Parasitic Infections In Sheep Research Articles

Epidemiological Data Regarding the Distribution of Gastrointestinal Parasites in Albanian Small Ruminants

Background: Gastrointestinal infection of small ruminants is becoming a real problem due to the resistance against anthelmintic treatment. These parasitic infections are prevalent among grazing ruminants and result in significant economic losses by reduced production. The aim of the study was to evaluate and estimate the total loud of parasitic infection is small ruminants, sheep’s and goats from different farms located in Korça district. Methods: This study investigates parasitic infections in sheep and goats across 40 farms situated in Korça district in southeastern Albania. The primary objective is to assess the prevalence of gastrointestinal parasites within feces samples from mature sheep and goats. In total, 121 feces samples were meticulously collected. Samples were analysed and processed using the Mini-FLOTAC technique in order to identify eggs and oocysts in each herd. Result: The results of the investigation revealed the presence of Strongyloides papillosus in 45.45% of samples, Ostertagia spp. eggs in 40.9% of samples, Monezia expansa eggs in 27.2% of samples, Dictiocaulus filaria in 22.3% of samples, Nematodirus spathiger eggs in 13.2% of samples, Haemonchus contortus eggs in 13.3%, Cooperia spp. eggs in 9% of samples, Trichostrongylus axei in 9% of samples, Coccidian oocysts in 4.1% of samples and Trichuris ovis in 1.6% of samples.

Evaluation of the supply of Duddingtonia flagrans for the control of gastrointestinal parasites in sheep.

Parasitic resistance imposes alternative control methods, like nematophagous fungi. In this study, two experiments were conducted supplying Duddingtonia flagrans aiming to evaluate the biological control of parasites in sheep. In the first, 24 sheep naturally infected by gastrointestinal nematodes were allocated, in randomized blocks, following the treatments: control or treated group, 0.5g/animal product containing D. flagrans, chlamydospores. Weight, body score, Famacha©, egg count per gram of feces (EPG), and larval percentage were evaluated. In the second experiment, D. flagrans (0.25 and 0.5g product) was infested with manure, plus or not protein concentrate, in a completely randomized design. In both experiments the dose was intentionally lower than recommended. Recovery and larval identification were performed. The SAS analyzed the variables by the MIXED procedure, repeated measures in time. Weight, body score, hematocrit, and Famacha© did not show differences between treatments (p>0.05); however, EPG (p<0.001) and the percentage of larvae identified in coproculture were different. In the second experiment, the inclusion of the fungus did not influence the recovery of larvae (p>0.05). In both experiments, colonization and advancement of the fungus were visualized. Under the experimental conditions, the fungus D. flagrans was not effective in the biological control of parasitic infection in sheep.

Time Series Model for Forecasting the Prevalence of Some Important Parasitic Infections in Slaughtered Sheep in North-Central Iran

Uncontrolled parasitic infections in livestock can increase the potential risk of transmission between human societies. Owing to the socioeconomic challenges of these diseases in slaughtered sheep, the current study aimed to forecast the prevalence of these infections in a central slaughterhouse in Alborz Province, north-central Iran. Data from 2009 to 2018 on parasitic infections in slaughtered sheep presented at a slaughterhouse were compiled and the prevalence of these diseases was computed. The prevalence has been considered as a time series and afterward, RStudio software using the best-fitted ARIMA model was applied to forecast the monthly variation in prevalence rates. From 2009 to 2018, a total of 1,339,196 sheep were slaughtered in the studied slaughterhouse. The Iranian Afshari breed was the most slaughtered sheep and, a total of 77.6% of these animals were raised under traditional farming system. In addition to the Alborz province, slaughtered sheep were brought from five other provinces, including Zanjan, Qazvin, Qom, Kurdistan, and East Azerbaijan. The highest and lowest total prevalence of studied parasitic zoonoses in slaughtered livestock were cystic echinococcosis (12.76%) and Taenia ovis infection (0.01%), respectively. An approximate stationary trend for fascioliasis and CE and a mild decreasing trend for dicrocoeliasis and sarcocystosis has been forecasted for the next 10 years. Forecasting the prevalence of T. ovis infection showed that without implementing control strategies, this infection would be increased in the years ahead. The current study has demonstrated for the first time the predicting of some important parasitic infections in sheep in Iran. The results provide helpful data for authorities for controlling these diseases in the frontline of meat production. Vast and in-depth forecasting investigations is required to find evidence-based data about these infections for entire the country of Iran.

