Emergence Of Anthelmintic Resistance Research Articles

Efficacy of Commonly Used Anthelmintics Against Naturally Occurring Gastrointestinal Nematodes in Goats

Efficacy of four commonly used anthelmintics have been evaluated against naturally occurring gastrointestinal nematodes in goats following the method of faecal egg count reduction test (FECRT) in the present study. Fifty goats in the age group of 1 to 2 years old and of either sex, having infection with strongyle group of nematodes were selected in the sheep and goat farm under project ‘Biotech Kisan Hub”, West Bengal University of Animal and Fishery sciences and the goats were equally divided into five groups; group I (infected control), group II (albendazole treated), group III (fenbendazole treated), group IV (ivermectin treated) and group V (levamisole treated). Faecal egg count (FEC) in terms of eggs per gram of faeces (EPG) were estimated in all the experimental goats (n = 50) on 0-day post treatment (0 DPT) and again on 10 DPT. Efficacy of albendazole, fenbendazole, ivermectin and levamisole were 78.15%, 80.24%, 86.38% and 95.46%, respectively. Comparatively less efficacy of albendazole and fenbendazole indicated the emergence of anthelmintic resistance and lower efficacy of ivermectin might be due selection of resistant worms. Efficacy of levamisole was comparatively higher and it can be used strategically to control GI helminth parasites of goats in that farm.

Activity Test of Binahong Leaf Extract (Anredera cordifolia (Ten.) Steenis) Against the Eggs of Ostertagia sp. In Peranakan Etawa Goats In Vivo

Gastrointestinal (GI) nematodes are widely recognized as a significant impediment to the achievement of optimal sheep production outcomes. The management of these parasites is predominantly dependent on the utilization of chemical anthelmintics. In recent decades, there has been a growing concern regarding the emergence of anthelmintic resistance across different categories of anthelmintics, as well as the issue of drug residues in animal products. Consequently, there has been a renewed interest in exploring medicinal plants as a potential alternative source of anthelmintics. Therefore, the purpose of this study was to assess the anthelmintic effectiveness of Anredera cordifolia (Ten.) steenis uses scientifically established in vivo on PE goats. The treatments applied in this study were made up of binahong leaf extract at concentrations of 0 mg/ml, 5 mg/ml, 10 mg/ml, and 15 mg/ml. The variable subject study was the efficacy of binahong leaf extract on Ostertagia sp. eggs. The findings of the investigation on the extract derived from binahong leaves exhibited a significant impact on diminishing the quantity of Ostertagia sp. eggs. The binahong leaf extract concentration of 15mg/ml exhibited the highest efficacy in reducing worm eggs, resulting in a reduction rate of 97.5%.

Comparison of the therapeutic efficacy of five anthelmintics against natural Fasciola hepatica infections in dairy cattle from the Mantaro Valley, Peru.

The intensive use of anthelmintic drugs to control Fasciola hepatica infections in dairy cattle has resulted in the emergence of anthelmintic resistance. Cases of resistance to triclabendazole (TCBZ) have been reported worldwide. The main goal of this research was to evaluate the main five fasciolicides to control fasciolosis in dairy cattle in the Mantaro Valley, Peru. Two fecal egg count reduction tests were performed. In a first study, 24 naturally F. hepatica infected cattle were randomly grouped into three experimental groups (n=8). Groups were treated with either TCBZ, nitroxynil (NTX) or closantel (CLOS). In a second experiment, 55 naturally infected cows were grouped into three experimental groups and treated with either TCBZ (n=18), rafoxanide (RFX)+albendazole (ABZ) (n=19) or clorsulon (CLN)+ivermectin (IVM) (n=18). Therapeutic efficacy was determined following the WAAVP guidelines by measuring reduction in fluke egg output at days 15 and 30 post-treatment. Bootstrapping method was used to obtain the 95% confidence intervals. The efficacy of TCBZ was inadequate in both studies (≤80.8%). Closantel showed high efficacy (≥ 90%) at both days, while NTX showed 92.9% (83-100) and 82.1% (53.6-100), efficacy, at days 15 and 30, respectively. Efficacy for RFX were 92.1% (79.6-98.9) and 97.4% (94.1-99.4); and for CLN, 98.8% (97.6-100) and 80.1% (44.7-99.4), at days 15 and 30, respectively. The outcome of this study indicates reduced therapeutic efficacy of TCBZ against F. hepatica in an important dairy area of the Peruvian central highlands but also demonstrates the validity of four alternatives.

