Managing anthelmintic resistance in goats—Can we learn lessons from sheep?

Knowledge, attitudes and practices of Australian dairy goat farmers towards the control of gastrointestinal parasites

BACKGROUND

Gastrointestinal parasites such as nematodes and coccidia are responsible for significant economic losses in the goat industry globally. An indiscriminate use of antiparasitic drugs, primarily registered for use in sheep and cattle, in goats has resulted in drug-resistant gastrointestinal parasites. Very little is known about the gastrointestinal parasite control practices used by Australian dairy goat farmers that are pivotal for achieving sustainable control of economically important parasites. The study reported here provides insights into gastrointestinal parasite control practices of Australian dairy goat farmers based on responses to an online survey.

METHODS

The questionnaire comprised 58 questions on farm demography, husbandry and grazing management, knowledge of gastrointestinal parasites and their importance in dairy goats, diagnosis of infections, antiparasitic drugs and alternate control options. After a pilot survey (n = 15 respondents), a link to the questionnaire was available to all (n = 456) registered members of the Dairy Goat Society of Australia Ltd from 17 April to 16 June 2023. Multiple correspondence analyses (MCA) were performed to explore the association between selected parasite control practices.

RESULTS

A total of 66 (14%) respondents completed the questionnaire. Of these, 74% (49/66) observed parasite-related illnesses in their goats; two-thirds of them assessed worms burden using faecal egg counts (FECs), with 26% (39/149) deworming their goats based on the results of the FECs. Most respondents (97%; 183/188) perceived that gastrointestinal parasites caused production losses and ranked Haemonchus contortus as the most important parasite. Anitparasitic drugs were used by 94% (62/66) of respondents, with the most frequently used anthelmintics being a commercial combination of four anthelmintics (levamisole, closantel, albendazole and abamectin), benzimidazoles and macrocyclic lactones. Most respondents (77%; 51/66) were unaware of anthelmintic resistance on their property. MCA results delineated two clusters of gastrointestinal parasites management.

CONCLUSIONS

This study provides insights into the demography of Australian dairy goat farms, the husbandry and grazing practices used by dairy goat farmers, their knowledge regarding gastrointestinal parasites and their practices for internal parasite control, thereby paving the way for tackling drug resistance in gastrointestinal parasites in dairy goats.

The current status and outlook for insecticide, acaricide and anthelmintic resistances across the Australian ruminant livestock industries: assessing the threat these resistances pose to the livestock sector

The Australian ruminant livestock industries are faced with the need to control parasitic infectious diseases that can seriously impact the health of animals. However, increasing levels of resistance to insecticides, anthelmintics and acaricides are substantially reducing the ability to control some of these parasites. Here we review the current situation with regard to chemical resistances in parasites across the various sectors of the Australian ruminant livestock industries and assess the level of threat that these resistances pose to the sustainability of these sectors in the short to long terms. We also look at the extent to which testing for resistance occurs across the various industry sectors, and hence how well-informed these sectors are of the extent of chemical resistance. We examine on-farm management practices, breeding of parasite-resistant animals, and non-chemical therapeutics that may act as short to long term means to reduce the current reliance on chemicals for parasite control. Finally, we look at the balance between the prevalence and magnitude of current resistances and the availability and adoption rates of management, breeding and therapeutic alternatives in order to assess the parasite control outlook for the various industry sectors.

Immunization with thiol-binding proteins from Haemonchus contortus adult worms partially protects goats against infection during prepatency

To contribute of the knowledge of the immune mechanisms underlying the response to the immunization of goats with thiol-binding proteins fractions (PBS-TSBP) from Haemonchus contortus (H. contortus) adult worms, this study analyzed the degree of protection and the immune responses developed against the parasite after vaccination with this antigenic complex during the time-elapsing between challenge with L3 of the parasite and the development of adult worms, evidenced by the appearance of first faecal eggs (prepatent period or prepatency). Goat kids immunized with PBS-TBSP generated an immune response during the prepatency which translates into a reduction in the number of worms, as well as a lower reduction on packed cell volume and plasma protein levels in relation to the non-vaccinated animals. As previously described in other studies carried out after the prepatent period, this protection was associated with a systemic humoral response. At the local level, a specific humoral response was also observed, together with an immune-inflammatory infiltrate in the gastric mucosa of MCH-II + cells and CD4⁺ lymphocytes, whose number was associated with a reduction in the number of worms and an increase in plasma proteins. A high peripheral eosinophilia was detected, but no corresponding increased infiltration of the gastric mucosa by eosinophils or globular leukocytes was observed. In agreement with previous data on the immunolocalization of the antigens used here, the results obtained contribute to the idea that these may be excretion/secretion (E/S) products necessary for parasite survival, whose inactivation during the larval and/or pre-adult stages may have contributed to immunoprotection.

Reducing anthelmintic inputs in organic farming: Are small ruminant farmers integrating alternative strategies to control gastrointestinal nematodes?

To counter the global spread of anthelmintic resistance (AR), considerable efforts have been invested in the development and dissemination of sustainable alternatives to control gastrointestinal nematode (GIN) infections in small ruminants. The degree to which these have been accepted and integrated by farmers, particularly in organic systems, where the drive to reduce chemical inputs is arguably even more pressing, has been little studied. To identify whether more comprehensive actions are needed to support the uptake of alternative GIN controls amongst organic farmers, this study conducted a survey in five European countries on organic dairy goat and meat sheep farmers to gain insight into current GIN control strategies and farmer attitudes towards AR and alternative measures in these countries. The structured survey was disseminated in the five European countries Switzerland, France, Netherlands, Lithuania and United Kingdom, receiving a total of 425 responses, 106 from organic dairy goat farmers and 319 from organic meat sheep farmers. Regression analyses were carried out to identify factors impacting anthelmintic drenching on meat sheep production systems, whereas all data were analysed descriptively. Four key findings emerged: i) The frequency of anthelmintic treatments averaged less than two per animal a year in all production systems; ii) Overall, organic farmers seemed well informed on the availability of alternative GIN control methods, but fewer stated to put them into practice; iii) Targeted selective treatment (TST) strategies of anthelmintics appears to be not commonly incorporated by organic farmers; iv) Despite operating under national and EU organic regulations, each of the organic dairy goat (Switzerland, France and Netherlands) and meat sheep (Switzerland, Lithuania and United Kingdom) production systems developed distinct approaches for GIN control. To increase uptake of alternatives to GIN control and optimise anthelmintic use, initiatives that promote research dissemination, farmer participatory and knowledge transfer activities at national level would be desirable.

Antibody response and abomasal histopathology of lambs with haemonchosis during supplementation with medicinal plants and organic selenium

We evaluated the effects of dietary supplementation with medicinal plants (Herbmix) or organic selenium (Selplex) on the immune responses and histopathology of lambs infected with Haemonchus contortus. Twenty-seven lambs were infected and reinfected with approximately 11,000 third-stage larvae of H. contortus during the experiment (on days 0, 49 and 77). Lambs were divided into two supplemented experimental groups (Herbmix and Selplex) and unsupplemented group (Control). The abomasal worm counts at necropsy on day 119 were lower for Herbmix (4230) and Selplex group (3220) than to the Control (6613) which resulted in 51.3% and 36.0% of reduction, respectively. The mean length of adult female worms was in the order Control > Herbmix > Selplex (2.1, 2.08, and 2.01 cm, respectively). The specific IgG response against adults was significantly affected by time (P < 0.001). Serum-specific and total mucus levels of IgA in the Herbmix group were highest on day 15. Mean levels of serum IgM against adults were influenced by treatment (P = 0.048) and time (P < 0.001). The Herbmix group had strong local inflammation in the abomasal tissue, with the formation of lymphoid aggregates and the infiltration of immune cells, but the tissues of the Selplex group had higher numbers of eosinophils, globule leukocytes, and plasma cells. The lymph nodes of each animal had reactive follicular hyperplasia due to the infection. Dietary nutritional supplementation with a mixture of medicinal plants or organic selenium could improve local immune responses and thus enhance the resistance of animals to this parasitic infection.

