Field efficacy of four anthelmintics and confirmation of drug-resistant nematodes by controlled efficacy test and pyrosequencing on a sheep and goat farm in Denmark

Multidrug resistance in Haemonchus contortus in sheep - can it be overcome?

Introduction

Gastrointestinal nematodes pose a threat to animal health and affect farmers by negatively impacting farm management.

Material and Methods

The study was conducted on a sheep farm with suspected reductions in the efficacies of anthelmintics. Efficacy was determined using in vivo faecal egg count reduction, in vitro egg hatch (EHT) and larval development (LDT) tests. In the first phase, 60 sheep were equally split into six groups. Group 1 received the recommended dose of albendazole (ALB), group 2 received the same after fasting for 24 h, group 3 received the dose divided into two halves at 6 h intervals, group 4 received a double dose of ALB, and group 5 received the recommended dose of ivermectin (IVM). Group 6 served as a control. The second phase of the experiment had two groups: one treated with levamisole (LEV) and a control group. Faecal samples were collected from all sheep.

Results

No reduction of egg output was observed in the groups treated with single, double, or divided doses of ALB, but one of 13.7-16.9% was noted in the fasting group. Efficacy in the IVM group ranged from 31.50 to 39.97%. The mean concentrations sufficient to prevent 50% of the eggs from hatching in the in vitro EHT and the mean concentrations in which the development of larvae to the L3 stage was inhibited by 50% in the LDT exceeded established thresholds for benzimidazoles and IVM. Haemonchus contortus was the only species identified after treatment. The LDT did not indicate the presence of resistance to LEV. All animals treated with LEV were negative for eggs 10 d after treatment.

Conclusion

Resistance to ALB and IVM in Haemonchus contortus was confirmed. Alternative approaches to improve the efficacies of benzimidazole did not sufficiently increase the efficacy, but LEV was an efficient anthelmintic treatment.

Understanding anthelmintic resistance in livestock using "omics" approaches

Widespread and improper use of various anthelmintics, genetic, and epidemiological factors has resulted in anthelmintic-resistant (AR) helminth populations in livestock. This is currently quite common globally in different livestock animals including sheep, goats, and cattle to gastrointestinal nematode (GIN) infections. Therefore, the mechanisms underlying AR in parasitic worm species have been the subject of ample research to tackle this challenge. Current and emerging technologies in the disciplines of genomics, transcriptomics, metabolomics, and proteomics in livestock species have advanced the understanding of the intricate molecular AR mechanisms in many major parasites. The technologies have improved the identification of possible biomarkers of resistant parasites, the ability to find actual causative genes, regulatory networks, and pathways of parasites governing the AR development including the dynamics of helminth infection and host-parasite infections. In this review, various "omics"-driven technologies including genome scan, candidate gene, quantitative trait loci, transcriptomic, proteomic, and metabolomic approaches have been described to understand AR of parasites of veterinary importance. Also, challenges and future prospects of these "omics" approaches are also discussed.

[Five past twelve - the resistance situation in small ruminant gastrointestinal nematodes in Germany]

Anthelmintic resistance has reached alarming levels worldwide and already seriously threatens pasture-based small ruminant production in certain geographic regions. The situation in Europe has also dramatically deteriorated in the last decade. This review provides an overview of the occurrence of anthelmintic resistance in small ruminants with a particular focus on Germany and its neighbouring countries. It also covers mechanisms leading to the development and spread of anthelmintic resistance, and recommendations for a responsible use of anthelmintics in veterinary practice.

Antiparasitic Tannin-Rich Plants from the South of Europe for Grazing Livestock: A Review

Internal parasites are one of the main causes of health threats in livestock production, especially in extensive livestock farming. Despite the environmental toxic effects (loss of dung beetles, biodiversity, and other issues) and resistance phenomenon derived from their prolonged use, anti-parasitic chemical pharmaceuticals are frequently used, even in organic farming. Such a situation within the context of climate change requires urgent exploration of alternative compounds to solve these problems and apparent conflicts between organic farming objectives regarding the environment, public health, and animal health. This review is focused on some plants (Artemisia spp., Cichorium intybus L., Ericaceae family, Hedysarum coronarium L., Lotus spp., Onobrychis viciifolia Scop.) that are well known for their antiparasitic effect, are voluntarily grazed and ingested, and can be spontaneously found or cultivated in southern Europe and other regions with a Mediterranean climate. The differences found between effectiveness, parasite species affected, in vitro/in vivo experiments, and active compounds are explored. A total of 87 papers where antiparasitic activity of those plants have been studied are included in this review; 75% studied the effect on ruminant parasites, where gastrointestinal nematodes were the parasite group most studied (70%), and these included natural (31%) and experimental (37%) infections.

