E. BIOLOGY
BIOLOGY
One of the best-studied leeches is the European medicinal leech, H. medicinalis and its biology and epidemiology will be discussed below.
They are amphibious animals, living usually in stagnant or slowly running fresh water with littoral vegetation. Leeches swim free in the water, with an undulating motion.
Each specimen of this leech is protandrous hermaphrodite and tends to cross-fertilize with another leech of the same species. Eggs (10-30) are deposited after being embedded in a cocoon, which are deposited in shady and humid places. Newborn leeches feed on plankton, young specimens on fish, frogs and toads whereas older leeches feed on the blood of warm-blooded animals [5,6].
Leeches are very sensitive to vibration and heat, then when a host animal such as a human enters water, they swim towards it and attach to exposed areas of the skin.
In the digestive tract of the leeches (and so in their environment) there are symbiotic bacteria such as Aeromonas hydrophila, A. veronii, and A. sobria, which are aiding in the digestion of the blood meal, providing essential nutrients such as Vitamin B and they produce antibiotics which prevent colonization by other potentially harmful microorganisms (See Prophylaxis).