Classical Swine Fever

What is Classical Swine Fever?

A highly contagious viral disease of domestic and wild swine that can be acute to chronic and can range from severe, with high mortality, to mild or even unapparent

What is CSF also known as?

Hog cholera

Describe the acute form of CSF

Manifested by high fever, depression, lack of appetite, diarrhea, reddened skin, internal hemorrhages and death

Describe the chronic form of CSF

Much milder and older pigs can recover

What is the mortality of acute CSF?

High: can approach 100%

What are the clinical signs of CSF?

-High fever, huddling, weakness, lethargy, decreased appetite, conjunctivitis, constipation or diarrhea, incoordination, posterior paresis, convulsions, vomiting, respiratory signs, skin hyperemia, hemorrhage or cyanosis

-Severe leukopenia

Describe subacute CSF

Clinical signs less severe, prolonged time course, lower mortality

What are the clinical signs of chronic CSF

-Decreased appetite, depression, fever, leukopenia, constipation or diarrhea, wasting or poor growth, skin lesions

-Clinical signs wax and wane for weeks to months

How soon should CSF be reported?

Immediately

What family does CSF belong to?

Flaviviridae

Describe viruses in the family flaviviridae

-Positive ssRNA

-Enveloped

What genus does CSF belong to?

Pestivirus (genotypes 1, 2 and 3)

What pestiviruses are related to CSF?

-Bovine virus diarrhea virus (BVD)

-Border disease of sheep

When was the US declared hog cholera free?

1978

What happened in 1978 in regards to CSF?

The U.S. was declared hog cholera free

The USDA APHIS surveillance plan for CSF includes surveillance for what 4 things?

1. Swine highly suspicious for CSF

2. Sick pigs submitted to a veterinary diagnostic laboratory

3. Pigs condemned at slaughter by the Food Safety and Inspection Service (FSIS)

4. Feral swine collected by Wildlife Services

How is CSF transmitted?

-Direct contact between animals: secretions, excretions, semen, blood

-Spread by farm visitors, veterinarians: Meat products, fomites and mechanical vectors

-In utero infections can lead to persistently infected piglets

What is the most common method of transmission for CSF?

Through direct contact between healthy swine and those infected with CSF virus:

-Primary oronasal transmission through direct or indirect contact

-Virus shed in oronasal and ocular secretions, urine, feces, blood

What kind of piglets can an infected pregnant gilt produce?

-Healthy piglets

-Persistently infected "shaker" piglets (Virus POS, antibody NEG)

-Stillbirths or abortions

What are the clinical signs of CSF in general?

Poor reproductive performance:

-May be only sign in herds infected with less virulent strains

-Abortion, stillbirths, mummified, malformed, weak piglets

-Piglets may be born with congenital tremor

-Piglets may be born persistently infected (non-clinical at birth, late onset clinical signs: inappetence, depression, poor growth, dermatitis, diarrhea, conjunctivitis, ataxia, posterior paresis, death typically within 1 year)

How is CSF transmitted by humans?

Contact with contaminated vehicles, pens, feed, or clothing may spread the disease

What is a major risk for CSF incursion into swine herds?

Feeding raw garbage

How long does CSF survive in pork and processed pork products?

Months when meat is refrigerated years when it is frozen

What is the incubation period of CSF in swine exposed post-natally?

2-14 days and often 3-7 days in acute cases. Animals with acute disease die within 1-2 weeks

What is the incubation period for CSF?

2-14, 15 days

What are the symptoms of CSF?

-Signs of CSF vary with the strain of classical swine fever virus and the age and susceptibility of the pigs

-High fever, huddling, constipation followed by D+ and reddened eyes are often seen

-The skin may show hemorrhages with discoloration of the ears, abdomen or inner thighs

-Young pigs may have incoordination, or weakness

-The disease can adversely affect reproduction with sows aborting or delivering stillborn or malformed piglets

-Milder forms of virus or infection in partially immune pigs may exhibit mild or no symptoms and yet still harbor and spread the virus

What are the lesions of CSF?

-Highly variable

-Acute disease

-Hemorrhage most common (skin discolored purple, cyanosis of extremities, lymph nodes swollen and hemorrhagic, petechial or ecchymotic hemorrhages on serosal and mucosal surfaces)

-GI: hemorrhage, enteritis, button ulcers

-Fluid in peritoneum, thorax or pericardial sac

-Tonsilitis (+/- necrotic foci)

-Splenic infarcts

-Lungs: congestion and hemorrhage

-Encephalitis

How is CSF diagnosed through virus detection?

-PCR, sequencing, FA, ELISA, VI

-Blood, tonsil, or nasal swabs (live)

-Tonsils, lymph nodes, brain, spleen, kidneys, ileum (necropsy)

How is CSF diagnosed via serology?

-FAVN

-ELISA (antibodies develop around 3 weeks post-infection)

What do you have to be conscious of when diagnosing CSF?

Cross reactivity with ruminant pestiviruses (BVDV and BDV occasionally infect pigs)

What are differentials for CSF?

-PDNS

-ASFV

-Septicemic bacterial diseases (Salmonellosis, erysipelas, acute Pasteurella)

-Severe PRRSV

How is CSF treated?

-Supportive care (no treatment for CSFV): prevention is the best practice

-Pigs that recover may shed virus for varying periods of time, serving as an infection risk to unaffected contact pigs

-CSF vaccines are available, require USDA approval for use, and can be used to assist in outbreak response efforts

Describe the vaccine available for CSF

-MLV vaccine

-Reduce clinical signs, limit transmission

-Employed to reduce infections during eradication program

-Widely used in CSF-free areas

-Not DIVA

How is CSF prevented and controlled?

-Slaughter of all pigs on affected farms

-Safe disposal of carcasses, bedding, etc.

-Thorough disinfection

-Designation of infected zone, with control of pig movements

-Detailed epidemiological investigation, with tracing of possible sources (up-stream)

-Surveillance of infected zone, and surrounding area

-Good biosecurity practices

-Cooking of food scraps for feeding pigs

-Control of animal importations

-Decontamination and disposal or foreign garbage