Treatment ineffectiveness towards Haemonchus contortus is highly prevalent in sheep and goat farms of North-Eastern Italy.

BACKGROUND: Anthelmintic resistance (AR) is a global threat to grazing livestock farming. In Italy, anthelmintic efficacy remains high compared to other European countries, but many parts of the country haven't been investigated yet. Local veterinary practitioners from Trentino and Veneto regions reported suspected inefficacy towards anthelmintic drugs in some of their farms, prompting a study on AR in sheep and goat farms of northern Italy. The study aimed to assess anthelmintic effectiveness using genus-specific faecal egg count reduction tests (FECRT), to detect differences in treatment response among nematode genera involved in the infection. RESULTS: Twelve farms (6 sheep and 6 goat farms) were included based on clinical suspicion of AR. Treatments were carried out with either benzimidazoles (BZ) or macrocyclic lactones (ML) Treatment was effective in 3/6 goat trials, with reduced effectiveness to BZ in two farms and to ML the last one. In sheep farms (6/6), effectiveness was consistently and more severely insufficient. Ineffectiveness was particularly high towards Haemonchus contortus, while Oesophagostomum/Chabertia maintained susceptibility in nearly all trials. Trichostrongylus/Teladorsagia exhibited intermediate results. CONCLUSIONS: This study reveals diminished efficacy of both BZ and ML in small ruminant farms in north-eastern Italy, an area previously lacking data on the topic, except for goats in South Tyrol. Variability in treatment responses among nematode genera support suspicions of AR, and further concerns are raised by the prevalence of treatment ineffectiveness against the highly pathogenic Haemonchus contortus. This finding underscores the urgent need for comprehensive AR monitoring in the area and improved management practices to prevent further resistance development and protect livestock health.

Prevalence status and detection of benzimidazole resistance using AS-PCR in Haemonchus contortus of goats from Marathwada region, Maharashtra, India.

This study examined Haemonchus contortus prevalence and benzimidazole resistance in eight districts of Marathwada, Maharashtra, India. A comprehensive investigation of 264 abomasa of goats collected from abattoirs and goats necropsied at the College of Veterinary Sciences and Animal Husbandry, Parbhani, revealed 21.21 % a prevalence of H. contortus. The incidence of H. contortus did not vary much across seasons and it was highest in summer (23.42 %), followed by monsoon (22.89 %), and lowest in winter (15.71 %). Statistically non-significant (p < 0.05) prevalence was observed in male and female animals. A detailed examination of 168 adult H. contortus worms from eight districts revealed the presence of all conceivable genotypes including homozygous resistant (rr), susceptible (SS), and heterozygous (Sr) BZ susceptible genotypes. The rr was the most frequent at 50 %, followed by SS at 27 % and Sr at 22 %. The presence of the SNP was observed in in all eight randomly selected and sequenced samples.

Potential distribution modelling for Haemonchus contortus (Nematoda: Trichostrongylidae) in South America.

The species Haemonchus contortus occurs in many regions worldwide, mainly parasitising small ruminants and economically impacting animal production. Climate change is considered a driving force for the risk of diseases caused by helminths and can also affect relationships between parasites and their hosts, with the potential to cause losses in both animal production and biodiversity in general. The aim of this study was to model the potential distribution of H. contortus in South America. We used MaxEnt to perform the analyses and describe the contribution of important bioclimatic variables involved in the species distribution. Our results show that H. contortus colonised most of the areas with habitats that suit the species' environmental requirements and that this parasite presents habitat suitability in a future scenario. Understanding the effects of climate change on the occurrence and distribution of parasite species is essential for monitoring these pathogens, in addition to predicting the areas that tend to present future parasite outbreaks and identify opportunities to mitigate the impacts of the emergence of diseases caused by these organisms.

Nemabiome metabarcoding shows a high prevalence of Haemonchus contortus and predominance of Camelostrongylus mentulatus in alpaca herds in the northern UK.

