Trichostrongylus colubriformis infection damages intestine brush board cells and could negatively impact postabsorptive parameters of Santa Ines lambs.

This study aimed to evaluate histological, digestive and postabsorptive physiological parameters in Santa Ines lambs infected with Trichostrongylus colubriformis and fed different levels of phosphorus. Therefore, eighteen Santa Ines, castrated male, six-month old, healthy lambs (initial body weight 22.4 ± 2.7 kg) were distributed in one of four treatments arranged in a 2 × 2 split-plot arrangement: Sufficient dietary P level and uninfected (SPui; n = 4), Sufficient dietary P level and infected (SPi; n = 5), Deficient dietary P level and uninfected (DPui; n = 4), Deficient dietary P level and infected (DPi; n = 5). Infected lambs received, orally, a single pulse dose of 40.000 T. colubriformis infective larval stage (L3). Animals were fed Tifton 85 hay (Cynodon ssp.; 60%), and cassava meal and maize gluten meal (40%). Measurement of nutrient apparent digestibility and nitrogen metabolism were performed in individual metabolic stalls. To achieve the trial results, it was measured methane emissions in respiratory chambers, urine purine derivatives, ruminal short-chain fatty acids (SCFA), histological cuts of duodenal mucosal tissues and passage rates fluxes, analyzed by external (Yb, Cr, and Co) and internal (iNDF) markers. Statistical procedures were performed in R studio. The fixed main effects of treatment and the interactions were tested by ANOVA, and means compared by Duncan's test at 5% significance. Apparent digestibility was not affected by treatments, however, nitrogen retained decreased (P < 0.01) and urinary nitrogen losses increased (P < 0.01) in infected animals. Small intestine digesta content, empty segment weight, and length were higher in infected animals (P < 0.05). Passage rate was not majorly affected by infection or dietary P levels. Methane emissions, SCFA concentrations, and purine derivative excretion were also not affected by treatments. Regarding the histology, the vilosity weight (P < 0.05), and crypt depth (P < 0.01) decreased in infected animals. In conclusion, T. colubriformis infection can damage intestinal mucosa and affect nitrogen metabolism, but did not affect the digesta transit, and nutrient digestibility. The P dietary levels did not promote any modification in GIT physiological parameters tested in this study.

Phosphorus kinetics in lambs experimentally infected with Trichostrongylus colubriformis with the use of 32P.

This study was conducted to evaluate the metabolism and phosphorus (P) kinetics in lambs experimentally infected with Trichostrongylus colubriformis using the isotope dilution technique and modelling. Fifteen male lambs (21.1 ±â€¯1.50 kg) of the Santa Inês hair breed of approximately six months old, distributed in the treatments infected (I, n = 8) and control (C, n = 7) were used. The infected lambs received serial infections with 5000 T. colubriformis larvae, three times per week, for 3 weeks (45 000 T. colubriformis total larvae). After 66 days of the last inoculation of infective larvae, 6.6 MBq of 32P were injected in each lamb to evaluate the P kinetics. Blood, faeces and urine samples were collected in the following seven days and the slaughter of lambs were carried out on the last day in order to collect bone and soft tissues (Liver, kidney, heart and muscle) samples. To analyse P flows, the biomathematical model with four compartments (C1 - gastrointestinal tract, C2 - plasma, C3 - bone and C4 - soft tissue) was used. Similar P intake (VI) between treatments (C and I) was verified. Lower absorption of endogenous (Vaf) and dietary P (Vaa), as well as, lower amount of endogenous P (from saliva) that reaches the gastrointestinal tract (VIT), consequently, higher excretion of dietary P (VFD) were verified in infected lambs (P < 0.1). Additionally, in infected lambs, the P bioavailability was lower compared to control lambs. With the lower absorption (VaT) of P in infected lambs, there was, consequently, lower distribution to bones and soft tissues (VeD2) and lower P deposition in the bones (VO+D). It was concluded that P metabolism of lambs infected with T. colubriformis was altered, with reduced intestinal absorption and bioavailability, increased faecal loss and reduced P flow to the bone.

Nutritional sensitivity of resistance to Trichostrongylus colubriformis in lactating ewes.

