Papua New Guinea Malaria Indicator Survey 2022-2023: final report on malaria prevention, infection prevalence, and treatment seeking

Background

Malaria remains a prevalent issue across Papua New Guinea (PNG), with the exception of its highland regions, where the cooler climate at altitudes above 1600 meters inhibits consistent transmission. The National Malaria Strategic Plan (NMSP) for 2021-2025 has set forth an ambitious goal to eliminate malaria from PNG by 2030. To achieve this, the NMSP outlines objectives to decrease the overall malaria burden by 63% and cut malaria-related deaths by 90% by the year 2025.

Since 2004, the PNG National Malaria Control Programme (NMCP), with financial support from The Global Fund to Fight AIDS, Tuberculosis and Malaria, has been actively distributing long-lasting insecticidal nets (LLINs) across the nation. From the latter part of 2011, the program has also expanded the availability of malaria rapid diagnostic tests (mRDTs) and artemisinin-based combination therapies (ACTs) in healthcare facilities. Furthermore, the NMCP has initiated home-based management of malaria in select regions, complemented by behavior change campaigns to bolster the adoption of both preventive measures and treatment solutions.

Methods

As part of the ongoing thorough assessment of the NMCP, the Papua New Guinea Institute of Medical Research (PNGIMR) undertook a nationwide Malaria Indicator Survey (MIS) from September 2022 to August 2023. This survey aimed to evaluate the reach of malaria control measures and the incidence of malaria infections on both national and regional scales. Conducted across 114 villages in all provinces, the survey encompassed 3,029 households, involving a total of 15,435 participants. For the purpose of diagnosing malaria, 12,849 capillary blood samples were collected and analyzed using mRDT and light microscopy techniques.

Results

Across PNG, 58% (95% CI 53.8, 62) of all households owned at least one LLIN, 46.1% (95% CI 41.4, 50.7) of the population had access to a LLIN and 30.7% (95% CI 26.1, 35.8) of household members slept under a LLIN the night before the survey. Among children <5 years, 41.9% (95% CI 37.5, 46.3) slept under a LLIN (67% among those children living in households that owned at least one LLIN). Among pregnant women (15-49 years), 54.4% slept under a LLIN (73.6% among those who lived in a household owning at least one LLIN). LLIN ownership and use were higher in areas below 1600 m altitude than in highland areas. Among women (15-49 years) with a live birth in the two years preceding the survey, 23.5% reported receiving three doses of Sulphadoxine-pyrimethamine (SP) as intermittent preventative treatment (IPTp) during their last pregnancy. Only 4% of household heads reported having received information on malaria in the past three months, mostly from health workers; other sources of information were rarely mentioned.

By mRDT, malaria infection was detected in 6.2% (95% CI 4.8, 8.1) of the population below an altitude of 1600 m, whereas 3.9% (95% CI 1.8, 8.4) was detected in highland areas at and above 1600 m. In children <5 years of age in villages <1600 m altitude, 6.9% (95% CI 5.2, 9.1) were infected with malaria parasites, whereas only two children (1.9%) were found positive among the villages at 1600 m and above. The provinces with the highest prevalence values were Madang (20.1%), Sandaun (19.6%), West New Britain (18.1%), Enga (16.8%), Manus (14.8%), Oro (12.3%), East Sepik (11.4%), and Gulf (11.9%). In this MIS round, it was found that 31 villages showed malaria prevalence rates exceeding 10%. Contrastingly, in the highland villages, malaria prevalence was generally below 3%, with only three exceptions. In the provinces of Gulf, Madang, East Sepik, West Sepik, Manus, New Ireland, and West New Britain, at least three surveyed villages reported adult malaria prevalence rates over 10%, and at least two villages reported rates above 10% in children under 5 years old. Notably, in Oro province, up to 50% of children under 5 were affected.

The target of 1.5% prevalence in children under 5 years of age was not reached on a national or regional level in areas <1600 m altitude where malaria conditions are favorable for transmission. On a provincial level, the target was met in only seven provinces. Prevalence was higher in males than in females and the difference was statistically significant among age groups in the Southern, Islands and Momase regions. Out of 103 surveyed villages, 17 villages reported no malaria infections, and in 63 villages, no infections were detected in children under 5 years old. 44 villages showed a notable higher prevalence of non-Plasmodium falciparum and mixed infections than P.f infections. In Bougainville province all five surveyed villages reported more non-P.f and mixed infections than P.f infections.

A recent fever was reported by 2.5% of all household members and 1.9% had an acute fever on the day of the survey. Anemia was detected in 52.5% of all household members and 3.5% had severe anemia. Anemia was less common in the Highlands Region than in the lowlands and decreased with age. Among children 2-9 years of age, 3% had an enlarged spleen (splenomegaly), specifically in West New Britain contributing up to 78%. However, these were rated 1 on the Hackett grade.

For 54.7% of recent fever cases in the general population and for 47.1% in children <5 years, treatment was sought outside the person’s home. The most common source of treatment were health facilities (52.3% in the general population, 33.3% in children <5 years). The most frequently cited reason for not attending a health facility was a perception that the illness was not serious or that the person already felt better. A diagnostic test was performed in 39.6% of cases in the general population and 26.1% of cases in children <5 years. The most commonly used drugs were antimalarials (46.2%), antipyretics (31.4%), and antibiotics (13.4%). Antimalarial was taken by 9% of cases in children <5 years. The most frequently used antimalarial was the first-line treatment artemether-lumefantrine (45.8%). Use of artemisinin monotherapies, primaquine, SP or chloroquine were much less frequently reported. Use of artemether-lumefantrine to treat test-positive cases was high, with 99% and 100% among the general population and children <5 years, respectively.

Targets and results of key indicators used in the evaluation of the Global Fund support to the PNG NMCP are listed in the table on the following page. Maps depicting LLIN coverage and malaria prevalence by province in five consecutive surveys over the period 2008/09 to 2022/23 are shown on subsequent pages.

Conclusion

After a resurgence of malaria prevalence observed between 2013/14 and 2016/17, a decrease between 2016/17 and 2019/20 across PNG was noticed. However, in this report we identified that there was an increase in malaria prevalence with mRDT. Simultaneously, trends in LLIN coverage show a reduction at national level compared to 2019/20 including communities in low-lying areas. There is a need to evaluate the impact of adapting interventions to different settings in areas below 1600 m altitude and in the Highlands of PNG, where the transmission setting may allow local elimination.