Parasitism and production in farm animals

The Economic Impact of Parasitism from Nematodes, Trematodes and Ticks on Beef Cattle Production

Global human population growth requires the consumption of more meat such as beef to meet human needs for protein intake. Cattle parasites are a constant and serious threat to the development of the beef cattle industry. Studies have shown that parasites not only reduce the performance of beef cattle, but also negatively affect the profitability of beef agriculture and have many other impacts, including contributing to the production of greenhouse gases. In addition, some zoonotic parasitic diseases may also threaten human health. Therefore, ongoing cattle parasite research is crucial for continual parasite control and the development of the beef cattle industry. Parasitism challenges profitable beef production by reducing feed efficiency, immune function, reproductive efficiency, liveweight, milk yield, calf yield and carcass weight, and leads to liver condemnations and disease transmission. Globally, beef cattle producers incur billions (US$) in losses due to parasitism annually, with gastrointestinal nematodes (GIN) and cattle ticks causing the greatest economic impact. The enormity of losses justifies parasitic control measures to protect profits and improve animal welfare. Geographical differences in production environment, management practices, climate, cattle age and genotype, parasite epidemiology and susceptibility to chemotherapies necessitate control methods customized for each farm. Appropriate use of anthelmintics, endectocides and acaricides have widely been shown to result in net positive return on investment. Implementing strategic parasite control measures, with thorough knowledge of parasite risk, prevalence, parasiticide resistance profiles and prices can result in positive economic returns for beef cattle farmers in all sectors.

Understanding Animal-Plant-Parasite Interactions to Improve the Management of Gastrointestinal Nematodes in Grazing Ruminants

Grazing systems have great potential to promote animal welfare by allowing animals to express natural behaviours, but they also present risks to the animals. Diseases caused by gastrointestinal nematodes are some of the most important causes of poor ruminant health and welfare in grazing systems and cause important economic losses. Reduced growth, health, reproduction and fitness, and negative affective states that indicate suffering are some of the negative effects on welfare in animals infected by gastrointestinal nematode parasitism. Conventional forms of control are based on anthelmintics, but their growing inefficiency due to resistance to many drugs, their potential for contamination of soil and products, and negative public opinion indicate an urgency to seek alternatives. We can learn to deal with these challenges by observing biological aspects of the parasite and the host’s behaviour to develop managements that have a multidimensional view that vary in time and space. Improving animal welfare in the context of the parasitic challenge in grazing systems should be seen as a priority to ensure the sustainability of livestock production. Among the measures to control gastrointestinal nematodes and increase animal welfare in grazing systems are the management and decontamination of pastures, offering multispecies pastures, and grazing strategies such as co-grazing with other species that have different grazing behaviours, rotational grazing with short grazing periods, and improved nutrition. Genetic selection to improve herd or flock parasite resistance to gastrointestinal nematode infection may also be incorporated into a holistic control plan, aiming at a substantial reduction in the use of anthelmintics and endectocides to make grazing systems more sustainable.

Sublethal effects of parasitism on ruminants can have cascading consequences for ecosystems

Parasitic infections are common, but how they shape ecosystem-level processes is understudied. Using a mathematical model and meta-analysis, we explored the potential for helminth parasites to trigger trophic cascades through lethal and sublethal effects imposed on herbivorous ruminant hosts after infection. First, using the model, we linked negative effects of parasitic infection on host survival, fecundity, and feeding rate to host and producer biomass. Our model, parameterized with data from a well-documented producer–caribou–helminth system, reveals that even moderate impacts of parasites on host survival, fecundity, or feeding rate can have cascading effects on ruminant host and producer biomass. Second, using meta-analysis, we investigated the links between helminth infections and traits of free-living ruminant hosts in nature. We found that helminth infections tend to exert negative but sublethal effects on ruminant hosts. Specifically, infection significantly reduces host feeding rates, body mass, and body condition but has weak and highly variable effects on survival and fecundity. Together, these findings suggest that while helminth parasites can trigger trophic cascades through multiple mechanisms, overlooked sublethal effects on nonreproductive traits likely dominate their impacts on ecosystems. In particular, by reducing ruminant herbivory, pervasive helminth infections may contribute to a greener world.

Prevalence of gastrointestinal parasitic infection in cows and buffaloes in Lower Dir, Khyber Pakhtunkhwa, Pakistan

Gastrointestinal (GI) Parasitic infection is a hot issue for cattle management. There is variation of GI parasites effects in sex, age of cattle, drinking water condition, nutrition, and severity of infection. Studies on prevalence of GI parasites among cattle population in Dir Lower are lacking. A total of 40 farms were selected randomly in six tehsil namely Tehsil Adenzai, Tehsil Timergara, Tehsil Balambat, Tehsil Munda ,Tehsil Lalqala, Tehsil Khall. Freshly cattle fecal samples were collected randomly from the selected farms during March 2018 till December 2018. Out of 314 buffaloes and cattle examined 58.59% (184/314) were positive for eggs, cyst/oocyst of one or more species of GI Parasites. The prevalence of parasitic infection was higher in Buffaloes 63.55% (75/118) as compared to Cow 55.61% (109/196) but the difference was not significant (p>0.05) Entamoeba,spp, Moniezia spp, Haemonchus spp and Coccidian spp were found in this study. The non-treated animals indicated the highest percentage of infection in cow 57.71% (101/175) and buffalo 68.13% (62/91).GI parasite prevalence in female animal were higher female cow 62.58% (87/139) and female buffalo 77.33% (58/75) as compared to male. But the difference is non-significant (p> 0.05) Yearling calves had the lower rate of GI parasitic infection than adults. Future investigations are necessary to evaluate the economic loss due to GI parasites in cattle's.

