Malaria

Queensland Health Guidelines for Public Health Units

Infectious Agent

Malaria is caused by the protozoan parasite species Plasmodium. There are 5 species that infect humans: Plasmodium falciparum, P. vivax, P. ovale, P. malariae and P. knowlesi.

P. ovale, P. malariae and P. knowlesi infections are uncommon compared with P. vivax and P. falciparum infections.1

Case definitions and notification criteria

Report both confirmed and probable cases.

Only confirmed cases are reported to NNDSS.

CONFIRMED CASE

A confirmed case requires laboratory definitive evidence only.

Laboratory definitive evidence

  1. Detection and specific identification of malaria parasites by microscopy on blood films with confirmation of species by an approved reference laboratory#
    OR
  2. detection of Plasmodium species by nucleic acid testing.

#Malaria Reference Laboratory, Pathology Queensland, Herston is the only approved malaria reference laboratory in Queensland.

PROBABLE CASE

A probable case requires laboratory suggestive evidence only.

Laboratory suggestive evidence

  1. Detection and specific identification of malaria parasites by microscopy on blood films other than by an approved reference laboratory
    OR
  2. a positive result with a rapid antigen, immunodiagnostic or immunochromatography test, in the absence of appropriate treatment (see laboratory aspects).

Community Outbreak Criteria

Any local transmission of malaria in Queensland should be treated as an outbreak and requires detailed epidemiological and entomological investigations.

Notification Procedure

Pathology Laboratories

To notify on laboratory confirmation by usual process of data transmission to NoCS.

Clinicians using Point of Care Tests

To notify the local Public Health Unit using the Notifiable Conditions Report Form.

Laboratory Aspects

Blood film microscopy remains the gold standard for diagnosis; serial collection of up to 3 samples every 12–24 hours preceding antimalarial treatment enhances sensitivity. A single negative blood film or negative antigen test does not exclude the diagnosis of malaria. A positive result on a rapid antigen test may be recorded for up to 3 to 4 weeks post treatment.

Laboratory suggestive evidence should be confirmed by blood film microscopy with confirmation of species by an approved reference laboratory or PCR due to limitations of sensitivity and specificity, interspecies variability and the diverse context of malaria testing in Australia.2

Objectives of surveillance

  1. To monitor the epidemiology of malaria in Queensland and inform public health initiatives.
  2. To demonstrate to WHO Australia’s continued malaria-free status.

Public health significance and occurrence

Half of the world’s population is at risk of malaria, and an estimated 247 million cases led to 619,000 deaths in 2021. The World Health Organization (WHO) African Region accounted for about 95% of cases and 96% of deaths globally.3

The disease is endemic in tropical and sub-tropical areas, including South and Central America, Asia, the Eastern Mediterranean, Africa and the Western Pacific.

High-risk areas of the Western Pacific region include Papua New Guinea (PNG), Vanuatu, and the Solomon Islands. PNG accounted for 87% of malaria (all species) cases in this region in 2021, followed by Solomon Islands, Cambodia and the Philippines. The proportion of P. vivax malaria in the Western Pacific region has increased, from about 17% in 2000 to almost one third of all cases in 2021 attributable to a reduction in P. falciparum disease.4

Malaria in Australia is commonly recorded in returned international travellers, including military or refugee arrivals associated with travel from endemic countries.5 Over 100 imported cases are usually recorded in Queensland each year. A reduction in notifications between 2020 and 2022 coincided with international travel restrictions related to COVID-19.6P. falciparum and P. vivax are the most predominant species notified. P. vivax infections are often acquired in the Asia-Pacific region, while P. falciparum is associated with travel to sub-Saharan Africa and PNG.7

Australia was certified by the WHO as being free of endemic malaria in 1981.8 However, re-establishment of malaria and local transmission in Australia could still potentially occur if imported cases travel to locations where suitable mosquito vectors (Anopheles species) are present. Occasionally, limited transmission occurs in the Torres Strait Islands following importation from PNG. Locally acquired malaria has occurred on the outer islands of the Torres Strait including Saibai, Boigu, Erub and Badu Islands. 5,7 The last cases acquired on mainland Australia were during an outbreak in north Queensland in 2002.9 Notably, a case of likely ‘Airport Malaria’ (acquired from an infected mosquito imported in an aircraft) has been reported in north Queensland in 1997.10

Queensland Health is a key stakeholder in surveillance and response procedures for exotic mosquitoes at International First Points of Entry to mitigate the public health risk posed by the importation of infected or suitable malaria vectors.

