Evaluation of the risk factors contributing to the African swine fever occurrence in Sardinia, Italy

This study assesses the relation between hypothesized risk factors and African swine fever virus (ASFV) distribution in Sardinia (Italy) after the beginning of the eradication program in 1993, using a Bayesian multivariable logistic regression mixed model. Results indicate that the probability of ASFV occurrence in Sardinia was associated to particular socio-cultural, productive and economical factors found in the region, particularly to large number of confined (i.e., closed) farms (most of them backyard), high road density, high mean altitude, large number of open fattening farms, and large number of pigs per commune. Conversely, large proportion of open farms with at least one census and large proportion of open farms per commune, were found to be protective factors for ASFV. Results suggest that basic preventive and control strategies, such as yearly census or registration of the pigs per farm and better control of the public lands where pigs are usually raised, together with endanced effords of outreach and communication with pig producers should help in the success of the eradication program for ASF in the Island. Methods and results presented here will inform decision making to better control and eradicate ASF in Sardinia and in all those areas with similar management and epidemiological conditions.

Assessment of an oral Mycobacterium bovis BCG vaccine and an inactivated M. bovis preparation for wild boar in terms of adverse reactions, vaccine strain survival, and uptake by nontarget species

Wildlife vaccination is increasingly being considered as an option for tuberculosis control. We combined data from laboratory trials and an ongoing field trial to assess the risk of an oral Mycobacterium bovis BCG vaccine and a prototype heat-inactivated Mycobacterium bovis preparation for Eurasian wild boar (Sus scrofa). We studied adverse reactions, BCG survival, BCG excretion, and bait uptake by nontarget species. No adverse reactions were observed after administration of BCG (n = 27) or inactivated M. bovis (n = 21). BCG was not found at necropsy (175 to 300 days postvaccination [n = 27]). No BCG excretion was detected in fecal samples (n = 162) or in urine or nasal, oral, or fecal swab samples at 258 days postvaccination (n = 29). In the field, we found no evidence of loss of BCG viability in baits collected after 36 h (temperature range, 11°C to 41°C). Camera trapping showed that wild boar (39%) and birds (56%) were the most frequent visitors to bait stations (selective feeders). Wild boar activity patterns were nocturnal, while diurnal activities were recorded for all bird species. We found large proportions of chewed capsules (29%) (likely ingestion of the vaccine) and lost baits (39%) (presumably consumed), and the proportion of chewed capsules showed a positive correlation with the presence of wild boar. Both results suggest proper bait consumption (68%). These results indicate that BCG vaccination in wild boar is safe and that, while bait consumption by other species is possible, this can be minimized by using selective cages and strict timing of bait deployment.