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.

Do water shortages increase gastrointestinal nematode loads in Nguni does?

OBJECTIVE

The objective of the study was to assess the effects of water deprivation on the burden of gastrointestinal nematodes in Nguni does.

METHODS

A survey was piloted on goat keepers in households where water was scarce (n = 143) and where it was available throughout the year (n = 142). In a controlled experiment, feed intake (ADFI), body condition score (BCS), FAMACHA score, packed cell volume (PCV) and faecal egg counts (FEC) were determined in does deprived of water for 24 and 48 h.

RESULTS

There was a significant association between the frequency with which goats drink water and the distance from the water source. From the experiment, an increase in the water deprivation period decreased ADFI, BCS and PCV, and increased FAMACHA scores and faecal egg counts in Nguni goats. The BCS of goats deprived of water for 48 h was 12% lower than the control (p < 0.05).

CONCLUSIONS

Reduction in water supply increased gastrointestinal burdens in does, which may compromise their productivity and production efficiency. Depriving goats of water for 24 h had no significant effect on gastrointestinal nematode (GIN) loads. The deprivation period of 48 h increased the GIN burden in does.

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.

Ovarian activation delays in peripubertal ewe lambs infected with Haemonchus contortus can be avoided by supplementing protein in their diets

BACKGROUND

The ewe lamb nutritional and physiological state interfere with the ovarian environment and fertility. The lack or excess of circulating nutrients reaching the ovary can change its gene expression. A protein deficiency in the blood caused by an Haemonchus contortus abomasal infection is detrimental to the organism's development during puberty. The peripubertal period is a time of intensive growth that requires a high level of nutrients. An essential feature controlling pubertal arousal and female reproductive potential is ovarian follicle growth activation. Protein supplementation improves the sheep's immune response to helminthic infections. We aimed to determine if supplementing protein in infected ewe lambs' diet would impact the ovarian environment leading to earlier ovarian follicle activation than in infected not supplemented animals.

METHODS

We fed 18 Santa Ines ewe lambs (Ovis aries) - bred by the same ram - with either 12% protein (Control groups) or 19% protein (Supplemented groups) in their diets. After 35 days of the diet, they were each artificially infected or not with 10,000 Haemonchus contortus L3 larvae. Following 77 days of the diet and 42 days of infection, we surgically collected their left ovaries and examined their genes expression through RNA sequencing.

RESULTS

We found that protein supplementation in infected animals led to an up-regulation of genes (FDR p-values < 0.05) and biological processes (p-value cut-off = 0.01) linked to meiotic activation in pre-ovulatory follicles and primordial follicle activation, among others. The supplemented not infected animals also up-regulated genes and processes linked to meiosis and others, such as circadian behaviour. The not supplemented animals had these same processes down-regulated while up-regulated processes related to tissue morphogenesis, inflammation and immune response.

CONCLUSION

Diet's protein supplementation of peripubertal infected animals allowed them to express genes related to a more mature ovarian follicle stage than their half-sisters that were not supplemented. These results could be modelling potential effects of the interaction between environmental factors, nutrition and infection on reproductive health. When ovarian activation is achieved in a timely fashion, the ewe may generate more lambs during its reproductive life, increasing sheep breeders' productivity.

Anthelmintic effect of essential rhizome oil from Hedychium coronarium Koenig (Zingiberaceae) introduced in Northeastern Brazil

Hedychium coronarium is native to Tropical Asia and has been introduced into several Brazilian biomes. Significant biological properties described for the essential oil (EO) from this species' rhizomes include antimicrobial, larvicidal, anti-inflammatory, antioxidant, phytotoxic, and anthelmintic activities. The primary constituents identified in this study by GC-MS in the EO were monoterpenes 1,8-cineole (33.5%), β-pinene (17.0%), α-terpineol (7.7%), α-pinene (7.3%), limonene (5.2%), and p-cymene (4.9%), comprising 75.6% of total oil compounds. The main monoterpenes' EO and standards were tested against N2 (susceptible) and UVR15 (resistant) adult nematode Caenorhabditis elegans strains, with varying dead rates in motility tests.. Nematocidal activity was not attributed to 1,8-cineole and β-pinene, the main H. coronarium rhizome oil components, as both exhibited an inhibitory concentration (IC₅₀) ≥ 5 mg/mL. On the other hand, the α-pinene (IC₅₀, 1.69 mg/mL) and (S)-(-)-limonene (IC₅₀, 1.66 mg/mL) standards demonstrated more efficient action than rhizome oil in motility tests, with significant adult C. elegans nematode mortality rates. These results support the hypothesis that the combination of H. coronarium EO constituents can be helpful as a nematicidal product, due to their synergistic action.

Survey on Endoparasites of Dairy Goats in North-Eastern Italy Using a Farm-Tailored Monitoring Approach

With the spread of anthelmintic resistance (AR), endoparasite monitoring consolidates its role for a more sustainable targeting of treatments. A survey on endoparasites in dairy goat farms of north-eastern Italy was conducted to test a monitoring approach based on a farm-tailored sample size. Farm management and parasites control practices were investigated in 20 farms through a questionnaire survey. Further, fecal samples were collected (November 2018–September 2019) from 264 animals from 13 farms and were analyzed individually with a modified McMaster method and subsequently pooled to perform a coproculture. Coccidia (78.4%), gastrointestinal strongyles (37.9%), Strongyloides (28.4%), Skrjabinema (18.9%), Trichuris (8.0%) and Nematodirus/Marshallagia (0.4%) were identified. Abundances were higher for coccidia and gastrointestinal strongyles. Haemonchus (71%) was the dominant gastrointestinal nematode. Pasture and age class resulted in the main risk factors at the multivariable analysis through a negative binomial regression model. Results from farm monitoring indicate that our approach can be a cost-effective decision tool to target treatments more effectively, but farmers need to be educated about the importance of parasitological testing, which is currently scarcely implemented, against the risk of AR.

Resistance of strongylid nematodes to anthelmintic drugs and driving factors at Czech goat farms

Background

Strongylid nematode infections may negatively affect both animal health and welfare, with deleterious consequences for livestock productivity. Many farmers in recent decades have relied on anthelmintics as the sole strategy of control, but the intensive use of these chemotherapeutics has led to the development of anthelmintic resistance (AR). Knowledge of both the efficacy of anthelmintics and factors promoting AR are essential to effectively control nematode infections, but no information on these topics for goats in the Czech Republic (CR) is available. This survey aimed to determine the occurrence of AR at Czech goat farms and to identify risk factors for the development of AR. A total of 24 herds of dairy goats across the CR were evaluated using in vitro tests for detecting AR, and a questionnaire survey was carried out to evaluate factors associated with AR.

