“She was so weak that she had to remain in bed till the beginning of April. Since then, after a visit to Crieff, she has improved rapidly, and can now walk two or three miles easily. She now has a fairly good colour, has good appetite, and no pain in the stomach. Examination of the circulatory system shows absolutely nothing abnormal, no dilatation of the ventricles, no arterial, valvular, or venous bruits. The respiratory murmurs and the percussion note of the lungs are normal. The liver is not, and the spleen is, just appreciably enlarged. The blood flows readily from a prick in the finger; it is rich red in colour. The red corpuscles are well-coloured, well-formed, and form rouleaux readily. There is a slight increase in the white corpuscles. Specimens of the blood drawn at 9 a.m., 8 p.m., 9 p.m., 1 p.m., and dried on the slide showed no evidence of filaria of any kind.
“The forearms presented, on the anterior and posterior aspects, slight flattened doughy swellings, which had no definite boundary and were not painful to pressure. There was no alteration in the colour of the skin over them.”
We are still at a loss to account for the entrance of the worm into the body. There are, I think, two different channels by which it might possibly find access. First, by the passage of the embryo filariæ directly through the conjunctiva, being brought in contact with the eye in water used for washing the face or bathing the eye. This I think an unlikely means of entrance, as in my patient special pains were taken to avoid such a possibility, and yet she became affected with the disease, and the power of the worm to penetrate skin or mucous membrane has never been demonstrated. Second, by the swallowing of the embryo filariæ along with articles of food or drink. Although in the case of my patient excellent measures were taken to secure the purity of the water-supply, and although the nature of the food was such as not readily to lend itself to the conveyance of impurities, still I think recent researches, made more particularly by Dr. Manson with regard to the development of the Filaria sanguinis, render it probable that the ova of the Filaria loa are, as suggested by Dr. Manson, taken into the circulation of the patient affected by the mature female parasite. That then some insect of predatory habits, drawing its food-supply from this polluted stream, becomes, in its turn, the host which supplies the necessary elements for the further development of the parasite. This insect, in its turn dying, deposits the embryo filariæ in water, which, being used for drinking purposes, permits the parasite once more to affect man. Which the insect is that probably plays the part of intermediate host is as yet unknown. This view is purely hypothetical, but I think, reasoning from analogy, the most probable one of the development of the Filaria loa.
The geographical distribution of this parasite appears to be a very limited one, as almost all, if not all, of the persons affected, whose cases have been reported, have either been natives of or been long resident on a limited area of the West Coast of Africa, including Congoland and Old Calabar. If Dr. Manson’s view as to the mode of development of the worm be substantiated, then naturally the area of the disease must necessarily be limited to the regions in which the intermediate insect host is to be found.
The fully grown worm may, judging by some of the cases recorded, infest the human subject for a good many years, and may yet not give rise to any very serious symptoms. It possesses very considerable locomotive powers. It is capable of wandering at will from one eye to the other, to disappear into the deeper parts of the orbit, to wander under the skin of the eyelids, and even to make excursions in the temporal region. These seem to be the limits of its excursions. No doubt the Rev. Dr. Nassau (the missionary at the Gaboon) had sometimes sensations of a filaria under the skin of the fingers as well as under the skin of the eyelid, but it is doubtful if this was a true case of Filaria loa, and even then if the worm had made its way from the fingers to the eyelid. At the same time it must be borne in mind that there are few regions of the body in which the skin is so thin as in the eyelids, whereby the presence of a small filamentous body can easily be discerned. The parasite might readily move about under the coarser cutis of other parts and yet escape detection.
The sensitiveness of the parasite to cold appears to be fully established by the experience of my patient and Mrs. H⸺, and it is possible that a prolonged residence in a cool climate may eventually prove fatal to the worm, as seems to have occurred in the case of the Rev. J. L⸺. All the cases previously recorded have occurred in negroes, but those I have brought forward prove that Europeans are also susceptible to the attacks of this worm.
I think I am warranted in saying that the disease is not very rare in the district favoured by the parasite, as, although the number of cases reported is small, the irregular intervals at which the worm comes to the surface, and the slight irritation or annoyance its presence causes, often prevent those affected seeking surgical advice; while it must be admitted that medical assistance is not very readily procured in large parts of the district where cases occur.
