Malaria
Queensland Health Guidelines for Public Health Units
Revision History
| Version | Date | Changes |
|
1.0 |
September 2011 |
Full revision of guideline. |
| 1.1 | July 2015 | Updated external links |
- Disclaimer
- Infectious Agent
- Notification Criteria
- Notification Procedure
- Reporting to NOCS
- Public Health Significance and Occurrence
- Clinical Features
- Reservoir
- Mode of Transmission
- Incubation Period
- Period of Communicability
- Susceptibility and Resistance
- Management
- Preventive Measures
- Summary
- References
Infectious Agent
Human malaria is caused by five different species of the protozoan parasite Plasmodium: Plasmodium falciparum, P. vivax, P. ovale, P. malariae and P. knowlesi. Mixed infections can occur. P. ovale, P. malariae and P. knowlesi infections are relatively uncommon. P. ovale is endemic only in tropical West Africa though is occasionally seen in SE Asia and Oceania; P. knowlesi occurs in rainforests in SE Asia, particularly in Malaysian Borneo. Both P. vivax and P. ovale are capable of relapsing.
Notification Criteria
Laboratory definitive evidence
- Detection and specific identification of malaria parasites by microscopy on blood films with confirmation of species by an approved reference laboratory 1
OR - detection of Plasmodium species by nucleic acid testing.
[1] RBWH laboratory is the only approved reference laboratory in Queensland
Suggestive Criteria
- Detection and specific identification of malaria parasites by microscopy on blood films other than by an approved reference laboratory
OR - a positive result with a rapid immunodiagnostic (immunochromatography or antigen detection EIA) test.
Community Outbreak Criteria
Any local transmission of malaria in Australia should be treated as an outbreak, and requires detailed epidemiological and entomological investigations.
Notification Procedure
Pathology Laboratories
To notify on laboratory confirmation by usual means.
Reporting to NOCS
Report only confirmed cases.
Confirmed case: A confirmed case requires laboratory definitive evidence only.
Public Health Significance and Occurrence
Half of the world's population is at risk of malaria, and an estimated 225 million cases led to nearly 781,000 deaths in 2009.
The disease is endemic in tropical and sub-tropical areas including South and Central America, Asia, the Eastern Mediterranean and the Western Pacific. Particularly high risk areas are found in South America, SE Asia, Sub-Saharan Africa and the Western Pacific nations of Papua New Guinea, Vanuatu, and the Solomon Islands. Malaria is rarely present in highly urbanised areas of cities, except on the outskirts near rural areas.
Several hundred imported cases are recorded in Australia each year. Many of these occur among migrants returning to their native country to visit friends and relatives, when they may have lost their partial immunity. Most cases diagnosed in Australia are imported from Papua New Guinea.
Australia was certified by the WHO as being free of endemic malaria in 1981.
Local transmission in Australia could still potentially occur if imported cases travel to areas where the vector (Anopheles mosquito species) is present. In Queensland this includes areas of north Queensland as far south as Mackay. In 2002 ten locally acquired cases were notified from the Cape York Peninsula.
Local transmission, via importation of infected mosquitoes, could also potentially occur, as happened in far north Queensland in 1996.
Clinical Features
Malaria is an acute febrile illness with an incubation period of 9 days or longer. Thus, a febrile illness developing less than one week after the first possible exposure is not malaria.
The initial symptoms, which may be mild, may not be easy to recognise as being due to malaria. They may cease, only to recur within several days. It is important that the possibility of malaria is considered in all cases of unexplained fever starting at any time between the ninth day of first possible exposure to malaria and up to 12 months (or rarely, later) after the last possible exposure. Any individual who experiences a fever in this interval should immediately seek diagnosis and effective treatment.
Falciparum malaria
The most severe form of malaria is caused by P. falciparum, which can result in death, particularly if diagnosis and treatment are delayed. Variable clinical features include fever, chills and profuse sweating, headache, muscular aching and weakness, vomiting, cough, diarrhoea and abdominal pain. Other symptoms related to organ failure may supervene, such as: acute renal failure, generalised convulsions, circulatory collapse, followed by coma and death.
Pregnant women, young children and elderly travellers are particularly at risk. Malaria in pregnancy increases the risk of maternal death, miscarriage, stillbirth and neonatal death.
Early diagnosis and appropriate treatment can be life saving. P. falciparum malaria may be fatal if treatment is delayed even in mild cases. A blood sample should be examined for malaria parasites. If no parasites are found in the first blood film but symptoms persist, a series of blood samples should be taken and examined at 6-12 hour intervals.
