School is out (but don’t let mosquitoes bite)

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“School’s out forever
School’s out for summer
School’s out with fever
School’s out completely” Alice Cooper

The end of the school year for students completing high school is here. School is out so the partying can start! Lets hope fever isn’t part of the story too.

For many students, this means traveling overseas for “schoolies” celebrations. The health and wellbeing of students attending “schoolies” has been front of mind of many parents and local authorities. This isn’t surprising given the risk taking behaviours many engage in.

Health authorities are often warning about potential health risks. However, with many travelling overseas for end of school celebrations, a range of mosquito related health risks may be experienced. The steps taking to avoid mosquito bites at home need to be changed if travelling to regions of the world where different mosquitoes and more serious mosquito-borne pathogens are found.

Overseas travel brings different risks

The risks may be significantly greater if travelling overseas to tropical regions such as SE Asia and the Pacific. Bali is a particularly popular party destination and also one with a high risk of mosquito-borne disease, especially dengue.

There are other mosquito-borne diseases to be wary of. Fortunately, the steps taken to avoid dengue will also assist in preventing exposure to Zika or Chikungunya too. There are occasionally cases of Japanese encephalitis virus in Australian travellers but they are rare.

Some regions will have a risk of malaria too. If you’re traveling to one of those regions, best consult your local travel health professional.

One of the main differences Australian travellers will face when spending time in regions prone to dengue outbreaks is that the mosquitoes that spread the virus bite during the day. We’re familiar with the local warnings to avoid mosquitoes at dawn, dusk, and overnight here in Australia. The mosquito that drives dengue outbreaks is most commonly Aedes aegypti, a mosquito that bites during the day.

We’re also likely to reach for the mosquito repellent when mosquitoes are abundant, as they often are, during summer coastal holidays. Bu Aedes aegypti is generally not that abundant. Don’t wait to notice the mosquitoes biting before putting on repellent.

These mosquitoes are also most likely to be present around urban areas and villages. These mosquitoes aren’t found in wetlands, they like living in water-filled containers where people live. Don’t think that just because you aren’t visiting wetlands or rainforests that there won’t be a risk of mosquito-borne disease!

Here are three tips on protecting yourself against mosquito-borne disease if you’re travelling overseas for “schoolies” celebrations:

1. Protect yourself against day-biting mosquitoes. Apply a repellent before breakfast and apply it like sunscreen. An even cover of exposed skin is required. Don’t bother applying it to clothing or “spraying it around the room”, that won’t protect you from bites.

2. Take repellent with you. Australian repellents must be registered with the Australian Pesticides and Veterinary Medicines Authority who test for efficacy and safety. You may not be able to get a hold of similar products overseas. Use a repellent that contains either diethyltoluamide (aka DEET) or picaridin; these formulations are readily available in local supermarkets and pharmacies. Oil of Lemon Eucalyptus is useful too but these formulations are often difficult to find.

3. Even if you’re staying at an expensive resort, where mosquito control is probably in place, take insect repellent for those day trips to local villages or markets. These are places and times where you may be exposed to “dengue mosquitoes”.

Don’t forget to check out Smart Traveller before heading off to Bali…or anywhere else for that matter. They provide all the updates on health and security concerns.

Photo at top of this post by Jed Villejo on Unsplash

Australian mosquitoes discovered in California: What does it mean?

AedesnotoscriptusThe movement of mosquitoes around the world is more likely to drive the spread of mosquito-borne disease outbreaks than a changing climate. Health authorities received yet another reminder of how easily pest mosquitoes can move about with human activity. They can sneak in and set up home before we even know they’re there.

Mosquitoes deserve more credit. We’re impressed with the adaptation of birds, fish and frogs to narrow ecological niches or extreme environments. How about showing the same respect for these insects that have left behind their life in tree holes or leaf axils and moved into our cities. They’ve switched tastes from primates to people and their pets. They may only fly short distances but we help move them around the world with increasing frequency accompanying globalisation and discounted airfares.

Exotic mosquitoes and international travel

Long before planes made the planet a much smaller place, we were already moving mosquitoes massive distances. It could probably be argued that the brown house mosquito, Culex quinquefasciatus, first came to Australia in water filled barrels with the first fleet and the movement of the Yellow Fever mosquito, Aedes aegypti, and associated pathogens from the Caribbean to Philadelphia and triggered a catastrophic outbreak of disease in 1793.

In more recent times, the spread of the Asian tiger mosquito, Aedes albopictus, has been well documented and has raised concerns amongst international health authorities with regard to outbreaks of disease caused by dengue and chikungunya viruses.

