Malaria prophylaxis
Malaria prophylaxis is the preventive treatment of malaria. Several malaria vaccines are under development.
For pregnant women who are living in malaria endemic areas, routine malaria chemoprevention is recommended. It improves anemia and parasite level in the blood for the pregnant women and the birthweight in their infants.[1]
Strategies
- Risk management
- Bite prevention—clothes that cover as much skin as possible, insect repellent, insecticide-impregnated bed nets and indoor residual spraying
- Chemoprophylaxis
- Rapid diagnosis and treatment
Recent improvements in malaria prevention strategies have further enhanced its effectiveness in combating areas highly infected with the malaria parasite. Additional bite prevention measures include mosquito and insect repellents that can be directly applied to skin. This form of mosquito repellent is slowly replacing indoor residual spraying, which is considered to have high levels of toxicity by World Health Organization (WHO). Further additions to preventive care are sanctions on blood transfusions. Once the malaria parasite enters the erythrocytic stage, it can adversely affect blood cells, making it possible to contract the parasite through infected blood.
Chloroquine may be used where the parasite is still sensitive, however many malaria parasite strains are now resistant.[2] Mefloquine (Lariam), doxycycline, or the combination of atovaquone and proguanil (Malarone) are frequently recommended.[2]
Medications
In choosing the agent, it is important to weigh the risk of infection against the risks and side effects associated with the medications.[3]
Disruptive prophylaxis
An experimental approach involves preventing the parasite from binding with red blood cells by blocking
Suppressive prophylaxis
Chloroquine, proguanil, mefloquine, and doxycycline are suppressive prophylactics. This means that they are only effective at killing the malaria parasite once it has entered the erythrocytic stage (blood stage) of its life cycle, and therefore have no effect until the liver stage is complete. That is why these prophylactics must continue to be taken for four weeks after leaving the area of risk.
Mefloquine, doxycycline, and atovaquone-proguanil appear to be equally effective at reducing the risk of malaria for short-term travelers and are similar with regard to their risk of serious side effects.[2] Mefloquine is sometimes preferred due to its once a week dose, however mefloquine is not always as well tolerated when compared with atovaquone-proguanil.[2] There is low-quality evidence suggesting that mefloquine and doxycycline are similar with regards to the number of people who discontinue treatments due to minor side effects.[2] People who take mefloquine may be more likely to experience minor side effects such as sleep disturbances, depressed mood, and an increase in abnormal dreams.[2] There is very low quality evidence indicating that doxycycline use may be associated with an increased risk of indigestion, photosensitivity, vomiting, and yeast infections, when compared with mefloquine and atovaquone-proguanil.[2]
Causal prophylaxis
Causal prophylactics target not only the blood stages of malaria, but the initial liver stage as well. This means that the user can stop taking the drug seven days after leaving the area of risk.
Regimens
Specific regimens are recommended by the
These regimens include:
- doxycycline 100 mg once daily (started one day before travel, and continued for four weeks after returning);
- mefloquine 250 mg once weekly (started two and a half weeks before travel, and continued for four weeks after returning);
- atovaquone/proguanil (Malarone) 1 tablet daily (started one day before travel, and continued for one week after returning). Can also be used for therapy in some cases.
In areas where chloroquine remains effective:
- chloroquine 300 mg once weekly, and proguanil 200 mg once daily (started one week before travel, and continued for four weeks after returning);
- hydroxychloroquine 400 mg once weekly (started one to two weeks before travel and continued for four weeks after returning)
What regimen is appropriate depends on the person who is to take the medication as well as the country or region travelled to. This information is available from the UK HPA, WHO or CDC (links are given below). Doses depend also on what is available (e.g., in the US, mefloquine tablets contain 228 mg base, but 250 mg base in the UK). The data is constantly changing and no general advice is possible.
Doses given are appropriate for adults and children aged 12 and over.
Other chemoprophylactic regimens that have been used on occasion:
- Dapsone 100 mg and pyrimethamine 12.5 mg once weekly (available as a combination tablet called Maloprim or Deltaprim): this combination is not routinely recommended because of the risk of agranulocytosis;
- Primaquine 30 mg once daily (started the day before travel, and continuing for seven days after returning): this regimen is not routinely recommended because of the need for G-6-PD testing prior to starting primaquine (see the article on primaquine for more information).
- Quinine sulfate 300 to 325 mg once daily: this regimen is effective but not routinely used because of the unpleasant side effects of quinine.
Prophylaxis against Plasmodium vivax requires a different approach given the long liver stage of this parasite.[11] This is a highly specialist area.
Vaccines
In November 2012, findings from a Phase III trials of an experimental malaria vaccine known as RTS,S reported that it provided modest protection against both clinical and severe malaria in young infants. The efficacy was about 30% in infants 6 to 12 weeks of age and about 50% in infants 5 to 17 months of age in the first year of the trial.[12]
The RTS,S vaccine was engineered using a fusion
Risk factors
Most adults from endemic areas have a degree of long-term infection, which tends to recur, and also possess partial
History
Malaria is one of the oldest known pathogens, and began having a major impact on human survival about 10,000 years ago with the birth of agriculture. The development of virulence in the parasite has been demonstrated using genomic mapping of samples from this period, confirming the emergence of genes conferring a reduced risk of developing the malaria infection. References to the disease can be found in manuscripts from
Quinine remained the only available treatment for malaria until the early 1920s. During the
The development of new
The CDC publishes recommendations for travels advising about the risk of contracting malaria in various countries.[15]
Some of the factors in deciding whether to use chemotherapy as malaria pre-exposure prophylaxis include the specific itinerary, length of trip, cost of drug, previous adverse reactions to antimalarials, drug allergies, and current medical history.[15]
See also
- Malaria prevention
- Mosquito control
References
- PMID 25300703.
- ^ PMID 29083100.
- ISBN 978-0-7817-3894-1. Retrieved 13 November 2010.
- ^ a b "Shutting the door on Malaria offers new vaccine hope". 19 December 2013.
- PMID 24280897.
- US Centers for Disease Control and Prevention. April 15, 2010. Archived from the originalon 14 January 2009. Retrieved 2012-05-02.
- ^ The World Health Organization provides country-specific advice on malaria prevention.
- ^ 2007 guidelines are available from the UK Health Protection Agency Archived 2013-09-28 at the Wayback Machine website as a PDF file and includes detailed country-specific information for UK travellers.
- ^ "Malaria: guidance, data and analysis". Public Health England. June 19, 2013. Retrieved September 10, 2014.
- ^ the Centers for Disease Control and Prevention website hosts constantly updated country-specific information on malaria. The advice on this website is less detailed, is very cautious and may not be appropriate for all areas within a given country. This is the preferred site for travellers from the US.
- PMID 14561793.
- S2CID 13944101.
- PMID 20553771.
- ^ Stein R (18 October 2011). "Experimental malaria vaccine protects many children, study shows". Washington Post.
- ^ a b Tan KR, Mali S, Arguin PM (2010). "Malaria Risk Information and Prophylaxis, by Country". Travelers' Health - Yellow Book. Centers for Disease Control and Prevention. Retrieved 20 December 2010.