African swine fever (asf) control and repopulation strategies in tropical condition: effectiveness of cleaning and disinfection protocols.

چکیده اصلی

African swine fever virus (ASFV) continues to challenge the pig industry worldwide, with persistence in farm environments posing a major obstacle to repopulation. This study evaluated ASFV DNA persistence and farm-level biosecurity practices on pig farms in Malaysia following cleaning and disinfection (C&D) protocols after an ASF outbreak in the farm. A structured biosecurity survey covering 5 domains (personnel entry, farm structure, C&D, carcass disposal management and water source) was conducted across 37 farms, comprising both ASF-affected and unaffected farms, while environmental swab sampling was performed on six ASF-positive farms that had undergone at least 3 months of downtime and intensive decontamination. All swab samples (n = 98) were tested using real-time polymerase chain reaction (qPCR). ASFV DNA was detected at five out of six sampled farms, with farm-level positivity ranging from 7.1% (Farm C) to 100% (Farm D), whereas Farm A achieved a completely negative qPCR results across all 25 swabs. Median Ct-values of positive samples ranged from 33.4 (Farm B; IQR 32.4-33.8) to 37.3 (Farm C), and differed significantly between farm (H = 24.83, p < 0.05). Farm B retained significantly lower Ct values than Farm D (p = 0.008) and Farm F (p = 0.002). Although pairwise comparisons between individual farms did not reach statistical significance due to the limited sample size and conservative post-hoc adjustments, the complete absence of detectable ASFV DNA observed at Farm A and near-complete absence at Farm C-the only site utilizing supplemental heat treatment - were both associated with the consistent application of foaming agent (wet cleaning), an explicit drying step, and treated water. These findings provide the first field-based evidence that, under tropical Malaysian conditions, ASFV DNA persists despite rigorous chemical treatment and suggests that the combination of mechanical cleaning, environmental drying, treated underground water and targeted heat application may enhance the reduction of detectable ASFV DNA and strengthen biosecurity for repopulation.

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