Colubriformis Infective Larvae Research Articles

Computed tomography revealed that bone density in lambs was affected by Trichostrongylus colubriformis infection

In this study we aimed to analyze computed tomography images of bony density in lambs submitted to infection induced by Trichostrongylus colubriformis. The lambs were randomly assigned to two experimental treatments: infected group (I) (n = 9) and control group (C) (n = 9). The lambs of group I were orally infected with 5000 T. colubriformis infective larvae (L3), three times per week during three weeks, totaling 45,000 L3. On the other hand, the lambs of group C remained uninfected. Each lamb was scanned 2x, the first scanning before the initial infection and the 2nd in the final of experimental period, with an interval of 90 days between measurements. For the analyses, the regions of the 4th and 12th ribs and thigh (femur) were selected, on the right side of the animal. The results showed that T. colubriformis infection reduced the bone density of growing lambs in the 4th rib (P = 0.0005), 12th rib region (P = <0.0001) and femur (P = 0.0063). Also, infected lambs had their bone density (4th rib, 12th rib and femur) reduced over time. We concluded that bone density in lambs was affected by Trichostrongylus colubriformis infection.

Pharmacokinetics and anthelmintic efficacy of injectable eprinomectin in goats

The objective of this study was to assess the pharmacokinetics and the anthelmintic efficacy of eprinomectin (Eprecis® 20mg/mL) following subcutaneous administration to goats. Forty non-lactating female Alpine goats aged between one and three years and weighing between 32.7 and 59.5kg, were randomly allocated to one of the following groups (8 animals per group): two groups were not infected and were treated at a dose of either 0.2 or 0.4mg/kg BW of eprinomectin, two groups were experimentally infected with nematodes and treated at 0.2 or 0.4mg/kg BW of eprinomectin similarly and one group was infected and left untreated (control). Infection consisted in a single and simultaneous administration of 5000 Haemonchus contortus and 12,500 Trichostrongylus colubriformis infective larvae. No local or general adverse reaction was visually observed whatever the dose rate. The maximal plasma concentrations (Cmax) were 20.68±12.85 vs 39.79±17.25μg/L and the plasma bioavailabilities (AUC) 83.45±34.75 vs 169.37±43.44μg*d/L for 0.2 vs 0.4mg/kg respectively. The efficacy against H. contortus and T. colubriformis was 97.8 and 98.7% at 0.2mg/kg and 98.4% and >99.9% at 0.4mg/kg respectively. The differences in worm burdens between the two dose rates were only significant for T. colubriformis. These results indicate that injectable eprinomectin is a potent anthelmintic against the two major gastrointestinal nematodes in goats. Additional information is needed regarding pharmacokinetics in lactating goats and milk residues.

Sustainable worm control practices in South America

A high prevalence of nematodes, especially Haemonchus contortus and Trichostrongylus colubriformis, that exhibit multiple anthelmintics resistance has been reported in sheep in several South American countries. For this reason, the development of strategies that are less dependent on anthelmintic treatments is imperative for the prophylaxis of gastrointestinal nematode infections in small ruminants. Integrated grazing using cattle and sheep can be used for pasture decontamination with considerable reduction of H. contortus and T. colubriformis infective larvae after cattle grazing. Several breeds of sheep exhibit genetically related resistance against nematode infections, as is the case of “crioulo”, “native” or naturalised breeds of sheep. These breeds descend from livestock introduced by Portuguese and Spanish settlers and have been submitted to a long process of natural selection in various environmental conditions. In the South, the Crioula Lanada breed is more resistant to H. contortus than are Corriedale sheep. In tropical areas, where the minimum temperatures are usually higher than 20°C, hair sheep flourish, especially the Santa Ines breed, which also display a higher level of resistance to nematode infections compared with certain breeds of European origin. However, Santa Ines sheep have inferior carcass quality compared with other commercial breeds. Recent studies showed that the crossbreeding of Santa Ines ewes with sires of breeds with high potential for growth and meat production, results in crossbred animals with high productivity and a satisfactory degree of resistance against nematode infections. Several studies have indicated that improvement in nutrition has a beneficial effect on the development of resistance in lambs that were naturally or artificially infected with nematodes. Therefore, supplementary feeding and breeding strategies to improve resistance to nematodes are feasible options in the effort to reduce dependence on anthelmintic drugs to control worm infections in sheep.

