In this essay we will discuss about Malaria:- 1. Historical Background of Malaria 2. Human Species of Malarial Parasite 3. Symptoms and Pathogenicity 4. Diagnosis 5. Control 6. Anti-Malarial Campaign.
Essay # Historical Background of Malaria:
It is very long ago that malaria was differently named as ague fever, marsh fever, intermittent fever, jungle fever, etc. The name malaria (Gr., mala = bad; aria = air) to this fever was given by Macculoch (1827) on the presumption that it was caused by the bad air of marshy localities.
Laveran (1880), first reported the malaria parasites in the blood of a malarial patient. But the way of entry of the parasites in human blood remained a mystery for a long time.
However, Richard Pfeiffer (1892) suggested the role of some blood-sucking insect in the transmission of malaria. Patrick Manson (1894) suggested the role of mosquitoes in the transmission of malaria. Working on this suggestion, Sir Ronald Ross (1897), an Indian army doctor, succeeded in establishing that malaria parasites are sucked up by female Anopheles mosquito and later on injected in the human blood.
Thus, mosquito-malaria relationship was established. This historic discovery (for which Sir Ronald Ross earned Nobel Prize in medicine, 1902) was made on August 29, 1897, referred to as the ‘Mosquito Day’. Then, Grassi (1898) and his associates worked out the complete life (Nobel Prize, 1902). cycle of the human malaria parasite in the Anopheles mosquito.
Shortt (1948) and Garnham (1954) have discovered that this parasite first enters the liver cells to undergo pre-erythrocytic schizogony before invading the red blood corpuscles. Rudzinska et al., (1965) have studied its ultra structure.
Essay # Human Species of Malarial Parasite:
As a disease, malaria is known for centuries. Once night air was thought to be poisonous causing fevers such as malaria. In fact the name malaria means bad air. Malaria is caused by four species of Plasmodium, but their morphology and life cycles are almost alike, yet they show some distinguishing characters.
1. Plasmodium Vivax:
Plasmodium vivax has a wide distribution in tropical and temperate zones; incubation period is 10 days; ring-shaped trophozoite is 1/2 to 1/3 the size of the erythrocyte; schizont fills the enlarged erythrocyte and has yellowish-brown haemozoin; enlarged erythrocyte has Schuffner’s dots; in blood the schizont forms 12 to 24 merozoites; gametocytes fill the enlarged erythrocytes.
2. Plasmodium Malariae:
Plasmodium malariae is found in tropical and temperate zones; incubation period is 27 to 37 days; ring-shaped trophozoite is 1/3 to 1/2 the size of the erythrocyte; schizont fills the erythrocyte which is not enlarged; haemozoin is dark brown; erythrocyte has no Schuffner’s dots; in blood the schizont forms 6 to 12 merozoites; gametocytes are round, they fill the erythrocyte which is not enlarged.
It causes quartan malaria fever every 72 hours.
3. Plasmodium Falciparum:
Plasmodium falciparum is very common in tropics; incubation period is 10 days; ring- shaped trophozoite is 1/6 to 1/5 of the erythrocyte, often there are two trophozoites in one corpuscle; schizont is 2/3 to 3/4 of erythrocyte which is not enlarged; haemozoin is black; erythrocytes not enlarged, they may even shrink and become greenish, they have no Schuffner’s dots; in blood the schizont forms 8 to 36 merozoites which are not seen in peripheral circulation; gametocytes are crescentic occupying one side of erythrocyte.
It causes pernicious malaria or malignant tertian malaria fever almost continuously or from 24 to 48 hours. A very serious result of falciparum infection is backwater fever, a condition when wholesale destruction of patient’s erythrocyte occurs and the liberated haemoglobin is excreted in urine.
4. Plasmodium Ovale:
Plasmodium ovale is sporadic in tropical and subtropical zones; incubation period is 14 days; ring-shaped trophozoite is 1/3 to 1/2 of the erythrocyte; schizont fills 3/4 of the erythrocyte which becomes enlarged and irregular in shape; haemozoin is dark brown; the enlarged erythrocytes have Schuffner’s dots; in blood the schizont forms 6 to 12 merozoites; gametocytes are round almost filling, the enlarged and irregular-shaped erythrocytes.
It causes ovale or mild tertian malaria fever every 48 hours.
