Every year, we get reports from Undercurrent subscribers
about how swarms of no-see-ums hampered shore diving, cut
beachside bar time short, and left them with a vacation souvenir
of nasty bites, bumps and welts. In some cases, reactions
to the bites have kept divers out of the water.
The Bay Islands in Honduras are the worst. John and
Marilyn Walker (Castro Valley, CA) were there last May,
staying at Fantasy Island, and were frequently bit, even
indoors. “The island in general features many biting insects,
but even though we sprayed with DEET and slept with the
air conditioner on, we still got red, itchy welts,” they wrote.
Christopher Mohr (Dublin, OH), who also stayed at
Fantasy Island, was amazed how intense and determined they
were in their hunt for human blood. “They were bad unless
you covered yourself with insect repellant. The bites were still
on us almost a week after we returned home. The resort was
diligent in spraying, which helped, but these insects are worth
paying attention to -- they can be a problem.”
They’re a problem nearly everywhere in the Caribbean,
and I can attest to that. While lying on a beach in the
Bahamas, I got 147 bites, which ruined a day of diving. On
the Honduran island of Guanaja, they chewed me up again,
leaving 60 marks on me while I waited for a 7:30 a.m. flight. Regardless of where you are in the Caribbean, chances are
you’ll get a few bites.
The no-see-um obviously gets its name because it is
nearly invisible, small enough to go through window
screens. The ones coming at me on the Utila beach were
little black dots the size of a period, flying down at me like
a miniature fleet of Luftwaffe. The scientific name for the
no-see-um is Ceratopogonidae, but it has accumulated more
common names, including sand flea, sand fly, biting midge and
punky. They’re common to wet areas like beaches, wetlands
and creeks. Divers will experience them at their worst in
Honduras, Nicaragua, Belize and Mexico’s southern coasts. Many resorts spray their grounds but can’t get them all
– besides the Fantasy Island reports we mentioned above,
Belize’s Isla Marisol resort is also a big breeding ground. And of course like any blight, no-see-ums breed like crazy. They lay eggs in standing water, where larvae hatch and
feed on dead vegetation. Within just a few days, the larva
becomes a pupa, then an adult that leaves the nest in search
of food.
Though one-third the size of a mosquito, its bite is
inversely more painful. While mosquito bites cause raised
lumps on the skin that become very itchy, they can be
soothed with calomine lotion, Benadryl, or aloe vera. No-seeum
bites result in typically a whole bunch of red welts that
irritate the skin, are slow to deflate, and cause three to four
days of severe itching. No-see-ums on the beach will bite
most often on the ankles and lower legs, just because they’re
closer to the ground. But if you’re unlucky enough to pass
through a dark swarm of them, no part of your body is off
limits and they could fly into your eyes, ears, nose or mouth.
Every person reacts differently to no-see-um bites. Two
people may receive an equal number of bites, and one will
not be affected while the other will turn into a walking
pincushion. For divers who suffer allergic reactions, one
treatment of antihistamines may work for one person, while
another may need a bigger, stronger dose of something
more potent.
Bigger Than Its Bite
At times, a no-see-um bite can lead to something far
worse than a red welt and uncomfortable dive days. A few
years ago, we reported the story of Undercurrent readers
Barry Lipman and Ingrid Preuss and their no-see-umplagued
visit to Guanaja. The bugs ruined a beach picnic
when Lipman received several hundred bites and had to flee
the beach. That night, he developed a 102-degree fever and
discovered that he was covered with little itching bumps. A six-day course of prednisone alleviated his symptoms and
allowed him to continue diving, but Preuss was not as lucky. Four months after the trip, she developed small, reddish
blemishes on her face at the locations of some no-see-um
bites. A dermatologist diagnosed it as cystic acne, but the
blemishes grew into ulcerated lesions. It took Preuss a trip to
Curaçao to visit specialists in order to get an accurate diagnosis:
leishmaniasis.
Not every type of no-see-um carries the disease. Scientists
have found the culprits to be no-see-ums of the genuses
Phlebotomus, typically found in Asia and Africa, and Lutzomya,
found in Latin America and the Caribbean. Like mosquitoes,
gestating female no-see-ums hungry for protein search
for a “blood meal,” and in the process can transmit one of
the twenty-plus species of protozoan parasites responsible
for the disease. Lipman was told that the fever and rash he
developed in Guanaja the night after receiving hundreds of
no-see-um bites were not the result of leishmaniasis but a
reaction to the toxins he received from the bites themselves. Multiple no-see-um bites can also cause death by kidney
failure from their toxins alone, without any other infectious
agent involved.