Development of a new monoclonal antibody to ovine chimeric IgE and its detection of systemic and local IgE antibody responses to the intestinal nematode Trichostrongylus colubriformis.

The J558L cell line, previously transfected with the ovine Cepsilon gene, was induced to secrete a chimeric IgE protein composed of the ovine heavy chain and a mouse light chain with MW of approximately 80 and 26 kDa, respectively. After purification, the chimeric protein was used to immunise BALB-c mice and monoclonal antibodies (mAbs) were generated. The mAb 2F1, which had greatest anti-IgE activity in preliminary screens, was chosen for further characterisation and an examination of systemic and local IgE responses to the intestinal nematode, Trichostrongylus colubriformis. The chimeric IgE protein was not recognised in enzyme linked immunosorbent assay (ELISA) by mAbs raised against ovine IgG1, IgG2, IgA or IgM. However, 2F1 was highly specific to the chimeric IgE protein, and did not cross-react with ovine IgG1, IgG2 or IgA. Western blot analysis also showed that 2F1 and secretory IgA (sIgA) did not cross-react, and that 2F1 and the anti-IgA mAb identified different MW bands from colostrum (approximately 200 and 400 kDa, respectively). 2F1 bound to mucosal mast cells (MMC) isolated from the intestines of lambs infected with T. colubriformis, but cultured bone marrow-derived mast cells (BMMC) required prior incubation with the chimeric IgE protein for this binding to occur. Distinctive staining of plasma cells and putative mast cells were observed using 2F1 on immunohistological sections of mesenteric lymph node and jejunum.ELISA incorporating 2F1 was able to detect >0.4 ng chimeric protein. Total IgE in ovine colostrum and intestinal homogenates was quantified using a capture ELISA, with known amounts of chimeric protein used to produce a standard curve. Colostrum from outbred Merino ewes had 0.55-11.05 ng ml(-1) total IgE, and their lambs, at necropsy after infection with a total of 18,000 T. colubriformis infective larvae over a 9-week period, had 45-620 ng g(-1) total IgE in intestinal tissue. Compared to genetically susceptible lambs, antigen-specific levels of IgE were significantly higher in genetically resistant lambs after infection with 4500 T. colubriformis infective larvae (TcL3) per week for 9 weeks (161.4 versus 44.8 geometric mean titres; P=0.043). In western blots, distinctive bands (19-21 and 27 kDa) from T. colubriformis larval antigen were differentially recognised by IgE, as identified by 2F1, in intestinal homogenates from genetically resistant animals. These results have demonstrated the value of 2F1 for quantification of IgE responses in samples derived from ovine fluids and tissues using ELISA, western blots and immunohistology. In this respect, it recognises native ovine IgE and does not require pre-treatment of the sample with denaturing agents or ammonium sulphate.

