A man living in a fever region suffered for seven months from intermittent paroxysms. He complained of pain in the left thorax, and manifested objectively an area of dulness below and posteriorly, over which bronchial breathing was audible. Chronic malarial pneumonia was diagnosticated, and the unfortunate man treated for months with quinin. In spite of the fact that the drug had not the slightest influence, the interesting diagnosis was adhered to. Finally a physician was found who doubted its correctness and made a puncture which showed thick pus. By thoracentesis there were evacuated about 1.5 liters of pus bonum et laudabile.
A woman suffered for a year from intermittent fever. Though no change was produced by weeks and months of quinin, and though the patient lived in a salubrious region, the diagnosis of malaria was not relinquished. An examination showed, in addition to the splenic tumor, swollen lymph glands. At the end of the second year the exitus occurred in consequence of lymphosarcoma.
A woman from a malarial region suffered from violent, more or less regular, intermittent paroxysms of fever, mild jaundice, and enlargement of the liver and spleen. Quinin administered for weeks had no influence. In the blood no parasites were found. The anamnesis eventually aroused a suspicion of lues. Potassium iodid produced rapid recovery.
A gentleman from a malarial region suffered almost daily from recurring paroxysms of fever. He had become very pale and emaciated. Wherever he went he was treated with quinin, though without result. In a university town a consulting physician unfortunately discovered pigment in the blood, and the wretched man was fed again with quinin. A renewed examination of the blood by another consulting physician showed every sign of malaria wanting; but a foul smelling discharge from the anus attracting his attention, the question was cleared up by a diagnosis of rectal carcinoma. This case teaches also that the blood examination must be carefully done.
From these few illustrations, which might easily be repeated ten times over, it is evident how little regard is bestowed on the rule that a fever which resists quinin for a long time is not malaria . The only absolute diagnostic characteristic of malaria is the occurrence of malarial parasites in the blood.
The results of expert investigators teach that the parasites may be found in almost every case. In Osier's clinic in Baltimore they were never wanting in 531 cases. The demonstration of the parasite, therefore, is not only of theoretic interest, but of considerable practical value. It possesses at least as much significance in malaria as Koch's bacillus in tuberculosis. The examination of the blood has accordingly become indispensable, and it is to be earnestly desired that the method obtain the widest prevalence not only among physicians practising in malarial regions, but everywhere. Malaria is carried by the infected individual, and under our present conditions of travel it is not difficult for people in Berlin or elsewhere to manifest attacks of pernicious fever acquired in Africa. Moreover, it is a well known fact that physicians practising in regions free from malaria are helpless in regard to intermittent fevers, the causes of which are not evident, and that they too willingly jump at the diagnosis of malaria when a blood examination would solve the question.
The examination of the blood for the purpose of diagnosis may be done at any time during the day or night. Parasites are usually most numerous in the peripheral blood shortly before and at the beginning of the paroxysm. When possible, therefore, this time should be chosen.
If quinin has already been repeatedly administered in large doses, the chances of finding the parasites are much less, since under its influence the ordinary forms succumb and entirely disappear. Laveran's crescents alone constitute an exception. These appear to be absolutely insusceptible to quinin.
If the paroxysms have ceased for several days, either spontaneously or due to medication, the result of the examination is usually negative. This is especially true in cases of infection with parasites of the first group. In cases of parasites of the second group crescents may still be encountered long after the cessation of the fever.
The evidence of pigment is almost the same as that of the parasites themselves. It is only necessary to be sure that the pigment is actually malarial pigment. Black blocks and granules occurring free in the plasma are entirely valueless and without significance. They are foreign particles which contaminate the specimen in spite of the utmost care in preparation. Characteristic only is the reddish black pigment inclosed in leukocytes seen in fresh preparations.
These melaniferous leukocytes are seen during the acute infection, and frequently one or two days after its commencement. Only in cases of infection with parasites of the second group do we find them, like the crescents, a long time after the attack. The rough granules of certain leukocytes which look dark in certain lights must not be confused with pigment. Lawrie's obstinate campaign against the malarial parasites was due to such an error.
It is well for the tyro to study normal blood thoroughly and for a long time under the strongest powers, so that in his search after malarial parasites he will not be confused by every ameboid leukocyte, swarming granule, vacuolated red blood corpuscle, or blood platelet. The beginner had better draw his conclusions only from typical parasites, and leave the pigment to more experienced eyes. Patience will always be rewarded. A single positive malarial parasite is absolute proof of infection.
Negative findings have only relative value, depending on whether the examination was done with sufficient expert knowledge and corresponding diligence. Even when this is true, a negative finding never means as much as a positive. Several preparations should, therefore, be examined at different times. If the examination is continually negative, a puncture of the spleen may be done in very important cases.