Retarded gastric acid secretion in rats infected with larval Taenia taeniaeformis.

The influence of hepatic larval Taenia taeniaeformis infection on gastric acid secretory activity and gastric mucosal integrity was investigated. After 12 weeks of infection with 2,000 T. taeniaeformis eggs, the gastric pH values of control and infected rats were 4.1+/-0.6 (mean +/- SD) and 8.4+/-0.2, respectively. There was no difference in the basal acid secretion between control (1.7+/-0.7 micro Eq.H(+)/15 min) and infected (1.9+/-0.3) rats. However, infected rats failed to respond to histamine stimulation, the maximum acid output level being 2.8+/-0.4 in the infected rats, compared to 12.9+/-3.3 in control rats. Larval T. taeniaeformis infection resulted in the suppression of gastric acid secretion leading to hypergastrinemia.

Histopathology and physiopathology of gastric mucous hyperplasia in rats heavily infected with Taenia taeniaeformis.

Rats heavily infected with larval Taenia taeniaeformis show hyperplasia of the gastric mucosa accompanied by mucous cell proliferation, increase in the level of intragastric pH and hypergastrinemia. Sixty one rats were divided into 2 groups designed as infected (36 rats) and control (25 rats) group. These rats were examined with time course of the infection histopathologically and physiopathologically, during 14-112 days postinfection (DPI). In the infected rats, gastric mucosal hyperplasia began to be observed at 56 DPI, and the structural disturbance of zymogenic units in the corpus and mucous units in the antrum had increased with time. However, the degree of these changes in the antrum was weaker than those in the corpus. Alcianblue and/or PAS-positive cells increased in their numbers with time, and 4 types of cells other than typical surface mucous cell and mucous neck cell were observed by electron-microscopy. However, zymogenic and parietal cells decreased in their number after 56 DPI. Further, the infected rats showed changes in the serum concentration of alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, glucose and total protein. Some similarities with Menetrier's disease were discussed.

Role of host immune response in the occurrence of gastropathy in rats infected with larval Taenia taeniaeformis.

Decrease of spleen weight from peak to control levels together with a corresponding decline of serum IgG level at the onset of gastric hyperplasia in Taenia taeniaeformis-infected euthymic rats, may indicate that a form of down regulation of host immune response during the course of larval T. taeniaeformis infection could facilitate the occurrence of gastropathy in rats. Gastric hyperplasia developed in T. taeniaeformis-infected athymic nude rats, indicating that occurrence of gastropathy associated with larval T. taeniaeformis infection in the rat is T cell independent. Apparently, gastric hyperplasia appeared early in nude rats which suggests that absence of T cell-mediated response could have facilitated its early occurrence.

Abundance and prevalence of Culicoides (Diptera: Ceratopogonidae) on some Philippine chicken farms.

In total, 10,067 biting midges of the genus Culicoides comprising 17 species were collected in a light trap survey of 50 chicken farms in the province of Batangas, southern Luzon, Philippines, between 14 September and 5 December 1988. The species of greatest prevalence and abundance were Culicoides effusus Delfinado, Culicoides peregrinus Kieffer, and Culicoides palpifer Sen & Das Gupta. Engorged females of C. effusus, C. peregrinus, C. palpifer, Culicoides oxystoma Kieffer, Culicoides arakawae (Arakawa), Culicoides guttifer (Meijere), Culicoides albibasis Wirth & Hubert, Culicoides huffi Causey, Culicoides clavipalpis Mukerji, and Culicoides wenzeli Delfinado were collected. The abundance and prevalence of C. effusus, C. peregrinus, and C. C. palpifer in the overall sample of farms as well as in farms with previous occurrence of leucocytozoonosis indicated that these species are potential vectors of Culicoides-borne Leucocytozoon caulleryi Mathis & Leger among chickens in this area. Although blood-engorged females of C. arakawae were collected frequently, the prevalence and abundance of this species were limited.