Results

Resistance against benzimidazoles was confirmed at 18 (75%) farms, and the level of resistance was high in four (22%) of the affected herds based on the egg hatch test. Ivermectin-resistant nematodes were detected in 13 (54%) herds using the larval development test; Teladorsagia/Trichostrongylus and Haemonchus were the predominant types of resistant larvae. Eight (62%) of the affected herds were evaluated as highly resistant to ivermectin. Eleven (46%) of the herds were resistant to both benzimidazoles and ivermectin. This report is the first on dual AR in the CR. A univariate logistic regression analysis indicated that a high stocking rate and farmer inexperience were significantly associated with ivermectin and benzimidazole resistance, respectively.

Conclusions

The results of our survey suggest that AR is widespread amongst herds of dairy goats in the CR, likely due to inappropriate practices of pasture and health management. AR may be an issue for expanding dairy-goat production in the CR in the near future unless both veterinary practitioners and farmers widely adopt strategies to prevent the development of AR.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02819-8.

Effect of Artemisia absinthium and Malva sylvestris on Antioxidant Parameters and Abomasal Histopathology in Lambs Experimentally Infected with Haemonchus contortus

This study evaluated the effect of Artemisia absinthium and Malva sylvestris on antioxidant response and histopathological changes in the abomasa of the Haemonchus contortus infected lambs. Twenty-four lambs were divided into four groups: unsupplemented lambs (UNS), lambs supplemented with A. absinthium (ART), lambs supplemented with M. sylvestris (MAL), and lambs supplemented with both plants (ARTMAL). Lambs were infected orally with approximately 5000 third-stage (L3) larvae of H. contortus. The experiment was conducted for 75 d (days), all animals were then slaughtered; and the abomasal tissues were examined for antioxidant parameters and histopathology. The concentration of malondialdehyde in the abomasal mucosa was lower in ARTMAL (p < 0.05), and the total antioxidant capacity was higher in MAL (p < 0.05), than in UNS. Increased mucus production was observed in the ARTMAL. The number of mast cells in UNS and ART was significantly higher than the number in MAL (p < 0.01 and p < 0.05). Plasma cell numbers were higher in ARTMAL than the number in MAL (p < 0.05). Abomasal tissue regenerated more frequently in ARTMAL. These results represent the first report of the impact of A. absinthium and M. sylvestris on antioxidant parameters and local immune responses of abomasal mucosa of lambs infected with a GIN parasite.

Structure of parasite cenosis of endoparasitoses of ruminants

The infestation was studied and the structure of the parasite cenosis of ruminants of the Udmurt Republic was characterized. Over the period of several years of research (2016-2020), a diverse parasitophauna was identified. According to the results of the research, it was established that cattle is mainly invaded by Eimeria spp., nematodes of the Strongylata suborder, dicroceliosis dominates from trematode infestations. The maximum infection rate was noted by eimeriosis invasion, during the entire time of the studies it varied from 87.84 % to 77.73 %, which indicates a tendency to increase invasion and stationary problems of farms. The features of competitive relationships are clearly traced in hepatic flukes: dicrocoeliums and fascioles. Dicrocoeliotic invasion prevails on average by 32 %, which indicates a partial manifestation of antagonism.When analyzing the generic structure of the parasite complex of cattle, on average for five years, it was found that the largest share is occupied by Eimeria spp - 44.35, Strongylata - 30.52, Dicrocoelium - 17.52, Fasciola - 6.43, Eurythrema – 0.67 and Trichostrongylus – 0.51 are less represented. A retrospective epizootic analysis of parasitoses showed that sheeps, like cattle, have a diverse parasitophauna, but in the first case, the detection of monoinvasions is 3.5 times higher. In the structure of sheep parasite cenosis, similar indicators of infection with Eimeria spp, Strongyloides, Moniezia were found, generic indices ranged from 24.18 to 27.61. Strongylatosis of the gastrointestinal tract are replaced by Strongyloides. A significant change was also observed in the group of trematode infestations. Unlike cattle, fasciolosis prevails in sheep with a maximum value of 9.5 times in 2019, while dicroceliosis was not registered at all in 2017. In the sheep parasite complex, moniesiosis occupies the main share – 27.61, which may be related to the conditions of keeping, since sheeps are grazing for a long time and a meeting with intermediate hosts - oribatid mites is inevitable.

Small Ruminant Production Based on Rangelands to Optimize Animal Nutrition and Health: Building an Interdisciplinary Approach to Evaluate Nutraceutical Plants

The plant kingdom can influence the productivity and health of herbivores at different levels. However, demonstrating this process in a scientific manner entails substantial endeavors from different disciplines. In the present review, we will describe the features of a native vegetation system traditionally used by small ruminants and use its particularities to build an interdisciplinary approach to evaluate the nutraceutical properties of plants. Initially, we will establish the context of the low deciduous forest (LDF), considering some botanical and nutritional aspects, as well as the presence of plant secondary compounds (PSC) and gastrointestinal nematodes (GIN). Furthermore, we will focus on coevolutionary aspects that undoubtedly shaped the plants-nutrients-PSC-GIN-herbivore relationship. In addition, the concept of nutraceutical will be discussed to provide clarity and aspects to be considered for their evaluation. Then, ethological, agronomical, nutritional, PSC, parasitological and animal species issues are deepened placing emphasis on methodological approaches. Special focus is given to condensed tannins, as they are the fourth largest group of PSCs and the most studied in livestock sciences. Validation of the nutraceutical properties of plants from native vegetation systems should be seen as a process derived from many scientific disciplines that feed into each other in a cyclic manner.

Drug discovery technologies: Caenorhabditis elegans as a model for anthelmintic therapeutics

Helminthiasis is one of the gravest problems worldwide. There is a growing concern on less available anthelmintics and the emergence of resistance creating a major threat to human and livestock health resources. Novel and broad-spectrum anthelmintics are urgently needed. The free-living nematode Caenorhabditis elegans could address this issue through automated high-throughput technologies for the screening of large chemical libraries. This review discusses the strong advantages and limitations for using C elegans as a screening method for anthelmintic drug discovery. C elegans is the best model available for the validation of novel effective drugs in treating most, if not all, helminth infections, and for the elucidation the mode of action of anthelmintic candidates. This review also focuses on available technologies in the discovery of anthelmintics published over the last 15 years with particular attention to high-throughput technologies over conventional screens. On the other hand, this review highlights how combinatorial and nanomedicine strategies could prolong the use of anthelmintics and control resistance problems.

