# Tropical Diseases/Chapter 7

CHAPTER VII
MALARIA: DIAGNOSIS
THERE is a marked tendency to regard and diagnose all fevers occurring in tropical countries, or in individuals who have returned from tropical countries, as malarial. Such slovenliness in diagnosis must be strenuously avoided by the practitioner. It is apt to become a habit which, sooner or later, is bound to have disastrous consequences.
At the same time the opposite error of overlooking malarial infection must be equally guarded against. In many tropical and sub- tropical localities practically every European is, or may be, the subject of active or latent malaria. The tropical practitioner therefore should approach the diagnosis of all his cases, no matter what, with the idea ever present to his mind that they may be malarial or complicated with malaria.
The three pathoguomonic signs of malaria.—— These are—— periodicity; the effect of quinine; the presence of the malaria parasite.
The diagnosis of malarial disease, if all the means at our disposal be employed, is usually not a difficult matter. Formerly, periodicity and the effect of quinine were the tests principally relied on. In certain circumstances they are fallible. Nowadays, in all doubtful and serious cases, it behoves the practitioner to have recourse to the least fallible test—— the microscopical examination of the blood. When such an examination yields a positive result, when the parasite in any of its forms, or its characteristic product—— hæmozoin—— either free in the liquor sanguinis or enclosed in leucocytes, is found, the diagnosis of malaria is securely established. Negative results from a single microscopical examination are not so trustworthy as ​positive; but if the practitioner has experience, and if he has the opportunity to make his examinations at suitable times and in a case untreated by quinine, they, too, are conclusive, more especially if supplemented by a differential count of the leucocytes.
The quinine test is generally conclusive in intermittents and in the various larval forms of malaria, but the more severe types of remittents are often singularly resistant to the drug. Moreover, time may not be available in which to test such cases with quinine. They may be cases of a threatening nature in which a speedy diagnosis is of the first importance. In such cases the microscope is the only available trustworthy diagnostic agent.
Periodicity in diagnosis.—— Periodicity at times is a trustworthy enough clinical test for malarial disease. Tertian and quartan periodicity occur only in malarial disease; when either is thoroughly established, its presence is almost conclusive as to the case being malarial. It is otherwise as regards the significance of quotidian periodicity. Quotidian periodicity we find in greater or less degree in nearly all fevers, particularly in fevers associated with suppuration. In hectic conditions quite unconnected with malaria one often sees a quotidian afternoon rigor, followed by hot, dry skin, and a temperature rising even to 103° or 104° F., the febrile movement concluding with a profuse diaphoresis and complete morning apyrexia. Such cases are apt to be misdiagnosed and treated as malarial.
Periodicity of fever in liver abscess; diagnosis from malaria.—— Particularly is this the case in suppuration connected with the liver a condition peculiarly liable to occur in tropical practice. Simulation of malarial fever by hepatic abscess is very common; it is a pitfall into which the inexperienced tropical practitioner often tumbles. In consequence, we find that, at one time or another, most liver abscess cases are drenched with quinine, on the supposition that the associated fever is malarial. There are several points, even apart from an exam​ination of the blood, which, if duly considered, will avert this blunder.
In hepatic abscess, although the liver is enlarged, the spleen is not necessarily so; splenic enlargement, though an occasional, is not a usual feature in liver abscess. In malarial fever if the liver be enlarged the spleen is still more so, and usually can be felt extending well beyond the costal margin. In hepatic abscess the fever occurs generally, though not invariably, in the late afternoon or evening; the patient may perspire profusely, independently of fever lysis, at any time of the day or night—— very generally whenever he chances to fall asleep. In malarial fever the paroxysm may, and generally does, occur earlier in the day; there is no marked tendency to sweating unless at the defervescence of the fever. In hepatic abscess a history of dysentery is nearly always obtainable if carefully inquired for. If fever be distinctly tertian or quartan in type it is not hepatic. In all doubtful cases the blood must be examined once or oftener, the rigor stage or early hot stage being selected for the examination, and the examination being made before administration of quinine. Apart from the presence or absence of the parasite or of pigmented leucocytes, marked increase of polymorphonuclear leucocytes would be in favour of hepatic abscess; a relative excess of mononuclear leucocytes in favour, though not conclusive, of malaria. Occasionally cases are met with in which there is a history of malarial infection and, in addition to this, a history of dysentery, and the liver and spleen are both enlarged. In such cases diagnosis may be impossible without the microscope and the aspirator.
Diagnosis of bilious remittent from yellow fever.—— In bilious remittent the icteric tinting of the skin is an earlier feature; albuminuria is not so common and generally not marked; temperature is maintained high for many days, not subsiding in three or four days as in yellow fever; the vomiting is profuse and bilious; the pulse does not become phenomenally slow as in yellow fever; in the initial ​stage the eyes are not congested and shining to the same degree; and, of course, the parasite is to be found in the blood.
