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In about half the cases of the latter the old worm was
present, but necator Americanus predominated in all heavy
infections. Brem, in Panama, found hookworms in 36.1
percent of 277 patients from various parts of the tropics.

United States.

No systematic investigation has been made of the terri-
tory known to be infected. Dr. C. W. Stiles has made sev-
eral reconnoissances, including a large part of the South.
These have stimulated many valuable observations by
physicians in various parts of the country. The extent and
the intensity of the infection in the whole population can
be surmised from the data present, but a systematic and
extensive search is very much needed.

It is clear that the country from Virginia, at the Potomac
river, to Florida and Texas is infected. In Virginia, Clay-
tor's early case furnished Stiles with the first specimen of
uncinaria Americana. Bagly (1910) believes there are 80
percent of infected work people in the cotton mills.



o» HOOKWOEM DISEASE.

In North Carolina the disease is even more frequent, as
shown by the valuable work of Nicholson and Rankin
(1904). They found that 37 percent of 140 students of
Wake Forest University were infected, usually in a mild
form. Semetimes every man from a given district was
infected.

In South Carolina the conditions are doubtless equally
serious, as shown by Stiles' investigation, but extensive
observations are lacking.

In Georgia the assertion of Harris that the disease is one
of the commonest of the serious diseases was found justified
by C. A. Smith (Atlanta), Warfield (Savannah), A. G. Fort,
and many others.

In Florida extensive observations do not yet exist, but
the disease is frequent, as Stiles pointed out in his early
survey. Kinyoun (1908) found very many hookworm car-
riers, especially among negroes. At present active efforts
are being made for repression of the disease.

In Alabama, Bondurant, of ]\robile (1903), first called at-
tention to the extent of the disease. Harrison, of Talledega
(1204), made an important addition to our knowledge.
Perry (1910) reports 15 to 20 percent in the white popula-
tion infected, and Cole and Winthrop {vide infra) show
even more.

In Mississippi, Bass found from his own observations and
those of correspondents that up to 50 percent of the popu-
lation were affected, and concluded that practically all the
rural population of the southern half of the state have or
have had the infection.

In Louisiana, Lemann and Guthrie called attention to the
importance of the disease in 1903, and many cases have
been observed since then, but no extensive series of cases
has been reported. The conditions in country localities are
doubtless al)ont the same as in adjacent states. Gage and



DISTRIBUTION. 39

Bass have examined 90 students in the Tiilane University
who were living in the state; 42.4 percent of those from the
country, and 2.5 percent from the city were found infected,
or a total in the whole state of 20.7 percent of young male
adults were hookworm carriers.

In Arkansas, Deaderick found comparatively few cases,
and the same will probably hold good in Tennessee.

Texas is widely affected, as Allen J. Smith showed early.
Investigations are now being made by the State Board of
Health, and fully confirm the wide range and intensity of
the infection.

Valuable information appears in a report by Dr. Stiles
to the Bureau of Labor. (Annual Eeport of the Surgeon
General of the Public Health and Marine Hospital Service
of the United States for the fiscal year 1908, AYashington,
1909.)

The investigation shows that 12.67 percent of cotton mill
employees are hookworm suspects. The percentage varies
with sex and age.

^ Percent

suspects.

Over 20 years 8.4

16 to 20 years 19.2

Under 16 years 27.2

Females 16.1

Males 15.2

Boys under 16 years 29.4

Girls under 16 years 18.7

Boys 16 to 20 years 20.7

Girls 16 to 20 years 18.1

Males over 20 years 5.8

Females over 20 years 13.

Interesting observations have been made on recruits in
the United States Army. Siler (1909), in an examination
of 105 recruits from the southern states, found 93 infected,
or 88.5 percent, and 85 percent in a total of 140 cases.

Chamberlain (1909) found 60 percent of infected men
among southern recruits.



40 HOOKWORM DISEASE.

The observations of Gage and Bass on 296 university
students are interesting in comparison with those on re-
cruits, for they deal with young men of about the same age,
presumably equally free from obvious symptoms, probably
belonging-sto families in better circumstances than those of
the recruits, and not so much exposed to the danger of in-
fected soil. The figures are small, but no selection was
made. The number of worms recovered from the subjects
varied from 3 or 4 to 200, so that the men were worm carriers
of real danger under conditions favorable to the dissemina-
tion and development of the ova.

Locality. Positive. Negative.

