otherwise, we found no other structural features of ellagitannins that significantly affected the anthelmintic activity on the third-stage infective larvae. The effective concentrations were physiologically relevant and should be achievable in the gastrointestinal tract also in in vivo conditions.

Multiple anthelmintic resistance in gastrointestinal nematodes of small ruminants in Bangladesh.

Anthelmintic resistance (AR) against gastrointestinal nematodes (GINs) of sheep and goats is a global concern. To address the problem, this study assessed the status of AR in different government and private sheep and goat farms in Bangladesh. We conducted fecal egg count reduction test (FECRT) and Egg hatch assay (EHA) experiments. For the detection of resistant larvae, pooled fecal samples from treated and non-treated groups were subjected to coproculture. Furthermore, 195 adult Haemonchus parasites were genotyped to ascertain benzimidazole (BZ) resistance allele from seven topographic zones of Bangladesh using allele specific PCR (AS-PCR). In FECRT, the percentage reduction along with 95% confidence intervals indicated that GINs were resistant to albendazole (ABZ), levamisole (LEV) and ivermectin (IVM). Coproculture revealed that Haemonchus spp., Oesophagostomum spp. and Trichostrongylus spp. were resistant to anthelmintics. ABZ resistance was also confirmed by in vitro EHA in all the farms except the private goat farm in Mymensingh. The genotype frequencies were 6% for homozygous resistant (rr), 59% for heterozygous (rS) and 35% for homozygous susceptible (SS) among different topographic zones. The allelic frequency of the mutation conferring resistance (r) ranged from 25% to 47% signifying resistance to BZ in nematodes of sheep/goats. The genotype frequencies (rr, rS and SS) and allelic frequencies (r and S) varied significantly (p˂0.05) in different zones in Bangladesh. Overall, the data suggest an alarming condition created by multiple AR in Bangladesh.

Optimal age of Trichostrongylus colubriformis larvae (L3) for the in vitro larval exsheathment inhibition test under tropical conditions.

This study identified the optimal age of Trichostrongylus colubriformis larvae (L3) under tropical conditions for the in vitro evaluation of plant extracts using the larval exsheathment inhibition test (LEIT). Two T. colubriformis isolates with different anthelmintic (AH) susceptibility status were used for this study. The L3 of both isolates were maintained on refrigeration (4-5 °C) until use. For the LEIT, the isolates were tested every week during 16 weeks, using a stock solution of Acacia pennatula acetone:water extract at different dilutions (80-1200 µg/mL). Respective positive controls (levamisole 12.5 mM) and negative controls (PBS) were included. Effective concentrations 50 % (EC50), 90 % (EC90) and respective 95 % confidence intervals (95 %CI) for exsheathment inhibition were calculated at 60 min after exposure to chlorine solution. Motility of L3 (migration percentages (M%)) was recorded weekly using the larval migration test (LMT) as an indicator of L3 fitness over time. No correlation was found between L3 age or M% and the extract's EC50 or EC90 values. However, the EC50 values for the A. pennatula extract ranged from 80 to 200 µg/mL from weeks 2-10. Beyond week 12, larval exsheathment was irregular, with higher EC50 and EC90 values and wider 95 %CI. The M% decreased below 85 % on week 7 for Paraiso isolate, and on week 10 for FMVZ isolate. A linear negative relationship was observed between the age of L3 and M% for both T. colubriformis isolates. The relationship (slope) for both isolates was similar therefore a single linear equation was estimated describing all M% data (r2 = 0.771, df = 164, P < 0.05). Thus, when using these T. colubriformis isolates under our tropical conditions for the evaluation of AH activity of plant extracts with LEIT, the optimal age of L3 is between weeks 2-7, when M% remained above 85 %. The latter may ensure consistent and reproducible exsheathment results for T. colubriformis. Each laboratory must identify optimal conditions to perform the LEIT.

Are Trichostrongylus tenuis control and resistance avoidance simultaneously manageable by reducing anthelmintic intake by grouse?