While leishmaniasis affects 12 million people in 88 countries
(with two million new infections annually), most of the
high-risk areas are not dive destinations. However, leishmaniasis
is well-entrenched in Mexico, Honduras, Belize and
other parts of Central America. It also appears to be spreading
to some islands in the Caribbean, including Trinidad and Hispaniola. Elsewhere, Thailand and Egypt have also
reported cases.
Though leishmaniasis accounts for less than five percent
of the tropical infections American travelers return with each
year, unless the victim consults a physician specializing in
tropical medicine, diagnosis is often inaccurate. The disease
itself is difficult to cure and victims are prone to recurrences. For decades antimony (sodium stibogluconate) has been considered
the most effective treatment, but the three-week intravenous
regimen is toxic in itself, and the parasite is reportedly
becoming resistant in some areas. Other treatments are
available but no cure is 100 percent effective, and there are
currently no preventative medications or vaccines.
Signs of leishmaniasis are sores that change in size and
appearance over time. They often end up looking somewhat
like a volcano, with a raised edge and central crater. Some
sores are covered by a scab and can be painless or painful. Some people also have swollen glands near the sores (for
example, under the arm if the sores are on the arm or hand). If you fear persistent sores are signaling leishmaniasis, ask for
a referral to a tropical medicine specialist or contact the U.S. Centers for Disease Control (www.cdc.gov), which can help
clinicians with biopsies and cultures, and recommend and
provide medication.
You Can’t Beat DEET
Fortunately, the chances are slim that you’ll die from a nosee-
um bite, but if you are a person who experiences strong reactions to bee stings or mosquito bites, chances are you’ll
also react strongly to these.
The first line of defense is dousing yourself with insect
repellents containing at least 30 percent DEET. Some divers
report success with cactus juice, a repellant sold in Roatan
that comes in a brown bottle and smells like Citronella or
Avon’s Skin-So-Soft, although Consumer Reports recently
found the latter offered no protection at all against the aedes
mosquito, an aggressive species that can carry dengue fever. Most likely, the people who found these questionable remedies
helpful wouldn’t be prone to attacks anyhow.
A more aggressive measure is applying concentrated
doses of DEET. Generally, the higher concentration of the
chemical DEET, the more effective the repellent. Consumer
Reports’ top-rated Deep Woods Off with 98 percent DEET
kept the aedes away for 12 hours. Products with 30 to 34 percent
DEET protected for at least five hours, while those with
seven percent DEET lasted only an hour against the aedes.
The CDC recently recommended two other active ingredients
to fight bites. One is picardin, which is odorless and
non-greasy. Consumer Reports recommends Cutter Advanced,
which prevents bites for two to three hours for aggressive
species, eight hours for less so. Another is oil of lemon eucalyptus,
which the CDC says is as effective as DEET. Consumer
Reports tested Repel Lemon Eucalyptus spray against another
repellent containing 10 percent DEET and found that Repel
prevented bites for four to seven hours for aggressive mosquito
species, and more than 12 hours for less aggressive
mosquitoes, longer than the DEET repellant and picardin.
DEET Plus Sunscreen a No-No
While it’s safe to apply it regularly over a two-week
vacation, don’t use it with sunscreen. Recent studies using
animal and human skin cells suggest the mixture might
increase DEET absorption but might not make sunscreen
not protect as well. About 20 versions of sunscreen-bug repellent
combinations are sold, but because the Food and Drug
Administration regulates sunscreen and the Environmental
Protection Agency regulates insect repellant, guidance for
using these combo products is in limbo since they don’t really
belong to either agency. Complicating the issue, Canadian
researchers recently tested human skin cells and found questions
beyond the all-in-one products: Spraying on DEET and
then rubbing on sunscreen actually increased DEET absorption
the most.
Be alert when you’re sitting at the outdoors bar for your
post-dive drinks – no-see-ums wake up when the sun goes
down and are most active at dawn and dusk. If possible, wear
long-sleeved shirts, long pants and socks. Make them lightcolored
and avoid dark or bright colors. Thoroughly spraying
clothing and fine-mesh screens and bed nets with permethrin
will give added protection (also dry them thoroughly before
use). Aerosol insecticides can also be used in rooms to clear
them of pests.
The most effective way to fend off no-see-ums is to take
a liveaboard trip, but the odds of bringing home anything
worse than itchy welts are too small to require a change of
dive travel plans. Still, it makes sense to take aggressive steps
to avoid becoming the main course for these biting bugs.
-- Ben Davison