August 16, 2023
NCCID Disease Debriefs provide Canadian public health practitioners and clinicians with up-to-date reviews of essential information on prominent infectious diseases for Canadian public health practice. While not a formal literature review, information is gathered from key sources including the Public Health Agency of Canada (PHAC), the USA Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO) and peer-reviewed literature.
Questions, comments, and suggestions regarding this disease brief are most welcome and can be sent to nccid@manitoba.ca
What are Disease Debriefs? To find out more about how information is collected, see our page dedicated to the Disease Debriefs.
Questions Addressed in this debrief:
- What are important characteristics of malaria?
- What is happening with current outbreaks of malaria?
- What is the current risk for Canadians from malaria?
- What measures should be taken for a suspected malaria case or contact?
What are important characteristics of the malaria?
Cause:
Malaria is a parasitic infection spread to humans by female Anopheles mosquitoes. The single-celled parasites are in the genus Plasmodium. Typically, four kinds of malarial parasites infect humans, Plasmodium falciparum, P. vivax, P. ovale, and P. malariae. P. Knowlesi, a type of malaria that naturally infects macaques in Southeast Asia, may also infect humans, causing malaria that is transmitted from animal to human.
In some rare cases transmission can also occur from human to human via mother-to-fetus transmission, blood transfusions, and the sharing of needles.
CDC: Malaria – Frequently asked questions
Signs Symptoms and Severity:
Typical symptoms of malaria are similar to those of a flu including fever, diarrhea, headache, sweat or chills, nausea and vomiting, muscle, and stomach pain. In cases of complicated malaria, symptoms may include severe anemia, hemoglobinuria, acute respiratory distress syndrome (ARDS), an inflammatory reaction in the lungs that inhibits oxygen exchange. The ARDS may occur even after the parasite counts have decreased in response to treatment, abnormalities in blood coagulation, low blood pressure caused by cardiovascular collapse, acute kidney injury, hyperparasitemia, where more than 5% of the red blood cells are infected by malaria parasites, metabolic acidosis (excessive acidity in the blood and tissue fluids), often in association with hypoglycemia is also reported in severe malarial symptoms. Severe malaria is a medical emergency that needs to be treated aggressively.
In most cases, the incubation period runs between 7– 30 days. However, shorter periods are observed most frequently with P. falciparum and the longer ones with P. malariae. With P. vivax and P. ovale, relapse infection can occur. Some parasites can stay dormant in the liver from several months up to about four years after a bite from an infected mosquito.
Some population groups are at high risk of developing severe malaria including children under the age of five, pregnant women and patients with HIV/AIDS, non-immune migrants, mobile populations and travellers. Children with severe malaria develop symptoms such as severe anemia, respiratory distress in relation to metabolic acidosis or cerebral malaria.
CDC: Malaria – Frequently asked questions
Diagnosis:
The malarial parasite can be visualized on both thick and thin blood smear stained with Giemsa, Wright.
Severe malaria patients may have either one or both conditions;
- Plasmodium falciparum asexual parasitemia and no other obvious cause of symptoms.
- the presence of 1 or more of the clinical or laboratory features in the above table.
The Plasmodium falciparum is the type of malaria that is most likely to cause severe infections and is responsible for the most malarial deaths globally.
Table 1: Criteria for severe Falciparum malaria
| Clinical manifestation | Laboratory results |
| Prostration or impaired consciousness | Severe anemia in children less than 12 years of age: Hb less than or equal to 5 g/dl or hematocrit of less than or equal to 15% In adults: Hb less than 7 g/dL and hematocrit less than 20% |
| Respiratory distress | Hypoglycemia (blood glucose less than 2.2 mmol/L) |
| Multiple convulsions | Acidosis (arterial pH less than 7.25 or bicarbonate less than 15 mmol/L) |
| Circulatory collapse | Renal impairment (creatinine greater than 265 umol/L) |
| Pulmonary edema (radiological) | Hyperlactatemia |
| Abnormal bleeding | Hyperparasitemia (greater than 10%) |
| Jaundice | Total bilirubin greater than 50 µmol/L |
| Hemoglobinuria | Macroscopic |
PHAC: For health professionals: Malaria
CDC: Malaria: Laboratory Diagnosis
CDC: Frequently asked questions
PHAC: Canadian Recommendations for the prevention and treatment of malaria
Treatment
Treatment varies according to the species of malarial parasite and the severity or complexity of malaria. Parenteral quinine is preferable for those who do not have severe malaria and cannot tolerate oral medication. Otherwise, the use of parenteral artesunate is preferable to parenteral quinine:
- For severe malaria
- When there is a quinine
- failure
- intolerance
- contraindication
In case of sudden deterioration, patients should be assessed and treated immediately and suspected of hypoglycemia or other complications of severe malaria (severe malaria can trigger hypoglycemia, which can be deteriorated by quinine therapy that stimulate insulin release).
Patients with severe or complicated malaria infection (usually due to plasmodium falciparum) require:
- immediate hospitalization
- urgent, intensive medical management, ideally in an intensive care unit
Recommended initial treatment in an observation unit to:
- ensure that treatment can be tolerated
- confirm decreasing parasitemia with treatment
There are two classes of drugs that are effective for the parenteral treatment of severe malaria:
- cinchona alkaloids:
- quinine
- quinidine
- artemesinin derivatives:
- artemotil
- artesunate
- artemether
A diagnosis of severe malaria requires parenteral therapy. This therapy requires one of the following parenteral drugs within an hour of the diagnosis:
- quinine
- quinidine
- artesunate
PHAC: For health professionals: Malaria: Treatment
PHAC: Canadian Recommendations for the prevention and treatment of malaria
Epidemiology:
The epidemiology of malaria is complex and varied within small geographic areas.