Anthelmintic Agents from African Medicinal Plants: Review and Prospects.

Soil-transmitted helminthiasis affects more than 1.5 billion people globally and largely remains a sanitary problem in Africa. These infections place a huge economic burden on poor countries and affect livestock production, causing substantial economic losses and poor animal health. The emergence of anthelmintic resistance, especially in livestock, and the potential for its widespread in humans create a need for the development of alternative therapies. Medicinal plants play a significant role in the management of parasitic diseases in humans and livestock, especially in Africa. This report reviews anthelmintic studies that have been conducted on medicinal plants growing in Africa and published within the past two decades. A search was made in various electronic databases, and only full articles in English were included in the review. Reports show that aqueous and hydroalcoholic extracts and polar fractions obtained from these crude extracts form the predominant (80%) form of the extracts studied. Medicinal plants, extracts, and compounds with different chemical groups have been studied for their anthelmintic potential. Polyphenols and terpenoids are the most reported groups. More than 64% of the studies employed in vitro assays against parasitic and nonparasitic nematode models. Egg hatch inhibition, larval migration inhibition, and paralysis are the common parameters assessed in vitro. About 72% of in vivo models involved small ruminants, 15% rodents, and 5% chicken. Egg and worm burden are the main factors assessed in vivo. There were no reports on interventions in humans cited within the period under consideration. Also, few reports have investigated the potential of combining plant extracts with common anthelmintic drugs. This review reveals the huge potential of African medicinal plants as sources of anthelmintic agents and the dire need for in-depth clinical studies of extracts, fractions, and compounds from African plants as anthelmintic agents in livestock, companion animals, and humans.

Polymorphisms in exon 11 of the mptl-1 gene and monepantel resistance in Haemonchus contortus.

Chemical treatments are the main strategy to control gastrointestinal nematodes in sheep,and the emergence of anthelmintic resistance, as consequence, results in control failures and leads to economic losses. Thus, molecular tests may constitute an excellent tool for the early detection of anthelmintic resistance-related mutations. Thus, a polymerase chain reaction (PCR)-based genotyping assay followed by polyacrylamide gel electrophoresis (PAGE) was developed to detect polymorphisms in exon 11 of the acetylcholine receptor monepantel-1 gene (mptl-1) that were previously associated with monepantel resistance through a genome-wide study in Haemonchus contortus. DNA samples recovered from individual and pooled third-stage larvae from two susceptible field-derived isolates and five (three in vivo-derived and two field-derived) resistant populations were used. New polymorphisms, including a 6-bp deletion and a 3-bp insertion, were detected in resistant individuals. These indels, confirmed using sequencing of cloned PCR products, are predicted to result in amino acid changes in transmembrane domain 2 (TMD2) of the MPTL-1 protein. The two susceptible isolates showed only the presence of the wild-type allele (100%), whereas lower frequencies of the wild-type allele were detected in monepantel-resistant populations (11.1 to 66.7%). These findings report new polymorphisms in the mptl-1 gene, validate the results obtained through genomic mapping for monepantel resistance, and provide a PCR-based assay to genotype indels located in exon 11 of mptl-1 in H. contortus.

