1. Picorna and Caliciviruses
October 14, 2009

2. Viruses with +ve RNA genomes
Aphtho
Entero
Picornaviridae
Rhino
Caliciviridae
Hepato
Cardio
Coronaviridae
feline calicivirus
coronaviruses
Arteriviridae
Genera of Picornaviridae:
Aphthovirus (Foot and Mouth Disease)
Entero (Polio, porcine enterovirus)
porcine enteoviruses - 11 serotypes. Most widely distributed. Varying virulence - Teschen disease (restricted to central Europe and East Africa), virulent strain of serotype 1, high morbidity and mortality - polio encephalomyelitis. Talfan disease/benign benign enzootic paresis, mild disease. Some serotypes may be associated with SMEDI
Rhino - cold viruses
Cardio - myocarditis
Hepato - hepatitis A
Calici - Norwalk, San Miguel sea lion virus, calici viruses of rabbits, vesicular exanthema in swine
equine arterivirus
Flaviviridae
pestiviruses (BVD)
Togaviridae
equine encephalitis viruses

3. Picornaviruses “pico” - small “rna” - RNA
single stranded, positive RNA
unenveloped, relatively stable

4. BBC a hundred days of foot and mouth
On individual basis FMD is not hugely significant - usually high morbidity and low mortality (very young animals - myocarditis). However, because of international trade barriers against countries with FMD economic implications are enormous. By CFIA estimates an outbreak of FMD would reduce the value of Canadian livestock by almost 2 billion dollars with costs to the cattle industry of over 30 million dollars per day.

5. Foot and mouth disease
highly contagious disease of domestic and wild ruminants and pigs.
systemic disease with high fever, vesicles on epithelial surfaces
not usually fatal in adults but causes economic losses (trade implications)
can be fatal in young animals - myocarditis
high morbidity, low mortality

6. Susceptibility to inactivationpH
stable between pH 7 and 9
inactivated by:
5% acetic acid or other acids
1-2% sodium hydroxide or other alkalis
phenolic and quarternary ammonium compounds - not effective
oxidizing agents (bleach) effective when environment not contaminated with organic substances. Detergents increase effectiveness
heat
in suspension 80o for 1 hr, 50o for 2 days, 37o for seven days
stable when associated with dried organic matter (see Dekker, 1998, Vet. Rec 143:168)
need to soak for 30 minutes to be safe - dipping not sufficient

7. CFIA recommendations for inactivation
50% solution of vinegar in water min
sodium carbonate, 100 gm/L - 30 min
citric acid powder - 2 gm/L - 30 min

8. Serotypes
7 serotypes - O, A, C, South African territories (SAT)-1, SAT-2, SAT-3, Asia
At least 60 subtypes

9. from:
Grubman and
Baxt, 2004

10. Susceptible species
domestic ruminants (cattle, buffalo, sheep, goats, camelids*)
wild or exotic ruminants (african buffalo, various antelope and deer species)
others (pigs, rabbits, mice, guinea pigs, chickens, elephants, humans)
horses are resistant
*Dromedary camels may not be susceptible - Wernery et al. Vet Rec February 11, 2006
Inoculated 2 heifers and 2 dromedary camels with isolate of serotype ). While both heifers showed typical lesions and virus was detected by RT-PCR the camels showed no lesions or virus. Neither of the camels seroconverted.

11. Different effects on susceptible species
pigs (amplifying hosts) - secrete large amounts of virus in breath, air borne spread
cattle (sentinel hosts) - highly sensitive to infection by respiratory route
sheep (maintenance hosts) - mild-asymptomatic disease, can spread through flocks before detection
pigs excrete times more virus than cattle. Pigs in intensive operations can create aerosol with high conc of virus. Can spread 10 to 60 km over land and 200 km over water
In UK outbreak sheep were asymptomatic while in Japan cattle were asymptomatic

12. Pathogenesis recovery infection clinical signs persistence
(most animals but effects can persist)
infection
(inhalation,
ingestion,
AI)
incubation period
(1-21 days, usually 3-5 in cattle, 4-9 in pigs)
clinical signs
(variable)
persistence
(months to years in partially immune animals, life time in some species)
infectious dose =
< 10 particles
virus shedding
(begins 1-4 days before
clinical signs appear)
direct - in all secretions and excretions, wind borne km if conditions are right
infection in pigs is by ingestion while in cattle it is by inhalation of droplets
indirect - environmentally stable, in contaminated animal products, can pass through birds and remain infectious
incubation period can vary from 1 day to 21 days although it is usually 3-5 days in cattle and 4-9 days in pigs. The shorter incubation periods are in naïve animals while the longer periods are in partially immune animals. 14 days is considered the maximum incubation period for quarantine purposes in FMD free countries that do not vaccinate.
Virus shedding can begin up to 5 days before clinical signs in cattle and 10 days in pigs
Brown J Histochem Cytochem March 3, Integrin alphav-beta6 rece3ptor for FMD, expressed on epithelia of airways, oral cavity, GI tract, sweat glands, hair follicle sheaths, epidermis coronary bands BUT NOT normal skin (consistent with tropism).
death
(myocarditis in young animals)