Major epidemiologic determinants that have been identified include:
- higher temperatures (temperatures higher than 20°C (68°F), Plasmodium falciparum (which causes severe malaria) can complete its growth cycle in the Anopheles mosquito, and thus malaria can be transmitted).
- level of rainfall
- distribution of mosquito breeding sites
- immunologic and genetic makeup of the population
- species of parasite and mosquito in the community at risk
- use of antimalarial drugs and application of other control measures
Prevention:
Currently, no vaccine is available in the market to prevent malaria. Individuals need to take precautions to prevent being infected.
Travellers are advised to visit a travel clinic or consult a health care provider six weeks before travel to discuss best anti-malarial for prevention. Antimalarials must be taken before, during and after a trip to prevent the disease. People are advised also to avoid mosquito bites, especially during sun rise and sun set.
PHAC: Canadian Recommendations for the prevention and treatment of malaria
Reporting and Surveillance
Malaria is a nationally notifiable disease in all provinces and territories in Canada. Malaria cases are reported to provincial or territorial government departments to the federal government if they meet the national case definition criteria.
Only confirmed cases should be notified and reported.
Case classification:
Confirmed case – Presence of Plasmodium sp. in thick or thin blood smear/film.
Probable case – Detection of Plasmodium sp. antigen in a clinical smear.
Probable case definitions are provided as guidelines to assist with case finding and public health management and are not for national notification purposes.
Malaria cases are subdivided into the following categories:
- Induced: a confirmed case of malaria acquired through a blood transfusion from a donor in whom the parasite has been confirmed.
- Autochthonous: a confirmed case of malaria acquired by mosquito transmission within Canada.
- Imported: a confirmed case of malaria acquired outside Canada.
- Congenital, confirmed: a confirmed case of malaria in an infant < 3 months old who has not left Canada since birth, with confirmation of the presence of the parasite in the mother.
- Congenital, probable: a confirmed case of malaria in an infant < 3 months old who has not left Canada since birth, but without demonstration of the presence of the parasite in the mother.
Special Note:
- A case is counted if it is the individual’s first attack of malaria in Canada, regardless of whether or not the person has experienced previous attacks of malaria outside the country.
- A subsequent attack in the same person caused by a different Plasmodium species is counted as an additional case.
- A repeat attack by the same species is not counted as a new case unless the person has traveled to a malaria-endemic area since the previous attack.
PHAC: For health professionals: Malaria
PHAC: National case definition: Malaria
What is happening with current outbreaks of malaria?
There were about 247 million cases on malaria reported in 2021 and 245 million in 2020. The estimated number of malaria deaths stood at 619 000 in 2021 compared to 625 000 in 2020.
Annually in Canada an average of 488 malaria cases are reported.
As of July 07, 2023, there have been seven locally acquired cases of malaria reported in two different states in the USA: six in the state of Florida and one in the state of Texas.
What are the current risks for Canadians?
All travelers are at risk where malaria exists. These include:
Asia – South Asia, Southeast Asia, some parts of East Asia
Africa – most of sub-Saharan Africa, limited areas in North Africa
Caribbean – Haiti, parts of Mexico, parts of the Dominican Republic
Middle East – limited areas
Eastern Europe – limited areas
South and Central America
South Pacific and Oceania region – some small islands, including Papua New Guinea
The WHO African region carries a disproportionately high burden of malaria as compared to other regions globally.
Hence, visiting high risk regions such as West Africa and Oceania (highest risk), other parts of Africa, South Asia, and South America (moderate risk), Caribbean, Central America, Mexico, and other parts of South America and of Asia (lower risk) increase the chances of getting infected. Also, factors such as period of stay, location of stay (rural vs remote), seasons of the year (summer vs rainy season), outdoor exposure especially during sundown and sun rise, exposure to areas where high death rates are reported due to malaria are some factors to consider.
Vulnerable population:
Pregnant women, young children under the age of five and immune compromised patient are at high risk of malarial infection.
What measures should be taken for a suspected Malaria disease case or contact?
If malaria is suspected, laboratory testing (microscopic examination of blood smears, polymerase
chain reaction or rapid diagnostic tests) should be done on one or more occasions to verify the
diagnosis. in most cases, the lab test can identify the species within 1 to 2 hours of receiving a blood specimen. However, in very few cases, when the level of parasitemia is low, an initial smear may be falsely negative. Thus, one or two additional smears are required every 12 to 24 hours to confirm or exclude the diagnosis. It is important to obtain repeat smears at regular intervals rather than potentially delay the diagnosis by attempting to time sample-taking with the fever cycle.
Suspected malaria should be considered a medical emergency, particularly if there is evidence of organ dysfunction, as well as altered mental state. Also, malaria should be suspected in any febrile person with a history of travel to a malaria-endemic area and a history of or finding of fever.
Blood should be examined immediately for malaria if it is suspected. If expertise in reading malaria smears is not available, diagnosis should involve the local use of an RDT and then the rapid transfer of a blood sample to a reference centre. The result of the RDT or initial blood smear should be available within 2 hours of blood taking.
PHAC: Canadian Recommendations for the prevention and treatment of malaria