Surveillance for malaria outbreak on malaria-eliminating islands in Tafea Province, Vanuatu after Tropical Cyclone Pam in 2015.

The risk of malaria outbreak surfaced in Vanuatu after Tropical Cyclone (TC) Pam in March 2015. In June and July 2015 we conducted malariometric surveys on the islands of Tanna, Aneityum, and Erromango in Tafea Province, where malaria elimination had been targeted, to determine if malaria incidence had increased after TC Pam. No Plasmodium infection was detected by microscopy and PCR in 3009 survey participants. Only 6·3% (190/3007) of participants had fever. Spleen rates in children aged ⩽12 years from Aneityum and Tanna were low, at 3·6% (14/387) and 5·3% (27/510), respectively. Overall bed net use was high at 72·8% (2175/2986); however, a significantly higher (P < 0·001) proportion of participants from Aneityum (85·9%, 796/927) reported net use than those from Tanna (67·1%, 751/1119) and Erromango (66·8%, 628/940). A recent decrease in malaria incidence in Tafea Province through comprehensive intervention measures had reduced the indigenous parasite reservoir and limited the latter's potential to spur an outbreak after TC Pam. The path towards malaria elimination in Tafea Province was not adversely affected by TC Pam.

Malaria eradication on islands.

BACKGROUND: To be successful, a malaria control programme needs to be tailored to the local epidemiological characteristics. Vanuatu consists of 80 inhabited islands in the Southwest Pacific, with hypoendemic and mesoendemic malaria and suitable conditions for sustained parasite elimination. We aimed to assess whether malaria can be eliminated on isolated islands. METHODS: Weekly mass drug administration of chloroquine, pyrimethamine/sulfadoxine (Fansidar), and primaquine was carried out on the entire population of 718 inhabitants of Aneityum island for 9 weeks in 1991 before the onset of the rainy season. Simultaneously with the administration of drugs, permethrin-impregnated bednets were distributed to the entire population. Larvivorous fish were also introduced into several identified breeding sites of Anopheles farauti. Periodic malariometric monitoring has continued for the past 9 years. Two additional islands of Vanuatu, one with and one without malaria transmission, have been monitored for comparison. FINDINGS: High community involvement as measured by drug compliance (88.3%) and bednet provision (0.94 nets per villager) has resulted in sustained interruption of malaria transmission in Aneityum. The surveys showed complete absence of Plasmodium falciparum after mass drug administration, and P. vivax disappeared from 1996 onwards, with the exception of two instances of imported infections (one mixed infection in 1993 and one P. vivax infection in 1999). INTERPRETATION: Malaria can be eliminated on isolated islands with well-adapted short-term mass drug administration and sustained vector control if there is a high degree of community participation.