Opportunistic Agents, Man

Opportunistic infectious agents do not cause obvious symptoms by their presence in immunocompetent individuals, but can proliferate into fulminant infections in immunodeficient or immunocompromised hosts.

Immune suppression reactions have increased recently worldwide in humans and animals. This occurs not only due to spreading of virus transmission (inclusive HIV), but also as a result of increasing use of drugs (e.g., cortisone) with immune-decreasing side effects. This deficiency of the immune system enables a broad series of agents – including viruses, bacteria, fungi and parasites – to reproduce in a much higher degree than it occurs under normal (i.e., immunocompetent) conditions. Such infections are due to the fact that opportunistic agents – especially the parasites Pneumocystis carinii, Cryptosporidium species and Toxoplasma gondii are the three main reasons for deaths in AIDS-patients. The most common parasites from the recently enlarging group of opportunistic agents are...