The diagnostics and treatment of tropical diseases

Chapter XXII: Filarial Infections

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GENERAL CONSIDERATIONS

The filarial worms are thread-like nematodes, with a thin cylindrical oesophagus, which live in various parts of the body and may or may not give rise to disease conditions. It is one of the most remarkable facts in animal parasitology that a person may harbor numerous adult filariae and myriads of embryos without in any way manifesting symptoms of the infection. In most of the filarial worms the female has a double uterus with the uterine opening near the anterior extremity.

It has been proposed to designate the filarial embryo by the
term microfilaria, reserving the generic name _Filaria_ for the
adult parasite. This may be convenient for differentiation but
zoölogical nomenclature does not permit different names for adults
and embryos. While there have been almost 20 different filarial
species reported for man there is, in some instances, doubt as to
the correctness of the observation, and again, a well recognized
species has at times been considered as a new species and given a
new name.

From a practical standpoint we need only consider: (1) _Filaria bancrofti_; the adult of which lives in the lymphatic glands and vessels while the sheathed embryos (which from their appearance in the blood only at night are called _Filaria nocturna_) obtain access to the peripheral blood vessels.

Various well-known conditions are caused by this parasite, such as
elephantiasis, varicose groin glands, chyluria, etc. This infection
was formerly stated to be caused by _Filaria sanguinis hominis_.

(2) _Loa loa_, the adult of which wanders about in the subcutaneous tissues, characteristically in the region of the eyes, while the sheathed embryo is found in the blood during the day, hence _Filaria diurna_.

Calabar swellings, irregular febrile conditions and the
disagreeable sensations incident to the wanderings of the worm are
clinical features of this infection.

(3) _Onchocerca volvulus._ The males and females of this parasite are found coiled up in channeled connective tissue tumors of the subcutaneous tissues.

The sheathless embryos have been surely found only within these
tumors and not in the blood.

(4) _Acanthocheilonema perstans._ This parasite does not seem to give rise to clinical manifestations except possibly to cause an irregular fever.

The adult is found in the retroperitoneal connective tissue or fat,
while the sheathless, blunt-tailed embryo is found in the blood,
both by day and night, hence _perstans_. The adult forms are found
in the tissues behind the abdominal aorta and at the attachment of
the mesentery.

(5) _Dracunculus medinensis._ The female of this parasite, about 36 inches long and 1/15 inch in diameter, travels to the subcutaneous tissues of the extremities and boring through the skin causes a small surface erosion.

An unimportant filarial worm which has been found only in the West
Indies and British Guiana is known as _Filaria demarquayi_ or _F.
ozzardi_. The embryos have sharp tails and are without a sheath.
The parasite is not known to produce symptoms.

HISTORY

_Filaria bancrofti._—While elephantiasis was frequently described by ancient writers yet the confusion between Elephantiasis Graecorum, a term applied to leprosy, and Elephantiasis Arabum, or the filarial condition, made the question of the nature of the skin thickenings very indefinite.

The thickenings due to leprosy and those connected with filariasis
were separated clinically by observers during the 17th and 18th
centuries, Hilary, in 1750, having accurately described the
progress of that form of elephantiasis connected with elephantoid
fever and lymphangitis. In 1863 Demarquay discovered filarial
embryos in the exudate of a chylous hydrocele and three years
later Wucherer, in Brazil, found similar nematode larvae in the
urine of a case of haematochyluria. Commencing with the year 1863
Lewis carried on a series of investigations in Calcutta in which
he found these embryos not only in the urine of patients with
chyluria but as well in the lymph and blood of those affected with
elephantiasis. He called the parasite _Filaria sanguinis hominis_,
a name still frequently employed by medical writers.

In 1876 Bancroft, in Australia, discovered the adult filarial worms
in a lymphatic abscess, hence the name _Filaria bancrofti_. In
1878 Manson, in China, demonstrated the mosquito transmission of
the disease as well as the phenomenon of nocturnal periodicity.
Manson’s idea, however, was that the fully developed embryo escaped
from the body of the infected mosquito at the time of the death of
the insect and that man contracted the infection in drinking water.

