Blood Loss during Hookworm Infection, Determined by Erythrocyte Labeling with Radioactive 51 Chromium. II. Pathogenesis of Ancylostoma braziliense Infection in Dogs and Cats

Abstract

Detection and measurement of fecal blood loss from pups and kittens infected with Ancylostoma braziliense showed that, compared with Ancylostoma caninulm, A. braziliense was relatively nonpathogenic. Blood loss started on the 10th and 11th days after inoculation of A. braziliense larvae to pups and kittens, respectively. Group mean ml (standard deviation) of blood loss per worm per day in the feces was 0.00109 (? 0.00111) from pups and 0.00187 (? 0.00187) from kittens. Even with relatively large infections of 600 to 800 A. braziliense the total blood loss per pup per day was less than the normal prepatent fecal blood loss and was equivalent to from 0.2% to 1.3% of circulating blood volume each day. Absence of pathogenesis was also shown by the failure of A. braziliense infection to adversely affect hematologic measurements and weight gains although infection of pups and kittens with A. braziliense induced a slight hypoproteinemia. There were no changes in halflife of circulating erythrocytes nor was there evidence of alteration of the normal rate of intravascular catabolism of erythrocytes. Clinical signs of infection were not detected, since pups and kittens infected with 600 to 800 adult A. braziliense appeared to be normal. It appeared that kittens were a less suitable host for A. braziliense than were pups, since size in kittens. A previous report (Miller, 1966b) described results of experiments in which the technique of labeling the erythrocytes with radioactive l1chromium was used to measure blood loss from dogs of different ages during infections of varying severity with Ancylostoma caninum. Fecal blood loss was measured and was correlated with changes of hematologic values during the infection. Observations in previous reports (De Faria, 1910; Sarles, 1929) indicated that Ancylostoma braziliense was probably less pathogenic than A. caninum in dogs. This suggestion was based on absence of deaths of infected dogs and on failure to observe free blood at necropsy either in the lumen of the dogs' intestines or in the gut of the worms. The present report describes experiments, using the technique of erythrocyte labeling with 15chromium in pups and kittens that were inoculated with A. braziliense larvae, to investigate the pathogenesis of infection with this hookworm. MATERIALS AND METHODS Management of experimental pups and procedures for culturing and preparing larvae for infection were described (Miller, 1964). The Received for publication 8 June 1966. the worms were slower to develop and of smaller special techniques of caging pups, labeling erythrocytes with 5lchromium as sodium chromate in isotonic saline, daily blood sampling and total fecal and urine recovery, and the measurement of blood, fecal, and urine radioactivities have also been described (Miller, 1966b). Kittens were purchased when 6 to 10 weeks old, were housed individually in wooden cat cages, and were vaccinated against the feline infectious enteritis complex (Fiovax, Registered Trademark of Burroughs Wellcome & Co., England). Diet for the kittens consisted of a prepared canned meat fed ad lib., and milk. Metabolism cages were not used for the kittens since the habits of cats with respect to the use of a soil-tray facilitated total fecal recovery. Urine was not collected from the kitte s but total daily urine output was collected from four of the five pups infected with A. braziliense. The culture of A. braziliense was obtained from a dog in quarantine, 2 months after importation from Durban, Republic of South Africa. The method of purification of the culture (i.e., exclusion of A. caninum) was described (Miller, 1966c). Techniques of culturing, harvesting, cleansing, and preparation of A. braziliense larvae for inoculation were the same as those used for A. caninum (Miller, 1964). Five pups were infected, when 5 months old, with 1,000 A. braziliense larvae by subcutaneous inoculation. Four 3-month-old kittens were similarly infected with 500 or 1,000 A. braziliense larvae. During the course of infection, and until necropsies were performed at 24 to 26 days after inoculation of larvae, blood samples (approximately 1 ml) were collected from the five pups