Advances in diagnosis and control of anthelmintic resistant gastrointestinal helminths infecting ruminants

Infection with gastrointestinal helminths is widely spread among ruminant causing severe losses and adversely affects the livestock husbandry. Synthetic chemotherapeutics have been utilized throughout years, as a means of combating helminthiasis. Anthelmintic resistance (AR) has a serious concern on livestock industry which, mainly arises as outcome of misuse, improper dosing and frequent utilization of the synthetic drugs.Various gastrointestinal helminths have the capability to survive the therapeutic dose of anthelmintics and become resistant to the major anthelmintic classes. Early diagnosis might delay or reduce the risk of AR. Conventional phenotyping methods were commonly used for detection of anthelmintic resistant helminths, but appeared to lack of sensitivity, especially when the frequency of resistant allele is very low. Several molecular assays were carried out to detect the AR with greater accuracy. Sustainable effective preventive and control measures for gastrointestinal helminths infection remain the corner stone to overcome AR. Rational use of anthelmintics with keeping unexposed proportion of worm populations, could have the potentiality to maintain and prolong the efficacy of anthelmintics. Several alternative anthelmintic treatments might offer valuable solutions either alone or adjunct to synthetic drugs to dilute the spread of resistance alleles among the helminths population. This article reviews current status of various diagnostic methods and control measures for anthelmintic resistant gastrointestinal helminths infecting ruminants and tries to present a practical protocol to avoid or delay the development of AR.

Parasitofauna and current status of anthelmintic resistance in Latvian sheep farms

Background and Aim:

Parasitic invasions, especially gastrointestinal nematodes, are widespread and are one of the main problems in sheep farms. For this reason, sheep are dewormed more often than other livestock species, often several times a year. Concerns about antiparasitic resistance from the farmers and veterinarians have arisen because, on some farms, antiparasitic drugs are used routinely for very long periods. There are no data available on anthelmintic resistance in gastrointestinal nematodes in sheep in Latvia. Our work aimed to determine the most common endoparasites in sheep and the degree of anthelmintic resistance on sheep farms in Latvia.

Materials and Methods:

All sheep (577) underwent a coprological examination before the start of the study, and only sheep diagnosed with more than 200 McMaster eggs per gram of feces were included in the study. A fecal egg count reduction (FECR) test was performed on 20 sheep flocks in Latvia.

Results:

In Latvia, sheep were most commonly infected with Eimeria spp. 97% (confidence interval [CI] 95% 96-98). The second most commonly diagnosed species were Trichostrongylidae 91% (CI 95% 89-93) and Strongyloides spp. 76% (CI 95%, 72-79). The ivermectin (IVM) FECR was 0.74% (0.73-0.74), showing resistance in all sheep farms included in this study. Albendazole (ABZ) FECR 0.89% (0.88-0.89) was effective.

Conclusion:

This study showed that the most popular deworming drugs (ivermectin, albendazole) in Latvia are ineffective in sheep. Additional studies on the use of IVM+ABZ combinations for deworming sheep should be performed.

Anthelmintic Drug Resistance of Gastrointestinal Nematodes of Naturally Infected Goats in Haramaya, Ethiopia