The investigations of Low and more recently those of Fülleborn and Bahr and others have shown that the larvae escape by way of the mosquito’s proboscis and enter the skin of man.

_Loa loa._—The knowledge of a filarial infection of the region of the eye seems to date from the time of Magellan. Although the disease is now confined to the west coast of Africa, cases were reported from the West Indies by Mongin and Bajou during the 18th century. These cases were in slaves who had contracted the infection in Africa.

In 1891 Manson noted the presence of the larval forms which showed
a diurnal periodicity in the peripheral blood.

_Dracunculus medinensis._—Ancient Egyptian writings would indicate that the disease was well known in those times. It is believed that the fiery serpent of the wilderness, which afflicted the Children of Israel, was an infection of this sort.

The prevalence of dracontiasis, as the infection is generally
termed, in Arabia, was well known to the Greeks and Romans.

Fedschenko, in 1870, noted the transmission of the disease by
species of _Cyclops_.

_Onchocerca volvulus_ was first discovered in 1893, in peculiar tumors of the natives of the Gold Coast.

_Acanthocheilonema perstans_ was first found by Manson, in 1891, in the blood of natives of the Congo.

Daniels also found these embryos, along with those of _F.
demarquayi_, in the blood of natives of British Guiana.

FILARIA BANCROFTI

GEOGRAPHICAL DISTRIBUTION

This parasite has been found in almost all tropical and subtropical countries. It is quite prevalent in the West Indies and has been found in some of the Southern states of the U. S. It is very common in some of the South American countries as well as in Central America. The infection is widespread in Arabia, India and China. Africa, especially the West Coast, and Australia, particularly in Queensland, are parts of the world where the infection prevails.

It is especially in some of the Pacific islands, as Samoa and Fiji,
that it is extraordinarily prevalent. Bahr has stated that Fijians
in the proportion of 27% show filarial embryos in their blood. In
25% of these natives clinical manifestations of the disease exist
but the embryos are absent from the peripheral circulation. In
other words more than one-half of the population show absolute
evidence of infection.

LIFE HISTORY

It is a well-known fact that filarial embryos may be present at night in the peripheral blood of persons not showing a single symptom of filariasis and again, in those with marked elephantiasis, varicose groin glands or chyluria there may be an entire and permanent absence of embryos in the blood. When certain mosquitoes bite persons having embryos in the blood they take into their stomachs the sheathed embryos of _F. bancrofti_. Flu states he has succeeded in infecting the following mosquitoes: _C. fatigans_, _S. scutellaris_, _M. ludlowi_ and _M. rossii_. The most suitable carriers proved to be _C. fatigans_ and _S. scutellaris_. Large numbers of larvae perish in anopheline mosquitoes.

The following developmental cycle has been demonstrated for _Culex
fatigans_ and _Stegomyia pseudoscutellaris_. Bahr has found that
if there are too many embryos taken up by the mosquito the insect
is apt to die, as the result of too heavy an infection; so that
a person harboring many filarial embryos may be less dangerous
than one with a smaller number. Upon reaching the stomach of the
mosquito the sheath of the embryo becomes fixed in the viscid blood
contents and the embryo itself by active motions is able to force
itself from its sheath. This escape usually occurs within two hours
but may take longer. The free embryo then bores its way through the
stomach walls and within twenty-four hours has reached the thoracic
muscles of the mosquito. Within forty-eight hours the embryo begins
to broaden and the anterior and posterior V spots to become more
prominent. About the end of the first week there commences the
formation of an alimentary canal, by which time the developing
larva is about 0.5 mm. long. When the larva is about 0.6 mm. long
an ecdysis apparently takes place. Later on these larvae develop
3 or 4 terminal papillae and make their way to the fleshy labium
of the mosquito’s proboscis. An occasional larva may enter other
structures than the labium but in such case they would be unable to
effect an entrance to their definitive host, man. These larvae in
the proboscis are about 1.5 mm. long and about 20 microns broad.

