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What are external parasites?
External parasites are insects that require blood to survive.
For questions related to external parasites such as bed bugs, you can contact the housing health advisory service.
Identification marks
Adult: 5–8 mm
The adult common bed bug is a wide, flat and brownish insect. Bedbugs that have not fed for a long time are quite light in colour.
The larvae stage of the common bedbug is quite similar to the adult insect, but they are smaller and lighter in colour.
Occurrence
The common bed bug is one of the best known external parasites in apartments.
The common bed bug requires one meal for each of its five exuviations. The common bedbug feeds on a sleeping human and is most active around one hour before dawn.
The common bed bug moves around during the night. During the day, they hide in the cracks of furniture, behind paintings, in the seams of mattresses or in the frame of a spring mattress, for example. They leave dark spots of excrement on the lower surfaces of beds and bed legs, as well as bloody spots on the sheets.
Damage
The sharp sucker of the common bed bug has a separate spout and sucking ducts, which means that they do not spread disease carriers as easily as the castor bean tick, for example. The common bed bug sprays saliva into humans, which at first has a slight numbing effect, but afterwards, causes itching and swelling for most people.
Prevention and extermination
If you detect common bedbugs in your apartment, immediately contact your building manager to start an extermination process carried out by professionals.
Do not carry out the extermination by yourself, as pesticides intended for consumer use do not have any effect on common bed bugs. They will only drive them deeper into their hiding places or even into neighbouring apartments. In addition, they may also become immune to the pesticide, which means that the substances used by professionals will also have less impact.
The common bed bug can also move into neighbouring apartments through holes in the walls or ceiling. You must therefore contact the property manager immediately if you discover or suspect bed bugs in your apartment.
Identification marks
Adult: 2.5–3 mm
A fully grown louse has no wings. It is quite a flat parasite that is either whitish or grey in colour.
Occurrence
The head louse (Pediculus humanus capitis) only lives in hair. It attaches its eggs, less than a millimetre long, onto the base of the hair.
It spreads easily through headwear, brushes and combs. They can also spread directly from head to head in close contact, for example, when taking group selfies. Lice can also be transmitted through seats covered with fabric on public transport or in theatres, for example. Without human heat, adult lice usually perish in a few days, and their eggs in about ten days.
The body louse (Pediculus humanus corporis) lives in clothing. They lay their eggs into the seams of clothing.
The crab louse (Phthirus pubis) lives in human hair, especially in pubic hair. It spreads through sexual contact, for example, but it may also spread through bedclothes, towels or brushes used in a sauna.
Damage
The head louse is not known to spread any diseases, but the body louse may spread typhus or relapsing fever. Crab louse infection causes severe itching, a rash and hair loss. Lice can cause skin infections.
Prevention and extermination
The applied treatments are shampoos or solutions sold in pharmacies. Treat all those living in the same household. If necessary, contact your health care centre.
Clean all premises thoroughly. Also vacuum the mattress and bed and wash the bedclothes at a minimum of 60 °C. Throw out the dust bag after vacuuming. Headwear should be stored in the sleeves of jackets instead of on the hat rack.
If you find occurrences of body lice, contact your local health care centre. Clean the premises thoroughly, vacuum the mattress and bed, and dispose of the dust bag after vacuuming. Dispose of contaminated textiles or wash them at 60 °C. Contact the property manager who will order a professional to perform the extermination.
Substances for exterminating pubic lice can be obtained from a pharmacy without a prescription.
More information
Ticks are arachnids. They are small, and many are microscopic. The habits of mites and ticks vary, and they dwell on land, as well as in salt and fresh water.
Red poultry mite
(Dermanyssus gallinae)
Identification marks
Adult: 0.6–1 mm
The red poultry mite is dark and red after sucking blood.
Occurrence
The red poultry mite is a common chicken parasite in henhouses, but it may also use other host animals. A red poultry mite can crawl into an apartment from birds’ nests on the building. It can survive for 4 to 5 months without blood.
Damage
The red poultry mites may bite people, but they cannot reproduce on human blood, and they do not live on human skin.
Prevention and extermination
Prevent birds nesting on your building. Remove all nests after the birds have left and spray the area with pesticide aerosol.
Itch mite
(Sarcoptes scabiei)
Fully grown mite: at most, 0.3 mm (not seen with a naked eye)
Occurrence
Spreads through skin contact but can survive in bed clothes for 2 to 3 days. The male mainly lives on the skin. The female punctures the skin and digs tunnels through it in which it lays its eggs. Most commonly found between the fingers, in bends of arms and legs, and on the chest and shoulders. A human itch mite can also take a dog as its host.
Damage
Itch mites cause strong itching of the skin and water filled vesicles, red spots and mite tunnels, which often become infected with pus-causing bacteria.
Prevention and extermination
Wash or heat-treat clothing. Use pharmacy products to care for your skin. Treat all those living in the same household.
Identification marks
Adult: 1–6 mm
Larva: 2–3 mm
Fleas are shiny, wingless insects that live in the nests of mammals and birds. They are usually quite black in colour and have flat sides. Fleas move around by jumping.
The larvae are usually white and have no legs.
Many animals have their own species of fleas. A flea of a specific host animal may try to feed on other animals or humans. The larvae live in the host animal’s nest and feed on organic waste.
The human flea (Pulex irritans) is occasionally encountered in Finland. Cat fleas are rarely seen, but dog fleas have not been observed in Finland for decades. Fleas from birds or squirrels can suck blood from humans as well.
The chicken flea (Ceratophyllus gallinae) is common in bird nests and can easily spread to humans. Up to 2,000 fleas can spread from one bird’s nest every year, and then spread onto cats and dogs from vegetation and be carried indoors by them.
Damage
A flea bite results in a reddish bump, which itches. Cortisone and antihistamine lotions are used to treat the bites if necessary.
Prevention and extermination
Birdhouses should be cleaned during the winter before the fleas hatch from their cocoons in the spring. Any waste from the birdhouse should be burned.
Identification marks
Adult: 5 mm
A city or sewer mosquito resembles an ordinary mosquito or a forest mosquito. The feeding female’s back body is aligned with the skin surface, and the end of its back body is usually blunt-shaped. The jaw filaments are short.
Occurrence
The city mosquito thrives in places where the water is left standing for a long time, such as in gutters and flowerpots. They come into apartments through windows, air ventilation channels and floor drains.
Damage
The mosquito bites during the night, causing lumps which may become irritated.
Prevention and extermination
It is recommended to install mosquito nets on windows and air ventilation channels to prevent mosquitoes getting into the house. Pour enough hot water into floor drains to change the water in the seal. In the evening, you can spray a suitable pesticide into the floor drain.