Can orange essential oil reduce the severity of parasitic infection in sheep?

In this study, a three-step experiment was conducted to evaluate the effectiveness of orange essential oil (OEO) to reduce the severity of parasitic infection in lambs naturally infected with gastrointestinal parasites. In the first and second stages of the experiment, the lambs were distributed in groups (n=10): without treatment (control), treated with levamisole (7.5mg/kg), and treated either with 200, 300 or 400mg/kg OEO in the first stage and with two doses of 300 or 350mg/kg each of OEO with a six-hour interval in the second stage. In the third stage of the experiment, 20 lambs were distributed into control and treated groups (two doses of 350mg/kg OEO) and slaughtered for determining the parasite count in the abomasum and small intestine. Evaluations were performed on D0, D3, D7, D10, and D14 by determining the egg count per gram of feces (EPG), and the percentage of EPG reduction was calculated in comparison to D0. Coproculture was performed on days D0 and D14 of the first and second stages of the study. In the first stage, the EPG increased by 20.90 and 100.99% and decreased by 5.54% on D14 in the groups treated with 200, 300, or 400mg/kg OEO, respectively. At the second stage, the EPG of the OEO groups decreased by more than 96% on D3, but on D14 was decreased by 0.82% and 77.07% in the 2×300 and 2×350mg/kg groups, respectively. Haemonchus sp. was the highest percentage of collected larvae in all coproculture tests, ranging from 90 to 100%. In the third stage, there was no difference (P>0.05) in the mean number of parasites between the OEO groups and the control. Although the decrease in EPG of more than 96% on D3 did not persist in the other evaluations, and immature forms and adult parasites were collected at slaughter, the EPG reduction of 77.07% on D14 with the dose of 700mg/kg (OEO2×350) suggests that OEO can help to reduce the severity of parasitic infection and, consequently, to diminish pastures contamination, when used together with other methods to control gastrointestinal parasites in sheep.

Prevalence and factors influencing gastrointestinal parasitic infections in sheep in Bangladesh.

Gastrointestinal (GI) parasites are major contributors to decrease productivity in livestock over the world. A cross-sectional study was conducted in different areas of Bangladesh to determine the prevalence of GI parasitic infections and their association with the biotic and abiotic factors in sheep. A total of 572 faecal samples were collected from the selected areas of Bangladesh and microscopic examination was performed for the identification of parasites using flotation and sedimentation technique. Out of 572, 441 animals were found infected with one or more species of GI parasites with an overall prevalence of 77.1%. Nine types of parasites from four different classes were detected namely Strongyles (42.1%), Strongyloides sp. (27.1%) and Trichuris sp. (1.0%), Moniezia sp. (2.4%), Paramphistomum cervi (32.5%), Fasciola gigantica (6.1%) and Schistosoma sp. (3.5%), coccidia (16.6%) and Balantidium coli (7.9%). Nematodes infections (56.8%) were significantly highest among trematodes (37.9%), protozoa (24.4%) and cestode (2.4%). In the present study, all the biotic factors including sex, age, physiological condition of female and body condition score (BCS) of animals were insignificantly (p>0.05) associated with the prevalence of GI parasitic infection in sheep but among the abiotic factors, muddy housing of animals, rainy season, having no knowledge about GI parasites and illiteracy of farmers were significantly (p<0.05) associated with the GI parasitic infections. This epidemiological investigation will assist to build a suitable control program against GI parasites in sheep and thus, help to prevent production loss and increase livelihood of small holder farmers.

