Lecture 5 - Part 1. FMD, ASFV & CSFV Flashcards
Diseases are divided into categories:
A, B, C, D, E
Disease category A
Diseases that do not normally occur in the EU and for which immediate eradicaton measures must be taken as soon as they are detetcted.
Disease category B
Diseases which must be controlled in all member states with the goal of eradicating them throughout the EU
Disease category C
DIseases which are of relevance to some Member States and for which measures are needed to prevent them from spreading to parts of the Union that are officially disease-free or that have eradication programs for the listed disease concerned.
Disease category D
Diseases for which measures are needed to prevent them from spreading on account of their movements between member states or entry into the EU.
Disease category E
Diseases for which there is a need for surveillance within the EU.
Notifiable animal diseases, so Highly contagious animal diseases, first half (6)
Foot and mouth disease
African swine fever
Classical swine fever
Rinderpest
Lumpy skin disease
Contagious bovine pleuropneumonia
Notifiable animal diseases, so Highly contagious animal diseases, 2nd half (7)
Sheep pox and goat pox
Peste des Petits Ruminants
Contagious caprine pleuropneumonia
African horse sickness
Glanders
(Highly pathogenic) Avian influenza
Newcastle disease
Name 3 Vesicular animal diseases
Foot and mouth disease
Vesicular stomatitis
Swine vesicular disease
(Vesicular exanthema of swine virus)
What species are susceptible to foot and mouth disease?
all cloven-hoofed animals
Domestic: cattle, pigs, sheep, goats, llamas, alpacas, camels, buffalos
Wild: African buffalos, deer, moose, wild pigs, giraffes, elephants etc.
What species are susceptible to vesicular stomatitis disease? (4)
bovine
swine
goats
horses
FOOT AND MOUTH DISEASE (FMD) is
a highly infectious viral disease of cloven-hoofed species characterized by fever and vesicles in the mouth and on the muzzle, teats, and feet.
FOOT AND MOUTH DISEASE (FMD) is rarely fatal except for - who and why?
young animals due to dystrophy of the heart and skeletal muscles.
How many serotypes of FMDV?
foot and mouth disease virus
7 serotypes exist: A, O, C, SAT1, SAT2, SAT3, Asia1
Serotypes do not confer cross immunity —> vaccination!
FMDV belongs to what viral family?
foot and mouth disease virus
family Picornaviridae,
genus Aphthovirus,
is an RNA-virus
FMDV can be inactivated by pH of?
Virus can be inactivated by pH <6.5 and pH >11.
Survives in milk and milk products, bone marrow and lymph nodes.
Can persist in contaminated fodder and the environment for up to 1 month!
Morbidity & mortality & recovery of FMDV
High morbidity (100%) in all age groups
Mortality <1%
Higher in young animals (myocarditis)
Recovery in 2 weeks.
World distribution of FMDV?
Endemic: Asia, Africa, Middle-East ja South-America
FMDV endemic where?
Asia, Africa, Middle-East ja South-America
Transmission of FMDV.
Virus is excreted with all body fluids.
So if e.g. you were not to find it in the fluid of a vesicle, then you can rule out FMD.
Incubation period of FMDV:
2-14 days
Can be as little as 24h!
Depends on the viral load - the smaller the dose, the longer the incubation period.
FMDV viral replication occurs where (typically)?
inthe oropharynx (tonsils!) and/or skin
Epithelial cells lyse, formation of blisters.
Which species are considered maintenance hosts for FMDV?
Sheep and goats are considered maintenance hosts for FMD; they have mild signs which delay diagnosis and allow for aerosol, contact spread, and environmental contamination.
Sheep can carry the virus in their pharyngeal tissue for 4-6 months.
What is meant by indicator host?
indicator host because they are often the first species to demonstrate clinical signs. Lesions quickly progress and become severe.
For FMD this is cows.
What is meant as amplifier host?
Pigs are amplifying hosts of FMD; they produce large quantities of aerosolized virus, but shed for a short time and are not long-term carriers
Which species are considered indicator hosts for FMDV?
Cows because they are often the first species to demonstrate clinical signs.
Cattle can carry the virus in their pharyngeal tissue for 6-24 months once infected with FMD.
