Veterinary Science and Microbiology
VSC438 Ecology of Infectious
Disease
Viruses, Dr. Jim Collins
1) Track down the host or reservoir species; consider vector species; investigate geography of human cases including sub-clinical human cases with serology; compare the isolated viruses, usually by sequencing the isolates. These methods can be used for any suspected emergent virus.
2) It would take the same set of circumstances to re-occur; since we don't fully know exactly what happened the appearance of the virus in humans again is unprdictable. It is arguable that it is UNLIKELY!
3) Most experts would assert that
we would first need to know if the vaccine was safe and worked in humans -
through animal models and volunteers! Secondly, one would also need to know
the populations at risk. Finally, more work is needed so as to be able to
estimate the likelyhood of re-emergence.
1)
Definition of a virus: small, protected nucleic acid ((+/-),
single/double or single/single DNA or RNA) that replicate inside cells and
usually kills the cell, and it is transmitted
2)
The
ecological niches of FMD are: animals!
3) Can’t be stopped from spreading around the
world because it is so stable and because of the many modes of transmission:
-animal to animal, via environmental
source, via meat products, slaughter house
remains, via humans, and via air
(wind)
3)
FMD
would make a good Bioterrorism agent because animals:
-can acquire it easily, slaughtering of cattle can
severely depress economy and food supplies, travelers can carry disease
1) Rabies is increasing in raccoons. Rabies spreads from bites and very rarely by
introduction into an open wound by saliva. .
2)
Methods
of control are to depopulate wildlife, vaccination (Oral Rabies Vaccine Program
in Texas) and trap-vaccinate-release programs, habitat modification (eliminate
food sources, access to human dwellings, and denning areas underneath houses).
3)
-bite -> muscles (where virus replicates)->neuron (vaccination here
can’t stop)->
ganglia, spinal cord,
brain->medulla->midbrain->hippocampus->behavior
(wandering, aggression) -> salivary
and other glands (kidney failure)->encephalitis/death
-virus keeps affecting (killing) neurons
-can only test brain for rabies
(hippocampus)
4) Biological features that prevent us from controlling
the virus in the host is that it locates inside of neurons.
1 – it remains hidden or latent – for a long time in
a wild animal and we have no warning that it is there and can finally cause
rabies. 2 – Rabies causes the animal to
stalk and bite, transmitting the virus. 3- Once it gets into a neuron, we
cannot stop it – fatal.
5) Coconino, Cochise, Pima, and Santa Cruz counties
for terrestial reabies; all of Arizona for Bat rabies. Surveillance of dead animals, vaccination and release
of skunks, public education, quarantine of animals.
1)
Protect
horse and household from West Nile virus by using vaccines (horses), mosquito
control, wearing protective clothing and repellents, surveillance of dead
birds and chicken sentinel flock, surveillance by the Department of Health
Services.
2)
Disease
control measure in 1800’s was to separate sewage and drinking water, drain swamps, get rid of standing water.
3)
Enzootic cycle-(Yellow Fever) mosq->monkey->mosq->monkey
Epizootic cycle- mosq->monkey->mosq->monkey
-> Aedes Aegypti -> humans
Urban cycle- (Dengue Fever) aedes->aedes->human->aedes
-> humans
Jungle cycle is an enzootic cycle in the jungle, like
your Yellow fever example above
4)
The importance of trans-ovarial transmission is
1)
?
Antigenic shift cause by mutations that arise in the virus genome that lead
to evasionof the immune response......
2)
Influenza viruses mix by exchange of gene segments during co-infection of
a host like the pig, followed by selection of the most fit virus and transmission
to another host, pigs or humans, etc.
3)
Influenza from pigs leads to virulent human
viruses, but not from chickens because the selection of viruses in pigs leads
to the correct mammalian receptor affinity whereas in birds only the avian
receptor affinity can be selected.
Only in the pig does virus receptor affinity change
so that the virus has affinity for humans
4)
Control
influenza through surveillance, proper hygiene, annual vaccines, and stop
mixing pigs with birds.
1)
Three
ways that spongioform encephalopathy can arise in an individual are 1) from
eating neural tissue from infected, diseased animals or receiving infected
transplant material (cornea or dura matter), or 2) by inheriting a prion gene
which is prone to initiate prion disease, or 3) or by spontaneous (and rare)
mis-folding of the endogenous prion protein, initiating prion disease.
2)
Disinfect bench of prions by 1 M NaOH
3)
BSE
still arising because the meal is still being used.
4)
There
is still a possible epidemic of vCJD because humans who consumed contaminated
beef in Great Britain might have a long latent period before developing the
disease.
1)
Eradication
of measles and polio can be accomplished by finding all human cases then by
breaking the chain of transmission (quarantine), and vaccinating the population
2)
Lowering of measles deaths before the development of vaccines was due to
3)
Looking
at attack rate figures, measles vaccine in US will not be effective in eliminating
all cases because there are still many people who don’t want to be vaccinated
(fear, religious groups, and militant resistance)
4)
Interrupting
transmission of measles is difficult because of the long latent period during
which an individual does not realize thaey have the virus but are spreading
it (just like HIV!).
5)
We
know where the virus comes from in an outbreak because CDC takes throat washings,
isolates the virus and types it into 8 groups consisting of the virus’ country
of origin.
Examples are 1=UK, Russia, 2=Phillipines, 3=Japan,
4= Europe, etc…?
1)
The
evidence that HIV came from SIVcpz is: SIVcpz infected chimps have antibodies
to HIV; sequences similarity and genomic organization relationship; geographic
range of chimps with SIV similar to humans with HIV; phylogenetic studies
of Lentiviruses, specific HIV and SIV show that viruses could have evolved
from each other through mutations.
2)
The
RNA polymerase likely led to HIV->SIV because of errors and mutations arose
that were not corrected, followed by selection of a variant, by chance, in
humans.
3)
HIV
epidemics in US and W. Europe involve transmitted mainly through homosexual
sex, sex industries such as prostitution, and by sharing of needles of IV
drug users. HIV epidemic in Africa is mainly transmitted
through
1)
Rodents
are natural reservoir hosts for hemorrhagic fever viruses. They spread the viruses among themselves, remain
persistently infected and transmit the virus through secretions to dead end
hosts such as humans.
2)
Rodent
zoonosis are diseases that are transmitted from rodents to humans.
3)
Animal->animal->human->human
4)
Yes