The mosquitoes have two terminal processes, the labella, separated
from the labium by a thin membranous partition called Dutton’s
membrane. The larvae, having completed their developmental cycle
in the mosquito, which takes about three weeks, and moving down the
labium, break through this membrane when it is put upon a stretch
by the wide separation of the labella at the time of feeding on
the part of the mosquito. It was formerly supposed that the larvae
entered man through the puncture made by the biting parts of the
mosquito, but Bahr has shown by experiments that they effect
an entrance through the intact pores of the skin as does the
ancylostome larva.

These larvae upon entering the human host reach the lymphatic vessels or glands and in this definitive host (man) the females are fertilized by the males and give off sheathed larvae from the uterine opening near the anterior end of the worm.

The sheath is simply the egg membrane which from being oval at
first becomes stretched by the developing embryo to finally become
a long, narrow sac encasing the fully developed embryo as it exists
in man. From the lymph stream they reach the general circulation.
In a case of a man with filarial embryos in his peripheral
circulation, who committed suicide one morning, Manson found the
embryos, in large part, contained in the vessels of the lungs.
There were 675 embryos per slide in blood from the lungs for one
from blood from the spleen or liver. It would thus appear that
during the day, when the embryos are absent from the peripheral
circulation, they retire to the lungs. In the case of the filarial
embryo of persons in the Pacific Islands there does not appear
to exist any periodicity. Bahr thinks this absence of nocturnal
periodicity to be connected with the habits of its principal
intermediary host, _Stegomyia pseudoscutellaris_, which feeds by
day. _Culex fatigans_ feeds at night.

With the filarial embryos found in patients in the Philippines
there is also a lack of nocturnal periodicity. In the opinion of
Ashburn and Craig the Philippine filarial worm is a new species,
_Filaria philippinensis_.

Walker, however, recently examined four adult filarial worms in
the Philippines and was unable to note any differences from _F.
bancrofti_.

PATHOLOGY AND MORBID ANATOMY

The adult worms may exist in numbers and over long periods of time give off great numbers of embryos into the peripheral circulation without there being any evidence of disease in the patient. There is apt to be at such time a marked eosinophilia. The process by which the fibrosis of lymph channels with obstruction to the flow of lymph occurs is unknown. Some think that with the pouring out of embryos inflammatory processes, bacterial or otherwise, may be set up. We know that there is a tendency for these adults to die and become calcified, in this way bringing about lymphatic obstruction.

Bahr notes the influence of adult filariae in producing an increase
in connective tissue in glands and considers such glands as less
resistant to bacterial infection.

Manson has an idea that some factor may cause the female to give off immature embryos, which being oval, and of considerable width, may block the lymphatics.

It has often been claimed that various cocci were the exciting
factors in the lymphangitis associated with filariasis. Recently
Dutcher has reported the isolation of an organism resembling
_B. subtilis_ as the cause of filarial lymphangitis (_Bacillus
lymphangiticus_).

As the result of the lymphangitis and blocking of the channels
the embryos cannot reach the peripheral circulation; hence when
obstruction does occur and symptoms of lymph stasis appear, there
may be an absence of embryos in the circulation.

It is now well established that patients with elephantiasis very rarely show embryos in the peripheral circulation, and this fact should be better understood because there is a tendency to negative a filarial diagnosis when embryos are absent from the peripheral circulation.

These lymph channel obstructions may at one time cause dilatations
or varices and at another bring about solid oedemas of the
tributary parts. The treatment will be considered under each
special form of the disease. It may be stated however that
salvarsan, arsenophenylglycin and other similar remedies have been
without special effect in destroying the filarial worms.

CLINICAL MANIFESTATIONS

Not only is it important to understand that elephantiasis and other manifestations of filarial infection may and usually do exist without there being embryos in the peripheral blood of the patient, but also, that a high percentage of a population may show filarial embryos in their blood and yet never or with extreme rarity show any of the signs of filarial disease. These people, with abundant embryos in their blood, usually show no disturbance of health. In the Philippines one may rarely see a case of chylocele but usually there is nothing clinical to note.