In vitro Anthelmintic Efficacy of Nano-encapsulated Bromelain against Gastrointestinal Nematodes of Goats in Kenya

Gastrointestinal nematodes (GIN) significantly affect goats’ productivity, and thus farmers carry out regular deworming to manage the infections. The emergence of anthelmintic resistance and the high cost of current drugs call for the development of alternatives, including medicinal plant extracts. The current study aimed to assess the anthelmintic efficacy of chitosan encapsulated bromelain (EB) against a selected range of GIN affecting goats in Kenya. Bromelain was extracted using standard laboratory methods from peels of ripe pineapples and thereafter encapsulated with chitosan. The GIN eggs were isolated from goat feces using the flotation method and were then subjected to PCR to identify the species. Adult worms were collected from the gastrointestinal tract of goats slaughtered at the nearby Ruiru abattoir. The PCR showed the extracted strongyle eggs consisted of 7 species of nematodes, including Haemonchus contortus, Oesophagostomum spp., Nematodirus filicollis, Ostertagia ostertagi, Trichostrongylus vitrinus, Trichostrongylus colubriformis, and Trichostrongylus axei. The in vitro assays showed that chitosan EB had an IC50 of 0.184 mg/mL, 0.116 mg/mL, and 0.141 mg/mL for the egg hatch inhibition, larval, and adult mortality assays, respectively. In all the assays, EB indicated better activity than non-encapsulated bromelain. The EB affected the eggs and worms through softening and embrittling the cuticle and shell as well as damaging the blastomeres and causing the death of the growing embryo. According to the results of the current study, EB has high anthelmintic activity on a large range of GIN and has the potential to contribute to the management of these parasites of small ruminants.

Best Management Practices for Parasite Control in Beef Herds in the Southeastern United States

Abstract The objective of this presentation is to outline best management practices for parasite control in beef herds in the Southeastern United States. The emergence of anthelmintic resistance in common gastrointestinal nematodes (GIN) of beef cattle necessitates a new approach. Short term economic gains from anthelmintic use must be balances with programs that foster long term sustainability of parasite control. An understanding of GIN biology combined with diagnostic testing is the foundation for developing control programs tailored to an individual farm. Incorporating refugia-based programs along with appropriate anthelmintic use will promote sustainable parasite control.

The use of ITS-2 rDNA nemabiome metabarcoding to enhance anthelmintic resistance diagnosis and surveillance of ovine gastrointestinal nematodes

(300 words)A lack of quantitative information on the species composition of parasite communities present in fecal samples is a major limiting factor for the sensitivity, accuracy and interpretation of the diagnostic tests commonly used to assess anthelmintic efficacy and resistance. In this paper, we investigate the ability of ITS-2 rDNA nemabiome metabarcoding to enhance fecal egg count reduction testing by providing information on the effect of drug treatments on individual parasite species. Application of ITS-2 rDNA nemabiome metabarcoding to fecal samples from ewes from over 90 flocks across western Canada revealed high gastrointestinal nematode infection intensities in many flocks with Haemonchus contortus being the most abundant species followed by Teladorsagia circumcincta and then Trichostrongylus colubriformis. Integration of ITS-2 rDNA nemabiome metabarcoding with pre- and post-treatment fecal egg counting revealed consistently poor efficacy of producer-applied ivermectin and benzimidazole treatments against H. contortus, but much better efficacy against T. circumcincta and T. colubriformis, except for in a small number of flocks. Integration of nemabiome ITS-2 rDNA metabarcoding with Fecal Egg Count Reduction Tests (FECRT), undertaken on farm visits, confirmed that ivermectin and fenbendazole resistance is widespread in H. contortus but is currently less common in T. circumcincta and T. colubriformis in western Canada. FECRT/nemabiome testing did not detect moxidectin resistance in any GIN species but suggested the early emergence of levamisole resistance specifically in T. circumcincta. It also revealed that although poor efficacy to closantel was relatively common, based on total fecal egg counts, this was due to its narrow spectrum of activity rather than the emergence of anthelmintic resistance. This study illustrates the value of ITS-2 rDNA nemabiome metabarcoding to improve fecal egg count resistance testing, perform large-scale anthelmintic resistance surveillance and direct more targeted rational anthelmintic use.

