Malaria is one of the world's greatest public health problems. It infects approximately 219 million people each year (range 154 – 289 million), with an estimated 660,000 deaths, mostly children in Africa. It is caused by four species of protozoan parasites of the genus Plasmodium: P. falciparum, P. vivax, P. malariae, and P. ovale and is transmitted by Anopheles species mosquitoes.
- Symptoms and Transmission
- Malaria Occurrence in Florida
- Malaria Risk in Travelers Visiting Friends and Relatives
- Resources and References
Symptoms of malaria depend on the Plasmodium species, but in most cases develop between seven and thirty days after the bite of an infected mosquito. P. vivax can develop up to a year after exposure and if not treated properly can cause additional attacks (“relapses”). Commonly, people experience flu-like symptoms such as fever, chills, sweats, headache, nausea and vomiting, body aches, and general malaise. P. falciparum can cause severe and life-threatening disease.
P. falciparum and P. vivax were previously present in Florida, but was eradicated from the state in the late 1940s. Local transmission has occurred only rarely in recent years, likely due to mosquito control measures, improved housing with screens, use of repellents, and drainage practices. A number of malaria cases are reported in immigrant and travelers to areas where malaria risk is high. There are 14 Anopheles mosquito species in Florida, all of which are potentially capable of transmitting malaria. An. quadrimaculatus and An. crucians have been major malaria vectors in the past. Since introduction from endemic areas occurs regularly and competent vectors exist in the state, local transmission is possible.
Prophylaxis and other prevention methods (bednets, mosquito repellent) can be effective in preventing malaria. In 2012, only 22% of cases reported taking prophylaxis and only 23% reported using some other prevention method. 65% of cases used neither prophylaxis nor other prevention methods.
Preventing Mosquito Bites
If possible, remain indoors in a screened or air-conditioned area during the peak biting period between dusk and dawn:
- If no screening or air conditioning is available, use pyrethroid-containing repellent in living and sleeping areas during evening and night-time hours and sleep under bed nets, preferably insecticide-treated.
- Wear long-sleeved shirts, long pants, and hats when outdoors.
- Use insect repellent when outdoors. Sprays that contain DEET (N,N-diethyl-meta-toluamide) offer good protection . Follow the directions on the product label.
- Higher concentrations of DEET may have a longer repellent effect; however, concentrations over 50% provide no added protection. Timed-release DEET products may have a longer repellent effect than liquid products.
- DEET should not be used on children younger than two months. Assist children less than 10 years old with application of repellant. Avoid applying repellant to young children’s hands, or around their eyes and mouth.
- Protect infants by using a carrier draped with mosquito netting with an elastic edge for a tight fit.
The largest outbreak in recent Florida history occurred in Palm Beach County in 2003 where there were eight cases. In 2012, 65 cases of imported malaria were reported in Florida. Forty-five cases (69%) were diagnosed with P. falciparum, 16 (25%) with P. vivax, two (3%) with P. ovale, two with P. malariae (3 %). All 65 cases were associated with travel or immigration. Reasons given for traveling to a malaria endemic county included: 43% visiting friends and relatives (VFR), 29% for business (including missionary and military), 9% of cases were recent immigrants, 8% tourism, 5% students or teachers, and 6% unknown reason.
Travelers to high malaria risk countries should talk to their healthcare provider about malaria prophylaxis and should take personal mosquito control measures. Those classified as visiting friends and relatives (VFRs) are primarily immigrants from malaria-endemic developing countries. Immigrants returning to their home country may be at increased risk for malaria. This increased risk has been attributed to high risk behaviors such as longer visit times and staying in villages and remote rural areas without screened windows or air conditioning. Additionally, VFRs are more likely to neglect personal protective measures against mosquitoes, such as prophylactic drugs, insect repellents, and bed nets. This may be because they believe themselves to be immune to the disease after having lived in an endemic area in the past. However, any immunity they may have had is lost over time, leaving them vulnerable to serious infections when they return to their home country. Their children who were born in the U.S. have no protective immunity.
VFRs are also less likely than other travelers to seek pre-departure medical advice. This may be associated with the cost of a physician visit. Insurance rates in this population are low, and even for those who are insured, visits to a travel medicine specialist and chemoprophylaxis are often not covered. Primary care providers may not have the most up-to-date information about malaria distribution and drug resistance. A Canadian study of VFRs traveling to India showed that family practitioners were the primary source of information and that only 31% of travelers planned to use prophylaxis, less than 10% intended to use personal protective measures, and only 7% had been prescribed appropriate prophylaxis for their destination. Some travelers also plan to buy prophylaxis at their destination, but these may contain the wrong drug, an incorrect amount of drug, or be contaminated.
Because of these risks, it is important to target messages to immigrant populations that may plan trips to their home countries. Promotion of travel medicine services as well as educational materials can be distributed through appropriate-language pamphlets, posters, and other ethnic media and community organizations such as churches. Primary care clinics that treat large numbers of immigrants should be encouraged to provide travel medicine training to practitioners to ensure they can provide high quality travel medicine services in a familiar and accessible setting. The practitioner should review the traveler's itinerary to provide specific guidelines and determine what type of chemoprophylaxis, if any, is recommended based on anti-malarial resistance and malaria risk in the area of travel. Convenience and low side effects are important considerations to increase compliance. The traveler should also understand the symptoms of malaria such as fever, chills, headache, muscle aches, fatigue, nausea, jaundice, vomiting, and diarrhea, so that they can seek medical attention if they become sick. In some cases, they can be prescribed stand-by medication for use if symptoms appear.
Educational materials should include information about malaria and preventive measures such as personal protection against mosquitoes and chemoprophylaxis. Mosquito avoidance practices are similar to those employed in the United States: staying inside with screened doors and windows during peak biting times from dusk to dawn, wearing clothing that covers the skin, and using insecticides and repellents, but should also include insecticide impregnated bed nets. These measures also protect against other tropical mosquito-borne diseases, such as dengue and Chikungunya, making the message even more important. The overall VFR campaign could also include information on preventing other diseases that they are at risk for, including food-borne diseases and tuberculosis.Antimalarial Drug Guidelines
- Visit a healthcare provider familiar with travel medicine 4-6 weeks before traveling to countries that are endemic for malaria to obtain helpful travel information, vaccinations for other diseases, and antimalarial drug prescriptions.
Purchase antimalarial drugs before traveling overseas to make sure that they are effective. Drugs bought in other countries may not be protective.
- Take all drugs as prescribed before, during and after travel for complete protection. Partial use may result in infection.
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