Johnson, in examining 400 people, in Charleston, S. C., found
19% with filarial embryos, yet only 5% showed any symptoms of
filariasis. Croll states that 11.5% of 4000 Europeans admitted
to the Brisbane Hospital (Australia) showed filarial infection
but practically none had symptoms. In South Queensland cases of
lymphangitis, chyluria and varicose groin glands are occasionally
seen and rather frequently hydrocele and filarial abscesses. There
is an absence of elephantiasis.

Elephantoid Fever

The febrile accessions that accompany the recurring attacks of lymphangitis in elephantiasis, lymph scrotum and other filarial manifestations, are very important because they may lead to errors in diagnosis.

Thus in Barbadoes, where there is no malaria, a condition in
which there occurs a high fever of sudden onset with rigors and
associated erysipelatous redness of leg or scrotum, accompanied by
lymphangitis and painful lymphatic glands, has given a suggestion
of a malarial paroxysm. The tense inflamed area, after several
days, shows an exudation of lymph and the redness disappears,
but with some resulting thickening of the affected tissues. Such
attacks may terminate with profuse sweating.

The treatment of the condition is such as would be advisable for ordinary lymphangitis—rest in bed, elevation of the part, laxatives and local applications.

Lymph Scrotum

This condition is apt to set in with fever. The scrotal tissues are somewhat tense and reddened and may show numerous lymphatic varices which when pricked with a needle, give exit to lymph which may or may not contain filarial embryos. The lymph continues to exude for a long time. Erysipelatous manifestations are not uncommon. With recurring attacks the scrotal tissues become more and more hypertrophied and may go on to elephantiasis of the scrotum.

Ordinarily local applications with suspension of the scrotum is the
proper treatment. Should the thickening increase to a great extent
the blubbery tissues may be excised, care being exercised to avoid
the testicles and to bring together sound tissue for the enclosing
flaps. These wounds usually heal readily, although there may be
delay in healing from the outpouring of lymph in cases where the
flaps include diseased tissue.

Varicose Groin Glands

Swellings which come on rather slowly and insidiously may involve the inguinal or femoral groups of glands of one or both sides. The epitrochlear glands may also be involved. The skin over the enlarged, rather doughy glands can be freely moved but the glands themselves are bound down to the deeper tissues. Elephantoid fever may set in associated with local manifestations of pain and redness.

If such glands are punctured with a hypodermic needle lymph,
which may contain embryos, exudes. This test together with their
slow disappearance on lying down and slow return on assuming the
upright position should differentiate hernia. When the contents of
a hernial sac are omental there is some difficulty in diagnosis. As
a rule it is not advisable to interfere surgically in this filarial
condition.

Filarial Abscesses

As a rule injury to the adult filarial worms, which results in their death, is not followed by abscess formation but such termination may occur. These abscesses have been found deeply seated in the extremities. Wise and Minett in a careful examination of 28 such cases found evidences of adult filariae in 22 cases. In 21 of these abscesses, infections with streptococci or staphylococci were demonstrated. Very interesting also is the finding of filarial worms in deep-seated abdominal abscesses.

As regards location, these filarial abscesses were found 31 times
in the pelvis of the kidney, 18 times in the epididymis, 12 times
in the retro-peritoneal tissues, 25 times in the inguinal glands,
4 times in the ilio-psoas muscles and 8 times in the lymphatic
vessels.

They regard the endemic funiculitis to which attention has been
directed by Castellani as simply a similar process involving
the tissues about the spermatic cord. The treatment of filarial
abscesses is similar to that of other abscesses.

Chyluria

As the result of obstruction of the lymphatic vessels varices may form in the bladder lymphatics and, as the result of their rupture, milky urine may be passed. If the thoracic duct be occluded the urine will show an abundance of fat, while if the obstruction exists only in other lymphatics, the milky fluid will be found to show but little fat. Blood is usually present in chyluria so that the urine will show an pinkish tinge.

Chylous urine coagulates rapidly and we have in such a specimen of
urine, upon standing, an upper fatty layer and pinkish sediment at
the bottom, with a clot between.

The sediment shows lymphocytes and at times filarial embryos. When
the exudate is lymph mixed with blood the term haematolymphuria
would be a better one.