The interest connected with the elucidation of the obscure points in the natural history of the worm will, I trust, stimulate those of our profession residing on the West Coast of Africa to undertake the further necessary investigations.
Remarks by Dr. Patrick Manson.—I have no hesitation in saying that I consider the communication to which we have just listened from the President to be one of the most important on the subject of filaria loa that has been made for many years. Two or three years ago I had an opportunity of examining the blood of a number of negroes from Old Calabar in a missionary establishment and elsewhere, and I made the interesting discovery that in 50 per cent. the blood contained the embryos of a species of filaria—Filaria perstans—which were quite different in their zoological characters from the filaria of the blood, with which every one must now be familiar. While examining one of these patients whose blood contained this new species of filaria I found another species of bloodworm, whose anatomical features were similar to those of the ordinary Filaria sanguinis, but which presented a very great difference physiologically, inasmuch as contrary to what is observed with the ordinary filaria, this one disappears at night and can only be found in the blood during the daytime. This second new bloodworm I therefore called Filaria diurna. Some time later, in a communication which I had from Professor Leuckart, he told me he had been enabled to examine the embryos in the uterus of an adult Filaria loa, and he sent me a sketch of these embryos. On comparing this sketch with the Filaria diurna, I came to the conclusion that they were practically identical, and therefore that the filaria I had found in the blood of the negroes might possibly be the embryos of Filaria loa. This opinion appeared to me to be strengthened by the fact that this patient had previously had a loa under the conjunctiva. I have very little doubt that the embryo of Filaria loa finds its way into the blood. Clinically, there is no evidence of its attempting to find its way to the surface of the body, and it is evident that there must be some arrangement by which it can get out of the body, and so propagate its species by passing from one person to another. From this and other considerations I consider that it must be by way of the blood that the necessary escape is effected. With the ordinary filaria it is now well known that the mosquito removes it from the blood and acts the part of intermediate host, and I suppose that a similar arrangement must exist in respect of the Filaria loa. On inquiring of the Old Calabar negroes as to the blood-sucking insects of the district, I learned that there was a particular fly which exists in great numbers about the creeks, and was very annoying on account of its pertinacity. I think this insect, which is also diurnal in its habits, is probably the intermediate host for the Filaria loa, us the mosquito is for the ordinary filaria. I do not believe that this individual worm was the only Filaria loa in the body of the patient whose history we have just listened to. It became visible simply because it wandered to a spot where it could be seen; elsewhere in the connective tissue I opine there are others. The patient was first seen in February, and whether sufficient time has intervened for the maturation of these parasites and the evolution of their embryos I cannot say. None, it is true, were found in the blood, but the specimen was a male, and from this it is impossible to say what the degree of maturity the embryos of any females present may be. I think the blood should be examined again, and I would suggest that if possible a similar examination should be made of the other members of the mission, and of the patients the President referred to. The locomotive habits and sensibility to cold of this parasite are particularly interesting in respect of the way in which they subserve its interests, on which they certainly have a bearing. The measurements of the Filaria loa usually given, as ascertained by looking over the literature of the subject, are from 17 mm. to 70 mm. The smaller measurements are explained by the author’s case; they apply presumably to the male parasite, which in the filaridæ is almost invariably smaller than the female. One measurement given, 15 cm., is so enormous that I question the accuracy of the observation, or, if the measurement were exact, it must have referred to some other parasite than Filaria loa. With respect to the nature of the protrusions from the body of the parasite under the microscope, one of them is certainly the alimentary canal; the other is probably the testis ruptured in two. One must be careful in coming to a conclusion about these and similar connective-tissue parasites. There are four or five whose young inhabit the human blood; and there are others whose young appear to have a different history. Especially in West Africa do we find such parasites. There is the guinea-worm, said, however, not to be found in Old Calabar; it certainly is found in the neighbourhood; its name signifies an African origin. There is the Filaria perstans, the Filaria nocturna, and also a very minute bloodworm, Filaria demarquayi, the parental form of which, as of