In vitro effects of tannin and extracts of Bridelia ferruginea and Mitragyna inermis on the exsheathment of infective larvae of Haemonchuscontortus

Bridelia ferruginea (Euphorbiaceae) and Mitragyna inermis (Rubiaceae) are two plants of the beninese pharmacopeia used in vivo for the control of gastrointestinal nematodes (GINs) in small ruminants. The objective of the present study is to explore the mechanism of bioactive compounds involved in the action of these two plants on the third-stage infective larvae (L3s) of Haemonchus contortus. Thus, sheathed L3s of H. contortus were incubated with acetone extracts of B. ferruginea and M. inermis at concentrations of 0, 150, 300, 600 and 1200 µg/mL for 3 h at 25°C. The L3s were then washed and artificially submitted to exsheathment in the presence of sodium hypochlorite solution. The role of tannins was verified by adding a tannin inhibitor, polyvinyl polypyrrolidone (PVPP), to the acetone extracts of these two plants for 2 h at 25°C. Acetone extracts from B. ferruginea and M. inermis inhibited the exsheathment of H. contortus larvae (p < 0.001) and this inhibitory effect was dose-dependent for M. inermis at the concentrations tested. Treatment of B. ferruginea and M. inermis extracts with PVPP was associated with a partial restoration of the exsheathment kinetics of H. contortus larvae (p < 0.001), confirming the predominant role of tannins but also the residual role of other secondary metabolites. These in vitro results suggest that these plants are endowed with anthelmintic (AHs) properties and therefore likely to be used as alternatives to synthetic molecules.

Review of the Eprinomectin effective doses required for dairy goats: Where do we go from here?

Eprinomectin (EPM) has been recently granted a marketing authorisation in the European Union for use in goats, with a zero-day milk withdrawal period. Considering the high prevalence of benzimidazole resistance worldwide and the economic implications of managing milk residues, EPM may today be considered the main (or even the only) affordable treatment option, at least in dairy goats in the EU. However, the chosen dose (1 mg/kg) seems to be suboptimal, especially for lactating goats, and the chosen route of administration (Pour-on) highly subject to inter-individual variability. Considering the scarcity of anthelmintic resources, such a dosage regimen might threat the sustainability of this crucial drug in goat milk production and needs to be urgently discussed and reassessed.

A producer survey of knowledge and practises on gastrointestinal nematode control within the Australian goat industry

Gastrointestinal nematodes (GINs) have been identified in Australia as a major problem in goat production, with few anthelmintics registered for use in goats. Therefore, anecdotally many producers use anthelmintics that have not been registered for goats. Using unregistered products could increase selection pressure for anthelmintic resistance as well as safety and/or meat or milk chemical residues of products from treated goats. This producer survey was conducted in 2014 to establish Australian goat producer knowledge, perception and practises of GIN treatment and control. Eighty-eight producers responded to the survey. Of these respondents, 90% thought that GINs were a problem for the Australian goat industry, and 73% considered GINs had caused production losses or health impacts for their goats during the 5 years prior to the survey. With regard to anthelmintic resistance, 7% believed that anthelmintic resistance was not a problem at all, 93% acknowledged anthelmintic resistance was a problem in Australian goats herds, with 25% of these reporting their properties as being affected. The majority (81%) of respondents believed the number of anthelmintics registered for goats was inadequate for effective GIN control. Of the 85% of producers who used an anthelmintic during the survey period, 69% had used a treatment not registered for use in goats. Fifty respondents listed the anthelmintic dosage used, and 50% of those had used a dose rate greater than the recommended label dose. The average frequency of administration of anthelmintic was 2.5 times per annum. Of the 51% of respondents who listed the frequency of their treatments given during the survey period, 16% administered four or more treatments annually to the majority of their goats and 8% administered treatments on an "as needed" basis. Faecal egg count (FEC) had been performed on 72% of properties in at least one of the six years covered by the survey. These results indicated that the majority of surveyed producers use anthelmintics that are not registered for use in goats and at different dose rates to label. These practises have the potential for increasing the spread of anthelmintic resistance in the GIN populations of goats and sheep. Further, giving dose rates in excess of label recommendations could impact goat safety and/or product residues. Further research is needed to investigate these risks and evaluate more sustainable GIN control options for goat herds. In addition more effective dissemination of information is necessary for the improvement of the Australian goat industry.

Phenotypic resistance of indigenous goat breeds to infection with Haemonchus contortus in northwestern Nigeria

Two studies at the National Animal Production Research Institute (NAPRI), Zaria, Nigeria, compared Red Sokoto (RS), Sahelian (SG), and West African Dwarf (WAD) goats after experimental or natural infection with Haemonchus contortus. In the first study, 20 RS, 17 SG, and 14 WAD kids were challenged at 6 months of age with 5000 L₃ larvae of H. contortus. Fecal egg counts (FEC), packed cell volumes (PCV), and body weights (BW) were recorded 0, 28, 35, and 42 days after infection. The FEC and PCV were affected only by time of measurement. In the second study, 322 RS and 97 SG kids were produced at NAPRI over 3 years, weaned at 4 to 6 months of age, dewormed, returned to contaminated pastures, and evaluated 28 and 35 days later. Effects of breed, year, breed × time interaction, and breed × year interaction were observed for PCV and BW; FEC was only affected by time of measurement, year and breed × year interaction. The FEC were larger and PCV were smaller on day 35 compared to day 28 and in year 2 compared to years 1 and 3. The SG kids were notably smaller than RS kids in year 2, with higher FEC and lower PCV, but FEC were larger for RS kids in years 1 and 3. Differences in parasite resistance among these Nigerian goat breeds were therefore small and likely reflected underlying differences in growth, development, and disease history.

Criollo goats limit their grass intake in the early morning suggesting a prophylactic self-medication behaviour in a heterogeneous vegetation

The present study compared the feeding behaviour of goats in the early morning (EM = 7:00-8:30 a.m.) and late morning (LM = 9:30-11:00 a.m.) in response to their natural gastrointestinal nematode (GIN) infection status. Twelve female adult goats (37 ± 7.7 kg live weight (LW); 5 ± 1 years) with browsing experience in the tropical deciduous forest were divided into two groups (n = 6): INF group, with natural GIN infection, and non-infected (NI) group, dewormed with moxidectin (0.4 mg/kg LW subcutaneous). Feeding behaviour (dry matter intake (DMI)) of two resource types (grasses vs. shrubs + herbs) was estimated by direct observation for 4 weeks on two grazing moments (EM vs. LM). Environmental temperature and relative humidity at pasture level were measured twice weekly. The GIN egg counts and goats' LW were measured on days 0, 14 and 28. Temperature (mean ± standard deviation) at EM (26.2 ± 1.5 °C) was lower than at LM (38.7 ± 1 °C; P < 0.01). Humidity was higher on the EM (85.1 ± 2.6%) compared to LM (60.4 ± 5.6%; P < 0.01). Irrespective of the infection status, goats consumed similar amounts of grass and shrubs + herbs during EM (P > 0.05). On the other hand, the experimental groups consumed more grass than shrubs + herbs during LM (P < 0.05). The latter suggested prophylactic behaviours strategies to (a) avoid GIN infective larvae, (b) balance the protein:energy ratio of the diet and (c) avoid saturation of detoxification pathways for the secondary compounds consumed from shrubs + herbs. The constant consumption of shrubs + herbs during the study may have reduced the GIN egg count of the INF group.

