Host Parasite Interactions

A small organism which lives within or upon a larger organism of a different species at whose expense it obtains some advantage

The larger organism that is parasitized

Entrance, mulitplication, and colonization of a host--need not cause disease and may be "normal flora"

The agent that causes disease

The disease producing organism

A parasite that ordinarily does not cause disease. Occurs in compromised host

Sequence of Infection (4)

Period prior to the development of symptoms (days to weeks)

The very first symptoms of an infection

Symptoms when disease is fully manifest

Shortly after eradication of an infection

The method for entry of the pathogen into the body

First and most important step in infection. Involves contact with a mucosal cell surface molecule (receptor). Involves specificity, antagonism, and synergy

Study of how a disease is transmitted (geographical distribution, animal reservoirs, season occurence)

Routes of Transmission (5)

True or False:
Adherence molecules extend from bacterial surface as lipoteichoic acid, proteins, and carbohydrates
True False

Degree of virulence is measured by (3)

Smallest dose that will result in death of the host

Dose that kills 50% of infected hosts

Dose that infects 50% of treated hosts

Ability to cause disease

Ability to invade tissues and multiply

Antibody with phagocytosis and killing of pathogen

Cell-mediated immunity

Mechanisms to avoid host defenses by extracellular bacterial pathogens

B cells produce specific antibodies (with Th2 cells) that _____ bacteria

______ can also opsonize bacteria

Phagocytosis can happen via (3)

These parasites require an intracellular environment. Examples include rickettsia, chlamydia, and viruses

These parasites grow intracellularly or on artificial media. Examples include mycobacteria, salmonella, brucella, legionnaire's disease, & listeria

How do intracellular pathogens avoid host defenses?

Secreted from bacterial cells into the surrounding medium

Neurotoxin producing flaccid paralysis

Neurotoxin producing spastic paralysis

Causes cells of the body to produce large amounts of cytokines

Enterotoxin--activates adenyl cyclase

Part of the cell wall of Gram-negative bacteria. Activates macrophages causing them to make IL-1, TNF-alpha, and IL-6. Fever, hypotension, DIC. Lethal shock can occur

The number of cases or incidence of a specific notifiable disease per unit population

The number of deaths due to a specific notifiable disease per unit population