Piloting a surveillance system to monitor the global patterns of drug efficacy and the emergence of anthelmintic resistance in soil-transmitted helminth control programs: a Starworms study protocol

To eliminate soil-transmitted helminth (STH) infections as a public health problem, the administration of benzimidazole (BZ) drugs to children has recently intensified. But, as drug pressure increases, the development of anthelmintic drug resistance (AR) becomes a major concern. Currently, there is no global surveillance system to monitor drug efficacy and the emergence of AR. Consequently, it is unclear what the current efficacy of the used drugs is and whether AR is already present. The aim of this study is to pilot a global surveillance system to assess anthelmintic drug efficacy and the emergence of AR in STH control programs. For this, we will incorporate drug efficacy trials into national STH control programs of eight countries (Bangladesh, Cambodia, Lao PDR, Vietnam, Ghana, Rwanda, Senegal and a yet to be defined country in the Americas). In each country, one trial will be performed in one program implementation unit to assess the efficacy of BZ drugs against STHs in school-aged children by faecal egg count reduction test. Stool samples will be collected before and after treatment with BZs for Kato-Katz analysis and preserved to purify parasite DNA. The presence and frequency of known single nucleotide polymorphisms (SNPs) in the β-tubulin genes of the different STHs will subsequently be assessed. This study will provide a global pattern of drug efficacy and emergence of AR in STH control programs. The results will provide complementary insights on the validity of known SNPs in the ß-tubulin gene as a marker for AR in human STHs as well as information on the technical and financial resources required to set up a surveillance system. Finally, the collected stool samples will be an important resource to validate different molecular technologies for the detection of AR markers or to identify novel potential molecular markers associated with AR in STH.

Piloting a surveillance system to monitor the global patterns of drug efficacy and the emergence of anthelmintic resistance in soil-transmitted helminth control programs: a Starworms study protocol.

To eliminate soil-transmitted helminth (STH) infections as a public health problem, the administration of benzimidazole (BZ) drugs to children has recently intensified. But, as drug pressure increases, the development of anthelmintic drug resistance (AR) becomes a major concern. Currently, there is no global surveillance system to monitor drug efficacy and the emergence of AR. Consequently, it is unclear what the current efficacy of the used drugs is and whether AR is already present. The aim of this study is to pilot a global surveillance system to assess anthelmintic drug efficacy and the emergence of AR in STH control programs. For this, we will incorporate drug efficacy trials into national STH control programs of eight countries (Bangladesh, Cambodia, Lao PDR, Vietnam, Ghana, Rwanda, Senegal and a yet to be defined country in the Americas). In each country, one trial will be performed in one program implementation unit to assess the efficacy of BZ drugs against STHs in school-aged children by faecal egg count reduction test. Stool samples will be collected before and after treatment with BZs for Kato-Katz analysis and preserved to purify parasite DNA. The presence and frequency of known single nucleotide polymorphisms (SNPs) in the β-tubulin genes of the different STHs will subsequently be assessed. This study will provide a global pattern of drug efficacy and emergence of AR in STH control programs. The results will provide complementary insights on the validity of known SNPs in the ß-tubulin gene as a marker for AR in human STHs as well as information on the technical and financial resources required to set up a surveillance system. Finally, the collected stool samples will be an important resource to validate different molecular technologies for the detection of AR markers or to identify novel potential molecular markers associated with AR in STH.

Molecular detection of two major gastrointestinal parasite genera in cattle using a novel droplet digital PCR approach

Cooperia sp. and Ostertagia sp. are two cosmopolitan parasitic nematodes often found in mixed gastrointestinal infections in cattle across temperate regions. In light of the recent increase in the emergence of anthelmintic resistance in these and other nematodes derived from cattle around the globe, and their negative impact on animal health and productivity, novel molecular assays need to be put forth in order to facilitate the monitoring of parasite burden in infected herds, using pasture and/or fecal samples. Here, we describe a novel droplet digital PCR platform–based concept for precise identification and quantification of the two most abundant and important parasite genera in grazing western European cattle. By exploiting a single nucleotide difference in the two parasites’ ITS2 sequence regions, we have developed two specific hydrolysis probes labeled with FAM™ or HEX™ fluorophores, which can not only distinguish between the DNA sequences of the two, but also quantify them in mixed DNA samples. A third, newly developed universal probe was also tested along the genus-specific probes to provide a robust and accurate reference. It was evident that the universal probe displayed congruent results to those obtained by the genus-specific probes when used with DNA from both parasites in a single sample. All in all, the results of our assay suggest that this novel protocol could be used to distinguish and quantify cattle parasites belonging to the two most important genera (i.e., Cooperia and Ostertagia) in a single mixed DNA sample.

