Celtnet Malaria Infromation Page

As you can see from the map on the left, Malaria is endemic to much of the tropical regions of the world. However, the severity of the disease and its effects vary from continent to continent. The worst forms are to be found in tropical sub-Saharan Africa (this excludes South Africa). This is also the region where malaria is most resistant to standard quinine-based drugs and this is the problem in treating most malaria cases as the only drugs commonly available are Quinine and Novoquine which are becoming less and less effective. Admittedly, most adults with Malaria develop some level of resistance, yet a bad bout of the disease can lead to liver complicatons, jaundice and even death.

What is Malaria?

Malaria is a parasitic infection caused by the protozoan parasites, Plasmodium. Each year, it causes disease in approximately 650 million people and kills between one and three million, most of them young children in Sub-Saharan Africa. Malaria is commonly-associated with poverty, but is also a cause of poverty and a major hindrance to economic development. Indeed, the most virulent for of the disease, caused by the parasite Plasmodium falciparum is also the commonest form of the disease in Sub-Saharan Africa.

Malaria is one of the most common infectious diseases and an enormous public-health problem. The disease is caused by protozoan parasites of the genus Plasmodium (Plasmodium falciparum is shown here). The most serious forms of the disease are caused by Plasmodium falciparum and Plasmodium vivax, but other related species (Plasmodium ovale, Plasmodium malariae, and sometimes Plasmodium knowlesi) can also infect humans. This group of human-pathogenic Plasmodium species is usually referred to as malaria parasites.

Malaria itself is what's known as a vector-borne infectious disease in that the malarial parasite cannot directly infect humans. Rather, malarial parasites are transmitted by female Anopheles mosquitoes. The parasites themselves infect and multiply within the red blood cells and as a result they cause symptoms that include anaemia (light headedness, shortness of breath, tachycardia etc.), as well as other general symptoms such as fever, chills, nausea, flu-like illness, and in severe cases, coma and death. The symptoms of malaria include fever, shivering, arthralgia (joint pain), vomiting, anemia caused by hemolysis, hemoglobinuria, and convulsions. There may be the feeling of tingling in the skin, particularly with malaria caused by P falciparum. The classical symptom of malaria is cyclical occurrence of sudden coldness followed by rigor and then fever and sweating lasting four to six hours, occurring every two days in P vivax and P ovale infections, while every three days for P malariae. P falciparum can have recurrent fever every 36–48 hours or a less pronounced and almost continuous fever. As the parasites mature and the red blood cells in which they have been growing rupture jaundice can occur (yellowing of the skin or whites of the eyes) and this is often accompanied by anaaemia.

Anopheles gambiae is probably the most well-known species in the genus Anopheles, a genus of approximately 400 species of insects, some 35 of which transmit Plasmodium parasites. Anopheles gambiae is the most well known of these as it's the most common vector for the most aggressive and lethal form of malaria, Plasmodium falciparum. It is only the female Anophelid mosquitoes that transmit malaria, as males live for only a week, feeding on nectar and other sources of sugar. Females will also feed on sugar sources for energy but usually require a blood meal for the development of eggs. After obtaining a full blood meal, the female will rest for a few days while the blood is digested and eggs are developed. This process depends on the temperature but usually takes 2–3 days in tropical conditions. Once the eggs are fully developed, the female lays them and resumes host seeking. This cycle repeats itself until the female dies and if the female feeds on a host suffering from malaria the parasite itself develops within the female and uses that mosquito as a vector.

Plasmodium parasites have two forms: male (microgametocytes) and female (macrogametocytes) that are ingested by an Anopheles mosquito during a blood meal. Whilst in the mosquito's stomach, the microgametes penetrate the macrogametes generating zygotes. The The zygotes in turn become motile and elongated (ookinetes) allowing them to invade the midgut wall of the mosquito where they develop into oocysts. These oocysts grow, rupture, and release sporozoites , which make their way to the mosquito's salivary glands. Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle.

During a blood meal, a malaria-infected female Anopheles mosquito inoculates sporozoites into the human host. Sporozoites infect liver cells and mature into schizonts, which rupture and release merozoites. (Of note, in P vivax and P ovale a dormant stage [hypnozoites] can persist in the liver and cause relapses by invading the bloodstream weeks, or even years later.) After this initial replication in the liver (exo-erythrocytic schizogony ), the parasites undergo asexual multiplication in the erythrocytes (erythrocytic schizogony). Merozoites infect red blood cells. The ring stage trophozoites mature into schizonts, which rupture releasing merozoites. Some parasites differentiate into sexual erythrocytic stages (gametocytes). Blood stage parasites are responsible for the clinical manifestations of the disease.

As the malaria sporocytes can lie dormant in the liver once a person is infected with malaria they can have recurring bouts of malaria and if the infection is with Plasmodium falciparum then there is a 1:10 chance that one of these attacks may be fatal. If the infected person is a child then these recurring attacks can lead to brain damage as the parasite and the damaged red blood cells imaair with the development of a growing brain. Malaria is also extremely dangerous for a pregnant woman and can cause spontaneous abortions.

Malaria is a true curse and if you have read this page then I hope you understand a little better why I am so concerned about my wife and son and how their plight has made me understand more about this potentially crippling and often fatal disease.

Treatment of Malaria

Contrary to popular opinion, a patient suffering from malaria, when properly treated, can expect a complete recovery. However, the treatment of malaria depends on the severity of the disease; whether patients who can take oral drugs have to be admitted depends on the assessment and the experience of the clinician. Uncomplicated malaria is treated with oral drugs. For Plasmodium falciparum, the most aggressive form of malaria, the treatment recommended by the WHO is the use of artemisinins in combination with other antimalarials (the so-called artemisinin-combination therapy, ACT) which seeks to limit the development of drug resistance against artemisinin-based therapies.

Severe malaria requires the parenteral administration (ie directly into the veins) of antimalarial drugs. Until recently the most used treatment for severe malaria was quinine but artesunate has been shown to be superior to quinine in both children and adults. Treatment of severe malaria also involves supportive measures.

Malaria Prophylaxis

The most common use of antimalarial drugs is to prevent infection by malaria in the first place. This is termed prophylaxis. Several drugs, the majority of which are also used in the treatment of malaria can also be taked to prevent malarial infection. Chloroquine may be used where the parasite is still sensitive (but this excludes the regions of the world where the risk of infection is greatest). In these regions, one of three medications: mefloquine (Lariam), doxycycline (available generically), and the combination of atovaquone and proguanil hydrochloride (Malarone) is frequently needed. Doxycycline and the atovaquone and proguanil combination are the best tolerated with mefloquine associated with higher rates of neurological and psychiatric symptoms.

It should be noted that the prophylactic effect of these drugs does not begin immediately which means that people temporarily visiting regions where malaria is endemic usually begin taking the drugs one to two weeks before arriving and must continue taking them for 4 weeks after leaving (with the exception of atovaquone proguanil that only needs be started 2 days prior and continued for 7 days afterwards). Generally, these drugs are taken daily or weekly, at a lower dose than would be used for treatment of a person who had actually contracted the disease. Use of prophylactic drugs is seldom practical for full-time residents of malaria-endemic areas, and their use is usually restricted to short-term visitors and travelers to malarial regions (anti-malarials also tend to be expensive).

In endemic regions, by far the most cost effective measure is to prevent the spread of malaria in the first place by draining marshland, killing the anopheles mosquito or preventing the mosquitoes from biting by using insecticides indoors and sleeping under mosquito nets.