Gastrointestinal nematodes (GINs) are a common threat faced by pastoral livestock. Since their major introduction to the UK in the early 1990s, South American camelids have been cograzed with sheep, horses, and other livestock, allowing exposure to a range of GIN species. However, there have been no molecular-based studies to investigate the GIN populations present in these camelids. In the current study, we sampled nine alpaca herds from northern England and southern Scotland and used high-throughput metabarcoded sequencing to describe their GIN species composition. A total of 71 amplicon sequence variants (ASVs) were identified representing eight known GIN species. Haemonchus contortus was the most prevalent species found in almost all herds in significant proportions. The identification of H. contortus in other livestock species is unusual in the northern UK, implying that alpacas may be suitable hosts and potential reservoirs for infection in other hosts. In addition, the camelid-adapted GIN species Camelostrongylus mentulatus was identified predominantly in herds with higher faecal egg counts. These findings highlight the value of applying advanced molecular methods, such as nemabiome metabarcoding to describe the dynamics of gastrointestinal nematode infections in novel situations. The results provide a strong base for further studies involving cograzing animals to confirm the potential role of alpacas in transmitting GIN species between hosts.

Development of a three-colour digital PCR for early and quantitative detection of benzimidazole resistance-associated single nucleotide polymorphisms in Haemonchus contortus.

Haemonchus contortus is the most pathogenic nematode in small ruminants and anthelmintic resistance (AR) hampers its efficient control. Early detection of AR status is required to reduce selection for AR and cannot be achieved using phenotypic tests. For benzimidazoles (BZs), the detection of AR-associated alleles characterised by single nucleotide polymorphisms (SNPs) in the isotype 1 ß-tubulin gene allows early AR detection in strongyles. The F200Y, F167Y, E198A and E198L polymorphisms have been described in BZ-resistant populations with a clear variation in frequencies between regions. A novel digital PCR (dPCR) enables the detection of all of the above-described polymorphisms in H. contortus. Assays were validated using synthetic DNA fragments containing these SNPs. Then, larvae obtained and pooled at farm level from 26 Austrian and 10 Italian sheep farms were analysed. For all assays a detection limit of 15 copies/µl of resistance alleles and a high level of accuracy were demonstrated, allowing to detect allele frequencies of 1% in most samples. In Austrian samples, elevated frequencies of F200Y resistance alleles were detected on all farms. Polymorphisms in codon 167 and codon 198 were identified in H. contortus from Austria for the first time. In Italian samples, the frequency of resistance alleles was still comparatively low, but F200Y resistance alleles were traceable. In conclusion we developed for the first time dPCR assays that target all SNPs of relevance associated with BZ-resistance in H. contortus. Future research on AR development could benefit from an early onset of SNP-based surveillance that would include the developed assays for all SNPs of relevance. Improved surveillance in the long term will include other important, though less pathogenic, nematode genera in the analyses.

Relationship between faecal egg count and health status in Nguni goats reared on semi-arid rangelands.

Gastrointestinal parasitism is a major constraint to goat productivity, particularly in resource-limited production systems. The objective of the study was to determine the relationship between faecal egg count and the health status of different classes of Nguni goats. Body condition score (BCS), packed cell volume (PCV), FAMACHA score, and faecal egg count (FEC) were measured in 120 goats of different classes (weaners, does and bucks) across seasons. The identified gastrointestinal nematodes (GIN) were Strongyloides (30 %), Haemonchus contortus (28 %), Trichostrongylus sp. (23 %), Oesophagostomum sp. (17 %) and Ostertagia (2 %), which showed higher prevalence at the hot-wet season compared to other seasons. An interaction (P<0.05) between class and season on BCS was observed. Lower PCV were observed in weaners (24.6 ± 0.79) in the post-rainy season, whereas does 27.4 ± 0.86 and bucks (29.3±1.03) had the highest PCV in the same season. Higher FAMACHA scores were observed in the hot seasons for all goat classes, while lower in the cool-dry season. Linear relationships between FAMACHA scores and FEC were observed in all seasons. The rate of change in FAMACHA score was higher in the post-rainy season (P<0.01) than in other seasons as FEC increased in weaners and does. Bucks had a higher rate of change in FAMACHA in the hot-wet season (P<0.0001) as FEC increased. The rate of BCS decline was higher in the post-rainy season in weaners and does (P<0.01) and bucks (P<0.05) than in other seasons. The decline in PCV was faster during the wet than in the dry seasons. It can be concluded that class and season affected BCS, FAMACHA, and PCV. A linear relationship between FEC and FAMACHA score suggests that FAMACHA could be a good indicator of GIN burden.

