1896.] 
NATURAL SCIENCES OF PHILADELPHIA. 
271 
REMARKS ON FILARIA. 
FREDERICK P. HENRY, M. D. 
The case which is the basis of my remarks belongs to one of a 
group of diseases included under the generic term “ filariasis,” by 
which is understood an affection caused by one or other species of 
Filaria. This parasite is by no means rare in the lower animals, 
e8j>eciully in the dog, but I will confine my remarks to those Filariee 
which infest the blood of man. Of these, three species are univer- 
sally recognized : (1) Filaria sanguinis hominis noctuma, (2) Fil- 
aria sanguinis hominis divrna, (3)Filaria perstans. This classifica- 
tion is based upon the habits of the filarial embryos, the first species 
being found in the suj>erficial vessels solely or chiefly during the 
night; the second solely or chiefly during the day, while the third 
is constantly present in the cutaneous capillaries. 
There is a fourth species recently discovered by Dr. Patrick 
Manson, formerly of Amoy, China, now of London, which he has 
modestly named Filaria Demarquayi, after Demarquay, the dis- 
coverer of Filaria noctuma. 
Filaria diurna and Filaria perstans are confined thus far to the 
West of Africa and adjoining districts, while the Filaria noctuma is 
widely prevalent in the tropics and endemic in certain sections of the 
United States. The adults of Filaria noctuma have been frequently 
found ; that of Filaria perstans never, so far as I have been able to 
ascertain. In the opinion of Manson the Filaria loa of the eye of 
the negro of Old Calabar is probably the adult form of the Filaria 
diurna. If it is not, he argues, then there must be another blood 
worm yet to be discovered, for the embryos of the loa must escape 
from the body of their host through the medium of the circulation. 
Filaria perstans has been practically proved by Manson to be the 
cause of the fatal “ sleeping sickness” of the Congo region. 
While engaged in the study of filariasis my attention was called 
by I)r. Charles A. Oliver of Philadelphia, to a remarkable case of 
Filaria loa recently reported by Dr. Argyll Robertson, the distin- 
guished ophthalmologist of Edinburgh. The patient was a lady 
who had spent eight years in missionary work at Old Calabar on 272 
PROCEEDINGS OF THE ACADEMY OF 
[1896. 
the West Coast of Africa. Without entering into the details of this 
most interesting case I will merely state that in two successive 
operations Dr. Robertson extracted two Filarise (species loa) from 
the ocular tissues, the first a male the second a female. Both of 
these adult parasites are described by Manson in the course of 
Robertson’s paper. The female was stuffed with embryos but 
repeated examinations of the blood failed to detect any embryonic 
Filarise in that fluid. This fact seems to refute Dr. Manson’s hypoth- 
esis that Flaria loa is the adult form of Filaria diurna. 
The fact that the case on which my remarks are based is the first 
of the kind observed in Philadelphia justifies the publication of a 
life-history of the parasite, Filaria nocturna, which I found in the 
blood of my patient and of which living specimens are placed under 
the microscope. I wish, therefore, to emphasize the fact that Filariae 
in the blood vessels are undeveloped, embryonic, and that they are 
the progeny of an adult, two or three inches long, which has its 
permanent abode in one of the lymphatic channels, probably the 
thoracic duct. Manson, observing the embryonic characters of the 
circulating Filarise, came to the inevitable conclusion that they must 
reach a further stage of development outside of the body and, in all 
probability, in the interior of some blood-sucking animal. He 
naturally thought of the mosquito, an insect whose nocturnal blood- 
sucking habits seemed to render peculiarly fit to act the part of 
intermediary host. Without entering into details I will merely say 
that Manson’s hypothesis was fully verified by experiment. 
In the case of Filaria diurna it is conjectured that certain blood- 
sucking flies of Old Calabar known as Mangrove flies play the role 
of intermediary host. 
The mode in which the embryos of Filaria perstans are supposed 
to escape from the human body is equally interesting, although it does 
not involve the agency of any blood-sucking insect. In the region 
in which Filaria perstans is endemic there prevails a skin disease 
called “ craw-craw ” attended with pustules, in the contents of which 
Filarise have been found. It is supposed, with great probability, 
that the embryos escape with the rupture of the pustules and, in 
some as yet unexplained manner, although probably through the 
medium of drinking water, gain access to the human system in 
which one, or more, attain maturity. It must be confessed, how- 
ever, that our knowledge of the life history of Filaria perstans and 
Filaria diurna is based more upon analogy than fact and that this 1896.] 
NATURAL SCIENCES OF PHILADELPHIA. 
273 
will probably continue to be the case until some Manson takes 
residence in West Africa. 
The presence of Filaria embryos in the blood does not necessarily 
give rise to disease, their transverse diameter inch) being as a 
rule such as to enable them to traverse the narrowest channels of 
the blood and lymph. Occasionally, however, they occlude these 
vessels and this is due to the fact that the embryos are prematurely 
born enclosed in a sac or sheath of globular form, the transverse 
diameter of which is about inch. Disease in man occasioned 
by the Filaria is, therefore, the result of disease in the Filaria itself- 
If the adult female Filaria produces the young in a physiological 
manner they are innocuous to their host; if, through disease or 
irritation, she brings them forth prematurely, they obstruct the lymph 
channels and produce one or more of the diseases grouped under the 
title of filariasis. According to Manson, “ it is very certain that in 
the great majority of instances in which the blood is infested with 
Filarire, no harm whatever accrues.” 