F. perstans, has not yet been found. There is the Filaria volvulus, which resembles the Filaria loa, in that it lives in the subcutaneous cellular tissue. Not long ago Professor Magalhães, of Rio Janeiro, described a species of filaria which he found in the left ventricle of the heart, which is also probably a new species. It follows, therefore, that before venturing on the diagnosis from specimens of parasites found in the blood or connective tissues, usually more or less mutilated, one requires to be very careful. One singular fact about the Filaria loa is that it will not live in the West Indies. It has been introduced many times, but does not spread. It has been removed from the eye there from imported negro slaves, but it has not become acclimatised. In this respect it resembles very closely the Filaria medinensis (guinea-worm), which was introduced times without number during the days of slave importation into the West Indies, yet it has died out altogether except in one or two places, the island Curaçao and a limited district in Brazil. This undoubtedly is in consequence of one of two things; either the habits of the people, or the absence of the proper intermediate host. In respect of the guinea-worm the intermediate host is a fresh-water cyclops. I recently had a case in the Seamen’s Hospital from which I was enabled to procure the embryos. This enabled me to carry out some experiments which I would urge upon those who have the opportunity to repeat. When the guinea-worm arrives at maturity a little vesicle or bulla is formed on the ankle or foot. The vesicle ruptures, and on careful examination you will see a small orifice in the centre in which sometimes the head of the worm may be seen, but not always. If you take a sponge and drop some cold water, not on, but in the neighbourhood of this orifice, you will see the hole become filled with a white grumous material, which under the microscope, and on adding a little water, is seen to be a wriggling, writhing mass of embryos. The application of water to the leg after an interval may lead to further extrusion of embryos. This is a striking illustration of the curious way nature has adapted the habits of the guinea-worm to its requirements. The young guinea-worm lives in water, and probably for this reason the mature worm descends to the feet or ankles, the parts of the human body in tropical countries most often within reach of water. Having procured in this way a supply of embryos, I tried to repeat the experiment described by the Russian naturalist, Fedschenko, on the metamorphosis of the embryos of the guinea-worm in its intermediate host. I obtained some fresh-water cyclops and placed them in water with the embryos. After five or six hours I took one of the cyclops and placed it under the microscope, and I found the body-cavity to contain twenty or thirty of the living and moving embryos. The next day, however, the cyclops were all dead, but the contained embryos were all lively. Having still one or two of the cyclops left I repeated the experiment, but, proceeding more cautiously, placed only a few of the embryos in the water along with the cyclops. After a few hours I removed the cyclops, and found that each of them had two or three guinea-worm embryos coiled up or moving about in their insides. Two of the cyclops I kept alive; one lived sixteen days and the other five weeks, and during this time the embryos could be seen moving and developing. At the end of five weeks I killed the cyclops, and I found the guinea-worm embryos had undergone a certain degree of development. The outer cuticle of the embryo had separated a good deal from the body—ecdysis, and there were certain changes in the alimentary canal. I have no doubt that had the cyclops been in a normal condition as regards exposure to light and sun, the metamorphosis of the guinea-worm inside the cyclops would have been completed. This shows that it would be possible to introduce the guinea-worm into England if we did not wear boots or shoes, and if we were in the habit of wading about in pools and marshes as do the natives of West Africa. There would be a discharge of the embryos into the water, and if less care were taken about the purity of the water-supply, and supposing there to be no adverse climatic influences, the worm would become common. This little story about guinea-worms shows how these and similar parasites pass from one man to another; and it shows how slight differences of habit, absence of intermediate host, and so on, govern the distribution of a parasite like Filaria loa. If you examine this Filaria loa exhibited by the President under the microscope, you will see that all over the skin there are minute but regular bosses or protuberances. This occurs in certain filariæ, but in no other human species so far as I am aware. These protuberances, I have no doubt, have a bearing on the locomotive habits of this particular parasite. I pass round a reproduction by Blanchard from a book which carries us back a century further in the history of the Filaria loa than that given by Dr. Robertson. This book was written by Pigafetta,[8] and it contains a picture showing a man drawing a guinea-worm out of his leg, and a woman having a worm removed from the eye, doubtless a Filaria loa.