Gastrointestinal parasites and their anthelmintic resistance are major constraints to goat production in Ethiopia. Experimental investigation by faecal egg count reduction test (FECRT) and larval cultures were used to assess the occurrence of anthelmintic resistance in naturally infected goats with gastrointestinal nematodes (GIN) in Haramaya, Ethiopia. One hundred goats with a minimum of 150 eggs per gram (EPG) count were selected and randomly divided into five groups, 20 goats in each group, four treated and one untreated group. The result of the faecal egg count reduction test percentage (FECRT%) and the lower 95% confidence limit showed the presence of anthelmintic resistance for all tested drugs except tetramisole. FECRT% and lower 95% confidence limit were 69.9% and 36.9 for albendazole, 84.3% and 66.1 for tetraclozan, 95.7% and 87.4 for tetramisole, and 71.1% and 38.2 for ivermectin, respectively. Trichostrongylus, Teladorsagia, and Haemonchus showed anthelmintic resistance for tested drugs. Coproculture from different treatment groups revealed Trichostrongylus (69.2% in ivermectin and 59.6% in albendazole) were the predominant nematode followed by Teladorsagia (21.9% in albendazole and 14.7% in ivermectin). In tetraclozan treatment group, Trichostrongylus (42%) and Teladorsagia (41.3%) were comparable, followed by Haemonchus (13%). In group treated with tetramisole, Teladorsagia (54.3%) were the most frequently detected nematode followed by Trichostrongylus (25.7%) and Haemonchus (11.4%). Therefore, this study demonstrated the presence of multidrug resistant nematodes that may limit the productivity of goats. Moreover, further studies covering wider areas of Ethiopia and mechanisms of nematode resistance need to be studied in the future.

First Report of Anthelmintic Resistance in Gastrointestinal Nematodes in Goats in Romania

Currently, there are three classes of anthelmintics most commonly used in small ruminants: the benzimidazoles (BZs), macrocyclic lactones (MLs) and cholinergic agonists (especially levamisole; LEV). The widespread use of those products has led to the emergence of drug-resistant parasite strains which represents a serious threat to the livestock industry. In the present study, we describe for the first time a case of resistance to anthelmintics in goats in Romania. The study was carried out in 2021 in a dairy goat herd from the Transylvania region. Two types of diagnostic methods were used to confirm anthelmintic resistance (AR). First, the faecal egg count reduction test (FECRT), an in vivo AR diagnostic method, was used to evaluate the efficacy of eprinomectin (EPM). The results of this test were analysed applying two different calculative methods that are used only in treated animals (without the control group). Furthermore, two in vitro methods were used: the egg hatch test (EHT) for the detection of resistance to BZs, and the larval development test (LDT) for detection of resistance to all three classes of anthelmintics. The results of FECRT indicate the resistance of gastrointestinal nematodes (GINs) to EPM in both calculative methods (FECR₁ = -88% and FECR₂ = -202%). In addition, the results obtained for ivermectin aglycone (IVM-AG) in LDT also indicate resistance to drugs from MLs group, especially avermectins. Similarly, the results of in vitro methods (EHT and LDT) indicate resistance to BZs in this herd. LEV was the only drug that stopped the development of L3 larvae 100% (LDT). H. contortus was the only nematode species found in coproculture after EPM treatment. Furthermore, H. contotus L3 larvae was the only species found in the wells with the highest concentrations of thiabendazole (TBZ) and IVM-AG in LDT. This suggests that resistance to both BZs and MLs was present for that species.

Effect of an Arthrobotrys musiformis (Fungi: Orbiliales) culture filtrate on the population of gastrointestinal parasitic nematode eggs in faeces of grazing lambs

This study assessed the anthelmintic activity of the oral administration of a free-spore culture filtrate of the nematophagous fungus (NF) Arthrobotrys musiformis (M-10) on gastrointestinal parasitic nematodes (GIN) in naturally infected lambs. The fungus was grown on potato-dextrose agar plates (PDA) and transferred to a fermented rice medium (FRM). After 40-day incubation the total amount of FRM with the growing fungi was transferred to a flask shaker with distilled water for a 24 h period. The fungus was centrifuged and filtered. Three groups of six naturally-infected lambs (>1000 epg) each were treated once as follows: Group 1) 63.8 mg/kg A. musiformis culture filtrate (CF) (per os); Group 2) Levamisole 7.5 mg/ml (intramuscularly), Group 3) 15 ml of distilled water (per os). Faecal samples were individually collected on days -2, 0, 2, 4, 6, 8 and 10 after treatment. For each experimental group, mean egg shedding was calculated and transformed (log 10 [epg + 1]). Means between the fungal filtrate group and the negative control were analysed using a T-Student Test. The faecal egg count reduction test (FECRT) was performed in groups treated with CF and Levamisole in relation to the control group (water) were 36.8-57.4% and 89-95.4%, respectively., although due to the difference between groups, no statistical significance was found (p > 0.05). The use of A. musiformis CF appears to be a good alternative treatment, although, more studies should be performed to establish the use of these fungal products as potential tools for GIN control.