The principal diseases to which the Filaria gives rise are abscesses, 
lymphangitis, dermatitis and cellulitis, erysipelas, orchitis, chyluria, 
chylous dropsy of the peritoneum, chylous dropsy of the tunica 
vaginalis, varicose groin glands, lymph scrotum and elephantiasis. 
The disease or rather the symptom that induced me to search for 
the Filaria was chyluria, which is not a common manifestation of 
filariasis even in the tropics. 
It is an interesting fact that the diseases to which the Filarise give 
rise are entirely due to mechanical interference with the circulation 
of lymph and blood ; no toxines, or at least none inimical to man 
seem to be generated by this parasite and this fact is in marked 
contrast to what is observed in the ordinary infectious diseases. In 
the latter, as is well known, the products of bacterial activity are 
intensely toxic. I would venture to suggest, in explanation of this 
anomaly, that excretory products diminish in toxicity to man in 
direct ratio with the ascent in the scale of being of the organism 
that discharges them. 
The most remarkable fact in connection with the habits of Filaria 
nocturna is that it is found in the superficial capillaries solely 
or chiefly during the evening and night. On several occasions I 
have examined the blood of my patient at noon or thereabouts and 
have found the parasites either absent altogether or very sparsely 
present; whereas at night they have always been abundant. This 274 
PROCEEDINGS OF THE ACADEMY OF 
[1896. 
“ filarial periodicity,” as it is called, has been carefully studied by 
Manson who found that toward sunset the embryos “ begin to enter 
the general circulation. Gradually, as the night wears on, their 
numbers increase. About midnight they are most numerous. As 
morning approaches they get fewer and fewer, and by 8 or 9 A. M. 
they have disappeared.” This periodicity is wonderfully adapted 
to facilitate the escape and further development of the embryo 
through the medium of the mosquito. Various theories of the cause 
of “ filarial periodicity ” have been advanced but none of them is 
entirely satisfactory. The most satisfactory of them is that which 
correlates the habits of the parasite with the sleeping and waking 
habits of the host. This, however, is simply reiterating the fact 
without explaining it. That the approach of the embryos to the 
surface is not entirely due to the somnolent condition of the host is 
shown by the fact that it begins several hours before bedtime; 
while, on the other hand, the parasites begin to retire to the deeper 
vessels hours before the usual hour of rising. It cannot be denied, 
however, that the condition of sleep has something to do with the 
approach of the Filaria to the surface. This is proved by a celebrated 
experiment of Dr. Stephen Mackenzie who induced a patient who 
harbored the Filaria nocturna to reverse his usual habits as to sleep- 
ing and waking: i. e. to remain awake all night, and sleep during 
the day. While this experiment was in progress the Filaria was 
found in the surface vessels solely or chiefly during the day. The 
fact that the embryos begin to find their way to the surface several 
hours before bedtime would seem to indicate that the systemic condi- 
tion which induces sleep is chiefly vascular and that it is of gradual 
development. 
The refuge of the embryo of Filaria nocturna during the day has 
not, as yet, been discovered. The embryos of Filaria immitis, a 
parasite of the dog, observe a modified periodicity and when fewest 
in the surface vessels are found in enormous numbers in the blood 
vessels of the lung. This is not the case with Filaria nocturna 
for Manson has examined blood expectorated from the lungs of a 
Filaria patient by day without finding the embryos and Myers has 
examined blood withdrawn by aspiration from the spleen and liver 
during the day, with negative results. 
I have elsewhere1 discussed the question of the treatment of 
1 Medical News, May 2d, 1896. 1896.] 
NATURAL 8CIENCES OF PHILADELPHIA. 
275 
filariasis and will, therefore, confine myself to the statement that 
there is no drug that will kill the adult parasite, and that even if 
such a drug were known it would he wisest to refrain from its em- 
ployment. When the adult worm has its seat in one of the extrem- 
ities and dies, an abscess usually results; or it is perhaps more 
correct to say that adult Filarise have been found in such abscesses, the 
presumption being that the latter are caused by the former. If, 
however, the adult Filaria dies in the thoracic duct, with consequent 
abscess, the result would be of necessity fatal. The only treat- 
ment worthy of the name is prophylaxis. Filaria nodurna being 
introduced into the system through the medium of drinking water, 
it is of vital consequence, in the countries in which filariasis is 
endemic, to secure a pure water supply by filtration or other means. 
As Manson remarks’; “ the ultimate disappearance of the filarial 
diseases is entirely a matter of personal and municipal education”— 
in other words of “ civilization .... and if any municipal 
or other body is in want of one more argument for a pure water sup- 
ply, here is one ready made to their hands.” 
1 Davidson’s Hygiene and Diseases of Warm Climates,