Clinical Notes : Dermatology

200. Horsefly Bite

Identification

Male and Female

Reaction to bite

Treatment

- References -

- CPD Quiz -

Identification

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

The females​

• 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.

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Other symptoms may include ​:

• dizziness, weakness

• nausea

• urticaria, wheezing, angioedema

Treatment.

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General :

• 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

Pain :

• paracetamol and ibuprofen

• avoid aspirin in under 16 year old

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Itch :

• crotamiton cream or lotion

• hydrocortisone cream or ointment

• antihistamine tablets

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Swelling :

• cold compress or ice pack for 10 minutes spells

• antihistamine tablets

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Infection :

• 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

NHS

Updated: Jan. 2020

Access

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Horsefly bite treatment: Three ways to soothe the wound recommended by the NHS

Andrews L

Expess, online Feb. 2020

Access

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Are horsefliy bites on the rise ?

Natural History Museum

Online February 2020

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What to do about a horsefly bite

Medical News Today

Online Feb. 2020

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Horsefly bites! What you need to know.

Warson Training Services

Online, Feb. 2020

Access

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An insight into the sialome of the horse fly, Tabanus bromius

Ribeiro JMC, Kazimirova M, Takac P,  Andersen JF, Francischetti IMB

PMC

Published online 2015 Sep 11

Access

Horseflies are present countrywide but are a particular nuisance in Co. Kerry and Cork.

CPD Quiz and Certificate

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