CLASSICAL SWINE FEVER (CSF): CAUSES, SYMPTOMS & EFFECTIVE PREVENTION AND TREATMENT

Classical Swine Fever (CSF) is a major threat to pig farmers, an infectious disease with rapid and strong transmission in pigs, caused by a virus. The characteristic of the disease is that the virus causes damage and pathological changes in many organs, especially the digestive system, leading to severe diarrhea due to intestinal ulcers. Fivevet provides effective solutions for prevention and treatment, helping to protect pig herds, stabilize production and reduce economic losses.

1. Classical Swine Fever
Classical swine fever is caused by a virus belonging to the family Flaviviridae, genus Pestivirus. The family Flaviviridae is divided into three main genera:
- Genus Flavivirus: Consists of 69 species of viruses, including 10 species important in veterinary medicine such as Japanese encephalitis virus, Wesselsbron virus, … causing dangerous diseases like hemorrhagic fever, encephalitis, and hepatitis.
- Genus Pestivirus: Includes 3 species of viruses causing diseases in livestock:
+ Bovine viral diarrhea virus (BVDV).
+ Border disease virus (BDV).
+ Classical swine fever virus (CSFV) or Hog cholera virus (HCV).
- Genus Hepacivirus: Contains viruses that cause hepatitis C and G in humans.
*Resistance
- Resistance is not high to environmental conditions, easily inactivated by temperature.
- Suitable pH ranges from 5–10, depending on temperature; the ability of the virus to be inactivated at pH < 5 varies.
- Disinfectants that quickly destroy the virus:
+ NaOH 2%: destroyed after 15 minutes.
+ Lime water 10%: destroyed after 15 minutes.
+ Phenic acid: destroyed after 15 minutes.
- In barns and manure, the virus is inactivated after a few days.
- In frozen pork, the virus can survive for many years, being a dangerous source of infection even for disease-free areas.
2. Epidemiology
a. Animals susceptible to classical swine fever
- Pigs of all breeds and ages can contract the disease.
- The disease spreads rapidly and strongly, with high morbidity and mortality rates.
- Adult pigs usually show milder symptoms than piglets.
- In the laboratory, the virus can cause disease in young pigs and rabbits.
b. Modes of transmission
- Transmitted directly or indirectly through the digestive tract.
- Humans are an important factor in spreading the virus.
- Transmission can occur through the air.
- Spread via semen during artificial insemination.
- Sows transmit the disease to their offspring through the placenta.
3. Clinical symptoms of classical swine fever
a. Peracute form
- Usually occurs at the early stage of an outbreak.
- Piglets are more susceptible to this form than adult pigs.
- Symptoms: severely depressed and a very high fever.
- Rapid progression; pigs die suddenly before the characteristic signs of the disease appear.
b. Acute form
- Incubation period: 2–4 days.
- Initial symptoms: pigs are depressed, fatigued, eat less or stop eating, move little.
- High fever: 41–42 °C, lasting 3–5 days.
- Piglets often lie piled up in a corner of the pen.
- Degree of spread: in a susceptible herd, initially only one pig is infected, but after 10 days the entire herd may be affected.
- Digestive signs:
+ Vomiting.
+ During the fever stage: constipation.
+ When the fever subsides: severe diarrhea.
+ Feces are watery, foul-smelling, sometimes containing blood and sloughed mucosal fragments.
- Respiratory signs:
+ Inflammation of the nasal mucosa, nasal discharge (initially clear and watery, later cloudy and thick, sometimes drying at the nostrils causing cracks at the margins).
+ Coughing: at first infrequent and dry; later frequent and moist.
- Nervous symptoms:
+ Staggering, unsteady gait.
+ Paralysis of the hind legs or paralysis of the posterior half of the body.
- Eyes:
+ Conjunctivitis and keratitis.
+ Lacrimation (at first clear and watery; later cloudy and thick).
- Skin:
+ Hemorrhages of varying sizes, from pinhead to pin size.
+ Numerous petechiae concentrated into patches, resembling “burnt sesame seeds.”
+ In some cases, large hemorrhages the size of a corn kernel, bruised and located deep under the skin.
Pigs die within one week after showing clinical signs, with mortality rates reaching up to 100%.
c. Chronic form
Caused by a virus strain of moderate virulence or by the progression from the acute form.
- Symptoms:
+ Pigs are emaciated, with prolonged diarrhea.
+ Fever appears intermittently.
+ Loss of appetite, reduced resistance, prone to secondary bacterial infections.
- Course of the disease: Lasts several weeks to a few months (2–3 months) before death.
- Effects on pregnant sows:
+ CSF virus can be transmitted through the placenta.
Depending on the virulence of the virus strain and the stage of pregnancy at infection, sows may:
+ Abort.
+ Have stillbirths.
+ Give birth prematurely.
If a sow is infected at 50–70 days of gestation, she may give birth to piglets carrying the virus.
- Effects on piglets born from infected sows:
+ May die immediately after birth.
+ Or appear normal at birth, then develop trembling, stunted growth, without fever.
+ Die after several weeks or months.
→ This phenomenon is called “late-onset swine fever.”
d. Subclinical form (persistent course)
When infecting pregnant sows, the classical swine fever virus can pass through the uterus and enter the fetus. Sows usually show only mild clinical signs, making detection difficult. Depending on the stage of pregnancy at infection, sows may experience abortion, mummified fetuses or premature birth. If infection occurs at 50–70 days of gestation, the piglets born may carry the virus and develop the “late-onset swine fever” form.
In addition, newborn piglets infected 8 or 48 hours after birth may also exhibit this form. This represents a dangerous source of transmission within the farm, causing a persistent and hard-to-control outbreak.

