Development of morphological changes and ileal glucagon gene expression in the small intestine of lambs infected with Trichostrongylus colubriformis

A Comparative Study on Pathological Changes in the Small Intestine of Sheep and Goat Experimentally Infected with Trichostrongylus colubriformis

Background

Trichostrongylus colubriformis, also called hairworm, is a genus of parasitic roundworm affecting gastro-intestinal tracts of a ruminant. Gross and microscopic lesion characterizations and comparing its effect in the small intestine of sheep and goats experimentally infected with T. colubriformis were undertaken in the study.

Methods

During the study period, 13 sheep and 14 goats were included in the experiment. The larvae of T. culibriformis were obtained from abattoirs and larvae were recovered by Bearmann techniques. The infective larvae of T. culibriformis (L3) as a single dose of 10,000 per-animal was administered orally to infected groups of sheep and goats. Blood was collected for hematological and serum biochemical analysis. Tissues for gross and histopathologic lesions characterization were collected from killed infected animals at 56 days.

Results

From the infected group, the total recovered mean worm burden was recorded as higher in goats (P<0.05) than sheep, with an establishment rate of 50.16% and 34.46%, respectively. The total mean PCV, Hb, and albumin values recorded in the infected groups of sheep and goats were significantly (P<0.05) lower than non-infected control of both animal groups. In goats, the total serum protein was significantly (P<0.05) lower in the infected group than the non-infected control group. Gross lesions found were enteritis with petechial hemorrhages, edema, hyperemia, and mucosal slough, which were marked in the duodenum (62.69%) and jejunum (33.33%) in sheep and 47.05% duodenum and 45.09% jejunum in goats. The microscopic lesions developed by T. colubriformis were subtotal villus atrophy, hemorrhage, straightened and elongated dilated crypts, loss of epithelium, mucosal erosion, and infiltration of inflammatory cells.

Conclusion

The present study showed that T. colubriformis infection caused physiological and pathological changes of the small-intestine in sheep and goats, with more severe infection in goats than sheep, although they were under the same management condition.

Effects of Oesophagostomum dentatum and dietary carbohydrates on morphology of the large intestine of pigs

The effects of Oesophagostomum dentatum infection and dietary carbohydrates on the morphology and epithelial cell proliferation in the gastrointestinal tract of pigs were investigated experimentally. Thirty-two worm-free pigs (n=32) from a specific pathogen-free farm were randomly divided into four groups (A-D), of eight animals each. Pigs in groups A (control) and B (infected) were fed Diet 1, and pigs in groups C (control) and D (infected) were fed Diet 2. The two diets were formulated: Diet 1 (%) contained barley flour, oat husk meal plus soya bean meal (55:21:24) and Diet 2 (%) contained barley flour, inulin and sugar beet fibre (SBF) (80.1:7:12.9) plus soya bean meal (3:1) to contain carbohydrates from inulin and sugar beet fibre (SBF) that were readily fermentable in the large intestine. The two infected pig groups (16 pigs total) were inoculated with 6000 infective larvae of O. dentatum and all pigs, including the controls, were slaughtered 12 weeks p.i. The combination of O. dentatum infection and highly fermentable dietary carbohydrates affected the mucosal architecture, the epithelial cell proliferation and mucin secretion of the large intestine. Infection had a significant influence on the crypt volume, height and density, and on muscularis externa at the proximal and middle colon. The changes in the affected gut sections were proportional to the number of worms present. However, these parameters appeared unaffected by those diets alone. In pigs without infection non-digestible dietary carbohydrates significantly influenced the tissue weight of colon.

Influence of enteric helminths on the distribution of intestinal endocrine cells belonging to the diffuse endocrine system in brown trout, Salmo trutta L

