Amongst other things, infection with parasites lowers the resistance of the host animal, and this in turn can cause susceptibility to disease. The term 'parasite' usually causes any keeper to think of worms. Ticks, mites, protozoa and worms can indirectly or directly result in the death of a tortoise. As this is a very comprehensive subject, we will deal now with internal parasites only. Protozoa are a complete one celled living organism that are only visible under a microscope, whereas worms are often visible to the naked eye.
Internal parasites harm their hosts in many ways.
Some suck blood and others destroy body cells. Excessive parasitic loads can lead to obstructions in the intestine, bile ducts and blood vessels. Some parasites can produce toxic substances and cause allergic reactions. Heavy parasitic loads can cause stress and suppress the immune system - opening the door to a wide variety of infectious bacteria. Heavy infections can also affect the fertility level of eggs and thus reproduction.