Nematode Infections In Sheep Research Articles

Comparison of traditional copromicroscopy with image analysis devices for detection of gastrointestinal nematode infection in sheep

Sustainable parasite control practices are necessary to combat the negative effects of gastrointestinal nematodes on animal health and production while reducing the selection pressure for anthelmintic resistance. Parasite diagnostic tests can inform treatment decisions, the timing and effectiveness of treatment and enable livestock breeding programmes. In recent years new diagnostic methods have been developed, some incorporating machine learning (ML), to facilitate the detection and enumeration of parasite eggs. It is important to understand the technical characteristics and performance of such new methods compared to long standing and commonly utilised methods before they are widely implemented. The aim of the present study was to trial three new diagnostic tools relying on image analysis (FECPAKG2, Micron and OvaCyte) and to compare them to traditional manual devices (McMaster and Mini-FLOTAC). Faecal samples were obtained from 41 lambs naturally infected with gastrointestinal nematodes. Samples were mixed and separated into 2 aliquots for examination by each of the 5 methods: McMaster, Mini-FLOTAC, FECPAKG2, Micron and OvaCyte. The techniques were performed according to their respective standard protocols and results were collected by trained staff (McMaster and Mini-FLOTAC) or by the device (FECPAKG2, Micron and OvaCyte). Regarding strongyle worm egg count, McMaster values varied from 0 to 9,000 eggs per gram (EPG). When comparing replicate aliquots, both the Mini-FLOTAC and Micron methods displayed similar repeatability to McMaster. However, we found FECPAKG2 and OvaCyte significantly less precise than McMaster. When comparing parasite egg enumeration, significant positive linear correlations were established between McMaster and all other methods. No difference was observed in EPG between McMaster and Mini-FLOTAC or FECPAKG2; however, Micron and OvaCyte returned significantly higher and lower EPG, respectively, compared to McMaster. The number of eggs ascribed to other parasite species was not sufficient for performing a robust statistical comparison between all methods. However, it was noted that FECPAKG2 generally did not detect Strongyloides papillosus eggs, despite these being detected by other methods. In addition, Moniezia spp and Trichuris spp eggs were detected by OvaCyte and Mini-FLOTAC, respectively, but not by other methods. The observed variation between traditional and new methods for parasite diagnostics highlights the need for continued training and enhancing of ML models used and the importance of developing clear guidelines for validation of newly developed methods.

The Influence of Flock Variation, Sample Size, Flock Size and Mean Egg Count on the Accuracy and Precision of the Estimated Mean Egg Count

The control of parasitic nematode infection in sheep and other animals is threatened by the evolution of drug resistance in parasite populations. One recommendation to delay the onset of drug resistance is to estimate the flock mean faecal egg counts by sampling a subpopulation and to treat sheep only when egg counts are high. However, there is little research on the accuracy and precision of estimates of the flock mean obtained from samples. In silico sampling was used to quantify the influence of flock variation, sample size, flock size and mean egg count on the accuracy and precision of the estimated mean egg count. Commonly used and recommended sampling schemes gave alarmingly imprecise estimates of the true flock means. Simply providing a point estimate of the flock egg count can be seriously misleading. Therefore, quantiles were provided for the proportion of estimates in a plausible scenario that is likely to require treatment. It may be more informative to use these quantiles to predict the probability that the true flock mean is sufficiently high to consider treatment.