Effectiveness of an experimental injectable prodrug formulation against Fasciola hepatica of different ages in experimentally infected sheep

In this work, we present an evaluation of the fasciolicidal efficacy of a new injectable formulation of fosfatriclaben in comparison with the subcutaneous closantel and oral triclabendazole formulations currently used in veterinary practice as fasciolicides. The study was carried out in vivo on Fasciola hepatica at 2, 4, 6 and 8 weeks of age in experimentally infected sheep. To evaluate the formulation, the percent reduction of the parasite load was measured and the number of fluke eggs. Fosfatriclaben was used at 6 mg/kg/IM (dose equivalent to triclabendazole content), closantel at 5% at 10 mg/kg/SC, and triclabendazole at 10 mg/kg/PO; the control group received no treatment. Fosfatriclaben showed fasciolicidal efficacies of 95.5 %, 100 %, 100 % and 100 %, and triclabendazole showed similar efficacies of 97.4 %, 100 %, 100 % and 100 %, at the different treatment weeks (P > 0.05). Closantel showed limited efficacy against 2-, 4- and 6-week-old flukes but 100 % efficacy in adult flukes. All three evaluated formulations eliminated all 8-week-old F. hepatica trematode eggs. Although fosfatriclaben and triclabendazole showed similar fasciolicidal efficacy, the intramuscular administration of fosfatriclaben has several advantages over the oral administration of triclabendazole, such as ease of administration for veterinary use and a reduced risk of accidents for both the operator and the animals. In addition, the dose used in this injectable formulation is only 60 % of the oral dose, which reduces environmental contamination.

Synthesis, bioevaluation and docking studies of some 2-phenyl-1H-benzimidazole derivatives as anthelminthic agents against the nematode Teladorsagia circumcincta

Gastrointestinal nematode infections are the main diseases in herds of small ruminants. Resistance to the main established drugs has become a worldwide problem. The purpose of this study is to obtain and evaluate the in vitro ovicidal and larvicidal activity of some 2-phenylbenzimidazole derivatives on susceptible and resistant strains of Teladorsagia circumcincta. Compounds were prepared by known procedures from substituted o-phenylenediamines and arylaldehydes or intermediate sodium 1-hydroxyphenylmethanesulfonate derivatives. Egg Hatch Test (EHT), Larval Mortality Test (LMT) and Larval Migration Inhibition Test (LMIT) were used in the initial screening of compounds at 50 μM concentration, and EC₅₀ values were determined for the most potent compounds. Cytotoxicity evaluation of compounds was conducted on human Caco-2 and HepG2 cell lines to calculate their Selectivity Indexes (SI). At 50 μM concentration, nine out of twenty-four compounds displayed more than 98% ovicidal activity on a susceptible strain, and four of them showed more than 86% on one resistant strain. The most potent ovicidal benzimidazole (BZ) 3 showed EC₅₀ = 6.30 μM, for the susceptible strain, while BZ 2 showed the lowest EC₅₀ value of 14.5 μM for the resistant strain. Docking studies of most potent compounds in a modelled Teladorsagia tubulin indicated an inverted orientation for BZ 1 in the colchicine binding site, probably due to its fair interaction with glutamic acid at codon 198, which could justify its inactivity against the resistant strain of T. circumcincta.

A survey of gastrointestinal nematode species in red deer (Cervus elaphus) farms in New Zealand using PCR

Gastrointestinal nematodes are recognised as an animal health issue for farmed red deer. The aim of this study was to explore the range of species infecting farmed deer herds and their farm-level prevalence in New Zealand. Faecal samples were collected from 12-24-month-old deer (n = 6-26; mean 19) on 59 farms located in the North (n = 25) and South (n = 34) Islands. Sub-samples of faeces were pooled by farm and cultured to recover third stage larvae. Twenty four larvae were randomly selected and identified to species using a multiplex PCR (total = 1217 larvae). At farm-level the most prevalent nematodes were Oesophagostomum venulosum 83% (n = 49) and the deer-specific nematodes in the subfamily Ostertagiinae (=Ostertagia-type) including, Spiculoptera asymmetrica 73% (n = 43), Ostertagia leptospicularis 47% (n = 28), Spiculoptera spiculoptera 47% (n = 28). The recently identified Trichostrongylus askivali was present on 32% (n = 19) of the farms and Oesophagostomum sikae on 17% (n = 10). In the analysis of the total number of larvae identified, the proportion was in similar order, 45% (n = 548) were O. venulosum, 14% (n = 173) S. asymmetrica, 10% (n = 124) S. spiculoptera, 9% (n = 114) O. leptospicularis, T. askivali, 3% (n = 40) and only 2% were O. sikae (n = 20). This study is the first to show the farm-level prevalence of nematode species in deer in New Zealand and the first to use PCR as a diagnostic tool. It provides data consistent with cross-infection from sheep/cattle to deer, and provided tentative insights into the proportions of the main GIN species across the deer population including O. sikae and T. askivali which have only recently been identified in New Zealand.

