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

Abstract

-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 (10 2 TCID 50 ), middle (10 3.5 TCID 50 ), or high dose (10 5 TCID 50 ) 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 Paderborn 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 b and basic reproduction ratio R 0 between the high inoculation dose of the Paderborn strain (b = 1.62/day, R 0 = 35.9) and the Brescia strain (b = 2.07/day, R 0 = 17.5) were observed. When the middle dose of the Paderborn strain was used for inoculation, the b (5.38/day) was not significantly higher than the Brescia strain or the high inoculation dose of the Paderborn strain, but the R 0 (148) was significantly higher. Infection with the Zoelen strain resulted in a significantly lower b and R 0 (b = 0/day, R 0 = 0) than the other strains.classical swine fever / transmission parameter / virus excretion / within-pen transmission

Factors affecting the infectivity of tissues from pigs with classical swine fever: Thermal inactivation rates and oral infectious dose

“…Whilst this route is not an exact representation of what might happen if an animal were to eat an infected pork product, it allowed inoculation of accurate dilution of doses in a standard volume, which would not have been possible by attempting to feed pigs with tissues from infected donor animals. The dose required to infect 50% of pigs via this oral route was much higher than via intranasal inoculation (Farez and Morley, 1997;Weesendorp et al, 2009a). Although, dose response data have not been published on oral live attenuated CSFV vaccines administered using blister baits, our data are in accordance with the stated dose require for oral vaccination (Kaden et al, 2010).…”

“…Virulence can also affect the dose required to instigate infection. For example, a low intranasal dose of moderately virulent CSFV failed to instigate infection whereas all animals inoculated with a similar dose of highly virulent virus became infected (Weesendorp et al, 2009a). We therefore determined the oral ID 50 of both a virulent and moderately virulent CSFV.…”

Transfection of RNA from Organ Samples of Infected Animals Represents a Highly Sensitive Method for Virus Detection and Recovery of Classical Swine Fever Virus

“…To our knowledge, the minimal infectious dose of highly virulent CSFV strain Koslov has not been determined so far. However, previous studies have shown that an inoculation dose between ~10 2.5 and 10 3 TCID 50 / animal of virulent CSFV strains (Brescia and Alfort/187) resulted in animal infection and disease [ 34 , 35 ] and a dose of 200 TCID 50 / animal was used for challenge infection with CSFV Koslov [ 36 ]. Based on these facts, a dose of 10 3 TCID 50 / animal of the highly virulent strain Koslov can be expected to be above the minimal infectious dose.…”

Primary Newcastle disease vaccination of broilers: comparison of the antibody seroresponse and adverse vaccinal reaction after eye–nose drop or coarse spray application, and implication of the results for a previously developed coarse dry powder vaccine

“…Moreover, the amount of virus shed by the inoculated chickens in the period between inoculation and contact infection of the pen mates also differed between various dose groups. Dose-dependent excretion and transmission of classical swine fever virus in pigs was also demonstrated (Weesendorp et al, 2009). Likely, the dynamics of the ND vaccine virus infection in chickens is dose-dependent too, implying a dose-dependency for the course of the increased colibacillosis susceptibility.…”

“…Eye-nose drop vaccinations using decreasing ND vaccine virus doses were accompanied by gradually increasing colibacillosis lesion scores, which is a novel finding. An explanation is that the dynamics of the vaccine virus infection is likely dose-dependent as was shown for viruses other than ND virus (Weesendorp et al, 2009;Spekreijse et al, 2011). Consequently, the course of the colibacillosis susceptibility of the broilers following ND vaccination might be dosedependent too, resulting in higher susceptibility at seven days after vaccination using lower vaccine virus doses ( Figure 2).…”