It has been suggested that the periparturient breakdown of immunity to parasites has a nutritional basis. Our overall hypothesis is that it results from a prioritized scarce metabolizable protein (MP) allocation to reproductive functions (e.g. milk production) rather than to immune functions. We have earlier shown that the relationship between MP supply, milk production and resistance to the abomasal nematode Teladorsagia circumcincta provides support for this hypothesis. Because nutritional sensitivity of resistance to parasites may differ between parasite species, we used the same nutritional protocol to test the overall hypothesis with a different parasite. Thus, five levels of dietary MP, ranging from 0.60 to 1.2 times assumed requirements, were offered for 4 weeks post-parturition to twin-rearing Greyface ewes, experimentally infected with the small intestinal nematode Trichostrongylus colubriformis. We hypothesized that the initial increments of MP supply would increase milk production without affecting the degree of breakdown of immunity whilst later increments would reduce the degree of breakdown of immunity. Indeed, the data suggest that the first two increments of MP supply increased milk production, whilst final worm burdens were reduced from the second increment onwards. MP supply did not affect mucosal mast cell concentration but increased globule leukocyte concentration. These results support the overall hypothesis that scarce MP allocation is prioritized to milk production over immune functions. In addition, the contrast between effects of MP supply on resistance to T. colubriformis and to T. circumcincta supports the view that periparturient immunity to small intestinal nematodes may be less sensitive to nutrient scarcity than periparturient immunity to abomasal nematodes.

Gastrointestinal nematode challenge induces some conserved gene expression changes in the gut mucosa of genetically resistant sheep.

Sheep have a varying ability to resist infection with gastrointestinal nematodes. This ability is due in part to genetic differences that exist between individuals. In order to define these differences we have used real-time PCR to quantify gene expression responses in the gut mucosal surface of genetically resistant and susceptible sheep, following a nematode challenge. Expression profiles were determined in response to two different nematode species, Haemonchus contortus and Trichostrongylus colubriformis, and in divergent sheep originating from two different genetic backgrounds. Results show that the response generated differs between resistant and susceptible animals and is further impacted by the origin of the sheep and nematode species used for challenge. However, some conserved features of a response mounted by a resistant or a susceptible animal were identified. Genes found to be more abundantly expressed in resistant animals include markers of an early inflammatory response, several Toll-like receptors (TLR2, 4, 9) and free radical producing genes (DUOX1 and NOS2A). Conversely, genes differentiating susceptible animals indicate a prolonged response and development of a chronic inflammatory state, characterised by elevated expression of members of the NF-kappabeta signalling pathway (IKBKB and NFKBIA) together with delayed expression of regulatory markers such as IL2RA (CD25), IL10 and TGFbeta2. While multiple nematode response pathways were identified, the identification of conserved aspects of the response which associate with resistance provides evidence that alternative nematode control strategies, such as breeding for resistant animals, may be feasible.

Influence of the route of administration on efficacy and tissue distribution of ivermectin in goat.

The tissue concentration and efficacy of ivermectin after per os and subcutaneous administration were compared in goats experimentally infected with Trichostrongylus colubriformis (ivermectin-susceptible strain, INRA). Infected goats (n = 24) were treated per os (n = 9) or subcutaneously (n = 9) with ivermectin, 0.2 mg/kg, or kept as not treated controls. The faecal egg counts and small intestine worm counts were determined. Ivermectin concentration was measured in the plasma, gastrointestinal tract, lung, skin or hair, liver and adipose tissues at 0, 2, 7 and 17 days post-treatment. The efficacy of ivermectin against T. colubriformis infection in goat was 98.7 and 99.9% for subcutaneous and oral administration, respectively. Ivermectin concentration declined with time and only residual concentration was measured at 17 days post-treatment in plasma and gastrointestinal tract. Ivermectin concentration was higher after subcutaneous compared to per os injection in most of the tissue examined. In skin, hair and subcutaneous adipose tissue ivermectin persisted at significant concentrations 17 days post-treatment for both routes of administration. In our experimental conditions, ivermectin provides similar efficacy against T. colubriformis after subcutaneous or per os administration in goat. However, the lower ivermectin levels in tissues after per os administration suggest that the lasting of efficacy may be shortened after per os compared to subcutaneous administration especially in animals with poor body condition in pasture where re-infection occurs quickly after anthelmintic treatment.

Demonstration of a range of inflammatory mediators released in trichostrongylosis of sheep.

