Malarial is caused by a parasite called Plasmodium, which is transmitted via the bites of infected mosquitoes. In the human body, the parasites multiply in the liver, and then infect red blood cells, Key interventions to control malarial include: Prompt and effective treatment with artemisinin – based combination therapies: use of insecticidal nets by people at risk: and indoor residual spraying with insecticide to control the vector mosquitoes.
Malarial parasites are from the genus plasmodium (phylum Apicomplexa). In humans, martial is caused by P. falciparaum, P. malaria, P. ovale, P. vivax and P. knowlesi. Among those infected, P. falciparum is the most common species indentified (75%) followed by P. vivax (-20%). P. falciparum accounts for the majority of deaths. P. vivax proportionally is more common outside of Africa. There have been documented human infections with several species of Plasmodium from higher, anes: however, with the exception of P. knowlest a zoonotic species that causes malaria in macaques – these area mostly of limited public health importance.
The disease is widespread in tropical and subtropical regions in a board band around the equator, including much of Sub-Saharan Africa and Asia.
Signs and symptoms
The signs and symptoms of malarial typically begin 8 – 25 days following infection. However, symptoms may occur later in those who have taken ant-malarial medications as prevention. The presentation may include fever, shivering, arthralgia (join pain), vomiting, hemolytic anemia, jaundice, hemoglobinuria, retinal damage, and convulsions. Approximately 30% of people however will no longer have a fever upon presenting to a health care facility.
The classic symptom of malaria is cyclical occurrence of sudden coldness followed by rigor and then fever and sweating lasting about two hours or more, occurring every two days in P. vivax and P. ovale infections, and every three days for P. malaria. P. falciparum infection can cause recurrent fever every 36-48 hours or a less pronounced and almost continuous fever. For reasons that are poorly understood. But that may be related to high intracranial pressure, children with malaria frequently exhibit abnormal posturing, a sign indicating severe brain damage. Cerebral malaria (encephalopathy specifically related to P. falciparum infection) is associated with retinal whitening, which may be a useful clinical sign in distinguishing malaria from other causes of fever.
Severe malaria is usually caused by P. falciparum, and typically arises 6 – 14 days after infection. Non-falciparum species have however been found to be cause of 14% of cause of severe malaria in some groups. Consequences of severe malaria include coma and death if untreated – young children and pregnant women are especially vulnerable. Splenomegaly (enlarge spleen), severe headache, cerebral ischemia, hepatomegaly (enlarge liver) hypoglycemia, and hemoglobinuria with renal failure may occur. Renal failure is a feature of black water fever, where hemoglobin from lysed red blood cells leaks into the urine.
Malaria is divided into severe and uncomplicated by the World Health Organisation(WHO) Severe malaria is diagnosed when any of the following criteria are present otherwise it is considered uncomplicated.
- Decreased consciousness
- Significant Weakness such that the person is unable to walk
- Inability to feed
- Two or more convulsions
- Low blood pressure (Less than 70 mmHg in adults or 50 mmHg in children)
- Breathing problems
- Circulatory shock, kidney failure or hemoglobin in the urine
- Bleeding problem
- Pulmonary edema
- Low blood glucose (less than 2.2mmol/l/40 mg/dl)
- Acidosis or lactate levels of greater than 5mmol/l
- A parasite level in the blood of greater than 2%
Methods used to prevent malaria include medications, mosquito eradication and the prevention of bites. The presence of malaria in an area requires a combination of high human population density, high mosquito population density and high rates of transmission from humans to mosquitoes and from mosquitoes to humans. If any of these is lowered sufficiently, the parasite will eventually disappear from that area, as happened in North America, Europe and much of the Middle East. However, unless the parasite is eliminated from the whole world, it could become re-established if conditions revert to a combination that favours the parasite’s reproduction. Many countries area seeing an increasing number of imported malaria cases owing to extensive travel and migration.