International Notes - Transmission of Malaria in Resort Areas - Dominican Republic, 2004

Malaria is caused by any of four Plasmodium parasites carried by Anopheles mosquitoes and usually is transmitted by the bite of an infective female Anopheles. In rural areas of the Dominican Republic, P. falciparum malaria is endemic, with the highest risk in the far western region of the country, and prophylactic medication with chloroquine is recommended for incoming travellers. Conversely, urban and resort areas in the Dominican Republic have been considered nonmalarious, and prophylactic medication has not been recommended for persons travelling to these areas⁽¹⁾. However, since November 2004, the Centers for Disease Control and Prevention (CDC) has received reports of three malaria cases in U.S. travellers returning from areas in La Altagracia and Duarte provinces previously considered nonmalarious. An additional 14 cases of malaria in La Altagracia Province, in the far eastern region of the country, have been reported in European and Canadian travellers. This report describes three of these 17 malaria cases and summarizes the overall investigation, which led to expansion of CDC recommendations for chloroquine prophylaxis to include all of La Altagracia and Duarte provinces.

Case Reports

Case 1. During the third week of November 2004, a woman aged 47 years was admitted to an intensive care unit (ICU) in the United States with multisystem organ failure, including acute respiratory distress syndrome and renal failure. She had a 6-day history of fever, chills, abdominal pain, headache, nausea, and vomiting that began 24-36 hours after returning from a 1-week vacation to a resort in Punta Cana in La Altagracia Province. The patient had been examined twice by a health-care provider in an outpatient setting and sent home. Two days before hospital admission, she had jaundice. On admission, the patient had P. falciparum malaria on blood smear (35% parasitemia), anemia (hemoglobin: 10.4 g/dL [normal: 12-18 g/dL]), leukocytosis (white blood cell count: 35,000/FL [normal: 5,000-10,000/FL]), severe thrombocytopenia (platelet count: 5,000/FL [normal: 130,000- 400,000/FL]), and was obtunded. The patient was started on intravenous quinidine gluconate, and the parasitemia cleared in 2 days. On the fifth day of hospitalization, the quinidine was discontinued, and the patient was placed on doxycycline. The patient underwent hemodialysis for renal failure; she improved and was discharged to a rehabilitation center, where she remained as of December 30, 2004. Her husband reported that they had stayed at an all-inclusive resort in Punta Cana during their entire week in the Dominican Republic and did not travel to other areas. In addition, the patient had not travelled to any other malarious areas nor received any blood transfusions during the preceding year.

Case 2. In late November, a man aged 71 years visited an emergency department in Canada 10 days after returning home from a week at a resort in Punta Cana and after 4 days of fever, myalgias, and malaise. Viral infection was diagnosed, and the man was discharged home. The next day, he saw his family doctor, who also diagnosed a viral illness. The following day, the patient's condition deteriorated substantially, and he was admitted to the hospital with hypotension, hypoxia, acute renal failure, and respiratory failure requiring mechanical ventilation. Two days after admission, the patient had a blood smear that demonstrated a 9% P. falciparum parasitemia. He was treated with intravenous quinidine and doxycycline and underwent hemodialysis. The patient reported taking a day trip to Santo Domingo while in the Dominican Republic but reported no other travel. During the preceding year, he had not travelled to any other malarious areas nor received any blood transfusions. As of 30 December, the patient remained hospitalized.

Case 3. In late November, a man aged 39 years was admitted to an ICU in Canada 12 days after returning home from a resort in Punta Cana, where he had stayed for 2 weeks. The patient reported having fevers and chills for 9 days and later had jaundice. One day after admission, he had a blood smear revealing 2% P. falciparum parasitemia and was treated with chloroquine and quinine. The patient was anemic and had acute respiratory distress syndrome, acute renal failure, and cerebral malaria; he underwent exchange transfusion. During the preceding year, the patient had not travelled to any other malarious areas nor received any blood transfusions. As of 30 December, the patient remained hospitalized.

Epidemiologic Investigation

After receiving reports of malaria in two U.S. travellers to the Dominican Republic, CDC contacted the Pan American Health Organization, World Health Organization, and Ministry of Health (MoH) in the Dominican Republic, which initiated investigations. Seventeen patients (i.e., three from the United States, six from Canada, and eight from European countries) were identified*. P. falciparum malaria was confirmed in all of them. Sixteen of the patients had travelled to Punta Cana resorts in La Altagracia Province and one to San Francisco de Macorís in Duarte Province. Sixteen returned home during 3 to 16 November and one returned 20 December; all were admitted to hospitals, and six required treatment in ICUs. As of 30 December, no deaths had been reported; three patients remained hospitalized. Seven of the patients confirmed that they had not travelled to any other malarious areas nor received any blood transfusions during the preceding year.