The presence of intestinal helminths in the alimentary canal of brown trout, Salmo trutta L., can alter the number of cells that synthesize modulatory peptides. A total of 167 brown trout were collected from tributaries of the River Brenta (northern Italy), of which 119 (71.3%) specimens were infected with enteric helminths, 28 with the acanthocephalan Pomphorhynchus laevis Müller, 1776 with intensity of infection ranging from 1 to 162 (18.57 +/- 30.79) worms per host and 67 fish with the cestode Cyathocephalus truncatus Pallas, 1781. Intensity of infection with C. truncatus ranged from 1 to 85 (6.87 +/- 12.59) per fish. In 24 fish there were concurrent infections of both species of helminths. The caecal and middle regions of the intestine were the most heavily parasitized. Immunohistochemical tests showed a decrease in endocrine cells (ECs) of the diffuse endocrine system (DES) positive to gastrin, cholecystokinin-8, bombesin and secretin antisera in the intestine of the infected trout. The number of ECs immunoreactive to anti-glucagon serum did not show differences in the digestive tract of uninfected brown trout and in conspecifics parasitized with P. laevis. The density of cells containing glucagon-like material was low in the fish parasitized with C. truncatus. The results suggest that endoparasitic helminths induce alterations in the DES of infected S. trutta.

Influence of diet complexity on intestinal adaptation following massive small bowel resection in a preclinical model

AIMS

To investigate the effect of dietary complexity on intestinal adaptation using a preclinical model.

METHODS

Four-week-old piglets underwent a 75% proximal small bowel resection or transection operation (control). Post-operatively, animals received either pig chow (n = 15), polymeric formula (n = 9), polymeric formula plus fiber (n = 6), or elemental formula (n = 7).

RESULTS

The weight gain of all groups was reduced compared with controls that were fed the same diet. Animals that had a resection, which were fed elemental formula, had significantly reduced weight gain compared with the other groups (4.7 4.2 vs 30.7 7.1 kg chow and 11.5 1.3 kg polymeric formula). Villus height was increased in the jejunum, ileum and terminal ileum of resected animals compared with controls in animals fed with pig chow, polymeric formula and elemental formula. The animals that had a resection had a significant reduction in the transepithelial conductance (10.4 5.5 vs 25.4 6.5 mS/cm2) and 51Chromium-EDTA flux (2.8 1.9 vs 4.8 4.9 microL/h per cm2) compared with the controls.

CONCLUSIONS

A complex diet was found to be superior to an elemental diet in terms of the morphological and functional features of adaptation following massive small bowel resection.

Adaptive physiological processes in the host during gastrointestinal parasitism

Parasite infection of the gastrointestinal tract with helminths or protozoa induces detrimental effects on host tissues and host physiology, which have been extensively studied and reviewed. However, parasitism of the digestive system is also associated with adaptive, compensatory phenomena based on changes in host physiology or structures and which tend to counterbalance the negative consequences. The objective of this review is to describe these adaptive processes and their possible underlying mechanisms. Different processes which tend to attenuate the effect of either the loss of appetite, the intestinal malabsorption or the increased tissue losses have been assessed. These processes have been reported both for helminth and protozoan infections, where they present similar characteristics. The mechanisms involved in the adaptation to parasitism remain largely unidentified. The role of feedback mechanisms based on host regulation, possibly through gastrointestinal hormones, has been raised. On the other hand, some data support the proposal that parasites themselves may initiate some of the adaptive processes and consequently favour their own survival. These adaptive phenomena appear to be an essential component in the dynamic balance between host and parasites. Also, parasite infections represent unique models to study the adaptation of the gastrointestinal tract to aggressors.

The immunobiology of gastrointestinal nematode infections in ruminants

The major gastrointestinal nematode parasites of ruminants all belong to the Order Strongylida and the family Trichostrongyloidea. Despite this close evolutionary relationship, distinct differences exist in the microenvironmental niches occupied by the developmental stages of the various parasites, which may account for the variable susceptibility of the different parasite species to the immune effector mechanisms generated by the host. In addition, different manifestations of resistance have been observed against the adult and larval stages of the same parasite species, and even against the same parasite stage. In particular, both rapid and delayed rejection of infective larval stages of gastrointestinal nematode parasites has been documented. This review will give an overview of the various manifestations of resistance to gastrointestinal nematode parasites of ruminants, as well as the immune mechanisms and antigens associated with the generation of immunity by the ruminant hosts to these parasites. In addition, a working model is provided aimed at reconciling most of the present knowledge on the different immune responses generated during infection with the various parasite rejection profiles. Extrapolation of these results to field conditions will need to take into account the variability imposed by seasonal changes and management practices, as well as the individual variability in immune responsiveness present in outbred animal populations.