In Vitro Anthelminthic Efficacy of Hypoestes forskaolii (Vahl) R.Br (Acanthaceae) Extracts on Gastrointestinal Nematodes of Sheep

The anthelminthic efficacy of the crude extracts of Hypoestes forskaolii (Vahl) R.Br (Acanthaceae) against gastrointestinal nematodes (GIN) in sheep was investigated using the in vitro egg hatch inhibition assay. Faecal samples were collected from sheep with naturally occurring infection of GIN (Trichostrongylus spp., Chabertia ovina, Cooperia spp., Haemonchus contortus and Teladorsagia spp.). Crude leaf extracts of H. forskaolii was obtained using increasing polarity solvents: n-hexane, chloroform, chloroform:methanol 9:1, methanol. Thiabendazole (0.2 µg/mL and 0.5 µg/mL) was used as a positive control and untreated GIN eggs in deionised water served as the negative control. All the extracts exhibited a weak ovicidal activity against GIN (less than 50% of egg hatch). Noteworthy, the n-hexane extract showed a percentage of inhibition of egg hatching greater than other extracts inhibiting the 30.8% at the concentration of 1 mg/mL showing a dose-dependent effect on nematode eggs hatching. Further studies are needed to investigate the effects of extracts used and to evaluate the ovicidal effects of other extracts of H. forskaolii.

Anthelmintic effect of thymol and thymol acetate on sheep gastrointestinal nematodes and their toxicity in mice

Thymol is a monoterpene and acetylation form of this compound can reduce the toxicity and enhance its biological effects. The objective of this study was to evaluate the effect of thymol and thymol acetate (TA) on egg, larva and adult Haemonchus contortus and the cuticular changes, acute toxicity in mice and the efficacy on sheep gastrointestinal nematodes. In vitro tests results were analyzed by analysis of variance (ANOVA) and followed by comparison with Tukey test or Bonferroni. The efficacy of in vivo test was calculated by the BootStreet program. In the egg hatch test (EHT), thymol (0.5 mg/mL) and TA (4 mg/mL) inhibited larval hatching by 98% and 67.1%, respectively. Thymol and TA (8 mg/mL) inhibited 100% of larval development. Thymol and TA (800 µg/mL) reduced the motility of adult worms, by 100% and 83.4%, respectively. Thymol caused cuticular changes in adult worm teguments. In the acute toxicity test, the LD50 of thymol and TA were 1,350.9 mg/kg and 4,144.4 mg/kg, respectively. Thymol and TA reduced sheep egg count per gram of faeces (epg) by 59.8% and 76.2%, respectively. In in vitro tests thymol presented better anthelmintic activity than TA. However TA was less toxic and in in vivo test efficacy was similar.

Monepantel resistant Trichostrongylus colubriformis in goats in Brazil

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

Caffeoyl and coumaroyl derivatives from Acacia cochliacantha exhibit ovicidal activity against Haemonchus contortus

ETHNOPHARMACOLOGY RELEVANCE

Acacia cochliacantha is a small tree whose foliage is traditionally used in Mexico for treatment of kidney pain, gastrointestinal illnesses and to kill intestinal parasites. In recent decades, the study of vegetal extracts has offered other possible alternatives for the control of Haemonchus contortus. Considering that this nematode affects dramatically the health and productivity of small ruminants, the aim of this study was to identify the anthelmintic compounds from A. cochliacantha hydro-alcoholic extract (HA-E) through an ovicidal test.

MATERIAL AND METHODS

In vitro egg hatch assay was conducted to determinate the anthelmintic effects of a HA-E (60g). Liquid-liquid ethyl acetate/water extraction gave two fractions (EtOAc-F, 1.92g; Aq-F; 58.1g). The less polar compounds from ethyl acetate fraction were extracted by addition of dichloromethane offering a precipitate phase (Mt-F, 1.25g) and a soluble mixture (DCMt-F 1.15g). All fractions were evaluated for ovicidal activity obtaining the egg hatching inhibition (EHI, 0.07-25mg/mL). Ivermectin (0.5mg/mL) was used as a reference drug (positive control), and distilled water, 2.5% DMSO and 2% methanol were used as negative controls. The isolated compounds from the most active fractions were subjected to spectroscopic (¹H NMR) Spectrometric (MS) and UV HPLC analysis in order to identify the bioactive compounds.

RESULTS

The less polar treatments (AcOEt-F, DCMt-F, DCMt-P) showed the highest ovicidal activities (98-100% EHI; at 0.62-1.56mg/mL) and the major compounds found in these fractions were identified as caffeoyl and coumaroyl derivatives, including caffeic acid (1), p-coumaric acid (2), ferulic acid (3), methyl caffeate (4), methyl-p-coumarate (5), methyl ferulate (6) and quercetin. In case of the less active fractions (Aq-F, Mt-F) were constituted principally by glycosylated flavonoids.

CONCLUSION

These results show that caffeoyl and coumaroyl derivatives from Acacia cochliacantha leaves had promising anthelmintic activity against Haemonchus contortus. This leguminous may offer an alternative source for the control of gastrointestinal nematodes of small ruminants.

Genotypic profile of benzimidazole resistance associated with SNP F167Y and F200Y beta-tubulin gene in Brazilian populations of Haemonchus contortus of goats

Benzimidazoles are the most common anthelminthic used for control of gastrointestinal nematodes of goats in the Brazilian semi-arid region. Resistance to these compounds in the nematode Haemonchus contortus has been associated with single nucleotide polymorphisms (SNP) in codons 167 (F167Y) and 200 (F200Y) on the β-tubulin isotype 1 gene. To determine the resistance profile to benzimidazoles of populations of H. contortus of goats of Brazilian semi-arid region, larvae of 29 populations of these nematodes were individually genotyped by real time PCR using a Taqman assay. The percentage of larvae homozygous (RR) for SNP F200Y was relatively low (18.9%), particularly when compared to SNP F167Y (32.7%), indicating that the latter has more relevance in this region. However, the associations between these two SNP demonstrate percentages of resistance ranging from 34.7% to 100% between populations, being the highest percentages for homozygous individuals resistant for the mutation 167 and susceptible to mutation 200 (RR-F167Y/F200Y-SS: 26.7%), followed by combination of heterozygous for both mutations (F167Y-SR/F200Y-SR: 22.8%). These results indicate high levels of resistance in populations of H. contortus of goats in the Brazilian semi-arid region, and thus ineffective antiparasitic control with the use of benzimidazoles in the region.

In vitro control of parasitic nematodes of small ruminants using some plant species containing flavonoids

This study determined in vitro anthelmintic efficacy of three plant species: Trema orientalis, Urtica dioica and Zanthozylum capense on nematode larvae of small ruminants. Dried leaf samples (40 g) were extracted in 70% ethanol, in portions of 10 g and concentrated to 100 ml. Half and one quarter of the original crude extract were both made to 100 ml. Rectal faecal material from 10 Merino sheep and 25 Nguni goats was pooled within species and thoroughly hand-mixed. Dung samples, each of 5 g were cultured for 12 days at 27 °C. On day 13, 4 plates were watered and 4 others treated with ethanol to correct for solvent effect on mortality. The design was 2 (animal species) × 3 (plant species) × 3 (extract concentrations). In each of three runs, three plates were treated with each crude extract in three incremental concentrations. Surviving L3 larvae were isolated, counted and mortalities became indices of anthelmintic efficacy. Data from nematode larval mortality were analysed to determine the effect of animal species, plant species, concentration and their interactions. Efficacy was affected by concentration (P = 0.0001), animal species (P = 0.0046), plant species (P = 0.0572), the interactions of animal species and concentration (P = 0.0010), plant species and concentration (P = 0.0123) and concentration × animal × plant species (P = 0.0435).

