[Show abstract][Hide abstract] ABSTRACT: Cattle besnoitiosis due to Besnoitia besnoiti is spreading across Europe and is responsible for severe economic losses in newly infected herds. Experimentally speaking, rabbits have been found to be susceptible to this parasite. The adaptation of B. besnoiti to rabbits may offer a new, easier and cheaper model of investigation for this disease. This study compared the virulence between tachyzoites and bradyzoites of B. besnoiti in rabbits. Eighteen New Zealand rabbits were allocated into three groups of six animals each. The rabbits from the control (group C), "tachyzoite" (group T) and "bradyzoite" (group B) groups were subcutaneously injected in the right flank with 66 μg of ovalbumin, 6.10(6) tachyzoites (125th passage on Vero cells) and 6.10(6) bradyzoites (collected from a natural infected cow) of B. besnoiti, respectively. Clinical follow-up and blood sampling for serological survey and qPCR were performed during 10 weeks until euthanasia. Molecular and immunohistochemistry examination was achieved on 25 samples of tissue per rabbit. Seroconversion occurred in group T without any clinical signs. Rabbits of group B exhibited a febrile condition (temperature above 40 °C from day 8 to day 11 following injection) with positive qPCR in blood. Cysts of B. besnoiti were found on skin samples and organs of rabbits from group B in tissue explored with threshold cycle (Ct) values below 30. These results suggest a higher virulence of bradyzoites in rabbits than Vero cell-cultivated tachyzoites. The proposed model could be used to assess the in vivo effectiveness of vaccine or drugs against cattle besnoitiosis.
Parasitology Research 07/2015; DOI:10.1007/s00436-015-4612-y · 2.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study reports a functional characterization of a limited segment (QTL) of sheep chromosome 12 associated with resistance to the abomasal nematode Haemonchus contortus. The first objective was to validate the identified QTL through the comparison of genetically susceptible (N) and resistant (R) sheep produced from Martinik x Romane back-cross sheep. The R and N genotype groups were then experimentally infected with 10 000 H. contortus larvae and measured for FEC (every three days from 18 to 30 days post-challenge), haematocrit, worm burden and fertility. Significant differences in FEC and haematocrit drop were found between R and N sheep. In addition, the female worms recovered from R sheep were less fecund. The second step of the characterization was to investigate functional mechanisms associated with the QTL, thanks to a gene expression analysis performed on the abomasal mucosa and the abomasal lymph node. The gene expression level of a candidate gene lying within the QTL region (PAPP-A2) was measured. In addition, putative interactions between the chromosome segment under study and the top ten differentially expressed genes between resistant MBB and susceptible RMN sheep highlighted in a previous microarray experiment were investigated. We found an induction of Th-2 related cytokine genes expression in the abomasal mucosa of R sheep. Down-regulation of the PAPP-A2 gene expression was observed between naive and challenged sheep although no differential expression was recorded between challenged R and N sheep. The genotyping of this limited region should contribute to the ability to predict the intrinsic resistance level of sheep.
Veterinary Research 06/2014; 45(1):68. DOI:10.1186/1297-9716-45-68 · 3.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bovine besnoitiosis is a chronic and debilitating disease observed in many European countries that may cause important economic losses in cattle. The recent widespread of the parasite in Europe had led the European Food Safety Authority to declare bovine besnoitiosis as a re-emerging disease in Europe. Many aspects of the epidemiology of bovine besnoitiosis such as the main routes of transmission are still unclear and need to be further studied. Among the different hypotheses, a sexual transmission has not yet been investigated. Therefore, the aim of this study was to evaluate the presence of Besnoitia besnoiti DNA in the semen of naturally infected bulls by using a highly sensitive method (real-time qPCR). Both pre-sperm and sperm fractions of 40 bulls, including seronegative (n = 11), seropositive subclinically (n = 17), and seropositive clinically (n = 12) infected animals, were collected by electroejaculation and analyzed by real-time qPCR. No B. besnoiti DNA was detected in 27 pre-sperm and 28 sperm fractions of the 40 examined bulls, suggesting that the transmission of B. besnoiti infection by the semen of chronically infected bulls is very unlikely.
