[Table of Contents]

Volume: 26S2 - March 2000

2000 Canadian recommendations for the prevention and treatment of malaria among international travellers
prepared by the
COMMITTEE TO ADVISE ON TROPICAL MEDICINE AND TRAVEL (CATMAT)

1. INTRODUCTION

Malaria is a common and serious infection caused by four species of the genus Plasmodium: Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae. Infection with P. falciparum can be fatal, and infections caused by P. vivax and P. ovale can relapse from latent liver stages. All species of malaria are transmitted by the bite of an infected female Anopheles mosquito. Rarely, transmission may occur by blood transfusion, by shared needle use, or congenitally from mother to fetus. The disease is characterized by FEVER and "flu-like" symptoms such as myalgias, headache, abdominal pain, and malaise. Rigors and chills often occur. The classically described alternate-day fevers or other periodic fevers are often not present. Severe malaria due to P. falciparum may cause seizures, coma, and renal and respiratory failure, and may lead to death. Malaria deaths are frequently the result of delays in the diagnosis and treatment of the infection.

THE SYMPTOMS OF MALARIA ARE NON-SPECIFIC AND DIAGNOSIS IS NOT POSSIBLE WITHOUT A BLOOD FILM.

The widespread resistance of P. falciparum to chloroquine has complicated the prevention and treatment of malaria. Drug-resistant strains of malaria are now common in much of the world. The maps in Figures 1a and 1b indicate the geographic distribution of P. falciparum malaria based on patterns of resistance. These regions require frequent updating as the malaria situation continues to evolve.

Figure 1a Map showing malaria-endemic zones worldwide*

* Visual aid only, see Appendix I, for specific country recommendations.

Figure 1b Enlarged map of China and Thailand showing patterns of malaria resistance*

* Visual aid only, see Appendix I , for specific country recommendations.

As noted in Figure 2 , the number of reported cases of malaria in Canada has risen more than twofold since 1994, to a peak of 1,036 in 1997. However, it is estimated that only 30% to 50% of cases are reported to public health agencies; therefore the true number of imported cases into Canada is likely to be substantially higher. It is of note that Canada's rate of imported malaria continues to be 3 to 10 times the per capita rate of the United States, which may reflect true differences in risk or may be a reporting artefact.

Figure 2 Trends in reported malaria cases, Canada, 1984-1997

The majority of imported P. falciparum cases in recent years were acquired in sub-Saharan Africa, and the majority of P. vivax cases were acquired in the Indian subcontinent. The increased numbers of Canadian malaria cases have been associated with an increased number of malaria deaths: seven from 1997 to 1999. All these deaths were due to P. falciparum. Factors contributing to the deaths were noncompliance with or failure to use appropriate chemoprophylactic agents, delay in diagnosis and treatment, and incorrect therapy once a diagnosis had been reached. Almost all malaria deaths in travellers are due to P. falciparum.

The overall case-fatality rate of imported P. falciparum malaria varies from approximately 1% to 5% and increases to 30% for those over 70 years of age. Progression from asymptomatic infection to severe and complicated malaria can be extremely rapid, with death occurring within 36 to 48 hours. The fatality rate of severe malaria is > 20% even when managed in modern intensive care units. The most important factors that determine patient survival are early diagnosis and appropriate therapy. It should be emphasized that the majority of infections and deaths due to malaria are preventable.

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