Haemonchus contortus: an overview.

This focus article was prepared by Amanda Carson, Rudolf Reichel, Suzie Bell, Rachael Collins and Jasmine Smith of the APHA Small Ruminant Species Expert Group, and Dave Bartley from the Moredun Research Institute.

Phenotypic and genotypic analysis of benzimidazole resistance in reciprocal genetic crosses of Haemonchus contortus.

Haemonchus contortus is arguably one of the most economically important and ubiquitous parasites of livestock globally and commonly involved in cases of anthelmintic resistance. Here, we performed reciprocal genetic crosses using susceptible (MHco3(ISE)) and multiple anthelmintic resistant (MHco18(UGA2004)) H. contortus isolates. Resultant admixed populations were designated MHco3/18 or MHco18/3, where the lead isolate reflects the origin of the females. Three independent filial generations were generated for each cross, which were subjected to bioassays, molecular approaches and population genetic analyses to investigate the phenotypic and genotypic inheritance of benzimidazole (BZ) resistance at each stage. A panel of microsatellite markers confirmed the success of the genetic cross as markers from both parents were seen in the F1 crosses. Egg hatch tests revealed a stark difference between the two F1 crosses with ED50 estimates for MHco18/3 being 9 times greater than those for MHco3/18. Resistance factors based on ED50 estimates ranged from 6 to 57 fold in the filial progeny compared to MHco3(ISE) parents. Molecular analysis of the F167Y and F200Y SNP markers associated with BZ resistance were analysed by pyrosequencing and MiSeq deep amplicon sequencing, which showed that MHco3/18.F1 and MHco18/3.F1 both had similar frequencies of the F200Y resistant allele (45.3% and 44.3%, respectively), whereas for F167Y, MHco18/3.F1 had a two-fold greater frequency of the resistant-allele compared to MHco3/18.F1 (18.2% and 8.8%, respectively). Comparison between pyrosequencing and MiSeq amplicon sequencing revealed that the allele frequencies derived from both methods were concordant at codon 200 (rc = 0.97), but were less comparable for codon 167 (rc = 0.55). The use of controlled reciprocal genetic crosses have revealed a potential difference in BZ resistance phenotype dependent on whether the resistant allele is paternally or maternally inherited. These findings provide new insight and prompt further investigation into the inheritance of BZ resistance in H. contortus.

Frequency of benzimidazole resistance in Haemonchus contortus populations isolated from sheep and goats in Bangladesh.

Anthelmintic resistance against gastrointestinal nematodes especially H. contortus of sheep and goat is a global issue. To address the gravity and extension of AR in Bangladesh, genotyping of 160 adult H. contortus parasitesw ere performed to confirm benzimidazole resistance allele from different geographic zones of Bangladesh based on allele specific PCR (AS-PCR). The genotype frequencies were 9.4% for homozygous resistant (rr), 61.2% for heterozygous (rS) and 29.4% for homozygous susceptible (SS) among the selected areas. The allelic frequency of the mutation conferring resistance (r) ranged from 27.5% to 52.5% indicating substantial existence of benzimidazole resistance in H. contortus in small ruminant nematodes. Therefore, it can be concluded that genotyping the F200Y polymorphism can be used to monitor the resistance and thereby to enhance the control on the development of anthelmintic resistance against H. contortus in small ruminant nematodes.

