Parasites in the Human Body: Human Skin Parasites

Skin parasites are small organisms that generally bite the human skin and feed, leaving the host with a powerful itch, a biting sensation and red swellings. Scratching these swellings is not a great idea, as it prolongs their duration (from about two weeks to about two months) and can cause infection from the bacteria that lie underneath the human fingernails.

There are multiple skin parasites and they are not particularly friendly. The most common ones are: mites, lice, ticks, fleas and flies.

In this article on parasites in the human body we will look at lice and ticks; how they infect, what problems they cause and how to treat such an infection.

The reason why these 0.5 - 0.8 mm invertebrates love us is because they literally can't live without us. If they are removed from the human host, they die in a couple of days due to an absence of food. Their food is exclusively the human blood, which they suck by biting the skin and secreting saliva. Lice are very mobile and they move rapidly. The eggs (called nits) are laid by the female on the root of the hair and because they are attached to the hair with a special saliva, they are hard to remove without special products. A mature female can lay up to six eggs a day and the eggs mature in 8 to 18 days.

There are two body lice species that can infest the human skin :

- The Pediculus hominis, which has 2 subspecies: the head lice and the body lice (Pediculus hominis capitis and Pediculul hominis corporis). The head and body lice are anatomically identical though the head louse is smaller in size.

- The Phthrius pubis (the pubian hair louse).

Both species use their three pairs of legs to attach themselves closely to the human skin.

The head lice look for the warmer regions of the head: behind the ears, the lateral sides of the head and neck, the occipital region. They cause severe itchiness (especially during the night-time).

Body lice can be found on the hems and seams of clothes where they lay their eggs. They can live between skin and clothes and besides causing itchiness, they also "come with" secondary infections. Their bite can be spotted by the presence of a 2-4 mm red papule (swelling).

The pubian louse can be asymptomatic for up to 30 days and if not treated can lead to inguinal inflammations and infections. They can spread using the abdominal or torso hair, and can also be found in the beard or the eye-lashes.

Lice are removed from the human skin using special products and a special comb.

The tick is the most dangerous human skin parasite and overall is one of the most dangerous human parasites.

Before maturing, a tick first goes through a larval and then a nymph stage. When crossing to another stage of its life, a tick needs food. That food is usually obtained from a mammal, humans included. While feeding, ticks can become contaminated, thus transmitting a virus or a bacteria to the human host.

Lyme disease is one of the most encountered diseases that a tick can carry. There is an efficient treatment, but it needs to be applied shortly after the contamination. There is no preventive treatments for this disease. Meningeal-encephalitis, a disease that can also be caused by ticks, is a viral disease with no cure. It attacks the central nervous system, and even though it is not deadly, it affects the nervous system in 40% of the cases.

Ticks are widely encountered, but predominantly in Central and Eastern Europe and Asia.The risk period is March - October.

Wearing clothes that cover the whole body during nature walks is a good preventative measure. Also, after returning from such a walk, a close inspection of the body (especially the knees and elbows) is recommended. Ticks can't be removed with a shower or a hot bath. Use special instruments, such as fine-pointed tweezers or a special tick removal tool. Care has to be taken to remove the tick to make sure its head is still not on the skin. Do not use oily products to remove a tick since this will stress it and cause it to further feed, thus increasing the risk of an infection.