Prevalence of Abomasum Nematode infection in Sheep from North of Iran

Abstract
 In many countries, small ruminants provide the primary source of human protein and play an important role in livestock production. Parasitic infections, especially gastrointestinal parasites, cause economic losses such as reduced fertility and milk production, damage to the leather industry, weight loss, treatment costs, and losses in severe infections. Thus, identifying and classifying these parasites, including the above cases, is essential for scientific research in any country. This study aimed to Prevalence of Abomasum Nematode infection in Sheep from North of Iran. In the present cross-sectional descriptive study, we have studied the prevalence of infection with abomasum nematodes in sheep in northern Iran from April 2020 to September 2021 in 2400 abomasum sheep slaughtered in industrial slaughterhouses in Gilan and Mazandaran provinces (1200 sheep from each province). With three age groups of below two years, two to four years, and above four years and gender segregation of hosts, after necropsy and preparation of sheep abomasal mucosa chip and isolation and segregation of samples, we studied the morphologic and morphometric characteristics of the samples. The actions were performed according to the taxonomic keys and using SPSS software V.16 and Paired Sample T-Test statistical test to determine the level of significance of the data (p <0.05) to classify and compare the obtained data and examine the ratio. The sex of the host was determined by the age of the animal and the prevalence of the parasite at the mentioned ages. The present study results and comparison of the prevalence of infection in Gilan and Mazandaran provinces showed that Marshallagia marshalli had the highest prevalence of 94.6% and 91.9% in Mazandaran and Gilan province, respectively. The prevalence of Ostertagia circumcincta was 87.2% and 77.2% in Gilan and Mazandaran provinces. The prevalence of Ostertagia occidentalis was 86.9% in Gilan province and 78% in Mazandaran province, while the prevalence of Parabronema skrjabini was 86.6% in Gilan province and 61.2% in Mazandaran province. The prevalence of Haemonchus contortus was 66.8% and 60.5% in Gilan and Mazandaran, the lowest prevalence in these two provinces. The present study results showed the importance of combating the spread of parasitic infections with strategic treatment methods and biological control of these parasites. Also, various reports of drug resistance in abomasal nematodes should be emphasized more and more by competent bodies.
 Keywords: Abomasum, Nematodes, North of Iran, Parasitic infections, Sheep.

The effect of weaning age on animal performance in lambs exposed to naturally acquired nematode infections

The effects of mixed gastrointestinal nematode (GIN) infections on animal growth and post-weaning activity patterns were investigated in grazing intact ram lambs when naturally exposed to two different infection levels and weaned at different ages. Ewes and their twin-born lambs were turned-out to graze in two permanent pasture enclosures naturally contaminated with GIN the previous year. Ewes and lambs in the low parasite exposure group (LP) were drenched before turn-out and at weaning, respectively, with 0.2 mg ivermectin per kg body weight, whereas those in the high parasite exposure group (HP) were left untreated. Two weaning ages were applied, early weaning (EW) (10 weeks) and late weaning (LW) (14 weeks), respectively. The lambs were then allocated to one out of four groups based on parasite exposure level and weaning age (EW-HP, n = 12; LW-HP, n = 11; EW-LP, n = 13; LW-LP, n = 13). Body weight gain (BWG) and faecal egg counts (FEC) were monitored, in all groups, from the day of early weaning and every four weeks, for 10 weeks. In addition, nematode composition was determined using droplet digital PCR. Activity patterns measured as Motion Index (MI; the absolute value of the 3D acceleration) and lying time were monitored continuously from the day of weaning until four weeks post-weaning using IceQube® sensors. Statistical analyses were performed in RStudio, using mixed models with repeated measures. BWG was 11% lower in EW-HP compared with EW-LP (P = 0.0079) and 12% lower compared with LW-HP (P = 0.018), respectively. In contrast, no difference in BWG was observed between LW-HP and LW-LP (P = 0.97). The average EPG was higher in EW-HP compared with EW-LP (P < 0.001), as well as in EW-HP compared with LW-HP (P = 0.021), and LW-HP compared with LW-LP (P = 0.0022). The molecular investigation showed that animals in LW-HP had a higher proportion of Haemonchus contortus compared with EW-HP. MI was 19% lower in EW-HP compared with EW-LP (P = 0.0004). Daily lying time was 15% shorter in EW-HP compared with EW-LP (P = 0.0070). In contrast, no difference in MI (P = 0.13) and lying time (P = 0.99) between LW-HP and LW-LP was observed. The results suggest that a delayed weaning age may reduce the adverse effects of GIN infection on BWG. Contrarily, an earlier weaning age may reduce the risk of H. contortus infection in lambs. Moreover, the results demonstrates a potential use of automated behaviour recordings as a diagnostic tool for the detection of nematode infections in sheep.

