Immigrant Health Service

Malaria screening

  • For severe or acute malaria see the statewide Malaria Clinical Practice Guideline

    Background

    Malaria is caused by infection with protozoan parasites of the genus Plasmodium, transmitted by female mosquitos of the genus Anopheles. Four species cause nearly all infections in humans; Pl. falciparum, Pl. vivax, Pl. ovale and Pl. malariae. The microbiological and clinical features vary between species (Table 1). The prevalence of malaria in refugees arriving in Australia was between 5-15%[1-3] and as high as 25% in children arriving from sub-Saharan Africa[3] during the peak wave of Humanitarian entrants from African source countries in the mid 2000s. This has reduced since the introduction of a 'Pre-Departure Medical Screen' (PDMS) in 2005 (known as the Departure Health Check (DHC) since 2012). This is a voluntary health check for refugee  entrants, that occurs 3-7 days prior to departure for Australia. The DHC includes a rapid diagnostic test (RDT) for malaria and treatment if positive[4], however screening is voluntary, and uptake is incomplete.

    2016 ASID refugee health guidelines recommend malaria screening in people travelling from/through endemic areas (Bangladesh, Bhutan, Burma, India, Pakistan, Sri Lanka, African source countries. Note: not Egypt, Middle East, Afghanistan).  In 2017, South Australian colleagues have noted increased presentations of African children with Pl falciparum malaria. 

    • Symptoms of malaria may be non-specific, such as fever, cough, headache, abdominal pain or vomiting.
    • People living in endemic areas develop anti-disease immunity followed by anti-parasite immunity. They may have asymptomatic infection, however are at increased risk of symptomatic infection post migration as immunity wanes.
    • The highest burden of disease occurs in young children (<5 years) prior to the development of adequate immunity. This age group is at increased risk of rapid deterioration and death.
    • Severe malaria is essentially defined as signs of vital organ dysfunction (including hypoglycaemia) or hyperparasitaemia (see below). Australian guidelines use a cut-off of parasitaemia >2%. In general only Pl. falciparum causes severe disease. Severe disease can occur with low peripheral parasite counts.
    • Cerebral malaria is defined as a patient with Pl. falciparum parasitaemia who does not respond to a painful stimulus and has no other identified cause of encephalopathy[5].
    • 98% of symptomatic Pl. falciparum infections present within 3 months post arrival[6].
    • 57% of symptomatic non falciparum infection present within 3 months post arrival and 96% within 12 months[6].
    • Infections can occur with multiple species, which will affect treatment.
    • Hypnozoites (dormant liver forms) only occur in Pl vivax and Pl ovale. These may cause a relapse of disease and require specific treatment.

    Assessment

    • Area of origin, country of transit, time since arrival
    • Previous malaria history
    • Recent screening and/or treatment (including prophylaxis)
    • Current symptoms, including fever pattern (a classic fever paroxysm consists of 3 stages (in order) cold, hot, sweat, lasting 6-10 hours total, usually late in the day)
    • Capacity to access health care in Australia (language skills, time since arrival, independent transport)
    • Others in family (who will also need screening)
    • Splenomegaly is found in 25-40% of symptomatic cases.

    Screening

    • Malaria should be excluded as a priority in all febrile recently arrived refugees from endemic areas (<3 months in Australia) with thick/thin film(s) and a RDT. Malaria may still be the cause of a febrile presentation in refugees settled for a longer period
    • All children aged <5 years from endemic areas, who have been in Australia <3 months should have malaria screening (thick/thin film and rapid diagnostic test) if not already performed, regardless of the reason for presentation
    • All refugees from endemic areas in Australia <3 months should be screened for malaria as part of their outpatient assessment
    • Refugees in Australia for longer than 3 months warrant screening if there is a history of recurrent febrile illnesses or a history of non-falciparum malaria.

    Investigations

    Note: specify country of origin and transit and recent treatment on pathology request forms.

    Thick and thin films

    • If the initial film is negative in patients suspected of having malaria, films should be repeated at 12-24 hour intervals. A fingerprick is adequate. Parasite counts are highest 4 hours after the fever has peaked
    • May not be sensitive if parasite counts are low (<20-50/mcl, possibly <100/mcl)
    • Are never reported as negative, only as no parasites identified
    • Thick films are used for parasite counts, thin films for morphology.

