Host Parasite Interaction - BIO214 Infectious Disease

Flashcards covering key definitions and concepts related to Host-Parasite Interactions, Pathogenicity, Virulence, Disease Progression, Microbial Mechanisms of Disease, and Coevolution from BIO214 Infectious Disease lecture notes.

Host-Parasite Interaction

A complex and dynamic relationship where parasites and hosts continually adapt to each other over time, impacting host populations, community interactions, and ecosystem functioning.

Opportunists

Organisms, such as commensals, which become pathogenic under certain conditions.

Pathogenicity

The ability of a microorganism to cause disease.

Virulence

The degree of pathogenicity, which can vary significantly even within the same species of pathogen.

Lethal Dose 50 (LD50)

The number of cells of a microorganism required to cause death in 50% of an infected population, often used to measure virulence experimentally.

Infectious Dose 50 (ID50)

The number of cells of a microorganism required to cause disease in 50% of an infected population, often used to measure virulence experimentally.

Natural History of Disease Timeline

A timeline depicting the stages of disease, including susceptibility, subclinical disease, clinical disease, and recovery, disability, or death.

Acute infection

An infection characterized by a rapid onset, short duration, and typically a high peak of virus production, such as with rhinovirus or influenza.

Persistent infection

An infection where the pathogen remains in the host for an extended period, potentially leading to chronic disease or death.

Latent, reactivating infection

An infection where the pathogen enters a dormant state within the host and can periodically reactivate, such as with herpes simplex virus.

Slow virus infection

An infection with a prolonged incubation period, gradually progressing over time, exemplified by measles virus SSPE or HIV.

Animate reservoirs

Living sources of infection, including humans (patients or carriers), animals, and insects.

Inanimate reservoirs

Non-living sources of infection, such as soil, water, and other objects.

Virulence Factors (Bacterial)

Mechanisms or components that allow bacteria to cause disease, including capsules, cell wall components (e.g., M protein), fimbriae, enzymes, antigenic variations, and biofilm formation.

Biofilm

A community of microorganisms encased in an extracellular polymeric substance, which can enhance bacterial pathogenicity by providing protection, facilitating nutrient acquisition, and aiding in host damage.

Exotoxins

Proteins produced inside pathogenic bacteria (most commonly gram-positive) during growth and metabolism, then secreted to damage host cells.

Endotoxins

Lipid portions of lipopolysaccharides (LPS), specifically lipid A, found in the outer membrane of gram-negative bacteria, released when bacteria die and lyse to cause host damage.

Cytopathic effects (CPE)

Visible signs of viral infections on host cells, which can include stopping mitosis, cell lysis, formation of inclusion bodies, cell fusion, antigenic changes, chromosomal changes, and transformation.

Mycotoxin

A toxic secondary metabolite produced by fungi that can cause illness in humans and animals.

Resistance (to infection)

The host's ability to limit the burden or growth of a pathogen.

Tolerance (to infection)

The host's ability to limit the health impact or damage caused by a given pathogen burden, even if the pathogen load is high.

Microevolution

Small, random genetic changes (anagenesis) that occur over generations, slowly driving speciation or extinction.

Coevolution

The process where two or more species reciprocally affect each other's evolution, often seen in host-parasite relationships where adaptations in one drive adaptations in the other.

Red Queen Dynamics

A theory suggesting that coevolution between hosts and parasites drives a constant evolutionary 'arms race,' where both continuously adapt to maintain their relative fitness, leading to fluctuating allele frequencies.

Host jumping

The ability of a pathogen, such as the influenza virus, to infect and adapt to different host species (e.g., birds, pigs, humans), often leading to new disease outbreaks.

Antigenic drift

Minor changes in the genes for the Hemagglutinin (HA) and Neuraminidase (NA) surface antigens of influenza viruses due to point mutations, leading to new strains that can evade existing host immunity and cause periodic epidemics.

Antigenic shift

Abrupt, major change in the HA or NA antigens of influenza A viruses, typically through gene reassortment between different virus strains, resulting in a completely new subtype that can cause pandemics.