Anthelmintic resistance in small ruminants in the Nordic-Baltic region

Gastrointestinal nematodes (GIN) in small ruminants result in production losses, and consequently economic losses, and are an animal welfare problem in most countries in the Nordic-Baltic region. Intensive use of anthelmintics to control helminth infections has led to anthelmintic resistance (AR), which has become a major issue in many European countries. Several studies have been performed in countries in the Nordic-Baltic region (e.g. Denmark, Sweden, Norway and Lithuania) showing increasing/emerging levels of AR. The aim of this paper is to provide an overview of the problem of AR on sheep and goat farms in the Nordic-Baltic region. This region has a limited number of registered anthelmintics. However, researchers in this area have discovered some surprising findings, such as ivermectin (IVM) resistance on a farm that had never used IVM. In Sweden there is evidence of macrocyclic lactone (ML)-resistant Haemonchus contortus being introduced with sheep imported from the Netherlands. As elsewhere in the world, the livestock trade appears to be contributing to the spread of AR in the region and isolated cases of multidrug-resistant cases have also been reported. This is surprising given that the frequency of treatments here is much lower than in other countries where sheep production is economically more important. The prevailing nematodes are Haemonchus, Teledorsagia and Trichostrongylus, while on some farms Haemonchus is dominant and clinical haemonchosis has increasingly been observed in recent decades. The reasons for this are unclear, but are probably related to this parasite's propensity to rapidly develop drug resistance and a general lack of awareness of the problem, possibly in combination with global warming and the increased livestock trade within the EU. In addition, domestic interactions through contacts with wildlife ruminants, alpacas may also be a contributing factor for transmission of AR.

Frequency of sheep farms with anthelmintic resistant gastrointestinal nematodes in the Mexican Yucatán peninsula

The present study explored the frequency of hair-sheep farms with gastrointestinal nematodes (GIN) resistant to albendazole sulfoxide (AS), ivermectin (IVM) and levamisole (LEV) in the Yucatán peninsula, México, using the faecal egg count reduction test (FECRT), and compared the frequency of farms diagnosed with resistance using three different formulae. The survey included farms from the states of Campeche (9) and Yucatán (14) (2016-2019). Collaborating farms had >100 grazing ewes. Animals in the FECRT were > 12 months old, received no anthelmintic for >8 weeks and had ≥150 GIN eggs per gramme of faeces (EPG). Animals were distributed to respective groups: untreated controls, AS (5 mg/kg BW), IVM (0.2 mg/kg BW), and LEV (7.5 mg/kg BW). Due to low EPG, some farms only included one or two AH groups. Second faecal samples were obtained on day 14 post-treatment to estimate the percentage reduction (%R) and 95% confidence interval (95%CI). Criteria to declare resistance were those proposed by the World Association for the Advancement of Veterinary Parasitology. Three formulae were used to estimate resistance frequency: The RESO© and eggCounts-T:C, which considered treated and control EPG means post-treatment, but differed in their 95%CI estimation, while the eggCounts-T:T only considered pre- and post-treatment EPG means with 95%CI. The RESO© and eggCounts-T:C formulae resulted in the same frequency of IVM resistant farms for Campeche (100%; 9/9) and Yucatán (92.9%; 13/14), while, the eggCount-T:T formula resulted in a frequency of 85.7% (12/14) IVM resistance in Yucatán. The three formulae estimated the same frequency of AS resistant farms in Campeche (100%; 9/9) and Yucatán (87.5%; 7/8). The RESO© and the eggCounts-T:C formulae resulted in the same frequency of LEV resistant farms for Campeche (44.4%; 4/9), and Yucatán (60.0%; 6/10), but the eggCounts-T:T formula resulted in a frequency of 40.0% (4/10) LEV resistance in Yucatán. The FECRT using RESO© or eggCounts-T:C formulae are stricter than the eggCounts-T:T as the latter cannot identify what proportion of the %R cannot be attributed to the AH. The untreated control group helped adjusting the %R calculation and seemed more adequate considering the propensity of hair-sheep to reduce their EPG on their own. .

