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  • PMSA Editorial Team 2020

Malaria


Malaria is known to be caused by infection of human red blood cells with a parasite transmitted to people through the bites of infected female Anopheles mosquitoes. The parasite uses two host organisms in its complex life cycle: a mosquito vector and a vertebrate host [9]. In the first meal, the vector acquires the parasite from an infective host. By the second meal, the vector transmits the parasite through her saliva into the blood of another vertebrate host [9]. Once in the bloodstream, the parasite attacks red blood cells, giving rise to the disease we now know as malaria. When red blood cells in the brain are involved, the infection results in the often-fatal condition of cerebral malaria [9].


Of the many known species of Plasmodium, only four infect humans routinely: P. falciparum, P. vivax, P. ovale, and P. malariae [13]. All four species of Plasmodium have been found in the endemic countries of the Pacific [8]. Data from the Global Health Atlas of the World Health Organization indicate that over the past 5 years for which figures are available (1999–2003) P. falciparum infection has hovered at around 80% of reported cases in Papua New Guinea, 70% in Solomon Islands and 50% in Vanuatu[9].


Environment considerations include [4]:

  • Climate (temperature, rainfall, humidity),

  • Availability of mosquito breeding and resting sites,

  • The existence of vector competitors

Malaria thrives in hot climates because the Plasmodium parasite matures quickly in the mosquitoes that carry it, making transmission more effective. The disease is predominantly found in tropical and subtropical regions[9]. Moreover, economic development results in land use changes that may exacerbate mosquito-borne diseases by creating new habitats for mosquitoes [17]. In addition, the world’s climate system is warming, as evidenced by increases in average air and ocean temperatures, widespread melting of snow and ice, and rising average sea level [15]. Global warming may have long-term effects on the transmission of malaria by altering variables such as temperature, humidity, rainfall and seasonality [12][16][20], allowing mosquitoes to ‘colonize higher altitudes and farther latitudes’ [11]. In Papua New Guinea, global warming may in time reduce the size of the cooler, malaria-free zones in the highlands [7].


Malaria is currently endemic to 109 countries [24]. Human efforts to control malaria have restricted its distribution over time. Between 1900 and 2002, the geographic area of human malaria risk was reduced by about half, from 53% to 27% of the Earth’s land surface [14]. However, the regional data does not give a good picture of malaria risk in the Pacific as the combined population of these six countries alone (1,698 million in 2007), as the population of Papua New Guinea, Solomon Islands and Vanuatu (7 million in 2007) was relatively invisible [9]. In 2008, a Project was released on the first contemporary data and maps of the geographical limits of P. falciparum malaria risk [9]. The study shows that 2.37 billion people (about 35% of the world’s population) live in areas at some risk of P. falciparum transmission, including 4.11 million in Papua New Guinea, 0.43 million in Solomon Islands, and 0.22 million in Vanuatu [9]. The geographic distribution of malaria in the Pacific is closely allied to the distribution of the Anopheles vector that transmits the parasite [9]. The pioneering work of Buxton and Hopkins (1927) led to the development of the ‘Buxton line’, which passes through southern Vanuatu and forms the eastern limit of the Anopheles mosquito in the Pacific [9]. While malaria in the Pacific is seen most frequently in countries west of the Buxton line, cases have been reported in other Pacific Island countries, such as Fiji and Tonga [10][19].


These cases of ‘imported malaria’ are of two types [9]:

  • Individuals with histories of malarial infection in endemic countries, who then suffer relapses outside those countries; and

  • Travelers who are infected shortly before leaving an endemic area and manifest a primary infection after arrival at their destination (poses difficulties for the diagnosis of malaria because the disease commonly presents in an early non-specific form [10].


For individuals who have been infected with the malaria parasite shortly before travelling, there can be problems in diagnosing the condition after arrival since early symptoms of malaria are often non-specific. Physicians in non-endemic countries may not be attuned to the possibility of this diagnosis [9]


Furthermore, in the early 1990s; a temporary but significant rise in incidence of malaria occurred in Solomon Islands and Vanuatu from 1999 to 2003; a relatively low and stable incidence in Papua New Guinea in recent years; and an incidence in Solomon Islands that is still much higher than that of its neighbour countries [9]. In the early 1990s Solomon Islands had one of the world’s worst malaria rates [9]. Even so, in 2003, Solomon Islands ranked tenth in the world for malaria incidence, but ranked first in the world outside Africa [23].


In addition, the average rate of deaths per 100,000 population for [9]:

  • Papua New Guinea was 10.6 deaths, with no discernible time trend (may reflect the higher proportion of P. falciparum malaria in that country compared with Solomon Islands).