Cysteine may play a role in the immune response to internal parasites in sheep

To investigate the potential role of cysteine in the increased parasite susceptibility of sheep selected for increased wool production, ten 2-year-old rams from both fleece-weight-selected (FW) and randomly selected (C) Romney lines received either 2 g of supplemental cysteine per day (+CYS) or saline (+SAL), via abomasal infusion. Following drenching to remove any pre-existing parasites, all sheep were dosed with Haemonchus contortus and Trichostrongylus colubriformis infective larvae. Sheep were also subjected to non-parasitic immune challenges: inoculation with ovalbumin and a commercial clostridial vaccine containing the tetanus toxin. Cysteine infusion elevated plasma cysteine concentrations by an average of 65% (P &lt; 0.0001), but no difference in cysteine levels was observed between selection lines. Off-pasture faecal egg counts (FEC) were higher in FW sheep (645 v. 200 eggs/g, P &lt; 0.01). FEC were unaffected by selection line or infusion treatment following experimental infection, although FEC of +SAL sheep were at least double those of +CYS sheep. Total parasite numbers in the abomasum and small intestine at slaughter were unaffected by selection line or infusion treatment. Cysteine infusion tended to result in greater peripheral eosinophilia over the experimental period (P &lt; 0.10), and higher counts of globular leukocytes in the abomasum at slaughter (P &lt; 0.05). Anti-parasite antibody responses showed no response to experimental infection, tending to drop over time; previous parasitic infection may have confounded results. There were no effects of selection line or infusion treatment on IgG responses to tetanus toxin, although data suggested that a swifter response occurred in +CYS sheep. Anti-ovalbumin IgG responses tended to be greater in +CYS sheep (Day 52, P &lt; 0.10). This study supports the greater susceptibility of FW sheep in natural parasitic challenge, as indicated by off-pasture FEC. Cysteine appears to influence certain aspects of immunocompetency in sheep, although the exact role of cysteine in the relationship between wool production and parasite susceptibility requires further elucidation.

Serum IgE responses during primary and challenge infections of sheep with Trichostrongylus colubriformis

Serum IgE responses during primary or challenge infections with Trichostrongylus colubriformis were examined by measuring total IgE and parasite-specific IgE by ELISA. Three- to four-month-old lambs reared nematode-free received a single primary infection of 30 000 T. colubriformis-infective larvae (TcL3). Infections were terminated after 100 days by anthelmintic treatment, at which time faecal egg counts had fallen to low levels. Total serum IgE increased slowly from 20 days p.i. until anthelmintic treatment. The specific IgE response to T. colubriformis adult antigen peaked at 20–27 days p.i. before returning to near baseline levels. A further slight increase occurred between 56 and 100 days p.i. The animals were then divided equally into two groups. A first series of challenge infections consisting of either weekly 10 000 TcL3 infections (Group A) or a single 30 000 TcL3 infection (Group B) produced low faecal egg counts. Total and specific IgE to adult and L3-ES antigens increased rapidly over a 21-day period, then remained elevated irrespective of challenge regime. Termination of primary and the first challenge infections with anthelmintic resulted in a rapid decline in serum IgE responses but not other T. colubriformis-specific Ig responses. A second series of challenge infections consisting of repeated 10 000 (Group A) or 20 000 TcL3 infections (Group B) resulted in all IgE responses peaking within 7–8 days p.i. Marked softening of faeces coincided with peaks of specific and total IgE responses during challenge infections. The results of this study showed that infection of sheep with T. colubriformis leads to elevated levels of total and parasite-specific IgE in serum. IgE responses following challenge suggest involvement of this antibody isotype in protection from T. colubriformis infections.

Serum mast cell proteinase responses of sheep to challenge with Trichostrongylus colubriformis and the effect of dexamethasone treatment

Eight-month-old random bred Romney wethered lambs were reared nematode-free in pens and assigned to 4 groups of 5 lambs. Lambs in 2 groups were dosed orally, twice a week, with 5000 Trichostrongylus colubriformis infective larvae (L3) for the duration of the experiment. These 2 groups were treated weekly with dexamethasone (0.5mg kg −1 body-weight), one between days −7 and 70, the other between days 77 and 147. A third group was dosed with L3 until anthelmintic treatment on day 133. A fourth group remained uninfected throughout and served as a control group. Nematode eggs in sheep faeces (FEC) were monitored at weekly intervals. Serum samples were taken twice a week and assayed for sheep mast cell proteinase (SMCP). Serum levels of SMCP in uninfected control sheep were 459 ± 190 pg ml −1. Twenty-eight days after nematode dosing commenced, SMCP levels were significantly above control sheep levels and after 49 days reached a plateau level of 1154±364 pg ml −1. The SMCP response persisted even after cessation of dosing, and SMCP levels remained significantly above control levels to the end of the experiment (day 213). Dexamethasone treatment prevented elevation of SMCP and resulted in a rapid reduction of extant SMCP levels in resistant sheep. Overall, serum levels of SMCP were significantly correlated ( P < 0.001) with specific anti- T. colubriformis L3 antibody in serum ( r = 0.601, d.f. = 78), blood eosinophils ( r = 0.609, d.f. = 78) and log(FEC+15) ( r = −0.521, d.f. = 78). These results show that serum levels of SMCP correlate with other indicators of parasitism and may have potential use as a non-invasive indicator of gastro-intestinal mast cell responses to nematode infection.