Parasite control in organic cattle farming: Management and farmers' perspectives from six European countries

Organic ruminant production is expanding in the EU, but parasite management remains a constant challenge. Mandatory outdoor access for all age groups can increase exposure to pasture borne parasites, whilst restrictions in the prophylactic use of anthelmintics can limit parasite control. The scientific community has been working to deliver effective parasite control strategies and alternative approaches in order to slow down the development of anthelmintic resistance (AR). However, the current parasite control practices and overall awareness with regards to AR and alternative approaches on farms are largely unknown and may be causing a knowledge gap between the scientific and farming communities. Therefore, a structured survey was conducted in six European countries (Switzerland, Germany, Denmark, Netherlands, Lithuania, Sweden) to provide basic data on practices, management and farmers' perspectives for grazing and parasite control (gastrointestinal worms and liver flukes) on organic cattle farms. Overall, 375 surveys were collected (282 dairy and 93 beef farms) in 2015-2016, and analysed descriptively. Additionally, surveys from the 228 dairy farms were assessed using a double-hurdle adoption model to identify the factors involved in the decision to drench against gastrointestinal parasites. Generally, there are prominent differences between countries, with monitoring methods differing especially, which has important implications in terms of knowledge transfer. For example, media warning was the most common method in DE, while antibody testing in bulk tank milk was the common method in NL. In other countries, clinical signs (diarrhoea, hair coat quality, and reduced weight or yield) and liver condemnation data were used frequently. In general, organic farmers from the six participating countries indicated that they would accept alternative approaches despite greater cost and labour. The likelihood of drenching were higher on farms with smaller farm areas, higher number of young stock and total livestock units and farms where faecal egg counts were used to monitor the parasites. In conclusion, it was evident that grazing and parasite management varied between the countries even though they operate under the same basic principles. Parasite management strategies must therefore be country specific and disseminated with appropriate methods.

Molecular detection of benzimidazole resistance levels associated with F167Y and F200Y polymorphisms in Haemonchus contortus of goats from Mozambique

Benzimidazole (BZ) resistance of Haemonchus contortus has been associated with single nucleotide polymorphisms (SNPs) in codons 200 (F200Y) and 167 (F167Y) and, to a lesser extent, in codon E198A, of the β-tubulin isotype 1 gene. The present study was undertaken to survey the status of BZ resistance in naturally infected goats in smallholder farms in southern Mozambique by real-time PCR (qPCR) using TaqMan® assays. H. contortus-infective larvae (L3; n = 432) from 12 populations were individually genotyped for F200Y and F167Y SNPs to detect BZ resistance. For the F200Y SNP, the results revealed an overall mean percentages of 18.8% homozygous resistant (RR), 47.8% homozygous susceptible (SS) and 33.4% heterozygous (RS) H. contortus. For the F167Y SNP, the overall mean percentages were 1.6% RR, 94.9% SS and 3.5% RS. The percentage of resistant alleles (%R) for the F200Y and F167Y SNPs was 35.7 and 3.4%, respectively. Genotype combinations of the two mutations indicate resistant percentages ranging from 0.0 to 52.9%. From the four herds with high RR individuals, three farms dewormed the animals monthly, while the fourth farm dewormed the animals every 3 months. In farms where animals were dewormed every 6 months, low percentages of RR individuals were found, whereas no RR individuals were discovered in herds where animals were dewormed annually. These results suggest that the F200Y SNP is more significant in BZ resistance development of the surveyed population compared with the F167Y SNP.

Bioanalytical method development and validation of moxidectin in plasma by LC-MS/MS: Application to in vitro metabolism

Moxidectin (MOX) has recently been approved by the US Food and Drug Administration for the treatment of river blindness in select populations. It is also being evaluated as an alternative for the use of ivermectin, widespread resistance to which is becoming a global health issue. Moreover, MOX is becoming increasingly used as a prophylactic antiparasitic in the cattle industry. In this study, we developed and validated an LC-MS/MS method of MOX in human, monkey and mouse plasma. The separation was achieved on an ACE C₁₈ (50 × 3.0 mm, 3 μm) column with isocratic elution using 0.1% acetic acid and methanol-acetonitrile (1:1, v/v) as mobile phase. MOX was quantitated using MS/MS with an electrospray ionization source operating in negative multiple reaction monitoring mode. The multiple reaction monitoring precursor ion → product ion transitions for MOX and abamectin (IS) were m/z 638.40 → 236.30 and m/z 871.50 → 565.35 respectively. The MS/MS response was linear over the concentration range 0.1-1000 ng/mL in plasma with a correlation coefficient (r² ) of 0.997 or better. The within- and between-day precision (relative standard deviation, RSD) and accuracy were within the acceptable limits per US Food and Drug Administration guidelines. The method was successfully applied to an in vitro metabolic stability study of MOX.

