Molecular contamination of an animal facility during and after African swine fever virus infection

Abstract

Introduction: The molecular contamination of an animal facility was investigated during and after an infection with highlypathogenic African swine fever virus (ASFV) among domestic pigs. The investigation evaluated the risk of indirect transmissionof the disease and indicated points that may facilitate cleaning and disinfection processes. Material and Methods: Six domesticpigs were infected oronasally with the highly pathogenic Georgia 2007 strain. Environmental samples from the floors, walls, rubberfloor mats, feeders, drinkers, high-efficiency particulate-absorbing filter covers and doors were collected 7 days post infection(dpi), 7 days later and 24 h after disinfection of the facility. The samples were investigated by real-time PCR and in vitro assays tofind genetic traces of ASFV and infectious virus. Results: Typical clinical outcomes for ASF (i.e. fever, apathy, recumbency andbloody diarrhoea) were observed, and all animals died or required euthanasia before or at 9 dpi. No infectious virus was found inenvironmental samples at the sampling time points. Genetic traces of ASFV were found in all locations except the doors. The initialvirus load was calculated using real-time PCR threshold cycle values and was the highest at the drain. A statistically significantdecrease of virus load over time was found on non-porous surfaces mechanically cleaned by water (the floor and drain).Conclusion: The gathered data confirmed different routes of virus excretion (oral and nasal, faeces and urine, and aerosol) andshowed virus locations and different initial concentrations in the animal facility. Maintaining the facility with mechanical cleaningand using personal protection (gloves) and hand disinfection may efficiently minimise the risk of further virus spread. Togetherwith the results of previously published studies, the present investigations’ failure to isolate infectious virus may suggest that ifstable environmental conditions are assured, the time needed before the introduction of new herds into previously ASF-affectedfarm facilities could be shortened and in this way the economic losses caused by the disease outbreak mitigated.