VASCULAR LESIONS IN RABBITS INFECTED WITH TRYPANOSOMA (TRYPANOZOON) BRUCEI

Abstract

When a rabbit is inoculated with Trypanosoma (Trypanozoon) brucei usually only a few parasites appear in the circulating blood. Nevertheless, 3 to 5 weeks after inoculation the animal becomes listless, the fur staring, and the ears pale, thick and heavy. The tissues around the eyes are swollen, and scabby necrotic lesions appear in the skin of the face, ears and scrotum. The animal dies several weeks after inoculation and the cause of death is unknown.This paper describes some observations on the circulation in the ears and muscles of normal and infected rabbits and an attempt is made to explain the vascular changes which accompany chronic trypanosome infection. METHODS Infection of rabbitsTrypanosomes (T.(T.) brucei, strain Tororo 427) were passaged in mice. The blood of an infected mouse was diluted in phosphate-buffered saline (pH 7.8) and then injected subcutaneously into male New Zealand white rabbits weighing 2.5-3.5 kg. Each rabbit received a volume of blood containing 107 trypanosomes and the animals were housed at 230 C. A naesthesiaBetween 4 and 5 weeks after inoculation with strain 427, when the animals showed signs of the infection, they were anaesthetized with halothane. A tracheal tube was inserted and anaesthesia maintained with N20 (20%), 02 (80%) and halothane (0.5-2.5%). The flow rate was 2.5 1./min. A few of the early experiments were carried out under intravenous pentobarbitone anaesthesia. A ngiographyContrast medium and drugs were introduced into the arterial system of the rabbit's ear through a plastic cannula tied into the right common carotid, the right mandibular or the right subclavian artery. A cannula passed caudally through the left carotid artery into the aortic arch was also tried. The contrast medium, sodium iothalamate (May & Baker) or sodium metrizoate (Glaxo), was injected rapidly through the cannula using either a manually operated syringe or a Cordis injector (pressure: 90 lb./sq. in.). The quantity of contrast medium required depended on the closeness of the cannula to the auricular artery, 2 ml. being sufficient for injection into the mandibular, 3 ml. for injection into the carotid and 8 ml. for injection into the subclavian artery. Radiographs of the ear were taken using a 0.1 mm focus X-ray tube (Rank Medical). Single pictures were usually taken on completion of the injection using industrial film (Gevaert Structurix) but in some experiments eight pictures were taken at intervals of 0.5 sec using a Schonander Serial changer and standard X-ray film (Ilford).R

Pathology of the Disease in Sheep Produced Experimentally by Trypanosoma brucei

“…The accumulation of trypanosomes and the cellular inflammatory exudate in tissues were often accompanied by focal, and occasionally diffuse, areas of acute necrosis of the interstitial and parenchymatous tissues. This infiltration of mononuclear cells into infected tissues and the necrosis may indicate, as suggested by GOODWIN and HOOK [6], that a cell-mediated immunological response of the delayed hypersensitivity type is tlie cause of tlie injurious effects.…”

Review of Pathology of Diseases in Domestic and Laboratory Animals Caused by Trypanosoma congolense, T. vivax, T. brucei, T. rhodesiense and T. gambiense

“…A positive correlation was found between the kinins and the number of trypanosomes in the blood [23]. In the rabbit the ears were reported to be oedematous, and microscopically there was a chronic angiitis and cellular and exudative inflammatory reaction [24,119,1201. Accompanying the reaction in the ears there was a decrease in red blood cells, packed cell volume, and haemoglobin.…”

Thrombocytopenia in Experimental Trypanosomiasis

“…First, in experimental rabbit trypanosomiasis, each wave of parasitemia is caused by trypanosomes with antigens different from those of the predecessors, against which antibody has already been produced (16). Second, Goodwin and Hook (17) have shown that the major pathologic changes in rabbits infected with Trypanosonta brucei are vascular lesions, thrombus formation, and increased vascular permeability. Finally, kinin concentrations are increased in experimental infections of laboratory animals (18) and volunteers (19).…”