Diagnosis of Malaria in West Africa
Authors: D. G. Ferriman
Journal: BMJ (1945)

This paper is based upon experience of over 2,000 cases of malaria in white personnel at an R.A.F. hospital in West Africa. The type was almost exclusively malignant tertian. The vast majority of patients had not been exposed to infec tion prior to service in West Africa, and their stay was com paratively short. Drug suppression and antimalarial discipline were in force. Owing to a big drainage scheme and efficient screening, the infection rate, though not low, was less than in many places on the coast. Patients were nearly always admitted to hospital in an early stage of the disease. Per nicious cases were uncommon ; only 9 of blackwater fever, 4 of cerebral malaria, and 1 of the choleraic type were seen, all of which recovered. No algid case presented. Chronic malaria was very uncommon ; not more than 6 cases were seen. M.T. malaria closely mimics many diseases ; it is dangerous, and parasites are not always found in the blood. Treatment, therefore, often has to be on suspicion. However, it is possible to become a little obsessed with the diagnosis when malaria accounts for no less than two-thirds of medical admissions? with results which are not always happy. The following is an account of matters found helpful in diagnosis. Cases of malaria will be referred to as proved (or slide-positive) and clinical (or slide-negative), depending upon whether parasites were or were not found in the blood stream. Diagnosis was often helped by a short period of observation. Grave complications, how ever, are so liable to arise in seriously ill cases of malaria that treatment was not delayed in any serious febrile illness unless the clinical picture pointed definitely to a non-malarial disease. For routine purposes a temperature of 103? was taken as an objective dividing-line between seriously and not so seriously ill cases ; these will be referred to as highand low-fever cases respectively. In the great majority of low-fever cases it was found possible to reach a shrewd diagnosis within 48 hours ; for the remainder, a working rule was adopted that antimalarial treatment should be tried when doubt still existed at the end of 4 days. Pathological Diagnosis Antimalarial therapy was started on finding a positive blood slide. Slides were taken on admission, before starting treat ment, in all cases. The following trial was made to determine the optimal delay for blood slides in low-fever cases. Treat ment was withheld in 136 virtually consecutive low-fever cases of suspected malaria?indefinitely in the first 71, and then for four days in 65. Blood slides were taken on admission, and night and morning. Ninety cases revealed parasites?66 in the first slide, 14 more within 24 hours, and 6 more within 48 hours ; only 4 showed parasites at longer intervals. It was concluded that delay beyond 48 hours for this purpose was of little value. The figures are very similar to those in a series of 968 reported by Hughes and Bomford (1944) from another West African Service hospital. Slides were taken night and morning for 48 hours in high-fever cases even though treat ment had been started, since it was found that parasites still appeared in an appreciable number of cases. In B.T. malaria parasites are most easily found on the rise of temperature in each rigor. Such typical, rises are not common in M.T. malaria. Slides were taken in those which did occur, but parasites were by no means always found. Suppfessive therapy was stopped while diagnosis was under consideration. It was started again as soon as malaria was thought excluded (i.e., a maximum suspension of 4 days). Malaria parasites are harboured somewhere after an attack, possibly in the bone marrow. Until it is known that they can not be found in the marrows of parasitized but symptom-free men a positive marrow smear cannot be accepted as diagnostic of active disease. Even were this the case, the number of blood-slide-negative cases of suspected malaria was far too great to justify the routine use of sternal puncture in West Africa. It was tried in a few such cases out of scientific interest, and parasites were sometimes seen. Clinical Diagnosis A number of clinical features were believed to assist in diagnosis. Splenomegaly was a very strong pointer. Other causes were rare. Admittedly 5% of 219 cases on the station had splenomegaly, and could be admitted with non-malarial illnesses, but this would hardly have accounted for more than 1 to 2% of admissions. The percentage, however, in febrile cases admitted to the medical wards was very much higher? approximately 25% of 406 consecutive cases. Tenderness of the spleen was virtually pathognomonic, and definite tender ness under the left costal margin, in the absence of a palpable spleen, came to be regarded as of great diagnostic value. The anomalous behaviour of many cases of malaria super ficially resembling other diseases was very helpful. Deteriora tion was of great assistance ; the common non-malarial illnesses concerned in differential diagnosis (febrile catarrhs, simple enteritis, and dysentery) tended to recovery, and that fairly rapidly. Another valuable pointer was in the time relations between constitutional and local symptoms. In the usual non malarial illnesses the onset might be with constitutional symp toms only, but local ones soon followed which persisted after disappearance of the former. In enteritis, for example, onset might be with 12 to 24 hours' headache, but the subsequent diarrhoea outlasted the headache by several days. In malaria, constitutional symptoms often preceded the local ones by days or persisted after their disappearance. The typical tertian periodicity of fever and symptoms was helpful when met, but unfortunately was not particularly common. Incidentally actual rigor was very uncommon and usually heralded blackwater fever. The combination of the symptoms of two non-malarial diseases, such as coryza and diarrhoea, was felt to indicate malaria. Two other points were of limited value. The degree ofconstitutional disturbance and the duration of illness might be incompatible with the non-malarial disease concerned. Thus a case with severe headache, a temperature of 105?, and coryza was hardly likely to be a febrile catarrh ; such obvious cases were, however, exceptional. The likelihood of malaria varied considerably between the various presenting symptom-complexes, and this was of much help in diagnosis. Very many cases presented with symptoms an signs of a general nature only. These included head ache, backache, aching limbs, dry cough, vomiting, fever, splenomegaly, and herpes. They will be called constitutional cases. It was believed that all such cases should be regarded as malarial, positive slides or not, unless definite reasons appeared to the contrary. They were indistinguishable from proved cases. No common satisfactory alternatives existed ; some form of heat exhaustion or an unknown virus was a possible cause, but little or no evidence existed for either. A number got worse or failed to recover until given antimalarial therapy. Others apparently recovered without, but of these an undue proportion returned shortly after discharge in frank attacks of malaria ; splenomegaly was seen to subside with out treatment in a case or two of this type. Constitutional symptoms might usher in many diseases which later declared ' themselves by local symptoms ; such possibilities had to be excluded by a short period of observation. An analysis of the symptom-complexes in 345 consecutive cases of proved malaria was rather instructive. Results (to the nearest 0.25%) are given in Table I. Four symptom-complexes