It’s (almost) impossible to avoid mosquito bites if you live in the tropics

Well…mosquito borne infections have been back in the mainstream news for the past few months, in particular, Zika virus infection. What has captivated us all about Zika virus is it’s apparent association with birth defects, particularly microcephaly (an abnormally small head usually resulting in brain damage). Anything that disproportionately targets pregnant woman and their unborn babies is going to hit a raw nerve with the general public. More recently, there have been reports of Guillain-Barre syndrome (paralysis from damage to the nerves) in patients following suspected Zika virus infection. Last week’s blog entry actually explained how syndromes such as Guillain-Barre can occur when the immune system works to well in response to some infections.

This week, I am going to jump back onto the Zika virus bandwagon. My first post about Zika virus 3 weeks ago, answered the 7 most common questions about the virus. In the current post, I will share with you my thoughts on whether or not pregnant women should visit areas with active Zika virus transmission, and the recent CDC travel advisory regarding such travel. I also want to share with you the real challenges persons living in the tropics face, in trying to avoid mosquito bites, and give recommendations for avoiding these bites.

Because of the potential grave complications of Zika virus infection in unborn babies, the CDC has issued a travel advisory for pregnant women. Essentially, the recommendation is, pregnant women in any trimester should consider postponing travel to areas where Zika virus transmission is ongoing. Pregnant women who must travel to one of these areas should talk to their doctor or other healthcare professional first, and strictly follow steps to avoid mosquito bites during the trip. The advisory stated further, women trying to become pregnant should consult with their healthcare professional before traveling to these areas and strictly follow steps to prevent mosquito bites during the trip.

Do I agree with the CDC advisory? Well, in medicine, my philosophy has been to assume the worst until I have all the facts, particularly for situations where lack of vigilance can result in devastating consequences. So yes, I agree with the advisory. However, for me personally, if I was pregnant or trying to become pregnant, I would completely avoid travel to areas with ongoing Zika virus transmission, unless it was an absolute emergency. This would be until we have all the facts about any link between the virus and fetal malformation.

Why would I completely avoid travel to such areas? Well, because I am from the tropics (specifically the Caribbean island of Antigua) I know that it’s just about impossible to completely avoid mosquito bites in these regions. Mosquitos are some of the smartest pests I have come across. They have a variety of ways to find humans, including detecting our smell (some body odors are more attractive to them than others), body heat, and carbon dioxide emission, which is probably why they love to buzz around the head and neck area.

There are different modalities to prevent mosquito bites, including killing them, repelling them, setting up barriers against them, and preventing mosquito breeding.

1 – Killing Often in the tropics, mosquitos are vanquished by squashing them between the palms of the hands, or by using a hand to squash them on the body after they land and attempt to bite. But mosquitos are very quick so you have to act fast and use a good amount of force. Otherwise, the next thing you know, the apparently fallen mosquito “shakes it off” and is off flying to find the next target, which of course could be you again! There are devices that look like mini tennis rackets which employ mild electric current to electrocute and kill mosquitos on contact. These are popular in some places. Probably the best way to kill mosquitos is to spray the entire house with an insecticide while the windows are closed and leave it for at least an hour or two, until the insecticide dissipates.

2 – Repelling There are a variety of insect repellants available, the classic recommendation being to use one with at least 20% DEET (example, OFF!). There are also repellants containing natural ingredients such as eucalyptus and citronella. The problem with insect repellant in general is that it gets diluted by sweat, and one must remember to apply it at least every 2 hours or more frequently with heavy sweating. Mosquitos are so smart, that if you missed putting repellant on one spot of your body, they will bite you right there. If you miss your ears, they will bite you there. I have even gotten a mosquito bite on my lip! That occurred while sleeping, but it just goes to show you how aggressive mosquitos are.

3 – Barriers Mosquito barriers include gauze screens on windows, and mosquito nets. Mosquito nets were common when I was growing up in the early 80s but for some reason people stopped using them, at least in the Caribbean. That is probably because it became more standard for houses to be built with gauze screens on the windows to prevent entry of mosquitos and other pests into the house. But, as I said, mosquitos are very smart – they would hang out on the veranda, conveniently just outside the door so that as soon as the door is opened, they zoom right in.

Another mosquito barrier is simply wearing long clothing to cover arms and legs. However, this may not be all that feasible, when the temperature is approaching 90 degrees. Additionally, if clothing is too thin, mosquitos can actually bite you through the clothing. Spraying clothing with insect repellant can prevent this from happening. Mosquito nets can also be sprayed with insect repellent, to decrease the chance of a mosquito finding that one hole in the net. Believe me, if there is one small hole, they will find it!

4 – Eliminating breeding grounds Mosquitos need water to breed, and mind you, these are picky, domesticated insects, so they like clean water. That is why the hang around human dwellings. In the Caribbean, and I am sure in many other developing countries in tropical regions, the public water supply can be unreliable and so most homes have tanks or sometimes drums to store water for backup. If these water supplies are not adequately covered, mosquitos can get inside and lay their eggs in the water. If not a physical cover, oil poured over the water creates an effective barrier to prevent the mosquitos laying their eggs.

So…….there you have it, the ways to minimize mosquito bites. For someone visiting for a short period, especially if they are staying in a hotel with air conditioning (mosquitos don’t like the cold), their chance of being bitten and infected by a mosquito, is probably lower than for a local person who is there all the time. However most visitors to the islands will visit the beach at least once, and mosquitos are even more plentiful in coastal regions. Many visitors are so focused on the perfect tan, they forget about preventing mosquito bites.

Insect repellants are much more affordable in developed countries so it is no big deal for visitors to bring their supplies. In the Caribbean, after all the duties and taxes are added on, OFF! for example, is rather expensive. The herbal repellants (eucalyptus, citronella) tend to be more affordable. However no one uses repellent every day, and when used, application certainly does not occur every 2 hours. That is just reality, especially when you are working or otherwise occupied.

Talking about working, not all workplaces are air-conditioned buildings, given the very high energy costs. Some offices don’t even have screens on the windows. So even though you optimize your home, you may be at risk for being infected at work. I remember as an intern in Jamaica, I contracted Dengue fever from being bitten by mosquitos at work!. There were always a lot of mosquitos hiding out under the desk at the nurses station.

Though Zika virus is likely to spread widely, including to warmer parts of the United States and other first world countries, the burden of disease is likely to be greatest in underdeveloped and developing countries, for the reasons alluded to above. So, yes, it’s easy for reproductive aged women like me, living in a developed country, to avoid travel to areas where there is Zika virus transmission. But what are women living in the heart of an outbreak region to do? I certainly think it’s unrealistic to expect them to delay pregnancy. We haven’t been able to prevent sexually transmitted infections such as HIV.

Talking about sexually transmitted infections, just this week there was an article in The New York Times describing possible sexual transmission of Zika virus. Just when we thought the plot couldn’t get any thicker…

All of us are patiently awaiting results of investigations into the possible link between Zika virus infection and the birth defect, microcephaly. If a link is found, then major mosquito eradication campaigns will have to be instituted, and governments will likely have to subsidize insect repellants, mosquito nets, and the like. These actions will hopefully be temporary, until a vaccine is developed, or even better, mosquitos are rendered non-infectious, through some genetic modification. Hopefully, no link is found between Zika virus and microcephaly. The virus will then be dismissed as one of the many viral germs which cause a mild, self limited illness, in the 20% of persons who do get sick after being infected.