Immune response in goats vaccinated with thiol-binding proteins from Haemonchus contortus

The experimental protocol of immunization tested here confirms its protective effect against Haemonchus contortus in goats. This protection translated into a 65.5% mean reduction in adult worm burden after a homologous challenge, and a significant decrease (73.2%) in cumulative faecal egg counts (FECs). These parasitological findings were consistent with the levels of some biopathological parameters. Thus, the reduction in adult worms and FEC observed in immunized animals were associated with increased levels of packed cell volume as well as plasma proteins. This response seems to be related to an important increase in specific antibodies (in serum and gastric mucus) and eosinophilia in response to challenge. At the local level, a cellular response was also observed in which CD4⁺ lymphocytes and globule leucocytes played a predominant role. Finally, it should be noted that the study of immunolocalization of proteins used in the vaccination trial suggests that these antigens have an internal location (at intestinal and reproductive tissues) in the adult worm. This observation, in conjunction with the kinetics of specific antibody levels after the challenge, suggests that these antigens may be part of excretory/secretory (E/S) products.

Gross, histopathology and molecular diagnosis of oesophagostomosis in sheep

A total of 120 tissue samples (Rumen, reticulum, omasum, abomasum, small intestine and large intestine) were collected from slaughter houses in Chennai, Kanchipuram and Tiruvallur districts and five samples from necropsy room at Department of Veterinary Pathology, Madras Veterinary College, Chennai, Tamil Nadu. Overall prevalence of GI parasites was 52.00%. Among the positive samples, single infection was found to be more (53.84%) than themixed infection (46.15%). Out of which, oesophagostomosis was 17.00% and found as single infection. In oesophagostomosis, significant gross lesions observed in the small and large intestine were multiple small to large, round to irregular, hard, fibrotic, raised nodules. The wall of the large intestine was greatly thickened and oedematous and the nodules were seen projecting into the lumen and mucosal surface was intact. On histopathological examination, ileum of sheep showed parasitic nodules with central baso-eosinophilic necrotic area, larval stages in the necrotic area, surrounded by layers of inflammatory cells and finally encapsulated in a thick fibrous connective tissue capsule. Immunohistochemistry (IHC) with Vimentin showed intense cytoplasmic positive signals DAB Brown. PCR was carried out targeting ITS2 regions of the O. columbianum and O. venulosum. DNA isolated from both the faecal eggs and adult worms showed good amplification.

Molecular expression and characterization of GCP7 gene of Haemonchus contortus

Haemonchus contortus is a highly pathogenic and most economically important parasite of sheep and goats worldwide. The cysteine proteases from H. contortus are prime targets for vaccine development. In the present communication we report the molecular expression and characterization of cathepsin B-like cysteine protease, GCP7 gene of H. contortus to study its efficiency as target protein for immunoprophylaxis against haemonchosis in sheep and goats. The complete ORF of GCP7 gene, devoid of the signal sequence, was amplified by RT-PCR from mRNA isolated from H. contortus and was cloned initially into pTZ57R/T cloning vector and then sub-cloned in the pET32a(+) expression vector to produce GCP7 antigen. The nucleotide and deduced amino acid sequence of the GCP7 was aligned against the related sequences of H. contortus available in public domain for in silico analysis by DNA STAR and MEGA version 4.0 softwares. The nucleotide sequence revealed that the GCP7 gene of H.contortus (Indian isolate) encodes 324 amino acids (devoid of signal sequence) and its nucleotide sequence had 95.9% to 99.4% sequence homology with that of U.S.A. and previously published Indian isolates. A high level expression of recombinant (r) GCP7 protein was observed in the molecular range (Mr) of 55 kDa. The rGCP7 protein was confirmed by its specific immunoreactivity against known reference positive sheep sera.

Estimation of the impact of Fasciola hepatica infection on time taken for UK beef cattle to reach slaughter weight

Fasciolosis is common in UK beef cattle, but it is unclear at what levels liver fluke burdens cause production losses. This study aimed to address these uncertainties by estimating the impact of liver fluke infection on UK beef cattle productivity and investigating the use of diagnostic tests in a quantitative manner. We built three linear regression models for slaughter age by weight and different measures of liver fluke status, while accounting for sex, breed, season, year and farm of origin. Data were sourced from Scotland’s largest red meat abattoir throughout 2013 and 2014. Our Meat Hygiene Service model estimated that cattle classified as having liver fluke damage had on average 10 days greater slaughter age than animals with no evidence of fasciolosis. Our liver fibrosis model estimated that the increase in slaughter age was more severe for higher fibrosis scores. Similarly, our burden model showed an increase in slaughter age for animals with as few as 1 to 10 parasites found in their livers. Lastly, we used receiver operating characteristic curves to show that serum antibody ELISA, copro-antigen ELISA and faecal egg counting can be useful in distinguishing between animals with and without production limiting levels of fasciolosis.

Social Behaviours and Networks of Vervet Monkeys Are Influenced by Gastrointestinal Parasites

Substantial research has shown that while some parasite infections can be fatal to hosts, most infections are sub-clinical and non-lethal. Such sub-clinical infections can nonetheless have negative consequences for the long-term fitness of the host such as reducing juvenile growth and the host's ability to compete for food and mates. With such effects, infected individuals are expected to exhibit behavioural changes. Here we use a parasite removal experiment to quantify how gastrointestinal parasite infections affect the behaviour of vervet monkeys (Chlorocebus aethiops) at Lake Nabugabo, Uganda. Behavioural profiles and the structure of nearest neighbour relationships varied significantly. As predicted, after deworming the duration of the resting events decreased, which is consistent with the idea that parasite infections are energetically costly. In contrast to what was predicted, we could not reject the null hypothesis and we observed no change in either the frequency or duration of grooming, but we found that the duration of travel events increased. A network analysis revealed that after deworming, individuals tended to have more nearest neighbours and hence probably more frequent interactions, with this effect being particularly marked for juveniles. The heightened response by juveniles may indicate that they are avoiding infected individuals more than other age classes because it is too costly to move energy away from growth. We consider that populations with high parasite burden may have difficulties developing social networks and behaviours that could have cascading effects that impact the population in general.

