Malaria: Infection and Symptoms

Malaria

• Malaria is a disease caused by the Plasmodium parasite, transmitted by infected mosquitoes
• The infectious agent is the sporozoite
• Most commonly spread through mosquito bites, but transmission is also possible through blood transfusion or transplacentally.

Malaria in Humans

• In humans, the parasite goes through three distinct stages: pre-erythrocytic schizogony, erythrocytic schizogony, and gametogony.
• There are five species of Plasmodium that infect humans:
  • P. vivax
  • P. falciparum
  • P. malariae
  • P. ovale
  • P. knowlesi
• Each species has different patterns of fever and severity.

P. knowlesi Infection

• P. knowlesi causes quotidian malaria, with fever recurring daily.
• Quotidian malaria is caused by a shorter red blood cell cycle (24 hours)
• Clinical features resemble P. vivax infection, but P. knowlesi is associated with more severe disease.
• P. knowlesi infections are increasingly reported in Southeast Asia.
• The only reported case in India is from the Andaman Islands.

Clinical Features of Malaria

• Benign Malaria is milder, caused by all four species except P. falciparum.
• Benign Malaria symptoms include:
  • Febrile paroxysm, a cycle of chills, fever, and sweating that occurs intermittently
  • Anemia (normocytic normochromic anemia)
  • Splenomegaly
• **Malignant Tertian Malaria (caused by P. falciparum) ** is characterized by sequestration of infected red blood cells in deep visceral organs.
• Malignant Tertian Malaria clinical features include:
  • Severe anemia
  • Prostration
  • Headache
  • Nausea
  • Algid malaria, characterized by cold clammy skin, hypotension, peripheral circulatory failure and profound shock.
  • Septicemic malaria, characterized by high-grade fever with dissemination of the parasite to various organs which can lead to multiorgan failure.
  • Pulmonary edema and adult respiratory distress syndrome
  • Hypoglycemia
  • Renal failure

Pathogenesis of P. falciparum Malaria

• Cytoadherence: Infected red blood cells adhere to the lining of blood vessels in the brain, kidney, etc.
• Rosetting: Infected red blood cells bind to uninfected red blood cells, helping to avoid detection by the spleen.

Diagnosing Malaria

• Blood smear examination: This is the gold standard for diagnosing malaria and can be used to differentiate between species.
• Rapid Diagnostic Tests (RDTs) : RDTs are fast, easy to use, and can detect specific Plasmodium antigens.
  • RDTs use nitrocellulose membrane strips with multiple test lines and a control line.
  • RDTs can differentiate between infections by P. falciparum and other species.
• PCR assays: PCR assays are used to detect specific P. knowlesi DNA.

Treatment of Malaria

• Chloroquine and primaquine: Used to treat uncomplicated malaria
• Prompt treatment is crucial, especially for P. knowlesi infections.

Malaria in Special Situations

• Transfusion Malaria: Occurs when malaria parasites are transmitted through blood transfusion, needle stick injury, or organ transplantation.
  • The infective form can be merozoites, trophozoites, or schizonts.
  • No pre-erythrocytic stage or relapse.
  • Treatment is the same as for naturally acquired infections.
• Malaria in Pregnancy: Pregnant women are at greater risk of severe malaria.
  • Can cause fetal distress, premature birth, low birth weight, and stillbirth.
  • Pregnant women are prone to severe anemia, hypoglycemia, and acute pulmonary edema.

Disadvantages of Rapid Diagnostic Tests (RDTs)

• Relatively expensive.
• Less specific than blood smear examinations.
• Difficult to differentiate between species.

Advantages of Rapid Diagnostic Tests (RDTs)

• Fast and easy to use.
• Do not require trained microscopists or specialized equipment.l