Ross River virus along the east coast of Australia
Ross River virus is the most commonly acquired mosquito-borne infection in Australia. It causes a potentially serious illness with flu-like symptoms and, although not fatal, can be seriously debilitating. There are around 5,000 cases of disease reported each year with cases reported from across the country. It is something of an urban myth to suggest that “Ross River virus is moving south from Queensland”. In fact, some of the largest outbreaks in recent years have been in southern states. South-west Western Australia has had considerable activity in recent years.
Along the east coast, activity has actually been reasonably low. Flooding of inland regions during 2010-2012 resulted in some substantial activity west of the Great Dividing Range but along the coast, not that much has been happening. One explanation is that the average to above average rainfall the east coast has experienced in recent times is not conducive for the major pest mosquitoes associated with coastal wetlands. With drier conditions forecast for this summer, conditions improve for these mosquitoes. The recent king tides that occurred in the first week of 2014 have provided an opportunity for a major emergence of mosquitoes. This may get the ball rolling for a big year of mosquito activity along the coast.
While we can forecast a rise in mosquito populations, predicting an outbreak of Ross River virus is much more difficult. The key reason for this is that mosquitoes don’t hatch out of the wetlands infected with the virus, they must bite an infective animal (most commonly kangaroos and wallabies) first. This means that complex interactions occur between mosquitoes, environmental conditions and wildlife ecology. We don’t quite understand how all these factors interact just yet. What we do know is that it is unusual to have more than a couple of years without at least a minor outbreak of Ross River virus and with a combination of suitable environmental conditions, could the Autumn of 2014 see a surge in cases of disease?
Will the Eliminate Dengue project eliminate dengue?
The Eureka Prize winning Eliminate Dengue project has many excited by the prospect that mosquitoes could be “vaccinated” against dengue infection. There have been some great results from Cairns, Australia, where field released Wolbachia-infected mosquitoes have natural spread through study sites and successfully replaced large percentages of “wild” mosquitoes. However, it is one thing to have a well resourced field study looking at the spread of Wolbachia infected mosquitoes alone, will they actually reduce rates of dengue? To test the effectiveness in a dengue-endemic region, the Eliminate Dengue project is currently undertaking field testing in Vietnam.
Unfortunately, 2014 hasn’t got off to a good start to the project. News of some small, but not insurmountable, hurdles has come through from Vietnam where populations of Wolbachia-infected mosquitoes on Tri Nguyen Island aren’t persisting at forecast levels. While the rate of Wolbachia-infected mosquitoes reached close to 80% in August 2013, the rate had fallen to below 65% by early December 2013. Whether the falling prevalence of infected mosquitoes is due to higher mortality rates of infected mosquitoes (or at least some degree of reduced competitive advantage) or other environmental factors is yet to be determined. Hopefully better news will come later in the year.
Pulling ticks and pushing Lyme in Australia
Ticks, and their health impacts, in Australia are gaining some increasing notoriety. We’ve always known that ticks can pose a potentially serious health impact due to bite reactions. There is also the fascinating “tick induced red meat allergy” that is being seen more commonly around Sydney. However, the controversy around the potential presence of a pathogen causing Lyme Disease, or a Lyme-like illness, spread by local ticks has focused the attention of local authorities and communities where ticks are abundant.
It will be interesting to see what comes out of the Tick-induced Allergies Research and Awareness (TIARA) group and the federal government’s Clinical Advisory Committee on Lyme Disease over the coming year. In addition, the largest study into tick-borne pathogens is currently underway at Monash University with specimens being processed from across the country in an effort to find, identify and (hopefully) culture any pathogens present so that we can better understand the complex issues surrounding tick-borne illness.
Even if new tick-borne pathogens are documented, the advice provided by local authorities on avoiding tick bites is unlikely to change significantly. However, what has been missing from the promotion of tick bite prevention methods is some good quantitative evidence on the best measures to prevent bites as well as how best to remove a tick once it has attached. Many of the products promoted for use haven’t been registered by the Australian Pesticides and Veterinary Medicines Authority (APVMA) for use against ticks; creating difficulties for health authorities to recommend their use. Also, despite some recent guidelines on tick removal from Europe, these guidelines may not be appropriate against local ticks that have the potential to cause anaphylaxis and paralysis. So, do you just pull off attached ticks or kill them first with an insecticide? We’re expecting some guidelines from the TIARA group this year (in the meantime, stay tuned for a blog post about this from me in coming weeks).
Dengue & FIFA World Cup in Brazil
There wouldn’t be a better place to be for a football loving entomologist than the FIFA World Cup in Brazil in June & July 2014. Enjoy some football; research some dengue!
Brazil has been a focus for dengue research for many years. With tens of thousands of travelers planning to visit Brazil for the world cup, concerns have been raised regarding the possible risk to travelers of dengue. Those risks are well founded as, not only is dengue endemic in the country, but many of the travelers to Brazil may not be fully aware of the risks and the appropriate personal protection measures they should take. We’ve seen this in recent years with a rise in the number of imported cases of dengue and Chikungunya virus with Australian travelers returning from SE Asian destinations. I’ve written about the need to educate travelers on avoiding mosquito bites in these dengue-endemic regions here.
