Clinical Notes : Dermatology
200. Horsefly Bite
The horsefly is a large, hairy fly whose bite can be extremely painful.
much larger than an average fly (1cm to 2.5cm)
dark, hairy, may also have brightly coloured patches or black and white back
generally found near to cattle, horse stables, ponds, pools, woodlands, and grassy areas
more prevalent during hot, sunny weather with low wind, and are more aggressive when thunder accompanies hot weather.
does not transmit any disease apart from swamp fever, which can be fatal in horses, mules, donkeys and zebras.
insect repellent (DEET) does not prevent horsefly bites
Male and female
will bite large mammals (humans, dogs, cows, horses) for blood, which they need to produce eggs.
anchors to the skin while drinking the blood with the help of small hooks along its mouthparts
have two razor sharp cutting blades that pierce the skin, causing a cut rather than a small puncture hole
releases substances that stop blood clotting at the point of skin puncture
the female fly then use a sponge-like part of their mouths to lap up blood.
will not leave behind any mouthpart or stinger when they bite people
Male flies do not bite instead drinking nectar from flowers or fruit.
Reaction to bite
Humans find horsefly bites painful.
Itch and some swelling is common.
Usually, a weal occurs around the site.
Other symptoms may include :
urticaria, wheezing, angioedema
clean site with mild soap and plain water with clean cloth or cotton wool
avoid scratching as this increases chance of infection
vinegar and bicarbonate of soda are unlikely to help
paracetamol and ibuprofen
avoid aspirin in under 16 year old
crotamiton cream or lotion
hydrocortisone cream or ointment
cold compress or ice pack for 10 minutes spells
mark edges of rash with pen to monitor increase in size
review red flags for infection and safetynet
standard anttibiotics for skin infection / cellulitis
Insect bites and stings
Updated: Jan. 2020
Horsefly bite treatment: Three ways to soothe the wound recommended by the NHS
Expess, online Feb. 2020
Are horsefliy bites on the rise ?
Natural History Museum
Online February 2020
What to do about a horsefly bite
Medical News Today
Online Feb. 2020
Horsefly bites! What you need to know.
Warson Training Services
Online, Feb. 2020
An insight into the sialome of the horse fly, Tabanus bromius
Ribeiro JMC, Kazimirova M, Takac P, Andersen JF, Francischetti IMB
Published online 2015 Sep 11
Horseflies are present countrywide but are a particular nuisance in Co. Kerry and Cork.
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