Watch out for the symptoms! / by Nicholas J. White

watch for the symptoms! alaria is the most important of the parasitic diseases that afflict man- kind . Whereas many of the other human parasites seem happy to live in relative harmony with their hosts, the parasites of Plas- modium falciparum (one of the four species of malaria) have a tendency to multiply rapidly and in an uncontrolled way in their human hosts, which may prove fatal. The disease is acquired when a biting female anopheline mos- quito takes a blood meal. Whilst 8 by Nicholas J. White probing for blood she injects the microscopic parasite which then finds its way to the victim's liver. There it invades a few of the liver cells and develops over a period of one to two weeks. During this period the human host is blissfully unaware of the infec- tion. At the end of this incubation period, the infected liver cells rupture and release a much increased number of parasites into the blood stream, where they rapidly invade the circulat- ing red blood cells. Once inside the red cell, the malaria parasite proceeds to consume the contents of its new home and to grow. At the end of a further two days (or three in the case of Plasmodium malariae) the destroyed cell bursts, releasing more parasites which immediately invade more red cells. Thus the infection expands and within a week the victim begins to feel ill. The symptoms of malaria depend very much on the amount of previous exposure to the disease and thus on the level of background immunity. In (Above) Mosquitos breed wherever there are stretches of still water. W ORLD HEALTH. September-October 1991 @ many parts of the tropics, particularly -£ in Africa, transmission of falciparum J malaria is intense, and everyone is - infected repeatedly. Children may get ~ severe malaria in the first few years of ~ life but gradually, with repeated infec- o tions, most of them develop immunity. 'Q By the time they are adults, they no 9 longer show malaria symptoms. In 8 these areas, malaria is a major cause of i childhood death. Furthermore, the hard-fought-for immunity of the survi-~ij«~ vors is easily lost if the subject leaves a :; malarious area. In other areas of the ;;: world, the transmission of the disease ~ is less intense and symptoms develop at any age. Flu-Hke symptoms The first symptoms are a vague feeling of being unwell and weakness, followed by fever. This is often accom- panied by headache and muscular aching. Nausea, vomiting and abdomi- nal pain may occur. At this stage the symptoms are indistinguishable from mild flu (influenza), and the patient may not seek medical advice. The dangerous falciparum malaria may progress in several ways; the most characteristic sign of severe infection is ::» unconsciousness (cerebral malaria). ~ This is a serious disease and one in five ~ patients will die from it. Coma begins cJi suddenly, usually following a gen- o eralized convulsion, or more gradually ~ as the patient becomes confused, ~ delirious, and finally cannot be wak- f ened. In children, the deterioration may be rapid. A child who was "off-colour" in the morning may be unconscious by the evening when the mother returns from the fields, and may be dead by the following morning. Cerebral malaria is a medical emergency which calls for urgent referral to hospital or health centre, so that antimalarial drugs and glucose can be given and further convulsions prevented. Malaria destroys the red cells of the blood, and anaemia develops rapidly. This is a particular problem in childhood and during pregnancy. The patient appears pale and lethargic and may require a blood transfusion (with all the attendant risks of transmitting viral infections such as hepatitis B or AIDS). Other signs which may develop are jaundice, in which the eyeballs look yellow. Rarely, if the patient takes quinine, the urine may become dark coloured or black (blackwater fever). In adults with severe malaria, the kidneys may fail and the patient will need to have dialysis to survive. Renal failure is usually reversible, but the mortality rate is high. W ORLD HEALTH, September-October 1991 (Above) Quick action is needed when- ever malaria is suspected; some forms of the disease can kill within hours_ (Below) Bouts of malaria prevent chil- dren going to school, and interrupt their education. Malaria has a reputation for causing teeth-chattering chills and shakes (what used to be called ague), with a splitting headache and high fevers which occur at exactly the same time every one or two days. This "synchro- nization" of the infection does take place eventually (particularly with P vivax, malariae, or ovale-the malarias which very rarely prove fatal) . But it takes several days of less regular fever before synchronization takes place, and falciparum malaria may never synchronize. Nowadays treatment is usually given well before this develops. The pattern of fever is therefore not very helpful in making a diagnosis. All malarias have a tendency to recur. In falciparum malaria, this usually happens within weeks of treatment and represents a "recrude- scence" of the original infection, which has not been cleared from the blood- that is, because treatment has failed. With P vivax and P ovale, true relapses occur months, or rarely years, primary infection. This is because some of the parasites lie dormant in the liver (these are called hypnozoites or sleeping forms). Relapse or recrudescent infections cause the same symptoms as the primary attacks. Mosquitos need water in which to breed; so the habits of the local anopheles mosquito vector are what determine the geographic pattern of disease. In many parts of the world, the disease is much more common in the rainy season as mosquito numbers increase. Malaria is a particular problem in young children and in pregnancy, where it affects both the mother and her unborn baby. Severe malaria is commonly found where people migrate to a malarious area from a non-malarious area-refugees , travellers, itinerant woodcutters, gem miners, soldiers and so forth. Death can usually be prevented by prompt treatment-but the key to this is recognition and the general availability of effective drugs. All too often one hears of returned travellers--especially tourists-who thought they had a bit of flu and could "shake it off' and a day or so later are found unconscious at home; or a child with a slight fever who will not eat or play normally, and then has a generalized convulsion followed by coma. • Dr Nicholas J. White is Director of the Wellcome/ Mahidol University/Oxford Tropical Medicine Research Programme. 420/6 Rajvithi Road. Bangkok 10400. Thailand. 9