Vaccination can protect from clinical signs but does not prevent development of the carrier state.
Which species are considered amplifier hosts for FMDV?
Pigs are amplifying hosts; they produce large quantities of aerosolized virus, but shed for a short time and are not long-term carriers
Course of FMD disease in cows:
acute, because cows are indicator hosts for FMD.
Clinical signs of FMD in cattle.
Pyrexia, anorexia, shivering, reduction in milk production (2-3 days), then:
smacking of the lips, grinding of the teeth, drooling, lameness, stamping or kicking of the feet.
vesicles in the mouth and on the muzzle, teats and feet
after 24h: rupture of vesicles —> erosions
Recovery time for FMD in cattle?
Recovery in 8-15 days
Complications of FMD in cattle?
tongue erosions,
superinfection of lesions,
hoof deformation,
mastitis and permanent impairment of milk production,
myocarditis,
abortions,
permanent weight loss,
loss of heat control (‘panters’)
Death of young animals from myocarditis.
Clinical signs of FMD in goats and sheep.
Are not as clear as in e.g. cattle, signs can be very mild which is why these are maintenance hosts.
Pyrexia
Lameness and oral lesions are often mild - complicates diagnosis
Agalactia
Death of young stock may occur without clinical signs.
Foot lesions along the coronary band or interdigital spaces may go unrecognised, as may lesions on the dental pad.
Clinical signs of FMD in pigs.
Pyrexia
foot lesions with lameness
(even detachment of the claw horn)
Vesicles at pressure points of the limbs, especially along the carpus (‘knuckling’)
Vesicular lesions on snout and dry lesions on the tongue
High mortality of piglets
Cardiac change in FMD cases.
Gray or yellow streaking in the heart from myocarditis, degeneration and necrosis of the myocardium in young animals of all species (‘tiger heart’).
Humans can catch FMD how?
milk, or droplet transmission from ppl with it
in very rare cases from animals, but disease is mild.
ddx for FMDV (3)
Vesicular diseases are clinically indistinguishable so they’re your main ddx!
vesicular stomatitis
swine vesicular disease
vesicular exanthema of swine
other ddx for FMDV other than the vesicular diseases (5)
burns - e.g. chemical, thermal
rinderpest
bovine viral diarrhoea and mucosal disease
infectious bovine rhinotracheitis
bluetongue disease
Material needed for Diagnosis of FMDV.(4)
an unruptured vesicle’s fluid (1ml),
or recently ruptured vesicle’s tissue (1g)
oesophageal-pharyngeal fluid
blood
Laboratory Diagnosis of FMDV.(3)
Virus isolation in cell-culture which is slow (4 days), but has high sensitivity and specificity.
Antigen ELISA - fast (hours), but may produce false positives.
RT-PCR
Prevention & control of FMDV (4-5)
Biosafety measures
Disinfection
Emergency vaccination
Strategy: stamping out
+ Destruction of carcasses by burning or burial
Classical swine fever (CSF) is also known as
hog cholera
CLASSICAL SWINE FEVER (CSF) is a
highly contagious disease of pigs,
caused by a Pestivirus,
characterised by high fever, lethargy, diarrhoea, vomiting and purple skin discolouration of the ears, lower abdomen and legs.
CSFV stands for
Classical swine fever virus
Classical swine fever virus belongs to what family
family Flaviviridae,
genus Pestivirus
RNA-virus
Classical swine fever virus /CSFV serotypes
one serotype
minor antigenic variability between viral strains
three genotypes, ten subtypes
Classical swine fever virus /CSFV stability
Inactivation pH <3 and >11
Does not persist long in the environment
Survives in refrigerated meat (months) and frozen meat (years)
Host range of CSFV
swine only!
Mostly seen in autumn.
CSFV Morbidity & mortality
Age and immune status affect mortality: piglets are more susceptible than adults.
Acute strain - high mortality (<100%)
Subacute - M&M both lower
Chronic - only few animals are affected but is always fatal!
Asymptomatic cases can occur.
Transmission of CSFV via
blood, saliva, urine, faeces, tissues
Starts during incubation period, goes on for months after recovery.
Direct contact
Indirect contact (fomites)
Entry portal: ingestion, membranes, skin abrasions.