4. Pathological lesions of classical swine fever
a. Acute form
Cadavers are emaciated, with feces smeared around the anus. Hemorrhages appear on the skin, especially in thin-skinned areas, with numerous spots and petechiae. The oral mucosa and gums are inflamed, hemorrhagic, sometimes with shallow or deep ulcers covered with bright white or pale yellow exudate.
Surface hemorrhages of the lungs: hemorrhages of varying sizes, from pinhead to pin-sized. The lungs have numerous inflammatory patches with different colors: red, brown. The mucosa and trachea are inflamed, on the mucosal surfaces with abundant frothy pink mucus.
Characteristic lesions in the digestive tract: Inflammation of the gastric mucosa, especially in the fundus and pyloric regions, with hemorrhagic patches or ulcers, particularly in the Peyer’s patches. Button-like ulcers appear on the mucosa of the ileocecal valve, and sometimes on the colonic mucosa.
Lymph nodes swollen, characteristic hemorrhage, can be observed hemorrhage in 3 states:
- Hemorrhage entire node, making node dark purple like amaranth fruit, plum, or ripe grape.
- Hemorrhage at edge of node.
- Hemorrhage in strips, with marbled pattern.
Spleen usually not swollen or slightly swollen, surface has hemorrhagic spots the size of pinhead or needle tip. The edge of the spleen due to congestion forms areas of necrotic tissue, usually dark purple, triangular, apex pointing inward. The edge of the spleen looks serrated, unevenly convex and concave – This is a characteristic lesion but not present in every case. The most common lesions are swollen or hemorrhagic lymph nodes or tonsils.
Kidneys swollen, kidney surface has hemorrhagic spots the size of pinhead or needle tip. Cutting the kidneys in half shows blood clots. Hemorrhage of the bladder mucosa, in some cases urine is red due to accumulated blood inside the bladder.
Gallbladder may be distended or atrophied, gallbladder mucosa hemorrhagic with many tiny spots or concentrated in patches.

In the chronic form, usually observed are button-like ulcers in the digestive tract, epiglottis, and larynx.