Essential Oils and Their Bioactive Compounds in the Control of Gastrointestinal Nematodes of Small Ruminants

Background: Gastrointestinal nematodes are one of the major health and economic problem of sheep and goats in the world. The control of these nematodes is carried out conventionally with synthetic anthelminths, which favored the selection of gastrointestinal nematode (GIN) populations multiresistant to anthelmintics. The emergence of anthelmintic resistance has stimulated the search for new alternatives to control small ruminant GIN, standing out the use of plants and their bioactives compounds, such as essential oils (EO). The objective of this review was to present the main characteristics and anthelmintic activity of EO, their isolated compounds and drug delivery systems in the control of GIN.Review: Essential oils are a complex blend of bioactive compounds with volatile, lipophilic, usually odoriferous and liquid substances. EO are composed of terpenes, terpenoids, aromatic and aliphatic constituents. EO has various pharmacological activities of interest in preventive veterinary medicine such as antibacterials, antifungals, anticoccicids, insecticides and anthelmintics. In vitro and in vivo tests are used to validate the anthelmintic activity of EO on GIN. In vitro tests are low cost screening tests that allow the evaluation of the anthelmintic activity of a large amount of bioactive compounds on eggs, first (L1) and third stage larvae (L3), and adult nematodes. The antiparasitic effect of EO is related to its main compound or to the interaction of the compounds. These bioactive compounds penetrate the cuticle of the nematodes by transcuticular diffusion, altering the mechanisms of locomotion, besides causing cuticular lesions. Following in vitro evaluation, the acute and sub-chronic toxicity test should be performed to assess the toxicity of the bioactive compounds and to define the dose to be used in in vivo tests. In vivo tests are more reliable because the anthelmintic effectiveness of bioactive compounds is evaluated after the metabolization process. The metabolization process of the bioactive compounds can generate metabolites that exhibit or not anthelmintic effectiveness. The in vivo tests assessing the anthelmintic effectiveness of bioactive compounds in sheep and goats are the fecal egg count reduction test and the controlled test. OE promoted reduction of egg elimination in faeces which may be related to cuticular and reproductive alterations in GIN, and reduction of parasite burden in in vivo tests. Due to the promising results obtained with OE in the in vivo tests, interest has been aroused in using nanotechnology as an alternative to increase the bioavailability of OE and consequently, potentializing its anthelmintic effect, reducing the dose and toxicity of the biocompounds. In addition to nanotechnology, the isolation and chemical modification of compounds isolated from OE have been employed to obtain new molecules with anthelmintic action and understand the mechanism of action of EO on the small ruminant GIN.Conclusion: The use of EO and their compound bioactive in the control of resistant populations of GIN is a promising alternative. The adoption of strategies in which natural products can replace synthetic anthelmintics, such as in dry periods and use synthetic anthelmintics in the rainy season when the population in refugia in the pasture is high, thus reducing the dissemination of GIN resistant populations. As perspective, the evaluation of pharmacokinetics and pharmacodynamics of these natural products should be performed so that one defines treatment protocols that optimize the anthelmintic effect.

Assessment of gastrointestinal nematode infection, anthelmintic usage and husbandry practices on two small-scale goat farms in Malaysia.