Less common: aerosol, semen, vectors
Reservoir of CSFV
only infected pigs!
CSFV Incubation period:
2-14 days
CSFV Persistent viraemia in
Congenitally infected piglets
Shedding of the virus for months!
Form of CSFV disease.
Mostly we see: subacute, chronic or atypical form of the disease.
Disease is variable from acutely fatal to asymptomatic.
Clinical signs of CSFV acute dz
Clinical signs are similar to other swine diseases (e.g. ASF)
Pyrexia (>40⁰C), huddling, weakness, anorexia, Conjunctivitis, Diarrhea, staggering, cyanosis, skin hemorrhages, death.
Clinical signs of subacute CSFV dz
similar to acute, but symptoms less severe.
pigs may survive!
Clinical signs of chronic CSFV dz
anorexia, depression, fever, diarrhoea
abortions, stillbirths, deformities
persistently infected pigs
almost always fatal
Clinical signs of congenital CSFV infection
persistent viraemia
tremors
deformities
persistently infected pigs disease is almost always fatal
Post mortem: CSFV acute dz
Highly variable
Haemorrhages
Necrotic foci in tonsils
Petechiae/ecchymoses on serosal and mucosal surfaces - kidneys, larynx, trachea, intestines, spleen, lungs
What type of post mortem ulcer is typical to chronic CSFV
necrotic foci called button ulcers, found in the: intestinal mucosa
epiglottis
larynx
Post mortem findings in congenital CSFV
cerebellar hypoplasia
thymic atrophy
haemorrhages
deformities
DDx for CSFV
ASF
Acute PRRS
Porcine dermatitis and nephropathy syndrome
Erysipelas
Salmonellosis
Eperythozoonosis
Actinobacillosis
Glasser’s disease
Aujeszky disease
Thrombocytopenic purpura
Warfarin poisoning
Heavy metal toxicity
… and other generalized septicemic or hemorrhagic conditions.
Suspect CSFV when…?
Suspect when:
Characteristic post mortem signs (hemorrages in internal organs)
High morbidity
Clinical signs: anorexia, deaths, reproductive symptoms
History of garbage/scrap feeding
Materials for CSFV detection.
ideally tonsil tissue
but also whole blood
Laborarotry analyses for detection of CSFV.
Detect virus, antigens or nucleic acids
Serology - ELISA or virus neutralisation, comparative neutralisation test
Treatment for CSFV.
There is no treatment!
Strategy for eradication of CSFV.
- rapid control via culling of infected animals and preemptive slaughter
- Restriction of movements
- Emergency vaccination
- Prophylactic vaccination in endemic areas – not in EU!
- ring vaccination in occurrence of an outbreak
ASFV
african swine fever virus
AFRICAN SWINE FEVER (ASF) is a
moderately contagious* disease of pigs, caused by Asfivirus, characterised by pyrexia, haemorrhages and high mortality.
- In books it is still ‘highly contagious’ but now we have new information
ASF is caused by what virus and belongs to which family
Asfivirus
family Asfarviridae, genus Asfivirus
“ASFAR” - African swine fever and related viruses
DNA-virus!
How many genotypes of ASF?
23 genotypes
no antigenic variability between viral strains!
ASF virus stimulates antibodies but
the antibodies do not neutralise the virus!
The lack of neutralizing antibodies is one of the reasons that explains the absence of an effective vaccine against ASFV nowadays
the only known DNA virus that is transmitted by arthropods.
ASFV
The virus replicates in Ornithodoros ticks and can be transmitted to swine through the bite of the tick.
ASFV stability
Inactivation pH <3.9 and >11.5
Serum increases the resistance of the virus
(pH 13.4 - 21h vs 7 days with serum)
Remains viable for long periods in blood, faeces and tissues (pork products!)
ASFV can survive for how long in;
4*C blood
room temp. feces
putrefied blood
contaminated pig pens
frozen meat
4’C blood 18 months
room temp. feces 11 days
putrefied blood 15 weeks
contaminated pig pens 1 month
frozen meat 1000 days
Host range of ASFV:
swine
African wild suids are asymptomatic carriers
Ticks (Ornithodoros sp.) - natural arthropod host and reservoir of the dz
reservoir of ASFV
African wild suids - asymptomatic carriers
(not the ticks!)