Studies on prevalence of gastrointestinal parasitic infection in sheep in Kashmir Valley

Studies on prevalence of gastrointestinal parasitic infection in sheep in Kashmir Valley

Prevalence of Gastrointestinal Parasitic Infections in Sheep and Goats of Sandwip Island, Chattogram, Bangladesh

Gastrointestinal (GI) parasitic infection is considered a common problem in sheep and goat production in Bangladesh. The current investigation was undertaken to determine the prevalence of GI parasitic infection and its associated risk factors (e.g., age, sex, nutritional &amp;amp; deworming status etc.) in sheep and goats of the Sandwip Island, Chattogram, Bangladesh. A total of 330 faecal samples of which 220 sheep and 110 goats were taken using a random sampling method. All the samples were subjected to routine coproscopy (e.g., direct smear, flotation and sedimentation) to detect the eggs/oocysts of helminths and protozoan parasites. Results demonstrated that the overall prevalence of GI parasitic infections was 68.64% in sheep and 61.82% in goats. The frequency of nematodes and trematodes was higher in comparison to cestodes and protozoan infections in both sheep and goats of all the three study areas. Age-specific prevalence demonstrated that adult goats had significantly higher GI parasitic infections in comparison to the young population. Female sheep were more prone to GI parasitic infections whereas the opposite trend was noticed for goats. The sheep and goats having the ‘poor’ body condition score/nutritional status were more susceptible to parasitic infections compared to moderate and good health conditions. Rarely or non-dewormed sheep and goats also harboured more GI parasites compared ‘dewormed animals’. The current investigation was fresh of its types in the study areas, therefore, we recommended extensive studies including epidemiological and molecular approaches to identify GI parasitic diseases and their associated risk factors.

The Electrophoretic Pattern of Serum Proteins in Sheep with Naturally Acquired Gastrointestinal Nematode Infections

Abstract The objective of this study was to describe the serum protein pattern in sheep with naturally acquired gastrointestinal parasitosis and to compare the distribution of protein fractions with the results obtained in animals with negative fecal examination results. Fecal and blood samples were taken from twenty-nine sheep positive for nematode eggs and twenty-four animals with negative results of fecal examination. Between the evaluated groups of sheep significant differences were noted in the relative mean values for all protein fractions and for albumin/globulin ratio (p&lt;0.01 and p&lt;0.001). The concentrations of total proteins showed no significant differences between both groups of sheep. The absolute mean values of albumin, α2-globulins and A/G ratio were significantly lower, the mean concentrations of α1-, β-, γ1- and γ2-globulins significantly higher in the nematode positive group of sheep (p&lt;0.01 and p&lt;0.001). In the nematode positive group the protein electrophoretic pattern showed a double α2-zone in three sheep and the γ-globulin zones were characterized by a diffuse higher broad and wide peaks. The presented results indicate that the gastrointestinal parasitic infections in sheep alter the distribution of serum proteins, and suggest their usefulness in animals with unchanged serum protein concentrations. The study brings new findings and extends the knowledge about the metabolic responses and consequences of gastrointestinal parasitic infections in sheep, particularly with regard to alterations in protein metabolism.

Estimation of Serum Copper Concentrations in Sheep and Goats Infected with Gastrointestinal Parasites in Mosul City, Iraq

The objective of the present study was to determine serum copper concentrations in sheep and goats infected with different gastrointestinal parasites. A total of 60 sheep and 30 goats were obtained from different areas in Mosul city and examined in the Veterinary Teaching Hospital, University of Mosul. Fecal and blood samples were collected from each animal. Animals infected with gastrointestinal parasites were diagnosed by detecting parasite eggs in fecal samples. Copper concentrations and hematological values were compared between infected and non-infected animals. Different gastrointestinal parasites were diagnosed include; Chabertia ovina, Cooperia spp., Haemonchus contortus, Marshallagia marshalli, Nematodirus spp., Oesophagostomum spp., Ostertagia ostertagia, Strongylus spp. and Trichostrongylus spp. in both single and mixed infection types. Infected sheep and goats suffered from different clinical signs such as emaciation, poor wool or hair, trembling, pale mucous membrane, loss of appetite, and diarrhea. Infected animals showed significantly (p≤0.05) lower serum copper concentrations compared to non-infected animals. Moreover, hematological parameters (RBC, Hb, PCV, MCH, MCV, and MCHC) were lower compared to non-infected animals. In conclusion, gastrointestinal parasitic infection in sheep and goats can decrease serum copper concentrations and blood parameters in infected animals, thereby exacerbating clinical signs.