Interactions Between Nutrition and Infections With Haemonchus contortus and Related Gastrointestinal Nematodes in Small Ruminants

Interactions between host nutrition and feeding behaviour are central to understanding the pathophysiological consequences of infections of the digestive tract with parasitic nematodes. The manipulation of host nutrition provides useful options to control gastrointestinal nematodes as a component of an integrated strategy. Focussed mainly on the Haemonchus contortus infection model in small ruminants, this chapter (1) illustrates the relationship between quantitative (macro- and micro-nutrients) and qualitative (plant secondary metabolites) aspects of host nutrition and nematode infection, and (2) shows how basic studies aimed at addressing some generic questions can help to provide solutions, despite the considerable diversity of epidemiological situations and breeding systems.

Diagnosis, Treatment and Management of Haemonchus contortus in Small Ruminants

Haemonchus contortus is a highly pathogenic, blood-feeding nematode of small ruminants, and a significant cause of mortalities worldwide. Haemonchosis is a particularly significant threat in tropical, subtropical and warm temperate regions, where warm and moist conditions favour the free-living stages, but periodic outbreaks occur more widely during periods of transient environmental favourability. The clinical diagnosis of haemonchosis is based mostly on the detection of anaemia in association with a characteristic epidemiological picture, and confirmed at postmortem by the finding of large numbers of H. contortus in the abomasum. The detection of impending haemonchosis relies chiefly on periodic monitoring for anaemia, including through the 'FAMACHA' conjunctival-colour index, or through faecal worm egg counts and other laboratory procedures. A range of anthelmintics for use against H. contortus is available, but in most endemic situations anthelmintic resistance significantly limits the available treatment options. Effective preventative programmes vary depending on environments and enterprise types, and according to the scale of the haemonchosis risk and the local epidemiology of infections, but should aim to prevent disease outbreaks while maintaining anthelmintic efficacy. Appropriate strategies include animal management programmes to avoid excessive H. contortus challenge, genetic and nutritional approaches to enhance resistance and resilience to infection, and the monitoring of H. contortus infection on an individual animal or flock basis. Specific strategies to manage anthelmintic resistance centre on the appropriate use of effective anthelmintics, and refugia-based treatment schedules. Alternative approaches, such as biological control, may also prove useful, and vaccination against H. contortus appears to have significant potential in control programmes.

Anthelmintic activity of acetone-water extracts against Haemonchus contortus eggs: interactions between tannins and other plant secondary compounds

This study aimed at (i) describing the effects of acetone-water extracts obtained from a range of different plant materials, on the hatching process of Haemonchus contortus eggs under in vitro conditions and (ii) identifying the role of tannins and other plant secondary compounds (PSC), on these AH effects by using polyvinylpolypyrrolidone (PVPP), an inhibitor of tannins and other polyphenols. An egg hatch assay (EHA) was used to determine the AH effect. Acetone-water (70:30) extracts from different foliages (Lysiloma latisiliquum, Laguncularia racemosa, Rizophora mangle, Avicennia germinans) and plant by-products (Theobroma cacao seed husk and pulp, and percolated Coffea arabica) were obtained. Fresh H. contortus eggs were incubated in PBS with increasing concentrations of each extract (0, 600, 1200, 2400 and 3600 μg/ml PBS). A general linear model was used to determine the dose effect of each extract. A mild ovicidal activity was only recorded for T. cacao extracts (seed husk and pulp). The main anthelmintic (AH) effect for all the extracts, except for C. arabica, was to block the eclosion of larvated eggs. The use of PVPP at 3600 μg/ml PBS showed that tannins of the L. racemosa extract were responsible for blocking eclosion of larvated eggs. Extracts of L. latisiliquum, A. germinans, T. cacao seed husk and pulp also blocked eclosion of larvated eggs but the addition of PVPP indicated that tannins were not responsible for that activity. In contrast, it suggested unfavorable interactions between polyphenols and other PSC contained in those extracts, limiting the AH effect on the egg hatching process. The present results suggest that the interactions between tannins and other PSC are complex and may reduce the AH effects against H. contortus eggs.

Worm-control practices and prevalence of anthelmintic resistance using in vivo FECRTs on smallholder sheep farms in Lithuania

This study determined the prevalence of anthelmintic resistance (AR) in parasitic nematodes on smallholder sheep farms in Lithuania from April to November 2014. Faecal samples were collected from two groups of 10-15 sheep treated with fenbendazole (FBZ) or ivermectin (IVM) on 18 sheep farms. Two samples were collected from each group: on day zero (T1) and 10-14 days after treatment. Faecal egg counts (eggs per gramme, EPG) were determined using a modified McMaster technique. Animals with < 140 EPG on day zero were removed from the analysis. The prevalence of AR was estimated using the in vivo faecal egg count reduction test. AR to FBZ was detected on three of 15 farms where FBZ was used (20 %) and was suspected on one farm (6.7 %). AR to IVM was detected on two of 16 farms where IVM was used (12.5 %). The main species of resistant gastrointestinal nematodes (GINs) identified after treatment were Teladorsagia spp. and Trichostrongylus spp. A questionnaire surveying 71 sheep farmers estimated that 71.8 % of sheep farmers used anthelmintics against GINs. IVM was the most frequently (68.6 %) applied anthelmintic, and 62.7 % of the respondents reported treating their animals twice a year. This study confirmed the presence of AR to GIN infections on sheep farms in Lithuania. Future studies should assess the prevalence of AR to GIN infection using in vitro methods.

The 'Toolbox' of strategies for managing Haemonchus contortus in goats: What's in and what's out

A dynamic and innovative approach to managing the blood-consuming nematode Haemonchus contortus in goats is critical to crack dependence on veterinary anthelmintics. H. contortus management strategies have been the subject of intense research for decades, and must be selected to create a tailored, individualized program for goat farms. Through the selection and combination of strategies from the Toolbox, an effective management program for H. contortus can be designed according to the unique conditions of each particular farm. This Toolbox investigates strategies including vaccines, bioactive forages, pasture/grazing management, behavioural management, natural immunity, FAMACHA, Refugia and strategic drenching, mineral/vitamin supplementation, copper Oxide Wire Particles (COWPs), breeding and selection/selecting resistant and resilient individuals, biological control and anthelmintic drugs. Barbervax(®), the ground-breaking Haemonchus vaccine developed and currently commercially available on a pilot scale for sheep, is prime for trialling in goats and would be an invaluable inclusion to this Toolbox. The specialised behaviours of goats, specifically their preferences to browse a variety of plants and accompanying physiological adaptations to the consumption of secondary compounds contained in browse, have long been unappreciated and thus overlooked as a valuable, sustainable strategy for Haemonchus management. These strategies are discussed in this review as to their value for inclusion into the 'Toolbox' currently, and the future implications of ongoing research for goat producers. Combining and manipulating strategies such as browsing behaviour, pasture management, bioactive forages and identifying and treating individual animals for haemonchosis, in addition to continuous evaluation of strategy effectiveness, is conducted using a model farm scenario. Selecting strategies from the Toolbox, with regard to their current availability, feasibility, economical cost and potential ease of implementation depending on the systems of production and their complementary nature, is the future of managing H. contortus in farmed goats internationally and maintaining the remaining efficacy of veterinary anthelmintics.

