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Introduction: Malaria has
been known to mankind since millennia and probably human malaria
evolved with the mankind. Today malaria affects more than 2400 million people, over 40% of
the world's population, in more than 100 countries in the tropics. Every year 300 million
to 500 million people suffer from this disease and about 1.5 million to 3 million people
die of malaria every year (85% of these occur in Africa), accounting for about 4-5% of all
fatalities in the world. Malaria ranks third among the major infectious diseases in
causing deaths. It is re-emerging as the # 1 Infectious Killer and it is the Number 1 Priority Tropical Disease of the World Health
Organization.
Aetiology: Malaria is an infectious disease
caused by the parasite called Plasmodia. There are four
identified species of this parasite causing human malaria, namely, Plasmodium vivax, P.
falciparum, P. ovale and P. malariae. Plasmodium falciparum is more common in sub Saharan
Africa and Melanesia (Papua New Guinea, Solomon Islands); Plasmodium vivax in Central and
South America, India, N. Africa and Middle East; Plasmodium ovale in Western Africa and
Plasmodium malariae is sporadic worldwide.
Transmission:
Malaria is transmitted by the female anopheles mosquito.
The mosquito enters human dwellings in the evening hours and bites late in the night.
Pathogenesis:
The infective form of the parasite are called sporozoites. Once in the body after the
mosquito bite, these sporozoites reach the liver in 30-40 minutes and start developing in
the parenchymal cells of the liver. Each sporozoite multiplies into 20-30000 merozoites,
ruptures the liver cell and is liberated into the blood stream where it infects red blood
cells. This phase of development within the liver is termed Pre-erythrocytic schizogony.
Since only a few hepatocytes are affected, this phase does not produce any symptoms or
signs. The merozoites in the blood infect red blood cells and develop within these cells
through stages. Each merozoite divides into 8-32 fresh merozoites, which rupture the red
cell and infect fresh red cells. This cycle occurs every 48-72 hours and it is called
erythrocytic schizogony. All the clinical manifestations of malaria are due to the
erythrocytic phase that results in the release of pro-inflammatory products of red cell
membrane and of the parasites. The clinical manifestations like chills and fever coincide
with this 48-72 hours cycle and occur every alternate day or once in 72 hours. Some of the
tissue forms in P.vivax and P. ovale go into hibernation (to tide over the adverse
conditions in the sub tropical and temperate regions) and get re-activated once in 2-6
months to cause relapse of symptoms. Some of the blood forms of the Plasmodia transform
into the sexual forms called as gametocytes (male and female) and when taken up by the
female anopheles mosquito, continue the life cycle within its body to become infective
sporozoites.
Clinical
Features: Malaria is a febrile illness characterized by fever and related
symptoms. But in an endemic area, malaria can present with myriad manifestations.
Therefore, malaria is a great imitator and trickster.
Malaria is typically described as an
illness characterized by shaking chills, followed by high grade fever and sweating (Cold
stage, Hot stage and Sweating stage). The febrile episode starts with shaking chills,
usually at midday between 11 a.m. to 12 noon, and this lasts from 15 minutes to 1 hour
(The cold stage), followed by high grade fever, even reaching above 1060 F,
which lasts 2 to 6 hours (The hot stage). This is followed by profuse sweating and the
fever gradually subsides over 2-4 hours. These typical features are seen after the
infection gets established for about a week.
Atypical Features: These
are more likely in the following situations- P. falciparum malaria, extremes of age,
pregnancy, immunocompromised (like HIV disease, tuberculosis, malignancy, diabetes,
major organ disease etc.), immuno suppressed (patients on steroids, immunosuppressants for
organ transplant/connective tissue disease etc.); patients who are immune to malaria after
many attacks, people on chemoprophylaxis, patients with complications of
P. falciparum
malaria etc.
The following atypical
features can be observed:
1. Atypical fever: Patient may present with low grade fever, or continuous
fever or quotidian fever with many spikes a day or as a classical P.U.O., Patients at
extremes of age, with immuno compromise, on immunosuppressants, on prophylaxis or immune
after many attacks and patients in shock may not have fever at all.
2. Head ache and body ache mimicking meningitis or encephalitis or ICSOL.
3. Weakness, prostration, easy fatiguability: This is particularly common in
patients who present with algid malaria.
4. Vomiting and diarrhoea: These are very common and could be due to
the disease or its treatment. P. falciparum can present as Choleraic form.
5. Cough: A dry hacking cough can be the presenting feature of early
P. falciparum malaria.
6. Breathlessness: Severe anemia associated with P. falciparum malaria or
chronic P. vivax malaria can present as exertional dyspnea. It can also be due to
non-cardiogenic pulmonary oedema in severe P. falciparum malaria.