Prevalence of gastrointestinal parasitic infections in sheep of a coastal belt under Noakhali district, Bangladesh

Gastrointestinal (GI) parasitic infection is considered one of the major concerns in sheep production in Bangladesh. The current study was undertaken to determine the GI parasitic infections in sheep reared in bathan area and semi-intensive conditions of six (6) randomly selected areas of Subarnachar upazila under Noakhali costal belt. A total of 200 fecal samples were collected and examined to detect the ova of GI parasites using routine coproscopical tests (e.g. direct smear, sedimentation and flotation). Results demonstrated that the overall prevalence of GI infections in sheep was found 79.50%, where infections caused by trematodes were the highest in comparison to cestode and nematodes. The frequency of GI parasites were more common in all the study areas where the higher prevalence was recorded in Char Clark, Char Jabbar and Char Bata which ranged around 82-84% compared to other areas. Further, sheep reared in bathan areas (82.66%) were found to be more susceptible to GI parasitic infections compared to sheep kept on semi-intensive condition (77.60%). Furthermore, the occurrence of GI parasites was significantly higher in female sheep compared to male. The present study documented the occurrence of GI parasites which might reduce the production performance of the animals of that coastal belt. We recommend further extensive study for molecular detection of such parasitic infections including growing awareness among sheep owners to prevent and control of those infections.

EFEITO DO PARASITISMO POR Haemonchus contortus SOBRE O METABOLISMO OXIDATIVO DE LEUCÓCITOS DE OVINOS

Resumo A resposta imune tardia direcionada para eliminação da hemoncose pode ser modulada pelo perfil Th2, sendo os eosinófilos as principais células efetoras responsáveis pela eficiente eliminação do parasita; ou modulada pelo perfil Th1, sendo os neutrófilos as principais células efetoras, que promovem eliminação parasitária mais deficiente, pois testes in vitro demonstraram que o parasita deprime o metabolismo oxidativo dos fagócitos. Desta maneira, este trabalho objetivou avaliar se o grau de infecção parasitária observado pela quantidade de ovos por grama de fezes (OPG) de Haemonchus contortus interfere no leucograma e se impacta no metabolismo oxidativo leucocitário em ovino naturalmente acometido por hemoncose. Para tanto, 39 ovinos machos adultos e sem alterações no exame físico, excetuando-se a coloração das mucosas, foram separados em 4 grupos conforme a infecção parasitária 0-350 (n=15), 400 a 1000 (n=10), 1100-2000 (n=7) e 2100-4700 (n=7). Notou-se correlação significativa positiva entre OPG e neutrófilos (r=0,56; P=0,0003) e significativa negativa entre OPG e eosinófilos (r=-0,50; P=0,0012) e OPG e metabolismo oxidativo leucocitário (P=0,0001), permitindo concluir que há relação entre as células efetoras e a severidade de infecção parasitária em ovinos naturalmente infectados por hemoncose. Também se verificou que a alta infecção parasitária promove diminuição do metabolismo oxidativo de leucócitos.

Evaluation of the role of galectins in parasite immunity.