Integrating applied parasitological and molecular epidemiological methodologies to investigate the capacity of Haemonchus contortus to over-winter on pasture in Scotland.

BACKGROUND: The Barber's Pole worm, Haemonchus contortus is of major concern to sheep producers, particularly in the southern hemisphere. This nematode is also commonly found in many sheep flocks in Northern hemisphere countries but is generally not associated with acute clinical pathology. As with other nematode species, the pattern of disease is changing in the United Kingdom. Changes in management practices, climate, anthelmintic resistance prevalence and parasite adaptation are possible factors thought to be responsible for this. METHODS: In the present study, a combination of traditional applied parasitological and molecular species identification techniques were used to assess the capability of H. contortus infective larvae to over-winter on pasture and infect lambs in early spring. RESULTS: Adult and inhibited H. contortus worms were identified in previously worm-free tracer lambs that had grazed contaminated pasture in late winter/early spring (February/March). CONCLUSION: The study illustrated the benefit of using classical applied parasitology techniques in conjunction with molecular species identification methods to explore the epidemiology of gastro-intestinal nematodes of livestock. This study also demonstrated that larvae were able to survive over-winter, albeit in small numbers, and potentially contaminate pastures earlier than previously considered in northern regions of the UK.

Epidemiology and spatio-temporal distribution of gastrointestinal parasites infection and accuracy of FAMACHA test in sheep in traditional farming systems in Burkina Faso.

Blood and faecal samples from 2086 Sahelian and Djallonke sheep have been collected to assess the epidemiology and spatio-temporal distribution of gastrointestinal parasites. A survey with a questionnaire allowed collecting data on individual animal and farms. Faecal samples were analysed using the McMaster technique, while anaemia was assessed using FAMACHA score test and packed cell volume. The overall prevalence of gastrointestinal parasites was 91%, and strongyles (70.7%), Eimeria sp. (60.4%), Moniezia sp. (5.7%), Stronyloides sp. (0.9%) were identified. There was no significant association between the region and strongyles infection (P ˃ 0.05). Animals sampled during the rainy season (n = 565; P = 82.2%, mean EPG = 154.8 ± 12.02) were mostly and heavily infected than those from the hot dry (n = 518; P = 74.2%; mean EPG = 97.7 ± 17.4) and the cold dry season (n = 392; P = 55.5%; mean EPG = 24.5 ± 19.5) (P ˂ 0.05). Females (n = 1027; P = 72.1%; mean EPG = 77.6 ± 17) were most infected than males (n = 448; P = 67.7%; mean EPG = 61.6 ± 19.5) (P ˂ 0.05). Animals that were treated, at most 3 months before sampling (n = 166; P = 61.5%; mean EPG = 41.7 ± 21.4), were less infected than those, which received this treatment after three months before sampling (n = 199; P = 74.8%; mean EPG = 89.1 ± 15.8) (P ˂ 0.05). Data from blood samples indicate that 6.5% of sheep was anaemic (PCV ≤ 19%), while 59.7% was noted anaemic regarding FAMACHA scores. PCV values varied significantly for FAMACHA scores, and the highest mean value was noted for score 1 (27.6) (P ˂ 0.05). The Cohen's kappa score between FAMACHA and PCV was 0.02. These findings suggest that strongyles infections are significantly associated with season, and heavier infections were noted during rainy season.

Relationships between FAMACHA© scores and parasite incidence in sheep and goats.