7. Chest pain: Rapid enlargement of spleen and peri-splenitis can cause pain
over left lower chest or abdomen and it may even radiate to left shoulder tip. Coupled
with hypotension, sweating, breathlessness etc., it can easily mimic acute myocardial
infarction. Chest pain and fever can also be mistaken for pleurisy, pneumonia, etc
8. Acute abdomen: Patients can present with acute pain abdomen, mimicking
perforation of D.U./ ureteric colic, etc.
9. Altered behaviour, altered sensorium, convulsions, coma: These can be due
to the severe infection or the drugs or both. Hypoglycemia, either due to disease or drugs
like quinine, is an important cause for these symptoms. Therefore administration of 25%
dextrose may be advisable in all such cases. Chloroquine can also cause acute psychosis in
some.
10. Ataxia: Patients with P. falciparum malaria can present with cerebellar
symptoms and signs.
11. Combinations: Patients can present with various combinations of the
above mentioned symptoms, further confusing the picture.
Diagnosis: Diagnosis of malaria is confirmed by
examination of the blood for malarial parasite. It can be done by the traditional
peripheral smear examination or by the new QBC fluorescent technique. The fluorescent
technique is faster and more sensitive, but identification of the species and assessment
of severity is difficult or even impossible. When in doubt, it is better to ask for a
peripheral smear. There are other non-microscopic tests like Parasight F test, Optimal
Assay, ICT test etc.
Complications of P. falciparum Malaria:
P. falciparum
can cause various organ dysfunction resulting in dramatic and life threatening
complications. One should be always alert to these possibilities. Hyperpyrexia, pallor,
jaundice, prostration, breathlessness, CNS manifestations, oliguria, hypotension etc., are
indicators of complications. Also, patients at extremes of age, pregnant, non-immune etc.,
are prone for these complications. All cases of complicated P. falciparum malaria should
be admitted and treated with parenteral anti malarials, with due consideration for the
local sensitivity pattern. Constant monitoring for various organ functions, and in
particular hemoglobin, blood glucose, creatinine and SGPT is essential. 12 hourly
monitoring of parasite count is necessary to assess the response to therapy and to detect
cases of drug resistance (a decrease of < 75% over 48 hrs. indicates resistance)
Treatment
of malaria: It is a disease that can be treated in just 48 hours, yet it can
cause fatal complications if the diagnosis and treatment are delayed.
Treatment of malaria involves
administration of a blood schizonticidal drug for alleviation of symptoms and tissue
schizonticidal and gametocytocidal drugs for preventing relaplse and transmission
respectively.
Chloroquine is the most effective, safe
and cheap blood schizonticidal drug. It is effective in all cases of vivax, ovale and
malariae infections and in cases of sensitive P. falciparum infection. It is administered
at a dose of 25 mg/kg (max. 2500 mg), generally in 4 divided doses - first dose of
10 mg/kg and then 3 doses of 5 mg/kg over 36-48 hours. Chloroquine is also gametocytocidal
against P. vivax malaria and therefore presumptive treatment with chloroquine helps in
preventing the spread of vivax infection.
Primaquine is used for its tissue
schizonticidal and gametocytocidal activities in all patients of malaria. In
P. vivax and
P. ovale infections, it prevents relapse by destroying the tissue forms when given at a
dose of 0.25 mg/kg (max. 15 mg) as a single dose daily for 14 days. In
P. falciparum
infection, a single dose of 0.75 mg/kg (max. 45 mg) is given at the earliest to destroy
the gametocytes.
In cases of P. falciparum infection with
proven resistance to chloroquine, second line drugs like quinine,
pyrimethamine+sulfadoxine or tetracyclines can be used. In cases of multi-drug resistant
P. falciparum infection, either mefloquine, halofantrine or artemisinin derivatives can be
used. In cases of complicated P. falciparum malaria, parenteral antimalarials should only
be used (injections of chloroquine, quinine or artemisinin derivatives depending on the
sensitivity pattern in the locality).
Prevention
and control: Malaria vaccine has not yet become a reality. Prevention of
individual infection requires dedicated and continuous efforts. Control of malaria is a
difficult task, because it involves three living beings that are highly adaptable and two
which (man and mosquito) are moving.
Every individual living in or visiting a
malarious area should adopt personal protection measures against mosquito bites. These
include closing of windows and doors, screening of windows, using mosquito repellant
creams, lotions, coils or mats and mandatory use of mosquito nets, preferably insecticide
treated bednets. Travelers to malarious areas should also take chemoprophylaxis of
antimalarial drugs.
Control of malaria involves various
measures directed at reducing the load of infection in the community and reducing the
transmission by controlling the mosquitoes.
-
Early Diagnosis and Prompt Treatment
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Personal Protection
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Repellants
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Bed nets
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Chemoprophylaxis
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Mosquito Control Measures
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Source Reduction
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Larvicides - chemical, biological
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Adult insecticides
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