Parasitology Research 05/2014; 113(6). DOI:10.1007/s00436-014-3894-9 · 2.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bovine besnoitiosis is an emergent disease in Europe  and is responsible for heavy economic losses. Most affected animals are asymptomatic and constitute a reservoir that must be identified as quickly as possible. This work presents the development of an indirect immunofluorescence antibody test (IFAT) at the Laboratory of Parasitology in ENV Toulouse. In this study, we evaluated the performance of the IFAT compared to Western Blot (Gold Standard) and to ELISA, through the analysis of 403 sera and using four dilutions (1:100, 1:200, 1:400, 1:800). Considering the positive cut-off at 1:200 serum dilution, the IFAT showed an almost perfect test agreement with the Western Blot; (κ = 0.940) showing a relative sensitivity of 91.8% and a relative specificity of 100%. The test appears as a very useful tool to confirm the serological status of samples that exhibited a discrepancy between findings of commercial ELISA kits and WB.
Revue de médecine vétérinaire 01/2014; 165(11-12):327-333. · 0.25 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cattle besnoitiosis due to the cyst-forming coccidian parasite Besnoitia besnoiti has recently been reported in expansion in Europe since the end of the twentieth century. The B. besnoiti life cycle and many epidemiological traits are still poorly known. Hematophagous flies, including the worldwide-distributed Stomoxys calcitrans, could be mechanical vectors in the contamination of mouthparts after the puncture of cutaneous cysts or ingestion of infected blood. In this study, a protocol is presented to assess more deeply the role of S. calcitrans, reared in laboratory conditions, in parasite transmission. A preliminary trial showed that stable flies could transmit tachyzoites from bovine artificially parasite-enriched blood to B. besnoiti-free blood using glass feeders. Evidence of transmission was provided by the detection of parasite DNA with Ct values ranging between 32 and 37 in the blood recipient. In a second time, a B. besnoiti-infected heifer harboring many cysts in its dermis was used as a donor of B. besnoiti. An interruption of the blood meal taken by 300 stable flies from this heifer was performed. Immediately after the blood meal was interrupted, they were transferred to a glass feeder containing B. besnoiti-free blood from a non-infected heifer. Quantitative PCR and modified direct fluorescence antibody test (dFAT) were used to detect B. besnoiti DNA and entire parasites, respectively, in the blood recipient, the mouthparts, and the gut contents of S. calcitrans at two time intervals: 1 and 24 h after the interrupted blood meal. Parasite DNA was detected at both time intervals (1 and 24 h) in all samples (blood recipient, mouthparts, and gut contents of stable flies) while entire parasites by dFAT were only found in the abdominal compartment 1 h after the interrupted blood meal. Then, S. calcitrans were able to carry B. besnoiti from chronically infected cattle to an artificial recipient in the conditions of the protocol.
Parasitology Research 10/2012; 112(2). DOI:10.1007/s00436-012-3157-6 · 2.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Gastrointestinal nematodes are one of the main health issues in sheep breeding. To identify loci affecting the resistance to Haemonchus contortus, a genome scan was carried out using 1275 Romane x Martinik Blackbelly back-cross lambs. The whole population was challenged with Haemonchus contortus in two consecutive experimental infections and fecal egg counts (FEC) and packed cell volumes were measured. A subgroup of 332 lambs with extreme FEC was sacrificed to determine the total worm burden, length of female worms, sex ratio in the worm population, abomasal pH and serum and mucosal IgG responses. The pepsinogen concentration was measured in another subset of 229 lambs. For QTL detection, 160 microsatellite markers were used as well as the Illumina OvineSNP50 BeadChip that provided 42,469 SNP markers after quality control. Linkage, association and joint linkage and association analyses were performed with the QTLMAP software. The linkage disequilibrium was estimated within each pure breeds and association analyses were carried out either considering or not the breed origin of the haplotypes. Four QTL regions on OAR5, 12, 13 and 21 were identified as key players among many other QTL with low to moderate effects. A QTL on OAR21 affecting the pepsinogen concentration exactly matched the pepsinogen (PGA5) locus. A 10-Mbp region affecting FEC both the 1st and 2nd infections was found on OAR12. SNP markers outperformed microsatellites in the linkage analysis. Taking advantage of the linkage disequilibrium helped to refine the locations of the QTL mapped on OAR5 and 13.
