Swine 14 Flashcards
What are major areas of concern for the Canadian swine industry in the event of an outbreak of foreign animal disease?
n Economics
> Shut down exports – 50% of production exported
n Restrict farm-to-farm movement
> Multi-site production, pig flow affected
n Disposal of carcasses
n Mental health
What major foreign animal disease(s) is/are the “most likely” to occur in the Canadian pig population?
- pseudorabies
- foot and mouth disease
- hog cholera
- african swine fever
Pseudorabies (Aujeszky’s Disease) is caused by what virus?
Pseudorabies virus
> suid herpesvirus 1 (suHV-1)
Pseudorabies (Aujeszky’s Disease) - persists in the host in what state, leading to what?
- can persist in latent state
- resulting in carrier animals and subclinical infections
Pseudorabies (Aujeszky’s Disease) survival in environment, susceptibility
Moderately resistant outside of the host
- Probably doesn’t survive much longer than 2 weeks outside of host
- Can be destroyed by disinfectants
can we distinguish pseudorabies titer from natural infection?
Marker vaccines make it possible to distinguish vaccine titres from natural virus antibody levels
Pseudorabies pathogenesis? predilection sites?
Pathogenesis: varies depending on the viral strain, age of pig, and viral load
- Inhalation or ingestion
> Replicates in upper respiratory tract epithelium
- Spreads to LN then, CNS: spinal cord and brain
> Localizes in many areas forms intranuclear inclusion bodies
- Localizes in Tonsil primary site
- Causes inflammation and necrosis of tissue
- Respiratory tract, bronchial tree, alveoli, endometritis, vaginitis, necrotic placentitis, fetus
()()()()
epithelial cells of upper resp tract > lymph vessles
> tonsil and local lymph nodes, then possibilities:
- > neurons innervating the facial and oropharyngeal area
-olfactory
-trigeminal
-glossopharyngeal
replication of PRV in the central nervous system is characterized by nonsupprative meningoencephalitis causing severe central nervous disorders
further spread to different neurons
latent infectin of neurons - > viremia
dissemination to multiple organs
replication in epithelia, vascular endothelium, lymphocytes, and macrophages
what happens when Pseydorabies gets into the central nervous system? what lesions do we see?
eplication of PRV in the central nervous system is characterized by nonsupprative meningoencephalitis causing severe central nervous disorders
Pseudorabies (Aujeszky’s Disease) is excreted how? for how long?
Excreted in large numbers in saliva, nasal secretions, urine and feces (for up to 2 weeks)
Pseudorabies (Aujeszky’s Disease) persists where in the pig?
n Persists in tonsil for several weeks
n Latent in CNS for many months
Pseudorabies (Aujeszky’s Disease): non-swine dead-end hosts; what animals, what signs? what countries
– causes fatal neurologic disease (rabies-like signs) and severe itching (mad-itch)
> Dogs, cats, cattle mice, racoons, mink, foxes….
> Found in most countries except: Canada, Greenland, Australia.
> USA – eradicated from commercial herds 2004
Pseudorabies (Aujeszky’s Disease) transmission
- Highly contagious, spreads through herd rapidly
- Mainly spread through respiratory route, oral-nasal
> pig-to-pig via oral and nasal secretions - Also, transplacental, milk, vaginal mucosa, semen
- Possibly airborne
- Fomites
Pseudorabies: clinical signs are variable, what do they depend on?
- Three ‘overlapping’ syndromes
- Age-dependant
- Infectious dose and strain dependant
> CNS, respiratory and reproductive
Pseudorabies: clinical signs in neonates. when do we see them? what are they? what about in weaned pigs?
NEONATES:
- Ill within 2-4 days after exposure
> High mortality ~100% usually within 1-3 days
> Sometimes sudden death
- Listless, anorexic, and pyrexia
- Neurological signs
> depression, tremors, convulsions, incoordination, dog-sitting posture, coma and death
Weaned pigs:
- Similar signs but mortality is usually much lower
Pseudorabies: clinical signs in gow-finish pigs:
- Primarily respiratory signs
> Coughing, sneezing, nasal discharge
> Loss of body condition - Pyrexia, anorexia, depression
- +/- CNS signs: tremors, convulsions
- High morbidity and low mortality
> many recover in 7-10 days
Pseudorabies: clinical signs in adult swine
- Pyrexia, anorexia
- Respiratory signs
> sneezing and coughing and laboured breathing - Most recover
- Abortions, returns, stillbirths, weak pigs
Pseudorabies in non-swine species: who is susceptible/ clinical signs?
- Dead-end hosts
> All livestock mammals, and cats, dogs, raccoons, skunks - Infected animals die within 1 to 2 days
before shedding virus – always fatal - Intense pruritis (mad itch)
- Neurological signs (rabies-like)
psudorabies gross lesions and histology
Gross lesions:
- fibrinonecrotic rhinitis / severe necrotizing rhinitis
- necrotic tonsillitis
- foci of necrosis in liver (neonate), spleen, lung
- aborted fetuses
> microscopic lesions in nervous tissue
Histology:
- intranuclear inclusion bodies
Pseudorabies; diagnosis and control
- History: including death of cats and dogs, high mortality in neonates, abortions, neurologic signs
- Many tests: FA, IHC, PCR, HISTOLOGY
- Eradication in U.S. (2004)
> DIVA Vaccine (gene-deleted)
> Vaccine highly efficacious - No treatment
- Inform CFIA of suspected cases – REPORTABLE!!
Foot-and-mouth disease (FMD); caused by what type of virus? strains?
- Picornaviridae
- Many strains - differ antigenically, limited cross protection
Foot-and-mouth disease (FMD) transmission
- Transmitted through respiratory droplets and nose-to-nose contact
> 50km aerosol