Mosquitoes, You and Climate Change

Mosquitoes require the proteins in blood to produce viable eggs © Sciengist

Mosquitoes require the proteins in blood to produce viable eggs © Sciengist

This article was originally published by RiAus on 4th September, 2015

 

Mosquitoes are undoubtedly some of the most annoying guests at Australian barbecues.

They attend only to feed on your blood, not your food.

Mosquitoes require the proteins in blood to produce viable, healthy eggs and you may have experienced: mosquitoes prefer some humans over others.

However, not all mozzies have a taste for human blood, some instead prefer to feed on other mammals and/or birds.

Some mosquitoes however, prefer a combination of sources.

Some Australian mammals and birds are hosts for mosquito-borne viruses

While there are over 300 species of mosquitoes in Australia, only a handful of them carry and transmit viruses or disease, and only some of them prefer human blood.

Ross River virus (RRV) is the most commonly reported mosquito-borne illness in Australia. Although it is not fatal, RRV can cause temporary, debilitating disease which may include arthritic symptoms.

There are several Australian mammalian and bird species capable of hosting the virus and several species of mosquito are known vectors: potentially capable of carrying the virus from the host animal to your backyard banquet.

As of July 2015, the incidence of RRV infection in Australia was already higher than that recorded annually for the last 10 years.

Recent climatic conditions on the east coast of Australia may be contributing to the regional outbreak, as the mosquitoes respond to favourable environmental stimuli.

All stages of the mosquito life cycle are dependent on optimal, species-specific conditions

Tiny, hatched mosquito eggs after inundation in water © Sciengist

Tiny, hatched mosquito eggs after inundation in water © Sciengist

The immature larval stage of the mosquito requires some form of aquatic environment after hatching from its tiny egg, and female mosquitoes find suitable sites to lay their eggs accordingly.

Dependent on species, the mosquito larvae may prefer fresh or brackish water, in fact all stages of the mosquito life cycle are dependent on optimal, species-specific conditions.

Similarly, arbo-virus hosts, such as wallabies, are themselves, responding in their own way to the environment and changing conditions.

As mosquitoes are dependent on and responsive to local environmental conditions, it is reasonable to expect some impacts of climate change on Australian mosquito populations, and the prevalence of the viruses they may carry.

Climate change predictions regarding mosquitoes are not cut and dry

Aquatic mosquito larval and pupal life stages (Image: wikipedia.com)

Aquatic mosquito larval and pupal life stages (Image: wikipedia.com)

Projected conditions for Australia under continued global climatic change, forecast increased temperatures, and an increase in the intensity of extreme rainfall.

These changes in annual climate would be considered favourable for mosquito populations. It is not, however, cut and dry.

Regional and seasonal variations in climatic conditions will occur, as they do currently. In fact annual average rainfall is predicted to decline.

This makes national predictions regarding impacts on mosquitoes a little tricky, with influences on regional mosquito micro-climates likely to vary greatly across the continent. Similarly, the environment the virus’ host species are faced with will vary.

Human responses to climate change may also determine the responsive mechanisms of mosquitoes

Vigilance is key, enjoy your snag without the bite (Image: Free Stock Photos)

Vigilance is key, enjoy your snag without the bite (Image: Free Stock Photos)

While populations of the dengue vector mosquito, Aedes aegypti, are resident in northern Queensland, outbreaks of dengue fever in Australia rely on importation of the virus, generally in the form of infected humans.

It has been suggested that changing environmental parameters may not solely influence the distribution of the dengue vector. Instead perhaps, our response to regional drying conditions through the installation of large water tanks may provide the species with favourable environments further south of its current range.

In addition, mosquitoes have demonstrated their ability to adapt to changing environmental conditions, an ability which may further facilitate range expansion under extreme conditions.

Continued population growth, urban sprawl and increased human travel are further variables in the mix, particularly where invasive mosquito species are concerned.

With contributing parameters varying for mosquito species and geographical regions, the only reasonable prediction at this point, is that humans will be required to be vigilant. Protecting yourself from biting mosquitoes, in both rural areas and urban developments is sensible: reduce the resident mosquitoes in your area by removing available egg-laying and larval sites; reduce your chance of being bitten by wearing suitable, protective clothing; encourage your local area to support regional mosquito surveillance.

And enjoy your snag, without the bite.

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