Galectin-11 and galectin-14 are ruminant galectins involved in parasitic infections. Although their roles in parasite immunity are still being elucidated, its appears that their functions are parasite specific. In gastrointestinal infections with the nematode Haemonchus contortus, both galectin-11 and galectin-14 appear to be protective. However, in a chronic infection of liver fluke, Fasciola hepatica, these galectins may aid parasite survival. This chapter discusses the methods designed to study parasitic infections in sheep, which have provided us with insight into the functions of galectin-11 and galectin-14 during host-parasite interactions. These methods include parasite cultivation and infection, galectin staining of host and parasite tissue, surface staining of parasites with recombinant galectins and in vitro assays to monitor the effect of galectins on larval development.

Understanding the epidemiology of gastrointestinal parasitic infections in sheep: What does a faecal helminth egg count tell us?

Faecal helminth egg counts can provide evidence of the presence of helminth parasites, but do not necessarily reflect helminth disease. Over-reliance of nematode faecal egg counts may be unhelpful in deciding on the need to treat sheep with an anthelmintic drug and hinders the long-term goal of selection of resilient animals. There is, therefore, a need to develop alternative indices of helminth parasitism that take into account the key objective of helminth control, which is to prevent significant production loss, by determining whether or not animals are actually suffering performance loss from infection. Faecal helminth egg counts are of greatest relevance in developing our understanding of parasite epidemiology, which is of paramount importance given the evolutionary potential of helminth parasites to adapt to changing conditions and in the development of sustainable strategies for their control.

Prevalence of gastro-intestinal parasitic infections in Sheep of Kashmir valley of India

Background: Geologically the J&K state (2, 22, 800 sq. kms) is both complex and varied. Climatic conditions of the state ranges from sub-tropical (Jammu), temperate (Kashmir) to cold artic (Ladakh) zones and belongs to the great Himalayan mountain range, which exerts significant influence on its agro-climatic conditions. Gastrointestinal parasitism is a major problem in sheep production worldwide, these parasites cause diarrhea, anaemia, reduced weight gain and increased production costs. Materials and Methods: Five hundred fecal samples of sheep (Ovis aries) were taken from two farms. All fecal samples were examined to determine the prevalence of gastrointestinal parasites. Direct microscopic examination, Centrifugation floatation and Sedimentation techniques were used to examine fecal samples. Results: Overall prevalence rate was 62.9%. most commonly encountered parasites were Strongyle spp., Strongyloides spp., Eimeria spp., Nematodirus spp., and Monezia spp. was 24.61, 15.5, 9.8, 9.0 and 3.3%, respectively. The highest prevalence of G.I parasites was recorded during monsoon season (March - May) followed by summer season (June – August) whereas the lowest prevalence was recorded during winter season. Analysis of the data on the basis of sex revealed a significant difference (P<0.05) in the overall incidence of gastrointestinal parasites between male (75.6%) and female (44.8%) sheep. The maximum infection was observed in younger age groups compared to adults (P<0.05). The prevalence of different species of endoparasites also varied in sheep of different body weight groups (P<0.05). The highest infection was observed in Kashmir Marino breed than corriedale breed. Conclusion: The data obtained in this study suggest that the age, sex, body weight and breed are important factors which influence the prevalence of gastrointestinal parasites. Key wards: climate, economy, faecal sample, Kashmir valley, parasite, prevalence, sheep

Prevalence of Parasitic Infection in Sheep From different Regions in Baghdad

This research concerns (306)faecal samples from different regions in Baghdad from sheep were examined,the results showed that 230 samples were infected with gastrointestinal parasites with total rate 75.1% which included : 49.0% of coccidiosis ( 9 species of Eimeria were recorded E.parva, E.ovina, E.crandalli s, E. weybridgensi, E. pallida, E. granulosa E .faurei, E. ovinadalis E.marsica) , 21.2% Nematodes 7.84% ,6.5% ,4.5%, 2.2% for Haemonchus, Trichostrongylus ,Nematodiru,and Trichuris in respectively , while the percentage of trematodes &amp; cestodes infections were 4.9% for fasciola 2.28% , Paramphistomum 1.6% , Moniezia 0.9% .Age factor influenced on infection percentage it is higher in younger with coccidiosis infection 25.4% while it is higher in aged animals with nematodes% 10.13 &amp; 1.96% for trematodes &amp; cestodes. Prevalence of coccidiosis infection showed seasonal diversity it is higher in winter, while the rate of infection with nematodes &amp; trematodes is higher in summer &amp; lowers in winter.