One of the most important activities in animal raising is parasite control. Since parasites share what animals eat on one hand, they have disease-causing effects on the other hand, they are parasites that must be fought. In fact, they can be responsible for the decrease in yield and can also cause death. Haemonchus contortus parasite from the Trichostrongylidae family is a blood parasite that causes anemia in sheep and goats. In this study, using the FAMACHA© card, which is widely used in the determination of anemia caused by Haemonchus contortus in the world, the color of the conjunctiva was scored in Akkaraman sheep and Hair goats raised in the Sizma district of Konya, and the relations between the score and the parasite type and density were determined. Accordingly, while no animals with 1 and 5 scores were observed in sheep, the numbers of animals with scores of 2, 3, and 4 were determined as 7.84%, 40.2%, and 52.96%, respectively. Parasite eggs belonging to the Trichostrongylidae family were observed in 96.07% of the sheep. On the other hand, no animal with score 1 or 2 was observed in goats. The numbers of animals with 3, 4, and 5 scores were determined as 6.12%, 54.08%, and 39.80%, respectively. Eimeria, the most common parasite species, was found in 68.18% of the goats and parasite eggs from the Trichostrongylidae family were observed in 17.05%. As a result, it was concluded that the card in question was a practical, easily available, and cheap tool in the detection of anemia by using the relationships between FAMACHA© card scoring and parasite loads.

Comparative Evaluation of Two In Vitro Tests for Detection of Ivermectin Resistance in Haemonchus contortus of Small Ruminants in Uttar Pradesh, India.

PURPOSE: Resistance against ivermectin in India has been detected solely implementing in vivo tests and there is no published report of resistance employing in vitro methods. The present study was carried out to study ivermectin resistance in H. contortus of small ruminants by two in vitro tests and to determine their efficacy in effectively detecting ivermectin resistance in the field isolates. METHODS: The present study was carried out in the small ruminant farms of the western region of Uttar Pradesh, India. Faecal samples with high egg per gram of faeces for H. contortus were selected. Two in vitro tests namely Micro agar larval development test and larval development assay were performed for assessing ivermectin resistance in field isolates of H. contortus by subjecting the eggs to different concentrations of ivermectin aglycone. RESULTS: The results of the two in vitro tests implicated towards the susceptibility of H. contortus isolates in the area under study. The standard deviations of the two tests was compared and was found to be statistically non-significant. CONCLUSION: It can be said that both in vitro tests are reliable for detecting resistance against different anthelmintics including ivermectin.

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.

Ovine haemonchosis: a review.

Sheep farming is the backbone of a rural economy in developing countries, and haemonchosis is a major impediment in the way of its progress. Haemonchus contortus (H. contortus) infection persists all over the world particularly in the tropical and sub-tropical regions. Various review articles have been published to substantially cover one or more aspects of its morphology, prevalence, pathogenesis, symptoms, diagnosis, immune response, drug resistance, treatment, and control measure. The objective of this paper is to briefly review past and present information available in the aforementioned areas in one place to enable the readers to fully understand the problem from a broader perspective. H. contortus parasite harbours in abomasum of affected animal and feeds on its blood, producing mild to severe symptoms and even death in acute form. The parasite thus inflicts heavy production losses and is of economic importance. H. contortus has developed diverse characters over the years leading to limited success in the production of vaccines. Indiscriminate use of the anthelmintics has produced drug resistance against almost all conventional products. Efficacy of medicinal plants and non-conventional chemicals has been reported under controlled experiments; however, research on their adverse effects on growth and fertility is yet to be studied. Research on molecular tools for identification and introduction of resistant genes into the flock is also underway but still a long journey to find its field application. Crossbreeding may compromise the production traits of the existing flock. In given circumstances, a targeted selective treatment approach along with selective breeding, culling of more susceptible animals, and maintaining a good body condition score through the provision of a balanced diet remains a workable strategy to control haemonchosis in sheep.

Haemonchus sp. in beef cattle in Brazil: species composition and frequency of benzimidazole resistance alleles.

