Fleas and lice
Dog flea Ctenocephalides canis
Fleas generally have a body that is flattened laterally and rear legs modified for hopping that give the animals an astounding range. The colouration of these insects is brownish to black. The adults live as bloodsuckers on humans, other mammals and birds. The eggs are laid at random in the vicinity of host animals. The thread-shaped, grub-like larvae grow to a length of approx. 5 mm and live in dust and wastes where they feed there on organic material. Most fleas are not dependent on the blood of a single host animal, but rather have a primary host and several secondary hosts. Domestic animals are usually responsible for bringing fleas into contact with humans. The dog flea has a body length of 1.5 to 3 mm. Its primary hosts are domestic dogs, foxes and wolves; secondary hosts include humans, domestic cats and domestic rabbits.
Fleas cause painful bites in humans and domestic animals that itch unpleasantly. The bites are often in a row pattern with sampling prior to the full blood meal. Various flea species have been responsible for the epidemic plagues of the past in their function as transmitters of the bubonic plague pathogen from rats to humans. Fleas can also transmit tapeworms to dogs and cats when they are bitten and swallowed by these pets.
Cat flea Ctenocephalides felis
The cat flea is has become the most frequent flea plague pest. Its primary host is the domestic cat; secondary hosts include domestic dogs, humans and rats. The adult insects grow to a length of 1.5 to 3.2 mm. For further general information on the biology of this species see under dog flea.
The damage caused by this species is the same as described under dog flea.
Human flea Pulex irritans
This flea species has become relatively rare. It can develop on humans even when no primary host animal is present. The primary hosts in Europe are domestic dogs, foxes and badgers; secondary hosts include humans, domestic cats, domestic pigs and hedgehogs. The body length of the human flea can reach 2 to 4 mm. For further general information on the biology of this species see under dog flea.
The damage caused by this species is the same as described under dog flea. Next to the plague flea (Xenopsylla cheopsis), the human flea was a principle vector of the bubonic plague epidemics of earlier centuries.
Head louse Pediculus capitis
Female head lice are up to 3.5 mm long, the males somewhat smaller. These flightless insects have clip-like legs that enable them to crawl the length of hairs readily. Their colour is reddish to dark grey. They are well adapted to the surface temperature of skin (optimum: 27 to 30°C), feed exclusively on blood, which they must suck several times a day. The females glue their eggs, which are approx. 0.8 mm long (nits) tightly to the hair shaft base. The entire development cycle from egg to adult takes approx. 3 weeks.
Head lice infestations are very unpleasant. The saliva that gets into the scalp during the biting and sucking processes causes pronounced itching. Local skin reactions such as reddening or urticaria. Scratching often allows bacteria to enter the wounds, which can then lead to large areas of eczematous inflammation. Lice are usually transmitted in direct human-to-human contact or via sharing of hats, caps, scarves, combs, brushes, towels, beds and items of clothing.
In case of head louse infestation, countermeasures should be taken immediately using products available in pharmacies and drugstores.
Book louse Trogium pulsatorium and other species
Dust and book lice are harmless insects approx. 1 to 2 mm long that crawl about in a lively manner and have nothing in common with bloodsucking head lice. They are found only in rooms with high humidity levels. Their colour varies from pale yellow to dark. They feed on hardly visible fungal cell sheets that grow in excessively moist environments.
In rooms with high humidity levels, book and dust lice cause damage to paper goods, e.g. books, files and wallpaper, when they scrape off the invisible fungal cells sheets that are their food. Fine paper dust is created in the process. These animals are often found in large numbers in stale foods and herbal drugs stored under excessively moist conditions in storage cabinets. Mass outbreaks are common in freshly wallpapered rooms in new, and insufficiently dried, buildings.
These harmless insects depend on high humidity levels and are therefore relatively easy to control by means of proper heating and ventilation.