Effects of age and immune suppression of sheep on fecundity, hatching and larval feeding of different strains of Haemonchus contortus

The effects of host age and immune suppression on abomasal parasitic infection in sheep were investigated following single experimental oral infections with MHco3 (ISE), MHco4 (WRS) and MHco10 (CAVR) strains of Haemonchus contortus in naïve 5-month-old crossbred lambs (n=1 per group) and 15-month-old Greyface sheep treated with methyl prednisolone acetate (n=2 per group) or without corticosteroid treatment (n=2 per group). Adult female H. contortus in 5-month-old lambs (n=1 per group) shed on average 6.5, 3.1 and 8.0 times more eggs than in 15-month-old sheep (n=4 per group) following infection with MHco3 (ISE), MHco4 (WRS) and MHco10 (CAVR) strains of H. contortus, respectively, over a period of 28 days following the commencement of patency. There was no obvious effect of age of sheep or corticosteroid treatment on the abomasal establishment of H. contortus or on in vitro assays for egg hatching or larval feeding at different concentrations of anthelmintics, although statistical analysis could not be performed due to the small group sizes.

Effect of forage legumes and anthelmintic treatment on the performance, nutritional status and nematode parasites of grazing lambs

Recent studies in New Zealand and the UK have shown that certain forages reduce parasitic infection in sheep. The aim of this experiment was to investigate the effects of legume forages compared to ryegrass on interactions between production, nutritional status and nematodes in grazing lambs. Twenty-four male lambs per forage treatment, half of which were treated with anthelmintics on Day 0, grazed monocultures of lucerne ( Medicago sativa), red clover ( Trifolium pratense) and white clover ( Trifolium repens) and were compared with lambs grazing perennial ryegrass (Lolium perenne). Individual faecal egg counts (FEC) and liveweight were determined every 7 days for 56 days, after which half the lambs were slaughtered to determine total nematode intensities (TNI). Results showed that lambs grazed on red or white clover, but not lucerne, had lower pooled mean FEC and improved liveweight performance compared to lambs grazing ryegrass. Lambs treated with anthelmintics had higher TNI compared to lambs not treated, due to a trend for more adult nematodes in lambs grazing lucerne and treated with anthelmintics than all other lambs, except those grazing red clover and also given anthelmintics. Lambs grazing white clover tended to have fewer adult nematodes than lambs grazing other forages. Examination of the nematode species showed a change in female T. circumcincta occurred in all lambs following anthelmintic treatment and that the forage species grazed by lambs affected individual parasite species. Lambs grazing white clover had fewer male and adult T. circumcincta compared to lambs grazing other forages, and lambs grazing lucerne had fewer adult T. circumcincta compared to lambs grazing ryegrass or red clover. Data on small intestine TNI showed that lambs grazing lucerne and given anthelmintics had more male adult nematodes than other lambs, except those grazing red clover and treated with anthelmintics. Results indicate that lucerne and red clover both increase the re-infection of grazing lambs with Trichostrongylus species compared to ryegrass following anthelmintic treatment. In conclusion, legume forages have the potential to contribute to the control of abomasal but not small intestine nematode parasites in finishing lamb systems.

Quantitative trait loci associated with parasitic infection in sheep

Gastrointestinal nematodes cause major losses to the UK sheep industry. As anthelmintic resistance is becoming a widespread problem alternative control methods are now sought. Breeding for improved parasite resistance is a possible control method (Woolaston and Windon, 2001). As genetic markers are now widely available there is considerable potential for application to livestock breeding through quantitative trait loci (QTL) detection and subsequent marker-assisted selection schemes. Although much work is underway, there are few published studies that identify QTL associated with parasite resistance. Therefore this study aims to identify QTL associated with parasitic nematode infection in a population of Scottish Blackface lambs using faecal egg count and Immunoglobulin A activity.