Vivax, ovale, malariae and knowlesi malaria
With the exception of P. knowlesi, malaria caused by other (non-falciparum) species is generally less severe and life-threatening.
P. knowlesi is now recognised as a major cause of severe and fatal malaria in hospitalised patients in Malaysian Borneo. Although it is usually less severe, there have also been several recent reports of P. vivax causing severe disease.
Both P. vivax and P. ovale can persist in the liver as hypnozoites and cause repeated episodes known as relapses over a period of some years. The timing and number of P. vivax relapses is dependent on the geographical location of infection. P. malariae has been known to persist asymptomatically in the blood for up to 40 years and cause symptomatic recurrences following a defined trigger such as a surgical procedure.
Reservoir
Humans are the only important reservoir of human malaria, except P. malariae which is common to man, the African apes and probably some South American monkeys, and P. knowlesi which infects macaque monkeys.
Mode of Transmission
Usually via the bite of an infectious female Anopheles mosquito. These mosquitoes feed mainly between dusk and dawn.
Malaria has also been transmitted in blood transfusions and via contaminated needles and syringes. Congenital transmission occurs rarely.
Incubation Period
Mosquito (extrinsic) incubation period
At temperatures between 25 and 30°C female Anopheles usually become infectious 8-10 days after the ingestion of an infected blood meal (this may extend up to 35 days at temperatures below 20°C).
Human (intrinsic) incubation period
Approximately:
- 9-14 days for P. falciparum
- 12-18 days for P. vivax** and P. ovale
- 18-40 days for P. malariae
- 10-12 days for P. knowlesi
**From 8-10 months with some strains of P. vivax from temperate areas.
Drug suppression of parasites (such as from prophylactic medications) may result in a prolonged incubation period or, in the case of P. vivax and P. ovale, masking of symptoms of the primary infection with the subsequent relapse appearing as the first clinical episode.
Period of Communicability
Humans are infectious to mosquitoes as long as infectious gametocytes remain in the person’s blood. Gametocytes usually appear within 3 days of parasitaemia with P. vivax and P. ovale and after 10 - 14 days with P. falciparum. Untreated or inadequately treated patients may be a source of mosquito infection for several years with P. malariae, up to 5 years with P. vivax and generally not more than 1 year with P. falciparum. Transmission by transfusion (or needle stick injuries) may occur as long as asexual forms remain in the circulating blood. With P. malariae this can continue for over 40 years. Stored blood can remain infectious for at least a month.
Artemisinins have been shown to dramatically reduce gametocyte carriage in both falciparum and vivax malaria.
Infected mosquitoes remain infectious for life.
Susceptibility and Resistance
Susceptibility is universal except in humans with specific traits eg. sickle cell trait, and absence of Duffy factor on erythrocytes. Functional or anatomical asplenia renders an otherwise immune person susceptible. People infected with HIV are at increased risk of symptomatic P. falciparum malaria and its severe manifestations.
Tolerance or partial immunity to clinical disease is present in adults in highly endemic areas where exposure to malaria occurs over many years. This resistance is lost after living away from an endemic area for a period of years.
Management
Cases
Prompt and adequate treatment is a high priority.
Investigation
Inquiry should be made as to overseas travel. The WHO annual publication International Travel and Health lists the risk of malaria infection among countries and within different areas of countries.
Treatment
Complex; see current version of Therapeutic Guidelines – Antibiotic or WHO treatment guidelines.
NB: Where possible, all patients with P. falciparum malaria should be hospitalised for at least 24 hours, to ensure that the medications are tolerated and that the patient is improving. If a patient with P. falciparum malaria is to be managed as an outpatient, the treating doctor should be advised that at the very least, the advice of an infectious disease physician with expertise in managing malaria should be sought.
Infections with P. vivax and P. ovale require treatment for both the blood stages to prevent recrudescence and the liver hypnozoites to prevent relapse. The latter is known as ‘terminal prophylaxis’. The current recommended treatment for terminal prophylaxis is primaquine 30 mg daily for 14 days in individuals who are not G-6PD deficient.
Counselling
The case should be advised of the nature of the infection, its modes of transmission, and the need for mosquito avoidance measures if in a malaria receptive zone.
Contacts
Contact Tracing
Only in cases of locally acquired malaria.
Community outbreaks/epidemics
- Locally acquired malaria in the outer islands of the Torres Strait is not infrequent. The current protocol is not to respond to a single outer island acquired P. vivax case, but to respond to clusters of P. vivax, and to single locally acquired cases of P. falciparum.
- The response to locally acquired malaria in other areas of Queensland will vary according to location and circumstance, but all outbreaks will require further epidemiological (eg. contact tracing) and entomological (eg. Anopheles surveys) investigations.
