Malaria

Introduction

Malaria is one of the major scourges of mankind in the developing world. It is estimated to affect more than 500 million people causing between one and three million deaths every year. Though, to a large extent, it has been eradicated from large parts of North America and Europe, it is rampant in most areas of the tropics. Travellers to the tropics have to specially safeguard themselves against the risk of malaria.





Cause and Pathogenesis

Malaria is caused due to infection by the protozoan Plasmodium species. It is transmitted by the bite of the infected Anopheles mosquito. Four major species of Plasmodia are implicated in the causation of malaria in humans and these are Plasmodium Vivax, Plasmodium Ovale, Plasmodium Malariae and Plasmodium Falciparum. Among these species, it is Plasmodium Falciparum that is the most dangerous and that is responsible for most of the deaths resulting from malaria. Infection begins when the infected female Anopheles mosquito bites the human. The microscopic forms of the parasite are carried through the patient's blood stream until they reach the liver. There they invade the liver cells and begin to reproduce. The swollen liver cells eventually burst discharging the merozoite forms of the parasite into circulation and this is when the symptoms of the infection start to become apparent.

Once inside the bloodstream the merozoites invade the red blood cells and start to grow. They consume and degrade the intracellular proteins inside the red cell, especially the haemoglobin, eventually causing the infected red cells to rupture.

Symptoms and Signs


The early symptoms of malaria are non-specific. The patient usually feels ill and has headache, fatigue, muscle pains and vague abdominal discomfort. These symptoms are followed by fever. The fever in classical malaria is a sequence of paroxysms of fever spikes, chills and rigors with sweating occurring at regular intervals. Physical examination reveals a few findings like a palpable spleen and mild anaemia with some patients having a mildly enlarged, palpable liver. Altered consciousness occurs in Falciparum malaria and may be an ominous sign as are convulsions. The involvement of the nervous system is seen in cerebral malaria, which is caused by Plasmodium Falciparum and is the most lethal form of malaria. Kidney failure is also seen sometimes in Falciparum Malaria.





Investigations and Diagnosis

The diagnosis of malaria depends upon the demonstration of the asexual forms of the parasite in the peripheral blood smears of the individual. There are now a number of newer methods of demonstrating the parasite in the blood. The Quantitative Buffy Coat (QBC) technique is now in extensive use. However, in endemic areas it is not always possible to demonstrate the parasite in the blood smears and several patients get treated for malaria on the basis of their clinical symptoms and signs. Supportive evidence for malaria may come in the form of mild anaemia, raised erythrocyte sedimentation rate and increased levels of C-Reactive protein. In severe cases, many of the biochemical parameters in blood are altered.

Treatment and Prognosis


Once the diagnosis of malaria has been made on the basis of a positive blood smear or strong clinical suspicion, then treatment should be started without delay. Chloroquine remains the mainstay in the treatment of malaria. The other drugs that are often used include Mefloquine, Tetracyclines, Primaquine, Pyrimethamine, Proguanil and Quinine. Newer drugs like Halofantrine, Artesunate and Qinghaosu are being used for cases of Chloroquine-resistant malaria. Except for the Falciparum malaria, patients who receive adequate treatment for the other forms, most often have an uneventful recovery. However, resistance to the conventional drugs is increasing and is a major cause for worry.

Cerebral malaria is a medical emergency and even with the best of treatment there is a substantial mortality rate.

Prevention


Prevention is the area on which the maximum focus should be. Steps to reduce the frequency of mosquito bites in endemic areas are important. Use of suitable clothing, insect repellents, bed nets etc. are recommended. Widespread use of the bed nets and repellents has been shown to reduce the incidence of malaria. Efforts are taken to reduce the population of mosquitoes in endemic areas. However, Chemoprophylaxis is often recommended for people who travel to malaria-endemic areas. Chloroquine is most often the drug of choice for Chemoprophylaxis except in areas of known chloroquine-resistance where drugs like Mefloquine or Doxycycline are used.