Identifying hepatic genes regulating the ovine response to gastrointestinal nematodes using RNA-Sequencing.

Gastrointestinal nematode (GIN) infections are considered the most important disease of grazing sheep and due to increasing anthelmintic resistance, chemical control alone is inadequate. Resistance to Gastrointestinal nematode infection is a heritable trait, and through natural selection many sheep breeds have higher resistance. Studying the transcriptome from GIN-exposed and GIN-unexposed sheep using RNA-Sequencing technology can provide measurements of transcript levels associated with the host response to Gastrointestinal nematode infection, and these transcripts may harbor genetic markers that can be used in selective breeding programs to enhance disease resistance. The objective of this study was to compare liver transcriptomes of sheep naturally exposed to Gastrointestinal nematode s, with either high or low parasite burdens, to GIN-unexposed control sheep in order to identify key regulator genes and biological processes associated with Gastrointestinal nematode infection. Differential gene expression analysis revealed no significant differentially expressed genes (DEG) between sheep with a high or low parasite burden (p-value ≤0.01; False Discovery Rate (FDR) ≤ 0.05; and Fold-Change (FC) of > ±2). However, when compared to the control group, low parasite burden sheep showed 146 differentially expressed genes (64 upregulated and 82 downregulated in the low parasite burden group relative to the control), and high parasite burden sheep showed 159 differentially expressed genes (57 upregulated and 102 downregulated in the low parasite burden group relative to the control) (p-value ≤0.01; FDR ≤0.05; and FC of > ±2). Among these two lists of significant differentially expressed genes, 86 differentially expressed genes (34 upregulated, 52 downregulated in the parasited group relative to the control) were found in common between the two parasite burden groups compared to the control (GIN-unexposed sheep). Functional analysis of these significant 86 differentially expressed genes found upregulated genes involved in immune response and downregulated genes involved in lipid metabolism. Results of this study offer insight into the liver transcriptome during natural Gastrointestinal nematode exposure that helps provide a better understanding of the key regulator genes involved in Gastrointestinal nematode infection in sheep.

PSX-B-11 Classification Performance of Multinomial Logistic Regression for Identifying Resistance, Resilience, and Susceptibility to Gastrointestinal Nematode Infections in Sheep

Abstract The objective was to investigate the feasibility of using easy-to-measure phenotypic traits to predict resistant, resilient and susceptible sheep to gastrointestinal nematodes via multinomial logistic regression (MLR). The database comprised 3,654 records on 1,250 Santa Ines sheep from six farms. The animals were classified into three responses to infection classes (resistant, resilient and susceptible) according to fecal egg count and packed cell volume. The MLR was used to predict such classes using the information of age, month of record, sex, Famacha degree, weight and body condition score as predictors, and a leave-one-farm-out cross-validation technique was used to assess prediction quality across farms. The MLR was able to predict with satisfactory performance the resistant and susceptible animals in two of the farms, with resistant precision equal to 79 and 77%, and susceptible recall equal to 68 and 83%, respectively. In addition, at least one of the classes was well predicted in four farms, with susceptible recall equal to 71 and 89% in two of these farms, and resistant precision equal to 86 and 100% in the other two farms. The model was not able to satisfactorily classify resilient class. The proposed approach could help attenuate the negative impacts related to infections caused by gastrointestinal nematodes, contributing to design deworming strategies that take into account the risk of an animal being contaminated, consequently reducing the costs with anthelmintic administration and laboratory analyses based on blood or fecal samples. The results suggest that the use of easily measurable traits may provide useful information for supporting management decisions on the farm level that could potentially contribute to reducing parasitic contamination and production costs. In addition, the animals identified as resistant can also be incorporated as selection candidates into breeding programs for genetic improvement of flocks.Supported by the São Paulo Research Foundation (FAPESP) grants #2020/03575-8, #2018/01540-2 and #2016/14522-7, SP, Brazil.

