Plasmodium vivax malaria: symptoms, relapses and treatment

Malaria is a serious infection spread by mosquitoes found in some parts of the world, caused by Plasmodium parasites. NHS inform lists five types that infect people: falciparum, vivax, ovale, malariae and knowlesi. They are found in different parts of the world, with some overlap, and they differ in how severe infection can be.

NHS inform says Plasmodium vivax is mainly found in Asia and South America. The same source says it tends to cause milder symptoms, but that the parasite can remain in the liver for years, so symptoms can come back if it is not treated properly. This dormant stage is the main thing that distinguishes vivax from falciparum malaria in practice.

Malaria is not found in the UK and cannot usually be caught from another person. The NHS says it is caused by being bitten by an infected mosquito, and that it can take just one bite. Rarely it can pass from a mother to her unborn baby or through a needlestick injury; NHS inform also mentions transfusion and shared needles.

All types of malaria cause the same sort of symptoms. NHS inform describes them as similar to flu and says they can start mild and be difficult to identify. The NHS lists the following:

• A high temperature, or feeling hot, cold or shivery.

• Sweating and headaches.

• Feeling confused, tired and sleepy.

• Feeling or being sick, tummy pain and diarrhoea.

• Loss of appetite and muscle pains.

• Yellow skin or whites of the eyes (jaundice).

• Sore throat, cough and difficulty breathing.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have malaria symptoms and have travelled to a country where malaria is found in the last 12 months, and to tell anyone you travelled with to get help straight away. NHS inform says to phone 111 or go to A&E if you or your child develops symptoms during or after a visit to an area where malaria is found, even if it is several weeks, months or a year later, and to tell staff about every country visited, including brief stopovers.

The NHS says to get medical advice quickly if symptoms start while you are travelling, without waiting to get home. NHS inform notes that the effects are usually more severe in babies, young children, pregnant women and older people, and that severe complications can occur within hours or days of the first symptoms.

NHS inform explains the life cycle in simple terms. When an infected mosquito bites, the parasite enters the blood and travels to the liver, where it develops for days to weeks before re-entering the blood. That is when symptoms start. In vivax malaria the parasite can also remain in the liver for much longer, which is why symptoms can reappear after an apparent recovery.

The NHS notes that malaria can sometimes come back and will need to be treated again if this happens. For people who have had vivax malaria, this means telling any doctor about it if a fever develops months later, even if you are no longer travelling. Which medicines are used, and for how long, depends on the type of malaria, which is why identifying the species matters.

Malaria is diagnosed with a blood test that looks for the parasite, which also identifies the species. Because symptoms from different species look alike, the blood film or rapid test is what tells vivax from falciparum.

NHS inform says that if malaria is diagnosed and treated quickly you should fully recover. It says treatment begins in hospital to make sure complications do not suddenly develop, that it is given as tablets or capsules, and that a drip into a vein is used if someone is very ill. The medicine and the duration depend on the type of malaria, the severity of symptoms, whether you took preventive tablets, your age and whether you are pregnant. Treatment can leave you feeling very tired and weak for several weeks.

NHS inform lists anaemia, cerebral malaria, liver failure and jaundice, shock, fluid on the lungs, low blood sugar and kidney failure among the complications that can occur in severe malaria generally, and says they can develop within hours or days of the first symptoms, which is the reason prompt assessment is advised for everyone.

The NHS says to get advice from a GP, nurse, pharmacist or travel clinic at least 4 to 6 weeks before you travel, though last-minute advice is still worth having. You may be prescribed antimalarial tablets and told how to prevent bites. NHS inform summarises this as the ABCD approach: awareness of risk, bite prevention, check whether you need antimalarial tablets, and diagnosis if symptoms develop.

Bite prevention includes covering arms and legs in the evening, using a repellent with 50% DEET, and sleeping under an insecticide-treated net. The NHS says that if you were born or used to live in a high-risk country you are not immune any more, so you still need protection. There is currently no vaccine that protects against malaria, according to NHS inform.

Antimalarial tablets must be taken before, during and for a period after travel, and the NHS says to take them as prescribed. Not all tablets are suitable in pregnancy, so specific advice is needed. The Travel Health Pro website provides country-by-country information on malaria risk.

Pre-travel malaria advice is available through GP practices, pharmacies and travel clinics; some elements may carry a charge, and antimalarial tablets are often bought on a private prescription. Diagnosis and treatment of suspected malaria in the UK is provided through NHS urgent care and hospital infectious diseases services.

Private travel clinics offer tablets and advice before a trip, and private hospitals can treat malaria, but anyone who becomes feverish after travel in a malaria area should be assessed urgently the same day through whichever service is quickest.