Heterakis vesicularis Frölich 1791

Abstract

Several parasites, a flagellate of the genus Giardia and also microsporidia have been reported in intestinal round worms, but up to the present time the latter have not been shown to be concerned in the transmission of disease.

Blackhead, an infectious disease of turkeys and other poultry, is caused by a flagellate, Histomonas meleagridis. It is transmitted experimentally and to some extent in nature by the direct ingestion of material contaminated with freshly passed discharges containing the protozoon. It appears, however, to be much more frequently transmitted indirectly by some phase distributed on the soil, evidently in association with the eggs of the caecal worm, H. vesicularis.

The presence of the protozoon in the egg of Heterakis is indicated by experimental evidence of various sorts.

1. Heterakis eggs kept in 1.5 per cent nitric acid until embryonated produce blackhead when fed to young birds isolated from all other sources of infection, although this treatment renders the material bacteriologically sterile.

2. That there occurs no resistant phase of the blackhead protozoon apart from the worm egg, capable of resisting the 1.5 per cent acid, is shown by the invariably negative results obtained by the repeated feeding of susceptible birds with the discharges of blackhead carriers, after treatment in 1.5 per cent acid. Furthermore, no resistant form has been demonstrated micro-scopically.

3. Heterakis material will only produce blackhead after the ova have blecome embryonated and capable of hatching. Samples of the same material fed before the eggs are ripe invariably furnish negative results.

4. The feeding of male Heterakis also furnishes only negative results although ova-containing females of the same lot produce blackhead.

The disease usually follows the feedinig of large numbersl of Heterakis, especially when the latter are pooled from several different birds.