Chapter 29 Flashcards
What is a well adapted pathogen
one that lives in balance with its host
What are chronic infections
host and pathogen survive
Three steps of an acute infection
- short term infection
- rapid and dramatic onset of disease
- host returns to good health
Stages of a disease
- Infection: organism invades and colonizes host
- Incubation period: time between infection & onset of symptoms
- acute period: the disease at height, overt symptoms present
- Decline period: disease symptoms subsiding
- Convalescent period: patient returns to normal state
Difference between mortality and morbidity
mortality: incidence of death in a population
morbidity: incidences of diseases in a population that includes both fatal and nonfatal diseases.
Worldwide deaths due to infectious diseases
- Respiratory: 31% (bacteria, viruses, fungi)
- Diarrheal diseases 15% (bacteria virus)
- AIDS 13% (virus)
- Tuberculosis 15% bacterium
- Malaria 6% (protist)
…
Others 11%
What is the myxoma virus
Biocontrol of rabbits in Australia
Steps of host-to-host transmission
- Virulence diminishes
- Resistance of host increases
- Pathogen extinction may occur if host killed before transmission
- if no host to host transmission, pathogen may remain virulent
What is herd immuinity
Resistance of a group to infection due to immunity of a high proportion of the group
What happens in herd immunity
immunized people protect nonimmunized and pathogen cannot be passed on
Common themes of all modes
- escape from host
- travel
- entry into new host
Major mneans of human infectious diseases transmission
- person to person: direct contact (hand shake, sex), indirect contact (watercup), airborne droplets (sneeze cough)
- Vehicle: (borne to all) water, food, air, soil
- Vector: arthopods/insects (lyme disease, malaria)
What is transmission facilitated by and what are the they?
Agents:
living agents: vectors
nonliving: vehicles and formites
What is zoonosis
disease primarily infection animals
occasionally transmitted to humans
know the cycles of host infection
know the cycles of host infection
Steps of schistosomiasis
- Embryonated eggs each with a fully developed miracidium are passed in feces
- snail host ingests eggs, miracidia emerge from eggs and penetrate the snail intestine
- cercariae released from snail
- cercariae penetrate the skin of fresh brackish water fish
- host becomes infection by ingesting undercooked fish contain metacercariae
- metacercariae exyst in the small intestine
- adult in small intestine
Eggs developed for miracidia
sporocysts -> rediae -> cercariae
what are common source epidemics
usually from water and food contamination
cholera