Malaria remains a mosquito-borne infectious disease caused by a group of single-celled parasitic micro-organisms known as protozoa belonging to the genus plasmodium. The disease is mainly transmitted by mosquito bites. The symptoms often commence few days after the bite. Malaria is transmitted most commonly by an infected female Anopheles mosquito. The mosquito bite introduces the parasite called plasmodium from the mosquito’s saliva into a person’s bloodstream. The parasites then travel to the liver where they mature and reproduce. The signs and symptoms of malaria typically begin eight to twenty-five days following infection.
However, symptoms may occur later in those who have taken anti-malarial medications in the past as prevention. Initial manifestations of the disease, which are common to all malaria species, are similar to flu-like symptoms and can resemble other conditions such as septicemia, gastroenteritis and viral diseases.The symptoms may include headache, fever, shivering, joint pain, vomiting, haemolytic anaemia, jaundice, haemoglobin in the urine, retinal damage, and convulsions.
The classic symptom of malaria is paroxysm – a cyclical occurrence of sudden coldness followed by shivering and then fever and sweating; occurring every two days in P. Vivax and P. Malariae infection. Severe malaria, which might lead to death, is usually caused by P. falciparum – often referred to as ‘falciparum malaria’. Its symptoms arise nine to thirty days after contracting the infection. Individuals with cerebral malaria frequently exhibit neurological symptoms including abnormal posturing, nystagmus, conjugate gaze palsy i.e. failure of the eyes to turn together in the same direction, opisthotonus, seizure, or coma.
There are several serious complications of malaria. Among these is the development of respiratory distress, which occurs in up to twenty-five percent (25%) of adults and forty percent (40%) of children with severe P. Falciparum malaria. Possible causes include respiratory compensation of metabolic acidosis, non-cardiogenic pulmonary oedema, concomitant pneumonia and severe anaemia. It is worthy to note that, concurrent infection of HIV with malaria increases mortality rate.
Malaria in pregnant women is the major cause of stillbirths, infant mortality, abortion and low birth weight, particularly in P. Falciparum infection. Symptoms of malaria can recur after varying symptom-free periods. Depending upon the cause, recurrence can be classified as either recrudescence or relapse. Recrudescence is when symptoms return after a symptom-free period; it is caused by parasites living in the blood as a result of inadequate or ineffective treatment.
While, relapse is when symptoms reappear after the parasites have been eliminated from blood but persist as dormant hyponozoites in liver cells; relapse commonly occurs between eight to twenty-four weeks and is common among P. Vivax and P. Ovale infections.
Malaria infection develops via two major phases namely, one involving the liver known as exoerythrocytic phase, and one that involves the red blood cells referred to as erythrocytic phase. When an infected mosquito enters a person’s skin to take a blood meal, sporozoites in the mosquito’s saliva enter the bloodstream and migrate to the liver where they infect hepatocytes, multiplying asexually and asymptomatically for a period of eight to thirty days. After a potential dormant period in the liver, these organisms differentiate to yield thousands of merozoites, which following rupture of their host cells, escape into the blood and infect the red blood cells to begin the erythrocytic stage of their life cycle.
The primary sources of mosquitoes include sewage, refuse, dirty stagnant water, and untidy environment. In most cases, mosquitoes thrive in damp and dirty environments or substances such as gutter, pool, faeces, urine, among other solid and liquid waste materials. This is why residents of untidy localities are at a high risk of contracting malaria.
Methods used to prevent malaria include medications, mosquito elimination through fumigation coupled with regular environmental sanitation, as well as prevention of mosquito bites via regular and proper use of the mosquito nets, among others. Prevention of malaria, which is yet to have a vaccine, may be more cost-effective than treatment of the disease in the long run; though the initial costs required are out of reach of many of the world’s poorest people. Owing to the non-specific nature of symptoms, diagnosis of malaria in non-endemic areas requires a high degree of suspicion. Malaria is invariably confirmed by the microscopic examination of blood films or by antigen-based Rapid Diagnostic Tests (RDT). Microscopy is the most commonly used method to detect the malaria parasite in the body. In spite of its widespread usage, diagnosis by microscopy suffers from two main drawbacks: many settings especially rural are not equipped to perform the test, and the accuracy of the results depends on both the skill of the lab technician and the levels of the parasite in the blood.
Malaria is widely treated with anti-malarial medications. The ones to be used solely depend on the type and severity of the disease. While medications against fever are commonly used, their effects on outcomes are not clear. Uncomplicated malaria may be treated with oral medications. The most effective treatment for P. Falciparum infection is the use of artemisinins in combination with other anti-malarial drugs known as Artemisinin-Combination Therapy (ACT), which decreases resistance to any single drug component.
It is obvious that malaria is a killer disease.
The World Health Organization (WHO) estimates that in 2010, there were about two hundred and ninety (219) million cases of malaria outbreak resulting to six hundred and sixty thousand (660,000) deaths. In majority of cases, about sixty-five percent (65%), occur in children under fifteen years. Survey also indicates that about one hundred and twenty-five (125) million pregnant women are at risk of infection each year; in Sub-Saharan Africa such as Nigeria, Angola, Chad, Congo, Benin, Ghana and several others.
Nwaozor writes from Owerri