Clots may form in the bladder and give rise to obstruction to the
flow of urine from the bladder.

The appearance of the chyluria is often preceded by heaviness about
the loins and pains in the region of the bladder.

The morning urine in such a case is apt to be clear while that
passed later in the day is milky in appearance.

A feature of chyluria is its tendency to disappear and reappear
so that when treating such a case one should be conservative in
considering the treatment as effecting a cure.

It is difficult to understand why chyluria should be common in
India and China while almost unknown in the filarial infections of
the Pacific islands.

In treating a case of chyluria one should enjoin rest in bed,
laxatives and a restriction of fluids and fats. Patients subject
to the condition should refrain from active exercise and other
conditions which might cause fatigue. Drugs are of little value.

Filarial Orchitis and Hydrocele

The condition rather resembles an attack of epididymitis. As a result of recurring attacks hydrocele develops. The fluid may be lymphous or chylous in appearance and upon microscopical examination may show filarial embryos. These filarial hydroceles seemed to be the most common manifestations of the disease as observed in the Philippines. These hydroceles or chyloceles do not become very large but may require tapping.

Elephantiasis

As the result of recurring attacks of lymphangitis the tissues of the affected part show the effects of lymphatic obstruction by an hypertrophy of the skin and subcutaneous tissues. It would seem that the combination of lymphatic obstruction and bacterial infection is necessary for the production of elephantiasis. The skin of a part affected with elephantiasis is rough and the hair scanty. In addition to the lymphoedema of the part there is a great increase in the connective tissue.

On account of the lymphatic stasis incision into the blubbery
tissue causes the outpouring of much lymph.

Elephantiasis of the lower extremities is by far the most common
situation, giving us probably 90% of such affections. In Fiji
elephantiasis of the upper extremities is quite common.

Other favorite sites are the scrotum, vulva, breasts and penis.
Rarely the scalp or areas about neck or trunk may show involvement.

Surgical treatment is the one usually followed. When an extremity
becomes too much of a burden, amputation may be indicated. The
employment of the method of lymphangioplasty, which consists in
the introduction of silk threads into the subcutaneous tissues,
to make a channel to the normal lymphatics, does not seem to have
been attended with any degree of success or at any rate permanent
results. These wounds tend to become infected and if this does not
occur the new channels are speedily obliterated.

Castellani recommends the use of Merck’s fibrolysin in injections of from 2 to 4 cc. daily, for three to six months. After each injection the part is tightly bandaged with flannel or rubber bandages. The injections may either be made into the affected part or into the gluteal region. Massage prior to the bandaging may give better results. When the limb becomes smaller and the skin smoother, long strips of skin and subcutaneous tissue may be dissected out and the adjacent edges sutured.

In considering the advantages of operation in elephantiasis of the
scrotum it is usually stated that the only question involved is the
removal of a burdensome mass which in no way is a source of danger
to the life of the patient. At the same time such patients are
subject to attacks of elephantoid fever, a condition not without
its dangers. There is one factor not usually brought forward and
that is the remarkable effect of a successful operation on the
mental state of the patient. This is well shown in the accompanying
illustrations of the patient before and after operation. If
sexual deficiencies are of so powerful an influence on persons of
education how much greater must they weigh on an uneducated native
with but few of the higher interests of life.

Prior to operation the patient should be kept in bed for a day
or so to lessen the amount of fluid and to secure relaxation of
tissues. Thorough scrubbing with soap and water the day of and the
day before the operation and the use of alcohol as an antiseptic
are important. Some prefer iodine.

For the operation the lithotomy position is employed. An assistant
supports the scrotal tumor wrapped in a sterile towel. Fauntleroy,
whose method I give, does not recommend a tourniquet to the base of
the tumor as in his opinion it assists but little in controlling
haemorrhage and endangers asepsis. Haemostats answer better and as
the vessels which give most trouble are deeply situated the elastic
cord would not affect them. In some cases there is very little
bleeding. The upper part of the pear-shaped tumor usually affords
sufficient sound skin next the thighs for the flaps. As a rule
the elephantoid tissue does not involve the upper 2 or 3 inches
of the skin anteriorly, which is thus available to cover in the
base of the penis. In addition to this covering for the penis we
have a long prepuce which has been considerably stretched so that
after removing all elephantoid tissue there is enough sound prepuce
remaining to cover the distal 2 or 3 inches, so that usually there
is sufficient sound skin for a 5-inch penis.

