Malaria in the Dominican Republic

Update: November 7, 2005

The Public Health Agency of Canada (PHAC) has been notified of a total of two cases of P. falciparum malaria in European travellers returning from the province of La Altagracia in the southeastern region of the Dominican Republic. [Map]

The initial case, referenced in the Agency's previous advisory on Malaria in the Dominican Republic dated October 20, 2005, involved a 24-year-old female tourist from France who acquired P. falciparum malaria during travel to the Bavaro area in the province of La Altagracia in August and September of 2005. A second case was later confirmed in a 20-year-old male tourist from Spain, who also travelled to the Bavaro area in late-August of 2005.

The Pan American Health Organization (PAHO) is working with the Ministry of Health in the Dominican Republic to ensure that intensive measures to interrupt transmission of malaria, including intensified surveillance and vector control, continue to be implemented in the province of La Altagracia.

The Agency continues to collaborate with the US Centers for Disease Control and Prevention (CDC) and the Pan American Health Organization in the monitoring and reporting of new cases of malaria in returning travellers from the Dominican Republic.

Source: GEOSentinel, Eurosurveillance, Pan American Health Organization

Malaria is an acute flu-like illness caused by one of four species of parasite of the genus Plasmodium; Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae. Infection with P. falciparum malaria can be fatal.

The disease is most commonly transmitted to humans through the bite of an infected mosquito, specifically the female Anopheles mosquito, a dusk-to-dawn biter.

Malaria is endemic (i.e., constantly present) in most of sub-Saharan Africa; in large areas of the Middle East, South Asia, South East Asia, Oceania, Haiti, Central and South America; and in parts of Mexico, North Africa and the Dominican Republic.

For comprehensive information, please refer to the Public Health Agency of Canada 's Disease Information Backgrounder on malaria.

P. falciparum malaria is known to be endemic (i.e., constantly occurring) in rural areas of the Dominican Republic, with the highest risk in areas bordering Haiti. On average, close to 1000 cases are reported each year. However, in 2004 this figure jumped to more than 2000 cases due to increased rainfall, an increase in the mosquito population, and increased movement of migrant workers between rural and resort areas.

Although resort areas in the Dominican Republic are generally not risk areas, small localized outbreaks have occurred in recent years in and around resorts in the province of La Altagracia.

• In 1999, a localized outbreak of malaria occurred in a tourist resort area in the province of La Altagracia. The outbreak, which spanned five-months, resulted in a total of 359 reported cases of malaria. The majority of which (76.6%) occurred in temporary construction workers from other parts of the country. An additional 16.9% occurred in local residents of the area.

• In 2004, a localized outbreak of malaria occurred in and around resort areas located in the provinces of La Altagracia. The outbreak began in mid-October 2004 and ended in January 2005. Among tourists, the outbreak resulted in a combined total of 21 confirmed cases of malaria reported in Canadian, American, and European travellers, between late-2004 and January 2005.

Recommendations

How to prevent malaria infection

Two important measures can help you prevent malaria infection: avoiding mosquito bites and using effective anti-malarial medications.

Personal Measures to Avoid Mosquitoes

Female Anopheles mosquitoes bite mainly during the evening and night. Using personal insect protective measures will reduce your risk of being bitten by these mosquitoes.

• stay in well-screened or completely enclosed, air-conditioned accommodation;
• sleep under insecticide-treated bed nets;
• wear clothing that reduces the amount of exposed skin; wear long-sleeved shirts (tightly weaved material, sleeves down, buttoned/zipped up, tucked into pants) and long pants (tucked into socks or footwear);
• light-coloured clothing may be less attractive to some mosquitoes and make mosquitoes more noticeable;
• use DEET-based products as repellents on exposed skin. The higher the concentration of DEET in the repellent formulation, the longer the duration of protection. However, this relation reaches a plateau at about 30% to 35%. DEET formulations that are "extended duration" (ED), such as polymers, are generally considered to provide longer protection times, and may be associated with less DEET absorption. Formulations over 30% are not currently available in Canada, although they are available internationally, including in the United States. It should be noted, however, that products sold outside Canada have not been evaluated by Health Canada. Most repellents containing "natural" products are effective for shorter durations than DEET and for this reason are not considered the preferred products for protecting against mosquito bites.
  