The persistence of the efficacy of injectable or oral moxidectin against Teladorsagia, Haemonchus and Trichostrongylus species in experimentally infected sheep

The persistence of the efficacy of moxidectin was evaluated against experimental gastrointestinal nematode infections in 55 lambs randomly allocated to 11 equal groups and infected on day 0. Moxidectin 1 per cent injectable solution was administered at a dose rate of 0.2 mg moxidectin/kg bodyweight to five of the groups on days -42, -35, -28, -21 and -14; five other groups were treated with moxidectin 0.1 per cent oral drench at the same dose rate on days -35, -28, -21, -14 and -7, and the 11th group remained untreated as a control. The lambs were infected experimentally with 8000 Teladorsagia circumcincta, 2000 Haemonchus contortus and 10,000 Trichostrongylus colubriformis infective larvae and killed three weeks later. Both formulations of moxidectin showed excellent activity against T circumcincta and H contortus with almost 100 per cent efficacy against the abomasal parasites for up to 35 days after treatment. The efficacy of moxidectin 1 per cent injectable against T colubriformis was much higher (> 99 per cent) than that of the oral drench and it was highly effective up to 21 days after treatment, and gave a moderate reduction in worm burden for up to 35 days after treatment. No adverse reactions to moxidectin were observed in any of the animals.

Growth and gastrointestinal nematode parasitism in lambs grazing either lucerne (Medicago sativa) or sulla (Hedysarum coronarium) which contains condensed tannins

SUMMARYTwo grazing experiments were undertaken to evaluate the effects of sulla (Hedysarum coronarium) which contains condensed tannins (CT) and lucerne (Medicago sativa), which does not contain CT, on the performance of parasitized and non-parasitized lambs. The work was carried out near Palmerston North, New Zealand in 1992 and 1993.Experiment 1 used lambs which were either genetically ‘conventional’ or ‘resistant’ to gastrointestinal nematodes and which had a naturally acquired heavy parasite burden (faecal egg count (FEC) 1300–2500 eggs per gram faeces (epg)). They were either drenched to remove all the parasites or remained undrenched when allocated to pure swards of either sulla or lucerne for the 28-day experimental period. Liveweight gains of drenched lambs were higher with sulla (mean 302 g/day) than with lucerne (mean 245 g/day; P &lt; 0·02) and rates of gain were not reduced (P = 0·10) by genetic resistance to nematodes. Undrenched lambs had mean faecal egg counts of 1090–2220 epg after 28 days, with higher counts in lambs grazing lucerne than in those grazing sulla (P &lt; 0·05). Lambs grazing lucerne also had a much lower average daily gain (ADG) (mean 50 g/day) than those grazing sulla (mean 206 g/day; P &lt; 0·0001). Resistant lambs had reduced (P = 0·07) ADG in the sulla treatment only.In Expt 2, lambs with a relatively low worm burden (average FEC 250 epg) were either drenched to remove all worms or dosed with 20 000 Trichostrongylus colubriformis infective larvae and grazed on pure sulla or lucerne swards for 42 days. Drenched lambs had a similar liveweight gain (mean 190 g/day) and wool growth when grazing either sulla or lucerne. Undrenched lambs grazing sulla had a greater ADG (mean 129 g/day) than those grazing lucerne (mean −39 g/day; P &lt; 0·0001) and a higher rate of wool growth from mid-side patches (P &lt; 0·009) and larger wool fibre diameter (P &lt; 0·05) than those grazing lucerne. Undrenched lambs grazing sulla had lower FECs (P &lt; 0·05) on days 14, 21, 35 and 42 than those grazing lucerne and lower (P &lt; 0·05) Trichostrongylus colubriformis worm burdens at slaughter. Undrenched lambs had less perineal faecal contamination when grazing sulla rather than lucerne. Parasite-induced anorexia was evident in the lambs grazing lucerne but not in those grazing sulla.These findings demonstrate that the performance of lambs infected with nematode parasites can vary substantially when given feeds of a similar chemical composition. The superior performance of lambs grazing sulla was probably caused by condensed tannins, which decrease protein degradation in the rumen and can increase post-ruminal protein availability.