Effect of anthelmintic treatment strategy on strongylid nematode species composition in grazing lambs in Scotland

Background

Refugia based anthelmintic protocols aim to reduce the rate of development of anthelmintic resistance in gastrointestinal nematodes (GIN). Previous studies have illustrated the impact of different drenching regimes on drug efficacy and animal growth; however, the impact on nematode populations has yet to be characterised within natural infections. This study investigated the changes in species composition of GIN throughout the grazing season, following implementation of four different ivermectin drenching regimes over six years: neo-suppressive monthly treatment (NST), targeted selective treatment (TST), strategic prophylactic treatment (SPT) and treatment upon observation of clinical signs (MT).

Methods

Lambs were grazed on one of eight replicate paddocks each grazing season following treatment regimes assigned in year 1. Faecal samples were collected fortnightly from all animals and hatched to first stage larvae (L₁). DNA was extracted from individual L₁ and a multiplex PCR assay targeting the internal transcribed spacer 2 (ITS2) region of Teladorsagia circumcincta, Trichostrongylus spp. and Haemonchus contortus conducted. Other species were identified using species-specific PCR. Worm-naïve tracer lambs were grazed on the paddocks at the start and end of each grazing season and adult worms recovered at post mortem to investigate the parasite population on pasture.

Results

Results showed an overall decrease in species diversity in egg output from the NST group which occurred within a single grazing season and was consistent throughout the experiment. Species diversity was protected over six years in groups implementing TST, SPT and MT treatment regimes, designed to offer refugia. The expected shift in species prevalence throughout the season from Teladorsagia to Trichostrongylus was observed in all but the NST group where only Teladorsagia spp. were recovered from trial lambs by the end of the experiment. Worm burdens indicated the presence of several species at relatively low abundance on pasture in the NST group in 2011. However, these species were not represented in egg output from trial lambs, probably due to the frequent anthelmintic treatment administered throughout the grazing season.

Conclusion

The molecular methods utilised here worked well. The comparable results of the three refugia-based treatment regimes suggest that nematode diversity can be maintained using part or whole group treatments if a rich supra-population of parasites are available to re-infect animals post treatment.

Relative maturity and the development of immunity to gastrointestinal nematodes in sheep: an overlooked paradigm?

Sheep display considerable variation in both the timing and magnitude of development of immunity to gastrointestinal nematodes (GIN). Onset of immunity is dependent on a number of factors, including antigenic stimulus, nutrition supply, age and size of the animals, the latter of which are confounded. Here, we review the factors associated with the development of immunity to GIN in sheep, particularly in the context of the role that relative maturity may have through applying the rules of genetic size scaling based on examples from published literature. Comparing animals based on their metabolic age, rather than chronological age, may provide an explanation for the timing of immune development and may reduce the variation in immune development that frequently is observed both between and within breeds. Further, this approach may help explain the phenotypic differences in animal performance between animals of varying immunological capacity to GIN through influences on mature body weight. As such, when considering factors influencing immune development to GIN, physiological age or relative maturity may be considered an overlooked paradigm. We propose it may be worthwhile to consider metabolic age when comparing the immune competence of animals to ensure the subjects are at an analogous stage of physiological development.

Chemical Structures of Plant Hydrolyzable Tannins Reveal Their in Vitro Activity against Egg Hatching and Motility of Haemonchus contortus Nematodes

The use of synthetic drugs against gastrointestinal nematodes of ruminants has led to a situation where resistance to anthelmintics is widespread, and there is an urgent need for alternative solutions for parasite control. One promising approach is to use polyphenol-rich bioactive plants in animal feeds as natural anthelmintics. In the present work, the in vitro activity of a series of 33 hydrolyzable tannins (HTs) and their hydrolysis product, gallic acid, against egg hatching and motility of L1 and L2 stage Haemonchus contortus larvae was studied. The effect of the selected compounds on egg and larval structure was further studied by scanning electron microscopy. The results indicated clear relationships between HT structure and anthelmintic activity. While HT size, overall flexibility, the types and numbers of functional groups, together with the linkage types between monomeric HTs affected the activity differently, the optimal structure was found with pentagalloylglucose.

Prevalence of intestinal and haemoprotozoan parasites of small ruminants in Tamil Nadu, India

Aim:

The aim of the present study is to assess the prevalence of intestinal and haemoprotozoan parasites of small ruminants (Sheep and Goats) in North Western part of Tamil Nadu, India.

Materials and Methods:

A total of 630 faecal samples (251-sheep, 379-goats) and 554 blood smears (242-sheep, 312-goats) were examined, for the presence of eggs of intestinal and haemoprotozoan parasites, respectively. The samples were received from the Veterinary college hospital and Veterinary dispensaries in North Western part of Tamil Nadu. Faecal samples were processed by sedimentation technique and examined under low power objective (×10), and blood smears were stained using Giemsa’s technique and examined under oil immersion (×100).

