Biology 12 Unit 4: Infectious Disease Agent Summary

A complete set of vocabulary flashcards covering the eight types of infectious disease agents, their modes of transmission, life cycles, and impacts on hosts as detailed in the Unit 4 lecture notes.

Influenza

An RNA virus with three strains (A, B, and C) that infects the respiratory system and replicates via lytic stages in epithelial cells.

Antigenic drift and antigenic shift

Processes by which the Influenza virus undergoes genetic changes, with the latter potentially resulting in disease outbreaks.

Lysis

The process where a host cell ruptures to release viral particles to infect other cells.

Ross River virus

An Alphavirus (RNA virus) transmitted by female mosquito vectors from marsupial reservoirs to humans.

Vector

An organism that transmits a pathogen from one organism to another, such as the female mosquito transmitting Ross River virus or Malaria.

Reservoir

A host, such as a marsupial for Ross River virus, that allows a virus to replicate and persist in the environment.

Sacbrood

A foodborne viral disease of honeybees where the virus replicates inside larvae, killing them and turning them black.

Varroa mite

A vector for honeybee viral diseases, such as Deformed wing virus, that can be asymptomatic or cause physical deformities in adult bees.

Amphibian chytrid fungus disease

Also known as Chytridiomycosis, a disease caused by motile zoospores that penetrate frog skin and disrupt the keratin layer, respiration, and osmosis.

Motile zoospores

The infective stage of Chytrid fungus and Phytophthora dieback that can swim through water or soil to reach a host.

Mycobacterium Tuberculosis

The bacterium responsible for Tuberculosis, which enters the lungs and reproduces by binary fission in the alveoli.

Tubercle

A structure formed in the lungs where macrophages contain the Tuberculosis pathogen, resulting in a latent, non-contagious infection.

BCG Vaccination

A preventative treatment administered to groups susceptible to Tuberculosis.

Agrobacterium tumefaciens

A bacterium that causes Crown gall by incorporating its plasmid DNA into host plant DNA, leading to uncontrolled cell division.

Crown gall

A tumor-like growth on plant crowns, roots, or stems that can interrupt the transpiration stream by blocking xylem and phloem.

Phytophthora dieback

A protist disease caused by zoospores that invade plant vascular tissue, causing the host to die from the crown downwards.

Mycelium mat

A network of threads grown by Phytophthora in or on plant roots that produces sporangia and chlamydospores.

Chlamydospores

Asexually produced structures of Phytophthora that allow the pathogen to survive unfavourable environmental conditions.

Plasmodium

A genus of protists, featuring six species, that causes Malaria in humans.

Sporozoites

The form of the Malaria pathogen transmitted from the salivary glands of a mosquito to the human bloodstream.

Merozoites

The stage of Plasmodium that forms in the liver and invades red blood cells, eventually causing them to rupture.

Gametocytes

Haploid stages of Plasmodium produced in the human host which are taken up by mosquitoes for sexual fertilisation.

Definitive host

The host in which the sexual phase of a parasite's life cycle occurs, such as the mosquito for Malaria.

Intermediate host

The host in which the asexual phase of a parasite's life cycle occurs, such as the human for Malaria.

Incubation period

The time between exposure to a pathogen and the appearance of symptoms, ranging from $1-2$ days for Influenza to $9-14$ days for symptomatic Malaria.