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.
Crab or pubic louse
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.
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:
avoid long grass and vegetation and keep pets from these areas;
remove vegetation near your property;
keep away host animals such as squirrels, mice, rats and other rodents, and deer. Deer carry ticks that carry Lyme disease;
use an insect repellent such as DEET, which will repel ticks also;
tuck trousers/pants into boots or socks to prevent ticks climbing onto your skin;
do a daily body check if out in areas with ticks; and
wear light clothing so that ticks are easy to spot.
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:
Wear gloves or using a cloth or tissue to prevent catching an infection from contact with the tick;
Use a pair of fine-tipped tweezers or commercial tick removal tool;
Grab the tick as close as possible to the skin, to include the mouth parts if possible;
Gently pull the tick straight out until the mouth parts are removed;
Wash your hands with soap and water;
Clean the bite area with soap and water or an antiseptic; and
Seek medical attention if you cannot remove all of the tick from the skin.
twist the tick — this can break off the mouth parts and leave them in the skin;
use any substance, such as alcohol, gels, ointment or petroleum jelly to try and make the tick drop off as this could make the tick regurgitate into the bite and cause infection;
use a flame, which could also make the tick regurgitate, carrying diseases into the skin;
scratch the bite because this will increase the risk of infection and cause further swelling.
Ticks can carry a variety of viruses, bacteria and protozoa, including several at the same time, which can make diagnosis and treatment difficult.
Tick borne encephalitis
Rocky Mountain Spotted Fever
Colorado Tick Fever
Australian paralysis tick
Crimean-Congo haemorrhagic fever
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.