The levels of inflammatory mediators in the intestinal contents of sheep immunized with Trichostrongylus colubriformis larvae increased in the first 6 days after challenge. These mediators were histamine, leukotriene C4, 6-keto-prostaglandin F1 alpha (from prostacyclin) and thromboxane B2. Leukotriene C4 was released in the greatest quantities. Leukotriene B4 was present but its concentration remained unchanged after challenge. The presence of these particular mediators in the intestinal contents after challenge is consistent with antigen-induced mediator release from the mucosal mast cells found in immune sheep undergoing challenge infection. This is the first sequential analysis of mediator release in sheep that also demonstrates the release of prostacyclin and thromboxane into the intestine during expulsion of a nematode infection.

The effect of reduced feed intake on the efficacy of oxfendazole against benzimidazole resistant Haemonchus contortus and Trichostrongylus colubriformis in sheep.

Within 12 h of reducing the daily intake of a 50:50 lucerne and wheaten hay ration from 800 to 400 g, there was an increase in digesta marker concentration indicating a reduction in the flow rate of digesta fluid and particulates through the abomasum of sheep. The efficacy of the recommended dose of oxfendazole (OFZ) was then tested against benzimidazole resistant Trichostrongylus colubriformis and Haemonchus contortus in sheep whose feed intake was halved 36 h before and after drug treatment. In animals fed the reduced ration there was a 60% reduction of T. colubriformis and 94% reduction of H. contortus compared with a 19% and 60% reduction respectively on the higher feed intake. It is therefore suggested that greater anthelmintic efficacy can be achieved in sheep by temporary feed reduction.

Interleukin-6 expression in gut of parasite challenged sheep.

Following challenge with Trichosirongylus colubrifonizis, increased numbers of T-cells and immunoglobulin responses are seen in the intestine of sheep immunised by repeated infection with live worms. IL-6 mRNA expression in the small intestine from T. colubriformis-immunised and naive sheep was determined by in situ hybridisation, whereas CD4(+), IgA(+), IgG(+) cells in the gut were evaluated by immunohistochemistry. There was constitutive expression of IL-6 mRNA by cells in the naive gut, and the number of these cells was increased by parasite challenge. There were corresponding increases in numbers of CD4(+) and TCR gamma/delta(+) T-cells and IgG(+) B-cells. Our data are consistent with a role for IL-6, perhaps produced by CD4(+) and/or TCR gamma/delta(+) T-cells or B-cells, in B-cell terminal differentiation. Infiltration of B-cells, particularly IgG(+) B-cells, may reflect parasite immunity in the host.

The effect of daily challenge with Trichostrongylus colubriformis larvae on the nutrition and performance of immunologically-resistant sheep.

Immunological resistance to Trichostrongylus colubriformis was developed in sheep by challenging them with 2500 larvae per day for 34 weeks. They were then rested for 24 weeks before being re-challenged with the same dose rate of the same larvae for 10 weeks. Nutritional, haematological and parasitological parameters were measured during the first 8 weeks of re-challenge infection. There were no faecal worm eggs excreted during the re-challenge infection. There was a small but significant increase in plasma-N leakage from Days 4 to 9 of dosing but this then declined to initial levels. There was no other detectable nutritional disturbance associated with re-infection. Re-challenge caused a rapid development of eosinophilia which peaked during Week 6 before declining to levels of the control animals by Week 8. Sheep resistant to T. colubriformis appear to be able to re-activate their immunological mechanisms when re-challenged with the parasite with little associated nutritional penalty.

Effect of prolonged subclinical infection with Trichostrongylus colubriformis on the performance and nitrogen metabolism of growing lambs.

Ten 5-month-old lambs, reared free of parasites and prepared with abomasal and ileal cannulas, were paired and given rations of pelleted dried grass by means of continuous feeders. From 7 months of age one of each pair was dosed daily with 2500 Trichostrongylus colubriformis larvae for 34 weeks. An untreated animal served as a pair-fed control to each infected lamb. During 5 experimental periods (pre-infection, and Weeks 6-8, 12-14, 18-20 and 29-34 of dosing) measurements were made of the amounts of N leaving the small intestine, the digestibility of 35[S]-labelled microbial protein in the small intestine, and the amounts of plasma protein leaking into the digestive tract. The infection caused a growth check (P less than 0.05) from Week 6 to approximately Week 13 of dosing. This resulted from inappetence, but also from a disruption in the N digestion and metabolism of the lambs. There was a marked eosinophilia at this time. Measurements of ileal flow rates during Weeks 6 and 12 indicated that significantly more N flowed to the terminal ileum of infected lambs during this period (Week 6, 3.1 g N day-1 P less than 0.05; Week 12, 5.0 g N day-1 P less than 0.001). Plasma N leakage into the intestine during Weeks 8 and 14 was higher in infected lambs (1.2 g N day-1 P less than 0.01 and 0.9 g N day-1 P less than 0.05, respectively) but the digestibility of 35[S]-labelled microbial protein was depressed below that of the controls during the later part of this period, i.e. during Week 13. Continued larval challenge beyond this point caused a less severe nutritional penalty. Voluntary feed intake increased and the animals started to gain weight. The amount of extra N flowing to the terminal ileum of infected lambs was less at Week 18 of dosing (3.5 g N day-1 P less than 0.01) than it had been at Week 12. Similarly, extra plasma N leakage into the tract of infected lambs was less during Week 20 (0.26 g N day-1) than during Week 14. There was however, still a detectable reduction in the coefficient of digestibility of 35S microbial protein in infected lambs during Week 19. By Weeks 29-34 the only detectable difference between the infected and control lambs was in their eosinophil counts.

