In this study we quantified the rate at which classical swine fever had been transmitted by several different types of inter-herd contact during the 1997–8 epidemic in The Netherlands. During that epidemic 428 CSFV-infected pig herds were detected, 403 of which were included in this study. The estimated rates of transmission were 0·065 per shipment of live pigs, 0·011 per contact by a pig transportation lorry, 0·0068 per person contact, 0·0007 per dose of semen, 0·0065 per contact with a potentially contaminated pig assembly point, 0·027 per week per infected herd within a radius of 500 metres and 0·0078 per week per infected herd at a distance between 500 and 1000 metres. These transmission rates can be used to optimize the strategy to stop future epidemics of CSF in The Netherlands. In addition, the analysis demonstrated in this paper, can be used to quantify CSFV transmission rates from other epidemics.

We present a method to estimate basic reproduction ratio R0 from transmission experiments. By using previously published data of experiments with Classical Swine Fever Virus more extensively, we obtained smaller confidence intervals than the martingale method used in the original papers. Moreover, our method allows simultaneous estimation of a reproduction ratio within pens R0w and a modified reproduction ratio between pens R′0b. Resulting estimates of R0w and R′0b for weaner pigs were 100 (95% CI 54·4–186) and 7·77 (4·68–12·9), respectively. For slaughter pigs they were 15·5 (6·20–38·7) and 3·39 (1·54–7·45), respectively. We believe, because of the smaller confidence intervals we were able to obtain, that the method presented here is better suited for use in future experiments.

Foot-and-mouth disease virus (FMDV) can spread by a variety of mechanisms, including, under certain circumstances, by the wind. Simulation models have been developed to predict the risk of airborne spread of FMDV and have played an important part in decision making during emergencies. The minimal infectious dose of FMDV for different species by inhalation is an important determinant of airborne spread. Whereas the doses for cattle and sheep have been quantified, those for pigs are not known. The objective of the study was to obtain that data in order to enhance the capability of simulation models. Under experimental conditions, forty pigs were exposed individually to naturally generated aerosols of FMDV, strain O1 Lausanne. The results indicated that doses under 100 TCID50 failed to infect pigs but doses of approximately 300 TCID50 caused short-term sub-clinical infection. The calculations suggested that a dose of more than 800 TCID50 is required to cause infection and typical disease.

Foot-and-mouth disease virus (FMDV) can be spread by a variety of mechanisms, including wind. Simulation models, developed to predict the risk of airborne spread, have played an important part in decision making in some outbreaks. The amount of airborne virus excreted as well as the minimal infectious dose (MID) of FMDV for different species are important determinants of airborne spread. The objective of this study was to obtain data for the O1 Lausanne, O SKR 2000 and O UKG 2001 strains of FMDV to enhance the capability of such models. Pigs were exposed to naturally generated aerosols of the three strains using an experimental design which delivered high doses of the two strains O1 Lausanne and O SKR 2000 over a short period, or of the O UKG 2001 strain over an extended period. The average excretion of the O1 Lausanne strain was 106·4 TCID50 per pig per hour. The excretion of the O SKR 2000 strain averaged 105·8 and the O UKG 2001 strain 106·1 TCID per pig per 24 h. The results show that the previous estimate of ‘above’ 800 TCID50 as the MID50 for the O1 Lausanne strain is a considerable under-estimate and that the real dose may be as high as 6000 TCID50. A dose of around 650 TCID50 of the O SKR 2000 strain failed to infect any pigs. Thus, the aerosol MID50 for pigs for this isolate is at least 1000 TCID50 and likely to be as high or higher than the O1 Lausanne strain. The exposure of pairs of recipient pigs kept physically separated from donor pigs in a series of rooms to aerosol exposure doses of the O UKG 2001 strain of around 50 TCID50 per min for 24–48 h failed to infect any of eight pigs. Thus, the present experiment confirms our previous findings [1, 2] that pigs, compared to cattle and sheep, are relatively resistant to infection with airborne FMDV.

The relationships between the inhaled dose of foot and mouth disease virus and the outcomes of infection and disease were examined by fitting dose-response models to experimental data. The parameters for both the exponential and beta-poisson models were estimated using maximum likelihood and Bayesian methods. The median probability of infection given a single inhaled TCID50 was estimated to be 0·031 with 95% Bayesian credibility intervals (CI) of 0·018–0·052 for cattle, and 0·045 (CI = 0·024–0·080) for sheep. These estimates were used to construct dose-response curves and uncertainty distributions for use in quantitative risk assessments.

Salmonella enterica serovar Abortusovis is one of the most common pathogens responsible for abortion in sheep. In Iran, the spread of Abortusovis is highly dependent on the nomadic life style. In this study we performed IS200 fingerprinting to identify the clonal lines circulating in Iran. All the isolates contained 4 or 5 copies of the transposon and could be classified in 4 genotypes. A single genotype was highly prevalent and very likely it has circulated in Iran since 1970. All the isolates showed a high degree of relatedness.

Thirty Japanese clinical isolates of Mycobacterium tuberculosis were analysed by pyrazinamide susceptibility testing and pyrazinamidase assay, as well as polymerase chain reaction for single-strand conformational polymorphism and direct sequencing of the gene encoding pyrazinamidase (pncA). All sensitive isolates showed pyrazinamidase activity and a wild-type pncA gene, but three resistant isolates had pncA gene mutations and lacked pyrazinamidase activity. The latter isolates showed a minimum inhibitory concentration of at least 100 mg/l by the 7H10 agar proportion method and 400 mg/l by the 7H9 liquid medium method. Isolate 28 showed T-to-C change at position 11, leading to Leu4→Ser substitution; isolate 29 had an 8-bp deletion from position 382; and isolate 30 had A-to-C change at position 29, leading to Gln10→Pro substitution. The deletion has not been described previously. This is the first demonstration of pncA gene mutations in PZA-resistant M. tuberculosis strains isolated from Japanese patients.

Cattle were vaccinated with a recombinant capripox-rinderpest vaccine designed to protect cattle from infection with either rinderpest virus (RPV) or lumpy skin disease virus (LSDV). Vaccination did not induce any adverse clinical responses or show evidence of transmission of the vaccine virus to in-contact control animals. Approximately 50% of the cattle were solidly protected from challenge with a lethal dose of virulent RPV 2 years after vaccination while at 3 years approx. 30% were fully protected. In the case of LSDV, all of 4 vaccinated cattle challenged with virulent LSDV at 2 years were completely protected from clinical disease while 2 of 5 vaccinated cattle were completely protected at 3 years. The recombinant vaccine showed no loss of potency when stored lyophylized at 4 °C for up to 1 year. These results indicate that capripoxvirus is a suitable vector for the development of safe, effective and stable recombinant vaccines for cattle.

Page 223, Table 1. ‘V2 GACTGCGTCAGTGAGGTT’

Should read ‘V5 GACTCTTCCATCTGCCG’

Page 226, Reference 1. ‘1997’ should read ‘1977’

Page 227, Reference 17. Replace with ‘Kobayashi K. Detection of enterohemorrhagic Escherichia coli using PCR. J Clin Microbiol 1991; 18: 507–13.’