Experimental studies on the migratory behavior and fate of toxocara canis larvae in the mice
Experimental studies on migratory behavior and distribution of Toxocara canis larvae were carried out, and histopathological changes in various organs of mice infected orally with Toxocara canis larvae were observed according to the various duration.
Eggs collected from worms or feces were cultured on tile or filter paper in petridish containing 0.5% solution of formalin at room temparature for 4 weeks. 0.5㎖ suspension containing 500 to 1,000 infective stage eggs were directly introduced into stomach through stomach tube.
On sacrifice the skinned body od mouse was divided into two parts at longitudinal median line. To determine the location where the larvae were concentrated, a half of the body was further divided into five parts; neck, fore leg, thoracic wall, abdominal wall and hind leg. Muscles were digested by artificial gastric juice(0.5% pepsin, 0.7% HCl in normal saline) to detect the larvae. Brain, liver and kigney were also digested. Baerman technic was used to detect the larvae from the shredded muscles and visceras.
Another half of the body was put into Bouin's or formalin fixative solution for histological specimens. Histological specimen of various part of body and organs of infected mouse were examined after staining with Hematoxyin-Eosin.
The results are summarized as follows:
The distribution attitudes of Toxocara larvae were different by time and organ. On the 2nd day after inoculation larvae were only detected from abnominal wall, lunge and liver.
On the 3rd and 4th day of inoculation, the distribution rate of the larvae in lung and liver showed almost equal.
From the 4th day after inoculation distribution rate of the lavae in brain increased gradually and the rate maintained almost same level of 20-35% up to 30th day after inoculation. Up to 5th day after inoculation, the rates in the kindney were gradually increased. The distribution rates of the larvae at neck part were
higher than in rther locations of the body up to 30th day after inoculation.
The highest distribution rates of Toxocara larvae after the inoculation were observed in brain from 150 to 360 days. And only a few larva were found in lung, liver and kidney at this stage.
In liver, cellular infiltration of polymorphonuclear leukocyte and mononucleated leukocyte were appeared arround the worm. On 30th day after infection granulomatous cchange with infiltration of the polymor-phonuclear leukocyte, epitheloid cell, fibroblast and giant cell around the worm was observed and the worms showed no noticeable morphological change. Inflammatory cells and leukocytes were infiltated around the granuloma.
No cellular infiltration around the worm was observed in brain. Especially, eosinophilic granules were appeared in the intestine and esophagus of the larvae on 270th day after the infection.
In early stage of infection, pathological change was not appeared in the kidney;
however, granulomatous change and mild fibrosis was observed 150 days later.
The larvae were found at interspace of the muscle fibers, and granuloma was formed and infiltrated with polymorphonuclear leukocyte, epitheloid cell and other cells. Mild fibrosis and giant cells were also observed.