Benzimidazole-based anthelmintics bound to grit (medicated grit) are annually prescribed on request by veterinary practices to grouse managers to control Trichostrongylus tenuis an intestinal parasite of red grouse Lagopus lagopus scotica Those prescribing medication typically do without knowledge of parasite loads and hence often prescribe when loads are low and unlikely to impact the host. Inappropriate use of anthelmintics in livestock has led to development of parasite resistance to anthelmintics. To encourage grouse managers to reduce anthelmintic use, the authors experimentally withdrew medication from parts of eight moors. The authors monitored parasite and grouse responses by counting eggs and adult worms and grouse mortality and breeding success. Rapid increases in parasite egg counts in early spring culminated in resuming medication at three wet, blanket-peat sites; one in the first spring and two in the second. Medication was restored, despite low parasite counts, at a fourth moor. On the remaining four moors, drier heaths in the east, parasite levels remained low, were not associated with grouse mortality, but breeding success was 16 per cent lower in years without medication. Better parasite monitoring by grouse managers and vets alike may reduce anthelmintic use, helping prevent drug resistance, but this may be off-set by reduced grouse productivity.

Economic viability of anthelmintic treatment in naturally infected beef cattle under different nutritional strategies after weaning.

The aim of the present study was to evaluate the effects of treatment with different anthelmintic compounds on the productivity of naturally infected calves and the economic viability of these treatments within extensive breeding systems employing different nutritional strategies after weaning. For this purpose, 4 farms with 42-60 calves naturally infected with gastrointestinal nematodes were selected. The calves were distributed into 6 groups (7-10 animals each) per farm and treated with ivermectin 1%, ivermectin 3.15%, eprinomectin 5%, levamisole 7.5%, albendazole 15%, and control group (no treatment). These animals were evaluated over an experimental period of 150 days. Levamisole 7.5% presented the best capacity for the reduction of eggs per gram (EPG) of feces in all herds evaluated, followed by albendazole 15% and eprinomectin 5%. Parasite resistance to multiple drugs was found in all herds, especially those of Cooperia, Haemonchus, Oesophagostomum, and Trichostrongylus. For farm 1, differences in weight gain and EPG reduction percentages led to a difference of US$285.06 between the levamisole and ivermectin 3.15% groups. Similar findings were noted for the levamisole and ivermectin 1% groups of farm 3, with a difference of US$399.37 because of the final weight gain in these groups. For farms 2 and 4, the ivermectin 3.15% and control groups, respectively, were the most profitable; these unexpected results were possibly influenced by variables not measured during the experimental period. This study suggested that anthelmintic treatments should always precede an efficacy test, once they are demonstrated to be most profitable under adequate breeding conditions, to ensure adequate control of gastrointestinal nematode infection.

The use of the larval development assay for predicting the in vivo efficacy of levamisole against Haemonchus contortus and Trichostrongylus colubriformis.

The larval development assay has been used for many years to measure the sensitivity of the free-living life stages of trichostrongylid nematodes to anthelmintics. The assay has applications in both drug discovery and the diagnosis of drug resistance. We revisited the usefulness of the larval development assay for diagnosis of resistance to levamisole using field-derived isolates of Haemonchus contortus and Trichostrongylus colubriformis showing varying levels of resistance to this drug in vivo. Each of the resistant isolates showed a plateau in their larval development assay dose-response at the highest drug concentrations tested, representing a highly-resistant fraction, amounting to between 6.9 and 55.1% of the populations. The remaining population fractions for the resistant isolates showed IC50 values from 1.4- to 17.8-fold higher than their corresponding susceptible isolate of the same species. We used a data set from the DrenchRite® test user manual to derive equations describing the relationship between the IC50 values for these low / moderate resistance components of each population and in vivo drug efficacy, and then used these equations to estimate the expected in vivo efficacy of levamisole against this population component of each isolate. A combination of this expected efficacy, with the known zero efficacy of the drug in vivo against the highly-resistant population fractions in each isolate, allowed us to calculate a predicted drug efficacy for the whole population for each isolate. The predicted levamisole efficacies for the three resistant H. contortus isolates were 88.8, 84.1 and 43.7%. These compared favourably with the actual efficacy of the drug against these isolates as determined in faecal egg count reduction tests or total worm count studies: 79, 66.3 and 40.6%, respectively. Similarly, for T. colubriformis, predicted efficacies of 82.0 and 1.8% compared favourably with the actual efficacies of 65-92 % and 0%, respectively. This study illustrates the usefulness of the larval development assay as a diagnostic tool for predicting in vivo efficacy of levamisole against H. contortus and T. colubriformis.

Lack of efficacy of monepantel against trichostrongyle nematodes in a UK sheep flock.