Influence of breed and parasite challenge on the immune response to naturally acquired intestinal nematode infection in sheep.

Natural infection by intestinal nematodes was assessed in Santa Ines and Ile de France sheep breeds, over a five-month grazing period, with emphasis on the development of the immune response in lambs under two anthelmintic treatment regimens. Nineteen Santa Ines and 19 Ile de France male lambs were allocated into two treatment groups: animals under suppressive treatment with anthelmintics; and animals under targeted selective treatment (TST). The nematodes Trichostrongylus colubriformis and Strongyloides papillosus showed the highest infection intensity in the TST animals in both breeds. Parasite-specific immunoglobulin G levels were significantly higher and more rapidly induced in Santa Ines lambs. Additionally, these lambs had higher levels of parasite-specific immunoglobulin A in intestinal mucus. Animals under TST had higher means of mast cells and globule leukocytes in the intestinal mucosa due to longer and greater parasite challenge in comparison with the suppressive group. A breed effect (P < 0.05) was recorded for mast cells, with Santa Ines lambs presenting the highest counts. Although Santa Ines lambs had lower intestinal nematode counts than Ile de France lambs, they had shown a large variation in T. colubriformis burden, with most of them presenting a marked worm burden, despite showing an earlier and more intense immune response to intestinal nematode infection.

Identification of Regulatory Functions of LncRNAs Associated With T. circumcincta Infection in Adult Sheep

Several recent studies have demonstrated the role of long non-coding RNAs (lncRNAs) in regulating the defense mechanism against parasite infections, but no studies are available that investigated their relevance for immune response to nematode infection in sheep. Thus, the aim of the current study was to (i) detect putative lncRNAs that are expressed in the abomasal lymph node of adult sheep after an experimental infection with the gastrointestinal nematode (GIN) Teladorsagia circumcincta and (ii) to elucidate their potential functional role associated with the differential host immune response. We hypothesized that putative lncRNAs differentially expressed (DE) between samples from animals that differ in resistance to infection may play a significant regulatory role in response to nematode infection in adult sheep. To obtain further support for our hypothesis, we performed co-expression and functional gene enrichment analyses with the differentially expressed lncRNAs (DE lncRNAs). In a conservative approach, we included for this predictive analysis only those lncRNAs that are confirmed and supported by documentation of expression in gastrointestinal tissues in the current sheep gene atlas. We identified 9,105 putative lncRNA transcripts corresponding to 7,124 gene loci. Of these, 457 were differentially expressed lncRNA loci (DELs) with 683 lncRNA transcripts. Based on a gene co-expression analysis via weighted gene co-expression network analysis, 12 gene network modules (GNMs) were found significantly correlated with at least one of 10 selected target DE lncRNAs. Based on the principle of “guilt-by-association,” the DE genes from each of the three most significantly correlated GNMs were subjected to a gene enrichment analysis. The significant pathways associated with DE lncRNAs included ERK5 Signaling, SAPK/JNK Signaling, RhoGDI Signaling, EIF2 Signaling, Regulation of eIF4 and p70S6K Signaling and Oxidative Phosphorylation pathways. They belong to signaling pathway categories like Cellular Growth, Proliferation and Development, Cellular Stress and Injury, Intracellular and Second Messenger Signaling and Apoptosis. Overall, this lncRNA study conducted in adult sheep after GIN infection provided first insights into the potential functional role of lncRNAs in the differential host response to nematode infection.

