Internal Parasites Ebook
Like the majority of animals, the wombat is host to several internal parasites such as worms of various kinds. Most of these, if present in small numbers, apparently do the animal little or no harm. Thick white roundworms are common in the colon of the wombat, and smaller roundworms have been found in the walls of the small intestine and in various organs, such as the lungs. Several harmless species of tapeworms are occasionally present in the intestines, but the wombat is not a host for hydatid cysts.
About 2 billion years ago, probably in a shallow laguna, bacteria encountered for the first time malicious shapeless little eukaryotes eating them. Some heterotrophic eukaryotic cells started a new business in life and became predators, whereas bacteria faced a new challenge, not to fall prey. The prototype of a phagocyte, an amoeba that feeds on bacteria, was probably the first to impose on bacteria the selection pressure to maintain or evolve new genes that facilitate survival within the predators (Figure 1.3). Today, still, amoebal creatures roam the world in search of bacterial prey. One of them, Hartmanella, is a notorious settler in cooling water systems and showerheads, an opportunistic human parasite itself, and one of the natural hosts for the human pathogen Legionella pneumophila (Chapter 18). The slime mold, Dictyostelium discoideum, has become a prime model organism for the study of some intracellular pathogens such as Mycobacterium marinum, M. avium and L. pneumophila...
That reveal key host-parasite associations and adaptive virulence mechanisms 23 . Due to the acquisition of several plant genes, such as ATP ADP translocases, by members of the Chlamydiaceae family, these organisms have been hypothesized to have originally shared a symbiotic relationship with plants, later becoming parasites of humans and animals through evolution 3 . As human parasites, chlamydiae acquired eukaryotic domains and genes, such as the actin-dependent regulator of chromatin (SWIB) domain 3 , aminoacyl-tRNA synthetase genes 30 and ATP ADP translocase genes 3, 73 , to facilitate their in vivo lifestyle.
While the same trend should be creating new human predators as well as human parasites, the successful evolution of an efficient new human predator is a long-term, and ultimately futile, process as soon as we humans get wind of any evolutionary change putting ourselves, and especially our children, in harm's way, we will institute immediate and surely successful eradication efforts. Killing new parasites, however, is a far more difficult endeavor, especially those of very small size, such as microbial forms. It is in this arena that some of the most interesting and fecund new species of the coming biota may be found.