Monepantel resistance was diagnosed during routine monitoring of the effectiveness of a farm's roundworm control strategy. Weaned lambs had become ill thrifty and developed diarrhoea, despite the routine use of monepantel. This clinical presentation was caused by trichostrongylosis. The faecal egg count reduction was 76.7% (95% CI: 55.1-82.2%) following treatment with 2.5 mg/kg monepantel. Predominantly Trichostrongylus vitrinus along with small proportions of Oesophagostomum venulosum and Trichostrongylus vitrinus were identified by deep amplicon sequencing of pools of larvae recovered from pre and post monepantel treatment coprocultures and on postmortem examinations. The undifferentiated FECRT showed resistance to monepantel, but not to levamisole, ivermectin, or moxidectin. Examination of farm anthelmintic treatment and animal movement records suggested that treatments before movement onto silage aftermaths, putatively with low numbers of susceptible nematodes in refugia, may have placed a high selection pressure on monepantel resistance. Effective control of parasitic gastroenteritis using anthelmintic drugs is a prerequisite for sustainable sheep production. This case reiterates the need for care when combining anthelmintic treatments with movements to safe grazing, and the value of monitoring of anthelmintic efficacy as part of iterative planned animal health management.

Anthelmintic resistance in goat herds-In vivo versus in vitro detection methods.

Anthelmintic resistance (AR) is a serious threat to animal health and has a major economic impact worldwide due to production and financial losses. The aim of this study was to determine the occurrence of AR on 30 goat farms in Slovakia during the pasturing seasons and to compare three widely used in vitro and in vivo methods for detecting AR in field conditions. A three-year survey was conducted during the pasturing seasons of 2014-2016. Goats on each farm were split into treated and control groups and were treated by recommended (5 mg/kg body weight) and double doses (10 mg/kg b.w.) of albendazole. Comparisons between percent reduction in a faecal egg count reduction test (FECRT) and an egg hatch test (EHT) and the presence of L3 larvae in a larval development test (LDT) using resistant concentrations of benzimidazole (BZ) were monitored after treatment. The FECRT indicated percent reductions of 69.2-86.2% for the single dose and of 36.3-45.4% for the double dose. The EHT indicated that all farms had BZ-resistant nematodes. Low (<15% hatching) and high (>15% hatching) levels of resistance were detected on 13 and 17 farms, respectively. The LDT failed to detect resistant larvae on seven farms but detected low and high levels of resistance on seven and 14 farms, respectively. The data indicate a moderate correlation between in vitro and in vivo tests for detecting BZ resistance among the 30 goat farms. The hatching detected by the EHT and the presence of L3 larvae by the LDT at resistant BZ concentrations provided reasonable identification of low levels of resistance in the parasite populations, but the use of a double dose for a treatment may underestimate the real occurrence of low levels of resistant parasites on goat farms.

Monepantel resistant Trichostrongylus colubriformis in goats in Brazil.

In a farm where Trichostrongylus colubriformis in sheep had been found resistant to monepantel (MNP), we aimed to evaluate the efficacy against gastrointestinal nematodes in a controlled efficacy test (CT) and a fecal egg count reduction test (FECRT) in goats. We used 15 (CT) and 30 goats (FECRT), naturally infected, and equally divided into control and treated groups. The efficacy of MNP in the CT against Haemonchus contortus, Trichostrongylus axei and Cooperia curticei was 100%. For T. colubriformis, the efficacy was 90.5% in goats treated with 2.5mg/kg, and 88.1% in goats treated with 3.5mg/kg. In the FECRT, the overall reduction was 91% (2.5mg/kg) and 90% (3.75mg/kg). In the fecal cultures, Trichostrongylus spp. larvae represented 25% (pre-treatment) and 15% (post-treatment) of the larvae in the control group, but they were 75% (2.5mg/kg) and 98% (3.75mg/kg) of the recovered larvae after MNP treatment. In accordance with published standards, and based on FECRT and CT, MNP was considered ineffective against T. colubriformis in the studied flock.

Pharmacokinetics and anthelmintic efficacy of injectable eprinomectin in goats.

The objective of this study was to assess the pharmacokinetics and the anthelmintic efficacy of eprinomectin (Eprecis® 20mg/mL) following subcutaneous administration to goats. Forty non-lactating female Alpine goats aged between one and three years and weighing between 32.7 and 59.5kg, were randomly allocated to one of the following groups (8 animals per group): two groups were not infected and were treated at a dose of either 0.2 or 0.4mg/kg BW of eprinomectin, two groups were experimentally infected with nematodes and treated at 0.2 or 0.4mg/kg BW of eprinomectin similarly and one group was infected and left untreated (control). Infection consisted in a single and simultaneous administration of 5000 Haemonchus contortus and 12,500 Trichostrongylus colubriformis infective larvae. No local or general adverse reaction was visually observed whatever the dose rate. The maximal plasma concentrations (Cmax) were 20.68±12.85 vs 39.79±17.25µg/L and the plasma bioavailabilities (AUC) 83.45±34.75 vs 169.37±43.44µg*d/L for 0.2 vs 0.4mg/kg respectively. The efficacy against H. contortus and T. colubriformis was 97.8 and 98.7% at 0.2mg/kg and 98.4% and >99.9% at 0.4mg/kg respectively. The differences in worm burdens between the two dose rates were only significant for T. colubriformis. These results indicate that injectable eprinomectin is a potent anthelmintic against the two major gastrointestinal nematodes in goats. Additional information is needed regarding pharmacokinetics in lactating goats and milk residues.