Exploring benzimidazole resistance in Haemonchus contortus by next generation sequencing and droplet digital PCR

Anthelmintic resistance in gastrointestinal nematode (GIN) parasites of grazing ruminants is on the rise in countries across the world. Haemonchus contortus is one of most frequently encountered drug-resistant GINs in small ruminants. This blood-sucking abomasal nematode contributes to massive treatment costs and poses a serious threat to farm animal health. To prevent the establishment of resistant strains of this parasite, up-to-date molecular techniques need to be proposed which would allow for quick, cheap and accurate identification of individuals infected with resistant worms. The effort has been made in the previous decade, with the development of the pyrosequencing method to detect resistance-predicting alleles. Here we propose a novel droplet digital PCR (ddPCR) assay for rapid and precise identification of H. contortus strains as being resistant or susceptible to benzimidazole drugs based on the presence or absence of the most common resistance-conferring mutation F200Y (TAC) in the β tubulin isotype 1 gene. The newly developed ddPCR assay was first optimized and validated utilizing DNA templates from single-worm samples, which were previously sequenced using the next generation PacBio RSII Sequencing (NGS) platform. Subsequent NGS results for faecal larval cultures were then used as a reference to compare the obtained values for fractional abundances of the resistance-determining mutant allele between ddPCR and NGS techniques in each sample. Both methods managed to produce highly similar results and ddPCR proved to be a reliable tool which, when utilized at full capacity, can be used to create a powerful mutation detection and quantification assay.

Field evaluation of anticoccidial efficacy: A novel approach demonstrates reduced efficacy of toltrazuril against ovine Eimeria spp. in Norway

Ovine Eimeria spp. infections cause reduced welfare, increased mortality, and substantial economic losses, and anticoccidials are crucial for their control. Recent reports of toltrazuril resistance in pigs, and anecdotal reports of reduced anticoccidial efficacy in lambs, necessitate evaluation of anticoccidial efficacy. Due to the substantial lifecycle differences between nematodes and coccidia, current WAAVP methods for assessing anthelmintic efficacy are not suitable for such evaluations. Faecal samples were collected from 8 pairs of twin lambs from 36 Norwegian sheep farms 6-8 days after turnout. One twin of each pair was then treated with 20 mg/kg toltrazuril and a second faecal sample from all lambs was collected 7-11 days later. Oocyst excretion rate in all samples was determined using McMasters. Suitability of treatment timing was investigated by evaluating the increase in mean log oocyst excretion in untreated lambs. Based on comparisons between groups, a threshold of ≥0.75 (13 farms) was used to identify farms where drug efficacy could be assessed with confidence, drug efficacy on farms with increases of ≥0.5 but <0.75 (7 farms) were evaluated with caution, and drug efficacy on farms with increases of <0.5 (16 farms) was not estimated. Reduction in oocyst excretion between samples from treated lambs compared with controls from the 20 farms with a threshold of ≥0.5 were then analysed using a generalised linear mixed model. The results were classified based on 95% CI obtained using parametric bootstrapping. Among these 20 farms, two exhibited reduced drug efficacy (upper 95% CI < 95%), 13 had good efficacy (lower 95% CI > 90%), and for 5 the results were inconclusive. This is the first evidence-based report of reduced anticoccidial efficacy in ovine Eimeria spp. Additionally, we highlight the problem of sub-optimal timing of treatment (16/36 farms), which could potentially result in incorrect conclusions being reached regarding lack of drug efficacy.