LivestockPlus: Forages, sustainable intensification, and food security in the tropics

The increased use of grain-based feed for livestock during the last two decades has contributed, along with other factors, to a rise in grain prices that has reduced human food security. This circumstance argues for feeding more forages to livestock, particularly in the tropics where many livestock are reared on small farms. Efforts to accomplish this end, referred to as the 'LivestockPlus' approach, intensify in sustainable ways the management of grasses, shrubs, trees, and animals. By decoupling the human food and livestock feed systems, these efforts would increase the resilience of the global food system. Effective LivestockPlus approaches take one of two forms: (1) simple improvements such as new forage varieties and animal management practices that spread from farmer to farmer by word of mouth, or (2) complex sets of new practices that integrate forage production more closely into farms' other agricultural activities and agro-ecologies.

Anthelmintic Activities against Haemonchus contortus or Trichostrongylus colubriformis from Small Ruminants Are Influenced by Structural Features of Condensed Tannins

Plants containing condensed tannins (CTs) may hold promise as alternatives to synthetic anthelmintic (AH) drugs for controlling gastrointestinal nematodes (GINs). However, the structural features that contribute to the AH activities of CTs remain elusive. This study probed the relationships between CT structures and their AH activities. Eighteen plant resources were selected on the basis of their diverse CT structures. From each plant resource, two CT fractions were isolated and their in vitro AH activities were measured with the larval exsheathment inhibition assay, which was applied to Haemonchus contortus and Trichostrongylus colubriformis. Calculation of mean EC50 values indicated that H. contortus was more susceptible than T. colubriformis to the different fractions and that the F1 fractions were less efficient than the F2 ones, as indicated by the respective mean values for H. contortus, F1 = 136.9 ± 74.1 μg/mL and F2 = 108.1 ± 53.2 μg/mL, and for T. colubriformis, F1 = 233 ± 54.3 μg/mL and F2 = 166 ± 39.9 μg/mL. The results showed that the AH activity against H. contortus was associated with the monomeric subunits that give rise to prodelphinidins (P < 0.05) and with CT polymer size (P < 0.10). However, for T. colubriformis AH activity was correlated only with prodelphinidins (P < 0.05). These results suggest that CTs have different modes of action against different parasite species.

Synergistic inhibition of Haemonchus contortus exsheathment by flavonoid monomers and condensed tannins

This study investigated the separate and combined anthelmintic (AH) effects of different phenolic compounds, including condensed tannins and flavonoids, all of which are known to occur in willow leaves, a potentially valuable dry season feed. A range of contrasting model tannins, which span the whole range of willow tannins, were isolated from tilia flowers, goat willow leaves, black currant leaves and red currant leaves. All together, the tested compounds represented the major tannin types (procyanidins and prodelphinidins) and flavonoid types (flavonols, flavones and flavanones). The larval exsheathment inhibition assay (LEIA) was used to assess their in vitro effects on Haemonchus contortus third stage larvae. Arbutin, vanillic acid, and taxifolin proved to be ineffective whereas naringenin, quercetin and luteolin were highly effective at 250 μM concentrations. Procyanidin (PC) tannins tended to be less active than prodelphinidin tannins (PD). Experiments with combinations of tannins and quercetin or luteolin revealed for the first time the existence of synergistic AH effects between tannins and flavonoid monomers. They also provided evidence that synergistic effects appear to occur at slightly lower concentrations of PC than PD. This suggests that the AH activity of condensed tannins can be significantly enhanced by the addition of quercetin or luteolin. This information may prove useful for plant breeding or selection and for designing optimal feed mixtures.

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Tannins and flavonoids showed anti-parasitic effects against Haemonchus contortus.

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This is the first report of their synergistic effects on larval exsheathment.

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Flavonoids enhanced especially the anthelmintic activities of procyanidin tannins.

Tannin containing legumes as a model for nutraceuticals against digestive parasites in livestock

Parasitic infections with gastrointestinal nematodes (GINs) still represent a worldwide major pathological threat associated with the outdoor production of various livestock species. Because of the widespread resistance to synthetic chemical anthelmintics, there is a strong impetus to explore novel approaches for a more integrated management of these infections. The use of nutraceuticals in the control of GINs is one of the alternatives which has been widely studied for 20 years. The objectives of this review are: (i) to define and illustrate the concept of 'nutraceutical' in the context of veterinary parasitology based on data obtained on the most studied models to control GINs in small ruminants, the tannin-containing legumes (Fabaceae); (ii) to illustrate how the 'nutraceutical concept' could be expanded to other plants, other livestock production systems and other GI parasitic diseases, and (iii) to explain how this concept is opening up new research fields for better understanding the interactions between the host, the digestive parasites and the environment.

Anthelmintic effect of carob pods and sainfoin hay when fed to lambs after experimental trickle infections with Haemonchus contortus and Trichostrongylus colubriformis

The aim of the study was to compare the in vivo anthelmintic activity of sainfoin hay (Onobrychis viciifolia) and carob pod meal (Ceratonia siliqua) against gastrointestinal nematodes. Seven days before infection, 64 naive lambs were assigned to four different groups: Group S received sainfoin hay and group CAR was fed with carob pods. The remaining lambs received lucerne hay (Medicago sativa) and were assigned to positive (non-treated, NT) and negative (treated, T) control groups (treatment with albendazole). On day 0, lambs were artificially trickle infected for 6 weeks, with a mixture of infective larvae of Haemonchus contortus and Trichostrongylus colubriformis. Parasitological and pathophysiological parameters were measured repeatedly during the 2-month study. Compared to the NT group, decreases in egg excretion were observed in the CAR and S groups with significant differences only found for sainfoin (p < 0.05). At necropsy, group S showed decreases in the total worm numbers of both nematode species with significant differences for H. contortus. In contrast, no differences were noticed for the CAR group. Compared to the NT group, lower values for fecundity of female H. contortus were found in the S and CAR groups, however differences were non-significant. No differences in body weight gains were found between groups. Consistent results were found showing significantly higher packed cell volume (PCV) values in the T and S groups compared to NT and CAR groups. Overall, these results confirm a positive effect associated with the feeding of lambs with tanniniferous resources on host resilience (PCV values) and against gastrointestinal parasitic nematodes by affecting some biological traits of worm populations (e.g. eggs per gram of faeces and worm numbers). However, the anthelmintic effects differed between the two tannin-containing resources, which might be associated with the quantity and/or quality of secondary metabolites (condensed tannins and/or other polyphenols).

Ruminant self-medication against gastrointestinal nematodes: evidence, mechanism, and origins

Gastrointestinal helminths challenge ruminants in ways that reduce their fitness. In turn, ruminants have evolved physiological and behavioral adaptations that counteract this challenge. Ruminants display anorexia and avoidance behaviors, which tend to reduce the incidence of parasitism. In addition, ruminants appear to learn to self-medicate against gastrointestinal parasites by increasing consumption of plant secondary compounds with antiparasitic actions. This selective feeding improves health and fitness. Here, we review the evidence for self-medication in ruminants, propose a hypothesis to explain self-medicative behaviors (based on post-ingestive consequences), and discuss mechanisms (e.g., enhanced neophilia, social transmission) that may underlie the ontogeny and spread of self-medicative behaviors in social groups. A better understanding of the mechanisms that underlie and trigger self-medication in parasitized animals will help scientists devise innovative and more sustainable management strategies for improving ruminant health and well-being.