Resistance to a triple-combination anthelmintic in Trichostrongylus spp. on a commercial sheep farm in New Zealand.

AIM: To evaluate resistance to anthelmintics containing abamectin, levamisole, and oxfendazole (AB-LEV-OX), derquantal and abamectin (DEQ-AB), moxidectin, and monepantel in naturally acquired gastrointestinal nematodes present on a sheep farm. METHODS: Faecal nematode egg count reduction tests (FECRT) were carried out on lambs that were approximately 7 months-old and infected with naturally acquired nematodes. Lambs were randomly allocated to one of five groups (n=15 per group): treatment with 2 mg/kg derquantel and 0.2 mg/kg abamectin; 0.2 mg/kg abamectin, 8 mg/kg levamisole HCl and 4.5 mg/kg oxfendazole; 2.5 mg/kg monepantel; 0.2 mg/kg moxidectin, or no treatment. Post-treatment samples were collected 12 days later. Abomasa and small intestines were collected from two slaughtered lambs from each of the DEQ-AB, AB-LEV-OX, moxidectin and control groups 15 days after treatment, for nematode counting. RESULTS: The FECRT demonstrated that efficacy was 90.3 (95% CI=84.2-94.1)% for AB-LEV-OX, 54.5 (95% CI=28.4-71.1)% for moxidectin, 99.2 (95% CI=97.4-99.8)% for DEQ-AB and 100% for monepantel, across all genera. For Trichostrongylus spp. efficacy was 85.5% for AB-LEV-OX and 46.7% for moxidectin. Haemonchus spp. were fully susceptible to all treatments. Post-treatment nematode counts indicated that the resistant Trichostrongylus spp. were from the small intestine. CONCLUSIONS: Anthelmintic resistance to both AB-LEV-OX and moxidectin was present in the Trichostrongylus genus on a commercial sheep farm. Monepantel and DEQ-AB were both effective against Trichostrongylus spp. based on FECRT results. CLINICAL RELEVANCE: This finding of resistance to an AB-LEV-OX triple-combination anthelmintic in the Trichostrongylus genus in sheep in New Zealand further limits anthelmintic treatment options available, and calls into question whether this combination is suitable for use as a quarantine treatment.

ANTHELMINTIC EFFECTS OF DRIED GROUND BANANA PLANT LEAVES (MUSA SPP.) FED TO SHEEP ARTIFICIALLY INFECTED WITH HAEMONCHUS CONTORTUS AND TRICHOSTRONGYLUS COLUBRIFORMIS.

BACKGROUND: Helminths is a endoparasites that cause the major losses for profitable sheep production in Brazil. The increased development of resistant strains of endoparasites have enforced the search for sustainable alternatives. The aim of this paper was to provide information about endoparasites control with banana leaves in infected sheep as alternative control strategies and see its viability. MATERIALS AND METHODS: In this study, we performed two trials to investigate the anthelmintic properties of banana leaves on endoparasites in sheep. In Trial 1, twelve sheep were artificially infected with Trichostrongylus colubriformis; in Trial 2, eleven sheep were artificially infected with Haemonchus contortus. Clinical examinations, packed cell volume, total protein, faecal egg counts (FECs) and egg hatchability tests (EHTs) were performed. At the end of the trials, the sheep were humanely slaughtered, and total worm counts were performed. RESULTS: In Trial 1 and 2, no significant FEC decreases were note but significant diference in EHTs were observed. Total worm counts, clinical and haematological parameters did not reveal significant changes between the treatment and control groups. These results suggest that feeding dried ground banana plant leaves to sheep may reduce the viability of Trichostrongylus colubriformis eggs, and this anthelmintic activity is potentially exploitable as part of an integrated parasite management programme. CONCLUSION: However, further investigation is needed to establish the optimal dosage, develop a convenient delivery form and confirm the economic feasibility of using banana plantation byproducts as feed for ruminant species. Abbreviations: Coproculture test (CT)., Faecal egg count (FEC)., Egg hatchability test (EHT).

