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.
Bites itch because your body reacts to the saliva injected by the insect while it is biting you.
Biting insects have a complex mouth structure that varies between species. It can include a needle-like part that pierces the skin and other parts that are serrated and saw through the flesh to find a blood vessel.
They also have a food canal to suck up blood and a canal that injects saliva containing anticoagulant and anaesthetic. The anticoagulant keeps the blood liquid to keep it flowing and the anaesthetic stops you from feeling the bite so you don’t disturb the feeding insect.
The body’s immune system recognises the foreign material injected into the bite and produces histamine as a defence mechanism. This causes localised inflammation and itching.
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 (link)
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.
Fleas are wingless insects that are about 3-4mm long when adult. They are very agile and especially good at jumping.
As a ratio of their size, fleas are one of the longest jumpers of any animal. They can quickly spread widely once inside a building.
There are several types of flea that affect humans, pets and animals and are common in the human environment. They tend to prefer a particular animal host, but will still bite to see if the host is suitable before dropping off.
Common animals that can bring fleas into contact with humans include:
Flea bites look alot like other insect bites, but there are, however, a few key characteristics which separate them apart.
How to identify flea bites:
How to treat flea bites:
Getting bitten by a flea can also lead to contracting some harmful diseases.
Diseases you can catch from fleas:
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.
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 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:
How to treat mosquito bites
Mosquito bites can be treated with some simple measures:
One of the main concerns around mosquito bites, is their ability to spread the following diseases:
You are most likely to pick up bed bugs from a hotel, where they can crawl into luggage and clothing. They can also catch a ride in bedding and furniture and spread through buildings by crawling through holes in walls, such as for electrical wiring, or along pipe work.
Bed bugs tend to feed at night but will search for a host at any time if they are starved. They find a host through an array of sensors that can detect warmth, carbon dioxide and body odours.
Bed bugs feed for only 5-10 minutes until they become engorged with blood, if not disturbed and may spend less than 20 minutes on a host. After feeding, they return to their shelter.
How to spot bed bug bites
How to treat bed bug bites
Bed bugs do not carry diseases so the only treatment needed is to stop itching and rarely for inflammation. If the bites develop into very itchy bumps, general products available from a pharmacy to stop itching are suitable. For inflammation it is best to see a doctor who can prescribe the most suitable treatment. Many people do not react to bed bug bites so do not need any treatment.
How to prevent bed bug bites
If you are worried about bringing back bed bugs from your travels, then follow these steps to prevent bed bugs from entering your home and feeding upon you at night:
Worried about bed bugs in your hotel or dorm? Follow these steps to prevent them from biting your guests:
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.
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:
How to treat fly bites
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
The head louse, or nit, is a single species of small wingless insect, Pediculus humanus capitis, which feeds only on human blood and has its complete life cycle on the human scalp.
Lice cannot jump or fly but can crawl from person to person in close contact. Head lice commonly affect children, but anyone with hair can catch them.
Head lice are considered harmless as they are not known to carry any disease and are regarded more as a cosmetic problem. They do cause itching of the scalp and secondary infections can result from scratching.
Detecting head lice
They are commonly found in the hair behind the ears and at the nape of the neck.
The remains of the white egg cases can also be seen attached to hairs.
The lice can be combed out of the hair onto a piece of white paper using a special nit comb that has very closely-spaced teeth to trap the lice.
Treating head lice
Repeated use of a nit comb can remove the lice, but larger infestation may only be effectively removed with medicated shampoos or lotions available from pharmacies. These contain insecticide so should be used carefully, especially on children.
The body louse (Pediculus humanus humanus) is indistinguishable from the head louse, but lives mainly in clothing, so the two types do not interbreed under normal conditions.
They are thought to have evolved from head lice around 100,000 years ago, which is about the time when humans invented clothing.
Prevention and treatment is to wash infected clothing at high temperature or destroy it.
The body louse can spread the rickettisal diseases Epidemic typhus (Rickettsia prowazekii) and Murine typhus (Rickettsia typhi). Epidemic typhus has been responsible for millions of deaths throughout history especially in time of war among soldiers and prisoners.