Result:

The analysis of data on the prevalence of intestinal and haemoprotozoan parasites of sheep and goats in North Western part of Tamil Nadu for the period from 2004 to 2013, showed an overall prevalence of intestinal parasites was found to be 67% and 35% in sheep and goats, respectively, whereas only 11% of sheep and 3% of goats had the haemoprotozoan parasitic infection. Highly, significant difference (p<0.01) in the prevalence of intestinal (χ²=65), and hemoprotozoan (χ²=15.4) parasitism was observed between sheep and goats. Intestinal parasites such as strongyles, Trichuris, Moniezia, amphistome, and coccidia were identified in which the highest prevalence was observed with coccidia, followed by strongyles, Monezia, Trichuris, and least with amphistome in both the sheep and goats. The haemoprotozoan parasites recorded were Theileria and Anaplasma species, of which, Anaplasma spp. being the highest and Theileria spp. the least prevalent in both the sheep and goats. The seasonal prevalence of intestinal parasites showed highest in rainy season, followed by moderate in winter and least with summer in both the sheep and goats, whereas the haemoprotozoan parasites recorded were the highest in summer followed by winter and least with rainy season.

Conclusion:

The present study suggests that North Western part of Tamil Nadu is highly endemic for intestinal parasites such as coccidia and strongyles and haemoprotozoans such as Anaplasma and Theileria species in small ruminants.

In vitro ovicidal assessment of methanol, ethyl acetate and chloroform extracts of Annona squamosa and Chenopodium album against caprine gastrointestinal nematodiosis

The objective of this study was in vitro evaluation of the ovicidal efficacy of methanol, ethyl acetate and chloroform extracts of Annona squamosa (seeds) and Chenopodium album (whole plant) in comparison to albendazole against the GI nematodes of goats using egg hatch test. Eggs of GI nematodes were incubated at 27 °C in different extracts at concentration of 100-6.25 mg/ml for 2 days. Distilled water and albendazole were used as negative and positive controls, respectively. Percentage efficacy and ED50 and ED90 values were separately evaluated with upper and lower confidence limit by log probit analysis using SAS 9.2. The ED50 and ED90 values of methanolic, ethyl acetate and chloroform extracts of A. squamosa was calculated as 1.52 and 4.56; 2.48 and 10.73; 3.02 and 12.44 mg/ml, respectively against GI nematodes if goats. Similarly, the ED50 and ED90 values of methanolic, ethyl acetate and chloroform extracts of C. album was calculated as 3.86 and 7.14; 2.73 and 8.31; 4.41 and 20.11 mg/ml, respectively This study shows that C. album and A. squamosa possess in vitro anthelmintic activities. The study also suggests further large scale pharmacological and toxicological studies for their safer use in veterinary medicine.

Contrasting views of animal healthcare providers on worm control practices for sheep and goats in an arid environment

A questionnaire survey was conducted to determine the worm control practices and anthelmintic usage of 150 key respondents involved in sheep and goat production in the arid Thal area of Pakistan. The information was collected by visiting farms, and interviewing the key respondents which included veterinary officers (n = 15), veterinary assistants (n = 51), traditional practitioners (n = 24), and small and large scale sheep/goat farm herders and owners (n = 60). Among all interviewed animal healthcare providers, the veterinary officers had the highest level of awareness of parasitic infection and advocated the use of modern available anthelmintics according to the predefined schedule. The farmers on the other hand, had the lowest level of knowledge about parasitic infections. They used modern anthelmintics at low frequencies (every six months) following an unusual practice of diluting the medicine. Veterinary assistants had a medium level of awareness about the parasitic infections using anthelmintic treatments when they deemed necessary rather than following a predefined treatment schedule. Traditional practitioners were also aware of parasitic infections and used traditional anthelmintics or a combination of the traditional and modern anthelmintics. The animal health providers had a different awareness and knowledge of parasitic infections which resulted in contrasting proposals for its' control. The farmers used worm control measures in accordance with their own views and those of animal healthcare advisors, combining modern and traditional treatments. This study provides the first insight into the differing views of those animal healthcare providers who form the basis for effective parasitic control within the sheep and goat industry of an arid region.

Immunoprotective effect of cysteine proteinase fractions from two Haemonchus contortus strains adapted to sheep and goats

A preliminary analysis of the significance of genetic diversity in cysteine proteinase genes has been performed simultaneously in sheep and goats, with regard to the immunological control using these enzymes against haemonchosis. For this purpose, we have studied the cross-immunoprotective effect of cysteine protease-enriched protein fractions (CPFs) in adult worms of two Haemonchus contortus strains from North America and Spain that are adapted to sheep and goats, respectively. Previous genetic analysis of cysteine proteinase genes in both strains has shown that some of loci are polymorphic and these differences are translated into changes in the amino acid sequences. However, our results show that CPFs from H. contortus adult worms have a protective effect against the parasite in both sheep and goats. These results are similar regardless of whether they were obtained from sheep or goat-adapted H. contortus strains, which could be very important in case H. contortus CPFs were commercially used in different countries, as vaccines to prevent the negative effects of this parasite. Interestingly, this experimental inoculation of both species with a heterologous strain of H. contortus contributes to the idea shown in previous studies about how difficult is the interpretation and the comparison of vaccination where strains not adapted to a specific host are used. Therefore, the challenger of using heterologous strains could provide similar results to those observed in immunised animals. This study suggests the possibility of exploring the mechanisms involved in natural protection against non-adapted strains, in order to develop strategies to control haemonchosis.