Blood parameters and immune responses during haemonchosis

Article Details: Received: 2020-10-06 | Accepted: 2020-11-27 | Available online: 2021-01-31 https://doi.org/10.15414/afz.2021.24.mi-prap.29-32 The aim of this experiment was to determine the effect of medicinal plants ( Artemisia absinthium and Malva sylvestris ) as feed supplements on blood parameters, and local immune responses in the abomasum of Haemonchus contortus infected lambs. Twenty-four lambs were infected orally with 5000 L3 larvae of H. contortus and subsequently randomly divided into four groups: unsupplemented animals (UNS), animals with A. absinthium (ART), animals with M. sylvestris (MAL), and animals with a mix of two plants (ARTMAL). During the experiment, samples of blood were taken for evaluation of hemoglobin and albumin levels. All animals were humanely killed after 75 days of the experiment, and abomasum tissue samples were taken for histopathology. The hemoglobin concentration in the blood was influenced by time ( p&lt; 0.001) and in all groups decreased until day 45. The serum albumin levels were influenced by treatment ( p&lt; 0.05) and time ( p&lt; 0.001) and in all groups occurred reduction until the end of the experiment compared to day 15. The number of plasma cells was higher in ARTMAL compared to MAL ( p &lt; 0.05). UNS and ART had significantly higher numbers of mast cells compared to MAL ( p&lt; 0.01 and 0.05, respectively). The regeneration of abomasal tissue was most frequent in ARTMAL. The results showed that dietary supplementation by A. absinthium and M. sylvestris did not positively affected blood parameters but influenced local immune response in the abomasum of H. contortus infected sheep. Keywords: Haemonchus contortus , sheep, hemoglobin, abomasum, local immune response References Besier, R. et al. (2016). The Pathophysiology, Ecology and Epidemiology of Haemonchus contortus. In Gasser, RB and Samson-Himmelstjerna, G. Haemonchus contortus- Past, present and future trends. (1. ed.). London: Elsevier Ltd (pp. 95-143). Hoste, H. et al. (2016). Interactions between nutrition and infections with Haemonchus contortus and related gastrointestinal nematodes in small ruminants. Advances in Parasitology, 93, 239–351. https://doi.org/10.1016/bs.apar.2016.02.025 McRae, KM. et al. (2015). The host immune response to gastrointestinal nematode infection in sheep. Parasite Immunology, 37(12), 605-613. https://doi.org/10.1111/pim.12290. Mravčáková, D. et al. (2019). Natural chemotherapeutic alternatives for controlling of haemonchosis in sheep. BMC Veterinary Research, 15, 1-13. https://doi.org/10.1186/s12917-019-2050-2 Rouatbi, M. et al. (2016). Effect of the infection with the nematode Haemonchus contortus (Strongylida: Trichostrongylidae) on the haematological, biochemical, clinical and reproductive traits in rams. The Onderstepoort Journal of Veterinary Research, 83(1), 1-8. http://dx.doi.org/10.4102/ojvr.v83i1.1129 Váradyová, Z. et al. (2018). Effects of herbal nutraceuticals and/or zinc against Haemonchus contortus in lambs experimentally infected. BMC Veterinary Research, 14(1), 78. https://doi.org/10.1186/s12917-018-1405-4 Villalba, JJ. Et al. (2017). Phytochemicals in animal health: Diet selection and trade-offs between costs and benefits. Proceedings of the Nutrition Society, 76(2), 113-121. https://doi.org/10.1017/S0029665116000719

129 Evaluation of the effect of Bedoukian compound X administered twice on gastrointestinal nematode infection in sheep

Abstract Gastrointestinal nematodes (GIN) and coccidia have a large financial and health impact on small ruminants. Recent years have seen an increase in anthelminthic/ coccidiostat resistance, and there is a need to develop alternative control methods. The objective of this study was to examine the effect of a unique proprietary compound used in the fragrance/flavor industry with an insect repellant application (Compound X; Bedoukian Research) on parasite control in sheep. Previous research by our laboratories showed a short term reduction in fecal egg count (FEC) in sheep orally drenched with the product. In the current study, naturally infected (GIN and coccidia) Katahdin lambs were orally drenched with 15 mL of Compound X and 15 mL mineral oil (CMX; n = 11) or 30 mL mineral oil (CON; n = 9) on d 0 and 21; FEC/fecal oocyst count (FOC) were determined every 7 d for 8 wk, and feces were cultured to examine GIN larvae. Data were analyzed using a mixed model with repeated measures over time, and regression (SAS). The FEC were reduced in CMX compared with CON between d 0 and 21 (P &lt; 0.03, both mixed model and regression), d 21 and 42 (P &lt; 0.001, mixed and regression), and d 0 and 56 (P &lt; 0.001); FEC were influenced by day of study (P &lt; 0.04), and the interaction tended to be significant using regression (P &lt; 0.10). The FOC were negligible and not analyzed. There was no effect on development of nematode larvae in feces. However, there was a shift in population distribution from Haemonchus contortus to Trichostrongylus spp. which indicated a possible effect on female H. contortus fecundity. There was a sign of toxicity in one lamb following the second CMX drench. The value of using such a compound for GIN control may warrant further investigation.

