Could a fly bite land you in hospital?
MOST of us swat away flies out of annoyance rather than fear, but some can be dangerous — even in the UK.
Last week it emerged that a bite — thought to be from a deer fly — put Lord Allen Bathurst, 55, a friend of Prince Charles, in hospital for four months with multiple organ failure. He’d developed sepsis (where the immune system goes into overdrive in response to an infection) as a result of the bite.
In theory, any insect bite could lead to sepsis, but it’s very rare, says Dr James Logan, an associate professor of medical entomology at the London School of Hygiene and Tropical Medicine. Here, we look at how different flies can affect your health.
DEER FLIES
ABOUT 1cm long, these have gold or green eyes and brown bodies with darker spots.
‘Their mouths cut through the skin with a saw-like action,’ says Dr Logan. They tend to feed off cattle, horses and deer, and can be found in places such as Richmond Park.
HEALTH HAZARD: They’re not usually dangerous, except that they carry animal faeces and bacteria in their mouths which can enter the bloodstream, says Dr Logan.
Despite the rare risk of sepsis, it is most likely your immune system will simply react to the saliva and the bite will result in a welt.
BLANDFORD FLIES
ALSO known as black flies, these are 5mm long and often mistaken for midges. ‘They live near running water — streams, brooks and even water features,’ says Dr Logan.
They are named after a Dorset town of the same name, where many people were bitten by the flies in the Sixties and Seventies. Peak time for bites is May and June.
HEALTH HAZARD: Victims, who are usually bitten on the leg, report a short, stabbing pain as the fly’s saliva enters.
The flies bite with scissor-like mouth parts which form a pool of blood on which they feed. The bites can cause swelling and joint pain, as the body releases histamine, and sometimes a high temperature.
HORSE FLIES
THESE are related to deer flies, but larger (up to 3cm long). They are mostly dark brown with a metallic sheen and dark eyes. Commonly found around water, including marshland and rivers, they die off in winter.
HEALTH HAZARD: Horse flies are well known for their painful bite — the females have jagged jaws that rip a hole in the flesh.
Signs of infection are a rash, pus, swelling and weakness. In rare cases people develop anaphylaxis, a life-threatening allergic reaction. Some deaths have been reported.
HOUSE FLIES AND BLOW FLIES
HOUSE flies are black, hairy and 5 to 8mm in length. They live off foods and human and animal waste. Meanwhile the blow fly (also called a blue or greenbottle) is 10 to 15mm long, has a green or blue body and red eyes.
‘Blow flies can cause myiasis [infestation by maggots], a problem for animals and humans, because maggots feed on flesh,’ says Dr Logan.
HEALTH HAZARD: Although they don’t bite, both house flies and blow flies can spread diseases — in the UK this typically means diarrhoea-type illnesses.