The flaps which are to cover the penis and testicles should be
mapped out with shallow incisions and care must be exercised that
only sound skin is included in these flaps. A horseshoe shaped
incision is made commencing at the left side of the base of the
tumor about 1 inch from the thigh and about at the level of the
penis in health. The incision is carried downward and passes just
below the opening of the penis on the tumor surface. A similar
incision on the right side completes the horseshoe curve. Next a
downward incision in the sound skin is made over the posterior
surface of the tumor, thus encircling the base of the scrotum. The
anterior horseshoe incision is now deepened to free the penis,
care being taken not to injure the spermatic cord. Next the
incisions are deepened laterally until the testicles are reached.
The testicles are usually in the center of the tumor imbedded in
a blubbery tissue from which they can be easily stripped. The
remains of the gubernacula are then hooked up and cut close to the
testicles. The tunicae vaginales are often thickened and contain
fluid which has to be drawn off.

In 60% of Fauntleroy’s cases it was necessary to remove one
testicle on account of extensive disease. One must also bear in
mind the possibility of hernial complications and undescended
testicle.

A sound is now introduced into the urethra and the septum of the
scrotum divided close to the sheath of the penis, then dissecting
away the blubbery tissue. At this stage there may be considerable
bleeding.

The testicles and spermatic cords are then dissected away from the
tunicae vaginales. The penis is now freed by a circular incision
around and above the opening in the anterior part of the mass.
The remainder of the horseshoe flap is now dissected up and the
penis freed. The proximal covering for the penis is made from this
horseshoe flap which is stitched to the distal one shaped from the
prepuce, carefully trimmed of elephantoid tissue.

The lateral flaps are brought together with linen or silk-worm gut
sutures leaving space for a drainage tube and we thus form a new
scrotum for the testicles.

The mortality is usually given as 5% but Fauntleroy did not lose a
case among 149 such operations, the tumors varying from 10 to 85
pounds in weight.

Chylous Hydrocele

Filarial affections of the tunica vaginalis or the testicle itself are not rare. In the milky fluid obtained by tapping such a hydrocele we may find filarial embryos.

Besides chylous hydrocele we may have a chylous ascites or a
chylous diarrhoea. Where there is no obstruction to the thoracic
duct there is less fat and the condition is more properly a
lymphocele rather than a chylocele. The same distinction is
applicable to the other conditions connected with lymphatic varices
due to lymphatic obstructions other than that of the thoracic duct.

LABORATORY DIAGNOSIS

The blood from a needle prick of the finger tip or the lobe of the ear can be examined as a fresh preparation. It is advisable to make a vaseline ring around the drop of blood on the slide and then apply a cover-glass. Such a preparation will permit of the examination of the living embryos for a day or more.

Smear preparations may be made by the Ehrlich method of drawing
cover glasses apart or by the Daniels method on slides. Some
prefer making a thick smear of a drop of blood and, after it
has dried, carefully to dehaemoglobinize it with water and then
staining with dilute haemotoxylin. Staining with Leishman’s or
Wright’s stain gives beautiful pictures. Fixation with methyl
alcohol or with heat, by burning off a film of alcohol, and then
staining with Giemsa’s stain or some haematoxylin preparation, is
to be recommended. On the whole I consider haematoxylin the most
desirable staining reagent, as such preparations hold their color
for a long time. The paper-like sheaths are seen as if twisted
about the larvae with their violet-stained cells. One should note a
break in the violet-stained cell column which is 50µ from the head
end of _F. bancrofti_ and 40µ for _L. loa_.

A V spot is seen posterior to the break in the cell column and
shows best with very light staining.

