Classical swine fever: Causes, preventive measures

Classical swine fever is a highly contagious viral disease in pigs that can lead to high fever, bleeding under the skin and in internal organs, and a very high mortality rate if not detected and treated promptly. In this article, Vemedim will provide information on the transmission mechanism, clinical signs, and effective disease prevention solutions to help farmers proactively protect their herds. Let’s take a look!

Causes of the disease and transmission mechanism of classical swine fever

Classical swine fever (CSF) is one of the most important infectious diseases in pigs, causing severe losses to the livestock industry. The disease is characterized by rapid spread, high fever, a high rate of illness and death in affected areas, typical hemorrhagic lesions, and susceptibility in pigs of all ages. In Vietnam, swine fever has caused serious economic losses for many years.

The causative virus

Classical swine fever is caused by a virus in the family Flaviviridae, genus Pestivirus, an RNA virus. CSF virus is highly resistant:

It can survive for many years in frozen meat.
It can survive for 6 months in salted or smoked meat.
It can survive for months in feces, waste, and barn bedding.

Transmission route

The virus spreads mainly through direct transmission from sick pigs to healthy pigs via the digestive tract or upper respiratory tract. The infection process of classical swine fever occurs as follows:

The virus enters through the mouth, nose, or contact with infected secretions.
The virus enters phagocytes and moves to lymph nodes such as the tonsils and pharyngeal lymph nodes, where it multiplies rapidly.
After 24 hours, the virus enters the bloodstream and infects vascular endothelial cells.
On days 3–4, the virus spreads to parenchymal organs, multiplies, and causes a second viremia on days 5–6.

In addition, CSF virus can also spread through:

The placenta, causing abortion, premature birth, or piglets born already infected with the virus.
Urine, tears, nasal discharge, straw, meat wash water, and the intestines of sick or dead pigs.
Vectors such as rats, insects, birds, dogs, cats, humans, vehicles, and livestock equipment.

The virus is not completely eliminated without proper barn sanitation measures, making the disease easy to erupt under intensive farming conditions.

*The classical swine fever virus is transmitted directly from sick pigs to healthy pigs through the digestive or respiratory route*

>> See also:

Clinical signs of pigs infected with classical swine fever

The disease has an incubation period of 4–8 days and can present in three main forms: peracute, acute, and chronic. Specifically:

Peracute form

Usually seen in piglets, with rapid death within 3–7 days.
In many cases, pigs die without obvious symptoms.
High fever of 41–43°C, bright red skin in the groin and lower abdomen, quickly turning purple.
Pigs may cough up blood and die within just 1–2 days.

Acute form

Affected pigs are lethargic, pile up together, lose appetite, and have a high fever of 41–42°C.
Initial symptoms: conjunctivitis, red eyes, discharge that is gray or dark brown.
Small pinhead-like hemorrhages under the skin, clustering into patches, typically on the ears, snout, and abdomen.
Stool is initially constipated, then becomes loose and foul-smelling.
Some pigs vomit, breathe heavily, have difficulty breathing, lose balance, convulse, or become paralyzed in the hind legs (neurological form).
Pregnant sows may abort, deliver stillborn piglets, or give birth to weak piglets that die early.

Chronic form

Usually seen in 2–3-month-old pigs, lasting 30–90 days.
Pigs are constipated, then develop diarrhea, stop eating or eat/drink abnormally, walk unsteadily, and hide in the pen.
Skin hemorrhages change from red to purple, with skin necrosis and peeling in patches.
When combined with other diseases such as paratyphoid and pasteurellosis, the disease becomes more severe.

*Depending on the disease form, the symptoms in pigs with classical swine fever also vary*

How to diagnose classical swine fever

Diagnosis of this disease is mainly based on clinical signs, lesions, and epidemiology, specifically:

Symptoms: high fever, constipation followed by diarrhea, loss of appetite, red eyes, discharge.
Lesions: skin hemorrhages, enlarged lymph nodes, kidney and spleen congestion, intestinal ulcers.
Antibiotics are ineffective.
The disease spreads widely, and all age groups are at risk.

*Classical swine fever is mainly diagnosed through observation of symptoms, lesions, and epidemiology*

Treatment and control of classical swine fever

Currently, there is no specific treatment for CSF. Serum may provide support, but it is costly and not economically suitable. The most effective disease prevention method is vaccination and biosecurity.

Vaccination

Piglets: first dose at 3 weeks of age, booster at 65 days (in areas where the disease is common). If piglets have passive antibodies from the sow, vaccinate at 5 weeks of age (in disease-free areas).
Replacement gilts: vaccinate 1–2 months before breeding.
Sows: vaccinate after weaning or before breeding.
Boars: vaccinate twice a year.

Sanitation and biosecurity

Sick pigs must be isolated away from healthy herds; feces and organs from sick pigs should be disposed of by deep burial + lime powder, and dead pigs must be destroyed.
Use artificial insemination to limit disease spread.
Control transport, slaughter, and timely outbreak response.
Carry out barn and equipment sanitation, and disinfect regularly with Vemedim Altacid.

*The most effective way to prevent classical swine fever is vaccination with the appropriate dose for the pig’s age*

To effectively control classical swine fever, farmers need to strictly implement measures such as rigorous management of breeding pigs, barn sanitation and disinfection, and more. When all the steps guided by Vemedim above are proactively carried out, farmers can minimize losses, protect their herds, and improve livestock production efficiency.