[Show abstract][Hide abstract] ABSTRACT: Bovine besnoitiosis is considered an emerging chronic and debilitating disease in Europe. Many infections remain subclinical, and the only sign of disease is the presence of parasitic cysts in the sclera and conjunctiva. Serological tests are useful for detecting asymptomatic cattle/sub-clinical infections for control purposes, as there are no effective drugs or vaccines. For this purpose, diagnostic tools need to be further standardized. Thus, the aim of this study was to compare the serological tests available in Europe in a multi-centred study. A coded panel of 241 well-characterized sera from infected and non-infected bovines was provided by all participants (SALUVET-Madrid, FLI-Wusterhausen, ENV-Toulouse, IPB-Berne). The tests evaluated were as follows: an in-house ELISA, three commercial ELISAs (INGEZIM BES 12.BES.K1 INGENASA, PrioCHECK Besnoitia Ab V2.0, ID Screen Besnoitia indirect IDVET), two IFATs and seven Western blot tests (tachyzoite and bradyzoite extracts under reducing and non-reducing conditions). Two different definitions of a gold standard were used: (i) the result of the majority of tests ('Majority of tests') and (ii) the majority of test results plus pre-test information based on clinical signs ('Majority of tests plus pre-test info'). Relative to the gold standard 'Majority of tests', almost 100% sensitivity (Se) and specificity (Sp) were obtained with SALUVET-Madrid and FLI-Wusterhausen tachyzoite- and bradyzoite-based Western blot tests under non-reducing conditions. On the ELISAs, PrioCHECK Besnoitia Ab V2.0 showed 100% Se and 98.8% Sp, whereas ID Screen Besnoitia indirect IDVET showed 97.2% Se and 100% Sp. The in-house ELISA and INGEZIM BES 12.BES.K1 INGENASA showed 97.3% and 97.2% Se; and 94.6% and 93.0% Sp, respectively. IFAT FLI-Wusterhausen performed better than IFAT SALUVET-Madrid, with 100% Se and 95.4% Sp. Relative to the gold standard 'Majority of test plus pre-test info', Sp significantly decreased; this result was expected because of the existence of seronegative animals with clinical signs. All ELISAs performed very well and could be used in epidemiological studies; however, Western blot tests performed better and could be employed as a posteriori tests for control purposes in the case of uncertain results from valuable samples.
[Show abstract][Hide abstract] ABSTRACT: Bovine besnoitiosis, caused by the cyst-forming apicomplexan Besnoitia besnoiti, is commonly reported in some restricted regions of South-Western Europe, and in larger regions of Africa and Asia. This infection is thought to be transmitted by blood feeding insects and is responsible for major economic losses in cattle production. A recent emergence in Europe, notified in the Centre of France, Spain and Germany, has attracted more attention to this disease. Clinical signs could appear in some animals; however, many infected cattle remain asymptomatic or show scleral-conjunctival cysts (SCC) only. Recent development of serological methods allows carrying out seroepidemiological field studies. In this respect, a long-term investigation was performed in a dairy cattle farm localized in an enzootic area of besnoitiosis of South-western France between March 2008 and May 2009. The objective was to estimate the seasonal pattern of B. besnoiti infections based on the presence of SCC and serology (ELISA and Western blot). In parallel, an entomological survey was conducted to describe population dynamics of Stomoxys calcitrans and Tabanidae species. The seroprevalence determined by Western blot in a cohort of 57 animals continuously present during the whole survey increased from 30% in March 2008 to 89.5% in May 2009 and was always higher than the prevalence based on clinically assessed SCC. New positive B. besnoitia seroconversions occurred throughout the year with the highest number in spring. In addition, many seroconversions were reported in the two months before turn-out and could be associated with a high indoors activity of S. calcitrans during this period.
[Show abstract][Hide abstract] ABSTRACT: A comparative experimental study was performed between Barbados Black Belly (resistant) and INRA-401 (susceptible) breeds of sheep in which primary infection with Haemonchus contortus was terminated on day 16. Measurements of parasite burden, abomasal tissue eosinophilia, IL-4, IL-5 and IL-13 mRNA transcripts in abomasal mucosa, and in vitro larval killing abilities of blood eosinophils were performed. The results show that: (1) worm burden was significantly lower and blood eosinophilia higher in the Black Belly than in the INRA breed. (2) Abomasal cytokine expression was noticed but no difference existed between the two breeds. (3) Three out of four Black Belly sheep had higher tissue eosinophil numbers compared to the INRA sheep (more eosinophils observed in the pyloric than in the fundic region in both breeds). (4) No significant difference was observed in the in vitro larval immobilizing potential of eosinophils between the two breeds. Collectively, abomasal eosinophil number and larval killing abilities of blood eosinophils do not seem to explain the difference in worm burden between the two breeds.