Absorption and secretion of calcium and phosphorus in the alimentary tract of lambs infected with daily doses of Trichostrongylus colubriformis or Ostertagia circumcincta larvae.

The flows of endogenous and exogenous calcium and phosphorus in the digesta at the abomasum, ileum and in the faeces were measured in growing lambs infected daily with 3000 T. colubriformis larvae (TC), 5000 O. circumcincta larvae or no larvae. The lambs were given 0.70 or 1.0 kg per day of a pelleted diet and the flow rates were measured by reference to soluble and particulate radioactive markers. The fraction of Ca and P in digesta of endogenous origin was measured by the method of isotope dilution involving a single intravenous dose of 45Ca or 32P. Ostertagia circumcincta infection was without effect on the absorption and secretion of Ca and P in the digestive tract, other than producing a small but significant increase in the endogenous faecal Ca excretion. There was, however, a striking increase in the flow of digesta at the abomasum, the DM and Na content of which was consistent with an increased secretion from the mucus-type cells in the abomasal mucosa. The extra digesta was absorbed in the small intestine. Trichostrongylus colubriformis infections reduced the absorption of exogenous P by about 30 per cent and increased losses of endogenous P due to the action of worms on the mucosa of the small intestine. The net effect of this was to induce a P deficiency in TC lambs, leading to a reduced flow of salivary P and a reduction in the plasma concentrations of P. The effect of TC on Ca metabolism was limited to an increase in endogenous faecal excretion.

Calcium and phosphorus absorption in lambs exposed to Trichostrongylus colubriformis.

Ten lambs (29 +/- 1.2 kg) reared parasite-free and prepared with rumen, duodenal and ileal cannulae were paired and one of each pair was given a daily oral dose of 2500 Trichostrongylus colubriformis larvae for 14 weeks. Untreated animals received the amount of ration consumed by their infected pair-mates the previous day. During weeks 6 and 12 of infection, all lambs underwent a 7 day calcium (Ca) and phosphorus (P) balance. During weeks 7 and 13, duodenal and ileal samples were collected to determine the amounts of Ca and P entering and leaving the small intestine. The infection caused varying degrees of feed refusal in all infected animals. As a result, the data on Ca and P in excreta and the amounts of Ca and P entering and leaving the small intestine were regressed against dry matter (DM) intake for each group at each period. There were no between-period differences in these relationships. Calcium absorption and retention were unaffected by the stress of infection. Infection affected several aspects of P metabolism. Blood P concentrations were markedly reduced. Absorption of P from the small intestine was greater (P less than 0.01) in control lambs (at 1 kg DM intake 6.6 g per day) than in infected animals (2.2 g P per day), but there was a greater (P less than 0.05) duodenal flow rate of P in control lambs which suggested much higher rates of salivary secretion of P than in infected animals. Phosphorus flow rates at the ileum were greater (P less than 0.01) in infected lambs, despite the lower duodenal flow rates, which indicated a major abnormality (P less than 0.01) in small intestine absorption of P in infected animals; this may have contributed to the growth check experienced by these lambs.

The effects of a concurrent infection of Trichostrongylus colubriformis and Ostertagia circumcincta on calcium, phosphorus and magnesium transactions along the digestive tract of lambs.

