By Doris Obinna and Sarah Akinlose
Malaria is a life-threatening disease caused by parasites that are transmitted to people through the bites of infected female mosquitoes.
About 3.2 billion people, almost half of the world’s populations are at risk of malaria.
Young children, pregnant women and non-immune travellers from malaria-free areas are particularly vulnerable to the disease when they become infected.
Every April 25, the world commemorates Malaria Day. According to World Health Organisation, the theme for this year is “End Malaria For Good.”
Following the great progress made under the Millennium Development Goals, it is important to build on this success and ‘end malaria for good’ under the Sustainable Development Goals.
Malaria is preventable and curable, and increased efforts are dramatically reducing the malaria burden in many places.
According to Consultant Family Physician/Director of Training, the Eko Hospitals, Dr B.C.Chukwukelu, malaria refers to the disease caused by the protozoa Plasmodium species, carried by the female anopheles mosquito. The parasites are spread to people through the bites of infected female anopheles mosquitoes, called “malaria vectors.” There are four parasite species that cause malaria in humans; P. falciparum, P. malariae, P. ovale and P. vivax of which two of these species; P. falciparum and P. vivax pose the greatest threat.
Chukwukelu said; “Environmental condition help to determine the intensity of malaria transmission in a region. For example, optimal temperature for parasite development in mosquito is 20-30°C. Sporogony ceases below 16°C. Temperature also affects mosquito development. It takes seven days to develop from egg to adult at 31°C. It takes 20 days to develop from egg to adult at 20°C.
“Malaria transmission is possible if the weather conditions are right to support the growth and infection of anopheline mosquitoes and if a reservoir of malaria parasites is available.
Malaria parasite reservoir can become available in non- malarious regions when travelers or immigrants arrive from malaria endemic countries.”
He said malaria is transmitted through bites from infected female anopheles mosquito, transfusion malaria and congenital malaria.
“Health burden of malaria in pregnant women are major causes of morbidity in pregnancy, and malaria in pregnancy has adverse effects, which differ with the level of malaria transmission and level of immunity in the pregnant woman. Effects are worse and life threatening in the non-immune or partially immune,” he stated.
Experts say that malaria is an acute febrile illness. In a non-immune individual, symptoms appear seven days or more (usually 10–15 days) after the infective mosquito bite. The first symptoms; fever, headache, chills and vomiting may be mild and difficult to recognize as malaria. If not treated within 24 hours, P. falciparum malaria can progress to severe illness, often leading to death.
Children with severe malaria frequently develop one or more of the following symptoms: severe anaemia, respiratory distress in relation to metabolic acidosis, or cerebral malaria. In adults, multi-organ involvement is also frequent. In malaria endemic areas, people may develop partial immunity, allowing asymptomatic infections to occur.
WHO states that in 2015, approximately 3.2 billion people nearly half of the world’s population were at risk of malaria. Most malaria cases and deaths occur in sub-Saharan Africa. However, Asia, Latin America, and, to a lesser extent, the Middle East, are also at risk. In 2015, 97 countries and territories had ongoing malaria transmission.
“Some population groups are at considerably higher risk of contracting malaria, and developing severe disease, than others. These include infants, children under 5 years of age, pregnant women and patients with HIV/AIDS, as well as non-immune migrants, mobile populations and travellers. National malaria control programmes need to take special measures to protect these population groups from malaria infection, taking into consideration their specific circumstances.”
The Physician states that there are 300 million cases of malaria in the world annually,
90 percent of these are in sub Saharan Africa while 50 percent of adults have at least one episode per year and children 4 to 5 episodes.
He said: “It is significant cause of mortality and morbidity particularly in the under-5 population and pregnant women, one million deaths/year 90 percent of which occur in children less than 5 years
“Malaria poses a public health problem, which is increasing by the day and used to be found all over the world, with the exception of a few temperate areas. It occurs in areas with conducive atmosphere for the growth of the anopheles mosquito; adequate rainfall, poor sanitation.
Eradicated in the developed world with improvement in their living conditions and socioeconomic standards.
“Three patterns of transmission by mosquitoes are stable malaria i.e. intense perennial malaria transmission, some seasonal variation increases in the wet season, most marked in (northern Nigeria). High level of immunity in adults i.e. seasonal malaria, seasonal transmission with variations and low level of immunity in adults and lastly epidemic malaria – affects all age groups,” he stated.
Experts proffer vector control is the main way to prevent and reduce malaria transmission. If coverage of vector control interventions within a specific area is high enough, then a measure of protection will be conferred across the community.
Also, WHO recommends protection for all people at risk of malaria with effective malaria vector control. Two forms of vector control; insecticide-treated mosquito nets and indoor residual spraying are effective in a wide range of circumstances.
“Early diagnosis and treatment of malaria reduces disease and prevents deaths. It also contributes to reducing malaria transmission. The best available treatment, particularly for P. falciparum malaria, is artemisinin-based combination therapy (ACT).
“While, WHO recommends that all cases of suspected malaria be confirmed using parasite-based diagnostic testing (either microscopy or rapid diagnostic test) before administering treatment. Results of parasitological confirmation can be available in 30 minutes or less. Treatment, solely on the basis of symptoms should only be considered when a parasitological diagnosis is not possible”
However, research shows that resistance to antimalarial medicines is a recurring problem. Resistance of P. falciparum to previous generations of medicines, such as chloroquine and sulfadoxine-pyrimethamine (SP), became widespread in the 1970s and 1980s, undermining malaria control efforts and reversing gains in child survival.
WHO recommends the routine monitoring of antimalarial drug resistance, and supports countries to strengthen their efforts in this important area of work.
“An ACT contains both the drug artemisinin and a partner drug. In recent years, parasite resistance to artemisinins has been detected in 5 countries of the Greater Mekong subregion: Cambodia, Lao People’s Democratic Republic, Myanmar, Thailand and Viet Nam. Studies have confirmed that artemisinin resistance has emerged independently in many areas of this subregion. Most patients are cured when treated with an ACT if there is no resistance to the partner drug.”
Malaria likes warm temperatures. Human beings serve as intermediate hosts to the pathogen, a parasite of the genus Plasmodium. The final host is the mosquito. After the infected mosquito bites, the pathogen moves to the liver of its human host. In this first stage, it matures and multiplies there before spreading throughout the bloodstream and ultimately attaching to the receptor molecules of red blood cells. After further growth, it triggers the periodic fever typical of malaria from within the blood of the human host. The cycle of this fever is 48 to 72 hours in duration, depending on which type of pathogen is involved. Some of the pathogens develop further into their primary sexual form, the gametocytes. If a mosquito then bites the infected person again, it takes up these gametocytes, which mature into new pathogens inside the mosquito and are soon ready to spread new infection through its saliva. A minimum temperature of 15 degrees Celsius is required for the cycle inside the mosquito, which is why malaria primarily occurs in tropical areas of South America and Asia as well as Africa.