[Show abstract][Hide abstract] ABSTRACT: Larvae of Oestrus ovis (Diptera: Oestridae) are ubiquitous parasites of nasal and sinusal cavities of sheep and goats. According to the chronobiology of O. ovis infections in Sardinia and the seasonal pattern of the IgG response, the optimal period to investigate the relationships between O. ovis larval populations and intensity of local and systemic IgG antibody responses was mid-July in the summer season. Sarda x Lacaune ewes (n=186), divided into three ram-families were used in the study. Systemic and local IgG responses were measured by ELISA tests using second stage larval crude extracts (L2CE) and L2 (L2SGC) and L3 (L3SGC) salivary gland contents as coating antigens. The number of larval instars, larval length of L1, L2 and L3 larvae, and larval weight of L2 and L3 larvae were individually recorded after ewe necropsy. Negative correlations among larval establishment and/or larval development on the one hand and intensity of local or systemic IgG responses on the other hand were found in two out of three studied ram-families.
[Show abstract][Hide abstract] ABSTRACT: The immune responses to Haemonchus contortus were compared in studies in resistant Barbados Black Belly (BBB) and susceptible INRA 401 (INRA) breeds of lambs. The cytokine patterns indicated a Th2-biased response in both breeds. A more persistent and elevated Th2 cytokine mRNA transcription and blood eosinophilia were noted in the BBB lambs. However, at days 4 and 30 post-infection, abomasal recruitment of eosinophils and mast cells were similar between the two breeds. Following primary infections, the BBB demonstrated a substantially lower faecal egg count compared to the INRA lambs. Furthermore, worm counts at 4 and 30 days post-infection, and adult female worm size and in utero egg counts 30 days after the first infection were significantly lower in the BBB than in the INRA breed. In the INRA breed, re-infection caused a significant reduction in most parasitological parameters compared with those observed after the primary infection. A similar response was not observed in the BBB sheep. In conclusion, while the major driving force in the response to H. contortus infection is a Th2-biased immunity in which the BBB showed its maximal performance during the primary infection, the INRA breed performed better after re-infection compared to its response to first exposure.
[Show abstract][Hide abstract] ABSTRACT: Different authors have reported that eosinophils are capable of immobilising infective larvae of different species of nematodes in vitro. However, classifying larvae as mobile or immobile is so subjective that it does not always mean all apparently immobile larvae are dead or those that are mobile are capable of surviving further immune responses if administered to their natural hosts. The objective of this experimental study was therefore to substantiate the role of eosinophils in the killing of Haemonchus contortus infective larvae by comparing the infectivity in sheep of larvae that had been incubated with eosinophil-enriched cell suspensions with control larvae. Since it was not possible to isolate pure eosinophils from sheep blood, we were compelled to evaluate the effects of other blood cells contaminating our eosinophil-enriched suspensions. Although eosinophils and neutrophils were the only cells found adherent to H. contortus infective larvae in vitro, induced eosinophils in the presence of immune serum were primarily responsible for the drastic reduction in larval motility compared to the minor effects of neutrophils and mononuclear cells. Corresponding reductions in faecal egg count and worm numbers were observed when the incubated larvae were transferred intra-abomasally to sheep. Interestingly, the proportion of larvae that failed to establish was much higher following incubation with induced eosinophils compared with other cells or with immune serum alone. Although this study did not address the in vivo role of eosinophils in sheep, the results strongly indicate that sheep blood eosinophils have a larval killing potential in vitro, and a larval mobility test alone may not fully explain the level of damage inflicted on the larvae.
Veterinary Research 07/2007; 38(4):647-54. DOI:10.1051/vetres:2007019 · 3.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Larval midgut proteins of hematophagous parasites contain strong antigens that can be used for host immunization. This concept has been applied for immunization of Pelibuey sheep against Oestrus ovis L. (Diptera: Oestridae). The aim of this study was to examine the effect of immunization on larval establishment (LE) and development. Immunized lambs (I, n = 6) received two injections of crude gut membrane protein extracts (GMPE) from third instar larvae with Freund's incomplete adjuvant (FIA) on days 0 (Day of first immunization) and 21 (0.4 and 0.45 mg GMPE/lamb, respectively). The control group (C, n = 5) received physiological saline with FIA. Lambs were challenged with first instars on Day 29 (20 larvae) and Day 43 (25 larvae). Blood samples were collected biweekly and IgG titers were analyzed by ELISA. All lambs were slaughtered on Day 90 and number of larvae recovered, larval stage and larval weight were recorded at necropsy. No significant effect of immunization on LE (C = 28.9%; I = 31.0% P > 0.05) was observed. Antibody titers were higher in the immunized group on Day 28 (P < 0.05), but subsequently similar in both groups. Larval physiological age and weight were also significantly (P < 0.05) affected by immunization. Immunization of Pelibuey lambs with GMPE did not affect LE but did delay O. ovis larval development.