Haemonchosis is a common problem on goat farms in tropical countries such as Malaysia. Prevention of production losses generally depends on the use of anthelmintic drugs, but is threatened by the emergence of anthelmintic resistance. This study investigates anthelmintic efficacy on small-scale Malaysian goat farms and describes putative risk factors. Adult goats had moderate to high pre-treatment faecal trichostrongyle egg counts, despite being housed on slatted floors and fed on cut-and-carry forage, raising questions about the source of nematode infection. Our results show multiple resistance to benzimidazole and macrocyclic lactone anthelmintic drugs and allow us to discuss the genetic origins of resistance with reference to farm husbandry and management. We conclude that improvement in Malaysian goat production efficiency will require the development of sustainable helminth control strategies, underpinned by a better understanding of the origins and population genetics of anthelmintic resistance.

Modelling the consequences of targeted selective treatment strategies on performance and emergence of anthelmintic resistance amongst grazing calves

The development of anthelmintic resistance by helminths can be slowed by maintaining refugia on pasture or in untreated hosts. Targeted selective treatments (TST) may achieve this through the treatment only of individuals that would benefit most from anthelmintic, according to certain criteria. However TST consequences on cattle are uncertain, mainly due to difficulties of comparison between alternative strategies. We developed a mathematical model to compare: 1) the most ‘beneficial’ indicator for treatment selection and 2) the method of selection of calves exposed to Ostertagia ostertagi, i.e. treating a fixed percentage of the population with the lowest (or highest) indicator values versus treating individuals who exceed (or are below) a given indicator threshold. The indicators evaluated were average daily gain (ADG), faecal egg counts (FEC), plasma pepsinogen, combined FEC and plasma pepsinogen, versus random selection of individuals. Treatment success was assessed in terms of benefit per R (BPR), the ratio of average benefit in weight gain to change in frequency of resistance alleles R (relative to an untreated population). The optimal indicator in terms of BPR for fixed percentages of calves treated was plasma pepsinogen and the worst ADG; in the latter case treatment was applied to some individuals who were not in need of treatment. The reverse was found when calves were treated according to threshold criteria, with ADG being the best target indicator for treatment. This was also the most beneficial strategy overall, with a significantly higher BPR value than any other strategy, but its degree of success depended on the chosen threshold of the indicator. The study shows strong support for TST, with all strategies showing improvements on calves treated selectively, compared with whole-herd treatment at 3, 8, 13 weeks post-turnout. The developed model appeared capable of assessing the consequences of other TST strategies on calf populations.

Immunogenomics of gastrointestinal nematode infection in ruminants - breeding for resistance to produce food sustainably and safely.

Gastrointestinal nematode (GIN) infection of ruminants represents a major health and welfare challenge for livestock producers worldwide. The emergence of anthelmintic resistance in important GIN species and the associated animal welfare concerns have stimulated interest in the development of alternative and more sustainable strategies aimed at the effective management of the impact of GINs. These integrative strategies include selective breeding using genetic/genomic tools, grazing management, biological control, nutritional supplementation, vaccination and targeted selective treatment. In this review, the logic of selecting for "resistance" to GIN infection as opposed to "resilience" or "tolerance" is discussed. This is followed by a review of the potential application of immunogenomics to genetic selection for animals that have the capacity to withstand the impact of GIN infection. Advances in relevant genomic technologies are highlighted together with how these tools can be advanced to support the integration of immunogenomic information into ruminant breeding programmes.

Influence of sustained deworming pressure on the anthelmintic resistance status in strongyles of sheep under field conditions.