Alabama 14 19

Arkansas 4 9

Florida 1 4

Georgia 7 7

Illinois 2

Kentucky 1

Louisiana, outsifie New Orleans 27 51

Louisiana, in New Orleans 1 39

Massacliusetts 1

Mississippi 14 38

Missouri 3

Oklahoma 1 3

Pennsylvania 1

South Carolina 3

Tennessee 2 6

Texas 7 7

Canada 1

Porto Rico 1

Roumania 1

Out of the subjects from the southern states outside of
New Orleans we get a percentage of infected students of
32.8.

Winthrop and Cole, in examining 66 Alabama medical
students, found 33, or 50 percent, infected.

Further facts bearing on the economic aspects of hook-
worm should be noted. Among the females of child-bear-



DISTRIBUTION. 41

ing age, 13 to 18 percent are uuable properly to iioiirisli in-
fants. Of males of military age, 5.8 to 20.7 percent are rel-
atively inefficient. Among children of school age, 18.7
(females) to 29.1 (males) are miable properly to profit from
study. "Taking all the statistics together, 12.6 percent of
the mill population are affected with a disease which
materially inhibits their normal working powers, and hence
inhibits the economic development of the community in
which they live."

It should also be noted that in some of the mills the pro-
portion of hookworm cases is as high as 80 percent among
the children.

Stiles has also pointed out the part the negro has in the
perpetuation and spread of hookworm disease. Relatively
immune to the disease, the negro is an extensive worm
carrier, and is even more careless as regards soil pollution
than his white neighbor.

In general, the parasite found in old world cases is ankyl-
ostoma duodenale; that in America, necator Americanus;
but Leiper found the latter widely distributed in the tropics,
especially in Africa. It has been found in returned immi-
grants in Italy, from Brazil as well as from the United
States (Schifone), and also in other localities, but appar-
ently has not yet spread beyond the immigrants. Necator
Americanus has also been found in patients from various
parts of Asia, Ceylon, the Philippines, and Australia, in
the Hamburg Sailor Hospital (Eodenwaldt), and by Noc in
Cochin China. Looss found it in pygmies in Africa, and
Fiilleborn in Cameroon. Da Silva Pinto finds necator more
frequently in the state of Sao Paulo in Brazil than ankyl-
ostoma. Branch thinks necator may be the original and
more common tropical hookworm. The conditions of work
and travel at the present time are such as to cause even
greater mingling of the two species than occurs now.



42 HOOKWORM DISEASE.

Climate.

Tlie chief factors in the existence of hookworm infection,
given the j)resence of the parasite, as by fresh importation,
are high temperature and moisture. The extent of the
disease in fhe tropics makes this clear, and the intensity of
the disease in the tropics even clearer. Outside the tropics,
mines offer the best conditions for the disease to exist. Xot
all mines are equally affected, even when miners carrying
worms are employed. In the mines of Pas-de-Calais, for
exami)le, Brehon found only two infected miners, and they
had come from a mine near Mons, in Belgium. The mines
at Pas-de-Calais have neither high temperature nor great
moisture. So also in Bohemia no cases were found until
1903, and since then only a few. But the mines are not
very deep and the temperature, accordingly, not very high.
Wainwright and Nichols (1904) made a large series of
observations in the anthracite coal mines of Pennsylvania,
but found hookworm in only one case.

Tenholt gives an instructive table showing the relation
of temperature in mines to infection in Westphalia.



TPinnpratiirp Number of Percentage

lempeiaiuie. workmen. of infected.

Below 17°C.=62.6°F. . , 36,033 0.6

17°— 20°C.=62.6°— 68°F 68,604 0.4

20°— 22°C.=68°— 71.6°F 43,710 2.5

22°— 25°C.=71.6°— 77°F 39,836 11.7

Above 2.5°C.=77°F 9,853 39.9

(The most favorable temperature for the development of
the larvge is from 25° to 35° C, or 78.5 to 95° F. Below 22°
C. or 71° F. few ova develop.)

The hot season in countries with temperate climates may
assist in the development of hookworm larvae in permanent
or temjoorary water or in damp earth, but, owing to the
length of time the larvfe require in order to reach the in-



DISTRIBUTION. 43

fecting age, such regions are rarely intense seats of the
disease.

The relation of moisture to hookworm infection has been
noticed by all who have studied the disease. In the tropics,
in brickyards, and in tunnels and mines (coal, tin, salphur,
gold, diamond, etc) a certain degree of wetness of the soil
has been found to obtain wherever the hookworm disease
occurs. This agrees with facts regarding the life history
of the parasites, which will be discussed in another place.
Turner explains the absence of ankylostomiasis in certain
South African mines by the acidity, from sulphuric acid,
of the water. Deep, warm, wet, and alkaline mines are
especially affected.

