Mosquito community dynamics

 Project Details
Title: Impacts of tropical deforestation and fragmentation on mosquito community
Researchers: Hayley L. Brant (Ph.D student), Professor John Mumford (Ph.D supervisor), Dr Robert Ewers (Co-supervisor), Dr Suzan Benedick (Malaysian Collaborator)
Nationality: International

 Sampling details and required resources
Spatial Scale: 2nd Order
Sampling Sites: Old growth controls, Fragments block A, Fragments block B, Fragments block C, Fragments block D, Fragments block E, Fragments block F, Oil Palm Control
Time Frame: 7 February 2012 until 1 October 2014
Resources: Research Assistant(s), Vehicle

 Rationale and questions
Land use changes, such as deforestation, urbanisation, water management and agricultural practice, are the main drivers of emerging infectious diseases (EIDs), which can result in public health and economic tolls (Patz et al. 2000). Each environmental change can have a significant effect on habitat quality and microclimatic conditions, which can affect vector abundance, survivorship, human biting behaviour and vector competence (Patz et al. 2000; Afrane et al. 2008). Land use change has been linked to emerging and re-emerging diseases (Gratz et al. 1999), especially zoonotic pathogens. As zoonotic pathogens tend to have high fertility rates and no reliable cure, vaccine or therapy (e.g. Nipah virus in Malaysia), they must be monitored to avoid public health disasters (Patz et al. 2004). This project will investigate how mosquito community dynamics are affected by tropical deforestation and fragmentation. Three main questions will be addressed:

1)      What is the effect of land use change on the human-landing rate, diversity and composition of mosquitoes

2)      What are the impacts of deforestation and fragmentation on mosquito abundance, community composition and public health

3)      What is the impact of deforestation and agricultural development on malaria epidemiology?

The overall outcome of the project is to collect extensive data on mosquito presence, diversity, abundance, and disease rates within Sabah. This will be used to identify if land use change, including deforestation and fragmentation, has a big impact on mosquito community dynamics and infection rates.

Question 1: Ovitrap surveillance and bare leg catches (BLC) will be used to measure the human-landing rate, diversity and community composition of mosquitoes. Ovitrap surveillance will be carried out in the SAFE Project 2nd order points of blocks B, C, D, E, OG2, OG3, OP1 and OP3. They will also be placed around villages within Benta Wawasan estates (Belian and Selangan Batu). BLC will be carried out in the SAFE Project 2nd order points of blocks D, E, OP1, OP2, OP3, OG2 and OG3. Two ovitraps will be used; a larger one (see Brant 2011, MSc. Thesis) and a smaller one based on the design of Lenhart et al. (2005). The smaller ovitrap will consist of a dark plastic container (diameter 7 cm, depth=10 cm), with an overflow hole near the rim of the container to avoid overflow of water during heavy rain (Yap & Thiruvengadam 1979; Rozilawati et al. 2007).  It will be tied 1 m high to trees, or underneath houses in the villages. A piece of cotton cloth (12 cm x 27 cm) will be placed within the ovitraps as an ovipositional substrate, and 200 ml of sterilised water is then added. All ovitraps are placed under heavy shade, measured by a densiometer, to ensure mosquitoes will be attracted to the traps. Water temperature and canopy cover are to be recorded at each site during the set-up of ovitraps. After six days, the traps will be collected and all ovipositional substrates are dried and placed in individual plastic bags. All water is carried back to the laboratory, for larvae to be counted and reared through to adults for identification. Eggs will be counted on the ovipositional substrates and the rim of the ovitraps by using a dissection microscope. After counting, unhatched eggs will be placed in water to hatch out. The human landing rate of mosquitoes will be measured using BLC. A pilot study demonstrated that mosquitoes in SAFE Project 2nd order points (block E, D, OP3, OG2) had peak Anopheles biting period occurring between 18:00-23:00 h. Within pairs, the collectors, with the aid of red torch lights, will aspirate mosquitoes off their own legs for the first 50 minutes of each hour, and then rest and prepare a new sampling cup for the remaining 10 minutes. Collected mosquitoes will be placed in cups covered with a net cloth, and a new cup will be used during every hour of collection. Mosquitoes will then be taken back to the field laboratory to be killed and sorted into individual tubes with silica gel. Identification of Anopheles species will occur at the Universiti of Malaya, and the other genera at the Natural History Museum (London). Question 2: Post logging data collection will be conducted; using the same methods mentioned in Question 1. Question 3: data from previous malaria cases will be collected from local medical clinics. These will be mapped against land use and land cover maps to see if there’s a trend between deforestation and malaria cases.

Output Files

  • Effects of marking methods and fluorescent dusts on Aedes aegypti survival

    Dickens, B. and H. Brant. 2014. Effects of marking methods and fluorescent dusts on Aedes aegypti survival. Parasites & Vectors 7:65. Abstract: Background Tracking the movement of mosquitoes and understanding dispersal dynamics is essential for the control and prevention of vector-borne diseases. A variety of marking techniques have been used, including dusts and dyes. Methods In this study, Aedes aegypti were marked using fluorescent dusts (‘DayGlo’: A-19 Horizon Blue & A-13-N Rocket Red; ‘Brian Clegg’: pink, blue & red), fluorescent paints (‘Brian Clegg’: blue, red & yellow) and metallic gold dust (‘Brian Clegg’). Dusting methods were those previously used in mark-release-recapture experiments, including application with a bulb duster, creation of a dust storm or shaking in a bag. Results Results [...]

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  • Impact of tropical deforestation and fragmentation on mosquito community dynamics

    Brant, HL, RM Ewers, I Vythilingam, C Drakeley, S Benedick and J Mumford. 2014. Impacts of Tropical Deforestation and Fragmentation on Mosquito Community Dynamics. ACTMP. Kuala Lumpur, Malaysia.

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