13. Clinical signs high fever - 40-41o
fluid filled vesicles - on mucosa and face, feet, hairless areas - rupture to form ulcers
sheep may not show clinical signs - as in UK outbreak
salivation, anorexia - lesions in mouth
lameness - ulcers on feet

14. Infection of heart muscle
young animals (up to 6 months of age in cattle)

15. Epidemiology
Factors that allow rapid spread and persistence in a population
antigenic variation (7 serotypes with no cross protection and many antigenic variants with limited cross reactivity)
large host-range (including wild-life)
low infectious dose (<10 particles)
large amounts of virus before clinical signs develop
no clinical signs in some species (sheep, cattle) allows spread
persistent infection in partially immune animals
hardy virus (many routes of spread, airborne)

16. Prevention In countries with endemic FMD FMD free countries
vaccination
vaccination and slaughter
FMD free countries
prevent introduction
in face of outbreak
test and slaughter
ring-vaccination and slaughter
ring-vaccination and slaughter only sick animals

17. Problems with vaccination
no cross protection if wrong serotype
short-lived immunity
partial protection if variant
does not prevent infection
persistent infection
cannot distinguish between vaccinated and infected animals
detection easier if no vaccination

18. Regaining FMD-free status
“stamping out” without vaccination - 3 months after last case
slaughter and ring vaccination - 3 months after last slaughter of last vaccinated animal
if all vaccinated animals are not slaughtered -
FMD free status with vaccination
12 months after last case
to regain FMD free without vaccination
no cases for 12 months after last vaccination
no importation of vaccinated animals

19. New Developments
Techniques that distinguish between vaccinated and infected animals
Vet J Jan;167(1):9-22.
* Vet J Jan;167(1):3-4.
Developments in diagnostic techniques for differentiating infection from vaccination in foot-and-mouth disease.
Clavijo A, Wright P, Kitching P.
National Centre for Foreign Animal Disease, Canadian Food Inspection Agency, Suite T2300, 1015 Arlington Street, Winnipeg, Manitoba, Canada R3E 3M4.
Foot-and-mouth disease (FMD) is a highly contagious and economically significant disease of cattle, pigs, sheep, goats and wild ruminant species. The FMD virus genome encodes a unique polyprotein from which the different viral polypeptides are cleaved by viral proteases, including eight different non-structural proteins (NSPs). Both structural and non-structural antigens induce the production of antibodies in infected animals. In contrast, vaccinated animals which have not been exposed to replicating virus will develop antibodies only to the viral antigens in the inactivated material. Vaccination against FMD is a key element in the control of the disease in addition to slaughter and movement restrictions. However, countries that vaccinate in the event of an outbreak will have to re-establish their FMD free status to the satisfaction of their trading partners.Because currently available vaccines stimulate the production of antibodies indistinguishable from those produced by infected animals in response to live virus and because vaccinated animals can be infected and become carriers of FMD virus, efforts have been made to develop diagnostic test that can differentiate vaccinated animals from those that are convalescent and from those that have been vaccinated and become carriers following subsequent contact with live virus. Currently the detection of antibodies to non-structural protein's (NSPs) is the preferred diagnostic method to distinguish virus infected, carrier, animals from vaccinated animals. However this is currently only possible at the herd level because of the great variability in the initiation, specificity and duration of the immune response in individual animals to the NSPs shown in many studies. Considerable effort and attention is now being directed toward the development of new methods and techniques for the rapid and accurate detection of anti-NSP antibodies, harmonization and standardization of current diagnostic techniques, as well as the production of defined reagents.
Moonen Vet Microbiol 99: tested three comercially available ELISAs for detection of antibodies to non-structural proteins. All three assays can be used on sera collected 4 weeks to 6 months after infection.
Cox Vaccine 23: Vaccination with O1 FMD isolate protected cattle from clinical disease when co-mingled with cattle infected with different strain of same serotype. Almost half of vaccinated animals became persistently infected but shed reduced amounts of virus.