[Show abstract][Hide abstract] ABSTRACT: Mast cells and eosinophils are known to participate in the processes of al-lergic inflammation and gastrointestinal parasitic diseases. Sodium cromo-glycate (SCG), a non steroid anti-allergic drug is used in the prophylaxis and treatment of asthma and GIT allergic disorders in human. This experimental study has used SCG to reduce the population and degranulation of mast cells and the subsequent mobilisation of eosinophils during Haemonchus contor-tus infection, in an attempt to rendering the relatively nematode resistant Black Belly breed of sheep more prone to the infection. Animals were divi-ded in to three groups of 5 sheep (groups SH, H and C: SCG treated and in-fected, non-treated and infected and negative control respectively). Blood and bone marrow eosinophil counts, faecal egg count (FEC), tissue eosino-phil, mast cell and globule leukocyte counts as well as measurement of other parasitological parameters were performed. Oral administration of SCG for 5 consecutive weeks successfully reduced the level of blood and bone mar-row eosinophil number but not tissue eosinophil level. Furthermore, a signi-ficant reduction in mast cells, and a moderate reduction in globule leucocyte numbers were observed in the abomasal mucosa. Mean values for FEC and worm counts were higher in group SH. However, there was no significant difference between SCG-treated and non-treated group, which suggests the reduction in the inflammatory response alone, may not be sufficient enough to influence H. contortus development in sheep. As the dose and mode of administration of this drug is not fully established for sheep, further studies might be required to make SCG a useful tool for experimental studies during gastrointestinal parasitism. RÉSUMÉ Un traitement quotidien au cromoglycate de sodium diminue les ré-ponses mastocytaires et éosinophiliques sanguines chez des moutons de race Black Belly résistants à Haemonchus contortus . Mastocytes et éosinophiles sont des cellules impliquées dans les proces-sus allergiques et les maladies parasitaires du tube digestif. Le cromoglycate de sodium (CGS), une drogue non stéroïdienne, est utilisée dans la préven-tion et le traitement de l'asthme bronchique et des manifestations allergiques du tube digestif. Cette expérimentation a utilisé le CGS afin de réduire la po-pulation et la dégranulation des mastocytes muqueux mais également la mo-bilisation des éosinophiles durant une infestation par Haemonchus contortus chez des moutons de race Barbados Black Belly réputés résistants à ce para-site. 15 agneaux de cette race ont été répartis en trois groupes de 5 animaux : i) traités au CGS et infestés par H. contortus (SH), ii) non traités au CGS et infestés (H) et iii) témoins non traités et non infestés (C). Des comptages ré-guliers d'éosinophiles sanguins ont été réalisés de même que des comptages d'oeufs dans les matières fécales. Après l'autopsie, 30 jours après l'infesta-tion, une évaluation de la proportion d'éosinophiles dans la moelle osseuse, du nombre d'éosinophiles, de mastocytes et de leucocytes dans la muqueuse abomasale a été menée sur tous les animaux. L'administration quotidienne de CGS avant l'infestation puis durant toute la durée de l'infestation a réduit significativement l'éosinophilie sanguine et la proportion d'éosinophiles dans la moelle osseuse mais n'a pas eu d'effet sur le recrutement de ce type cellulaire dans la muqueuse abomasale. Une réduction significative du nom-bre de mastocytes et, dans une moindre mesure, de leucocytes est constatée chez les animaux du groupe SH. La diminution de réponse cellulaire dans ce dernier groupe ne s'est pourtant pas traduite par une installation significati-vement supérieure, un meilleur développement ou une plus grande fécondité des vers femelles même si des tendances apparaissent dans ce sens. Comme la posologie et le rythme d'administration du CGS ne sont pas complètement validés chez le mouton, d'autres expérimentations sont nécessaires pour fai-re du CGS un outil d'étude de la réponse cellulaire des ovins aux strongylo-ses gastro-intestinales.
