MALARIA
Symptoms of malaria typically appear 10-15 days after the infective mosquito bite and include:
- Fever
- Chills
- Headache
- Nausea and vomiting
- Muscle pain and fatigue
- Sweating
- Anemia (due to the destruction of red blood cells)
- Jaundice (yellowing of the skin and eyes due to liver damage)
In severe cases, malaria can cause complications such as:
- Cerebral malaria (affecting the brain)
- Severe anemia
- Acute respiratory distress syndrome (ARDS)
- Organ failure
| Type of Malaria | Prevalence | Severity | Characteristics |
|---|---|---|---|
| Plasmodium falciparum | Sub-Saharan Africa, South Asia, Southeast Asia | Most severe, causes majority of malaria-related deaths | Severe anemia, cerebral malaria, multi-organ failure, irregular fever patterns |
| Plasmodium vivax | Asia, Latin America, parts of Africa | Less severe than P. falciparum but causes significant illness | Relapsing malaria due to dormant liver stages (hypnozoites), tertian fever patterns (every 48 hours) |
| Plasmodium ovale | West Africa, other parts of Africa, western Pacific islands, Southeast Asia | Less severe than P. falciparum, similar to P. vivax | Causes relapses due to hypnozoites, tertian fever patterns (every 48 hours) |
| Plasmodium malariae | Worldwide, less common than P. falciparum and P. vivax | Milder form of malaria, chronic infections can persist for years | Quartan fever pattern (every 72 hours), chronic infections can lead to nephrotic syndrome (a serious kidney condition) |
| Plasmodium knowlesi | Southeast Asia, particularly Malaysia | Can cause severe, rapidly progressing infections similar to P. falciparum | Originally a parasite of macaques, can be transmitted to humans, daily fever patterns (every 24 hours) |
Vaccination for malaria has been a significant focus of research and development due to the global impact of the disease. Here is an overview of the current status and progress in malaria vaccines:
RTS,S/AS01 (Mosquirix)
- Developer: GlaxoSmithKline (GSK) in partnership with the PATH Malaria Vaccine Initiative and supported by the Bill & Melinda Gates Foundation.
- Target Parasite: Plasmodium falciparum.
- Mechanism: The RTS,S/AS01 vaccine targets the circumsporozoite protein (CSP) of the malaria parasite, which is crucial for the parasite's ability to infect liver cells.
- Efficacy: Provides partial protection, with efficacy varying by age and number of doses. In clinical trials, it reduced malaria cases by about 30-50% in young children.
- Implementation: Approved by the World Health Organization (WHO) in 2021. Pilot programs have been launched in several African countries, including Ghana, Kenya, and Malawi, to assess real-world effectiveness and feasibility.
R21/Matrix-M
- Developer: University of Oxford in collaboration with the Serum Institute of India and Novavax.
- Target Parasite: Plasmodium falciparum.
- Mechanism: Similar to RTS,S, this vaccine also targets the CSP of the malaria parasite but includes a different adjuvant (Matrix-M) to enhance immune response.
- Efficacy: Preliminary studies have shown higher efficacy rates compared to RTS,S, with up to 77% efficacy in initial trials.
- Status: Undergoing further clinical trials to confirm efficacy and safety before broader implementation.
Other Candidates
- SPf66: An earlier vaccine candidate developed in Colombia, showed variable efficacy in trials and is no longer pursued.
- PfSPZ Vaccine: Developed by Sanaria Inc., it uses live, attenuated sporozoites to induce immunity. It has shown promise in early-phase trials but requires more extensive testing.
Challenges and Future Directions
- Efficacy: While current vaccines like RTS,S and R21 show partial efficacy, there is a need for vaccines with higher and more durable protection.
- Multiple Strains: Plasmodium falciparum's genetic diversity poses a challenge for creating a universally effective vaccine.
- Combination Approaches: Research is ongoing into combining vaccines with other malaria control measures such as bed nets, antimalarial drugs, and vector control strategies.
- Long-term Immunity: Efforts are focused on developing vaccines that provide long-lasting immunity, potentially reducing the need for frequent booster doses.