Essay # Symptoms and Pathogenicity of Malaria:
The symptoms of malaria, in case of P. vivax infection, appear on an average after about 14 days of initial infection. In fact, it starts when the merozoites along with toxins are liberated into the blood, they are then deposited in the spleen, liver and under the skin, so that the host gets a sallow colour.
The accumulated toxins cause malaria fever in which the patient suffers from chills, shivering and high temperature with convulsions followed by profuse sweating. The fever lasts from six to ten hours, then it comes on again after every 48 hours coinciding with the liberation of new generation of merozoites. The malaria caused by P. vivax is known as benign tertian malaria.
After repeated and simultaneous schizogony, large numbers of erythrocytes are destroyed at intervals of 48 hours setting free increasing amounts of toxins into the blood, this causes the characteristic paroxysm of malaria on every third day. The paroxysm is divisible into three stages, chill or rigour stage, febrile or high temperature stage with fever over 104° F., and defervescent or sweating stage (Fig. 19.6).
Obviously, since erythrocytes are damaged in Plasmodium infection, hence, anaemia becomes inevitable. Anaemia develops because of the destruction of erythrocytes in large number; the infected erythocytes become fragile, hence, easily ruptured and damaged.
The enlarged, spleen is said to release lysolecithin, a lytic substance, which damages erythrocytes and the parasite is believed to produce an antibody, the haemolysin, which haemolyse the normal erythrocytes.
Essay # Diagnosis of Malaria:
Chills, shivering, muscular pain, high temperature and profuse sweating are the most apparent symptoms to diagnose the infection of P. vivax. In acute conditions the development of anaemia with enlargement of spleen is sufficient to diagnose its infection. However, the diagnosis must be confirmed by blood test.
Essay # Control of Malaria:
Malaria is one of the most important human diseases, since it not only kills millions of people annually, but it renders the most fertile regions of the earth unsafe for human habitation.
The oldest remedy known against malaria is quinine which is very effective in killing schizont stages, but it is ineffective against gametocytes and exoerythrocytic stages, Mepacrine is effective against merozoites, but paludrine is superior to both as it kills almost all stages, except the one in the liver.
However, the control measures of malaria can be discussed in the following three headings:
1. Destruction of the secondary host (mosquito):
Control of mosquitoes for prevention of malaria is very important; this may be done by:
(i) killing the mosquitoes in human dwellings by spraying them with D.D.T., which remains toxic to mosquito for several months
(ii) by filling up ditches and ponds where mosquitoes breed, and by draining swampy places to prevent breeding. In India, five wet days followed by 2 to 3 dry days were found very effective in the control of mosquitoes
(iii) by spraying surface of ponds with kerosene oil or with insecticides which kill larvae and pupae of mosquitoes; it is easier and more effective to kill larvae than the adults; they can also be destroyed by introducing certain fish (minnow, Gambusia, Lebistes) which are the natural enemies of mosquitoes because they feed on larvae and pupae.
2. Prevention of infection:
The preventive measures are essential to adopt to avoid the infection. These usually involve the defence against mosquito bites and use of preventive drugs.
Use of insect repellents, nets, screening of windows of the house, etc., prevent mosquito bite, similarly, use of anti-malarial drugs like Quinine, Paludrine, Daraprim, etc., in definite dose periodically are effective in checking malaria infection.
3. Treatment of the infected person:
Various drugs are used for the treatment of malaria. Physicians usually recommend drugs like Quinine, Atebrin, Camoquin, Chloroquine, Plasmoquine, Resochin, Pentaquine, Pamaquine, Mepacrine, Paludrine, etc., for the treatment of malaria.
Essay # Anti-Malarial Campaign:
Since, malaria is a global problem to some extent but certain countries like India face a widespread infection of this disease. However, with the assistance of World Health Organization (WHO), the Ministry of Health of Government of India started a National Malaria Control Programme (NMCP) in the year 1953.
Under this programme effective measures were taken and malaria was almost controlled because DDT and other insecticides used were very much effective in eradicating the mosquitoes. But in recent years the cases of malaria are frequently witnessed and the frequency is rapidly increasing again.
It appears that the insects have developed resistance and immunity to DDT and other similar insecticides; they have also changed their behaviour.
However, various research laboratories in our country like Vector Control Research Centre at Pondicherry, Postgraduate Medical Institute at Chandigarh, National Institute of Communicable Diseases at Delhi and others are engaged in finding out the measures to check malaria infection and also the way to eradicate the mosquitoes.