This week saw the announcement that a mosquito, Aedes notoscriptus, had made its way from (most likely) Australia to California. The news attracted plenty of attention from media in Australia and North America. The mosquito discovery was due to the diligence of two agencies in Los Angeles, The Greater Los Angeles County Vector Control District and San Gabriel Valley Mosquito and Vector Control District. The joint media release from these two agencies described the discovery and identification:

“During an expanded search this summer for the invasive Asian tiger mosquito, staff from the San Gabriel Valley Mosquito and Vector Control District (SGVMVCD) and the Greater Los Angeles County Vector Control District (GLACVCD) collected unusual specimens from a couple of homes. After someinitial research, photographs of the mosquito were sent to Dr. Cameron Webb and John Clancy with theMarie Bashir Institute of Infectious Diseases and Biosecurity at the University of Sydney, Australia and they confirmed it to be Aedes notoscriptus.”

 

This was a great example of international collaboration. There was also little doubt that without the availability of high quality photographs we wouldn’t have been able to offer such a rapid identification. Not so long ago we would have had to ship specimens back and forth to confirm identification.

What does this mean for California?

Apart from questions regarding how this mosquito made it half way around the world, the critical issue now is to assess what pest or public health risk this mosquitoes poses to Los Angeles, California and North America more generally.

Aedes notoscriptus (commonly referred to as the ‘backyard mosquito’) is widespread in Australia. From the cold climates of Tasmania to the tropical north of the country. The mosquito is also found in New Zealand, Western Pacific and Indonesia.

The mosquito is closely associated with urban areas. Eggs are laid in a wide range of natural and artificial water-holding containers. There are very few Australian’s who haven’t been bitten by this mosquito. It is a constant companion at summer BBQs and is considered a nuisance-biting pest, mostly biting in the afternoon and early evening. However, it does have broad tastes when it comes to blood feeding. The abundance of this mosquito is relatively low compared to some of our “wetland” mosquitoes (such as Aedes vigilax and Culex annulirostris) and the mosquito doesn’t fly far, generally less than 200m.

The low natural dispersal of the mosquito is thought to have contributed to the emergence of subpopulations in some regions of Australia. More recent studies have found that phylogenetic analyses of DNA sequence data from mitochondrial markers indicate the mosquito is a complex of divergent genetic lineages, some geographically restricted, others widespread. There is, however, no doubt assisted movement of mosquitoes is also occurring around the country. As with any container-inhabiting mosquito, human movement will drive the spread of this mosquito in North America.

From a public health persepctive, Aedes notoscriptus is a less significant nuisance-biting pest than Aedes albopictus and Aedes aegypti. However, it is a vector of arboviruses and parasites. Aedes notoscriptus is an effective vector of Ross River and Barmah Forest viruses. A range arboviruses have also been isolated from field collected specimens in many parts of the country and the mosquito has been implicated in Ross River virus transmission in major cities including Sydney and Brisbane. Neither Ross River virus or Barmah Forest virus are known to exist in California.

Fortunately, the mosquito is generally not considered an effective vector of dengue viruses, West Nile virus, Yellow Fever virus or, chikungunya virus but it has been shown to be susceptible to Rift Valley fever virus. Aedes notoscriptus is an effective vector of dog heartworm, Dirofilaria immitis.

How did it get there?

We may never know. Mosquitoes can be moved about in lots of different ways, from cargo holds in aircraft and ships to baggage and belongings of individuals. Industrial, mining and agricultural equipment may provide a route of movement too.

Given that established populations have been discovered, it may be more likely that personal belongings may have been moved to California from Australia or New Zealand with travellers or family relocating for work. Perhaps surveys of the local community, combined with genetic analysis of the specimens will help answer this question.

The take home message for local authorities, both in California and Australia, is that the mosquito did make the trip, slipped through the cracks of quarantine and become established. While this introduction may not pose a significant impact to California, the introduction of Aedes albopictus to Australia could have far more substantial impacts. If we can export our mosquitoes, we should remain vigilant of the potential for exotic mosquitoes to find their way to us from Asia, Europe or the Americas.

What should authorities do?

There are already strategies in place for the surveillance and control of container-inhabiting mosquitoes in California. These strategies would prove effective in tracking and controlling Aedes notoscriptus. The one advantage authorities have is that Aedes notoscriptus is readily collected in carbon dioxide baited light traps whereas Aedes albopictus and Aedes aegypti are generally not collected as often by these traps.

In summary, the mosquito should not be considered a major pest or public health risk. The priority for local authorities should remain the other container-inhabiting species such as Aedes albopictus and Aedes aegypti. Notwithstanding these species, other mosquitoes associated with urban environments, particularly Culex spp., are currently playing an important role in one of the largest outbreaks of West Nile virus. In fact, the “proportion of mosquitoes infected with West Nile virus is at the highest level ever detected in California“.

Californian authorities have enough on their plate without the extra worry of an Australian hitchhiker turning up and moving in!

The wonderful photo of Aedes notoscriptus at the top of this post is provided by Jared Dever, Direcror of Communications, at Orange County Vector Control District.