Stiles has shown that in the southern states sandy soil is
more favorable than clay for the production of the disease.
This is probably due to the fact that in wet sand the larvae
can easily avoid drying and at the same time obtain oxygen.
On dry soil the larvae soon die, and among dwellers of such
places, as the Arabs of the Sahara desert and the Soudanese,
the disease is rarely seen. Deaderick has pointed out that
alluvium offers favorable conditions for the larvae, and that
all the ground conditions are not yet known. The Porto
Rico Commission has also shown that not only alluvium, but
also clay soils, offer numerous foci, but Leichtenstern could
find no larvae in the clay of brickyards. It is important to
distinguish between pools of water that may long remain
on clay and earth free from water. The life history of the
larvae (see Chapter III) will throw much light on the
subject.

Shade is an important element, and will have to be con-
sidered in connection with the life history of the larvae and
the modes of infection. Elevation is of no importance if
the other conditions are favorable; mountains, as the St.
Gothard tunnel, over 3,000 feet above sea level, as well as
coast lands, are involved.



44 hookwoe:m disease.

Occupation and social position of hookworm subjects. —

Hookworms affect especially those who have intimate re-
lations to the soil. In the tropics it is especially the poorer
classes, the agriculturists and their families, that are af-
fected. According to the Porto Eico Commission, for ex-
ample, 85 percent of the nearly one million inhabitants are
poor and 75 percent are agriculturists. "The poorer the
man, the more exposed is he to heavy infection. Coffee
pickers and laborers on coffee estates are the most exposed
of all laborers on the island. Infection on sugar planta-
tions is not so common, but is nevertheless frequent, espe-
cially in the irrigating ditches. ' ' Washing at the edges of
streams and banana culture are other occupations leading
to infection. One of us has observed many instances in
charcoal burners and turpentine "dippers." The people
come from infected regions, and their occupations offer fa-
vorable conditions for the spread of the disease.

Gardening is a possible means of infection in the well-
to-do, as also in j)rofessional gardeners.

In many regions outside the tropics, hookworm disease is
rather a trade disease than an endemic. Mining and brick-
making have frequentl}^ been alluded to. The details of the
mode of infection are discussed in Chapter IV, but it may
be said here that in many places the wives and families of
miners and brickmakers, and sometimes gardeners, do not
share the disease.

Barefooted children. — In certain occupations infection
takes place through the hand, the bare feet, or through de-
fective boots. An imjoortant cause in the southern United
States is the habit among children, even of the better
classes, in the country of going barefoot. Not only country
children, but city children, in the summer vacations have
ground itch, and later hookworm disease, as we have ascer-
tained in dozens of instances. Even adults oecasionallv get



DISTRIBUTION. 45

infected by wading- in pools, yielding to what Claude A.
Smith aptly calls "the joy of going barefoot." In heavily
infected regions persons of all kinds of classes and occupa-
tions, and of all ages, occasionally get the disease. In
some of these the method of infection is obscure. Dirty
vegetables or fruit, or skin infection by larvae-containing
water, are the most probable.



CHAPTER HI.

-, ZOOLOGIC FEATURES.

Hookworms belong to the class of nematodes, the family
strongylidae and subfamily strongylinaB.

The nematodes form a very large class of worms, usually
long and narrow, from 1 millimeter to 40 to 100 centimeters
in length, round on section, and sometimes hair-like in their
proportions. The sexes are usually distinct; the males
usually smaller than the females, and generally distin-
guished also by the shape of the tail end, which is some-
times rolled in a circular, spiral, or cork-screw manner;
sometimes, as in hookworms, s]3read out like an umbrella,
or funnel-shape. The length of the body is sometimes
marked, as in ascaris, by four longitudinal bands. There
are in some species circular striations, and in others the
bodies are smooth, or furnished with papillae or other ap-
pendages. The mouth end varies in shape in different
genera, is generally narrower than the body beyond it, and
possesses six papillae. It passes into a muscular esophagus,
that also varies in shape and proportion in different genera,
and this in turn is followed by the chyle-gut and the
rectum, which opens near the tail end of the worm. The
nerves of nematodes are made up of scanty groups of gan-
glion cells and fibers, especially well developed around the
esophagus. The parasitic species have no special sense
organs. Some free-living ones have two reddish eyes, fur-
nished in some species with lenses. The excretory organs
consist of a system of tubes, ending in an excretory pore.
The genital organs are tubular. That of the male opens in
common with the rectum, and that of the female is separate