[Show abstract][Hide abstract] ABSTRACT: Selection of resistant animals and host immunization have been proposed as alternative methods for the control of gastrointestinal nematode parasites. However, a better knowledge of the mechanisms involved in protective immunity against these parasites is required for the development of optimal strategies. In this study, 3 month old INRA 401 lambs (n = 81) were allocated into three groups: uninfected control, challenged either once (primary-infected animals) or twice (previously-infected animals) with 10,000 Haemonchus contortus L3. Uninfected control and challenged animals were sequentially sacrificed at 3, 7, 15 and 28 days post challenge. In both challenged groups, a clear Th2-oriented immune response was observed in the abomasal lymph node and mucosa. IL-4 and IL-13 mRNA over-expression, recruitment of eosinophils, mast cells and globule leukocytes and production of specific systemic IgG and mucosal IgA were observed earlier in previously-infected animals than in primary-infected ones. At 28 days post infection, no differences between intensities of these responses were observed between the challenged groups. Worm establishment rates were similar in previously-infected and primary-infected lambs. However, reductions of worm development, female fecundity and fecal egg output were observed in previously-infected sheep. We conclude that H. contortus infection in young INRA 401 lambs induced an unequivocal Th2 immune response resulting in the regulation of worm egg production without affecting their establishment.
Veterinary Research 07/2006; 37(4):607-22. DOI:10.1051/vetres:2006022 · 3.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Oestrosis is a nasal myiasis of sheep and goats caused by larvae of the fly Oestrus ovis and can lead to severe clinical signs, which together with the disturbance caused by the adult fly may result into serious economic losses. Infection rates and larval burdens are always higher in sheep than in goats after either natural or artificial infestation. The aim of this study was to compare the host preference of the adult fly O. ovis between sheep and goats in mixed flocks, where they are kept together under the same husbandry conditions and hence, are very similarly exposed to the fly preference. Blood sera samples were collected from a total of 397 sheep and 335 goats, from 43 mixed flocks located at different regions of Greece. Antibodies specific to O. ovis IgG were measured by ELISA. A flock was considered positive when at least one individual was positive, i.e. showed a seropositivity of >or=20% in relation to positive control sera. A total of 193 (48.6%) sheep and 58 (17.9%) goats were found to be seropositive against O. ovis. Thirty-eight (88.4%) out of 43 flocks had at least one seropositive animal. The mean seroconversion against O. ovis in animals from the different flocks was 38.6% and 13.6% for sheep and goats, respectively, whereas the variance of infection within each flock was 0-100%. The mean seropositivity between sheep that were found to be positive or negative was 60.6% and 5.4%, respectively, whereas the corresponding values between goats were 35.2% and 5.2%, respectively. No significant difference in the seroconversion values was noted between flocks from the different areas (P=0.817), whereas a very significant difference was observed between animal species (P=0.001). However, there was no significant difference when seroconversion comparisons were made within samples of the same animals species, sheep or goats from different flocks of all the regions included in the study (P=0.695). The results of this study clearly demonstrate that O. ovis has a widespread distribution in Greece, and the seroprevalence is significantly higher in sheep than goats (P=0.001).