The break in the column of the cell nuclei marks the position of the nerve ring, which is distant from the head one-fifth the total length. The anterior spot, below the break in the cell column, is distant about 30% of the total length. It is the location of the excretory pore. In _F. bancrofti_ the cell nuclei extend to 95% of length, thus differing from those of _L. loa_, which fill up the tail end. At about 82% of the length from the head is located the anal pore.

Ruge’s thick film method for malarial parasites gives excellent
results in staining filarial embryos. Either the Giemsa or
haemotoxylin staining may be employed.

Embryos may be found in the lymph from varicose groin glands or in
the exudate from a chylous hydrocele, as well as in the urinary
sediment from a case of chyluria.

The failure to find embryos in no way negatives the existence of a filarial infection.

Adult filariae, either alive or dead and calcified, may be found in
the lymphatic glands or in the contents of filarial abscesses.

The blood shows an eosinophilia.

LOA LOA

This filarial infection is at present only known for the West Coast of Africa. In the Cameroons and in Old Calabar the infection is quite common.

As noted in the table previously given, the adults which are a
little more than an inch long have cuticular protuberances or
bosses, about 12 to 15 microns in height. The sheathed embryo is
very similar to that of _F. bancrofti_, but has a more twisted
tail and shows a complete filling up of the tail end with rather
elongated cells. The lines of the curves of the embryo show
irregularities and are not the smooth lines characteristic of _F.
bancrofti_ embryos.

The periodicity is diurnal, for which reason the parasite was originally termed _F. diurna_.

Leiper has reported two species of _Chrysops_, one of the tabanid
biting flies, as transmitting agents and considers that the embryos
undergo development in the salivary glands of the fly.

The life history is not well understood but as a rule a period of
several years elapses after infection before adult filariae or
filarial embryos are found. Again, for some reason, adult filariae
may be noted and when extracted be found full of embryos and yet
embryos not be found in the peripheral circulation.

The adults are noted for their tendency to move about in the
subcutaneous connective tissues having been found in such tissues
in the region of scalp, trunk, penis and extremities.

Most frequently, however, they are noted in the tissues about the
region of the eyes and even under the conjunctivae, from which
location they have been frequently extracted. It is this which has
caused the name _Filaria oculi_ to be given the worm.

The course of the wandering worm is usually marked by an oedematous track. In his own case, recently reported by a medical man, the first symptoms were transient painless swellings about the joints, associated with stiffness. Various diagnoses, such as rheumatism, erythema nodosum and angioneurotic oedema were made in his case. Although two adult filariae were removed at different times the blood examinations were negative for embryos.

As a rule the appearance of the worms in the subcutaneous tissues
is characterized by itching sensations and a feeling of tension.
Warmth causes them to appear in the superficial tissues while
cold makes them confine themselves to the deeper structures.
Eosinophilia is rather pronounced.

=Calabar Swellings.=—Although we have no absolute proof that these usually painless swellings, which occur rather suddenly on various parts of the body having only a thin layer of connective tissue, as forearms, face, ankles, hands, are connected with an infection with _L. loa_, yet such is the general view. These swellings are about the size of a hen’s egg, do not pit on pressure and last for about three days. There is marked tension over the swellings and they may itch greatly.

Rarely does one note more than one swelling at a time. Eosinophilia
is quite marked during the attacks. Manson thinks the oedema
results from the extrusion of embryos from the female at the site
of the swelling. Ward considers the cause to be toxic material
excreted by the worm.

There is very little of importance in connection with treatment.
When the worms, which travel in the tissues about the eye, at the
rate of about ½ inch per minute, are noted, some local anaesthetic
may be used and the worm seized with forceps and extracted through
a small incision. Elliot recommends the application of hot
fomentations to the eye and upon the appearance of the worm under
the conjunctiva to instill cocaine solution, seize the worm with
forceps and then pass a silk ligature through the conjunctival
fold taking in the worm. The ligature is tied and an incision made
through which the worm is extracted. Cooling local applications, or
an ichthyol ointment, may be applied to the Calabar swellings.

ONCHOCERCA VOLVULUS

This name is given to a filarial worm, found principally on the West Coast of Africa, which causes the formation of subcutaneous tumors. In certain localities as many as 10% of the population may be infected. More recently the parasite has been reported from Guatemala.

