Classical Swine Fever | Epidemiology

The density of pig populations as well as the presence of wild boars in certain areas are major factors influencing the epidemiology of CSF.

Most common causes of outbreaks

The probability of spreading the disease is higher in areas with higher swine population densities.

Considering that wild boar and domestic pigs are equally susceptible, endemic CSF in wild boar is an important reservoir of virus for domestic pigs. Outbreaks often start when domestic pigs come in contact with infected material originated from wild boars.

Feeding domestic pigs or wild boars with swill is an important predisposing factor for infection.

Global situation

North America – USA has been feree of CSF since the endo of the eradication program in 1978. Canada has been free since 1974. Mexico has 3 distinct areas: (i) the northern states on the border with USA plus the Yucatan peninsula are free of CSF without vaccination; (ii) the central part is designated eradication area where vaccination has been prohibited; and (iii) the southern part of the country is designated control area, where the disease is endemic and vaccination is used continuously.

Central America – Belize and Panama are free of the disease. CSF is endemic in the other countries where it is controlled by vaccination. CSF is also present in 3 Caribbean countries: Cuba, Haiti, and the Dominican Republic.

Brazil – In 1992 a program for eradication of CSF was implemented in Brazil (see map below). The program was designed to achieve eradication in a progressive way, starting in areas where the swine production is more intense. The country was divided into 3 areas: (i) southern states, which are free of the disease without vaccination; (ii) states with a relatively large swine population where CSF was still endemic and vaccination was made compulsory; and (iii) the rest of the country where swine production is not significant and vaccination was not made compulsory. CSF was absent from the southern states until 1997, when an outbreak was reported. Stringent control measurements were adopted and no other CSF cases have been reported in the southern states since then. The success of the program lead the Ministry of Agriculture to prohibit vaccination against CSF in the whole country in 1998, but that was followed by an increase in the number of outbreaks in the northeastern part of the country (see table below) and vaccination started to be used again in northeastern states except for Bahia and Sergipe in 2001. The states of Rio Grande do Sul, Santa Catarina, Paraná, Minas Gerais, and Mato Grosso do Sul have been declared free of CSF.

Map of Brazil. The following states are free of CSF: Rio Grande do Sul, Santa Catarina, Paraná, Minas Gerais, and Mato Grosso do Sul.

South American Countries other than Brazil – No cases of CSF have been reported in Uruguay since 1991, and in Chile since 1996, but CSF is still enzootic in most of the South American countries. Control programs are in place in Argentina, Brazil, Chile, Colombia, Ecuador, and Paraguay. These include vaccination, laboratory testing, stamping out (depopulation), quarantine, control of transit and import restrictions.

European Union (EU) – An official control program was established in 1980 with the goal of complete eradication of the disease from the EU, but in spite of 19 years of strict control policy, the achievement of complete eradication appears unlikely. Endemic infection of wild boars in the EU poses a major risk for outbreaks in domestic pigs. Although the incidence of CSF may be low throughout long periods of time, occasional outbreaks that become an extensive epizootic such as the epidemic centered in the Netherlands in 1997, make the control policy extremely expensive and the practicality of imposing strict control measures can become increasingly difficult.

Central and Eastern Europe (CEE) – Prohibition of vaccination has been adopted only in a few CEE countries, namely Czech Republic, Estonia, Hungary, and Poland, whereas in most of the CEE control in based on vaccination. Methods for diagnosis and control of CSF is largely dependent on the economic situation of each individual country.

Asia – Japan started an eradication program in 1996 and since then no cases of CSF have been reported. The program consisted of 3 phases: (i) during the first 2 years, control was based on vaccination; (ii) during the next 2 years a local area free of CSF was established; and (iii) the last phase with duration of 1 year, when vaccination was suspended. In contrast to Japan, outbreaks of CSF still occur regularly in most of the South-East Asian countries. The situation in mainland China and North Korea is unknown.

Australia and New Zealand – free of CSF.

Africa - unknown

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