Planning anthelmintic treatments to control gastrointestinal nematode infections in sheep

A planned approach to anthelmintic treatments against gastrointestinal nematodes in sheep is vital given their clinical and economic importance, and the prevalence of anthelmintic resistance. The key nematode species in the UK are Nematodirus battus, Teladorsagia circumcincta, Trichostrongylus species and Haemonchus contortus. Knowledge of the biology of these species and the annual production cycle on UK sheep farms can guide when treatments may be necessary. The timings of these treatments can be further refined using grazing history, weather conditions and faecal egg counting. This information can then be combined with knowledge of anthelmintic resistance to make a rational treatment decision, and reduce the selection for anthelmintic resistance; for example, by using strategies that maintain populations of parasites in refugia, using multiple active treatments or improving drug bioavailability.

Eprinomectin pour-on: Prevention of gastrointestinal and pulmonary nematode infections in sheep

The present study was conducted to further characterize the anthelmintic activity of the 0.5% w/v topical formulation of eprinomectin (EPRINEX® Pour-on, Merial) when administered at 1 mg/kg body weight to sheep in preventing the establishment of induced gastrointestinal and pulmonary nematode infections.Thirty-six female Merino sheep (∼4 months of age, weighing 27.0–36.0 kg) were blocked by pre-treatment body weight to form blocks of four animals. Within blocks, the animals were randomly allocated to either remain untreated (control) or be treated once with EPRINEX® either on Day 0, Day 7 or Day 14. Starting on Day 15, the sheep were given trickle infections with infective larvae of seven species of gastrointestinal nematodes and Dictyocaulus filaria lungworms daily for seven consecutive days. Five weeks after completion of the daily challenge (Day 56), the animals were necropsied for parasite recovery and count.Treatment with EPRINEX® prevented the establishment (>90%, p ≤ 0.027) of D. filaria, Teladorsagia circumcincta (pinnata/trifurcata), Cooperia curticei, Nematodirus battus, Trichostrongylus colubriformis and Oesophagostomum venulosum for at least 21 days, and of Haemonchus contortus and Trichostrongylus axei for at least 14 days. Sheep in the groups treated with EPRINEX® at Days 7 and 14 had significantly (p ≤ 0.018) higher Day -1 to Day 56 wt gains than the untreated controls.No treatment-related health problems or any other health problems were observed throughout the study.

Controlling nematode infections in sheep: application of HACCP

Gastrointestinal nematode infection in sheep is a significant challenge for production with implications for animal health and welfare, and lamb growth. Flocks rely on the chemical control of worm burdens,...

Morbidity Parameters Associated with Gastrointestinal Tract Nematodes in Sheep in Dabat District, Northwest Ethiopia.

Gastrointestinal nematode (GIN) infections of sheep and their interaction with selected morbidity parameters were studied in smallholder farms. 120 faecal samples were collected and examined using faecal flotation to determine nematode infection in sheep. Thus, the study demonstrated overall prevalence of 57.5% GIN infections, while the mean faecal egg count (FEC) was 517.5 EPG. The severity of GIN infection was determined based on EPG as a mild infection (EPG <500), 55.1%, moderate infection (EPG = 500–1500), 30.4%, and heavy infection (EPG >1500), 14.6%. Five genera of nematodes were identified using coproculture: Haemonchus (33.3%), Trichostrongylus (26.7%), Bunostomum (20%), Oesophagostomum (13.3%), and Cooperia (6.7%). A significant difference was observed in the mean FEC among the FC (P < 0.001), FAMACHA© score (P < 0.01), and the BCS of the animals (P < 0.001). FEC was positively correlated with the FAMACHA© score (FS), while FC and BCS were negatively correlated. Thus, FAMACHA© chart can suggest well the severity of nematode infections and can serve as a suitable on-farm tool to identify nematode-infected sheep and gives a guide to identify sheep that need to be treated with an anthelmintic.