Prevention and Control Measures

On 24 November, CDC expanded its recommendations for chloroquine prophylaxis for travellers to the Dominican Republic to include all of La Altagracia and Duarte provinces, in addition to rural areas countrywide⁽²⁾. The revised recommendations advise clinicians and travellers about the expanded malaria risk area so that any febrile persons who have visited these areas will receive prompt diagnosis and treatment to avoid severe complications. Major networks of blood collection agencies and the Food and Drug Administration also were contacted. Similar alerts were issued by health officials in Europe and by the Public Health Agency of Canada.

The MoH investigation included active case detection and entomologic investigations in La Altagracia and Duarte provinces. In Duarte Province, officials confirmed that no other cases had been reported during 2003-2004. Nonetheless, MoH is taking precautionary measures, including enhanced surveillance. In La Altagracia Province, MoH surveillance data have identified an increase in cases of malaria beginning in November 2004 among migrant workers in the Bavaro Zone, 10 miles from the Punta Cana resort area. MoH intensified control measures in the Bavaro Zone, which included: 1) presumptive treatment of all construction and hotel workers by using directly observed therapy with chloroquine and primaquine, and 2) mosquito control through residual and spatial insecticide spraying and application of larvicide to suspected breeding sites. Measures instituted in the Punta Cana resort area include intensified surveillance and larvicide application.

MMWR Editorial Note

This report describes an outbreak of malaria in areas in the Dominican Republic previously thought to be nonmalarious. P. falciparum is the only malaria parasite in the Dominican Republic and has remained susceptible to chloroquine. Because P. falciparum malaria can be rapidly fatal, travellers should be aware of risk areas so that they can take appropriate preventive measures; clinicians should consider malaria in their diagnosis and treatment of febrile illness in travellers. Malaria can be prevented by taking an antimalarial drug and by preventing mosquito bites. Chloroquine is the recommended drug for malaria prevention for persons travelling to the Dominican Republic and is highly efficacious and well tolerated by most travellers. To prevent mosquito bites, travellers should use insect repellent containing up to 50% DEET and wear long-sleeved clothing; if not staying in screened or air-conditioned housing, they should sleep under a net, preferably one treated with insecticide. Rapid intervention is crucial for ill travellers with suspected malaria(3). In nearly all cases in this outbreak, delays in diagnosis and treatment occurred; in certain cases, delays contributed to serious illness.

During July 1999 and March 2000, a previous outbreak in the Dominican Republic occurred among European travelers to Punta Cana, principally in the Bavaro Zone. Factors identified as contributing to that outbreak were: 1) the increased breeding of A. albimanus mosquitoes, the predominant malaria vector in the Dominican Republic, in the wake of Hurricanes Mitch and George and 2) malaria-infected migrant workers. In 1999, approximately 3,000 malaria cases were reported in the Dominican Republic, a 50% increase over the number of cases in 1998(4). During the 1999-2000 outbreak, CDC travel recommendations were temporarily expanded to recommend chloroquine prophylaxis for all areas in La Altagracia Province; this recommendation was rescinded 2 months later after MoH increased surveillance and controlled the outbreak.

In September 2004, Hurricane Jeanne struck the Dominican Republic. The east coast, including Punta Cana and the Bavaro Zone, received heavy rains and flooding, which might have resulted in increased breeding of mosquitoes. In addition, construction in Punta Cana and the Bavaro Zone has brought in many migrant workers from areas where malaria is endemic. The ongoing MoH investigation will attempt to determine whether these factors have contributed to the recent increased transmission. MoH surveillance data indicate that, on average, approximately 1,500 to 2,500 malaria cases are reported annually in the Dominican Republic; in 2004, a total of 2,012 cases had been reported through November.

Effective surveillance systems and rapid communication among surveillance networks are crucial to detecting cases of malaria and intervening in areas that are usually nonmalarious. During this outbreak, rapid communication among surveillance networks in North America, Europe, and the Caribbean led to prompt diagnoses and timely public health interventions to prevent additional cases among residents of and travelers to the Dominican Republic.

Notes

* The first U.S. patient was reported through the Emerging Infections Network, a provider-based sentinel network developed by the Infectious Disease Society of America. The other two U.S. patients were reported through the CDC Malaria Hotline. The Public Health Agency of Canada, the GeoSentinel Network, and the European Network on Imported Infectious Disease Surveillance reported six cases in travellers from Canada and eight cases in travellers from Europe.

References

1. CDC. The yellow book: Health information for international travel, 2003-2004. Atlanta, GA: US Department of Health and Human Services, CDC 2003.

2. CDC. Outbreak notice: Advice for travelers about revised recommendations for malaria prophylaxis in Dominican Republic; updated December 17, 2004. Atlanta, GA: US Department of Health and Human Services, CDC; 2004. Available at http://www.cdc.gov/travel/other/ malaria_dr_2004.htm.

3. Newman RD, Parise ME, Barber AM et al. Malaria-related deaths among U.S. travelers, 1963-2001. Ann Intern Med 2004;141:547-55.

4. Jelinek T, Grobusch M, Harms-Zwingenberger G et al. Falciparum malaria in European tourists to the Dominican Republic. Emerg Infect Dis 2000;6:537-8.

Source: Morbidity and Mortality Weekly Report, Vol 53, Nos 51 and 52, 2004.