The WHO annual publication International Travel and Health and Centers for Disease Control and Prevention lists countries and their regions which present risk of malaria.

Clinical Features

The severity and clinical course of malaria is dependent on parasite species and host factors such as age, level of immunity, or use of chemoprophylaxis.1

Malaria is classified as uncomplicated or severe, differentiated by the absence or presence of vital organ dysfunction. Symptoms of uncomplicated malaria include fever, sometimes presenting as malarial paroxysms (cyclical fever, rigors and profuse sweating), and influenza-like symptoms, including headache, myalgia and malaise.1,11

Severe malaria is characterised by one or more of the following: respiratory distress, pulmonary oedema, shock, hypoglycaemia, jaundice, severe anaemia, significant abnormal bleeding, metabolic acidosis, acute kidney injury, hyperparasitaemia, seizures, impaired consciousness or coma (cerebral malaria). Inability to tolerate oral medication, vital organ dysfunction and high parasite counts are associated with a higher risk of death.1,20

In low incidence settings, clinical suspicion of malaria should focus on unexplained fever or history of fever from the ninth day following the first possible exposure (e.g. travel to malaria endemic areas) up to 12 months (or rarely, longer) after the last possible exposure. A febrile illness developing less than one week after the first possible exposure is not indicative of malaria.

Symptoms may be intermittent, or recur in association with relapsing malaria, commonly observed with P. vivax and P. ovale.1,11

Falciparum malaria

Severe malaria is most commonly caused by P. falciparum. Case fatality rates associated with untreated severe malaria (particularly cerebral malaria) reach 100%. Pregnant women, young children and elderly travellers are particularly at risk of severe malaria. Malaria in pregnancy increases the risk of maternal death, miscarriage, stillbirth and neonatal death.

Early diagnosis and appropriate treatment can be lifesaving. P. falciparum malaria may be fatal if treatment is delayed even in mild cases.11,12

Vivax, ovale, malariae and knowlesi malaria

With the exception of P. knowlesi, malaria caused by other (non-falciparum) species is generally uncomplicated and rarely causes severe disease.

P. knowlesi is a zoonosis associated with high parasitaemia and a short 24-hour erythrocytic cycle. Cases of rapid and severe disease (akin to disease caused by P. falciparum) have been acquired on the island of Borneo and Malaysia.1,13,14

Severe P. vivax malaria has been associated with severe anaemia, thrombocytopenia, acute pulmonary oedema, and less commonly cerebral malaria, acute renal failure or shock.  Intense transmission of P. vivax in Indonesia and PNG is associated with significant morbidity and mortality, particularly in infants and children.1,15

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. While uncommon, P. malariae infection 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.12

Reservoir

Humans are the only important reservoir of P. vivax, P. falciparum and P. ovale malaria. P. malariae infects humans, African apes and probably some South American monkeys. Macaque monkeys are the natural host of zoonotic P. knowlesi malaria.12

Mode of Transmission

Malaria is usually transmitted via the bite of an infectious female Anopheles mosquito. These mosquitoes typically feed between dusk and dawn.12

Malaria has also been transmitted in blood transfusions and via contaminated needles and syringes. Vertical transmission occurs rarely.12

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 (which may extend up to 35 days at temperatures below 20°C).16

Human (intrinsic) incubation period

The approximate time from an infective bite to the onset of symptoms in humans (intrinsic incubation period) is:

