Malaria Vectors on Buka and Bougainville Islands, Papua New Guinea
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Journal of the American Mosquito Control Association, 18(2):100-106, 20O2 Copyright @ 2OO2 by the American Mosquito Control Association, Inc. MALARIA VECTORS ON BUKA AND BOUGAINVILLE ISLANDS, PAPUA NEW GUINEA R. D. COOPER aNo S. P. FRANCES Australian Army Malaria Institute, Gallipoli Barracks, Enoggera, Queensland 4052, Australia ABSTRACT, Anophelines were sampled from 82 locations on Buka and Bougainville islands in Papua New Guinea by larval collections, carbon dioxide-baited mosquito traps, and human biting catches. Anopheles farauti s.s. was collected in larval surveys but infiequently in mosquito traps on both islands; on Buka Island this species was readily collected in human biting catches. Anopheles faretuti 2 was commonly collected in larval surveys on both islands; however, it was not collected in either mosquito traps or human biting catches. Anoph- eles punctulatus was found only on Buka Island, where it was commonly collected as larvae, but rarely in human biting catches and mosquito Iraps. Anopheles lungae was collected as larvae liom only I site on Bou- gainville. Anopheles fararll s.s. fed consistently throughout the night (1900 0600 h); small peaks at midnight and dawn were not statistically significant. Of I,156 An. farauti s.s. specimens examined by enzyme-linked immunosorbent assay for malaria sporozoites, 20 were fbund to be positive; 72 were positive for Plasmodium - - .fulciparum and 8 were positive for P. vivax (247 variant 5;21O variant 3). Anopheles fara&ti s.s. seems to be the major malaria vector on these islands, whereas An. punctulatus may play a minor role on Buka Island. Anophele .t'arauri 2 is unlikely to be involved in malaria transmission on Buka or Bougainville islands. KEY WORDS Anopheles punctulatus group, malaria, Bougainville, Papua New Guinea INTRODUCTION a peace agreement was signed and a multinational peace-keeping group (PKG) was installed while the The islands of Buka and Bougainville are lo- political issues were resolved. Concern for the in- cated in the southwestern Pacific at the northern cidence of malaria in PKG personnel led to re- end of the Solomon Island Archipelago, and newed interest in the malaria vectors of the prov- make up the North Solomons Province of Papua ince. The following report details surveys New Guinea (PNG). Malaria occurs on both is- conducted to ascertain the species present and their lands and dichlorodiphenyltrichloroethane (DDT) role in malaria transmission. indoor residual spraying for vector control was implemented in 1961 and continued, at 2 spray rounds per year, until the early 1980s. Potential MATERIALS AND METHODS malaria vectors on the islands were identilied as Survey area and timings: Collections of anoph- Anopheles farauti Laveran, Anopheles punctula- eline mosquitoes were made from Arawa, Tonu, tus Ddnitz, and Anopheles koliensis Owen (Spen- and Buka areas of North Solomon Province, PNG cer 1961,1971). These speciesbelong to the (Fig. 1). Collections were made during the period Anopheles punctulatus group, which is now February-March 1999. known to consist of 12 closely related species Topography and climate oJ'the region' Buka Is- distributed throughout the southwestern Pacific land (area 850 km') is a raised coral reef composed and northern Australia (Foley et al. 1994; Cooper of limestone overlaid with plastic clays. Most of et al. 1996, 2OO2). Identification of the members the island (757o) is below 100 m; the highest point of the group by morphological characteristics is is 1,000 m. Much of the island has been cleared for unreliable. The An. farauti species are isomor- copra plantations and native gardens. Bougainville phic and the other members are now known to be Island (area 8,150 km') is made up of a series of polymorphic for previously used diagnostic char- volcanic peaks up to 2,6OOm. More than one half acters (Cooper et al. 2OO2).Because of this, over of the island consists of hills and mountains. Coast- the last decade, various molecular-based tech- al plains, made up of volcanic material distributed niques have been developed to accurately iden- by rivers, terminate on the coast with swamps im- tify these species (Cooper et al. 1991, Beebe and pounded by coastal sand dunes (Scott et al. 1967). Saul 1995). Although the original members of the The climate is continuous hot-wet with precipita- An. punctulal&.s group were known to be major tion of 2,600-3,300 mm/year (median of 14 years vectors in the region, the recent recognition of of data); rainless periods on average do not exceed several cryptic species within the group has now 2.5 days. The mean temperature is 27.3"C (24- resulted in uncertainty as to the actual role the 30"C)and the average humidity is 807o(McAlpine different members play in transmission of malar- et al. 1983). ia. Sut'vey methods: Larval and human night biting In the mid-1980s. the North Solomons Province collections were made in the Buka, Arawa, and attempted to secede from PNG. This resulted in a Tonu areas, and carbon dioxide (COr)-baited mos- civil war that closed the province until 1998, when quito trap (Rohe and Fall 1979) collections were too JUNE2002 MALARTA VEcroRS oN BUKA AND BouGAtNVrr-l-E ISLANDS. PAptJA NEw GUTNEA l0l BUKA ISLAND 5km 1oo 11t tfll n,'-o .!3 \ 4E'v. 1R 21 4A-ct I 22 23 26 27 25 30 c 41 EMPRESS 48 50 TONU AREA ARAWA AREA cf2 '73 .71 60r 74. 