Direct and indirect effects of bioactive tannin-rich tropical and temperate legumes against nematode infections

Parasitic infections with gastrointestinal nematodes (GINs) represent a major pathological threat associated with the outdoor production of various livestock species. Up to now, the control of these parasitic diseases essentially relied on the use of commercial anthelmintic drugs. However, resistance to anthelmintics is nowadays widespread in worm populations. Recent results indicate that bioactive tanniniferous plants represent a valuable option as an alternative to commercial drugs for the control of GINs. The pertinent use of tannin-containing fodders as nutraceuticals supposes a clear understanding of the mode of action against the worms. The objectives of this paper are: (1) to discuss the nature and quantity of the active molecules involved in the anthelmintic activity; and (2) to review and analyze the changes provoked to the various parasitic stages. The possible involvement of some main polyphenols to explain the bioactivity of some tannin-rich plants will be discussed as well as the possible effects on the various nematode stages, relying on data obtained either with the temperate forage, sainfoin (Onobrychis viciifoliae) or with the tropical legume tree (Lysiloma latisiliquum). The information on the mode of action will be related to the potential consequences for better field applications under entirely different environmental and ecological conditions of productions.

Small ruminant resistance against gastrointestinal nematodes: a case of Haemonchus contortus

Gastrointestinal nematode (GIN) infections are a common constraint to small ruminant industry throughout the world, and among those, haemonchosis has its own significance. Control of GIN primarily relies on the use of anthelmintics, but this approach has become less reliable due to the development of resistance in GINs against commonly used anthelmintics and an increased consumer demand for environmentally friendly animal products. These issues have stimulated investigations to find alternative sustainable control strategies, which are less reliant on anthelmintic input. One of such strategies is breeding of small ruminants for their resistance to the GINs. The susceptibility and resistance of animals to GIN infections varies within and between breeds. Various parasitological, biochemical and immunological parameters are employed to evaluate natural resistance status of animals both in natural pasture and artificial infections. The immune mechanisms responsible for resistance are not completely understood, but it has a significant effect in inherited resistance. Relatively resistant or tolerant animals show better local and generalised immune response as compared to susceptible. Immune response against GINs is influenced by many physiological factors. Determination of specific genes linked with host resistance will provide a valuable approach to find out the molecular mechanism of host resistance to GINs. Resistance has been reported to reduce pasture contamination, which in turn reduces re-infection and thus the requirement of the frequent anthelmintic treatments. The efficiency of control can be increased through objective and accurate identification of genetically tolerant individuals by natural and artificial infections with GINs. Complete resistance is the ultimate solution, but this has generally been ignored as a commercial reality. This paper reviews the published reports on natural resistance in small ruminants and discusses the prospects of developing small ruminants, which could be resistant to GINs.

Potentilla fulgens (Family Rosaceae), a medicinal plant of north-east India: a natural anthelmintic?

The cestode parasite, Raillietina echinobothrida and the trematode, Gastrothylax crumenifer were exposed to the ethanolic root peel extract of Potentilla fulgens, an antiparasitic local medicinal plant of Meghalaya, India, to evaluate the anthelmintic efficacy of the plant. The parasites were incubated in 1, 5, 10, 20, 50 and 100 mg crude alcoholic extract per ml of phosphate buffered saline (PBS) at a temperature of 37 ± 1°C. Paralysis and death were observed at 2.00 ± 0.05 and 2.80 ± 0.06 h for the cestode and 1.21 ± 0.06 and 2.18 ± 0.04 h for the trematode parasites at the highest test concentration of the plant extract. The commercial anthelmintic, Praziquantel (PZQ) showed higher activity at the tested concentration (0.02 mg/ml). To further investigate the efficacy of the plant extract, vital tegumental enzymes of the parasite viz. Acid phosphatase (AcPase), Alkaline phosphatase (AlkPase) and Adenosine triphosphatase (ATPase) were studied. Quantitatively, the total enzyme activity of AcPase, AlkPase and ATPase was found to be reduced significantly by 69.20, 66.43 and 29.63% for R. echinobothrida and 47.96, 51.79 and 42.63% for G. crumenifer, respectively compared to the respective controls; histochemical study also showed reduction in the visible staining of the enzymes. The reference drug, PZQ also showed more or less similar effect like that of the plant extract. The result suggests that phytochemicals of P. fulgens have anthelmintic potential.

Anthelmintic activity of some Mediterranean browse plants against parasitic nematodes

The anthelmintic properties of tannin-rich plants are being explored as an alternative to chemical drugs. Most data have been acquired on legume forages, but only few on browse plants. The present study aimed to (i) screen the in vitro effects of extracts from 7 Mediterranean plants on Haemonchus contortus, (ii) verify the role of tannins using an inhibitor, polyvinyl polypyrrolidone (PVPP) and (iii) verify the in vivo effects of extracts from 4 plants. Significant inhibition was shown in vitro using a larval migration inhibition (LMI) assay for all extracts except that from Olea europaea var. koroneiki. After adding PVPP, the LMI values were restored to control levels for all plants except Pistacia lentiscus and Ceratonia siliqua, confirming a role for tannins in the activity. In the in vivo experiment, 48 lambs composed 6 groups, depending on diet. On Day 0, groups G1–G5 received H. contortus and Trichostrongylus colubriformis larvae and G6 remained uninfected. The various diets were distributed from Days 14 to 45: P. lentiscus (G1), Quercus coccifera (G2), C. siliqua (G3), Onobrychis viciifolia (G4), or Medicago sativa for the 2 control groups (G5, G6). Egg excretion, packed cell volumes (PCVs) and inorganic phosphate were measured weekly throughout the entire experimental period. At slaughter, the worms were enumerated and their fecundity assessed. Consumption of the 4 browser plants did not provoke differences in pathophysiological measurements but there were significant decreases in egg excretion, mainly explained by significant decreases in worm fecundity for both species, without any statistical difference in worm numbers.