4G



ZOOLOGIC FEATURES. 47

from and usually anterior to the anus. All male nematodes
have preanal and postanal papillae, which are used in
specific differentiation. The eggs are so-called ''simple
ova," containing only one kind of cell, and, though varying
considerably, are usually characteristic for each species.
Some species are oviparous, and others viviparous. The
development of nematodes is simpler than that of tape-
worms or flukes. In many cases, as ascaris, trichocephalus,
and oxyuris, there is no intermediate host; in others, as
dracunculus and filaria, there is. In some, as strongyloides,
there is reproduction outside the definitive host. In the
case of hookworms, as we shall see, part of the development
of the larvae takes place outside the host. Very few nema-
todes (strongyloides) reproduce outside the definitive host.

Round worms live partly in fresh or salt water, in earth
or mud, in decomposing matter of all kinds, partly parasitic
in various organs of animals, and very often in plants.
Familiar examples are the common intestinal round worm,
ascaris lumbricoides, the "vinegar eel" (anguillula aceti),
and the trichina spiralis (trichinella) ; one of the most in-
teresting is the "hair-worm" (gordius), popularly sup-
posed to develop from horse-hair put in water for that pur-
pose, and in rare cases found as a parasite in man.

The nematodes are subdivided into eight families:

1. Enoplidse. Live free; many species in sea water.

2. Anguillulidae. Characterized especially by a double
swelling of the esophagus ("rhabditic") ; live free, es-
pecially in fresh water or in earth, or in decomposing
material ("vinegar eels"); many are parasites of plants,
and a few of animals. Many are very minute.

3. Angiostomidae. Developing by heterogeny, contain-
ing the genus strongyloides.

4. Gnathostomidae. A small family, often parasitic in
wild animals, but very rarely in men.



48 HOOKWORM DISEASE.

5. Filaridse. Very long, narrow worms, represented by
several species of important parasites, including filarise.

6. Trichotracliilid«. Containing several important para-
sites, especially trichina (trichinella) and tricliocephalus, or
the whipworm, a common parasite of man in warm coun-
tries.

7. Strongylidse. A very large group subdivided into
several sabfamilies. Besides hookworms, eustrongylus,
strongylus, and sclero stoma belong to this family.

8. Ascaridae. Containing the common parasitic round
worms and pinworms, and some others.

The strongylidsB form a very large family. They are
characterized by long, cylindrical bodies, rarely filiform;
the possession of six oral papillae — two lateral and four
sub median — generally projecting in the form of nodules or
conical points; a mouth capsule with or without teeth,
either in the body axis or turned dorsally or ventrally. The
esophagus is more or less swollen in the posterior part. The
males have a "bursa copulatrix" and one or two spicules;
the females have one or two ovaries. The eggs are usually
deposited in segmentation, sometimes containing the em-
bryo. The sexes are distinct. Important members are the
"colic worms" of horses and the kidney worms of hogs (but
not the kidney worms of dogs and man — Stiles), the "gape
worms" of chickens, and the hookworms. Many others are
frecjuent parasites of various lower animals, and occasion-
ally of man. The members of the family have undergone
many changes of nomenclature, not necessary to describe
fully in this place. There is also much difference of opinion
regarding the nomenclature and classification of the hook-
worms. The following list shows some of the most im-
portant synonyms in chronological order:

1789: uncinaria — Frolich.

1843: agchylostoma dnodoualo — llulnni.



ZOOLOGIC FEATURES. 49

1845: ancylostoma duodenal e — Creplin.
1850: an cliylo stoma duodenale — Dubini.
1851 : ancylostomum duodenale — Diesing.
1851: strongylus quadridentatus — von Siebold.
1851: sclerostoma duodenale — Cobbold.
1861: dochmius anchylostomum — Molin.
1861: monodontus — Molin.
1866: strongylus duodenalis — Schneider.
1876: dochmius duodenalis — Leuckart.
1879: anchilostoma duodenale — Bozzolo.

Ankylostoma Duodenale.

The generic name above, or ankylostomum duodenale, or
ancylostomum duodenale (French, anchylostome; German,
ankylostomum or anchylostomum; Italian, anchilostoma) is
preferred in England and the continent for the old world
hookworm. No matter how spelled, Dubini 's name seems
justified by the accuracy of his description. The spelling
' ' agchylostoma, " passable in Italian, would have to be
latinized for international nomenclature, "ancylostoma"
being the correct spelling.

