Preventing and Treating Insect Bites

Biting insects feed on humans and animals by piercing skin to tap into a blood vessel. They actively seek a food source by using their various senses such as heat, smell and sight to find a suitable host. Some insects make a quick feed and leave while others prefer to find hidden areas of the body to stay till they are gorged and can only drop off when they are swollen with blood.

Whichever way they find a host and feed, however, biting insects can cause itching, inflammation, painful welts and in addition can transmit many serious diseases that affect millions of people across the world.

Mites

Mites are are closely related to ticks. There are nearly 50,000 known species, mostly microscopic, occupying a very diverse range of habitats. Many are pests of plants and animals such as bees and birds, but very few affect humans.

The house dust mite does not feed directly on humans but on shed skin particles and pet dander. The shed skins and faeces can cause allergic reactions in some people, similar to hay fever, asthma and eczema.

Scabies

The scabies mite, Sarcoptes scabiei, is a parasitic mite about 0.5mm long that burrows into the outer layer of skin to feed on skin cells. It lays 10-25 eggs that hatch and emerge from the skin after 3-4 days to travel to another part of the body and repeat the cycle.

The infection results in itching caused by the body’s reaction to secretions from the mites. This can take up to eight weeks to appear.

Scabies is highly contagious. People living in the same household are likely to become infected easily.

The most common treatments for scabies are the pesticides permethrin, malathion and lindane. However, these can have side effects and should be used with advice from a medical professional.

Rickettsialpox

Rickettsialpox is caused by the bacteria Rickettsia akari, which can be carried by house-mouse mites. They will seek new hosts, including humans, when the mice die off naturally or as a result of pest control. Infection is transmitted by the bite of the mite.

Rickettsialpox is regarded as a mild disease that takes 2-3 weeks to recover from. The first symptom is a bump around the bite that appears about a week after the bite, which turns into black crusty scab.

The mouth parts of a female mosquito

Legend:
a — antennae
c — compound eye
lb — labium
lr — labrum
md — mandibles
mx — maxillae
hp — hypopharynx

Source: Wikimedia commons: Xavier Vázquez.

Reactions to bites

People’s reactions to bites can vary greatly depending on the sensitivity of their immune system and whether they have been bitten before.

It can take hours or days for itching or redness to occur after being bitten, making it difficult to tell what bit you. In this case you will need other identifying factors to tell the source of the bite.

Mosquitoes

There are over 3,500 known species of mosquito worldwide and a large number of these transmit diseases that affect more than 700 million people each year, causing at least two million deaths.

Female v. male mosquitoes

Only the female mosquitoes need a blood meal, having the specialised mouth parts that can penetrate animal skin, though they can also feed on sweet plant juices.

Male mosquito mouth parts are adapted only to feed on nectar and plant juices and cannot penetrate skin. It is the females that transmit diseases to humans and animals.

The female mosquito finds a host by sensing carbon dioxide in breath, perspiration and body odours, and tends to feed in the evening and night time, though there are notable exceptions.

Mosquito bites

Mosquito bites are characterised by itchy red bumps on the skin, with varying degrees of swelling, depending on the person’s immune response.

How to prevent mosquito bites:

• Cover skin: wear long sleeves, trousers, footwear and hats.
• Avoid bright colours: bright colours attract mosquitoes.
• Avoid strong scents: strong scents such as perfumes and deodorants attract mosquitoes; Use insect repellents: use gels and sprays containing DEET or other repellent for applying to exposed skin; lighting insect repellent coils or citronella candles can help keep mosquitoes away from an area;
• Avoid areas with still water: mosquitoes breed in slow moving or still/stagnant water, so removing these from around the home — even small containers — will reduce mosquito numbers by preventing their breeding.
• Avoid vegetation: Avoid areas with dense vegetation where mosquitoes congregate.
• Use mosquito nets for sleeping: when in remote or undeveloped areas these are a proven way to prevent bites while sleeping and they can also be impregnated with insecticide to kill the mosquitoes as they land on the net.

How to treat mosquito bites

Mosquito bites can be treated with some simple measures:

1. Clean the bite area with soap and water: this is the most important treatment for a mosquito bite.
2. Use a cold compress: swelling can be reduced immediately after a bite by covering it with a cold compress such as ice in a cloth (but do not hold ice directly on the skin).
3. Take anti-histamines: itchiness and swelling can be relieved with antihistamine creams. Oral anti-histamine can also help if you have multiple bites.
4. Do not scratch: avoid scratching as this will increase the itching and could lead to the bite becoming infected.

Mosquito borne diseases

One of the main concerns around mosquito bites, is their ability to spread the following diseases:

• Malaria
• Dengue
• Chikunguya
• Yellow Fever
• Zika virus disease
• Lymphatic filariasis/ elephantiasis

Find more information on insect-borne diseases.

Flies

Midges and gnats

The term midge and gnat is a very general term for a wide range of flies, including the Sand fly and Black fly. Most are aquatic during the larval stage.

Biting Flies

It is important to note that not all flies bite, some go about their day to day lives without the need to feast on humans. However there are a few fly species which rely on our blood to survive, these are:

• Sandfly
• Blackfly
• Horse fly
• Highland midge

How to treat fly bites

1. Wash the bite with soap and warm water.
2. Use and apply either antiseptic cream or spray to the area after washing.
3. Apply ice to the bite for 15 minutes, several times a day.
4. Avoid scratching so you don’t break the skin and cause and infection.

The bites of some flies such as horse flies can bleed. In this case a simple plaster applied after the bite has been washed would help. If the bleeding doesn’t stop on its own, you should see a doctor.

How to prevent fly bites

• Avoid outdoor activities during the day when flies are more prevalent.
• Cover up - wear long sleeves when outside.
• Use an insect repellent before going outside.
• Empty out bins, and clean dirty cups and plates regularly - flies are attracted to decaying matter.
• Install window and door screens to keep flies out.

Moths

Out of an estimated 160,000 species of moth there is only one genus, Calyptra, that can bite animals to drink their blood.

There are around 19 species of the moth, which are commonly called vampire moths, but just one species is known to have the ability to pierce human skin: Calyptra thalictri.

Unlike mosquitoes, only the male moth is known to have the ability to drink blood.

There are few reports of the moth biting humans and the only known case of the moth drinking human blood was in a test by the Russian scientist Vladimir Kononenko in 1999.

This species is native to areas as disparate as Thailand, the Urals and southern Europe.

In 2007 several newspapers reported recordings in Finland and later in Sweden. It is not thought to pose any risk to humans.