gastrins and Haemonchiasis

Abomasal Trichostrongylidae infections are still today an important cause of scarce performances in small ruminants, mainly when bred in extensive systems. Although morpho-biology, symptomatology, prophylaxis and therapy of these infections are well known, other, such as physiopathology, are less investigated. The aim of the present note is to review the more important physiopathogenetic mechanisms of abomasal Trichostrongylidae infections, with special emphasis to Haemonchus spp. and Teladorsagia spp. The parasitic anorexia due to the action of gastrin, the defects of digestion due to hypocloridia, the scarce intestinal absorption and anaemia caused by H. contortus are discussed. Furthermore, the effects of hypersensitivity sometimes caused by these abomasal nematodes are examined. A better knowledge of physiopathological mechanisms can represent an important factor to understand the relationships between host and parasite, useful to set up new diagnostic techniques or new therapeutic and prophylactic protocols for sanitary education and control plans of these important and widespread parasitic infections.

Topics: Abomasum; Anemia, Hemolytic; Animals; Anorexia; Female; Gastrins; Goat Diseases; Goats; Haemonchiasis; Haemonchus; Host-Parasite Interactions; Hypoalbuminemia; Male; Sheep; Sheep Diseases; Stomach Diseases; Trichostrongyloidea; Trichostrongyloidiasis

Nematode larvae developing within the glands cause local loss of parietal cells and mucous cell hyperplasia whereas reduced acid secretion, increased serum gastrin and pepsinogen concentrations and generalized histological changes are associated with parasites in the abomasal lumen. Parietal cells with dilated canaliculi and/or degenerative changes typical of necrosis are present soon after the transplantation of adult worms, and abomasal secretion is also affected. Anaerobic bacteria survive in greater numbers as the pH rises, with bacterial densities becoming similar to ruminal populations at an abomasal pH of 4 and above. Failure to lyse bacteria may affect adversely the nutrition of the host. The parasites may initiate the pathophysiology through the release of excretory/secretory (ES) products which either act directly on parietal cells or indirectly through enterochromaffin-like (ECL) cells by provoking inflammation or by disrupting the protective mucosal defence system. Parietal cell dysfunction is proposed as a key event which leads to loss of mature chief cells and mucous cell hyperplasia, as well as hypergastrinaemia. Inflammation increases circulating pepsinogen concentrations and may also contribute to increased gastrin secretion. Stimulation of mucosal proliferation and differentiation of parietal cells in the isthmus by the raised serum gastrin levels will be beneficial by generating a new population of active parietal cells and adequate acid secretion.

Topics: Abomasum; Animals; Anorexia; Bacteria, Anaerobic; Cattle; Cattle Diseases; Gastrins; Haemonchiasis; Haemonchus; Host-Parasite Interactions; Hydrogen-Ion Concentration; Intestinal Mucosa; Ostertagia; Ostertagiasis; Pepsinogens; Sheep; Sheep Diseases; Stomach Diseases

Excretory/secretory (ES) products collected from exsheathed L3 or parasitic stages of Haemonchus contortus were tested in vitro for gastrin stimulatory properties using an ovine abomasal antral mucosal preparation. In addition, the motility of exsheathed L3 and parasites recovered on weeks 2, 6 and 8 post-infection was studied in water, saline, saline with glucose or ovine blood and in HBSS pH 2.5-7.4. Parasitic stages became immotile rapidly in water and HBSS pH 2.5, more slowly in HBSS pH 3.5, but nearly 100% remained motile for 48 h when blood was included in the medium. Exsheathed L3 motility was reduced only by water and HBSS pH 2.5, and then only in the second week of incubation. Gastrin secretion was not consistently increased by any of the parasite ES products tested in vitro, therefore, they probably do not stimulate the G cell directly to produce the hypergastrinaemia seen in parasitised sheep.

Topics: Abomasum; Animals; Gastric Mucosa; Gastrins; Haemonchiasis; Haemonchus; In Vitro Techniques; Sheep; Sheep Diseases

Abomasal pH and serum pepsinogen and gastrin were increased in parasite-naive sheep by infection with either larval or adult H. contortus. Four sheep received 10000 larvae intraruminally and 9000 adult worms were given directly via an abomasal cannula to another 4 sheep. The latter animals were dosed orally with 0.4 mg kg-1 ivermectin 4 days after worm transfer and their recovery was monitored for a further 8 days. Whereas the presence of adult worms rapidly induced changes in the secretory activity of the abomasum, the early larval stages had minimal effects up to the 4th day post-infection. After either larval or adult infection, the initial hypergastrinaemia began at the same time as the increase in abomasal pH, but serum gastrin continued to increase after abomasal pH had reached a maximum and returned more slowly to normal values after drenching. The increase in serum pepsinogen did not precede those in the other parameters, unlike the earlier hyperpepsinogenaemia which occurs with Ostertagia infection. Three of the 8 infected sheep had no detectable serum pepsinogen increase during the parasitism while showing typical effects on abomasal pH and serum gastrin. The rapidity of the responses to the transfer of adult worms and to their removal by treatment with anthelmintic supports a role for worm excretory/secretory (ES) products which possibly are not produced by the early larval stages. The similarity of responses to H. contortus and O. circumcincta infection suggests the involvement of the same or very similar ES products.

Topics: Abomasum; Animals; Feces; Gastrins; Haemonchiasis; Haemonchus; Hydrogen-Ion Concentration; Larva; Parasite Egg Count; Pepsinogens; Sheep; Sheep Diseases

Blood gastrin and pepsinogen responses of native village goats in Malaysia to a single dose of 10,500 infective Haemonchus contortus larvae were investigated. Both blood values were significantly elevated within a week of infection and exhibited a highly significant correlation during the study. The magnitude of the blood gastrin response was, however, significantly greater than that of pepsinogen during the period that both blood values were elevated. It is suggested that blood gastrin assay may be of particular value in the diagnosis of chronic haemonchosis in animals harbouring relatively light worm burdens.

Topics: Animals; Female; Gastrins; Goat Diseases; Goats; Haemonchiasis; Haemonchus; Pepsinogens

Radioimmunoassay of plasma gastrin has shown that a hypergastrinaemia occurs in yearling sheep, after infection with 10(6) infective third stage larvae of Haemonchus contortus. Plasma gastrin concentrations began to rise two to four days after infection, that is, at about the same time as, or slightly before, the abomasal pH was observed to increase.

Topics: Abomasum; Animals; Gastrins; Haemonchiasis; Hydrogen-Ion Concentration; Radioimmunoassay; Sheep; Sheep Diseases; Trichostrongyloidiasis

Topics: Animals; Gastrins; Haemonchiasis; Hemoglobins; Male; Pepsinogens; Sheep; Sheep Diseases; Trichostrongyloidiasis