Diagnosis from other types of paroxysmal fever.—— The following also are often mistaken for malarial fever: Cerebro-spinal meningitis; urethral fever; the fever attending the passage of gall-stones, or with inflammation of the gall-bladder; that associated with pyelitis and surgical kidney; lymphangitis, particularly that form of lymphangitis associated with elephantiasis and other filarial diseases; undulant fever; relapsing fever; trypanosomiasis; kala-azar, generally an irregular fever, though often quotidian, and almost invariably attended with enlarged liver and spleen and with anæmia; the fevers associated with tuberculous disease, with ulcerative endocarditis, with some types of pernicious anæmia, with splenic leucocythæmia, especially with visceral syphilis, with rapidly growing sarcoma, with forms of hysteria, and with many obscure and ill-defined conditions. The use of the microscope must not be neglected in such cases if there be the slightest doubt as to their exact nature.
It must not be concluded that, although unquestionable evidence of the presence of one or more of the foregoing has been obtained, malaria is absent. Malaria often concurs with these diseases. Malaria is a common complication in trypanosomiasis, for example, and it is often hard to pronounce as to whether in such cases any given rise of temperature be due to the trypanosoma or to the malaria parasite. The same may be said of tuberculosis, of syphilis, and, in fact, of any medical or surgical condition.
Typhoid and paratyphoid fevers.—— With out the microscope it is sometimes impossible to diagnose typhoid types of malarial fever from genuine enteric. In both there may be diarrhœa or constipation; in both there may be splenic enlargement; in both there may be typhoid tongue, delirium, and the entire range of typhoid symptoms. As a matter of fact, until recent years all typhoid in India was regarded and treated as malarial fever—— malarial ​remittent and, doubtless, often with disastrous results. In circumstances in which the Widal test or blood culture is available, either is an invaluable supplement to microscopical examination of the blood.
Typho-malarial lever.—— One important fact in connection with the diagnosis of typhoid in malaria must ever be kept in mind. In individuals who have previously been subjected to malarial influences and who, perhaps, have suffered at one time from well-marked malarial fever, the oncoming of typhoid is often preceded by three or four paroxysms exactly like those of ordinary ague. This may occur even when the patient has been for some time in a nonmalarial country, as England. In such cases quinine is usually given early in the attack; its failure to check the disease should lead to careful prognosis and the avoidance of too active purgation. Similarly, well-marked malaria-like fluctuations of temperature and the appearance of the parasites in the blood in the course of a continued fever do not exclude typhoid. These cases are probably typho-malarial, and have to be treated as such as typhoid with a malarial complication.
Necessity for microscopical examination of blood in pernicious attacks.—— Without the microscope it is sometimes impossible to diagnose, in time to direct appropriate treatment, pernicious comatose malarial attacks from heat-stroke or, if algide in character, from ordinary apoplexy; malarial dysentery, which must be treated with quinine, from ordinary dysentery, which must be treated with emetine, or ipecacuanha, or with the sulphates; algide malarial attacks, from cholera; certain types of malarial fever occurring, as they are very apt to do, in the puerperal state, from puerperal fever; malarial pneumonia, from croupous pneumonia; malarial aphasia, from the aphasia of organic brain disease; and so on.
It is manifest that the revelations of the microscope have enhanced our powers of diagnosis in malarial affections enormously, and, therefore, our powers of treatment. Every doubtful case must be ​tested by it. In many forms of malarial disease, if life is to be saved, action must be prompt, decisive, energetic, and based on accurate diagnosis. The diagnosis of ordinary agues may be postponed for a day or two without much danger, and be made correctly enough without the microscope; but every now and again a pernicious attack is sprung upon the practitioner, the nature of which he must be able to recognize at once, and recognize with confidence. When the parasite is seen in the blood, it is surely known that there is a malarial element in the case and that quinine is indicated. Confidence in directing treatment is a great matter. It cannot, therefore, be too strongly urged on the tropical practitioner to avail himself of every opportunity to gain experience in the use of the microscope in blood examinations, and to take care to have a suitable instrument in working order and available at a moment's notice. The practical difficulties in carrying out this recommendation are insignificant in comparison with the importance of the results. With practice, five minutes usually suffices to effect a positive microscopical diagnosis of malaria.
Every tropical practitioner should be provided with a travelling microscope, or, at least, carry about with him a few microscope slips for blood films. He must be on his guard, however, against concluding from the discovery of malaria parasites in his films that malaria is necessarily the only, or even the principal, disease his patient is suffering from.