It is supposed that the adult worms cause an inflammation of the
lymphatic vessel in which they may lie and that a formation of
new connective tissue results, giving rise to a tumor-like mass,
which is most often found in the axilla or about the sides of the
thorax. This tissue stroma encompasses the worms except for the
anterior extremity of the female, with its uterine opening, and the
posterior extremity of the male carrying the spicules, which ends
lie loose in a sort of cyst-like dilatation, which is filled with
a viscid fluid swarming with unsheathed embryos. These tumor-like
masses cause very little discomfort, last indefinitely and do not
tend to ulcerate.

It was formerly thought that these larvae were absent from the peripheral circulation but more recent investigations in cases of onchocerciasis have shown sheathless larvae in the blood, which had the characteristics of those in the contents of the tumors. Such findings, however, are of extreme rarity, the blood examination being almost invariably negative.

The cysts are usually found on the sides of the chest and are quite
superficial, with the skin freely movable over them. They may be as
large as a hen’s egg but usually are smaller. They are also found
over trochanters or along the crests of the ilium.

Dubois states that the embryos may be found in juice from puncture of groin glands.

The tumors are easily enucleated.

In the American infections the tumours are more common in the
regions near the eye and it has been thought that certain cases of
keratitis may be due to onchocerciasis.

DRACUNCULUS MEDINENSIS

The disease caused by infection with this parasite is usually termed dracontiasis and the parasite _Dracunculus medinensis_ or the Guinea worm.

The geographical distribution includes India, Arabia, the West Coast of Africa and Brazil.

_Life History._—The male has not surely been seen in man so that
the pathological condition is entirely connected with the female
worm. Almost invariably the female worm, which measures about
two feet long by 1/12 inch broad, tends to wander down to the
connective tissue structures of the lower extremity. In about 10%
of the cases the worm may present elsewhere, as scrotum, back or
arms. At the posterior extremity there is a sort of anchoring hook.

With the anterior extremity the worm presses against the overlying
skin and causes the formation of a blister-like lesion.

This vesicle later on bursts and, if water is applied to the
spot, a delicate tube, the uterus, is extruded and there exude a
few drops of a milky fluid, which swarms with the sharp-tailed,
striated, sheathless embryos. It is thought that the pouring forth
of embryos, when water touches the part, is in order that the
embryos may reach the water of a pool through which the infected
native may be wading. Once in the water of such a pool, the larvae
are swallowed by _Cyclops_ and gaining the body cavity of this
little crustacean, they continue to develop for about one month.

During this period there are two ecdyses, the first after about two
weeks, when the tail becomes blunt.

When one takes these infected cyclops into the stomach, by drinking water containing them, the cyclops is killed by the gastric juice and the Guinea worm larva breaks out of the dead intermediary host and bores its way through the stomach wall and possibly goes to the tissues about the retroperitoneal region. As a matter of fact we are in ignorance of the exact cycle which goes on, until the fertilized female, with her embryo-distended uterine tube, reaches the lower extremity. A cross section of the female shows the body of the worm to be almost entirely made up of uterus, with an insignificant alimentary canal pressed to one side.

The period of incubation is from 8 to 12 months.

Usually there are no other symptoms than discomfort from the
blister and a feeling of heaviness about the affected extremity. At
times there may be pain and fever. The parasite may fail to gain
exit to the skin surface or die before reaching maturity. In such
cases she may become calcified or give rise to abscess formation.
The _x_-ray plate may show a convoluted cord-like structure with
frequent breaks in the line.

_Treatment._—By douching the point of exit we may cause the uterus to empty itself in about three weeks. At that time we may commence extraction by intermittent traction by winding the worm around a large toothpick or similar object. If undue force is exerted the worm may break off and abscess formation or sloughing result.

Macfie has reported success in treating 23 cases of dracontiasis with tartar emetic. He gave 1 grain intravenously every other day and found that it was not necessary to give more than 6 grains in the course of treatment. The inflammation quickly yielded and the discharge from the sore ceased rapidly.

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The diagnostics and treatment of tropical diseasesChapter XXII: Filarial Infections

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