Nematode parasites and faecal soiling of sheep in lairage: evidence of widespread potential production losses for the sheep industry

Diarrhoea (scouring) and subsequent faecal soiling of fleece are important economic and welfare issues for the sheep industry. Nematode worm infections are commonly implicated as a cause of scouring. This study aimed to investigate the extent of strongyle parasite infections, and identify any association with faecal worm egg count (WEC) and scouring in sheep from winter rainfall environments in Western Australia consigned to an abattoir. Faeces were collected from sheep with evidence of scouring and normal sheep (firm faecal pellets and no evidence of fresh diarrhoea on breech). A total of 4430 sheep from 113 lines of lambs (<12 months old), 10 lines of yearlings (12–24 months old) and 235 lines of adult sheep (>24 months old) were sampled between September and January. Mean WEC in lamb lines was 1525 eggs per gram (epg) of faeces with mean WEC >1000 epg in 42% of lines and >2000 in 22% of lines. Mean WEC in adult lines was 486 epg, with 13% lines having mean WEC >1000 epg. There was a trend (P = 0.099) to higher WEC in scouring lambs (2289 epg) compared with normal lambs (1523 epg). The scouring adult sheep had lower WEC (417 epg) compared with normal adults (482 epg, P = 0.021). The findings suggest that large strongyle infections were common in lambs consigned for slaughter. The low WEC in scouring adult sheep was consistent with the suggestion that a hypersensitivity to ingested nematode larvae, rather than large worm burdens, may be responsible for scouring in mature sheep.

The effect of long-term feeding of fresh and ensiled cassava (Manihot esculenta) foliage on gastrointestinal nematode infections in goats

The benefit of long-term feeding of fresh or ensiled cassava foliage on gastrointestinal parasite in goats was evaluated. Eighteen male goats (15.15 +/- 2.83 kg and between 4-6 months) were randomly allocated into three treatments supplemented with 200 g of wheat bran head(-1) day(-1). All groups were fed ad-libitum on either grass (CO), fresh cassava (CaF) or ensiled cassava foliage (CaS). At the beginning of the trial, each goat was inoculated with 3000 L3 containing approximately 50% Haemonchus contortus. Individual LWt, FEC and PCV were measured at weekly intervals for 10 weeks. At the termination of the experiment all goats were slaughtered for worm recovery and enumeration. The goats in CaF and CaS had similar weight gains while those in CO lost weight (p < 0.05) through the trial. FEC in CaF and CaS were lower (p < 0.05) than CO during the patency of parasite infections, but there was no difference between CaF and CaS goats. PCV of all groups decreased from above 30% to around 25% at the end of the trial. The compositions of established worm burdens were mainly H. contortus (19-40%) and Trichostrongylus colubriformis (55-76%). TWB did not differ among the groups, however, CaS significantly reduced H. contortus burdens, as compared to CaF and CO (p < or = 0.005). Thus, ensiled cassava foliage reduced the H. contortus population while the fresh foliage only reduced worm fecundity.

The effect of concurrent corticosteroid induced immuno-suppression and infection with the intestinal parasite Trichostrongylus colubriformis on food intake and utilization in both immunologically naïve and competent sheep

The nutritional cost of both the acquisition and maintenance of immunity to gastro-intestinal nematodes was investigated using immunologically naïve 5-month-old lambs and immunologically competent 17-month-old ewes. Within each age cohort, animals were either infected with the equivalent of 80 L3Trichostrongylus colubriformislarvae per kg live weight (LW) per day (IF), similarly infected and concurrently immuno-suppressed with weekly injections of 1·3 mg/kg LW of the glucocorticoid methylprednisolone acetate (ISIF), immuno-suppressed only (IS) or remained as controls (C). Body composition of all animals was estimated using X-ray computer tomography on days -14 and 76 relative to the start of infection. Body weight and faecal nematode egg counts (FEC; eggs per gram of fresh faeces (e.p.g.)) were taken weekly and blood samples for serum proteins and antibodies were obtained every 2 weeks. FEC in IF lambs peaked at 1250 e.p.g. before a typical decline as immunity developed to less than 100 e.p.g. by day 75. FEC of less than 100 e.p.g. in IF ewes indicated immunity was maintained. Successful immuno-suppression in ISIF lambs and ewes was indicated by FEC of 4000 e.p.g. on day 75 and was confirmed by comparative worm burdens and serum antibody titres. The typical reduction in voluntary food intake (VFI) as a consequence of infection was observed in IF lambs (proportionately 0·30,P< 0·001) but not in IF ewes, ISIF lambs or ISIF ewes. Gross efficiency of use of metabolizable energy for net energy deposition was reduced by proportionately 0·20 in lambs during acquisition of immunity and by 0·16 in ewes maintaining an established immunity. Infection in immuno-suppressed animals reduced efficiency by 0·05 and 0·15 for lambs and ewes, respectively. These findings allowed the hypothesis that the reduction in VFI and loss in performance in young parasitised sheep is caused by physiological signalling associated with the acquisition phase of the host immune response to infection, rather than simply the damage caused by the parasiteper se.

