Effect of strain and inoculation dose of classical swine fever virus on within-pen transmission.

Weesendorp, E.; Backer, J.A.; Stegeman, J.A.; Loeffen, W.L.A.


To improve the understanding of the dynamics and options for control of classical swine fever (CSF), more quantitative knowledge is needed on virus transmission. In this study, virus excretion and within-pen transmission of a strain of low, moderate and high virulence were quantified. Furthermore, the effect of inoculation dose on excretion and transmission were studied. The transmission was quantified using a stochastic susceptible-exposed-infectious-recovered (SEIR) model. Five transmission trials were conducted with ten pigs each. In each trial, three pigs were inoculated with the low virulent strain Zoelen, a low (102 TCID50), middle (103 TCID50), or high dose (105 TCID50) of the moderately virulent strain Paderborn, or the highly virulent strain Brescia. The other seven pigs in each trial served as contact pigs. None of the pigs inoculated with the low dose of the Paderbom strain were infected. When it was assumed that the infectiousness of the pigs coincided with virus isolation positive oropharyngeal fluid and/or faeces, no significant differences in transmission rate ß and basic reproduction ratio R0 between the high inoculation dose of the Paderbom strain (ß = 1.62/day, R0 = 35.9) and the Brescia strain (ß = 2.07/day, Ro = 17.5) were observed. When the middle dose of the Paderbom strain was used for inoculation, the ß (5.38/day) was not significantly higher than the Brescia strain or the high inoculation dose of the Paderborn strain, but the Ro (148) was significantly higher. Infection with the Zoelen strain resulted in a significantly lower ß and Ro (ß = 0/day, Ro = 0) than the other strains