Multiplexed-tandem PCR for the specific diagnosis of gastrointestinal nematode infections in sheep: an European validation study

BackgroundTraditional methods of detecting and identifying gastrointestinal nematode infections in small ruminants, including sheep and goats, are time-consuming and lack in sensitivity and specificity. Recently, we developed an automated multiplexed-tandem (MT)-PCR platform for the diagnosis and identification patent infections with key genera/species of gastrointestinal nematodes of sheep and validated this approach in detailed experiments carried out in Australia. In the present study, we deployed this diagnostic platform in Scotland and Belgium to test samples from naturally infected sheep in these environments and to validate the MT-PCR platform relative to traditional diagnostic methods routinely used by local laboratories.ResultsMT-PCR detected all microscopy positive samples and there was a significant agreement between the results of the different test methods in terms of the species detected and their relative proportion in a test sample, however, for some samples, there were discrepancies between the results of the different test methods. Selective sequencing of purified MT-PCR products demonstrated the results to be 100% specific.ConclusionsThe MT-PCR platform is an advanced method for the species/genus-specific diagnosis of gastrointestinal nematode infections in small ruminants and has demonstrated utility when deployed in different countries and climatic zones. The platform is user-friendly due to the largely automated procedure and has high versatility in that it can achieve a specific diagnosis from different types of sample templates, including larval culture and faecal samples. With appropriate modifications of the primers used, the MT-PCR platform also provides potential for the diagnosis of a variety of other pathogens of veterinary or medical importance.

The host immune response to gastrointestinal nematode infection in sheep.

SummaryGastrointestinal nematode infection represents a major threat to the health, welfare and productivity of sheep populations worldwide. Infected lambs have a reduced ability to absorb nutrients from the gastrointestinal tract, resulting in morbidity and occasional mortality. The current chemo‐dominant approach to nematode control is considered unsustainable due to the increasing incidence of anthelmintic resistance. In addition, there is growing consumer demand for food products from animals not subjected to chemical treatment. Future mechanisms of nematode control must rely on alternative, sustainable strategies such as vaccination or selective breeding of resistant animals. Such strategies take advantage of the host's natural immune response to nematodes. The ability to resist gastrointestinal nematode infection is considered to be dependent on the development of a protective acquired immune response, although the precise immune mechanisms involved in initiating this process remain to be fully elucidated. In this study, current knowledge on the innate and acquired host immune response to gastrointestinal nematode infection in sheep and the development of immunity is reviewed.

Effect of spraying Arthrobotrys conoides conidia on pastures to control nematode infection in sheep

The effect of spraying pastures with conidia of the fungus Arthrobotrys conoides (GenBank ID: JN191309) for the biological control of gastrointestinal nematode infection-pressure in lambs was assessed. A 12,000-m2 area was divided into six 2,000-m2 fenced areas. Two groups were formed: the treatment group comprised three fenced areas, where conidia were sprayed on the pasture weekly at 7.5 x 104 conidia m-2; and the control group, also comprising three fenced areas, where conidia were not sprayed. The pastures included lopsided oat ( Avena strigosa Schreb) and Italian ryegrass ( Lolium multiflorum Lam.). Five naturally infected lambs, were placed between July and September in each fenced area. The effectiveness of biological control was assessed between May and September 2009 by counting the number of third-stage larvae (L3) in each pasture. Additionally, the egg output of the sentinel animals was monitored by counting the number of gastrointestinal nematode eggs per gram of faeces (EPG) and the average weight gain was measured. The negative impact on soil was assessed by counting the number of free-living nematodes and phytonematodes. The number of gastrointestinal nematode larvae in the treated pastures decreased. This was significant at two examination days (end August and end of September). At the end of the study, conidia treatment reduced gastrointestinal nematodes on pasture by 52.4% compared to the control group; this difference was statistically significant. Regarding the whole examination period the average reductions in EPG in treatment group was 49.1% compared to the control group. The most common genera of gastrointestinal nematodes were Haemonchus and Trichostrongylus . Animal weight gain and soil nematode counts did not differ significantly.