20. Diagnosis
clinical signs - can be confused with other vesicular diseases
laboratory
sample collection
vesicle fluid, skin at edge of ruptured vesicle, excretions and secretions
inoculated onto susceptible cells
if cpe - confirm FMD and serotype by capture ELISA
if no cpe - 2 “blind” passages
PCR

21. Idiopathic vesicular disease in swine in Manitoba Tim Pasma, Suzanne Davidson, Sheryl Shaw, 2008, CVJ 49:84-85

22. Tim Pasma, 2008, CVJ 49:84-85

23. Some viruses that cause vesicular disease in swine
Foot and mouth disease (reportable)
Swine vesicular disease (reportable)
Vesicular stomatitis (reportable)
Vesicular exanthema (not in N America)
Porcine parvovirus
Porcine enterovirus

24. Calicivirus

25. Caliciviruses vesicular exanthema of swine San Miguel sea lion virus
feline calicivirus
rabbit haemorrhagic virus
bovine and porcine enteric caliciviruses
chicken calicivirus
Smith et al Jn Emerging Dis 4#1
5 groups: Sapporo, Norwalk, hepatitis E (fatal in 25% of pregnant women), marine caliciviruses, rabbit hemorrhagic disease (kills 95% of infected rabbits)
various outbreaks of vesicular disease in swine, quarantine of California uncooked pork train from San Francisco to Chicago -> outbreak in Cheyenne Wyoming -> 41 states. federal eradication program VES eradicated declaired “foreign disease”.
San Miguel virus, also from several sea-lions - “viruses indistinguishable from VESV”.
caliciviruses isolated from 11 species of marine mammals, fish, unknown host range, some infections of humans
sea-lions ->fish->pigs->mink
same virus from snakes and marine mammals
nematodes from marine mammals -> fish -> fur seals

26. feline calicivirus
Vet Res Mar-Apr;38(2): Epub 2007 Feb 13. Links
Feline calicivirus.
Radford AD, Coyne KP, Dawson S, Porter CJ, Gaskell RM.
University of Liverpool Veterinary Teaching Hospital, Leahurst, Chester High Road, Neston, S. Wirral, CH64 7TE, United Kingdom.
Feline calicivirus (FCV) is an important and highly prevalent pathogen of cats. It belongs to the family Caliciviridae which includes other significant pathogens of man and animals. As an RNA virus, high polymerase error rates convey upon FCV a high genome plasticity, and allow the virus to respond rapidly to environmental selection pressures. This makes the virus very adaptable and has important implications for clinical disease and its control. Being genetically diverse, FCV is associated with a range of clinical syndromes from inapparent infections to relatively mild oral and upper respiratory tract disease with or without acute lameness. More recently, highly virulent forms of the virus have emerged associated with a systemic infection that is frequently fatal. A proportion of FCV infected cats that recover from acute disease, remain persistently infected. In such cats, virus evolution is believed to help the virus to evade the host immune response. Such long-term carriers may only represent a minority of the feline population but are likely to be crucial to the epidemiology of the virus. Vaccination against FCV has been available for many years and has effectively reduced the incidence of clinical disease. However, the vaccines do not prevent infection and vaccinated cats can still become persistently infected. In addition, FCV strain variability means that not all strains are protected against equally. Much progress has been made in understanding the biology and pathogenesis of this important feline virus. Challenges for the future will necessarily focus on how to control the variability of this virus particularly in relation to emerging virulent strains and vaccination.

27. Fe calicivirus in exotic cats
J Zoo Wildl Med Jun;38(2):292-9.Links
Systemic calicivirus epidemic in captive exotic felids.
Harrison TM, Sikarskie J, Kruger J, Wise A, Mullaney TP, Kiupel M, Maes RK.
Potter Park Zoo, 1301 South Pennsylvania, Lansing, Michigan 48912, USA.
A 5-day-old, mother-raised, Amur tiger cub (Panthera tigris altaica) presented with tongue ulcerations. Identical lesions appeared and progressed to sloughing of the tongue in the three littermates of this cub the following day. The lesions progressed in all cubs to include sloughing of the carpal, tarsal, metacarpal, and metatarsal foot pad epithelium. Oral ulcerations were also noted in adult African lions (Panthera leo) and Amur tigers (Panthera tigris altaica), but not in two adult snow leopards (Panthera uncia) housed in the same building. All adult cats had been previously vaccinated for common feline diseases including feline calicivirus (FCV). Detection of FCV RNA in oral secretions by a real-time reverse transcription polymerase chain reaction assay (RRT-PCR) confirmed FCV infection in the tiger cubs and one lion. A male lion and a male tiger cub died during the disease outbreak. RRT-PCR confirmed FCV in multiple tissues in both of these animals. A stray cat live-trapped outside the feline building during the epidemic was found to be positive for FCV by virus isolation and was thought to be the source of infection.