Morbidity & mortality of ASFV
Morbidity in naive population <100%
Mortality - dependent of the virulence;
high virulence <100%
low virulence - lower mortality
Morbidity versus mortality versus case fatality rate
morbidity = cases of illness
mortality = the cases of death that occur in a population
case fatality rate = the proportion of cases that die from a specified disease among all individuals diagnosed with the disease
What is the treatment for ASFV?
No treatment or vaccine currently exists for this disease.
So, culling.
Transmission of ASFV.
Direct contact
Indirect contact
feeding on garbage containing infected meat
fomites
biological vectors - ticks (Ornithodoros sp)
Within tick vector: transstadial, transovarial, sexual transmission.
Route: oronasal, via tick bites
Excretion of ASFV.
Excretion: blood, tissues, secretions and excretions of sick and dead animals.
Excretion starts during the incubation period.
Forms of ASF disease:
peracute, acute, subacute and chronic
Clinical form of ASFV disease depends on (4)
virus strain virulence
exposure dose
exposure route
host
Incubation period of AFSV:
3-15 days
Excretion starts during the incubation period.
add from note bit on slide 70
how to identify peracute ASFV disease
sudden death with just a few lesions or no clinical signs
Initial signs of ASFV infection (not depending on the virulence of the virus):
intermittent low fever, appetite loss, weight loss, respiratory signs
Also with strains of higher virulence the initial signs are the same; we might not see the signs of acute disease because pigs die before they can develop.
Only in post mortem we can see some hemorrages in internal organs.
good difference between the ambiguous or prodromal signs of ASFV versus classic swine fever is:
african swine fever: respiratory
classic swine fever : diarrhea
Clinical signs: acute AFSV
short IP: 3-7 days
high fever (<42⁰C), anorexia, lethargy, weakness, recumbency
cyanotic skin blotching on the ears, tail, lower legs and hams
abdominal pain, constipation or diarrhoea (mucoid —> bloody)
dyspnea, vomiting, nasal and conjunctival discharges, neurologic signs
abortions
leucopenia
death in 5-10 days
Clinical signs: subacute ASFV
caused by moderately virulent strains
similar clinical signs than in acute dz, just less severe
mortality is low in adults
very high in young animals
fever, thrombocytopenia and leukopenia may be transient - affected pigs die or recover within 3-4 weeks
Clinical signs: chronic ASFV
caused by strain with low virulence.
intermittent low fever, appetite loss, weight loss, depression, respiratory signs, necrosis in areas of skin, chronic skin ulcers, arthritis
pericarditis, adhesions of lungs, swelling over joints.
can go on for months (2-15 months)
can be fatal, though low mortality
Review this table on African swine fever disease forms.
Post mortem changes in acute ASFV
haemorrhages in LNs
petechial haemorrhages of the kidneys
congestive splenomegaly
oedematous areas of cyanosis in hairless parts
cutaneous ecchymoses on the legs and abdomen
excess of pleural, pericardial and/or peritoneal fluid
Post mortem changes in chronic ASFV
focal caseous necrosis and mineralisation of the lungs
enlarged LN
DDx for ASFV
classical swine fever - needs lab to distinguish!
Porcine reproductive and respiratory syndrome (PRRS)
Erysipelas
Salmonellosis
Aujeszky’s disease - younger animals
Pasteurellosis
Porcine dermatitis and nephropathy syndrome
Actinobacillosis
other septicaemic conditions
heavy metal toxicity
Diagnosis of ASFV
Suspect when: characteristic post mortem signs, anorexia, depression and sudden deaths in the herd
Material for diagnosis of ASFV
tissue samples (LN, spleen, kidney, lung), blood and serum
Prevention, control & Treatment for ASFV.
Immobilisation and surveillance areas?
No Tx
No vaccine
Culling!
Immobilisation areas:
Protection area 3km
Surveillance area 10km
Laboratory analyses for diagnosis of ASFV
PCR & ELISA mainly
Haemadsorption test (HAD)
Fluorescent antibody test (FAT)
Indirect fluorescent antibody (IFA)
Immunoblotting test