Epidemiology of parasitosis in the Tzotzil sheep production system

The prevalence of parasitic infections in sheep caused by Eimeria spp., intestinal nematodes, Dictyocaulus filaria and Fasciola hepatica was analyzed. The study was carried out in 78 crossbred adult sheep, from 15 different flocks (10.5±6.5 sheep), which belonged to five different indigenous Tzotzil communities in the highlands of Chiapas, Mexico. Feces were collected for parasitologic analysis during the four seasons of the year. The results indicated a high average prevalence of Eimeria sp. (81.7%) and intestinal nematodes (76.9%), with a higher presence of subclinical infection, and a lower proportion of moderate and severe infection during summer and winter. The occurrence of Fasciola hepatica (37.5%) and Dictyocaulus filaria (16.7%) was also concentrated at summer and winter. Geographically, the highest prevalence of Eimeria spp. was found at Bautista Chico (90.0%) and Luquilhó (83.0%); of intestinal nematodes at Mitzitón (90.0%) and Nachig (87.0%). Fasciola hepatica highest prevalence was at Nachig (50.0%) and Mitzitón (50.0%); and Dictyocaulus filaria at Mitzitón (35.0%) and Nachig (25.0%). The occurrence of ectoparasites was also investigated. The seasonal fluctuation of parasitic infections was correlated ( r≥0.60) with climatic changes, forage availability, dry matter intake and body weight. The environmental factors, when associated with poor management of the flocks, reduced the tolerance of sheep to the different parasitoses.

Consequences of long-term feeding with condensed tannins on sheep parasitised with Trichostrongylus colubriformis

Naive wethers were used to investigate the long-term effects of dietary condensed tannins from Quebracho extract, during an intestinal parasitic infection in sheep. Sheep were allocated to eight groups; seven groups were daily infected with 3000 L 3 Trichostrongylus colubriformis for 10 weeks and the eighth group was the uninfected control. The 10-week experiment was divided into two periods; Period 1 (P 1, week 1–5) corresponded to high worm establishment and acquisition of immunity, whereas Period 2 (P 2, week 6–10) to the established worm population and expression of host immunity. Three experimental foods with similar composition were formulated: Q0, Q3 and Q6. Their difference was in the content of Quebracho extract which was 0, 30 and 60 g per kg fresh matter, respectively. All foods were offered at an allowance of 3.5% of sheep liveweight. During P 1, parasitised sheep were offered one of the three experimental foods and during P 2 they either remained on the same food or changed food according to the design (P 1–P 2): Q0–Q0, Q0–Q3, Q0–Q6, Q3–Q0, Q3–Q3, Q6–Q0, Q6–Q6. Control sheep were offered the allowance of Q0 throughout. Sheep that consumed Q3 and Q6 reduced their faecal egg counts (FEC) compared to sheep offered Q0, during both periods ( P<0.05). No differences were observed in the FEC between sheep offered Q3 and Q6. The changeover from Q0 in P 1 to either Q3 or Q6 during P 2, was accompanied by a reduction in FEC ( P<0.05), whereas an increase in FEC was observed when food changed from Q3 or Q6 to Q0 ( P<0.05). Worm burdens and fecundity at the end of the experiment were reduced in sheep offered foods Q3 and Q6 compared to sheep offered Q0. A significant decrease in liveweight gain and in food conversion efficiency of parasitised sheep offered Q3 and Q6 compared to sheep offered Q0, was observed in P 1 ( P<0.05) but not in P 2. By the end of the experiment control sheep had achieved higher liveweight and converted food more efficiently than parasitised sheep ( P<0.05). In conclusion, evidence for a long-term effect of Quebracho extract, during both the initial establishment and on the established T. colubriformis population in sheep, was provided by the present study. It is suggested that the effect observed was a direct anthelmintic effect of the condensed tannins included in sheep diets.