75 61o a J7 62 '7-g.zic tz\ 63r 81o '96 a 67 68 10km *..11ul-----J 2km Fig. 1. Location of anophelinesites surveyed on Buka and Bougainville islands, Papua New Guinea (site numbers as in Table l). made in Buka and Arawa. Larval sites were clas- terman 1996) and further identification was carried sified as established or unestablished. Established out by polymerase chain reaction-restriction frag- sites varied in size from small temporary pools to ment length polymorphism (PCR-RFLP) analysis permanent swamps; all had well-established flora of the ribosomal DNA internal transcribed spacer 2 and fauna and all contained some degree of organic region (ITS2), by the method of Beebe and Saul matter and plant debris. Unestablished sites were (1995). Where numbers permitted, at least 5 spec- all small temporary pools with little or no flora and imens from each site were identified with PCR- (tire f'auna and no organic debris; wheel ruts tracks) RFLP analysis. in unsealed roads were a common example of this All specimens collected in traps and human bit- type of site. ing were analyzed individually for the presence of Anophelines collected as larvae were maintained human malaria sporozoites by the enzyme-linked in their site water, fed finely ground goldfish food, immunosorbent assay (ELISA) procedure of Wirtz and reared through to adults. All adults were iden- et al. (1987). The head and prothorax were used for tified in the field by using The Mosquitoes of the South Pacific (Diptera, Culicitlae) (Belkin 1962). this analysis; the remainder of the specimen was Adults belonging to the An. punctulatus group then used for identification by PCR-RFLP analysis, as were preserved in liquid nitrogen, whereas speci- mentioned above. mens that were still larvae and pupae at the end of Average hourly biting collections made over 5 the study were preserved in 1007o methanol. With nights (1900-0600 h) were compared and analyzed this material, DNA was extracted from the abdo- by a l-way analysis of variance (ANOVA; mens by the Pat Roman method (Black and Muns- SigmaStat for Windows, Jandel Scientific Software, t02 JoURNAL oF THE AMERTCANMoseumo CoNrnor- AssocrATroN Vor-. 18, No. 2 Table l. Collection sites on Buka and Bougainville islands, indicating collection method, number and species collected, and larval site type (site numbers as in Fig. l). Speciesr Site Total Established Unestablished no. Collection collected fs.s. f2 larval site larval site I Larval 25 0 0 25 Drain 2 Larval 25 o 0 25 Drain 3 Lzuval 7 0 o 7 Wheel rut + Larval 6 0 6 0 Wheel rut Larval 9 0 5 0 Wheel rut 6 Larval 2l I 0 Wheel rut 7 Larval -)2 0 0 32 Wheel rut 8 Larval 9 0 5 0 Wheel rut 9 Larval 15 2 3 0 Swamp t0 Larval 16 0 5 0 Ground pool ll Larval 67 0 5 0 Wheel rut l2 Larval 13 0 5 0 Wheel rut '70 13 Larval 70 0 0 Wheel rut 14 Larval 33 0 5 t4 Wheel rut l5 Larval 26 0 5 0 Swamp 16 Larval 35 0 0 3s Drain 1'7 Larval 38 0 0 Swamp 18 Larval 40 0 0 40 Wheel rut 19 Larval 27 0 5 9 Wheel rut 20 Larval 6 0 0 6 Wheel rut 21 Larval 0 0 ZJ Wheel rut 22 Larval 5 0 0 Swamp 23 Larval 39 0 4 35 Wheel rut 24 Larval 49 0 0 49 Drain 25 Larval 55 0 0 55 Wheel rut 26 Larval 10 o 0 10 Creek 27 Larval 26 0 0 26 Drain 27 Trap 0 28 Larval 36 0 0 36 Wheel rut 29 Larval 35 0 0 35 Wheel rut 30 Larval 40 0 0 40 Wheel rut 30 Tiap 0 JI Larval 30 0 o 30 Drain 32 Larval 60 0 0 60 Wheel rut -f -) Larval 43 0 0 q3 Wheel rut 34 Larval JJ o 0 33 Wheel rut 35 Larval 56 0 0 56 Wheel rut -to Larval 15 0 3 t2 Pig wallow -)t Larval 87 0 0 87 Wheel rut 38 Larval l0 0 5 0 Swamp 38 Biting 1 1 0 3 39 Larval 45 0 0 45 Wheel rut 40 Larval 9 0 o 9 Wheel rut 41 Larval 32 0 0 JZ Pig wallow 42 Larval 7 0 7 0 Ground pool 43 Larval 59 o 5 0 Wheel rut 44 Larval 20 0 4 16 Wheel rut 45 Larval 8 0 5 0 Ground pool 46 Larval 20 0 0 20 Wheel rut 47 Larval l0 0 6 0 Wheel rut 47 Biting I 0 o I 48 Larval 26 0 0 26 Wheel rut 49 Larval 3l 0 I 28 Wheel rut 49 Tiap 0 50 Larval 6 o 6 o Drain -')| Larval 35 0 5 0 Swamp 52 Larval 26 0 5 0 Swamp 52 Biting 64 64 0 0 52 Trap x 2 6 5 0 1 53 Larval ll 0 0 1l Wheelrut 53 Trap 0 Larval 16 0 5 1l Pig wallow 54 Trap 0 JuNs 2002 Melenre VECToRs oN Bux,q nNo BoucerNvrr-le IsleNos, Plpur New GuNsa 103 Table l.