In vitro nematicidal effect of Chenopodium ambrosioides and Castela tortuosa n-hexane extracts against Haemonchus contortus (Nematoda) and their anthelmintic effect in gerbils

The in vitro nematicidal effect of Chenopodium ambrosioides and Castela tortuosa n-hexane extracts (E-Cham and E-Cato, respectively) on Haemonchus contortus infective larvae (L3) and the anthelmintic effect of these extracts against the pre-adult stage of the parasite in gerbils were evaluated using both individual and combined extracts. The in vitro confrontation between larvae and extracts was performed in 24-well micro-titration plates. The results were considered 24 and 72 h post confrontation. The in vivo nematicidal effect was examined using gerbils as a study model. The extracts from the two assessed plants were obtained through maceration using n-hexane as an organic agent. Gerbils artificially infected with H. contortus L3 were treated intraperitoneally with the corresponding extract either individually or in combination. The results showed that the highest individual lethal in vitro effect (96.3%) was obtained with the E-Cham extract at 72 h post confrontation at 40 mg/ml, followed by E-Cato (78.9%) at 20 mg/ml after 72 h. The highest combined effect (98.7%) was obtained after 72 h at 40 mg/ml. The in vivo assay showed that the individual administration of the E-Cato and E-Cham extracts reduced the parasitic burden in gerbils by 27.1% and 45.8%, respectively. Furthermore, the anthelmintic efficacy increased to 57.3% when both extracts were administered in combination. The results of the present study show an important combined nematicidal effect of the two plant extracts assessed against L3 in gerbils.

Field evaluation of the efficacy of common anthelmintics used in the control of gastrointestinal nematodes of sheep in Dabat district, Northwest Ethiopia

Background

Gastrointestinal nematode (GIN) infections are the main impediments that restrict the welfare and productivity of small ruminant in the world. Effective management of GINs in grazing sheep relies heavily on the use of highly efficacious anthelmintic drugs. However, anthelmintic resistance is becoming a significant concern in the world, and this phenomenon severely threatens the potential utilisation of this control strategy. Therefore, this study was conducted 1) to evaluate the efficacy of commonly used anthelmintic on GINs in naturally infected sheep and 2) to assess the farmers’ perception on anthelmintics utilisation practices in Dabat district, Northwest Ethiopia.

Methods

One hundred twenty nematode infected sheep were used in this study. Sheep were selected based on the egg count (≥150 eggs per gram of faeces). The animals were allocated randomly into four groups (30 animals per group). Group-I, II and III were treated with Albendazole, Tetramisole, and Ivermectin, respectively. The 4th group was left untreated (as control). Faecal samples were collected on day 0 (before treatment), on day 3, 7, 10 and 14 (post-treatment). The modified McMaster technique was used for quantifying the eggs. Faecal egg count reduction test (FECRT) was applied to determine the efficacy of anthelmintic at day 14 (post-treatment). In addition, a questionnaire survey was conducted on 100 randomly selected sheep owners.

Results

All anthelmintics tested revealed significant (P < 0.05) reduction in nematode egg excretion in the sheep post-treatment. Faecal egg count reduction (FECR) levels for Albendazole, Tetramisole, and Ivermectin were 97.2, 98.9 and 97.7%, respectively. Post-treatment egg counts and percentage reduction of egg counts were not significantly different (P > 0.05) among the treatment groups. The nematode genera identified before treatment were Haemonchus, Trichostrongylus, Cooperia, Trichuris, Teladorsagia, Bunostomum, and Strongyloides. Haemonchus and Trichostrongylus were detected after treatment with Albendazole and Ivermectin. The questionnaire survey revealed that Albendazole was the most commonly (90%) used anthelmintic to treat nematodes in sheep, followed by Tetramisole (36%) and Tetraclozan (Tetramisole-Oxyclozanide combination) (20%). Respondents expressed that anthelmintic selection was made based on veterinarian prescription (84%), colour (27%), efficacy (4%), price affordability (1%) and availability (1%).

Conclusion

This study demonstrated that the tested anthelmintics had an acceptable level of efficacy against GINs of sheep.