Plant secondary metabolites: antiparasitic effects and their role in ruminant production systems

The purported antiparasitic properties of plant secondary metabolites (PSM) have been the cause of controversy amongst the scientific community. Despite long-standing knowledge of the prophylactic and therapeutic properties of PSM-rich extracts, which comes mainly from ethnoveterinary sources, the scientific evidence of the antiparasitic effects of PSM is inconsistent. In the first part of the present paper the causes of this controversy are addressed, and the evidence available on the antiparasitic effects of PSM is critically examined. The focus is on examples of the antiparasitic activity of PSM against helminth nematodes. The conclusion is that PSM can have antiparasitic properties, which depend on their structure, level of ingestion and availability within the gastrointestinal tract of the animal. The second part is an appraisal of the potential role of PSM for parasite control in ruminant production systems. Despite their antiparasitic properties, PSM consumption does not necessarily have positive consequences in parasitised herbivores, as excessive consumption of PSM can adversely affect herbivore fitness and survival, through their anti-nutritional properties. For this reason it is suggested that the antiparasitic properties of PSM should be assessed at the same time as their anti-nutritional effects. The same measure, e.g. the performance of parasitised hosts, should be used when assessing these properties. The assessment of the costs and benefits suggests that parasitised herbivores can benefit from the long-term consumption of PSM only if the antiparasitic benefits outweigh the anti-nutritional costs of PSM. In addition, it is proposed that parasitised animals might be able to benefit from PSM consumption even if their performance is impaired, as long as the latter is a short-term compromise that leads to long-term benefits.

Anthelmintic and nutritional effects of heather supplementation on Cashmere goats grazing perennial ryegrass-white clover pastures1

To investigate anthelmintic and nutritional effects of heather supplementation in goats grazing perennial ryegrass-white clover pastures, 40 dry Cashmere goats were randomly assigned to 4 treatments in a 2 x 2 factorial arrangement: 2 grazing management treatments (supplementation with heather vs. nonsupplementation) and 2 anthelmintic treatments (treatment vs. nontreatment). Goats grazed continuously from May to September 2004. At the end of the grazing period, the number of dead goats due to gastrointestinal parasitism was 1 in the group supplemented with heather and dosed with anthelmintic, 4 in the group that received neither supplementation nor anthelmintic, and 0 in the other 2 groups. For goats that did not receive anthelmintic treatment, the percentage of heather in the diet was negatively correlated with fecal egg count in August (r = -0.59, P < 0.05) and September (r = -0.49, P < 0.1) and positively correlated (r = 0.54, P < 0.05) with BW changes during the grazing season. Therefore, the correlation coefficient between BW change and fecal egg count was negative (r = -0.62, P < 0.05). Rumen ammonia concentrations were always lower in supplemented goats (P < 0.05). However, VFA concentrations were greater in goats consuming heather (58.9 vs. 50.9 mmol/L), which suggests that ruminal fermentation was not adversely affected by consumption of tannins. Heather availability in the vegetation might represent a valuable opportunity and sustainable method to control gastrointestinal nematode infections in a goat production system based on grazing perennial ryegrass-white clover pastures.

Effect of sainfoin (Onobrychis viciifolia) silage and hay on established populations of Haemonchus contortus and Cooperia curticei in lambs

The objective of the study was to examine the effect of dried and ensiled sainfoin (Onobrychis viciifolia) on established populations of Haemonchus contortus (abomasum) and Cooperia curticei (small intestine) in lambs under controlled conditions. Twenty-four parasite naïve lambs were inoculated with a single dose of infective larvae of these parasites 28 days prior to the start of the feeding experiment. Twenty-four days post-infection, 4 days prior to the start of the feeding experiment, animals were allocated to four groups according to egg excretion, live weight and sex. Groups A and B received sainfoin hay and control hay, respectively, for 16 days. Groups C and D were fed on sainfoin silage or control silage for the same period. Feeds were offered ad libitum and on the basis of daily refusals were supplemented with concentrate in order to make them isoproteic and isoenergetic. Individual faecal egg counts on a dry matter basis (FECDM) were performed every 3-4 days and faecal cultures and packed cell volume (PCV) measurements were done weekly. After 16 days of experimental feeding, all animals were slaughtered and adult worm populations were determined. The consumption of conserved sainfoin was associated with a reduction of adult H. contortus (47% in the case of hay, P<0.05; 49% in the case of silage, P=0.075) but had little effect on adult C. curticei. Compared to the controls, H. contortus specific FECDM was reduced by 58% (P<0.01) in the sainfoin hay group and by 48% (P=0.075) in the sainfoin silage group. For both sainfoin feeds FECDM specific to C. curticei were significantly decreased when compared to the control feeds (hay 81% and silage 74%, both tests P<0.001). Our data suggest that different mechanisms were responsible for the reduction in FECDM in response to feeding tanniferous fodder. For H. contortus, the decrease seemed to be due to a nematocidal effect towards adult H. contortus. In contrast for C. curticei, the reduction in FECDM appeared to be a result of a reduced per capita fecundity. For both, hay and silage, an antiparasitic effect could be shown, offering promising perspectives for the use of conserved tanniferous fodder as a complementary control approach against GIN.