Possible role of histamine in the genesis of pulmonary arterial disease in cats infected with Toxocara cati.

Kittens between 12 and 20 weeks of age were orally dosed with 6000 infective ova of Toxocara cati. Animals were sacrificed at intervals between one and eight weeks after infection to study the development of pulmonary arterial lesions. After two weeks, marked leucocyte infiltration and mild thickening of the media of some of the smaller arteries was apparent histologically . Cellular inflammatory activity progressively increased up to four weeks after infection when intimal proliferation was evident in many of the arteries. After six weeks, the arterial walls were grossly thickened with pronounced intimal proliferation which after eight weeks had resulted in complete occlusion of some vessels. The progressive arterial occlusion was associated with a three- to four-fold increase in the parenchymal mast cell population and a corresponding increase in lung histamine content. The possible role of histamine in the genesis of the arteriopathy is discussed.