  • 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 12

** Some P. vivax strains in temperate areas have an incubation period of 6–12 months.17

Incubation periods can be significantly lengthened by partially acquired immunity or use of anti-malarial medications. Chemoprophylaxis may suppress symptoms of P. vivax and P. ovale primary infections with the subsequent relapse appearing as the first clinical episode months or even years after the infective mosquito bite.2

Period of Communicability

Humans are infectious to mosquitoes whilst 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 decades with P. malariae, up to 5 years with P. vivax and generally no more than one year with P. falciparum.12

Transmission by transfusion (or needle stick injuries) can occur from an infected donor and stored blood can remain infectious for at least a month.12

A 3-day course of artemisinin-combination treatment over 2 asexual cycles dramatically reduces gametocyte carriage and onward transmission risk to mosquitoes.1

Infected mosquitoes remain infectious for life.

Susceptibility

Susceptibility is universal except in humans with specific traits (eg. sickle cell trait, and other haemoglobin related disorders or blood cell dyscrasias including G6PD deficiency) that can protect against certain species of malaria. Individuals who are negative for the Duffy blood groups possess red blood cells resistant to P. vivax. 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.12,18

Maternal antibodies provide protection to newborns in the first months of life in areas of high P. falciparum transmission (e.g. Sub Saharan Africa). In areas of moderate to high transmission, partial immunity is generally seen in adults (lower parasitaemia with asymptomatic or less severe disease), with clinical disease (higher parasitaemia that can progress rapidly to severe malaria) confined mainly to young children.  Immunity is modified in pregnancy and diminishes when individuals move out of endemic areas for prolonged periods.1

Management

CASES

Investigation

Ensure specimens are taken or referred for case confirmation in consultation with laboratories and clinician. Seek confirmation of parasite species and the presence of gametocytes.

Determine travel history and identify potential location/s of exposure for probable and confirmed cases with consideration to where the case lived/worked/visited. For current malarious regions refer to International Travel and Health or CDC – Malaria – Travelers – Malaria Information and Prophylaxis, by Country.

Malaria in the absence of overseas travel to an endemic region should raise the suspicion of local transmission and be escalated to environmental health and/or senior medical entomology staff. A detailed history of movements is required during the exposure period.

As Anopheles mosquitoes are present across Australia, public health action may be undertaken to minimise risk of malaria community transmission, particularly in areas with suitable environmental conditions and significant vector populations. Consider the local risk profile and consult with environmental health and/or medical entomology to guide appropriate further investigation and response.

Treatment

Prompt and adequate treatment is a high priority.

The treatment goal for uncomplicated malaria is prompt elimination of all parasites to prevent progression to severe disease and onward vector transmission.1

Choice of therapy should be informed by Plasmodium species, expected resistance and susceptibility depending on geographical area of acquisition, clinical status of the patient, drug safety, and previous use of antimalarials including malaria chemoprophylaxis. Treatment regimens must be completed regardless of partial immunity. P. vivax and P. ovale infections also require treatment for the hypnozoites, to prevent relapsing episodes. See current version of Therapeutic Guidelines – Antibiotic or WHO Guidelines for malaria.

Severe malaria treatment is a medical emergency. Treatment goals include the rapid attainment of therapeutic levels of antimalarial therapy (via parental dosing), management of complications and supportive care.1P. vivax and P. ovale malaria requires ‘radical curative treatment’ of dormant parasites (hypnozoites) with primaquine to prevent relapse. G-6PD deficiency must be excluded before commencing primaquine.1

Discuss with Infectious Diseases Physician regarding the need for hospitalisation.

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.

Locally acquired cases/Community outbreaks

Any locally acquired case of malaria in Queensland requires a public health response appropriate to the location and circumstances. This may include active case finding, surveillance and entomological management. All locally acquired cases should be notified to the Communicable Diseases Branch.

Contact Tracing

Consider active case finding (symptom screening and appropriate laboratory testing) in response to a locally acquired case of malaria. Contacts may include household members, neighbouring households, co-travellers, or work colleagues.

