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| commonest cause of neonatal diarrhoea in calves and lambs= |
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3layered icosahedral capsid
(3layers of protein) |
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| how long does rotavirus survive in enviro? |
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6months -1yr
resistnat to dessictaion and UV light
outer capsid = bile and acid resisitant |
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| in inner capsid of rotavirus = |
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12 copies of RNA pol
11segments of dsRNA
capping enzymes |
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| rotavirus replicates in... |
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| infection of rotavirus by... |
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| for rotavirus to become infectious it requires... |
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...predigestion by trypsin (a protease) to gte rid of outer capsid
This restricts rotavirus infection to the intestine as not activated until in intestine |
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| rotavirus infects cell via... |
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...adhesion and endocytosis
intermediate capsid inserts proteins into cell mb of endosome = derc IC Ca2+ = change in intermediate capsid = disintergration of endosome and inner capsid/core in cytoplasm |
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| mRNA synth of rotavirus occurs in... |
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...virus core
does this to hide dsRNA as dsRNA = a potnent inducer of IFN reaction |
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| protein synth of rotavirus occurs in... |
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| ...cytoplasm, ER mb and golgi body |
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| what is done to prevent initiation of hosts immune response? |
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| dsRNA hidden in core and - RNA strand only synth in core (as both of these would otherwise trigger IFN immune response) |
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| rotavirus exits host cell via... |
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...cell mb budding and then gets rid of lipid ENV (as rotavirus has no ENV)
or cell lysis (larg no of virus released) |
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| the 11 segments of dsRNA in rotavirus encode what? |
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9 ds RNAs encode single proteins (monocystronic)
2 dsRNAs produce a peptide thats cleaved into 2 proteins
so in total 13virus proteins are made |
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| large amorphous mass of viral protein where viral replictaion occurs |
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sialic acid
therefore may be zoonotic, spread by insect vectors |
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| are humans at risk of calf ans sheep rotavirus? |
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| do you have to have marked/gross intestinal pathology for diarrhoea to occur sue to rotavirus? |
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...direct inhibition of SGLT1
...activateion of Ca2+ release from ER
=diarrhoea |
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| activation of Ca2+ release from ER of microvilli due to NSP4 causes... |
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1. distruption of cytoskeleton, cell perm and tight junctions = water leaks, cell out
2. loose microvilli = derc SA = decr absorption
3. decr dissacharides such as lactulase = bacteria fermentation of lactose in neonates =osmotic secretion
4. incr ca2+ contributes to virus synth and stability
5. incr Ca2+ causes infected cell to secrete amines, peptides, NO and cytokines = activate neteric NS = activate crypt cell secretion and gut motility |
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| most susceptible to rotavirus infection = |
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| rotavirus is a dz of ________. |
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1. EM of faecal rotavirus - looks like wheel
2. strains distinguished by diff sizes of their RNA segments (diff banding pattern of RNA on polyacrilamide gel)
3. Ag capture ELISA test
4. latex agglutination tests |
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...rotavirus virus proteins on outer capsid = neutralising effect - stop virus adhering to cell mb
Abs have to be in SI (no gd in blood) |
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| most effective protection from rotavirus = |
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| IgA (from maternal milk therefore calves reared on artificial milk are more at risk of dz) |
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| killed vacc used to boost maternal Ab levels |
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| disadvantages of killed rotavirus vacc = |
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-many rotavirus strians, not all included in vacc
-annual boosters req |
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Bluetongue virus (BTV)
african horse sickness |
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| orbivirus structure and replication same as... |
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| most imp sheep dz in the world = |
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...midges-cullicoid imicola
(local UK midges can also act as vectors if weather hot enough) |
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small insects (<5mmm long)
short mouthparts
chews through sheep(hosts) skin = ruptures bvs=pool of blood=sucks up blood |
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| in local areas of midge bite site |
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...reticulo-endothelial cells:
-dendritic cells
-macro
-lympho
-endothelial cells |
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| BTV spreads around body as... |
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| ...cell associuated virameia, howevere it can be free in blood |
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1. fever - due to damaged endothelium and leukocytes (virus qu. gd at ducking IFN response)
2. inappentance
3. conjunctivitis
4. hyoeraemia (incr blood in organs, mucous mbs and coronary band)
5. drooling
6. lameness
7. oedema (due to leaky bvs)-pulm oedema = resp distress = cyanosis = 'blue tongue', liquid out of nose from lungs - chokes animals |
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| if sheep with BTV got a blue tongue = |
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prognosis is BAD!
and it is not as common a sign of BTV as you would think! |
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| on PM what do BTV infected lungs look like? |
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| v red, heavy lungs with froth in trachea |
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| in general what sp are more resistant to BTV? |
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| cattle and native african breeds |
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| what must BTV do in midge b4 it can reinfect host? |
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| replicate in midge gut & spread to salivary glands of midge |
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| does BTV infection harm the midge? |
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no
not cytopathic in insect cells 9doesnt want to kill vetcor, need vector to spread and reinfect host) |
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| how long does it take midge to become infectious? |
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| replication of BTV in cullicoides is _____ dependent |
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| a single bite of carrier insect ALWAYS infects sheep with BTV, but an injection of BTV of similar quantity isnt always infectious. WHy? |
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| insect saliva effects host immunity and viruses pathogenicity |
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...eggs in soil or manure
unlikely virus can survive in wintering insect eggs |
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| transovarial transmisison of BTV in insects? |
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| longer than sheep and doesnt cause as severe clinical signs |
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| cattle - BTV may be surviving winter in cattle lymphocytes - gamma delta Tcells can become persistantly infected(viraemia). |
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| how is virus overwintered in cattle viraemia re-activated? |
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| midge bite in summer = inflam = attract and activate lymhpho =activate and release virus from lympho |
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| what midge feed at the start of summer becomes infected with BTV? |
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| the midge feed ~ 4hrs after 1st midge feed, as it take ~4hrs to reactivate virus and thereofre for the cow to become an active/infectious carrier |
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| full complement of proteins produced by a particular genome |
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1. inhibit Xa = inhibit blood coagulation
2. collagenase = soften tissue and clot buster
3. apyrase = ATP and ADP to AMP = vasodilation
4. stop Thelpre 1 and incr Thelper 2 response = wrond immune response to tackle virus
5. insect trypsin can cleave virsu outer capsid = enhance BTV infectivity
6. cause inflam response= incr cells in local area of viral infection for virus to infect |
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1. inactivated/killed BTV8 strain
2. live attenuated
3. virus like particle |
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| strain of BTV seen in UK = |
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| inactivated/killed BTV8 vacc = |
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specific - only effective against BTV8 strain
variable efficacy
safe
used in UK and eliminated BTV8 strain outbreak |
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| why dont we use the live attenuated BTV vacc in UK anymore? |
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| may revert to virulent strain! |
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| virus like particle BTV vacc = |
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| inner and outer capsid proteins made in bacculovirus get strong neutralising Ab response against outer capsid = protect from clinical dz, but may not prevent infection or carrier status developing. Safe as no nucleic acid = no replication |
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| is BTV currently a problem in UK? |
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