Transcript Viral causes of diarrhoea in neonates

Neonatal diarrhoea
Rota and coronaviruses
October 6, 2010
Viral causes of diarrhoea in
neonates
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Rotavirus
Coronavirus
BVD
Bredavirus
Calicivirus
Parvovirus
Astrovirus
Susceptibility of neonates
• Rotaviruses 4 to 14 days
• Coronavirus 4 to 30
0
4 days
Colostral
Antibodies 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
rotaviruses
Reoviridae
bluetongue virus
african horse sickness
Birnaviridae
infectious bursal disease (chickens)
infectious pancreatic necrosis (salmonid fish)
Rotaviruses
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7 groups and many serotypes
DS, segmented genome
Unenveloped
Inactivated by phenolic disinfectants
Relatively insensitive to chlorination
Persistence?
Rotavirus structure, serogroups
and serotypes
VP1
VP2
VP3
VP6
7 Groups
(A->G)
VP4
12 serotypes
(P)
VP7
14 serotypes
(G)
Segmented genomes of
rotaviruses
electropherotyping
implications
Bovine rotaviruses
Group A > B>C
Most Group A, serotypes G6 and G10
http://www.bovilis.com/diseases/ncd/pathogenesis.asp
Pathogenesis
lactase
water
Undigested
milk
water
Shortened and fused
villi
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 RTPCR (Maes et al. 2003, J. clin micro 41:290)
Coronaviruses
Viruses with +ve RNA genomes
Picornaviridae
Caliciviridae
foot and mouth disease virus
porcine enteroviruses
feline calicivirus
Coronaviridae
Arteriviridae
coronaviruses
equine arterivirus
Flaviviridae
Togaviridae
pestiviruses (BVD)
equine encephalitis viruses
Coronaviruses
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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 ($22.5038.50/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. Lutz
An update on FIP
Veterinary Sience Tomorrow
Jan, 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
FEC
FIP pathogenesis
Mild diarrhoea
or respiratory illness
virus
immune system
persistent infection
low level of replication in epithelial and lymphoid cells
pregnancy in
young queens
weaning, sale,
shipment,
adoption
elective surgery
concurrent infections
(FeLV, FIV ?)
Virus
immune
system
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. Lutz
An update on FIP
Veterinary Sience
Tomorrow
Jan, 2001
www.vetscite.org
clinical signs
• common signs
– chronic antibiotic unresponsive fever
– progressive anorexia, weight loss
– stunting of growth
• blood abnormalities
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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)
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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