Mosquito distribution in a saltmarsh: determinants of eggs in a variable environment

Abstract

Two saltmarsh mosquitoes dominate the transmission of Ross River virus (RRV, Togoviridae: Alphavirus), one of Australia's most prominent mosquito-borne diseases. Ecologically, saltmarshes vary in their structure, including habitat types, hydrological regimes, and diversity of aquatic fauna, all of which drive mosquito oviposition behavior. Understanding the distribution of vector mosquitoes within saltmarshes can inform early warning systems, surveillance, and management of vector populations. The aim of this study was to identify the distribution of Ae. camptorhynchus, a known vector for RRV, across a saltmarsh and investigate the influence that other invertebrate assemblage might have on Ae. camptorhynchus egg dispersal. We demonstrate that vegetation is a strong indicator for Ae. camptorhynchus egg distribution, and this was not correlated with elevation or other invertebrates located at this saltmarsh. Also, habitats within this marsh are less frequently inundated, resulting in dryer conditions. We conclude that this information can be applied in vector surveillance and monitoring of temperate saltmarsh environments and also provides a baseline for future investigations into understanding mosquito vector habitat requirements. Journal of Vector Ecology 42 (1): 161-170. 2017.

How do local differences in saltmarsh ecology influence disease vector mosquito populations?

“…Increased samphire cover was the only shared predictor among sites for mosquito abundance. Previous studies on vector distribution within saltmarshes have shown a strong preference for regions with samphire, (Gislason & Russell, ; Dale et al ., ; Jacups et al ., ; Rowbottom et al ., ) because this habitat provides substrate for eggs of aedine mosquitoes. Other well‐known indicators of mosquito abundance include combinations of rainfall and high tides (Tong & Hu, ; Kelly‐Hope et al ., ; Jacups et al ., ; De Little et al ., ; Werner et al ., ; Koolhof et al ., ) because these provide hatching triggers for Aedes mosquitoes (Bader & Williams, ).…”

“…For example, variation in the nature and number of aquatic competitors and predators in saltmarshes has been reported to influence mosquito oviposition (Mokany & Shine, ; Eitam & Blaustein, ; Vonesh & Blaustein, ), thereby altering the spatial distribution of mosquito assemblages. Research also has shown that presence of competitors and predators within aquatic environments can impede mosquito larval development, resulting in reduced larval survival, a slower developmental rate and smaller adult mosquitos (Knight et al ., ; Alto et al ., ; Vonesh & Blaustein, ; Farjana et al ., ; Rowbottom et al ., ; Rowbottom et al ., ). Similar changes to mosquito development, size and survival can also be observed with environmental stress, such as increases in water temperatures and salinity and eutrophication (Clark et al ., ; van Schie, ; Kokkinn et al ., ; van Schie et al ., ; Williams et al ., ; Chaves et al ., ; Muturi et al ., ), which can, in turn, influence vector competence and virus transmission intensity (Paaijmans et al ., ).…”

“…In southern Tasmania, the location of this study, Ae. camptorhynchus is responsible for infecting an average of 26 people per annum, with outbreaks per year reaching 117, and cases occurring predominantly in suburbs adjoining saltmarshes (Robertson et al ., ; Carver et al ., ; Rowbottom et al ., ). Aedes camptorhynchus rapidly colonizes waterbodies after significant rainfall and tidal inundations and is capable of tolerating salinities exceeding that of sea water (Carver et al ., ; van Schie et al ., ).…”

Rapid identification of shallow inundation for mosquito disease mitigation using drone-derived multispectral imagery

“…Laboratory simulations were first implemented to explore the relationship of water depth and vegetation cover, typical of a South Australian saltmarsh on rich organic substrate, to NIR reflectance (Rowbottom et al, 2017). The findings subsequently contributed towards analyses of multispectral drone imagery that attempted to map potential breeding areas of focal saltmarsh mosquito species, Aedes vigilax and Aedes camptorhynchus, known to be vectors of the Ross River Virus (RRV) in Australia (Johnston et al, 2014).…”

Influence of the aquatic plant, Lemna minor on the development and survival of Culex pipiens mosquito immature.

“…Aquatic plants can be influenced the behavior and survival of mosquito adult and immature stages (Angerilli and Beirne, 1974;Rowbottom et al, 2017). It may reduce the wave action of the water and thus provide a suitable substrate for oviposition and may also restrict oviposition by rendering the water surface inaccessible to ovipositing female.…”