An explicit immunogenetic model of gastrointestinal nematode infection in sheep.

Gastrointestinal nematodes are a global cause of disease and death in humans, wildlife and livestock. Livestock infection has historically been controlled with anthelmintic drugs, but the development of resistance means that alternative controls are needed. The most promising alternatives are vaccination, nutritional supplementation and selective breeding, all of which act by enhancing the immune response. Currently, control planning is hampered by reliance on the faecal egg count (FEC), which suffers from low accuracy and a nonlinear and indirect relationship with infection intensity and host immune responses. We address this gap by using extensive parasitological, immunological and genetic data on the sheep–Teladorsagia circumcincta interaction to create an immunologically explicit model of infection dynamics in a sheep flock that links host genetic variation with variation in the two key immune responses to predict the observed parasitological measures. Using our model, we show that the immune responses are highly heritable and by comparing selective breeding based on low FECs versus high plasma IgA responses, we show that the immune markers are a much improved measure of host resistance. In summary, we have created a model of host–parasite infections that explicitly captures the development of the adaptive immune response and show that by integrating genetic, immunological and parasitological understanding we can identify new immune-based markers for diagnosis and control.

Gastrointestinal nematode infections in sheep raised in Botucatu, state of São Paulo, Brazil.

Gastrointestinal nematode infections were evaluated in sheep raised in Botucatu, state of São Paulo, Brazil between April 2008 and March 2011. Every month, two tracer lambs grazing with a flock of sheep were exposed to natural infection with gastrointestinal nematodes for 28 consecutive days. At the end of this period, the lambs were sacrificed for worm counts. Haemonchus contortus presented 100% of prevalence. The seasons exerted no significant influence on the mean intensity of H. contortus, which ranged from 315 worms in November 2010 to 2,5205 worms in January 2011. The prevalence of Trichostrongylus colubriformis was also 100%, with the lowest mean intensity (15 worms) recorded in February 2011 and the highest (9,760 worms) in October 2009. In the case of T. colubriformis, a significant correlation coefficient was found between worm counts vs. rainfall (r = -0.32; P <0.05). Three other nematodes species were found in tracer lambs, albeit in small numbers. Their prevalence and mean intensity (in parenthesis) were as follows: Oesophagostomum columbianum 28% (25.2), Cooperia curticei 7% (4.5) and Trichuris spp. 2% (1). In conclusion, the environmental conditions of the area proved to be highly favorable for the year-round transmission of H. contortus and T. colubriformis.

A Review of the Epidemiology of Gastrointestinal Nematode Infections in Sheep and Goats in Ghana

In this paper, the gastrointestinal nematode parasites infecting small ruminants (sheep and goats) in Ghana and the epidemiological factors influencing their prevalence are reviewed and discussed. Twelve nematode species belonging to six families have been reported to infect these livestock in the country with Haemonchus contortus being the most prevalent helminth parasite in both animals. Parasitic gastroenteritis is caused by mixed infection of several nematode species. Management /husbandry practices, climate and host influence are found to be the main factors that affect gastrointestinal nematode infections in sheep and goats. Seasonal changes in the level of infective strongylate nematode larvae on pasture in the different agro-ecological zones of Ghana are reviewed. The number of infective larvae on pasture is reported to be directly related to the pattern of rainfall. Consequently, rainfall could be relied on to predict the rate of transmission of infection in grazing animals. Finally, the relevance of epidemiological knowledge in the development of efficient measures for controlling gastrointestinal nematode infections in sheep and goats in Ghana is discussed.