Vector control

Locally transmitted disease response, including vector management, will be undertaken according to local protocols and in coordination with local government. This may include revised routine vector management and enhanced monitoring and control of mosquito populations.

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 a trip risk assessment and the prescriber’s instructions, and advice on prevention of mosquito bites using repellents, protective clothing and mosquito nets if rooms are not screened or air-conditioned.

Travellers must be warned that no prophylactic measures are completely effective, and medical attention should be sought 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 for malaria when a patient presents with symptoms compatible with malaria following a visit to a malarious area or in response to local public health awareness campaigns.

Community health education

Messaging for malaria prevention may include:

  • Avoid mosquitoes when they are most active; the Anopheles mosquito is mainly active between sunset and sunrise.
  • Use an effective insect repellent on exposed skin and reapply within a few hours, following the manufacturer’s instructions. The best mosquito repellents contain the active ingredients Diethyl Toluamide (DEET), Picaridin or Oil of Lemon Eucalyptus (also known as PMD; p-menthane-3,8 diol).
    • Repellents containing less than 10% DEET or picaridin are considered safe for children, however the use of topical repellents is not recommended for infants under 3 months of age. To protect infants less than 3 months of age, physical barriers, such as having the child wear long, loose-fitting clothing or using nets on prams and cots is recommended. Young children should not apply repellents themselves. Repellents should be applied to the hands of a carer first, and then applied evenly to the child’s exposed skin.
  • Cover up with light-coloured, loose-fitting clothing with long sleeves, long trousers, socks and covered footwear when outside.
  • Ensure that intact flyscreens are fitted in homes, tents, caravans or other accommodation.
  • Use treated mosquito nets over the bed when sleeping if accommodation is not air conditioned or if screens on doors and windows are compromised.
  • Use insecticide sprays, vaporising dispensing units (indoors) or mosquito coils (outdoors) at night.

Vaccination

In 2021, the RTS,S/AS01 vaccine was the first malaria vaccine to be recommended by the World Health Organisation for the prevention of P. falciparum malaria in children in regions with moderate to high transmission, and as part of a comprehensive malaria strategy. This vaccine is not available in Australia.1

Disinsection of aircraft, ships etc

The Department of Agriculture, Fisheries and Forestry 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.20

Needle stick injury

Standard infection control precautions apply for health care workers caring for patients with malaria.

