Makindo Medical Notes

Related Subjects: |Fever in a traveller |Malaria Falciparum |Malaria Non Falciparum |Viral Haemorrhagic Fevers (VHF) |Lassa fever |Dengue |Marburg virus disease |AIDS HIV |Yellow fever |Ebola Virus |Leptospirosis | Crimean-Congo haemorrhagic fever |African Trypanosomiasis (Sleeping sickness) |American Trypanosomiasis (Chagas Disease) |Incubation Periods |Notifiable Diseases UK

About

• Malaria is a life-threatening disease caused by Plasmodium parasites transmitted through the bites of infected female Anopheles mosquitoes.
• Even when it doesn't kill, malaria debilitates, leading to decreased productivity and quality of life.
• It predominantly affects working-aged adults, resulting in significant socioeconomic impact.
• Closely associated with poverty, high infant mortality, general mortality, and morbidity.
• See BNF for Current Treatment Guidelines

Etymology

• The word "malaria" comes from the Italian words "mala aria," meaning "bad air," reflecting the historical belief that the disease was caused by foul air in marshy areas.

Types of Plasmodium Species

• P. falciparum: The most lethal form, responsible for the majority of severe cases and deaths, especially in sub-Saharan Africa.
• P. vivax: Common outside Africa; it can survive at lower temperatures and has dormant liver stages (hypnozoites) leading to relapses.
• P. ovale: Less common; similar to P. vivax with the ability to form hypnozoites causing relapses.
• P. malariae: Generally causes milder disease but can persist in the blood for long periods, sometimes leading to chronic infection.
• P. knowlesi: A zoonotic species found in Southeast Asia; can cause severe disease and was previously misdiagnosed as P. malariae due to morphological similarities.

Risk Factors

• Sickle cell trait provides relative protection against P. falciparum malaria.
• Individuals negative for the Duffy blood group antigen are resistant to P. vivax infection; this is common in many African populations.
• Repeated malaria infections can lead to partial immunity, reducing the severity of future infections.
• Infants and young children are at high risk of severe infection due to underdeveloped immunity.
• Immunity to one Plasmodium species does not confer protection against others.
• Variant strains within a species can lead to multiple episodes, as immunity to one strain may not protect against another.

Incubation Periods

• P. falciparum: Typically 10–14 days.
• P. vivax and P. ovale: 10–14 days, but hypnozoites can cause relapses months or years later.
• P. malariae: 18 days to 6 weeks; can persist asymptomatically for years.
• P. knowlesi: Approximately 9–12 days.

Clinical Presentation

• Acute febrile illness characterized by cycles of chills, high fever, and sweating (paroxysms).
• Symptoms include headache, muscle aches, nausea, vomiting, and general malaise.
• P. falciparum can lead to severe complications such as cerebral malaria, anemia, hypoglycemia, and organ failure.
• Chronic infection leads to anemia, splenomegaly, and increased susceptibility to other infections.
• Immunity can wane in individuals who leave endemic areas and then return, increasing susceptibility.
• Neonates are relatively resistant during the first 6 months due to maternal antibodies and fetal hemoglobin.

Investigations

• Microscopic Examination:
  • Thick blood films: Used for detecting the presence of parasites; more sensitive.
  • Thin blood films: Used for species identification and estimating parasitemia levels; stained with Giemsa.
  • Multiple samples over 48 hours may be necessary to exclude malaria.
• Rapid Diagnostic Tests (RDTs): Detect Plasmodium antigens; useful in settings without microscopy.
• Molecular Methods: PCR assays for species identification and detecting low-level parasitemia.
• Additional Tests:
  • Complete blood count (CBC): May show anemia and thrombocytopenia.
  • Liver and renal function tests: To assess organ involvement.
  • Pregnancy testing: Pregnant women are at higher risk for severe disease.

Management

Management depends on the Plasmodium species, severity of infection, and local drug resistance patterns.

Non-Falciparum Malaria

• Usually caused by P. vivax, P. ovale, P. malariae, and P. knowlesi.
• Chloroquine is the drug of choice where there is no resistance.
• In areas with chloroquine resistance, consider artemisinin-based combination therapies (ACTs) such as artemether-lumefantrine (Riamet) or atovaquone-proguanil (Malarone).
• Primaquine is used for radical cure of P. vivax and P. ovale to eliminate hypnozoites in the liver and prevent relapse.
• P. malariae and P. knowlesi are typically treated with chloroquine alone.
• For severe cases or when oral therapy is not possible, intravenous medications such as IV artesunate or IV quinine may be required.
• Test for G6PD deficiency before prescribing primaquine due to the risk of hemolysis.

Falciparum Malaria Management

• P. falciparum requires prompt treatment due to its potential severity.
• First-line treatments include ACTs such as artemether-lumefantrine (Riamet) or atovaquone-proguanil (Malarone).
• In severe cases, intravenous artesunate is preferred over quinine due to better efficacy and safety.
• Supportive care may include management of anemia, hypoglycemia, seizures, and renal failure.
• Pregnant women require special consideration; consult current guidelines for appropriate therapy.

Prevention

• Vector Control: Use of insecticide-treated bed nets, indoor residual spraying, and elimination of mosquito breeding sites.
• Chemoprophylaxis: Travelers to endemic areas should take prophylactic antimalarial medications as recommended.
• Vaccination: The RTS,S/AS01 vaccine is approved for use in children in high-transmission areas.
• Personal Protective Measures: Wearing long sleeves, using insect repellents containing DEET.

Key Points

• Early diagnosis and prompt treatment are critical to prevent severe complications and reduce transmission.
• Resistance to antimalarial drugs is a significant concern; adherence to current treatment guidelines is essential.
• Ongoing research and public health efforts are vital to control and eventually eradicate malaria.