Abstract
Malaria is a life-threatening disease caused by the bite of the female Anopheles mosquito, which results in infection of the red blood cell. Malaria is a protozoal disease caused by infection with the parasites of genus Plasmodium (species falciparum, vivax, ovale, malariae and knowlesi). P. falciparum is associated with a greater maternal and fetal mortality/morbidity (low birthweight and anaemia) than non-falciparum infections.
In 2016, there were an estimated 216 million cases of malaria in 91 countries, an increase of 5 million cases over 2015. Malaria deaths reached 445 000 in 2016, with most malarial cases and deaths occurring in sub-Saharan Africa.
In 2008, there were six deaths reported in the UK from malaria.
Specific risk groups more vulnerable to malaria are young children, non-immune pregnant women, semi-immune pregnant women, semi-immune HIV-infected pregnant women, individuals with HIV/AIDS, travellers from non-endemic areas and immigrants.
Background and Epidemiology
Malaria is a life-threatening disease caused by the bite of the female Anopheles mosquito, which results in infection of the red blood cell. Malaria is a protozoal disease caused by infection with the parasites of genus Plasmodium (species falciparum, vivax, ovale, malariae and knowlesi). P. falciparum is associated with a greater maternal and fetal mortality/morbidity (low birthweight and anaemia) than non-falciparum infections.1
In 2016, there were an estimated 216 million cases of malaria in 91 countries, an increase of 5 million cases over 2015. Malaria deaths reached 445 000 in 2016, with most malarial cases and deaths occurring in sub-Saharan Africa.
In 2008, there were six deaths reported in the UK from malaria.2
Specific risk groups more vulnerable to malaria are young children, non-immune pregnant women, semi-immune pregnant women, semi-immune HIV-infected pregnant women, individuals with HIV/AIDS, travellers from non-endemic areas and immigrants.
Life Cycle
The female anopheline mosquito, while taking her blood meal, injects ‘sporozoites’ into the bloodstream of the intermediate host (man or woman). These sporozoites reach the liver and develop into ‘schizonts’. This stage is known as tissue schizogony. A few of these schizonts become dormant forms in the liver, known as ‘hypnozoites’ (seen in P. vivax and P. ovale infections). Hypnozoites are responsible for relapse of malaria. The schizonts burst to release ‘merozoites’, merozoites develop into trophozoites or immature sexual forms which are then taken up during the mosquito’s blood meal. The sexual cycle of the parasite takes place in the definitive host (female anopheline mosquito).3
It has been observed that pregnant women are at two times higher risk of being bitten by a mosquito than their non-pregnant counterparts. This is probably due to physiological phenomena during pregnancy: increased exhalation leading to release of volatile substances which attract mosquitoes, and the higher temperature of the abdominal surface temperature, increasing blood flow to the skin.2 [EL 2]
Signs and Symptoms of Malaria
Malaria is an acute febrile illness.
1. Fever and chills
2. Headache may be mild but it is not specific enough to recognise as malaria
3. Myalgia
4. Cough
5. Neurological signs and symptoms (confusion, disorientation, dizziness or coma)
6. Gastrointestinal (nausea, vomiting, diarrhoea)
If malaria is not treated within 24 hours, P. falciparum malaria can progress to severe illness, often leading to death.
Asymptomatic pregnant women can become severely anaemic, with poor fetal outcome due to placental sequestration.
Classification of Malaria
A) Uncomplicated Malaria
Fewer than 2 per cent parasitised red blood cells in a woman with no signs of severity and no complicating features.
B) Severe and Complicated Malaria
The parasitaemia of severe malaria can be less than 2 per cent. Pregnant women with 2 per cent or more parasitised red blood cells are at higher risk of developing severe malaria and should be treated with the extensive malaria protocol.
Malaria is classified as being severe malaria if any of the following are present:
1. Impaired consciousness or coma
2. Repeated generalised convulsions
3. Jaundice
4. Renal failure
5. Acute respiratory distress syndrome, pulmonary oedema
6. Hypotension, circulatory collapse
7. Haemoglobinuria
8. Spontaneous bleeding disseminated intravascular coagulation
9. Severe anaemia (Hb < 8 g %)
10. Thrombocytopenia
11. Hypoglycaemia (<2.2 mmol/L)
12. Acidosis (pH < 7.3)
13. Hyperlactaemia
14. Parasitaemia > 2%
Diagnosis4
Treatment for malaria should not be initiated until there is a laboratory confirmation, except in cases where there is a strong clinical suspicion.
The following tests are available to diagnose malaria from blood samples:
1. Gold standard test: thick and thin peripheral smears
2. Rapid diagnostic tests (RDT)
3. Polymerase chain reaction (PCR)
1 Microscopic Examination of a Peripheral Smear
The diagnosis of malaria relies on microscopic examination (the current gold standard) of thick and thin blood films for parasites.
Thick smears help pick up the presence of malarial parasite whereas a thin smear helps identify the species and quantify parasite density. A series of three blood smears should ideally be examined by a qualified laboratory technician.4 [Grade A recommendation]
2 Rapid Diagnostic Test (RDT)
A rapid diagnostic test is an alternative way of quickly establishing the diagnosis of malaria infection by detecting specific malaria antigens in the blood and is available in the form of dipsticks or cassettes.
RDTs permit a reliable detection of malaria infections, particularly in remote areas with limited access to good-quality microscopy service. The test determines within 15 minutes whether patients are infected with malaria.
Invalid results mean RDT kits are damaged. If the RDT is negative, no treatment for malaria is required; however, if the symptoms persist, a repeat test should be carried out after a couple of days as the test might miss early malaria infection.
3 Nucleic Acid Amplification-Based Diagnostics
A nucleic acid amplification test can detect low-density malaria infections. It is more sensitive and specific than microscopy as it detects the parasite nucleic acid. It can also detect resistance patterns. The test is more expensive and requires a reference laboratory to run the test.
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