Post on 04-Feb-2016
description
Neonatal diarrhoea
Rota and coronavirusesOctober 6, 2010
Viral causes of diarrhoea in neonates
• Rotavirus• Coronavirus• BVD• Bredavirus• Calicivirus• Parvovirus• Astrovirus
Susceptibility of neonates
• Rotaviruses 4 to 14 days• Coronavirus 4 to 30
0 4 days
ColostralAntibodies in gut
Susceptible period
Prevention of viral diarrhea in calves
• Vaccination of pregnant animals• Colostrum for 2 weeks• Management
vaccines against calf diarrhoea
Rotaviruses
Viruses with ds RNA genomes
Reoviridae
Birnaviridae
rotaviruses
bluetongue virus
african horse sickness
infectious bursal disease (chickens)
infectious pancreatic necrosis (salmonid fish)
Rotaviruses
• 7 groups and many serotypes• DS, segmented genome• Unenveloped• Inactivated by phenolic disinfectants• Relatively insensitive to chlorination• Persistence?
Rotavirus structure, serogroups and serotypes
VP4
VP7VP6
VP3
VP2
VP1
7 Groups(A->G)
14 serotypes(G)
12 serotypes(P)
Segmented genomes of rotaviruses
implicationselectropherotyping
Bovine rotaviruses
Group A > B>CMost Group A, serotypes G6 and G10
Pathogenesislactase
water
water
Undigested milk
Shortened and fusedvilli
http://www.bovilis.com/diseases/ncd/pathogenesis.asp
Maintenance of rotaviruses in populations
• stable in environment• mucosal antibody more important than
systemic antibody• persistence and periodic shedding
Diagnosis
• Detection of virus in fecal smears by FAT– FAT for GrA (PDS)
• feces, $22 includes coronavirus• jejunum, ileum, $38.50, includes coronavirus
• EM and immune EM• antigen capture ELISAs (human test for Gr A
rotaviruses)– 80 to 95% sensitivity and specificity compared to RT-
PCR (Maes et al. 2003, J. clin micro 41:290)
Coronaviruses
Viruses with +ve RNA genomesPicornaviridae
Caliciviridae
Coronaviridae
Arteriviridae
Flaviviridae
Togaviridae
foot and mouth disease virus
porcine enteroviruses
feline calicivirus
equine arterivirus
pestiviruses (BVD)
coronaviruses
equine encephalitis viruses
Coronaviruses
• SS +ve RNA• Enveloped• Epithelial cells of gut and respiratory tract• Persistent infections• Increased shedding in winter and at calving
(bovine corona virus)
Diagnosis
• FAT on fecal or gut samples ($22.50-38.50/sample)
• EM ($45/sample)
Some other coronaviruses
• Transmissible gastroenteritis and respiratory disease in pigs
• Infectious bronchitis in poultry• Feline enteric coronavirus (FEC) and
infectious peritonitis (FIP)• Ferret (catarrhal enteritis and FIP-like)• SARS coronavirus
feline infectious peritonitis
M.C. Horzinek and H. LutzAn update on FIP
Veterinary Sience TomorrowJan, 2001
www.vetscite.org
FIP
• fatal disease of young (3-18 mo), or very old in multi-cat houses or catteries
• not seen before 1950– new virus?– old virus, new disease
• systemic antibodies not protective, may even be harmful
feline enteric coronavirus
• closely related to dog, pig (TGE), human coronaviruses– species specific but K9CV can infect cats
• two serotypes– serotype I
– more common, 70-95% of isolates, does not cross react with K9CV
– difficult to isolate
FeCV, serotype 2
Both serotypes can lead to FIP causing strains
epidemiology
• Exposure to FeCV– 25% of cats from 1-2 cat households are seropositive– 75-100% of cats from catteries seropositive
• susceptible cats become infected immediately following exposure
• kittens can become infected in utero or soon after maternal antibodies drop below protective levels
epidemiology (FIP)
• 1:5,000 in 1-2 cat households• 1:20 in catteries
– sporadic– clustered (2-3 cats) - rare– rarely epidemic
• no gender or breed predisposition
FIP pathogenesisFEC
Mild diarrhoeaor respiratory illness
persistent infection
virus immune system
low level of replication in epithelial and lymphoid cells
pregnancy in young queens elective surgery
weaning, sale, shipment,adoption
concurrent infections (FeLV, FIV ?)
Virus immunesystem
increased virus replication -> virulent mutants
increased ability to grow in macrophages
immune-mediated lysis of infected cells
cytokines draw in more susceptible cells
vascular permeability
immune complex related damage
M.C. Horzinek and H. LutzAn update on FIPVeterinary Sience
TomorrowJan, 2001
www.vetscite.org
clinical signs
• common signs– chronic antibiotic unresponsive fever– progressive anorexia, weight loss– stunting of growth
• blood abnormalities – progressive increase in serum proteins– increase in globulins– anemia– serum, urine brown due to bilirubin
clinical signs
• “wet” form (poor cell-mediated immunity)
– peritonitis– pleuritis
• “dry” form (some CMI)• granulomas• enlarged lymph nodes• cloudiness in eye• neurological signs
• can change from dry to wet
Sharif et al. 2010. Vet Med Int
diagnosis• RT-PCR for FeCoV• Serology (ELISA for anti FeCoV antibodies)
– prognosis?• no titre - no FIP but may still be infected• <100 - less chance of developing FIP• >100 - greater chance of getting FIP
• increased globulins and protein (>35g/L)• cytology
– degenerate and non-degenerate PMN, macrophages, some lymphocytes, protein background
– FeCV positive cells (FAT)
control
• vaccine– Primucell FIP
• Intranasal ts virus
• management– early weaning and separation