All examples of host-parasitism so far mentioned in Part II showed how infecting microorganisms encounter the body, humoral and cellular factors of defense mechanisms in a sequential time course. Due to these multifaceted defense mechanisms, only a relatively small number of microbial species equipped with a full set of virulence factors (Part I) succeed in producing lethal infectious disease in the host animals who do not have any genetic or temporary deficiency in some part of their defensive mechanisms. Here, “genetic deficiencies” are caused not only by mutations in the nucleotide base sequences of the chromosomal DNA resulting in the hereditary disease, e.g., sickle cell anemia, agammaglobulinemia, but also by the abnormalities in the number or structure of the chromosome, e.g., Downs or Turner’s syndrome. In contrast, “temporary deficiencies” means the incapability to synthesize enough of the constituent factors to maintain a healthy state of homeostasis. The representative cause of such temporary deficiencies are malnutrition, severe fatigue or exhaustion from overwork or mental stress, or combinations with other diseases, including those of an infectious nature. Therefore, temporary deficiencies can be overcome by the removal of causes in their reversible stages.
KeywordsVirulence Factor Sickle Cell Anemia Microbial Species Host Organism Severe Fatigue
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