3
I NFECTED PEOPLE NECE SARY FOR SPREAD OF DISEASE.-All the favor­able
conditions for the disease may prevail in a given locality and yet
no hookworm disease will exist, unless the egfls of the parasite have
been deposited there with the f eces of some infected person and allowed
to develop. Hence, in cities, where sewerage systems are used, or the
night soil collected and hauled away, regardless of climatic conditions,
we do not find the disease.
RURAL SECTIONS FAVORABLE TO ITs SPREAD.-Elsewhere, on the con­trary,
where open privies and, far too often, no privies at all, are used,
millions upon millions of eggs are scattered over the earth, and develop
into minute, infecting worms ready to attack and vic~imize any accessi­ble
member of the human family_
In the Southern States all the factors n ecessary for the propagation
of the disease are found. We have the warmth, moisture, oxygen, and
infected people, who pollute the soil. North of the Ohio and Potomac
rivers the climate is too cold and, in the arid West, too dry to favor
the disease. In these sections, therefore, the' disease is rare.
HOOKWORM DISEASE AFFECTS A "IMALs.-Dornestic and wild animals
suffer from hookworm disease. Cows, dogs, cats, and foxes, and many
other animals in certain localities, have been known to sicken and die
in large numbers from hookworm disease. For man it is indeed fortu­nate
that the hookworms found in such animals do not molest him.
The hookworrn which infests man belongs to a type separate and dis­tinct
from those found in animals.
These facts considered, let us now direct our attention to the hook­worm
as a parasite and a disease producing factor.
THE HOOKWORM: ITS LIFE CYCLE.
HOOKWORM ECGs.-The hookwonn (see Figs. 1 and 2) germinates
from an egg. This egg (Fig. 3), with myriads of others, passes with
the excreta from the bowels of an infected person. A lack of oxygen
in the human intestine prevents its hatching until it has passed from
the body.
FIG R E 1. A male hookworm, n atural size.
FIGURE 2. A female hookworm, natural size. (P. H. & M. H. Service.)
SIZE OF EGG.-The egg is far too small to be seen by the unaided eye.
It must be magnified a hundred times to be recognized. So small is it
that in a portion of feces no larger than the head of a small pin two or
three dozen eggs may be found. In shape, size and markings if differs
distinctly from the egg of any other worm. It is oval, rather bluntly
rounded at the ends. The yolk is dark in appearance and is surrounded
by a clear, transparent zone which separates it from the shell.