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Acute Febrile Illnesses Summary 2022
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- University Of South Africa (Unisa)
Acute Febrile Illnesses Summary 2022
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Acute Febrile IllnessesMalaria
Malaria is a protozoan disease that is transmitted to humans through the bite of female
Anopheles mosquitoes. Malaria is caused by the Plasmodium falciparum of the genus
Plasmodium. the four species that are known to cause diseases in people are:
P. falciparum: also called malignant malaria
P. vivax: tertian malaria
P. ovale : tertian malaria
P. malariae : quartan malaria
. Malaria is one of the most common human infectious diseases, with a worldwide distribution,
and causes approximately 2 million deaths annually. Malaria affects 40% of the world's
population living in tropical/subtropical climates
. Malaria prevalence is increasing due to the emergence of DDT -resistant Anopheles
mosquitoes, drug-resistant Plasmodium parasites, and changes in global Ob.
.Malaria is common in both lowland and highland areas, with epidemics frequently observed in
the latter occurring between 1600 and 2150 meters above sea level in the months September
to December
. The disease is widely prevalent in 75% of the country, affecting over 40 million people
. All human malaria parasites are found in Ethiopia, but Plasmodium falciparum and
Plasmodium vivax are the most common at 60% and 40% respectively. However, P. ovale and P.
malaria
. Malaria endemic is defined based on the incidence of the spleen (palpable spleen) in children
from age 2 to 9 years.
Transmission
• Malaria is transmitted by the bite of female Anopheles mosquitoes or by blood vaccination. A
female Anopheles mosquito carries the Plasmodium parasite and releases her into the human
body while feeding on blood.
• Malaria transmission requires high ambient temperatures and collected water, ideal
conditions for mosquito breeding. Transmission is therefore common in the lowlands during
the wet season, especially when non-immune individuals migrate to the lowlands. Rare cases of
congenital infection are known.
, Life cycle and etiology
• The life cycle of the malaria parasite can be divided into two, the asexual cycle and the sexual
cycle.
• The estrous cycle occurs within the Anopheles mosquito (ultimate host)
• The asexual cycle occurs in the human body and has two stages:
– liver stage (pre- and extra-erythrocytic stage) and
– erythrocytic stage
• Human infection begins with the inoculation of Plasmodium sporozoites by female Anopheles
mosquitoes during blood feeding. Sporozoites are transported to the liver via blood enter
hepatocytes and undergo asexual reproduction. At this stage, a single sporozoite generates
thousands (10,000–30,000) of merozoites. The swollen hepatocyte ruptures and releases
merozoites into the bloodstream, which then invade red blood cells, multiplying 6- to 20-fold
every 48 to 72 hours. When a certain concentration of parasites in the blood is reached, the
symptom phase begins. In P. vivax and P. ovale, some of these liver types remain dormant
(called hypnozoites) for months to years. These dormant forms of (hypnozoites) are
responsible for the relapses that characterize these two infections.
• After entering the bloodstream, merozoites invade red blood cells and become trophozoites.
The trophozoite expands, develops pigment, and becomes a -type amoeba, occupying most of
the red blood cells and consuming almost all the hemoglobin by the end of 48 hours of life in
the RBC. It is now called schizont. Multiple divisions then generate multiple merozoites that are
released into the bloodstream when the infected red blood cell ruptures and repeats the same
cycle to invade other new red blood cells. This explains Malaria's anemia, which is primarily due
to the destruction of her RBCs.
• During this process, infected and sometimes uninfected red blood cells are removed from the
circulation by the splenic lavage function, contributing to anemia. This immune function of the
spleen causes the organ to enlarge.
• In Plasmodium falciparum, infected erythrocytes, including the mature form, adhere to small
blood vessels (called cell adhesion), and uninfected erythrocytes form rosettes (called
rosettes), both of which are found in areas such as the brain. Contributes to the separation of
red blood cells in vital organs guides the heart, disrupts microcirculation and metabolism and
contributes to its weight. This makes the mature form difficult to detect, with only ring type and
her gametocytes detected in peripheral blood smears. Sequestration is not characteristic of
other types of malaria, and all stages of the parasite are found in peripheral blood films.
• After a series of asexual cycles, some parasites develop into morphologically distinct long-
lived sexual forms (gametocytes) capable of transmitting malaria. During blood feeding,
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