April Showers Bring May Flowers...And Mosquito Bites
April is here, and the weather thus far has been delightfully mild. We all know “April showers bring May flowers.” Unfortunately, those showers leave small puddles of water in our ditches, buckets left in the sand box, and in the oddest places like hollowed spaces in trees. These seemingly harmless collections of water are a breeding ground for the most deadly organism on earth, the mosquito.
Yes, you read that correctly. The mosquito is the deadliest organism on earth because it is the vector for a number of diseases such as malaria, Eastern Equine Encephalitis, St. Louis encephalitis, Japanese encephalitis, yellow fever, dengue, West Nile virus, Zika virus, and my personal favorite, chikungunya. Thankfully, in the US of A most of these diseases are rare due to excellent mosquito control measures by public health agencies. However, these things are still annoying little critters which can ruin your barbecue or birthday party.
Ædes ægypti, Ædes albopictus, Anopheles quadrimaculatus, and Culex quinquefasciatus are the scientific names of four common mosquitoes which plague our area. (Don’t the names just sound annoying? And sinister?) They all need stagnant water to breed and go through a complicated life cycle which is not relevant to this discussion. What is relevant is that in order for many mosquitoes to be able to produce eggs, they need to have components found in blood. This can be from any animal: reptiles, fish, cats, dogs, birds, horses, and humans. This is where we come into the picture.
What exactly attracts mosquitoes to people in order to siphon off a small amount of blood from them? There are a number of factors which contribute to this: type O blood, heavy breathers, those with a lot of skin bacteria, people with a lot of body heat, children, and the pregnant. A person’s attractiveness to mosquitoes also has a heritable, genetically-controlled component. That’s all interesting, but how does a mosquito locate someone?
Female mosquitos hunt their hosts by sight and by detecting compounds such as carbon dioxide, octenol, and nonaldehyde. The last compound is found in perfumes. They also are able to detect chemicals in perspiration. They prefer some people to others because frankly, some people’s sweat smells better to them than others. So when we say your child smells sweeter to the mosquito, we are really only half joking.
Mosquitos are crepuscular critters. In other words, they hunt for hosts in twilight (dusk and dawn). During the heat of the day they prefer to hang out in cool areas and only bite if they are disturbed. Otherwise they wait until evening to resume their hunt.
The female mosquito basically has a hypodermic needle for a nose. This is called her proboscis. When she bites someone, she injects her proboscis into the skin and releases a little saliva which is an anticoagulant and sucks out a small amount of blood. (She spits in your skin. Yuck.) It is this saliva which is the means of spreading disease. It’s also the cause of the itching. The saliva causes histamine to be released which produces a red, itchy bump called a wheal to form. This histamine is meant to destroy the proteins left by the saliva. Most of the time this wheal forms immediately, but occasionally it may take hours to a few days to show up.
Once a mosquito bites you there are options to deal with the itching. Antihistamines orally such as Benadryl, Claritin, Zyrtec, Allegra, and Xyzal will help with the itching. Topical Benadryl is also effective. Topical steroid treatments like 1% hydrocortisone cream and triamcinolone cream are another option. Before using any of these it would be best to consult with one of our physicians as to which is best for your child. Even with no treatment, the itching resolves within a few hours. (This was an actual experiment I performed in a medical entomology class in college. We weren’t allowed to scratch the itch. Worst 2 hours of my life!)
As with so much in healthcare, an ounce of prevention is worth a pound of cure. Here are some ways to prevent the mosquito from ruining your outdoor activities. First, remove sources of stagnant water. Empty old buckets, tire swings, and any other source of standing water that you see. Second, wear clothing which covers as much exposed skin as possible. While this helps, it may not prevent all bites. Third, insect repellents. The most effective are those which contain DEET, but DEET in high concentrations can cause problems in children, so get a product such as Off Family or Off Skintastic. These have a much lower concentration of DEET, generally less that 10%. Parents should apply the repellent. Children should never apply insect repellents themselves. Oil of lemon eucalyptus is quite effective. And finally, citronella is also an effective repellent, although it lasts for a shorter time than others. Fourth, if you are camping be sure to use mosquito netting to keep those pests out of your tent.
Finally, mosquito borne disease in our area is not very common due to excellent mosquito control measures. What we mostly deal with are complications from scratching, like impetigo. If the wheal becomes very red or covered with a crust that looks like dried honey, we should examine your child in the office. However unlikely, if your child has mosquito bites and suddenly develops fever, body aches, headache, and stiff neck, it is imperative that we see them right away.
