Host-pathogen interaction

The host-pathogen interaction is defined as how microbes or viruses sustain themselves within host organisms on a molecular, cellular, organismal or population level. This term is most commonly used to refer to disease-causing microorganisms although they may not cause illness in all hosts. Because of this, the definition has been expanded to how known pathogens survive within their host, whether they cause disease or not.

On the molecular and cellular level, microbes can infect the host and divide rapidly, causing disease by being there and causing a homeostatic imbalance in the body, or by secreting toxins which cause symptoms to appear. Viruses can also infect the host with virulent DNA, which can affect normal cell processes (transcription, translation, etc.), protein folding, or evading the immune response.

One of the first pathogens observed by scientists was Vibrio cholera, described in detail by Filippo Pacini in 1854. His initial findings were just drawings of the bacteria, but up until 1880, he published many other papers concerning the bacteria. He described how it causes diarrhea as well as developed effective treatments against it. Most of these findings went unnoticed until Robert Koch rediscovered the organism in 1884 and linked it to the disease.Giardia lamblia was also discovered by Leeuwenhoeck in the 1600s, but it wasn’t found to be pathogenic until the 1970s, when an EPA sponsored symposium was held following a large outbreak in Oregon involving the bacteria. Since then, many other organisms have been identified as pathogens, such as H. pylori and E. coli, which have allowed scientists to develop antibiotics to combat these harmful microorganisms.

Pathogens include bacteria, fungi and viruses. Each of these different types of organisms can then be further classified as a pathogen based on its mode of transmission. This includes the following: food borne, airborne, waterborne, blood borne, and vector-borne. Many pathogenic bacteria, such as Staphylococcus aureusand Clostridium botulinum are food borne pathogens that secrete toxins into the host to cause symptoms. HIV and Hepatitis B are viral infections caused by blood borne pathogens, and Aspergillis is the most common pathogenic fungi that secretes aflatoxin which acts as a carcinogen and contaminates many foods, especially those grown underground (nuts, potatoes, etc.).

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