LESSON 13 PICORNAVIRIDAE Flashcards
(Pico means very small) ^________ nm
22-30
PICORNAVIRIDAE
* Non-enveloped, _______-sense, _______ - stranded RNA viruses with _____
symmetry
The capsid is composed of __ protein subunits. Each subunit consists of four proteins ______,_____________,_________ …..
* The protein VP4 is located on the ____________///_
. Replicate in ______
*positive, single, icosahedral
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*VP1(1D), VP2 (1B), VP3 (1C) and VP4 (1A).
*inner surface of the capsid
*cytoplasm
Classification of picornaviruses of importance.Foot-and-mouth disease virus, swine vesicular disease virus and duck hepatitis A virus causes
OIE- listed diseases
is a highly contagious disease of
even-toed ungulates, characterized by fever and the formation of
vesicles.
Foot-and-mouth disease (FMD)
Foot-and-mouth disease (FMD) is a highly contagious disease of even-toed ungulates, characterized by fever and the formation of
vesicles.
Seven major serotypes are recognized _____________________________________________________________________________
No cross-immunity between different serotype but only within each serotype 70
Large amounts of virus are shed by infected animals in all ________________.
*FMDV-A, FMDV-Asia 1, FMDV-O, FMDV-C, FMDV Southern African Territories (SAT) 1, FMDV-SAT 2 and FMDV-SAT 3.
*secretions and excretions
FOOTH AND MOUTH DISEASE OR PICORNAVIRIDAE
Large amounts of virus are shed by infected animals in all secretions
and excretions.
Virus shedding begins during the incubation period, usually beginning about ______ before the appearance of clinical signs, and infectivity of animals is much reduced by __________ after the lesions develop.
Transmission occurs by ____, by animal products including
________●●●●●
Infected groups of animals, particularly ____, shed large quantities of
virus in exhaled air as an aerosol.
Under suitable conditions of low temperature, high humidity and
moderate winds such aerosols may spread the virus over long distances (within 10 km)
*24 hours
*four to five days
*direct contact
*meat, offal, milk, semen and embryos, by the airborne route or by
mechanical carriage by people, vehicles and fomites.
*pigs
PICORNAVIRIDAE ( FOOT AND MOUTH DISEASE)
____ are most susceptible to infection because of their large
respiratory volume and the low infective dose required.
The virus is moderately resistant but is sensitive to pH outside the
range 6.0 to 9.0.
Virus can remain infective on ____________.
Following death and rigor mortis, the production of lactic acid in
muscle inactivates the pH-labile virus but virus may persist in offal
and bone marrow.
Foot-and-mouth disease virus can persist in the pharyngeal region of
animals that have recovered from FMD or in vaccinated animals
following contact with live virus.
Persistence can last up to three years in cattle, several months in
sheep and up to five years in African Cape buffalo
*Cattle
*soil for three days in the summer and
for 28 days in the winter
*
FOOTH AND MOUTH DISEASE OR PICORNAVIRIDAE
The principal route of infection is by ___, although infection
can also occur by ______…
Following inhalation viral replication occurs in the pharynx
followed by spread to the bloodstream and distribution to
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predilection sites including the epithelium of the mouth, muzzle,
feet and teats.
Vesicle formation results from swelling and rupture of infected
____________ in the stratified squamous epithelium at these sites.
*inhalation
*ingestion, insemination, inoculation or contact
with abraded skin.
*keratinocytes
FOOTH AND MOUTH DISEASE OR PICORNAVIRIDAE
Following an incubation period of________ , infected
cattle demonstrate_____,_____,_____
There is profuse salivation as vesicles appear in the mouth and
rapidly rupture leaving raw, painful ulcers. Vesicles also appear
in the interdigital cleft and on the coronary band giving rise to
lameness and the shifting of weight from one foot to another. Vesicles may appear on the teats and udder of lactating cows.
The lesions heal rapidly but may become secondarily infected
giving rise to mastitis and underrunning of the sole.
Infected animals show a marked loss in condition and growth
rate but mortality in adult cattle is rare.
Death may occur in calves due to acute myocarditis.
Although the virus does not cross the placenta, abortion may
occur, probably as a result of the fever. In pigs feet lesions are more pronounced and the hooves may
slough.
_________ is marked and the most prominent clinical sign in pigs.
The disease in sheep, goats and wild ruminants is generally
milder, presenting as a rapidly spreading lameness accompanied
by fever.
Infection in man has been described on a few occasions, usually
in laboratory personnel working with the virus or in people
handling infected animals. The disease is mild and characterized
by fever and vesiculation of the skin and mucous membrane
*two to eight days
*fever, loss of appetite, and a marked drop in
milk production.
*Lameness
FOOTH AND MOUTH DISEASE OR PICORNAVIRIDAE
Diagnosis: ELISA, RT-PCR, virus demonstrations from cell culture
Control: vaccinations; affected and in-contact animals are
slaughtered. Following an outbreak, movement restrictions are
applied and infected premises must be thoroughly cleaned and
disinfected. Mild acids such as citric acid and acetic acid and alkalis
such as sodium carbonate are effective disinfectant
a mild vesicular disease of pigs which occurs sporadically in parts of
Europe and Asia.
Swine Vesicular Disease (SVD)
___________It is clinically indistinguishable from foot-and-mouth disease.
Swine vesicular disease virus is an __________
Swine Vesicular Disease (SVD)
enterovirus
Swine Vesicular Disease (SVD)
a mild vesicular disease of pigs which occurs sporadically in parts of
Europe and Asia. it is clinically indistinguishable from foot-and-mouth disease. Swine vesicular disease virus is an enterovirus
The natural host is pig but is zoonotic (mild infection in man)
Transmission can occur by direct or indirect contact, the virus is
stable for long periods in the presence of organic matter in the
environment. The spread of disease from farm to farm is dependent on the
movement of infected pigs or contaminated materials. The tissues of infected pigs contain large quantities of virus. The
infectivity of the virus is retained despite the pH changes that occur
during rigor mortis and the virus can persist indefinitely in
refrigerated pork.
Swine Vesicular Disease (SVD
Pathogenesis:
The incubation period is two to seven days. Subclinical disease is common:
Following the entry of virus through damaged skin or
ingestion, there is local replication followed by
spread via the lymphatics to the bloodstream. During the two- to three-day viraemia many organs
and tissues become infected. Shedding of virus can start before clinical signs are
evident and is heaviest in the first week following
infection. The faeces and lesion material of infected pigs may
contain infective virus for many weeks or months. The clinical disease is characterized by a transient fever
followed by the development of vesicular lesions on the
feet, particularly on the coronary band, and less
commonly on the lips, tongue and snout. Lameness,
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dullness and inappetence occur but are not constant
signs. The animals do not lose condition and the lesions heal
rapidly over the course of a few weeks. The severity of the clinical signs is influenced by the
strain of SVDV, the route and dose of infection and the
husbandry conditions
Swine Vesicular Disease (SVD)
Diagnosis: serological test (ELISA), cell culture to demonstrate
cytopathic effect (CPE), virus neutralization test, RT-PCR
Control: Bio-security, vaccines. Control measures, applied following
an outbreak of SVD, include thorough cleaning and disinfection of
premises, control of pig movement and boiling of waste food fed to
pigs.
