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Malaria

Malaria

14 June 2016

Causative agent

Malaria is a serious and sometimes fatal disease caused by a group of malaria parasites, namely Plasmodium vivax, Plasmodium falciparum, Plasmodium ovale, and Plasmodium malariae. It is commonly found in many parts of tropical and sub-tropical areas where the climate is warm, like Africa, South-East Asia and South America.

Clinical features

Symptoms of malaria include intermittent fever, chills, sweating, headache, tiredness, nausea, vomiting and muscle pain. In typical cases, the fever comes, then subsides for 1 – 3 days and then comes again in a cyclical pattern. Complications include anaemia, liver and kidney failure, seizures, mental confusion, coma, and death if the disease is not treated promptly.


Mode of transmission

Malaria is a vector-borne communicable disease transmitted by an infected female Anopheline mosquito. When the mosquito bites a malaria patient, the mosquito becomes infected and will pass on the disease when it bites another person. Malaria is not transmitted from person to person. However, malaria can be transmitted through contaminated blood or blood product transfusion, organ transplant, or shared needles or syringes. Malaria may also be transmitted from a mother to her foetus/newborn baby before or during delivery.

Incubation period

The incubation period varies with different species of Plasmodium. This usually ranges from 7 – 30 days but may be up to months or even longer after the bite of an infected Anopheline mosquito.

Management

There are effective drugs against malaria but early diagnosis and prompt treatment are crucial. The doctor would prescribe a course of anti-malarial drugs with other supportive measures. The patient should complete the whole course of medication to ensure clearance of the malaria parasites.

Prevention

  1. Take measures to avoid mosquito bite.
     
  2. There are currently no licensed vaccines against malaria.
     
  3. Malaria infection during pregnancy can have adverse effects on both the mother and the foetus. Therefore, pregnant women should not visit malarious areas unless this is absolutely necessary.
     

General Measures on Preventing Mosquito-borne Diseases

  1. Wear loose, light-coloured, long-sleeved tops and trousers, and use DEET-containing insect repellent on exposed parts of the body and clothing.
     
  2. Take additional preventive measures when engaging in outdoor activities:

    • Avoid using fragrant cosmetics or skin care products
       
    • Re-apply insect repellents according to instructions
       
  3. Special notes when travelling abroad:

    • If you travel to areas where malaria is common, arrange a consultation with doctor at least 6 weeks before the trip for preventive measures and obtain anti-malarial drugs for prophylaxis if necessary. The prescription of anti-malarial medication depends on several factors including but not limited to the itinerary, time of travel, types of activity and past medical history of the traveller. If you decide to take such medication, you should start taking the drugs before the trip, continue throughout the journey and until some time after leaving the area according to the instruction of the doctor.
       
    • During the trip, if travelling in endemic rural areas, carry a portable bed net and apply permethrin (an insecticide) on it. Permethrin should NOT be applied to skin. Seek medical attention promptly if feeling unwell.
       
    • During your visit abroad or after coming back to Hong Kong, if you have symptoms of malaria, seek medical advice immediately and provide travel details to the doctor. Urgent blood tests may be performed and prompt treatment is vital.
       

Help prevent mosquito proliferation

  1.  Prevent accumulation of stagnant water

    • Change the water in vases once a week
       
    • Clear the water in the saucers under potted plants every week
       
    • Cover water containers tightly
       
    • Ensure air-conditioner drip trays are free of stagnant water
       
    • Put all used cans and bottles into covered dustbins
       
  2. Control vectors and reservoir of the diseases
     
    •  Store food and dispose of garbage properly

Pregnant women and children of 6 months or older can use DEET-containing insect repellent. For details about the use of insect repellents and the key points to be observed, please refer to 'Tips for using insect repellents'.

For more information about control and prevention of mosquito breeding, please visit the website of the Food and Environmental Hygiene Department (FEHD) at http://www.fehd.gov.hk/english/safefood/handbook_prev_mos_breeding.html
 

Related link: World Health Day 2014


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