  Regulatory agencies in western nations may differ regarding the recommended maximum concentration and application rates of DEET, especially for children. The Committee to Advise on Tropical Medicine and Travel (CATMAT) is satisfied that, for travel outside of Canada where the risk of malaria outweighs the risk of any important adverse reaction to DEET, the threshold for use of DEET should be low.
  
  CATMAT recommends that concentrations of DEET up to 35% can be used by any age group.
  
  For children, alternative personal protective measures, such as mosquito nets treated with insecticide, should be the first line of defense, especially for infants less than 6 months of age. Portable mosquito nets, including self-standing nets, placed over a car seat, a crib, playpen, or stroller help protect against mosquitoes. However, as a complement to the other methods of protection, the judicious use of DEET should be considered for children of any age. Recent medical literature from Canada suggests that DEET does not pose a significant or substantial extra risk to infants and children.
  
  DEET/sunscreen combination products are not generally recommended, because DEET can decrease the efficacy of sunscreens. As well, sunscreens should be used liberally and often while DEET should be used sparingly and only as often as required. If application of both is necessary, the Canadian Dermatology Association recommends that the sunscreen be applied first and allowed to penetrate the skin for 20 minutes, prior to applying DEET.

These precautions will also help to prevent other mosquito-borne infections such as dengue fever.

Antimalarial Medication (Prophylaxis)

Antimalarial medications decrease the risk of developing symptomatic malaria. However, they do not provide 100% protection against the disease. Your individual need for antimalarial medications should be discussed with your physician or travel medicine professional several weeks before travel.

If your physician or travel medicine clinic prescribes an antimalarial medication, it is important that you take it as directed in order to maximize the protective effect. Each drug has its own dosing regime that should be strictly followed. Because of the incubation period of the disease, these medications must be taken both before, during, and after travel.

Travellers are reminded to complete their prescribed regimen of prophylaxis on their return. Except for atovaquone/proguanil which must be taken for one week after returning from a malaria-endemic area, chloroquine, doxycyline and mefloquine must be taken for four weeks after returning from a malaria-endemic area.

For travellers who opt not to take malaria prophylaxis during their travel to La Altagracia, PHAC does not recommend that they start chemoprophylaxis on their return home to Canada but advises that individuals seek immediate medical attention should they develop a fever and inform their physician that they have visited an area where malaria occurs so that they can be tested without delay.

Important to Note

If you develop a fever within 3 months after returning from an area where malaria occurs, you should seek medical advice immediately. Be sure to inform your physician that you have visited an area where malaria occurs so that you can be tested without delay. Malaria must be ruled out by the examination of one or more blood films under a microscope.

As a reminder...

The Public Health Agency of Canada routinely recommends that Canadian international travellers consult their personal physician or a travel clinic prior to international travel, regardless of destination, for an individual risk assessment to determine their individual health risks and their need for vaccination, preventative medication, and personal protective measures.

The Public Health Agency of Canada recommends, as well, that travellers who become sick or feel unwell on their return to Canada should seek a medical assessment with their personal physician. Travellers should inform their physician, without being asked, that they have been travelling or living outside of Canada, and where they have been.

For additional information on malaria:

• Visit the Public Health Agency of Canada's Disease Information Backgrounder on Malaria.
• The Committee to Advise on Tropical Medicine and Travel (CATMAT) produces evidence based statements and guidelines. For maps of malaria-endemic areas and other information about malaria, visit CATMAT's Canadian recommendations for the prevention and treatment of malaria among international travellers as published in the Canada Communicable Disease Report - Supplement (Vol. 30, June 2004).
• Malaria - Frequently Asked Questions