Quantification of resistant alleles in the ß-tubulin gene of field strains of gastrointestinal nematodes and their relation with the faecal egg count reduction test.

BACKGROUND: Benzimidazole (BZ) resistance in gastrointestinal nematodes is associated with a single nucleotide polymorphism (SNP) at codons 167, 198 and 200 in the isotype 1 of beta-tubulin gene although in some species these SNPs have also been associated with resistance to macrocyclic lactones. In the present study we compared the levels of resistance in Teladorsagia circumcincta and Trichostrongylus colubriformis by means of the faecal egg reduction test (FECRT) and the percentage of resistant alleles obtained after pyrosequencing. The study was conducted in 10 naturally infected sheep flocks. Each flock was divided into three groups: i) group treated with albendazole (ABZ); ii) group treated with ivermectin (IVM); iii) untreated group. The number of eggs excreted per gram of faeces was estimated at day 0 and 14 post-treatment. RESULTS: Resistance to ABZ was observed in 12.5% (1/8) of the flocks and to IVM in 44.4% (4/9) of them. One flock was resistant to both drugs according to FECRT. Coprocultures were performed at the same dates to collect L3 for DNA extraction from pooled larvae and to determine the resistant allele frequencies by pyrosequencing analysis. In T. circumcincta, SNPs were not found at any of the three codons before treatment; after the administration of ABZ, SNPs were present only in two different flocks, one of them with a frequency of 23.8% at SNP 167, and the other 13.2% % at SNP 198. In relation to T. colubriformis, we found the SNP200 before treatment in 33.3% (3/9) of the flocks with values between 48.5 and 87.8%. After treatment with ABZ and IVM, the prevalence of this SNP increased to 75 and 100% of the flocks, with a mean frequency of 95.1% and 82.6%, respectively. CONCLUSION: The frequencies observed for SNP200 in T. colubriformis indicate that the presence of resistance is more common than revealed by the FECRT.

Ovicidal and larvicidal activity of extracts of Opuntia ficus-indica against gastrointestinal nematodes of naturally infected sheep.

This study describes the in vitro anthelmintic activity of extracts from Opuntia ficus indica against gastrointestinal nematodes of sheep. The anthelmintic activity was evaluated by inhibition of egg hatching, larval development and larval migration assays. The residual aqueous fractions from cladodes and fruits showed higher ovicidal activity with EC50 values of 7.2mg/mL and 1.5mg/mL, respectively. The aqueous, hexane, and ethyl acetate fractions from fruits and the aqueous fraction from cladodes inhibited 100% of larval development at the lowest concentration tested (1.56mg/mL). The crude cladode and fruit ethanolic extracts inhibited larval migration and showed EC50 values of 0.74mg/mL and 0.27mg/mL, respectively. Phytochemical screening detected high concentrations of alkaloids, tannins, flavonoids, and saponins in the fruits and cladodes. The results demonstrated that O. ficus exhibits anthelmintic activity in vitro, suggesting that, beyond its nutritional potential, this plant can also be an ally for parasite control in sheep.

Cross-resistance to moxidectin and ivermectin on a meat sheep farm in France.

Resistance to ivermectin and moxidectin was explored by a faecal egg count reduction test in two sheep flocks with suspected anthelmintic resistance. The FECRT confirmed one suspicion, with a mean percentage of reduction in egg excretion within the treated groups of 0% for ivermectin (CI 95%: -228 to 58) and 13% for moxidectin (CI 95%: -152 to 70). This was further explored by a controlled efficacy test. An experimental infection of 18 naïve lambs was set up using infective larvae isolated from this flock (5000 L3/lamb). Compared to the control group, abomasal worm burdens (Teladorsagia circumcincta) were reduced by 90% [CI 95%: 81.5-94.8] and 85% [CI 95%: 72.4-92.2] after ivermectin (p<0.05) and moxidectin (p<0.05) treatment respectively. Again, compared to the control group, there was a reduction for intestinal strongyles (Trichostrongylus colubriformis) of 100% and 99% [CI 95%: 97.5-99.7] for ivermectin and moxidectin respectively. No difference was found between the efficacy of moxidectin and ivermectin. Pharmacokinetic values indicated that the strongyles were submitted to anthelmintic concentrations usually lethal to them. This trial demonstrated the first multiple resistance of ovine strongyles in France.