The aim of the present study was to investigate the occurrence of Haemonchus contortus and Haemonchus placei in beef cattle and the frequency of single nucleotide polymorphisms associated with benzimidazole (BZ)-resistance in Haemonchus spp. in Brazil. For such, fecal samples were collected from 61 beef cattle ranches in 11 Brazilian states. Third-stage larvae (L3) were produced for morphological species identification and DNA extraction. PCR was performed for the analysis of the isotype 1 ß-tubulin gene and the products were sequenced to confirm the presence of H. placei and H. contortus. For each field population, pyrosequencing assays were performed to quantify the frequency of the F167Y, E198A and F200Y polymorphisms in the isotype-1 ß-tubulin gene. The results of the morphometric analysis of 2345 larvae showed that H. placei was present on all ranches. The analysis of the isotype 1 ß-tubulin gene confirmed 100% prevalence for H. placei and 23.7% for H. contortus. Pyrosequencing assays demonstrated single-nucleotide polymorphisms (SNPs) associated with BZ-resistance in all three codons (F167Y, E198A and F200Y) of the isotype 1 ß-tubulin gene in H. placei field populations. Frequencies of resistance-associated alleles above background (≥ 15%) were found for at least one codon in 11.4% of the field isolates and maximum frequencies of 30, 21 and 29% were found for codons 167, 198 and 200, respectively, on individual ranches. This study confirms the presence of H. contortus in beef cattle in the major livestock farming states in Brazil and demonstrates that genotypes associated with BZ resistance are present in field populations of Haemonchus spp..

Is there competition between Haemonchus contortus and Haemonchus placei in a pasture grazed by only sheep?

This study aimed to evaluate the dynamics of Haemonchus contortus and Haemonchus placei infections and hybridization between these species in grazing sheep without contact with cattle. On January 14, 2014, sixteen young sheep were infected with 4000 infective H. placei third-stage larvae L3; 11 days later, another group n = 16 was infected with 4000 H. contortus L3. The establishment rates of H. contortus and H. placei L3 were, on average, 61.6 % and 56.8 %, respectively, in the permanent sheep. After the establishment of patent infections, all permanent sheep were allocated together in the same clean pasture where they grazed for the next 12 months. Euthanasia of a sample of the permanent sheep was performed every three months: in May, August, November and February. Two weeks before the sheep were removed for euthanasia, 2 worm-free tracer sheep were introduced to the pasture to evaluate the larval population in the field. The tracer sheep grazed alongside the permanent sheep for 2 weeks. Then, they were housed indoors for 20 days; at the end of this period, they were euthanized. Parasites were recovered from the permanent and tracer sheep and identified using morphological and molecular techniques. A total of 432 worms (from permanent and tracer animals) were analyzed by PCR using species-specific primer pairs. Of these specimens, only two (0.46 %) male worms were identified as hybrids: one was recovered from a permanent animal euthanized in August and the other from a tracer sheep that grazed in May. The last detection of adult H. placei worms occurred in sheep euthanized in May (approximately 3.5 months after the beginning of the grazing period). The morphological evaluation of the L3 produced in fecal cultures showed that H. placei were progressively replaced by H. contortus populations starting in March. The last trace of H. placei L3 was found in August, when a small percentage (0.5 %) of infective larvae with H. placei morphology was identified in a fecal culture. In conclusion, hybridization between H. contortus and H. placei can occur in the field during coinfection. It was demonstrated that H. placei established successfully in artificially infected worm-free sheep; however, with concomitant natural reinfection with H. contortus, the H. placei population showed a rapid decrease and was eliminated within a few months in an environment without cattle.

Epidemiology of strongyle nematode infections and first report of benzimidazole resistance in Haemonchus contortus in goats in South Darfur State, Sudan.

