the body's defenses Flashcards
all pathogenic prokaryotes known to date are archaea/bacteria
bacteria
bacteria cause what fraction of all human diseases
1/2
some bacterial diseases are transmitted by other species such as…………..
ticks and fleas
prokaryotic pathogens usually cause illness by producing what
poisons
what are the 2 classes of poison
endotoxin
exotoxin
what is an exotoxin
a toxic protein that is secreted by a prokaryote or other pathogens that produces specific symptoms even if the pathogen is no longer present
what is an endotoxin
a toxic component of the outer membrane (lipopolysaccharide) of certain gram negative bacteria that is released only when the bacteria die
how can horizontal gene transfer transform normally harmless bacteria into pathogens
horizontal gene transfer can spread genes associated with virulence e.g. E.coli is normally harmless but a pathogenic strain has evolved
what are the 3 types of symbiosis
mutualism
commensalism
parasitism
what are chemoautotrophic bacteria
they harvest chemical energy from compounds such as hydrogen sulphide e.g. in a hydrothermal vent
what are arthropods
segmented bodies with a hard exoskeleton and jointed appendages e.g. insects, spiders, crabs, lice and fleas
do arthropods have an open or closed circulatory system
open
what are zoonotic pathogens
those that are transferred to humans from other animals either through direct contact with an infected animal or by means of an intermediate species called a vector
give examples of parasites that spread zoonotic diseases
ticks, lice and mosquitos
why is identifying the dominant host for a pathogen important
you can then target the host to control spreading of the disease
for a particular locus, which genotype has the greatest fitness
heterozygotes
what is an epidemic
a general outbreak of disease with higher incidence than would normally be expected for a particular geography or population
what is an endemic
the constant presence and/or usual prevalence of a disease for a particular geography or population
what is a pandemic
a global epidemic spreading across continents
which human behaviours in history have influenced epidemic disease
exploration changes in patterns of trade warfare famine poverty, overcrowding and poor living conditions
how have human behaviours influenced epidemic disease
they brought the opportunity for infectious agent to expand beyond its original ‘disease pool’ with devastating effect
what was the black death
Bubonic plague - the first pandemic
what organism carried the bubonic plague
fleas
how did the fleas infect humans with the plague
they jumped from black rats to humans
what type of transmission does the plague fall under
zoonosis - jump from one species to another
what are symptoms of the plague
gangrene of extremities
rapid onset and appearance of buboes
infection of the lymphatic system
what id the vector species in plague transmission
infected fleas
what bacterium causes plague
Yersinia pestis
how can plague be treated
with antibiotics unless the strain is resistant
how can plague be prevented
pest control (rod of the rats)
how is small pox spread
by droplets
what are the symptoms of small pox
high fever and flu like illnesses
rash - infectious pustules
what are the two types of influenza
A and B
which type of influenza has caused pandemics
A
which influenza A antigen is important for binding to the host cell
hemagglutinin
which influenza A antigen is important for release from infected cell
neuraminidase
why does influenza A cause pandemics
antigenic drift - caused by gene mutation and antigen variation
what is Spanish flu
bird to human transmission of the avian virus
what type of transmission does the Spanish flu show
zoonosis
how is syphilis spread
by sexual contact - can result in still birth or deformities
how is syphilis treated
penicillin injection
which disease is known as the disease of war and famine
typhus
what is typhus caused by
an obligate intracellular bacterium
how are typhus bacterium transmitted to humans
via body lice
what are symptoms of typhus
fever, chills, headache, muscle pain, confusion, rash
what is typhus treated with
antibiotics
are typhoid fever and typhus the same thing
NOOOOOOOOOOOOOO!!!!!
what is typhoid fever caused by
salmonella typhi bacterium
it has to be ingested
how can salmonella typhi be ingested
water contaminated with faecal matter
what are typhoid fever symptoms
headache, fever, abdominal pain (enlarged spleen/liver), diarrhoea/constipation, rash
how can typhoid fever be controlled
safe drinking water
proper sewage disposal
antibiotics
vaccines
what are the virulent factors of the typhoid life cycle involved in
in symptom development and immune evasion
what bacteria causes cholera
vibrio cholerae - when ingested from faecal matter
how many types of vibrio cholerae cause disease
2
what is the natural habitat of vibrio cholerae
freshwater, brackish and coastal-water habitats
what is the action of vibrio cholerae
it produces a toxin that modifies a g protein involved in slat and water regulation
cAMP is continuously made resulting in intestinal cells secreting a large amount of salts into the intestines along with water by osmosis causing major diarrhoea
how can cholera be controlled
safe drinking water
proper sewage disposal
antibiotics
vaccines
what is polio
Illness through gastrointestinal infection by poliovirus
what does the poliovirus do
replicate in motor neurons if invade CNS
how is poliovirus transmitted
mainly through contact with faeces
what are the 2 types of polio vaccine
sabin and salk
what are the sabin vaccines made of
attenuated viruses
what are the salk vaccines made of
inactivated vaccine (used in UK since 2004)
what is TB caused by
Mycobacterium tuberculosis (MTB)
TB has a latent form, what does this mean
it is non infectious at this stage
how is TB spread
person to person through air
what are symptoms of TB
cough, night sweats, chest pain, coughing up blood/mucous
what are treatments for TB
6 month course of antimicrobial drugs
what are methods of TB prevention
vaccination
what is the treatment for HIV
lifelong drug treatment - no cure
what is a parasite
‘A parasite is an organism living in or on another living organisms, obtaining from it part or all of its organic nutrition, commonly exhibiting some degree of adaptive structural modification and potentially causing some degree of damage to its host
what is prevalence
the proportion of a population infected (e.g.3%)
what is incidence
• Incidence – the proportion infected in a unit of time i.e. the number of new infections e.g. 3% per week
what is intensity
the number of parasites per host
what is mortality
the number of deaths in a unit of time
what is morbidity
the amount of ill – health/disability in a unit of time
what is DALY
Disability adjusted life year – a measure of overall disease burden. The number of years of lost to ill health, disability or early death
what are ectoparasites
live on the organism e.g. lice
what are endo parasites
live in the organism e.g. tapeworms, toxoplasma gondii
what are NTDs
neglected tropical diseases - diseases that cause substantial illness for more than one billion people globally.
what are examples of NTDs
schistosomiasis
infection rates and disease burdens of NETs are greatest where
poorest communities lacking infrastructure and sanitation.
what are ascaris lumbricoides
round worms
what can ascaris lumbricoides be treated with
Oral albendazole, mebendazole and/or Ivermectin
How is schistosomiasis transmitted
in water
what is the cycle of schistosomiasis
parasitic eggs in water larvae hatch and infect snails - the vector larvae released into water penetrate human skin larvae mature into worms cause liver problems worms lay eggs that cause damage eggs released into water via urine or faeces
how to cure schistosomiasis
using drugs
prevention of schistosomiasis
treatment of breeding snails
what is the plasmodium life cycle
transmission to human via mosquito bite sporozoites enter liver and infect hepatocytes liver cells rupture sexual cycle mosquito ingests gametocytes sporozoites develop
why don’t we have vaccines for schistosomiasis and malaria
- Complex life cycles, with multiple stages in different tissues
- High level of antigenic variation, e.g. blood stage malaria
- Multiple immune evasion strategies (eg sequestration)
- Parasites are able to suppress the immune system