Twelve lambs, paired on the basis of live weight, were cannulated in the abomasum, proximal jejunum and terminal ileum. Six were infected with 3000 T. colubriformis and 3000 O. circumcincta larvae per day for 18 weeks. The other six lambs were pair-fed to the infected lambs. All animals were offered fresh ryegrass and white clover pasture, cut daily. Dry matter intake, live weight and plasma Ca, P and Mg concentrations were measured throughout the experiment. During weeks 7 and 17 post-infection, digesta flow along the gastrointestinal tract of infected and control animals was measured. Parasitism depressed dry matter intake by 60 per cent and was associated with a reduction in retention of Ca, P and Mg in both infected and control animals. During weeks 7 and 17, parasitism increased the flow of Ca past the proximal jejunum and, during week 17, the flow of P past the terminal ileum. Increased endogenous Ca and P losses, together with a net reduction in absorption of Ca and P, were associated with depressed plasma Ca and P concentrations. These findings, together with evidence of reduced addition of P to anterior regions of the tract, indicate induced Ca and P deficiency. There was evidence for compensatory absorption of Ca and P in the large intestine and distal small intestine, respectively. Magnesium metabolism was apparently not affected by parasitism.

Trichostrongylus colubriformis infection in rabbits: persistence of the distal adaptive response to parasitism after anthelmintic treatment.

Mucosal changes associated with anthelmintic treatment in Trichostrongylus colubriformis-infected rabbits were assessed along the entire length of the small intestine. The following groups, each of five rabbits, were compared: infected (group I); infected and treated on day 21 with fenbendazole (group IT); uninfected but given fenbendazole on day 21 (group C, controls). All animals were killed on day 28. In the proximal part of the small intestine of group I rabbits, the worms were associated with shortening of the villi and a significant depletion in alkaline phosphatase activity, which differed significantly from the findings in groups C and IT. In the same region, no difference was found between groups C and IT. In the distal small intestine, hypertrophy of villi and crypts (an adaptive response to the infection), coupled with an increase in enzymic activity, were present in both groups I and IT, in contrast to group C. These results suggest that a complete mucosal restoration occurred within 7 days of anthelmintic treatment in the parasitized part of the intestine. In contrast, the adaptive response observed beyond the main site of parasitism was not abolished by treatment. The functional significance of these findings is discussed in relation to the compensatory growth commonly observed after anthelmintic treatment in ruminants.

Chronic infection with Trichostrongylus vitrinus in sheep. Some effects on food utilisation, skeletal growth and certain serum constituents.

The effect on food utilisation and skeletal growth of daily infection for 90 days with 2500 Trichostrongylus vitrinus larvae was investigated. Controls were killed initially or fed ad libitum. Food intake, digestibility of dry matter and nitrogen and content of body fat, protein, water and minerals were determined, and selected bones examined chemically and histologically. Serum constituents were determined weekly. Digestibility of food dry matter and nitrogen were reduced during weeks 3 and 5 after initial infection but subsequently recovered. Deposition of fat, protein, calcium and phosphorus in the body was reduced by 36, 58, 67 and 78 per cent respectively. Gross efficiency of utilisation of metabolisable energy was reduced by 36 per cent. Bone changes were associated with a reduction in osteoblastic activity. Hypoalbuminaemia, hyperglobulinaemia and hypophosphataemia were present in infected sheep. There were no significant changes in serum calcium or urea concentrations. It is concluded that the effects of continuous intakes of T vitrinus and T colubriformis larvae on host metabolism are essentially the same.

Effect of phosphorus intake on growth rate, food intake and quality of the skeleton of growing lambs infected with the intestinal nematode Trichostrongylus vitrinus.

The performance of growing lambs dosed daily for 12 weeks with 2500 Trichostrongylus vitrinus larvae (I) or given no larvae (control, C) was compared at two levels of phosphorus intake; 2.75 gP/kg dry matter (normal, NP) and 1.88 pgP/kg dry matter (low, LP). Both low phosphorus and T vitrinus infection reduced dry matter intake and growth rate and the combined effect of low phosphorus and infection were additive. Plasma hypophosphataemia (less than 60 mg per litre) occurred in groups CLP, ILP and INP from week 3, the values gradually returning to normal levels in INP lambs by the end of the trial. T vitrinus infection did not depress plasma phosphorus concentration below that seen in the low phosphorus controls. Both low phosphorus intake and T vitrinus infection reduced the density and mineralisation of bone, the most severely affected bones occurring in groups ILP lambs. T vitrinus infection reduced the content and concentration of phosphorus in the rumen and the effect was greater at the lower intake of phosphorus. Infection also reduced the proportion of phosphorus in the rumen liquid phase. The number of T vitrinus recovered from the intestine was higher and villous atrophy more extensive in lambs from group ILP. It is suggested that development of 'resistance' may be delayed on a low phosphorus intake.

