The Etiology of Visceral Larva Migrans: II. Comparative Larval Morphology of Ascaris lumbricoides, Necator americanus, Strongyloides stercoralis and Ancylostoma caninum

Publisher Website
Google Scholar
Abstract
The morphological characters of all tissue stages and the larval behavior in the abnormal host are described for A. lumbricoides, N. americanus, S. stercoralis, and A. caninum. These larvae can be identified most easily by characters seen in transverse sections at the level of the mid-intestine, such as the presence and size or lack of lateral alae and posterior excretory columns, the type of intestine, and the relative diameter of the body. A. lumbricoides, Strongyloides, and N. americanus larvae are unable to exist for long periods as the tissue stage. Those forms failing to undergo tracheal migration are unable to survive in tissues for more than a few weeks and are therefore unlikely to be incriminated in visceral larva migrans. Similarities in behavior exhibited by Toxocara canis and A. caninum larvae suggest that the latter is also capable of producing visceral larva migrans in man. A. caninum is capable of survival as the tissue stage for periods in excess of 1 year. It is further suggested that skin-penetrating larvae of the A. caninum type may be involved in the etiology of tropical eosinophilia.