Reduced neophobia: a potential mechanism explaining the emergence of self-medicative behavior in sheep

Gastrointestinal helminths challenge ruminants in ways that reduce their fitness. In turn, ruminants have evolved physiological and behavioral adaptations that counteract this challenge. For instance, emerging behavioral evidence suggests that ruminants self-select medicinal compounds and foods that reduce parasitic burdens. However, the mechanism/s leading to self-medicative behaviors in sick animals is still unknown. We hypothesized that when homeostasis is disturbed by a parasitic infection, consumers should respond by increasing the acceptability of novel foods relative to healthy individuals. Three groups of lambs (N=10) were dosed with 0 (Control-C), 5000 (Medium-M) and 15000 (High-H) L3 stage larvae of Haemonchus contortus. When parasites had reached the adult stage, all animals were offered novel foods and flavors in pens and then novel forages at pasture. Ingestive responses by parasitized lambs were different from non-parasitized Control animals and they varied with the type of food and flavor on offer. Parasitized lambs consumed initially more novel beet pulp and less novel beet pulp mixed with tannins than Control lambs, but the pattern reversed after 9d of exposure to these foods. Parasitized lambs ingested more novel umami-flavored food and less novel bitter-flavored food than Control lambs. When offered choices of novel unflavored and bitter-flavored foods or different forage species to graze, parasitized lambs selected a more diverse array of foods than Control lambs. Reductions in food neophobia or selection of a more diverse diet may enhance the likelihood of sick herbivores encountering novel medicinal plants and nutritious forages that contribute to restore health.

Gastrointestinal nematodes of dairy goats, anthelmintic resistance and practices of parasite control in Northern Italy

BACKGROUND

Gastrointestinal nematodes (GINs) are one of the main constraints to ruminant production worldwide. Anthelmintic resistance (AR) has been reported in goats throughout Europe, yet little is known about the AR status in Italy. The aims of the study were: i) determine the frequency of AR in GINs in goat flocks in Northern Italy, Italy, ii) survey goat farmers on the current practices of parasite control, iii) update the species composition of the gastrointestinal helminthofauna. Thirty three flocks were enrolled and 1288 individual fecal samples were collected. Based on the egg per gram (EPG), 15 flocks were selected to evaluate the presence of AR in GINs with the Fecal Egg Count Reduction Test (FECRT). A questionnaire surveyed 110 dairy goat farmers to acquire information about farm management and drenching practices against GINs. Further, the gastrointestinal tracts of 42 goats were analyzed.

RESULTS

The FECRs indicated that five of the 15 flocks had problems of AR, which was identified in all two of the anthelmintic classes tested. Resistance and suspected resistance was found in 40% of the flocks selected for AR testing that were treated with benzimidazoles while 20% of the flocks treated with eprinomectin had resistant GINs. Teladorsagia/Trichostrongylus L3 were isolated from the post-treatment coprocultures of all flocks with resistance but not from the flock with suspected oxfendazole resistance. Treatments against helminths were performed once annually in 73.63% of the flocks, but 20.00% of farmers declared not regularly treating their goats every year. Annual treatments usually occurred in autumn or winter at dose rate for sheep. Te. circumcincta, H. contortus, Tr. colubriformis, Skrjabinema caprae and Oesophagostomum venulosum were the most abundant and prevalent species of the gastrointestinal tract.

CONCLUSIONS

Strategies to prevent the development of AR should be widely adopted in Northern Italy. Further, farmers and practitioners should be educated about the importance of using the correct dose rates in goats. In addition, the presence of highly pathogenic GINs coupled with high worm burden in all sector of gastrointestinal tract and the prevalence values further suggest that improved diagnosis and active surveillance of GINs infection is needed.

The influence of stocking rate and mixed grazing of Angora goats and Merino sheep on animal and pasture production in southern Australia. 4. Gastrointestinal parasitism

Gastrointestinal nematodes limit the growth, production and welfare of goats but there are few reliable sources of information for recommending management practices across flocks. The effects of animal species (Angora goat, Merino sheep, mixed-grazed goats and mixed-grazed sheep at the ratio of 1 : 1) and stocking rate (SR: 7.5, 10, 12.5 animals/ha) on gastrointestinal parasitism were determined in a replicated experiment on improved annual temperate pastures in southern Australia, from 1981 to 1984. Detailed monitoring of gastrointestinal nematodes was undertaken on animals before, during (five times per year) and at the conclusion of studies using faecal strongyle egg counts (WEC) and total worm counts. Sheep had a greater proportion of nematodes as Teladorsagia spp. and goats a greater incidence of Trichostrongylus spp. Both goats and sheep developed resistance to Nematodirus spp. during the experiment. WEC was similar in goats and sheep at the start of the experimental period but, thereafter, was consistently greater in goats than in sheep. While WEC was highly related to total worm count, the regressions for sheep and goats were different. Increasing the SR increased the WEC of goats and mixed-grazed goats but not of sheep. During the experiment, WEC declined at 7 and 10 animals/ha but increased at 12.5/ha. Mixed grazing with goats provided beneficial effects for sheep at all stocking rates, but the effects for goats were dependent on the stocking rate, being beneficial at 7.5 and 10/ha but harmful at 12.5/ha. The WEC of separately grazed goats were generally higher than the WEC of mixed grazed goats. The WEC of mixed sheep were lower than those of separately grazed sheep. During the experiment, the WEC of mixed grazed sheep declined faster than the WEC of separately grazed sheep but the WEC of separately grazed goats at 12.5/ha and of mixed grazed goats at 10 and 12.5/ha increased. Under the environmental and pastoral conditions examined, Angora wether goats should not be grazed at SR above those recommended for wether sheep. In the present study, the impact of gastrointestinal-nematode infections in goats was reduced at lower SR. Further, mixed grazing of Angora wether goats with wether sheep at or below the recommended SR resulted in reduced gastrointestinal parasitism for both sheep and goats, compared with monospecific grazing conditions. Goats did not represent a gastrointestinal-nematode hazard to sheep.

Lack of efficacy of monepantel against Teladorsagia circumcincta and Trichostrongylus colubriformis

After reports of the apparent failure of monepantel to reduce the egg counts of goats on a farm in the lower North Island of New Zealand, faecal egg count reduction tests were conducted in goats and lambs resident on the property, and a confirmatory, slaughter study was conducted using 12 sheep, sourced elsewhere, that were grazed on the farm for approximately 5 weeks. In the egg count reduction test in goats, 8 animals were given monepantel at 3.9 mg/kg (just over 1.5× the sheep dose rate of 2.5mg/kg), whilst four received 7.7 mg/kg (just over 3× the sheep dose). In the egg count reduction test in sheep, 15 lambs were treated with 3.0mg/kg of monepantel. For the confirmatory study, the sheep were housed indoors for 2 weeks before half were treated with 2.9 mg/kg monepantel and the animals were killed for worm counts 9 days later. There was no evidence of efficacy in either egg count reduction test, or in the goats, the two dose rates used appeared equally ineffective. Likewise, there were no significant reductions in egg counts or worm burdens in the slaughter study. Monepantel was ineffective against at least two gastrointestinal nematode species, Teladorsagia circumcincta and Trichostrongylus colubriformis. These findings represent the first report from the field of resistance having developed to the anthelmintic monepantel with severe resistance developing in more than one species after being administered on 17 separate occasions to different stock classes and in less than 2 years of the product first being used on the farm in question.