5. Diagnosis of Classical Swine Fever
a. Clinical Diagnosis
Based on characteristic symptoms and pathological lesions, from which a preliminary conclusion about the disease is made.
b. Paraclinical Diagnosis
Collect samples from the spleen, tonsillar lymph nodes, lymph nodes or blood and immediately send to the laboratory FiveLab – Central Veterinary Diagnostic and Testing Center 5 for testing, providing the fastest and most accurate results.
Contact FiveLab immediately via hotline (+84) 0822 120 555 or (+84) 0972 249 555 for guidance on sample collection, receiving results, and timely consultation to protect the safety of your livestock.
6. Prevention of Classical Swine Fever
a. Disease Prevention Hygiene
Maintain the farm always clean, cool, and well-ventilated; periodically spray disinfectants with products such as Five-BGF, Five-B.K.G, Five-Iodine, Five-Perkon 3S,… to kill pathogens and protect the livestock.
b. Disease Prevention Vaccine
Inject Five-CSF vaccine to prevent Classical Swine Fever:
- Suckling piglets: 1st dose at 2–5 weeks old; 2nd dose about 2–3 weeks after the 1st dose.
- Replacement gilts: Inject 2–3 weeks before mating.
- Pregnant sows: Inject 3–4 weeks before farrowing.
- Breeding boars: Inject periodically every 6 months to maintain immunity.

7. Treatment of Classical Swine Fever
The disease is caused by a virus and has no specific medicine. When the disease is detected, the following control measures must be applied immediately:
- Isolate sick pigs; if the prognosis is poor, cull immediately to prevent spreading.
- At the same time, spray disinfectants, detoxify, and sanitize the farm once a day with solutions such as Five-Iodine, Five-B.K.G, Five-BGF, or Five-Perkon 3S.

*Entire Herd:
- Vaccination: Use Five-CSF vaccine for the whole herd, repeat the 2nd dose after 1 month.
- Enhance resistance: Use Five-Anti Virus or Beta-Glucan.C, treatment course 7–10 days.
- Electrolyte supplementation & fever reduction: Use Five-Cam Cum, Five-Lyte Oral, Five-No Stress Super.
- Antibiotics for secondary infections: Mix into feed products such as Five-Amoxcin Super, Five-Paflo, Five-Doxcolis Super, Five-Colisuper, Five-BMD 50%, Five-Berin.H, …
- Liver and kidney detoxification with one of the following products: Five-Acemin.B12, Five-Orgamin,…
- Supplement feed with probiotics, enzymes, and vitamins to help pigs digest and absorb feed well, prevent diarrhea and recover quickly, such as Five-Prozyme 5way, Five-Enzym, Five-Orgacid, B.comlex-K&C, Five-Aminovit super,… Treatment course 3–5 days.
Frequently Asked Questions:
1. What is Classical Swine Fever (CSF)?
Classical Swine Fever (CSF) is a dangerous contagious disease caused by the CSF virus belonging to the Flaviviridae family, Pestivirus genus. The disease spreads quickly, has a high mortality rate, causes severe damage to the pig farming industry.
2. How does Classical Swine Fever spread?
The CSF virus can be transmitted through:
- The digestive tract (eating feed or drinking water contaminated with the pathogen).
- The respiratory tract (air, dust in the pigpen).
- From sow to piglets via the placenta.
- Through semen during artificial insemination.
- Humans and farming tools are acting as intermediaries spreading the virus.
3. Is there a treatment for Classical Swine Fever?
CSF has no specific medicine. When the disease is detected, it is necessary to:
- Isolate or cull severely sick pigs.
- Regularly detoxify and disinfect the farm.
- Vaccinate healthy pigs to contain the outbreak.
4. How should the vaccine for Classical Swine Fever be administered?
Vaccination schedule with Five-CSF vaccine:
- Suckling piglets: 1st dose at 2–5 weeks old, repeat after 2–3 weeks.
- Replacement gilts: Inject 2–3 weeks before mating.
- Pregnant sows: Inject 3–4 weeks before farrowing.
- Breeding boars: Inject periodically every 6 months.
5. How to effectively prevent Classical Swine Fever?
Preventive measures:
- Keep the farm always clean, cool, and well-ventilated; periodically spray disinfectants such as Five-BGF, Five-B.K.G, Five-Iodine, Five-Perkon 3S.
- Vaccinate with Five-CSF vaccine according to the schedule.
- Supplement Beta-Glucan.C, Five-Anti Virus to enhance resistance.
- Manage feed and water sources, avoid contact between healthy pigs and pigs suspected of infection.