How Typhus spreads
The louse picks up the disease by feeding on an infected person then when moving to another person excretes the organism in its faeces. The bacteria infect the host through the bite wound when the faeces and squashed lice are rubbed over the skin. It can also be inhaled in air-borne particles or enter the body rough the mucous membranes of the mouth and eyes.
The body louse was the principle means of the spread of the bacteria B. Quintana, the cause of trench fever during the First World War. It infected a large proportion of troops on both sides. In recent times it has been recorded worldwide: in Europe, North America, Africa, and China. Other biting insects can also spread the disease.
The crab louse (Pthirus pubis) feeds exclusively on blood and is only found on humans. It is distinct from the other two types of human louse in appearance, having a rounder and shorter body. It is usually found in pubic hair or other coarse hair such as eye lashes, beards and moustaches. It is mainly spread by close contact, sexual activity and shared use of towels, clothing and beds.
The Triatomine bug carries the protozoan, Trypanosoma cruzi, which causes Chagas disease, also called American trypanosomiasis.
It is classified by WHO as a neglected tropical disease, with 8 million people infected worldwide and an estimated 10,000 deaths caused by complications from the disease.
There are 150 species of the bug and more than 100 species of mammal carry the parasite, so it is considered impossible to completely eradicate the disease.
Nymphs and adult of the triatomine bug Rhodnius prolixus
Source: Wikimedia Commons: Thierry Heger (link)
Originally a rural disease, socioeconomic changes, deforestation, rural migration and urbanisation have resulted in Chagas disease spreading more widely, according to WHO, and it is increasingly being detected in countries where it is non-endemic.
Triatomine bugs bite exposed areas such as the face, but it is not the bite that transmits the disease. After feeding, the bug defecates, which carries the protozoan onto the skin.
When the person inadvertently wipes their skin this can carry the protozoan into the bite, other broken skin, or the eyes and mouth.
Both the male and female adults and nymphs are blood sucking and carry the parasite in their faeces.
The bugs live in cracks and crevices of poorly constructed homes, where they hide during daylight and emerge at night to feed. Fresh faeces contains live parasites, so infection can also occur after touching a place where they have defecated.
Spraying house interiors with insecticide, plastering walls to fill in hiding places, bed nets and hand hygiene are all effective means of control.
An adult bug and a nymph with clear defecation marks on the wall, in a house in Mexico
Source: WHO (Chagas disease campaign), Isaias Montilla
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 Malaysia, 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.
Arachnids are a separate Class from insects in the classification of the animal kingdom, distinguishable by their eight legs and two body sections: the abdomen and cepahlothorax.
The group is easily distinguished from insects, which have six legs, three body sections (head, thorax and abdomen) and one pair of antennae. They are both in the Arthropod phylum, however, which consists of animals having an exoskeleton.
The arachnids have many members that can be pests of humans: the ticks, mites, scorpions and spiders.
There are around 900 species of tick, all of which are parasites that feed on the blood of mammals, birds and less commonly reptiles and amphibians.
Ticks inhabit areas with long grass or heavy vegetation. They can sense a host by detecting breath, body odours, body heat, moisture and vibrations through a sensory organ in the first pair of legs.
Ticks do not seek a host but lie in wait, climbing up grass or onto the edge of leaves and hold up their front pair of legs to wait for a host to pass and latch onto — a posture called ‘questing’. They then crawl around the host looking for their preferred site to feed from, such as soft skin.
A tick on a blade of grass with forelegs extended in the questing position
Source: Wikimedia Commons: Mcvoorhis (link)
How to prevent tick bites
In areas of known infestation you can take some measures to reduce the chance of tick infestation:
It is important to remove a tick properly so that you do not leave mouth parts behind in the skin, squeeze body fluid into the bite or cause it to regurgitate into the bite, which will increase the chance of infection.
How to remove ticks:
Ticks can carry a variety of viruses, bacteria and protozoa, including several at the same time, which can make diagnosis and treatment difficult.
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.
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 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.
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