Rotavirus Flashcards
Rotavirus general
Major cause of diarrhoea in many domestic species Short incubation period (12-24 hours)
Clinical signs of Rotavirus
Profuse water diarrhoea (white scours), inappetence, depression, dehydration May stop suckling Low mortality, often associated with dehydration or secondary bacterial infection Disease usually seen in animals 1-8 weeks old Not in first week (colostrum) Reduced colostrum intake, overcrowding (environmental contamination builds up- immuno suppression), poor hygiene, chilling (using energy to stay warm)
Transmission (part of pathogenesis)
Transmission by ingestion of contaminated food, water, or fomites *highly infectious/ contagious High concentrations shed in faeces, infectious dose is small, minimal env. contam. leads to widespread env. effects
Rotavirus falls under what family?
Reoviridae (same as Orbivirus- blue tongue, African horse sickness)
Coronavirus and Rotavirus same pathogenesis- opposite of what disease?
Opposite of Parvo Severe enteritis- intestinal epithelial destruction (apical cells)- on the tips of the villi of the small intestine. These cells ahve an absorptive and secretory function (for example disaccharides like lactose). So when you stop breaking down lactose and absorbing the fluid, you end up with malabsorption. High conc. of sugar in the lumen, you get a secretory diarrhoea and osmotic diarrhoea. FLUID ACCUMULATION IN THE GUT= secretory diarrhoea. One of the proteins on the capsid of the rotavirus also induces hypersecretory diarrhoea.
Pathogenesis Rotavirus
Infection usually localised to SI, little local inflammation of infected enterocytes, little local inflammation of infected enterocytes, reduced ability to break down disaccharides such as lactose therefore osmotic diarrhoea in addition to secretory
What disinfectants do not work on rotavirus?
Bleach does not work– too much organic material as well but rotaviruses are resistant anyway. Chlorine does not work.
What is an enterotoxin?
Inflammation and secretory diarrhoea
Epi of Rotavirus
Excreted at very high titres, survive in faeces for months, resistant to chlorine disinfection, waterborne transmission?
Control of rotavirus
Improved hygiene (unlikely to control on its own), antibody in colostrum (crosses lumen of neonate gut and becomes systemic IgG), antibody in milk (lactogenic immunity- bind in the intestine- neutralize the virus and it passes through)- vaccination of dam that increases antibody in milk is protective. Dehydration and electrolyte imbalances are the major cause of death in rotavirus cases (fluid therapy and no milk).
What happens in an endemic situation with rotavirus and immunity?
Lactogenic immunity (antibody from milk neutralizes virus and it passes through) because Mom has been exposed prior and has the antibodies to pass on. So it keeps getting passed on down the line like this
What causes death with rotavirus?
Dehydration and electrolyte imbalances (fluid therapy and no milk)
Coronaviridae
Coronavirus causes all kinds of dysfunction
Bovine coronavirus diarrhoea
Very similar to rotavirus
Coronavirus- SARS
Severe Acute Respiratory Syndrome- fever, general malaise, headaches, chills, cough, death About 8000 cases with 800 deaths reported Spread by close contact/ secretions
Coronavirus
Enveloped, ss RNA
Bovine Coronaviridae general and transmission
Second most common cause of diarrhoea in calves (after rotavirus), less than 2 weeks old- diarrhoea lasts 4-5 days, replicates in mature SI epithelial cells- fluid absoption and digestion of disaccharides reduced Fecal oral route of transmission (secretory and osmotic diarrhoea)
Porcine Coronaviruses (4)
3 are exotic- we have Porcine Haemagglutinating Encephalomyelitis.
Porcine Resp Coronavirus acts as a natural vaccine to another coronavirus.
Porcine Epidemic Diarrhoea- massive US outbreak recently- watery dirrahoea
Epi and Pathogenesis of Porcine Coronavirus
Porcine Coronaviruses animals affected
Feline Infectious Peritonitis Virus (FIPV) (Coronaviruses) is a mutant of what?
Feline enteric coronaviruses (FECV)
FIPV Epi
Multi cat households, faecal oral transmission- enteric viruses that cause other disease, shed through GIT (faeces and oral/nasal), young cats and older cats see the most clinical signs. Kittens often infected from mom.
* In multi cat homes 15% of cats are persistently infected. Most cats are transiently infected (eliminate virus).
Pathogenesis of FIPV
Infection does not always result in a disease.
Most infected kittens develop an effective cell-mediated immune response and eliminate the virus.
**FECV infection sensitizes cats to FIPV as antibody enhances uptake by macrophages.**
What does the mutation of FIPV mean?
It can survive and replicate in macrophages (this is the mutation from FECV)
3 possibilities with immune response and therefore pathogenesis:
*If cat mounts effective cell mediated immune response infected macrophages get blasted away from cytotoxic T cells
*If there is a decreased immune response- normal cat periodic FIPV chronic ongoing shedder
*Non effective immune response- continuous FIPV replication- B cell activation- non protective antibodies- Abs enhance uptake by macrophages- immune complexes- vasculitis- and then either moderate lesions to dry FIPV (fatal over months) or severe vascular permeability (fatal over weeks)
*** MHC type makes certain breeds over represented with FIPV***
With FIPV, if the cat shows clinical signs, what does that mean?
The cat will most likely die. So mostly you don’t know about it, and if you do, they will likely die.
Infectious Bronchitis general
Highly contagious, economically important disease of chickens worldwide.
Respiratory system is the site of primary replication
Viraemia within 1-2 days of exposure
Virus distributed widely- oviducts, kidneys, Bursa, severity of lesions determined by strain virulence
Resp. transmission by aerosol (most imp route)
Shed from rep tract for several weeks
Also faeces and eggs of infected birds
Infectious Bronchitis
Chickens.
48 hour incubation
Most severe in young birds (stretch out trachea- gasp for air)
Nasal exudate
Death is caused by inflammatory debris in trachea- so they suffocate
Older birds- rales (resp noise) and gasping, reduced egg production
* Nephrotrophic strain- higher mortality
7 days in individuals
10-14 days in a whole flock (meaning REALLY contagious- sweeps through flock in a couple weeks)
Infectious Bronchitis Diagnosis
PCR
No Tx
Vaccines available
