viral and bacterial infections Flashcards
what causes infectious diseases?
what is it the product of?
- microorganisms cause disorders which damage tissue or cause dysfunction
- product of interaction btwn agent and host
infectious disease is dependent upon… (5)
- intrinsic characteristics of agent
- mode of transmission
- unique characteristic of host
- host-agent relationship
- host responses to infection
characteristics of the agent (3)
interaction btwn agents and host…
what is disease a result of?
- interaction btwn agents and humans is cooperative and development of disease is the exception
- disease is the result of agent interference w/ function and integrity of host.
2 ways parasites can act and an example of each disease
certain parasites will produce disease (eg- myobacteria tuberculosis), others are facultative pathogens which can colonize, invade or both (eg candida albicans)
what is virulence? what is another name for virulence?
extent of interference of agent. a.k.a. pathogenicity
modes of transmission
horizontal (2)
vertical (2)
zoonotic (1)
- horiontal:
direct spread- exposure from sick individuals is characteristic of contagious disease (eg small and chicken pox, TBC.
indirect spread- exposure to contamindated water, food or soil (mycosis, histoplasmosis) - vertical:
prenatal (rubella)
perinatal (hep B) - zoontic transmission - animal to host (rabies, malaria)
characteristics of the host
-3 barriers to infection
- intact skin and mucosal surface and secretions
- phagocytotic cells at the site of entry
- immune system
when are host barriers effective? what happens when they are defective?
barriers or defense mechanisms are only effective when they are intact, if they are defective infectious agents will produce disease
just exposure to infectious agents is not necessarily sufficient, spread is determined by: (2)
- virulence of infectious agent
2. extent of host resistance
definitions of two host-agent relationships :
high virulence
low virulence
- high virulence- implies capability of agent to cause disease in normally resistant individuals
- low virulence- an agent which is only effective in host with low resistance (opportunistic infection)
pathogenicity factors-
dependent on 3 host-agents relationships…
2 characteristics of the agent
1 characteristics of the host
- ability to produce an infection and propagate w/i the host by overcoming host defenses
- agents ability to generate products that will result in tissue damage (ie toxins, lytic enzymes, etc)
- induction of host-cellular responses to the infectious agents can lead to tissue damage as well (hypersensitivity I- IV)
host responses to infection
(4 types of inflammation)
- exudative inflammation
- necrotizing inflammation
- chronic inflammation
- granulomatosis inflammation
viral infections characteristics (2)
capsid
latency definition
protein shell around virus
to propagate, each virus must do what?
- 4 stages of virus cycle
- attach to cell
- penetrate it
- un-coat
- replicate: DNA in nucleus and RNA in cytoplasm
how do viruses travel?
definition of viremia
- except for some respiratory viruses, virues probably travel via blood
- viremia- presence of virus in bloodstream
how do viruses cause disease?
how do viruses produce disease?
- viruses cause disease by killing the infected cells but in some cases disease can be produced w/o killing infected cells
- viruses produce disease by promoting the release of difference chemical mediators
viral infections- influenza
def
characterized by…
two distinct viruses that cause it…
- acute self-limited viral respiratory disease which is distributed worldwide and often occurs in widespread epidemics.
- characterized by fever, headache, myalgia, and prostration w/ bronchitis and bacterial pneumonia as common complications
- two distinct viruses cause the disease: influenza virus A and B- periodically undergo changes in antigenic composition making world population become newly susceptible to disease
viral infections- measles (rubeola) def incubation period -> first symptoms clinical signs immunity
- highly contagious disease caused by RNA measles virus occurring in young children
- incubation period of 10-21 days precedes prodrome with fever, cough, conjunctivitis and malaise
- clinical signs- blue-gray spots with red areola appear on buccal membranes and erithematosus macloapular rash spreading downwarrd from head -> face -> trunk and limbs lasting about 5 days
- recovery confers immunity and live vaccine is available (from Merck!!) :)
viral infections- rubella def clinical signs immunity congenital rubella
- mildly contagious viral (RNA) disease that usually affects children 5-15 yo
- clinical signs- mild- characterized by lymphadenopathy, maculopapular rash of duration 3-5d and conjunctivtis
- infection infers immunity
- congenital rubella is when fetus is infected during first trimester of gestation can be disastrous disease, causing fetal death, premature delivery and number of sever congenital defects
medical terminology:
macula
papular
pustule
macula- usually red rash, same level as skin
papular- red rash, popped up from skin
pustule- blister, papula with fluid in it