  • The average rate for Solomon Islands was 8.4 deaths, with a sustained increase in the mortality rate, peaking at 14.9 in 2003 (most probably due to the breakdown in health service delivery during a period of civil unrest), followed by a pronounced decline.


In 2017, Solomon islands had 52,483 confirmed cases of malaria and 27 deaths reported [3]. Vanuatu had 982 cases of malaria and 0 deaths in 2014 while PNG had a staggering 1.1 million presumed and confirmed cases of malaria and 307 deaths in 2013. In 2015, three countries accounted for 91% of just over 355,000 confirmed cases reported: PNG (79%), Cambodia (7%) and Solomons Islands (5%) [1][2][3]


It is also important to note that Malaria is a major cause of anaemia, low birth weight, premature birth and infant mortality [9]. In 2002, malaria ranked as the 9th leading cause of death globally, accounting for 2.2% (1.27 million) of the 57 million deaths that year [9]. Mortality from malaria is concentrated among children under 5 years of age. Malaria also suppresses links between malarious and non-malarious regions, which may curb foreign investment and tourism in endemic areas [21]. Endemic countries may also find it difficult to promote tourism because international travellers find malarious destinations less attractive, which has been the experience in Solomon Islands [9].


Diagnosis

  • The clinically, prompt and accurate diagnosis is vital in selecting an appropriate drug intervention for a disease that can be rapidly fatal [9].

  • WHO treatment guidelines suggest that malaria diagnosis should be based on both:

  1. Clinical criteria (signs and symptoms) and

  2. Parasitological criteria (detection of parasites in the blood) [22].

  • Diagnosis on the basis of clinical criteria alone can lead to error because the first symptoms of malaria are non-specific and similar to the symptoms of many minor viral illnesses: headache, muscle ache, fatigue, fever and chills [9].

  • Microscopic examination of blood samples is the most reliable method of diagnosis but it is not available in many developing countries [19]. In Papua New Guinea, for example, there were 84,051 laboratory-confirmed malaria cases in 2006, but 20 times as many clinically diagnosed cases: 1,676,681 [25].

  • While the use of rapid diagnostic tests (RDTs) may offer a partial solution, these tests suffer from their own drawbacks of higher cost, variable sensitivity and specificity, and vulnerability to heat and humidity [22].

Prevention and Treatment


1. All mosquitoes share a pattern of biological development that is linked to aquatic breeding sites. The way was clear to introduce environmental controls over mosquito breeding sites by clearing swamps and improving drainage [9]. The Malaria (Control) Act requires every person occupying cultivated land to take all necessary measures to prevent any coconut shell capable of holding rainwater being used as a breeding place for mosquitoes [9].


2. The use of dichloro-diphenyl-trichloroethane (DDT) [9].

  • The pesticide was cheap to produce and had valuable residual properties: microscopic amounts sprayed in dwellings could kill mosquitoes for months afterwards [9].

  • Seizing this new opportunity, WHO implemented the Global Malaria Eradication Program from 1955 to 1969.

  • Malaria was virtually wiped out in many parts of Melanesia, where spraying with DDT continued practices that had commenced in some places during World War II [5][8]

  • In 2004– 2006, residual spraying covered over 46,000 households in Solomon Islands and 2,000 households in Papua New Guinea, but none at all in Vanuatu [24].


3. Drug prophylaxis and treatment

  • A synthetic medicine, chloroquine that has similar properties to quinine, and was inexpensive, safe and long-lasting [9].

  • However, genetic mutations gave some parasites some resistance to the drug [9].

  • The limitations on the effectiveness of chloroquine have encouraged the development of other antimalarial drugs (such as primaquine) and these are used widely throughout Melanesia.

  • Prophylaxis is also available through use of tetracycline antibiotics, which are effective in killing parasites in the blood but are unsuitable for long-term use [9].

  • Artemisinin-based Combination Therapy (ACT) is now the first line of treatment for P. falciparum malaria (WHO 2006) although its high cost often necessitates use of ineffective drugs in the poorest countries [23].


4. Insecticide-treated nets

  • The idea of using bed netting to protect people from the night-feeding habits of many species of mosquito is not new [9]

  • The impregnation of nets with long-lasting insecticide that survives multiple washes gives an even higher level of protection [25].

  • The use of insecticide-treated nets (ITNs) is effective in reducing the disease burden of malaria

5. A malaria vaccine

  • Childhood immunization against communicable diseases has been one of the greatest public health successes of the past century, eradicating some medical conditions such as smallpox and polio, and effectively controlling many others [9a].