So hopefully now you are bettered armed to fight these annoying pests. Enjoy the mild weather with fun outdoor activities. Just take the precautions which have been discussed and you will keep the mosquitoes at bay.
Fun fact: In Iberville Parish, Louisiana there is a town called Maringouin. This is the Cajun French word for a large swamp mosquito.
Leaves of 3, Seriously...Let It Be
The mild days of spring have arrived after a rather brutal winter for southeast Louisiana. I mean, seriously, it snowed twice this past winter! What’s up with that?! But I digress. The trees have returned to their verdant splendor, the grass is beginning to grow to the point of needing to be mowed, and lurking back in the corner of your yard, there it is. Toxicodendron radicans. The dreaded poison ivy. (Poison ivy fun fact: it’s not really an ivy. It is in the same family of plants as cashews and pistachios.) Here is a little info about this nasty little vine/bush that may help you to avoid a nasty rash, or to help you deal with it if it happens.
Poison ivy causes what we doctors call urushiol-induced contact dermatitis. It actually can be caused by a number of Toxicodendron plants. In the eastern USA it is most commonly poison ivy or poison sumac. In the western USA it is most commonly poison oak (although there is an eastern poison oak as well). The causative agent in all of the plants is an oil called urushiol. Urushiol actually causes changes in the protein arrangement in your skin cells such that your immune system thinks they are foreign bodies which need to be destroyed. This is a type IV hypersensitivity reaction or a delayed hypersensitivity reaction. This means that the reaction is not like the reaction you get with a bee sting or with pollen. It usually is delayed by 48-72 hours from exposure to the urushiol.
The rash associated with poison ivy affects over 350,000 Americans every year. Interestingly, 15%-30% of people won’t have any response to the urushiol. For those who do develop the rash the response varies from mild to severe. The rash is red and raised and may have small vesicles to large blisters. It is intensely itchy. It is NOT contagious and you cannot spread it on your body by scratching. The liquid that forms in the blisters does not contain urushiol, so that isn’t a source of spread. If you have developed the rash in various places on your body you can be assured that the urushiol touched you in that location. You CAN get the rash from urushiol which is on your dog’s fur, on your clothing, or on any other object which has touched the poison ivy plant.
Poison ivy is a self-limited condition and will typically resolve on its own within 14 days. That’s little comfort to the person who is itching to the point of near madness. Lucky for him there are some treatment options.
So what do you do if you are exposed? First, DON’T PANIC. (Just kidding. Who panics from poison ivy exposure?) The best thing to do is wash the skin with soap and water immediately. If the urushiol is removed it won’t cause the rash. You should also wash clothing, toys, gardening tools, and anything else that has come in contact with the plant, and that includes Fido. If you develop the rash it is too late for this as the urushiol is very well and quickly absorbed into the skin. Once the rash develops topical treatments such as 1% hydrocortisone cream, zinc oxide, and calamine lotion can help alleviate the itching. Colloidal oatmeal and baking soda added to bathwater may also help some with itching. If the rash is extensive or with significant facial involvement, injections with corticosteroids or oral corticosteroids may be needed. These will require a visit to the doctor. Nota bene, Benadryl and other antihistamines may not help much since the reaction is not mediated by histamine but is cellular mediated. Occasionally scratching will lead to secondary infections which require antibiotics. If the vesicles or blisters become filled with pus, it would be best to have them checked by one of our doctors.
Your mom and them always say an ounce of prevention is worth a pound of cure. This goes for poison ivy as well. The best way to prevent poison ivy is to avoid contact with it. Poison ivy and poison oak are either vines or shrubs which have leaves in clusters of three. Poison ivy vines are also covered with tiny roots which give it a hairy appearance. The leaves of both of these plants go from light green in spring, to darker green in summer, to red in autumn. Even leaves that have fallen from the vines are capable of causing the dermatitis. Poison sumac looks different. It is a shrub or tree with 7 or more leaves arranged on either side of the stem. Of the three plants producing urushiol, sumac is probably the most potent. Here are some little sayings which will help you know what you should avoid:
Leaflets three; let it be!
Berries white, run in fright!
(and my favorite) Hairy vine, no friend of mine.
Better yet, here is a photo:
or in real life:
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