Anthelmintic resistance (AR) status in Madras Red sheep from selected field flocks of a government funded scheme, covered by regular, sustained anthelmintic treatment for more than 10years was determined. Parameters such as fecal egg count reduction test (FECRT), larval paralysis assay (LPA), and allele-specific-PCR (AS-PCR) were used to test the efficacy of fenbendazole, tetramisole, and ivermectin at recommended doses, in two seasons. Sheep belonging to non-beneficiary farmers were used as controls. Mean FECRT values of beneficiary group during winter and summer seasons were 77.77 and 76.04, 93.65 and 92.12, and 95.37 and 98.06%, respectively, for fenbendazole, tetramisole, and ivermectin. In the non-beneficiary groups, the corresponding values were 74.82 and 81.09%, 96.05 and 97.40%, and 97.26 and 98.23%, respectively. The results revealed resistance to fenbendazole, suspect resistance to tetramisole and susceptibility to ivermectin in beneficiary flock. In non-beneficiary flock, while resistance was noticed against fenbendazole, both tetramisole and ivermectin were effective. FECR values were found to be significantly different between beneficiary and non-beneficiary groups against tetramisole. The results of LPA confirmed this finding, as 50% of the Haemonchus contortus larvae were paralyzed at the concentration of 0.0156μg/ml in the beneficiary group, while those of non-beneficiary groups required lower concentrations of 0.0078μg/ml. AS-PCR revealed the predominance of heterozygous susceptible population of H. contortus in the beneficiary group. In this study, resistance to fenbendazole was confirmed in both the beneficiary and non-beneficiary groups and this could be attributed to frequent use of benzimidazoles as seen from the deworming records. Emergence of tetramisole resistance was detected in the beneficiary group, where the drug was used continuously for 4years. Ivermectin was found to be effective in all the flocks. It is recommended that the practice of routine deworming of three to four times a year should be avoided, as it can lead to emergence of anthelmintic resistance.

Keys to solving health problems in small ruminants: Anthelmintic resistance as a threat to sustainable nematode control

The epidemiology of nematode parasites has changed as they have adapted to climatic and management changes and as a consequence of the inappropriate use of anthelmintic drugs. This adaptability is conferred by large, polymorphic genomes and r-reproductive strategies. A significant net effect of these factors has been the emergence of anthelmintic resistance. Consequently, blueprint control programmes have failed and suboptimal sheep productivity due to nematode parasites has become commonplace. The focus of veterinary nematode control in intensively managed sheep flocks and goat herds must shift from attempts to eliminate parasite populations, towards the adoption of management and anthelmintic drug treatment strategies aimed at maintaining adequate standards of health in the face of a low level of challenge. Conventional parasitological methods are useful for the diagnosis of disease and for monitoring of nematode management over time, but they lack the sensitivity needed to mitigate effects of climate and management on population genetics of the parasites. The publication of a draft genome and transcriptome for the model nematode parasite, Haemonchus contortus, affords opportunities for post genomic research to identify sensitive molecular markers to evaluate resistance management strategies and potential candidates for novel control methods.

Efficacy of anthelmintic treatment in captive-reared black stilts (Himantopus novaezelandiae) released to the wild

AIMS: To assess the efficacy of praziquantel (PZQ) administered to control helminths in captive-reared critically endangered black stilts (Himantopus novaezelandiae) before their release into the wild and determine the effect on their survival shortly after release.METHODS: Of 77 captive black stilts, 37 were treated with PZQ prior to release into the wild in South Canterbury, New Zealand, in August and September 2007. Faecal helminth egg counts (FEC) were measured before and after anthelmintic treatment, and before and after release to the wild using modified faecal flotation and sedimentation methods. In addition, total helminth counts were determined in 11 of the birds that died following release, as well as four captive and 11 other wild stilts.RESULTS: The efficacy of PZQ against trematodes was 92% and against Capillaria spp. was 34%. No trematode or Capillaria spp. eggs were detected in treated birds 1 day after treatment, but FEC increased 3–5 days after treatment. There were no differences in the total helminth counts for trematodes, cestodes or Capillaria spp. in control or treated birds (p>0.2). Survival did not differ between treatment groups in the August or September releases (p>0.4). Of control and treated birds, 11/17 (65%) and 8/14 (57%) survived to 31 days, respectively, in the August release, and 16/20 (80%) and 10/15 (67%) survived to 84 days, respectively, in the September release.CONCLUSION: Overall, the results suggest that PZQ treatment may be an unnecessary cost and the risks of producing anthelmintic resistance, injuring the birds during processing or producing an unnecessary stress response at the time of release could exceed any likely benefits.CLINICAL RELEVANCE: It is recommended that pre-release anthelmintic treatment of black stilts should be used only if indicated by health screening. Any treatment should incorporate annual efficacy testing to monitor the emergence of anthelmintic resistance.