Anthelmintic activity of Tunisian chamomile (Matricaria recutita L.) against Haemonchus contortus

The chemical treatment of gastrointestinal parasitic diseases has been undermined by increasing resistance and high toxicity. There is an urgent need to search for alternative natural sources for the treatment of such parasites. In this respect, the present study aims to quantify phenolic compounds of chamomile (Matricaria recutita L.) and to study their in vitro anti-oxidant and anthelmintic activities in solvents with increasing polarity. In vitro determination of anti-oxidant capacity was carried out using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical cation methods. In vitro anthelmintic activity was investigated on egg-hatching inhibition and loss of motility of adult worms of Haemonchus contortus from sheep. The results showed that methanolic and aqueous extracts contain more total polyphenols, total flavonoids and condensed tannins than chloroformic and hexanic extracts. ABTS and DPPH assays showed that methanolic extracts had the highest anti-oxidant potency (IC50 = 1.19 μg/ml and 1.18 μg/ml, respectively). In vitro anthelmintic activity showed that both methanolic (IC50 = 1.559 mg/ml) and aqueous (IC50 = 2.559 mg/ml) extracts had the greatest effect on egg hatching and motility of worms (100% after 8 h post exposure at 8 mg/ml). A significant and positive correlation between DPPH and ABTS tests was observed for all tested extracts. Therefore, total phenolic, total flavonoid and condensed tannin values were correlated with IC50 from both ABTS and DPPH, and with inhibition of egg hatching. To our knowledge, this report is the first of its kind to deal with in vitro anthelmintic activities of chamomile extracts.

Overview of anthelmintic resistance of gastrointestinal nematodes of small ruminants in Brazil

Abstract Frequent and inappropriate use of all classes of antiparasitic drugs in small ruminants has led to failures in their effectiveness, culminating in a global problem of anthelmintic resistance. Brazil stands out as one of the world’s leaders in publications about anthelmintic resistance, and for having the most numerous reports of this resistance in small ruminants in the Americas. These studies have involved mainly the fecal egg count reduction test (FECRT) and its correlation with field management practices. In vivoeffectiveness testing is conducted in areas where livestock is of greater economic significance, e.g., in the South (sheep) and Northeast (goats), or is important for research and economic centers, such as the Southeast (sheep). The most widely studied species is sheep, for which the widest range of drugs is also evaluated. Despite significant advances achieved in molecular research, laboratory analyses should include knowledge about the reality in the field so that they can become feasible for the producer. Moreover, molecular studies can be underpinned by the analysis of field studies, such as the maintenance of antiparasitic effectiveness over time and the mechanisms involved in this process.

Failure of ivermectin treatment in Haemonchus contortus infected-Swedish sheep flocks

Control of gastrointestinal nematodes of veterinary importance in Swedish sheep flocks is primarily based on recurring strategic anthelmintic treatments after detection of strongyle eggs in faeces samples. This study reports reduced efficacy of ivermectin (IVM) against Haemonchus contortus in naturally infected Swedish sheep flocks. Faecal egg count reduction tests (FECRT) and examinations of H. contortus-specific DNA with qPCR on larval cultures were applied to samples from 11 sheep flocks (A-K) in south-eastern Sweden between 2013 and 2014. Four of these flocks (D, E, J and K) had been in direct contact with flock H, where IVM treatment failure was first observed in October 2013, some years after the introduction of imported dairy sheep. In flock H, the resistance status to IVM was also confirmed by a larval developmental test. IVM concentrations 15-20 times higher than for susceptible strains of H. contortus were required to kill the larvae. In addition, faeces samples were obtained from 37 other Swedish sheep farms where the treatment response to IVM was screened initially in six animals using FEC and qPCR 7-10days after administration of IVM. Six farms where the majority was identified with this pre-screening test (B, C, F, G, I and K), were also investigated in more detail with FECRT as described above after the animals had been allocated to groups and treated orally or injected with a minimum of 0.2mg IVM, 0.2mg doramectin (farm F) or 0.2mg moxidectin per kg body weight (farm A and B). Four flocks (farm A, D, G and I) were also treated with 4.8mg albendazole and/or 7.5mg levamisole per kg body weight. Pre-treatment faeces samples were collected from 15 animals on the same day as deworming. Post-treatment samples were collected 7-10days later, whenever possible from 10 animals per group with the highest pre-treatment egg counts. Based on FECRT results, IVM efficacy to H. contortus was reduced on six farms (C, D, E, G, H and I) out of 11 farms studied with FECRT. This is the first report of IVM treatment failure in H. contortus-infected sheep in Sweden.