Individuals with suspect or confirmed cases must be reported to the Thunder Bay District Health Unit by the next working day by fax, phone or mail.
- Fax: (807) 625-4822
- Phone: 625-8318 or toll-free at 1-888-294—6630, ext. 8318
- Mail: 999 Balmoral Street, Thunder Bay, ON P7B 6E7
Malaria is caused by protozoan parasites of the genus Plasmodium (P). Four species of Plasmodium routinely infect humans: P. vivax, P. ovale, P. malariae, and P. falciparum. Humans also occasionally become infected with Plasmodium species that normally infect animals, such as P. knowlesi.
The classic symptoms of malaria are high fever with chills, rigor, sweats and headache, which may be paroxysmal. Symptoms can occur in cycles of 48-72 hours if not treated, though cyclical symptoms are uncommon. Symptoms may also include cough, diarrhea, respiratory distress, vomiting and muscle pain. Complications may include coma, renal failure, liver failure, and other system failure resulting in death.
The most serious malarial infection, falciparum malaria, usually presents a highly variable clinical picture including one or more of the following: fever, chills, sweats, anorexia, nausea, lassitude, headache, muscle and joint pain, cough and diarrhea. Anemia, thrombocytopenia and/or splenomegaly often develop after some days.
The primary attack lasts for weeks or months; relapses may also occur. Infection may remain for years or lifelong without any recurrence of febrile episodes.
Modes of transmission:
The disease is transmitted to humans through the bite of an infected female Anopheles mosquito.
The disease may also be transmitted through injection or transfusion of infected blood; congenital transmission rarely occurs.
The median time between an infective bite and the appearance of clinical symptoms for P. falciparum is 9 – 14 days; 12 – 18 days for P. vivax and P. ovale and 18 – 40 days for P. malariae.
Delayed primary attacks by P. vivax or P. ovale may occur 6 - 12 months after exposure.
Period of Communicability:
Mosquitoes may acquire the parasites from infected humans as long as the gametocytes are present in the blood; this varies with parasite species and with response to therapy. Untreated or insufficiently treated patients may be a source of mosquito infection for several years in P. malariae, up to 5 years in P. vivax, and generally not more than 1 year in P. falciparum malaria.
Transfusion transmission may occur as long as asexual forms remain in the circulating blood (with P. malariae up to 40 years or longer).
Stored blood can remain infective for at least one month.
Susceptibility is universal. Those most at risk are persons travelling to malaria-endemic areas who are not protected by chemoprophylaxis.
Diagnosis & Laboratory Testing
Microscopy is usually adequate but not when the parasite is scarce in early infections or after treatment. Attention should be given to the sensitivity results. Approved tests include:
• Appropriate staining methodology for Plasmodium in blood smears
• Tests for Plasmodium specific antigen
• Nucleic acid amplification test (NAAT) for Plasmodium sp.
Treatment & Case Management
To prevent malaria, refer travelers to a travel clinic for up to date information about malaria endemic areas and malaria prophylaxis. Advise to use protective clothing, bed nets and repellents with DEET in high risk areas. Advise to seek early diagnosis and treatment for a febrile illness during or following travel to endemic areas.
Treatment is under the direction of the attending health care provider. Provide education about the illness and how to prevent the spread.
Genotyping is available for P. falciparum infections to determine resistance to anti-malarial drugs.
- Ministry of Health and Long Term Care, Infectious Diseases Protocol, 2016. Appendix A (2014) and Appendix B (2014)
- Public Health Ontario, Monthly Infectious Diseases Surveillance Report, Malaria, April 2014.
1. Heymann, D.L. Control of Communicable Disease Manual (20th Ed.). Washington, American Public Health Association, 2015, pg. 372-388 (Includes in-depth information on malaria such as prevention for pregnant travellers, parents of young children, chemoprophylaxis, and specific treatment for all forms of malaria).