Adjuvant technology refers to the use of substances in vaccines that enhance the body's immune response to the provided antigen. These substances, called adjuvants, are crucial for improving the efficacy of vaccines, especially those that rely on weaker antigens or aim to induce a stronger and longer-lasting immunity. Here's a detailed overview of adjuvant technology:
Purpose of Adjuvants
- Enhance Immune Response: Adjuvants help to boost the magnitude and duration of the immune response to an antigen.
- Dose Sparing: By enhancing the immune response, adjuvants can reduce the amount of antigen needed in each vaccine dose.
- Broadening Immunity: They can help generate a more comprehensive immune response, including both humoral (antibody-mediated) and cellular immunity.
- Improving Efficacy in Diverse Populations: Adjuvants can enhance vaccine efficacy in populations with weaker immune responses, such as the elderly or immunocompromised individuals.
Types of Adjuvants
Several types of adjuvants are used in vaccines, each with different mechanisms of action. Some common adjuvants include:
-
Aluminum Salts (Alum):
- Description: One of the oldest and most widely used adjuvants.
- Mechanism: Enhances antigen uptake by antigen-presenting cells and stimulates a strong antibody response.
- Use: Found in vaccines for diseases like hepatitis B and diphtheria-tetanus.
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Oil-in-Water Emulsions:
- Examples: MF59, AS03.
- Mechanism: Enhance the recruitment and activation of immune cells at the injection site.
- Use: Found in influenza vaccines.
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Saponin-Based Adjuvants:
- Examples: QS-21.
- Mechanism: Enhance both antibody and cell-mediated immune responses.
- Use: Found in vaccines for malaria (RTS,S) and herpes zoster (Shingrix).
-
Toll-like Receptor (TLR) Agonists:
- Examples: CpG 1018, MPL (Monophosphoryl lipid A).
- Mechanism: Mimic microbial components to activate innate immune responses.
- Use: Found in hepatitis B vaccines (Heplisav-B) and HPV vaccines (Cervarix).
-
Liposomes:
- Description: Spherical vesicles that can encapsulate antigens and adjuvants.
- Mechanism: Enhance antigen delivery and stimulate strong immune responses.
- Use: Under research for various vaccines.
Role in Malaria Vaccines
In malaria vaccines, adjuvants are essential for inducing a robust immune response against the malaria parasite, which has a complex life cycle and various evasion strategies.
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RTS,S/AS01:
- Adjuvant: AS01, which includes MPL and QS-21.
- Mechanism: Enhances both antibody and cell-mediated responses, crucial for targeting the liver stage of Plasmodium falciparum.
-
R21/Matrix-M:
- Adjuvant: Matrix-M, a saponin-based adjuvant.
- Mechanism: Stimulates strong immune responses, potentially offering higher efficacy than RTS,S.
The recently released World Malaria Report shows that the number of cases and deaths due to the mosquito-borne infection in India has continued to decline.India’s downward trend was reflected in the larger WHO South East Asian region that remained on track to achieving the 2030 target of reducing cases and deaths by 90 percent, the report said.
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For Prelims: General Science, Current Events of National and International Importance For Mains: GS-II, III: Social Justice and International Relations; Achievements of Indians in Science & Technology, Developments and their Applications and Effects in Everyday Life |
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Previous Year Questions
1.Widespread resistance of malarial parasite to drugs like chloroquine has prompted attempts to develop a malarial vaccine to combat malaria. Why is it difficult to develop an effective malaria vaccine? (UPSC CSE 2010)
(a) Malaria is caused by several species of Plasmodium Answer (b) The answer is (b) Man does not develop immunity to malaria during natural infection. Here's why the other options are incorrect: (a) Malaria is caused by several species of Plasmodium - While this is true, it doesn't directly explain the difficulty in developing a vaccine. A vaccine can target multiple strains as needed. (c) Vaccines can be developed only against bacteria - This is not true. We have vaccines for many viral diseases as well. (d) Man is only an intermediate host and not the definitive host - This is a fact about the parasite's life cycle, but it doesn't impact vaccine development. |