  • That vaccine reduced malaria infection in children aged 5–17 months by 53%. It is too early to be confident of success but, if the goal is achieved, a vaccine will give Pacific populations cost-effective and long-lasting protection against malaria [9].


Over 50 years ago, at the start of WHO’s Global Malaria Eradication Program, it was claimed that one can ‘be confident that malaria is well on its way towards oblivion' [9]. However, malaria is no longer in retreat. With rapidly growing populations in areas of high endemicity, the number of malaria cases are estimated to increase [9].The combined population of Papua New Guinea, Solomon Islands and Vanuatu is expected to grow from 7.23 million in 2008 to 11.32 million by 2030: an increase of over 4 million people (56%) in 22 years [9]. Steps have been taken towards developing a malaria vaccine, and there has been ‘heretofore unheard of political, strategic, and financial support for malaria scientific studies and control actions’ [9].



  1. Asia Pacific Malaria Elimination Network (APMEN). Malaria in Papua New Guinea. 2020

  2. Asia Pacific Malaria Elimination Network (APMEN). Malaria in Vanuatu. 2020

  3. Asia Pacific Malaria Elimination Network (APMEN). Malaria in Solomon Islands. 2020

  4. Ault, S. Effect of malaria on demographic patterns, social structure, and human behavior. In M. Service (Ed.), Demography and vector-borne diseases (pp. 271–282). Boca Raton: CRC Press. 1989

  5. Avery, J. A review of the malaria eradication program in the British Solomon Islands 1970–1972. Papua New Guinea Medical Journal. 1974. 17, 50–60.

  6. Baselala, E. Malaria campaign begins in Solomons, Vanuatu. Islands Business. June. http://www.islandsbusiness.com. Accessed 12 March 2009. 2007.

  7. Barnett, J. Food security and climate change in the South Pacific. Pacific Ecologist, Winter,32–36. 2007

  8. Black, R. Malaria in the South-West Pacific. Noumea: South Pacific Commission.1955

  9. Brian Opeskin. J Pop Research. Malaria in Pacific populations: seen but not heard. 2019. 9a. Centers for Disease Control and Prevention. (1999). Achievements in public health, 1900–1999

  10. Changes in the public health system. Morbidity and Mortality Weekly Report, 48, 1141–1147.

  11. Finau, S. Malaria in Tonga: An imported case. New Zealand Medical Journal, 90, 465–466. 1979

  12. Finkel, M. Bedlam in the blood: Malaria. National Geographic, 212(1), 32–67. 2007

  13. Gage, K., Burkot, T., Eisen, R., et al. Climate and vectorborne diseases. American Journal of Preventive Medicine, 35, 436–450. 2008

  14. Garnham, P. Malaria parasites and other haemosporidia. Oxford: Blackwell. 1966

  15. Hay, S., Guerra, C., Tatem, A., et al. The global distribution and population at risk of malaria: Past, present and future. Lancet Infectious Diseases, 4, 327–336. 2004

  16. Intergovernmental Panel on Climate Change. Fourth assessment report. Climate change 2007: Synthesis report. www.ipcc.ch/ipccreports/ar4-syr.htm. Accessed 12 March 2009. 2007

  17. McMichael, A., Woodruff, R., & Hales, S. Climate change and human health: Present and future risks. Lancet, 367, 859–869. 2006

  18. Norris, D. Mosquito-borne diseases as a consequence of land use change. EcoHealth, 1, 19–24. 2004

  19. Price, R., Tjitra, E., Guerra, C., et al. Vivax malaria: Neglected but not benign. American Journal of Tropical Medicine and Hygiene, 77(Suppl. 6), 79–87. 2007

  20. Ram, P., & Malani, W. Imported malaria in Fiji. Fiji Medical Journal, 6, 24–26. 1978

  21. Reiter, P. Climate change and mosquito-borne disease. Environmental Health Perspectives, 109(Suppl. 1), 141–161. 2001

  22. Sachs, J., & Malaney, P. The economic and social burden of malaria. Nature, 415, 680–685. 2002

  23. World Health Organization (WHO). Guidelines for the treatment of malaria. Geneva: WHO. 2006

  24. World Health Organization (WHO). World Malaria Report 2005. Geneva: WHO. 2005

  25. World Health Organization (WHO). World malaria report 2008. Geneva: WHO. 2008a

  26. World Health Organization–Global Malaria Program (WHO–GMP). (2007). Insecticide-treated mosquito nets: A WHO position statement. Geneva: WHO.


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