BACKGROUND: Since pastoralists in South Darfur, Sudan, had complained about lack of albendazole (ABZ) efficacy to control nematodes in goats, the frequency of infection with gastrointestinal helminths was studied before in vivo faecal egg count reduction tests (FECRT) were conducted using ABZ orally either at the dose recommended for sheep, 5 mg/kg body weight (bw) or at 10 mg/kg bw. Experiments included goats naturally infected with gastrointestinal nematodes or experimentally infected with local Haemonchus contortus isolates. Three study areas (Nyala, Beleil and Kass) were visited in autumn or winter. RESULTS: Out of 478 screened goats, 82.4% were infected with gastrointestinal helminths and 82% were shedding eggs of strongyle nematodes with 90% of the strongyle larvae representing Haemonchus spp. A FECRT using naturally infected goats (n = 225: 71 untreated, 104 and 50 treated with 5 and 10 mg ABZ/kg bw, respectively) detected reduced ABZ efficacy in Nyala and Kass. Paired and unpaired FECRT calculations detected reductions of 72-92% with samples taken at 8 days post treatment with 5 mg ABZ/kg bw and of 85-94% with 10 mg ABZ/kg bw. The FECRT based on day 14 post treatment samples showed reductions of 69-77% with 5 mg/kg and of 75-87% with 10 mg ABZ/kg bw. In Beleil, ABZ efficacy was 95%. In the egg hatch test EC50 values for Nyala and Kass ranged from 0.12-0.24 µg thiabendazole/ml, corresponding to benzimidazole resistant phenotypes. Only Haemonchus spp. larvae were present after treatments in coprocultures. When the efficacy was evaluated experimentally using isolates of H. contortus from Nyala and Kass, the 5 mg ABZ/kg dose revealed reductions of 76-78% on day 8 and of 62-70% on day 14 with the unpaired method. Using 10 mg ABZ/kg, the FECR was still only 77-82%. CONCLUSIONS: Both, in vivo and in vitro methods detected resistant H. contortus populations in goats from South Darfur State. The time point 14 days post treatment was more sensitive for detection of ABZ resistance than 8 days post treatment. This is the first report on the occurrence of anthelmintic resistance in Sudan confirming that anthelmintic resistance selection is occurring in African subsistence farming systems.

Alarming levels of anthelmintic resistance against gastrointestinal nematodes in sheep in the Netherlands.

In a survey involving 34 sheep flocks spread over the Netherlands anthelmintic resistance (AR), based on a fecal egg count reduction (FECR) test, was determined for six different products. The study was conducted in ewes shortly after lambing during spring 2015. A FECR of less than 90%, indicating presence of AR against one or more nematode genera producing strongylid eggs, was found in 22 of 30 (73.3%) flocks against oxfendazole, 18 of 23 (78.3%) flocks against ivermectin, 15 of 32 (46.9%) flocks against moxidectin, and 2 of 26 (7.7%) flocks against monepantel. No AR was observed against levamisole. If oxfendazole resistance was observed, Haemonchus contortus was involved in 90.5% of the cases. If resistance against ivermectin, moxidectin or monepantel was observed, it invariably involved H. contortus. In the majority of cases resistance was also observed for Teladorsagia circumcincta and/or Trichostrongylus spp, between which no distinction was made in this study. Based on FECR 9 of 15 (60.0%) flocks showed resistance against closantel, which was mainly due to closantel not being effective against most other nematode species than H. contortus. However, in 44.4% of flocks showing reduced FECR it did involve H. contortus as well. Multi-drug resistance (excluding closantel) was found in 16 flocks, of which 8 showed resistance against 2 products, 7 against 3 products and 1 flock showed resistance against 4 products. If resistance against 3 or 4 products was present, there invariably was resistance against both ivermectin and moxidectin. Overall, of the 22 flocks in which both macrocyclic lactones (ML) were tested, 4 (18.2%) showed no resistance against both products, 9 (40.9%) showed resistance against ivermectin only, and 9 (40.9%) showed resistance against both MLs. It is concluded that AR is widespread in sheep in the Netherlands and involves products from all major anthelmintic classes, with possibly the exception of levamisole. It appears that the macrocyclic lactones have lost much of their efficacy against sheep nematodes over the last decade.