Studies on the Hookworm Larva as a Vector of Pathogenic Microorganisms

Abstract

Hookworm larvae in their early stages of development are intimately associated with materials heavily contaminated with pathogenic microorganisms. The present investigations are directed toward the possibility that these larvae might act as vectors in the dissemination of certain diseases related in their epidemiology to soil contamination.

The first requirement was to establish the nature of the association existing between larvae and micro-organisms. McCoy 1 has shown that hookworm larvae are able to grow to the infective stage on 22 out of 25 species of bacteria tested. He concludes that all of the evidence from his experiments indicates that living bacteria constitute the essential food utilized by hookworm larvae in developing to the infective stage.

The present work was undertaken to determine whether or not these bacteria could be ingested in their intact form. Certain evidence is presented to show that this is a physical possibility. Of less certainty is the demonstration of bacteria within various portions of the alimentary tract of immature larvae and within the sheath spaces of infective larvae.

The observations were made on living larvae by means of a tech-nic in which the larvae may be studied under the oil immersion power of the microscope. The larvae therefore show no alteration or distortion of structure such as might be produced by death, staining or fixing of the specimens. The observations and measurements can readily be made during more or less prolonged periods of inactivity of the larva.