Antibody responses of sheep to challenge with Trichostrongylus colubriformis and the effect of dexamethasone treatmen

Eight-month-old random bred Romney wether lambs were reared nematode-free in pens and assigned to 4 groups each of 5 lambs. Lambs in 3 groups were infected orally, twice a week, with 5000 Trichostrongylus colubriformis infective larvae (L3), a control group remained uninfected throughout. Two infected groups were treated with dexamethasone (0.5 mg kg −1bodyweight), one between days — 7 and 77, the other between days 77–154. Nematode challenge infection was withheld from the third group from day 133 after anthelmintic treatment. Nematode eggs in sheep faeces (FEC) were monitored at weekly intervals. T. colubriformis-specific antibody levels were determined twice a week and specific immunoglobulin isotypes (IgA, IgG,, IgGi and IgM) determined weekly in serum samples using ELISA. Resistance, as measured by FEC, was expressed by 35 days after L3 infection began but sheep dosed with dexamethasone did not develop resistance. Extant resistance was abrogated in sheep dosed with dexamethasone. Nematode challenge resulted in elevated serum levels of antibodies to T. colubriformis L3 excretory/secretory antigens, these consisted predominantly of IgG 1 and IgM. The IgG 1 response was more persistent than the IgM response. Specific serum IgA and IgG, responses were low, but significant, in nematode-challenged sheep. Dexamethasone treatment prevented the antibody responses and resulted in a rapid reduction of extant antibody levels in resistant sheep. Weight gain was reduced by nematode challenge with or without dexamethasone treatment compared with control sheep.

Changes in inflammatory mediators and larval inhibitory activity in intestinal contents and mucus during primary and challenge infections of sheep with Trichostrongylus colubriformis

Helminthologically naive merino sheep were given either a single infection of 30,000 or a trickle infection of 6000 Trichostrongylus colubriformis infective larvae (TcL3) per week. Faecal egg counts started to fall after 8 weeks in the single infection and after 11 weeks in the trickle infection. Small intestinal contents were collected from indwelling intestinal fistulae over the next 14 weeks. Concentrations of sheep mast cell protease (SMCP) in these contents increased to highest levels 9–11 weeks and 6–10 weeks after the single infection and from the start of the trickle infection, respectively. Similarly, peptidyl leukotriene (PLT) concentrations were highest at 6 weeks and at 6–9 and 13 weeks, respectively. Histamine concentrations increased slightly after both infections to peak values at 7 weeks and 9 weeks, respectively. Inhibition of migration of larvae in vitro was increased in contents sampled at 8 weeks after the single infection and after 6–10 weeks of the trickle infection. Another 2 groups of sheep were immunised by repeated infections with TcL3. Gut contents from 1 group sampled immediately before and after challenge with 30,000 TcL3 at 0 and 18 days had increased levels of larval migration inhibitory (LMI) activity throughout the 35 day period, especially 7–14 days after challenge (DAC). The mediators SMCP increased significantly 5–7 DAC while PLT increased 7–14 DAC. In the second group of immunised sheep, levels of SMCP and PLT increased rapidly within 1 DAC and further increased 3–14 DAC. Increased concentrations of platelet activating factor PAF occurred only at 14 DAC, while LMI activity was greatest in mucus collected 5–8 DAC. Since increased concentrations of these mediators occurred around the time when egg counts started to decline in primary infections and were increased after challenge of immune sheep, the results suggest roles for the mediators and/or their cellular source in the expression of immunity.

