L27: Rotaviruses (Romero) Flashcards
Rotavirus structure
- dsRNA
- wheel shape in electron microscopy
Clinical features of rotaviruses
- d in mammals/birds
- very short incubation period
- ingestion of milk worsens d in mammals**
- reduced colostrum intake increases severity of d and serious dehydration**
- most recover within few days
CS of porcine rotavirus
Sows: transient d
Piglets: profuse d, severe dehydration due to flocculent material lesions in SI
Pathogenesis of rotavirus
- destroy terminally differentiated enterocytes lining tips of SI villi
- dec. lactase production from enterocytes
transmission of rotaviruses
- excreted in feces
- fecal-oral trans.
- persist in environment
- bacterial/viral co-infections common (rotavirus itself usually not cause of systemic disease**)
Dx of rotaviruses
- CS
- electron microscopy
- immunoelectron microscopy
- enzyme immunoassay
- electropherotype of RNA
- RT-PCR
Prevention of porcine rotaviruses
- sanitation
- don’t mix pigs of different ages
- immunoprophylaxis: vaccines, group specific immunity
Tx of porcine rotaviruses
- supportive tx w/ fluids
- abx to control concurrent infections
- electrolyte solutions containing glucose and glycine ad libitum
Immunity to rotaviruses**
- local immunity in the SI is most important in protecting the young**
- colostrum Ab is transudated back into the intestine**
- continuous feeding of small amounts of colostrum is most effective in protection**
vaccination against rotaviruses
vaccinate dams with attenuated or inactivated vaccines to elicit neutralizing Ab that are transferred to colostrum and milk
Bovine viral diarrhea virus general chars.
- group of related viruses w/ varying virulence
- responsible for 2 clinically different diseases: Bovine viral diarrhea (an acute epizootic infection) and Mucosal disease (a sporadic lethal enzootic disease of persistently-infected bovines)
Bovine viral diarrheal virus susceptible hosts
cattle buffalo antelope llamas alpaca
Epi of Bovine Viral Diarrhea Virus
1) Postnatal infection in non-pregnant cattle (mainly calves)
2) Infection in pregnant cows: transplacental infection to embryos or fetus
3) Persistent infection in calves and mucosal disease –> severe disease, death
Pathogenesis of Bovine Viral Diarrhea Virus
- resp. transmission
- replicate in nasal mucosa/tonsils
- spreads to regional LN and then systemically, esp. lymphoid tissue and intestines
- usually subclinical
Prenatal and persistent infections of Bovine Viral D virus
- abortion, stillbirth, malformation
- growth retard, abn hair coat, stunting
- usually die by 2 yrs
Mucosal disease cause
-caused by persistent infection with non-cytopathic bovine viral diarrhea virus biotype that mutates into a cytopathic biotype
transmission of Bovine Viral Diarrhea Virus
- fomites, body fluids, placental tissue from PERSISTENTLY infected animals
- poor trans. from acutely-affected animals
- persistently infected bovines shed life-long
What is responsible for more than 50% of total mortality in feedlots?
Bovine Respiratory Disease Complex
What can compose Bovine Respiratory Disease Complex
Viruses: -Bovine viral diarrhea -Infectious bovine rhinotracheitis -Bovine coronavirus -Bovine respiratory syncytial virus -Bovine parainfluenza virus 3 Bacteria: Mannheimaia haemolytica
Dx of Bovine Viral Diarrhea
- CS, necropsy
- virus isolation
- detect viral Ag in ear notch biopsy
- RT-PCR
- Serology: persistently infected animals are Ab NEGATIVE**
Prevention and Control of Bovine Viral Diarrhea virus
- ID and immediate culling of persistently-infected bovines are key to control
- test new members of herd and vaccinate
Vaccination for Bovine Viral Diarrhea virus
- live-attenuated (not in pregnant cows)
- inactivated viruses reduce clinical dz but don’t prevent fetal infection
- useless to vaccinate persistently-infected animals
Infectious Bursal Disease/Gumboro disease Virus chars.
- highly contagious
- spreads rapidly through flocks
- droppings contaminate environment
- no vertical trans.
- no carrier state
- hardy in env.
2 clinical forms of Infectious Bursal Disease/Gumboro disease**
1) Subclinical (young chicks; causes severe immunosuppression; most economically important)
2) Clinical (older chicks; rapid increased in mortality)
gross lesions assoc. with infectious bursal disease (IBD)/ Gumboro**
- Primarily in BURSA OF FABRICIUS** (hemorrhage, caseous material, swelling, atrophy)
- Muscle hemorrhage
- distended renal tubules due to urates from dehydration
- hemorrhage in kidneys and b/w proventriculus/gizzard
Cardinal microscopic lesions assoc. with infectious bursal disease (IBD)/ Gumboro**
- Primarily in bursa of Fabricius**
- Necrosis, Edema, cystic cavities, fibroplasia, atrophy of BF**
Dx of infectious bursal disease (IBD)/ Gumboro disease
- must determine pathotype of field virus
- virus isolation in the allantoic membrane or yolk sac of embryonated hen’s eggs
- impression smears of affected BF and direct immunofluorescence with labeled antiserum
- RT-PCR of RNA from BF or Spleen
Why vaccinate chickens against Gumboro?**
Breeder hens: to stim. development of high and persistent levels of VN antibodies to be transferred to progeny chicks through the egg during laying period
Young Chicks: to prevent immunosuppression, morbidity and mortality after natural infection w/ virulent IBDV during first 4 wks of life
