Zambia: Malaria and Acquired Immunity
By JONES MUNANG’ANDU,
MALARIA is protozoa infection of the genus plasmodium.
There are four (4) main species of parasites that infect humans; Plasmodium falciparum, plaslesmodium vivax, plasmodium malariae and plasmodium ovale.
Of these the most common in Zambia and indeed most lethal is P. Falciparum.
This species account for 95 per cent of all the malaria cases in Zambia,with P.malariae comprising 3 per cent and P. ovale 2 per cent.
Plasmodium vivax is very rare in Zambia(NMCC,2004).
Female Anopheles mosquitoes spreads malaria.
There are about 250 species of mosquitoes in Zambia and of these about 40 belong to Anopheles species.
Three (3) main vectors have been identified; These are Anopheles Fumestus,Anopheles Gambiae and Anopheles arabiensis.
Malaria is a major public health problem in Zambia. Malaria also contributes to maternal mortality infant and under five child mortality.
Even though the economic impact in Zambia has not yet been quantified, it is likely to be substantial due to the number of productive days lost due to the number of productive days lost due to malaria.
The intensity of malaria in an area determines the effect of all malaria cases.
Malaria transmission has been classified as either stable or unstable. In areas of stable transmission, malaria is frequently transmitted by mosquitoes from one person to another resulting in high levels of acquired immunity and low peripheral parasitaemia.
On the other hand, in areas of unstable transmission malaria is infrequently transmitted by mosquitoes from one person to another.
Therefore, patients in these areas have low level of acquired immunity with heavy peripheral parasitaemia and the areas are prone to epidemics.
Everybody in Zambia is at risk of being infected by malaria.
However, children under the age of five (5) years, pregnant women and immune suppressed persons are more susceptible.
Tourists and people returning from non-malarious areas are prone due to lack of acquired immunity.
In areas of high of high transmission like Zambia, children are at higher risk due to neonatal naivety or lack of exposure to parasite infection.
These children suffer high parasite densities and acute clinical disease.
If untreated, this can progress very rapidly to severe malaria.
Pregnant women are also susceptible to malaria infection because their immunity is suppressed.
Studies have shown that pregnant women through the region have significant levels of placental parasitaemia.It is more common among the primagravida ( first pregnancy) and even worse among the HIV positive pregnant women, because their immune status is suppressed even further. ( Stekefee RW et al (1996).
For the pregnant woman, her depressed immunity makes her more susceptible to malaria and puts her at a higher risk of developing severe malaria, which may lead to death and Aneamia as well as increasing the risk of death from hemorrhage.
The increased likely hood of pregnant woman getting malaria also adds a significant risk to the developing foetus, such as severe malaria which may lead to abortion, still birth or premature delivery.
Furthermore,malaria contribute to low birth weight which is directly linked to infant mortality.
If malaria is avoided in pregnancy,the risk of mother to child transmission of HIV is reduced further during foetal life.
Even though one might have an acquired immunity for malaria, research has shown an interaction between malaria and HIV/AIDS to increase the level of illness in the patient.
Consequently, HIV positive persons are more likely to have malaria parasitaemia and have a reduced response to anti malaria medication.
Prompt diagnosis and early treatment are vital element of the management of the malaria.
The primary objective is to shorten the course of illness, prevent the illness from becoming severe and prevent death or sequelae from severe malaria.
“Available data shows that in areas of intense transmission infected person with high proportions of partial immunity to malaria are often symptomatic.” (WHO, 2005).
Effective management, of malaria can only be treated by qualified personnel.