Introduction to Malaria
Malaria is a parasitic disease caused by
Plasmodium species, transmitted to humans through the bites of infected
Anopheles mosquitoes. It remains a significant public health challenge, particularly in tropical and subtropical regions. Histologically, malaria has distinct features that can be observed in various tissues, providing crucial insights into its pathology and aiding in diagnosis.
Histological Features of Malaria
Histological examination of tissues affected by malaria reveals several characteristic changes. These changes are primarily due to the sequestration of infected red blood cells (RBCs), immune responses, and the toxic effects of the parasite on host tissues.Red Blood Cell Changes
In malaria,
RBCs become infected with Plasmodium parasites. The infected RBCs may exhibit
Schüffner dots (fine, granular stippling in the cytoplasm) in cases of Plasmodium vivax or ovale infections. Infected RBCs often appear enlarged and may demonstrate a distorted shape. These changes are best observed in blood smears stained with Giemsa stain.
Sequestration and Tissue Hypoxia
One of the hallmarks of severe malaria, especially caused by
Plasmodium falciparum, is the sequestration of infected RBCs in microvasculature. This sequestration leads to tissue hypoxia and contributes to the pathology of
cerebral malaria, acute renal failure, and other severe complications. Histologically, this can be seen as capillaries and venules packed with parasitized RBCs.
Spleen Pathology
The spleen plays a crucial role in filtering infected RBCs and mounting an immune response. In malaria, the spleen is often enlarged (splenomegaly) and may exhibit
hyperplasia of lymphoid follicles and increased numbers of macrophages containing engulfed parasitized RBCs and hemozoin pigment. Chronic malaria can lead to
fibrosis and architectural distortion of the spleen.
Liver Pathology
The liver is another organ significantly affected by malaria. Histological examination of the liver in malaria reveals
Kupffer cell hyperplasia, sinusoidal congestion, and the presence of hemozoin pigment. In severe cases, there may be evidence of hepatocyte damage and focal necrosis.
Bone Marrow Findings
Malaria can also affect the bone marrow, leading to
dyserythropoiesis (abnormal red blood cell production) and hemophagocytosis (macrophages engulfing RBCs, white blood cells, and platelets). The bone marrow may show an increased number of macrophages containing malarial pigment and parasitized RBCs.
Kidney Pathology
Renal involvement in malaria can result in acute kidney injury. Histologically, this may be characterized by acute tubular necrosis, interstitial nephritis, and the presence of malarial pigments in renal tubules. Chronic infection can lead to
glomerulonephritis and eventual renal failure.
Placental Malaria
In pregnant women, malaria can lead to placental sequestration of infected RBCs, which is associated with adverse outcomes such as low birth weight and preterm delivery. Histologically, the placenta may show intervillous space congestion with parasitized RBCs, fibrin deposition, and the presence of malarial pigment.Diagnosis and Histological Techniques
Histological diagnosis of malaria primarily relies on the examination of blood smears using Giemsa stain. However, tissue biopsies from affected organs (e.g., liver, spleen, bone marrow) can also provide valuable diagnostic information. Advanced techniques such as immunohistochemistry and molecular methods (e.g., PCR) can enhance the detection and characterization of Plasmodium species in tissue samples.Conclusion
Malaria's impact on human tissues is profound and varied, with distinct histological features that are crucial for understanding its pathology. Histological examination provides valuable insights into the mechanisms of disease and aids in the accurate diagnosis and management of this life-threatening infection.
