CHIKV mostly over

Coconuts · Post by **Coconuts** » Fri Dec 05, 2014 7:50 am

I have been closely monitoring the spread of chikungunya virus (CHIKV) throughout the Caribbean. This single-stranded RNA virus was discovered in Tanganyika in 1952, and genetic studies indicate that it first evolved in the 1700's. Since then, it had spread to other locations in Africa, as well as to South and Southeast Asia. CHIKV first appeared in our hemisphere in St. Martin, precisely one year ago, and from there spread quickly throughout the Caribbean. The first case in the VI was reported in May, and at that time, predictions were made that it would peak later this year. The only way to get CHIKV is to be bitten by a mosquito that has previously bitten someone in the infectious stage of the disease, which lasts about a week. The symptoms include a high initial fever, and then significant joint pain and headaches for that week. Fortunately, everyone who comes down with the disease is immune for life, and so the local population rapidly develops so-called "herd immunity", and becomes incapable of sustaining the virus.

CHIKV's primary carrier is the Aedes aegypti mosquito, which is a household dwelling insect that normally stays within a 200 ft radius during its lifespan. Since CHIKV transmission requires that a mosquito bite an infected individual, and then another uninfected person, the disease spreads most easily in areas with dense residential populations. St. John, with the National Park and a small population, is in a much better position than, say, downtown Charlotte Amalie. If you happen to be bitten by a mosquito while hiking a trail on St. John, the odds that that mosquito had previously bitten an infected person are extremely low.

While the pain and suffering of those who have been infected is unfortunate, the good news is that infection rates on St. Thomas and St. John have plummeted in recent weeks (the same cannot be said for St. Croix, where the problem is likely to get worse before it gets better). Reported cases on St John were always so low as to be statistically difficult to interpret, but St. Thomas vividly illustrates the trend. The following graph from the VI Health Department shows how quickly herd immunity has set in, and broken the train of transmission:

: Reported cases of CHIKV vs time

While the relative isolation and gentle trade winds of our villas on Gifft Hill restrict mosquito issues to occasional days after heavy rains, CHIKV has led us to consider new ways to reduce mosquito local populations. We have recently deployed two new tools in our arsenal, with four "Mosquito Deleters" and Biocare mosquito traps set out in and around each villa (links below). These pretty clever and environmentally friendly devices exploit hard-wired behaviors in mosquitos to disrupt their life cycle without the use of toxins. We are encouraging everyone we know to adopt these measures as well. It has not escaped our attention that these devices might also provide some wonderful summer relief to our pool and yard in New Hampshire, not to mention the homes of other forum members.

http://www.mymosquitodeleter.com/index.php/how-it-works

http://store.doyourownpestcontrol.com/b ... quito-trap

All the best,

Kevin

RickG · Post by **RickG** » Fri Dec 05, 2014 4:04 pm

This is all good news. There are some big gaps in the reporting, but anecdotally the cases are down too.

Did you find any permethrin or bifenthrin based solutions? We have Mosquito Authority treat our DC yard in the summer and it keeps the mosquitoes away. I've been real happy with the performance, but its not safe for aquatic creatures.

Cheers, RickG

Caw954s · Post by **Caw954s** » Sat Dec 06, 2014 7:05 am

Thanks for that post coconuts. Another non-toxic product that I use are the mosquito donuts. They contain a bacteria (BTI) that only attacks the mosquito larvae in water and is non-toxic to other organisms in the water (I'm an aquatic biologist and work at the EPA). The donuts are safe for use around birds, wildlife, children, and pets. Mosquito Donuts have been registered by the EPA for use in animal watering troughs and fish habitats. The donuts are perfect for fountains and other man-made water features, any standing water situation. You can break off a piece of donut for smaller areas and the donuts float and last approximately two weeks. The Aedes aegypti mosquito can easily breed in small areas inside your house, like basement drains and plant pot saucers. But, the mosquito donuts only kill the larvae, not the egg and a Aedes aegypti mosquito egg can withstand dry conditions for long periods and then hatch quickly when the eggs receive water again. So, you could leave a piece of mosquito donut in a plant pot saucer, doesn't bother the donut if it's dry and it will release the BTI again when wet.

Coconuts · Post by **Coconuts** » Sat Dec 06, 2014 9:25 am

Rick G &Caw954s: Yes, we do use pyrethrins and pyrethroids for mosquito control, in addition to lethal ovitraps. Pyrethrin is a natural, biodegradable compound extracted from chrysanthemum flowers, which causes insect nerves to fire constantly, leading to their death. It has no effects on mammals, and is described by the USDA as "the safest of all insecticides". We have a small automatic dispenser of pyrethrin by the bathroom in the great room. Pyrethroids such as permethrin and bifenthrin are very similar man-made derivatives, and I was surprised to find that all of St. John Hardware's various insect killing sprays are based on these compounds. No higher octane insecticides are available for sale, at least not there. Even the spray applied during visits by our insect control team (Deltamethrin) is a pyrethroid.

SJH also sells "Mosquito bits", which are granules that contain BTI, and as Caw954s points out, this bacteria is perfectly safe for mammals, but deadly to insects. Its toxins create lethal pores in insect gut cell walls; we sprinkle some granules in our shower traps from time to time. We used to use this as an organic alternative to traditional and nastier insecticides (typically organophosphates) back when we were living on the farm. We have heard of the Mosquito Donut version, but haven't yet used them; thanks for the reminder!

All the best,

Kevin

loria · Post by **loria** » Sat Dec 06, 2014 6:09 pm

Great info-- and thanks-- we use the donuts up north for lavae control.....one thing i wonder about is the effect on the bat populations..... if we delete mozzies.....just a thought....as bats are having a tough time of it anyway

Caw954s · Post by **Caw954s** » Sat Dec 06, 2014 6:41 pm

Does my heart good to read that you, loria, are concerned about bats...I love bats too! I so enjoy watching them fly and catch bugs at twilight. Don't worry, we'll never eradicate Mosquitos, they'll be here long after we're gone!

Coconuts · Post by **Coconuts** » Sat Dec 06, 2014 11:02 pm

Caw954s: "Don't worry, we'll never eradicate Mosquitos".

Things that once seemed certain are now in play. I spent yesterday down at Harvard's Wyss Institute, where we are co-developing a novel system for in-situ sequencing of the transcriptome. Folks there are all abuzz over a new and powerful tool, CRISPR/Cas9, and are already considering ways to use this system to edit wild mosquito populations, rendering them incapable of hosting malaria, dengue, and other diseases (CHIKV?).
Short Wyss Institute video on mosquito editing here:
https://www.youtube.com/watch?v=Cy69C6vnFCQ
and background on CRISPR/Cas9 here:
https://www.youtube.com/watch?v=2pp17E4E-O8
CRISPR/Cas9 is also featured in the December issue of Scientific American, where it made it into their list of ten "World Changing Ideas".

If a more radical step was taken to make mosquitoes give birth to all males, for example, we could in fact now "eradicate mosquitoes", although ethics boards would never green light such a project. Personally, I wouldn't mourn their passing, and bats mostly eat larger insects that are easier to echolocate, but other potentially serious ecological side effects could occur that would be hard to predict.

We live in interesting times...

All the best,

Kevin

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