The effects of immunization of sheep with Trichostrongylus colubriformis larvae on worm burdens acquired during grazing

The effects of immunization of sheep with Trichostrongylus colubriformis larvae on worm burdens acquired during grazing. International Journal for Parasitology 19: 177–181. Romney sheep, reared helminth-free in pens to 5 months of age, were immunized against Trichostrongylus colubriformis by giving two doses of 200,000 T. colubriformis infective larvae at 15 day intervals to assess protection from natural challenge during grazing. Five immunized sheep and five unimmunized sheep were grazed on infested pasture for 4 weeks, and were then returned to the pens for 4 weeks before slaughter. Worm burdens, gastrointestinal histology and mucus antiparasite activity were examined at slaughter. Faecal egg counts and haematological examinations were carried out at regular intervals throughout the trial. Significant protection ( P < 0.05) was afforded immunized sheep against adult T. colubriformis (87%), T. axei (67%), Nematodirus spathiger (91%) and Osteragia spp. (42%). Greater numbers of immature Nematodirus spp. and Ostenagia spp. were present in immunized sheep ( P < 0.05). Overall, a significant ( P < 0.05) 42% reduction in total nematode burdens was afforded by immunization of the sheep with T. colubriformis larvae. Immunized sheep had significantly ( P < 0.05) more globule leukocytes, mast cells and eosinophils in gastrointestinal tissue and significantly ( P < 0.05) higher levels of mucous antiparasite activity than unimmunized sheep. Haematological observations showed some sheep had transient eosinophilia during immunization or grazing. Both immunized and unimmunized sheep showed depressed ( P < 0.05) total leukocyte counts during grazing which returned to pre-grazing levels within 1 week of return of the sheep to the pens. Overall, haematological parameters reflected parasite challenge and were unrelated to worm burdens acquired.

Local and systemic antibody responses in gerbils following vaccination with irradiated or non-irradiated Trichostrongylus colubriformis larvae.

Groups of 10 Mongolian gerbils, Meriones unguiculatus, were vaccinated with 1,500 gamma-irradiated Trichostrongylus colubriformis infective larvae (L3) or with non-irradiated larvae. 25 days later five gerbils from each group were necropsied and the remaining gerbils challenged with 1,500 non-irradiated T. colubriformis infective larvae. Systemic, local intestinal and coproantibody levels were compared in each group of gerbils 25 days after vaccination and 26 days after challenge. Strong local intestinal and faecal antibody responses were detected. Coproantibodies reflected antibody levels in the intestinal contents and in mucosal extracts. The results gave further support to the view that coproantibody measurements provide a sensitive index of immunity at mucosal surfaces to intestinal parasites.

Studies on the kinetics of expulsion by guinea-pigs of primary infections with the intestinal nematode parasite Trichostrongylus colubriformis

Heston strain guinea-pigs were infected with 1000 Trichostrongylus colubriformis infective larvae and the kinetics of parasite expulsion from the host studied. Expulsion began approximately 15 days after infection, after which log worm count declined from an initial level of approximately 2·77 at a rate of approximately 0·1 per day. There was no significant difference in worm counts in each sex.

Responses to infection with Haemonchus contortus and Trichostrongylus colubriformis in ewes of different reproductive status

Groups of ewes which were either lactating, pregnant, non-lactating (lambs removed at birth) or unmated were subjected to twice weekly infection with constant numbers of H. contortus and T. colubriformis infective larvae for 8 weeks. From the size, structure and fecundity of their worm burdens, lactating ewes, and those in late pregnancy did not differ from each other and showed evidence of diminished immunological responses to infection compared with unmated ewes. The worm burdens of non-lactating ewes, slaughtered less than 30 days after parturition, resembled those of lactating and pregnant animals, but substantially fewer T. colubriformis were found in two ewes which had been deprived of their lambs for 33 and 40 days respectively. Increased numbers of mast cells, eosinophils and globule leucocytes were found in the gut mucosa of animals showing parasitological evidence of an immune response, and in particular, very few globule leucocytes were present in lactating and pregnant animals. Within animals over all groups there was a pronounced negative correlation between numbers of T. colubriformis and numbers of globule leucocytes in the small intestine.