[Show abstract][Hide abstract] ABSTRACT: The anthelmintic properties of tanniferous plants and of their secondary metabolites represent one possible alternative to chemotherapy that is currently being explored as a means of achieving sustainable control of gastrointestinal nematodes in ruminants. Previous in vivo and in vitro results suggest that tanniferous plants can have direct anti-parasitic effect against different stages of nematodes. However, the mode of action of the bioactive plant compounds remains obscure. The objectives of the current study were (1) to examine the hypothesis that extracts of tanniferous plants might interfere with the exsheathment of third-stage infective larvae (L3); (2) to assess the role of tannins in the process by examining the consequence of adding an inhibitor of tannins (polyethylene glycol: PEG) to extracts. The effects of 4 tanniferous plant extracts on exsheathment have been examined on L3 of Haemonchus contortus and Trichostrongylus colubriformis. Artificial exsheathment was induced in vitro by adding hypochloride solution to larval suspension. The evolution of exsheathment with time was measured by repeated observations at 10-min interval for 60 min. The selected plants were: genista (Sarothamnus scoparius), heather (Erica erigena), pine tree (Pinus sylvestris), and chestnut tree (Castanea sativa), with tannin contents ranging from 1.5 to 24.7% of DM. Extracts of a non-tanniferous plant (rye grass, tannin content: 0.3% of DM) were included in the assay as negative controls. The extracts were tested at the concentration of 600 microg/ml and the effects were compared to the rate of exsheathment of control larvae in PBS. No statistical differences in the pattern of exsheathment was observed after addition of rye grass or genista extracts for both nematode species and with heather extracts for T. colubriformis. In contrast, pine tree extracts on larvae of both species and heather extracts with H. contortus induced a significant delay in exsheathment. Last, contact with chest nut extracts led to a total inhibition of the process for both nematodes. These results suggest that extracts of tanniferous plants might affect a key process in the very early stages of larval invasion of the host. In most cases, the addition of PEG led to a total or partial restoration towards control values. This suggests that tannins are largely involved in the inhibitory process. However, other secondary metabolites may also interfere with the process that would help to explain some of the differences in response observed between the two nematode species.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this experiment was to determine if an earlier infection with Oestrus ovis would down regulate an infection with Trichostrongylus colubriformis when the larvae of O. ovis were expelled from the nasal cavities of sheep by a specific treatment. Three groups of five lambs were used: group 1 was artificially infected with O. ovis larvae and later with T. colubriformis, group 2 received O. ovis larvae and later was treated with ivermectin 14 days before being infected with T. colubriformis. Group 3 was infected with T. colubriformis only. The criteria examined were: the effects on nematode egg excretion, worm fecundity, nematode burdens and the kinetics of blood eosinophils. Significant decreases of nematode egg excretion, worm fecundity, nematode burdens were observed in group 1 compared to group 3. However, no changes were observed in either group 2 or 3. In group 2 it was noted that antiparasitic treatment induced a rapid decrease in blood eosinophils to a range close to the non-infected control group and this was associated with the removal of the down regulation effects of nematode burdens. This experiment showed that there is no cross immunity between O. ovis and T. colubriformis and that eosinophils may act against any parasite without specific priming.
[Show abstract][Hide abstract] ABSTRACT: Resistance to anthelmintics in populations of gastrointestinal nematodes is a major concern in small ruminants. One solution
to limit the spread of anthelmintic resistance is to apply treatments selectively by targeting the most susceptible animals within
a flock. In dairy goats, previous studies have shown that, within a flock, goats in first lactation and those with high level of milk
production were highly receptive to nematode infections. These results provided the rationale for targeted treatments. In dairy
ewes, such epidemiological information on possible factors modulating the susceptibility to parasitism were still lacking. The
objective of the current study was therefore to examine differences in the level of parasite infection and in the pathophysiological
consequences in dairy ewes, depending on the age or on the level of milk production. In three farms, parasite egg excretion, and the
serum concentrations of pepsinogen and inorganic phosphate were compared on one hand between primiparous and multiparous
ewes; on the other hand, between ewes with the highest and the lowest level of milk production, within a cohort of 3–5-year
old animals. Overall, the results did not indicate significant differences for both either the parasitological or pathophysiological
measurements depending on the level of milk production. In contrast, significant differences were found according to age,
indicating higher levels of infections in the primiparous ewes than in the multiparous ones and suggesting that this category of
animals represents a particular parasitic risk within a flock.
Small Ruminant Research 05/2006; DOI:10.1016/j.smallrumres.2005.02.025 · 1.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The effects of tannins on adult populations of Haemonchus contortus, Trichostrongylus colubriformis and Teladorsagia circumcincta in goats are characterised mainly by a decrease in egg excretion without any significant changes in worm number. In contrast, the impact of tannins on T. colubriformis or T. circumcincta third-stage larvae (L3) is associated with a significant reduction in worm establishment. The objective of the present study was to examine the effects of quebracho extract tannins on H. contortus L3. The consequences of consumption of sainfoin hay were also examined. Twenty-one naïve kids were divided into three experimental groups. Group Q received quebracho extract and group S received sainfoin hay from days D3 to D5. Group C remained as an infected control group. All kids received 1500 L3 H. contortus on D0, D1 and D2. On D18, post-infection, the kids were slaughtered and the worm populations compared in the different groups. Compared to the control values, the worm counts decreased, respectively, by 33% and 38% in groups Q and S but the differences were not significant. No differences were found in pathophysiological measurements between the three groups. The results confirm differences in tannin effect according to nematode species but not parasitic stage.
The Veterinary Journal 10/2005; 170(2):260-3. DOI:10.1016/j.tvjl.2004.05.001 · 2.17 Impact Factor