References

  1. World Health Organization. WHO Guidelines for malaria [Internet]. 2023 [cited 2023 Aug 11]. Available from: https://www.who.int/publications-detail-redirect/guidelines-for-malaria
  2. Public Health Laboratory Network. Malaria – Laboratory case definition [Internet]. Department of Health and Aged Care; 2018 [cited 2023 Nov 8]. Available from: https://www.health.gov.au/resources/publications/malaria-laboratory-case-definition?language=en
  3. World Health Organization. Malaria [Internet]. 2009 [cited 2023 Aug 11]. Available from: https://www.who.int/news-room/fact-sheets/detail/malaria
  4. World Health Organization. World malaria report 2022 [Internet]. [cited 2023 Aug 11]. Available from: https://www.who.int/teams/global-malaria-programme/reports/world-malaria-report-2022
  5. Knope KE, Doggett SL, Jansen CC, Kurucz N, Feldman R, Lynch7 SE, et al. Arboviral diseases and malaria in Australia, 2014–15: Annual report of the National Arbovirus and Malaria Advisory Committee. Commun Dis Intell [Internet]. 2019 Apr 15 [cited 2023 Aug 11];43. Available from: http://www.health.gov.au/internet/main/publishing.nsf/Content/75F30C0D2C126CAECA2583940015EDE3/$File/arboviral_diseases_and_malaria_in_Australia-_NTAC_2014%E2%80%9315_annual_report.pdf
  6. Queensland Health. Notifiable Conditions Annual Reporting. 2023 [cited 2023 Aug 11]. Notifiable conditions annual reporting. Available from: https://www.health.qld.gov.au/clinical-practice/guidelines-procedures/diseases-infection/surveillance/reports/notifiable/annual
  7. Queensland Health. Mosquito-borne diseases in Queensland 1 July 2012- 30 June 2017 [Internet]. 2018. Available from: https://www.health.qld.gov.au/__data/assets/pdf_file/0020/712253/mbd-report-annual.pdf
  8. World Health Organization. Synopsis of the World Malaria Situation in 1981. Wkly Epidemiol Rec Relevé Épidémiologique Hebd. 1983;58(25):189–92.
  9. Hanna JN, Ritchie SA, Brookes DL, Montgomery BL, Eisen DP, Cooper RD. An outbreak of Plasmodium vivax malaria in Far North Queensland, 2002. Med J Aust [Internet]. 2004 Jan 5 [cited 2023 Aug 11];180(1). Available from: https://www.mja.com.au/journal/2004/180/1/outbreak-plasmodium-vivax-malaria-far-north-queensland-2002
  10. Jenkin GA, Brown GV, Ritchie SA, Hanna JN. Airport malaria in Cairns. Med J Aust. 1997;166(6):307–8.
  11. Tan K, Abanyie F. Malaria. 2023 [cited 2023 Aug 11]. CDC Yellow Book 2024. Available from: https://wwwnc.cdc.gov/travel/yellowbook/2024/infections-diseases/malaria
  12. Drakeley C, Targett G. Malaria. In: Control of Communicable Diseases Manual [Internet]. American Public Health Association; 2015 [cited 2023 Aug 11]. (Control of Communicable Diseases Manual). Available from: https://ccdm.aphapublications.org/doi/10.2105/CCDM.2745.097
  13. William T, Menon J, Rajahram G, Chan L, Ma G, Donaldson S, et al. Severe Plasmodium knowlesi malaria in a tertiary care hospital, Sabah, Malaysia. Emerg Infect Dis. 2011 Jul;17(7):1248–55.
  14. Barber BE, Grigg MJ, Cooper DJ, van Schalkwyk DA, William T, Rajahram GS, et al. Clinical management of Plasmodium knowlesi malaria. Adv Parasitol. 2021;113:45–76.
  15. Price RN, Douglas NM, Anstey NM. New developments in Plasmodium vivax malaria: severe disease and the rise of chloroquine resistance. Curr Opin Infect Dis. 2009 Oct;22(5):430–5.
  16. Queensland Health. Guideline for the management of community outbreaks and epidemics of malaria in the Torres Strait [Internet]. 2011 [cited 2023 Oct 7]. Available from: https://www.health.qld.gov.au/__data/assets/pdf_file/0022/444325/malaria-gl.pdf
  17. Brasil P, de Pina Costa A, Pedro RS, da Silveira Bressan C, da Silva S, Tauil PL, et al. Unexpectedly long incubation period of Plasmodium vivax malaria, in the absence of chemoprophylaxis, in patients diagnosed outside the transmission area in Brazil. Malar J. 2011 May 14;10(1):122.
  18. CDC - Parasites - Malaria [Internet]. 2023 [cited 2023 Aug 11]. Available from: https://www.cdc.gov/parasites/malaria/index.html
  19. Andrea K. Boggild and David O. Freedman. Infections in Returning Travelers. In: John E. Bennett MD, Raphael Dolin MD and Martin J. Blaser MD, editor. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases-[Internet]. 9th ed. Elsevier, Inc; 2020 [cited 2023 Sep 1]. Available from: https://www.clinicalkey.com.au/#!/browse/book/3-s2.0-C2016100010X
  20. Dr R Harley. Australian Red Cross Blood Service. 2011.

Version History

VersionDateChanges
1.0 September 2011Full revision of guideline
1.1July 2015Update external links
2.0September 2023Full revision and updated case definition (addition of probable case)

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Last updated: 27 July 2016