The name uncinaria was widely adopted in America by
reason of the important work of Stiles, though Looss from
the beginning objected to the change on account of the fact
that the genus uncinaria of Frolich agrees with the type
criniformis (Goze) more than with ankylostoma duodenale
(Dubini). More recently (1907), Stiles states that "the
old genus uncinaria (type vulpis^ criniformis) must be
divided into at least four smaller groups: uncinaria (type
vulpis), agchylostoma (type duodenale), necator (type
Americanus), bunostomum (type trigonocephalum), and
probably into several additional units. . . . Evidence
is accumulating to the effect that they should be given



50 HOOKWOEM DISEASE.

generic rank." The recent (1909) classification of Railliet
and Henry shows the same tendency. Besides the two
human species of ankylostoma and necator, there are sev-
eral species of the genus uncinaria which are found in
lower animals — e. g. :

Uncinaria canina,

Uncinaria stenocephala, tin dogs.

Uncinaria trigonocephala,

Uncinaria (ankylostoma) tubaeformis, or ^

Uncinaria perniciosa, !>in cats.

Uncinaria Balsamoi, ' J

Uncinaria trogocephala, in shee^D.

Uncinaria radiata, in cattle.

Uncinaria Lucasi, in seals (thought by Looss to be the
cause of the great mortality — 17 percent — of suckling seals
on the Pribiloff Islands).

Uncinaria os papillatum, in elephants.

There is no j^roof that any of these infect man, and among
lower animals each genus infested seems to have its own
species of hookworms. The worm supposed by Rathonyi to
be a hookworm in mine horses in Hungar}^ has been shown
to be a sclerostoma.

In order to make clear the anatomic features of human
hookworm, it seems best to describe at length the one long-
est known, and to mention more briefly the points of differ-
ence in the new world 23arasite. In this we follow the
more exhaustive descriptions, especially of Looss, Stiles,
and Allen J. Smith.

The old world hookworms are small and almost cylin-
drical, the male about 10 millimeters long and 0.45 milli-
meters wide, the female 12 to 18 millimeters long and O.GO
millimeters wide. (Frontispiece.) In both sexes the an-
terior end tapers gradually. In the female the jDosterior end
tapers to a fine point or spine. (Fig. 1.) The posterior end



ZOOLOGIC FEATUKES.



51




J— >








p<



be






52 HOOKWORM DISEASE.

of the male tapers in about the last quarter of its length, but
the tip of the tail is concealed by the bursa, which flares out
to a width equal to that of the thickest part of the body, or
even more, giving the tail end a square or sometimes con-
cave appea^'ance at the end. The color when alive is some-
what flesh-red or cream color; when dead, duller, gray or
grayish white. The posterior two-thirds are often brown
or reddish brown, from blood in the intestine. The skin is
smooth, delicate, with fine transverse striations, AVith the
bending of the worm transverse folds are formed, especially
about the head. The name hookworm is often supposed to
be due to the bending of the head backwards, and this is so
striking a feature that the supposition is natural, though
the name was given on account of other "hooks," as has
l)een mentioned before. Eight (Smith) — Looss, four — mus-
cular bands, most pi ainl}". defined on the sides, symmetric-
ally arranged, run the length of the body, merging to-
gether laterally to form a fairly continuous body wall, and
in the male help to form the bursal ribs.

Besides the proper skin muscles, Looss describes certain
special muscles, such as the anal muscles, in female worms
only; the vulvar muscles; the cephalo-esophageal muscles,
which pass from the top of the nervous ring to the surface
of the esophagus, and, extending obliquely forward through
the bod}^ cavity, are inserted partly in the skin and partly
in the mouth capsule. They probably assist in the move-
ments of the head, as well as in those of the buccal capsule.
The end of the chyle -gut is surrounded by a network of
muscles, especially well developed in males. In both sexes
there is a sphincter muscle of the rectum. Finally, there is
a complicated system of muscles in connection with the
tail end of the male.

The body cavity is divided by a membranous septum at-
tached dorso-ventrally, in the folds of which, as in a mesen-



ZOOLOGIC FEATITKES,



Do



-Ceri^g/.s.




Fig-. 2. Male hookworm (ankyl-
ostoma duodenale) of man. ac. "p.,
accessory piece to spicules; a. p., anal
papilla; h. c, buccal capsule; can. cerv.
gl. s., canal of left cervical gland; cerv.
gl. d., right cervical gland; cerv. gl. s.,
left cervical gland; cu., cuticle; cul.,
cul de sac of testicular tube; e.,
esophagus; e'., posterior end of


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