Subclinical infection with the nematode Trichostrongylus colubriformis increases gastrointestinal tract leucine metabolism and reduces availability of leucine for other tissues.

Gastrointestinal (GI) tract leucine metabolism was measured in 6- to 9-mo-old lambs subjected to trickle infection with Trichostrongylus colubriformis larvae and in separate animals that were not infected. Animals prepared with a jejunal catheter and with indwelling catheters into the aorta and the portal- (PDV) and mesenteric- (MDV) drained viscera were infused simultaneously with [1-13C] and [5,5,5-2H3] leucine to determine GI tract sequestration of leucine from arterial and luminal amino acid pools by tracer and tracee arteriovenous concentration differences. Leucine oxidative losses and net fluxes were also determined across the GI tract. Infection had no detectable effect on whole-body leucine flux, but it increased total GI tract leucine sequestration by 24% (P<.05) and GI tract oxidative losses of leucine by 22 to 41% (P<.01). Net PDV fluxes of leucine were decreased by 20 to 32% during the infection. The infection did not alter either the proportion of precursor leucine used by GI tract metabolism that was derived from the arterial leucine pool (.84 to .88) or the proportional sequestration of digesta-derived leucine during "first pass" absorptive metabolism (.12 to .18). These findings help to elucidate the metabolic basis for the reduced growth rates and nitrogen retention observed when animals are subjected to subclinical nematode infection.

Parasitism (Trichostrongylus colubriformis and Eimeria ninakohlyakimovae) in sheep: relationship between wool fiber diameter changes and feed conversion efficiency.

Twenty-five lambs, 5 months of age, were used to compare the infection pressure of Trichostrongylus colubriformis with that of Eimeria ninakohlyakimovae. Effects of the parasitic infection pressure were assayed by determining body weight gains, feed conversion efficiencies, and wool fiber diameter changes (reflecting changes in protein metabolism) in lambs fed a good ration and those given a marginal diet (dehydrated alfalfa pellets). Significant differences in weight grains or feed conversion efficiencies of nematode- or coccidia-infected lambs and noninfected controls were not found, but significant differences due to the parasites' effect on wool fiber diameters and in lamb response to different feeds were found. Protein uptake or assimilation, or both, were apparently affected by a combination of infection with E ninakohlyakimovae and a marginal diet.

Effects of concurrent subclinical infections by coccidia (Eimeria christenseni) and intestinal nematodes (Trichostrongylus colubriformis) on apparent nutrient digestibilities and balances, serum copper and zinc, and bone mineralization in the pigmy goat.

Subclinical infections by the intestinal nematode Trichostrongylus colubriformis were established in 7 pigmy goats by inoculating each with 4,000 infective larvae 5 days/week for 18 weeks. At the start of the 14th week, 3 of the goats were orally inoculated daily with 10,000 sporulated oocytes of the coccidium Eimeria christenseni for 6 days, producing subclinical infections. During selected weeks, the goats were placed in metabolism cages to monitor feed consumption and collect orts, feces, and urine. Samples of rib, vertebra, and tibia were removed at time of death, on day 126. The superimposition of the coccidial infections on the nematode infections did not affect apparent ash, nitrogen, organic matter, or dry matter digestibilities; balances of nitrogen or phosphorus; serum copper or zinc concentrations; liveweights or feed conversion efficiencies. Mean calcium balances remained positive, although they were reduced during the first week of the superimposed coccidial infections. The mineralization of the matrix of the tibia and 4th lumbar vertebra was less in the goats with the superimposed coccidial infections than in those infected only with nematodes. Presence of the superimposed infections was associated with a decrease in the mean moisture and lipid contents of the tibia.

Influence of subclinical nematodosis on the kinetic disposition of fenbendazole in buffaloes.

The disposition kinetics of fenbendazole was studied in buffaloes subclinically infected with gastrointestinal nematodes. There was significantly reduced uptake of the drug in infected animals compared to uninfected controls. The pH of the duodenal liquor was highly alkaline compared to the acidic pH in uninfected animals. The egg count in the faeces never became zero though the numbers were reduced to a great extent compared to pre-treatment values. The influence of the host's physiology on the reduced bioavailability of fenbendazole is discussed.