Influence of immunoprotection on genetic variability of cysteine proteinases from Haemonchus contortus adult worms

The limitations associated with the use of anthelmintic drugs in the control of gastrotintestinal nematodosis, such as the emergence of anthelmintic resistance, have stimulated the study of the immunological control of many parasites. In the case of Haemonchus contortus, several vaccination trials using native and recombinant antigens have been conducted. A group of antigens with demonstrated immunoprotective value are cathepsin B – like proteolytic enzymes of the cysteine proteinase type. These enzymes, which have been observed in both excretory-secretory products and somatic extracts of H. contortus, may vary among different geographic isolates and on strains isolated from different hosts, or even from the same host, as has been demonstrated in some comparative studies of genetic variability. In the present study, we evaluated the genetic variability of the worms that fully developed their endogenous cycle in immunised sheep and goat in order to identify the alleles of most immunoprotective value. To address these objectives, groups of sheep and goats were immunised with PBS soluble fractions enriched for cysteine proteinases from adult worms of H. contortus from either a strain of H. contortus isolated from goats of Gran Canaria Island (SP) or a strain isolated from sheep of North America (NA). The results confirmed the immunoprophylactic value of this type of enzyme against haemonchosis in both sheep and goats in association with increased levels of specific IgG. The genetic analysis demonstrated that the immunisation had a genetic selection on proteinase-encoding genes. In all the immunised animals, allelic frequencies were statistically different from those observed in non-immunised control animals in the four analysed genes. The reduction in the allelic frequencies suggests that parasites expressing these proteases are selectively targeted by the vaccine, and hence they should be considered in any subunit vaccine approach to control haemonchosis in small ruminants.

Antiparasitic efficacy of a novel plant-based functional food using an Ascaris suum model in pigs

Ascaris lumbricoides is the most prevalent soil-transmitted helminth (STH) infection of human beings worldwide. Chemotherapy with synthetic anthelmintics such as albendazole, mebendazole, and pyrantel pamoate is the current method of treatment; however, the emergence of anthelmintic resistance could substantially decrease the efficacy of such treatments and the sustainability of STH control programs. Additionally, benzimidazoles are not recommended for pregnant women or children under age one. A blinded, controlled study was conducted to evaluate the efficacy of two microencapsulated, plant-based essential oil blends, TTN1013 (α-pinene, linalyl acetate, p-cymene, and thymol octanoate) and TTN1014 (α-pinene, linalyl acetate, p-cymene, and thymol acetate) as functional foods against Ascaris suum infection in pigs, an important pathogen that closely resembles human infections with A. lumbricoides. Four groups of 16 female, 21–24 day old, Yorkshire-cross pigs were treated daily with 0.5 or 1.0mg/kg TTN1013, 1.0mg/kg TTN1014, or 1.0mg/kg equivalent of empty capsules, delivered inside a cream-filled sandwich cookie for 14 weeks. Three days after the initiation of daily treatments, pigs were inoculated daily with A. suum eggs for four weeks. Pigs were weighed weekly and fecal egg counts (FEC) were conducted weekly starting five weeks after initial inoculation with A. suum eggs. Fourteen weeks after first infection with eggs, pigs were necropsied and worms were recovered, counted and separated according to sex. TTN1013 administered daily at a dose of 1.0mg/kg yielded a statistically significant reduction in total worm counts (76.8%), female worm counts (75.5%), FEC (68.6%), and worm volume (62.9%) when compared to control group. Reduction of total and female worm numbers and FEC were not significant for TTN1014 or at the 0.5mg/kg dose of TTN1013. All treatments were well-tolerated by all pigs and did not cause any adverse reactions. All pigs remained clinically normal and showed no signs of reduced intestinal health for the duration of treatment. Based on these results, TTN1013 shows promise as a daily supplement to reduce infection burdens of soil transmitted helminths in both pigs and human beings.