    Rapid diagnostic tests (RDT)

    • Test sensitivity of the local RDT (ICT) is 84-97% (>90% for Pl. falciparum if parasite count >100/mcl) and specificity is 81-100%
    • The locally used RDT gives information on the presence of Plasmodium spp (by detecting parasite LDH) and whether the species is Pl. falciparum (by detecting HRPII).
    • RDTs may remain positive for up to 4 weeks after successful parasite treatment (which is important to consider if people have been treated prior to arrival).

    Other tests in symptomatic patients

    • FBE and film, reticulocyte count
    • VBG, lactate, BSL
    • CUE and LFT
    • Coagulation
    • G6PD screen if quinine/primaquine will be used
    • Screen for pregnancy if indicated

    Management

    • All patients with malaria should be managed in conjunction with an Infectious Diseases Specialist
    • All patients with malaria require assessment in hospital. If there is any suggestion of symptoms (i.e. in a patient who has had outpatient refugee screening) the patient should be recalled to hospital immediately
    • All patients will require a period of observation in hospital while treatment is commenced and/or admission
    • Patients with severe malaria should be managed as for any severely unwell patient, including checking BSL and monitoring for anaemia and for seizure activity. Cardiac monitoring will be required for some medications (i.e. intravenous quinine)
    • Family members should also be screened
    • Malaria is a notifiable disease

    Therapeutic guidelines for malaria are available (see RCH library drug information - intranet access required). Additional considerations include:

    • Artemether-lumefantrine (Riamet) is PBS listed (to weight 5kg/age 3 months) for malaria (therefore health care card rates). Dosing/timing need clear explanation - and picture-based dosing aids may be useful
    • Atovaquone-proguanil (Malarone) is a private script, and outpatient prescribing is usually not feasible because of cost considerations
    • Chloroquine resistant Pl vivax occurs in Timor, Papua New Guinea and the Pacific region; other first line treatment options may be needed
    • G6PD screening must be performed prior to prescribing primaquine.

    Outpatient management

    Outpatient management may be considered if all the following criteria are met [adapted from [7]]

    • Age >5 years.
    • Clinically well.
    • Reviewed by a senior doctor and Infectious Diseases Unit consulted.
    • No clinical or laboratory features of severe malaria.
    • Has resided in endemic area for most of the previous year.
    • Tolerated first dose of oral medication and observed 4-6 hours post.
    • Family has sufficient understanding to ensure compliance and follow-up.
    • Family has sufficient understanding and ability to return to hospital (by ambulance) if child becomes more unwell.
    • Family have a discharge letter stating child has malaria (including type of malaria), with contact numbers and treatment details.
    • No other co-morbidity requiring admission.

    Even if all criteria are met, home-based nursing/Hospital in the Home should be considered for medication and clinical supervision. There are additional considerations in malaria-receptive areas in Northern Australia.

    Follow-up

    Patients should be seen in Infectious Diseases outpatients at 28 days with repeat thick/thin films and RDT, or immediately if symptoms recur.

    Resources

    Severe malaria: WHO definition [5]

    • Prostration
    • Impaired consciousness/coma
    • Respiratory distress (acidotic breathing)
    • Multiple convulsions
    • Circulatory shock
    • Pulmonary oedema or Acute Respiratory Distress Syndrome
    • Abnormal bleeding
    • Jaundice
    • Hemaglobinuria
    • Severe anaemia
    • Hypoglycaemia (< 2.2 mmol/L)
    • Acidosis (HCO3 < 15 mmol/L or base deficit > 10 mmol/L)
    • High lactate (> 5 mmol/L)
    • Hyperparasitaemia (> 4% if non immune child in area unstable endemicity, > 20% in stable endemic areas)

    Table 1: Malaria species

    Species Pl. falciparum Pl. vivax Pl. ovale Pl. malariae
    Predominant spp Sub Saharan Africa, PNG, Haiti South and North Asia, Eastern Europe, Central America, parts South America West Africa, occasional South East Asia, PNG Patchy worldwide, less common outside Africa
      Equal prevalence: Oceania, East Asia, other parts South America      
    Incubation 7 - 14 days 12 - 17 days 15 - 18 days 18 - 40 days  
    Fever Paroxysm May be absent or subtertian Tertian (48 hours) Tertian (48 hours) Quartan (72 hours)
    % Cells affected May be high < 2 - 3% < 2 - 3% < 1%
    Cerebral malaria Yes No No No
    Severe disease Yes Rare reports    
    Resistance reported Yes Yes No No
    Natural history (without treatment) 12 months 3 years 3 years Many years
    Hypnozoite form (can relapse) No Yes Yes No

    References

    Immigrant health clinic resources. Author: Georgie Paxton, reviewed August 2017.