Preventive Measures
Health education for travellers
It is important to reduce the risk to travellers both for their own protection and to reduce the risk of imported cases to receptive areas in Australia.
Pre-travel advice for travellers to malaria-endemic countries should include the use of appropriate anti-malarial prophylactic medication, strictly in accordance with the prescriber's instructions, and advice on protection from mosquitoes by the use of repellents, protective clothing and mosquito nets if rooms are not screened or air-conditioned.
Travellers must be warned that no prophylactic measures are com¬pletely effective, and a blood test for malaria should be done if they develop fever during travel or within 12 months of return from a malarious area.
Clinician education
Medical practitioners should be encouraged to have a high index of suspicion of malaria when a patient presents with symptoms compatible with malaria following a visit to a malarious area.
Community health education (imported cases)
As Anopheles mosquitoes are present in northern Australia, action may be taken by public health authorities to minimise risk of the spread of malaria in local communities when the disease is diagnosed in a returning overseas traveller and vector populations are significant. These would include mosquito avoidance measures:
- avoid exposure during peak mosquito activity; the Anopheles mosquito is mainly active between sunset and sunrise
- use personal insect repellents
- wear loose-fitting, light-coloured, long-sleeved clothing and long trousers
- avoid strong scents eg. perfumes, aftershaves
- live in mosquito-proof accommodation or use a (treated) mosquito net over the bed, and insect spays and mosquito coils at night.
Disinsection of aircraft, ships etc
The Department of Agriculture and Water Resources/Biosecurity has disinsection requirements for international aircraft arrivals into Australia.
Blood transfusion transmission
Screening procedures are in place. Donation can often still be made by those who have had malaria but only the plasma component of the blood is used.
Needle stick injury
Appropriate infection control precautions – health care workers caring for patients with malaria.
Summary
Prepare a report of any investigation into locally acquired malaria for the Communicable Diseases Branch, Queensland Health, on request.
All locally acquired cases of malaria will be notified to WHO by DoHA.
References
Department of Agriculture and Water Resources/Biosecurity: Guidelines for airline and aircraft operators arriving in Australia
Australian Red Cross Blood Service. Personal communication, Dr R Harley 2/6/2011.
Brasil P, de Pina Costa A, Pedro RS, et al. Unexpectedly long incubation period of Plasmodium vivax malaria, in the absence of chemoprophylaxis, in patients diagnosed outside the transmission area in Brazil. Malaria Journal, 2011; 10:122.
Brookes DL, Ritchie SA, van den Hurk AF, Fielding JR, Loewenthal MR. Plasmodium vivax malaria acquired in far north Queensland. Medical Journal of Australia, 1997; 166: 82.
Centers for Disease Control Atlanta. Malaria home page (and linked pages). Accessed 3/6/2011.
Hanna JN, Ritchie SA, Eisen DP et al. An outbreak of Plasmodium vivax malaria in Far North Queensland. Medical Journal of Australia, 2002; 180: 24-28.
Heymann D (Ed). 2008. Control of Communicable Diseases Manual, 19th edition. American Public Health Association: Washington.
Jenkins GA, Ritchie SA, Hanna JN, Brown GV. Airport malaria in Cairns. Medical Journal of Australia, 1997;166: 307-308.
Maguire JD, Baird JK. The ‘non-falciparum’ malarias: the roles of epidemiology, parasite biology, clinical syndromes, complications and diagnostic rigour in guiding therapeutic strategies. Annals of Tropical Medicine & Parasitology, 2010;104(4): 283–301.
Price RN, Douglas NM, Anstey NM. New developments in Plasmodium vivax malaria: severe disease and the rise of chloroquine resistance. Current Opinion in Infectious Diseases, 2009; 22(5): 430-435
Van den Hurk AF, Ritchie SA, Ingram A, Cooper RD. The first report of Anopheles farauti sensu stricto below the nineteenth parallel at Mackay, Queensland. Medical Journal of Australia, 1998;169: 89-90.
Warrel D, Herbert M Giles, (Ed). Essential Malariology, 4th Edition, 2002. Arnold: London.
WHO. World Malaria report 2010.
WHO. Guidelines for the Treatment of Malaria, 3rd Ed. 2015.
WHO. International travel and health, 2012 Edition.
William T, Menon J, Rajahram G, Chan L, Ma G, Donaldson S, et al. Severe Plasmodium knowlesi malaria in a tertiary care hospital, Sabah, Malaysian Borneo. Emerging Infectious Diseases, 2011; 17(7): 1248-1255.