While there is obviously a risk to travelers, a risk often overlooked is the possibility that travelers returning to their home countries may inadvertently introduce dengue viruses to local mosquito populations. As is the case in Australia, there are regions where suitable mosquitoes are present that can transmit dengue viruses but the disease is not endemic. Sporadic, and occasionally significant, outbreaks are triggered by infective travelers. Could we see locally acquired cases of post-World Cup dengue in North America, Europe or Australia? Conversely, could travelers import a new mosquito-borne virus into South America? (see below)
Chikungunya in the Americas
2013 was the year that Chikungunya really made its presence felt in Australia. This was due to the Asian Tiger Mosquito knocking at the door of mainland Australia and raising the risk that a temperate climate tolerant mosquito may one day be widespread in Australia and, as a key vector of Chikungunya virus, could pose a serious health risk. Despite no known locally acquired cases of the infection in Australia, the numbers of infected travelers returning from Chikungunya endemic regions jumped dramatically in 2013 with over 100 cases reported compared to an average of about 25 cases for the previous two years.
It was at the end of 2013 that the virus was first detected in the Americas. By the first week of 2014 almost 100 cases now reported from Caribbean island of St Martin. Now with effective vectors of Chikungunya virus throughout much of South America and many parts of North America the question of whether more outbreaks are likely to occur should be asked. With increased travel to South America in conjunction with the FIFA World Cup (and additional tourism activity prompted by the tournament), perhaps the greatest risk is posed by travelers introducing the virus to other countries where suitable vectors are present. Perhaps Zika virus may pop up too in South America too…
The media love news of a new mosquito repellent. There is likely to be a steady stream of news stories this year about the discovery of new mosquito repellent chemicals. Considerable research is going into the discovery of chemicals, derived from a range of botanical and non-botanical sources, that may hold potential as mosquito repellents. Some neat computational analysis is being done that includes “molecular field topology analysis, scaffold hopping, and molecular docking” to uncover new repellent products. A recent study identified a few “nice” smelling chemicals that may be effective and more user friendly repellents. There also seems to be a focus on products derived from “food grade” substances, I assume as a way to avoid some of the registration obstacles and/or allow greater marketability for the “natural” repellent market. I expect to see many more announcements over the course of the year….but very few new products being made available that will make much of a differences “in the real world” (at least this year).
These “discoveries” are usually framed within the context that N,N-diethyl-3-methylbenzamide (DEET) based repellents are unsafe or unpleasant to use. This argument lacks substance when you considered that the safety of DEET is demonstrated time and time again. In addition, most circumstances call for the use of only a low or moderate concentration DEET-based repellent. A formulation that only contains about 10% DEET will still provide a few hours protection. Interestingly, a lot of the commercial “low dose” DEET-based repellents are being replaced by picaridin-based (a product considered more “user friendly”) repellents here in Australia.
Rather than new active ingredients, what we really need is better formulations. A move away from topical repellents would be a great move and overcome the difficulties in “user compliance” to get the most effective results. The most promising product in this regard is metofluthrin. This product has recently been registered for use by the APVMA in Australia so I’m looking forward to seeing it available in local stores. It has proven to be effective in preventing mosquito bites. What is most interesting is that the product is usually included with battery operated “clip on” devices that individuals wear. They may not prevent bites when mosquito populations are high (e.g. close to wetlands) but could be a useful alternative to topical repellents when mozzies are just causing a mild annoyance.
$600,000 would buy a lot of mosquito repellent!
One of the most amazing things to happen last year was the phenomenal support provided to a crowd-funded mosquito repellent patch that purported to make the wearer invisible to mosquitoes. The company raised almost US$600,000 for filed testing of their patches in endemic regions of Africa. Yep, over half a million dollars.
I’ve written about what is required to evaluate new mosquito repellents (it was easily the most read post on my blog last year). Field tests of the Kite Patch are scheduled to commence in Uganda in January 2014 so I will be keeping a keen eye out for any updates. Most importantly, I’m keen to see some published peer-reviewed papers reporting on field and laboratory testing of these new repellents. Hopefully we’ll know by the end of the year whether the “dream” of an effective non-topical repellent can become a reality. The next interesting development will be when the patches are sent out to supporters of the crowd funding campaign. This isn’t expected to be until late 2014 or early 2015 (after the completion of Uganda field tests and EPA approvals).
The 11th Mosquito Control Association of Australia conference will be held in Mandurah, Western Australia on 7-10 September 2014. The conference will be held at The Sebel Mandurah and is shaping up to be an exciting forum. Mandurah is located an hour south of Perth and plays an important role in mosquito ecology, being located on the Peel and Harvey estuaries with large areas of tidal saltmarsh habitat. Management of mosquitoes and mosquito-borne disease has been an important issue for local authorities.
The theme of the 2014 conference is “Bringing good science to strategic programs” will bring together research entomologists, field biologists, and vector control specialists in a unique networking environment designed to promote collaboration and partnerships to improve preparedness, prevention, and control of vector-borne diseases of medical importance. Keep an eye on the MCAA website for more details in the next month.
So, it looks like there will be plenty of medical entomology stuff to keep an eye on for 2014, I wonder what surprises will be tossed up….