Viability of African Swine Fever Virus with the Shallow Burial with Carbon Carcass Disposal Method

Abstract

African swine fever (ASF) is a highly contagious swine disease with high mortality. In many countries, culling pigs infected and exposed to the ASF virus is mandatory to control the disease, which poses a real challenge in the disposal of large numbers of carcasses during ASF outbreaks. Shallow burial with carbon (SBC) Thanks ew mortality disposal method developed from deep burial and composting. The present study investigates the effectiveness of SBC in disposing of ASF virus-infected pigs. The real-time PCR results showed that DNA of the ASF virus was still detected in bone marrow samples on day 56, while the virus isolation test revealed that the infectious ASF virus was destroyed in both spleen and bone marrow samples on day 5. Interestingly, decomposition was found to occur rapidly in these shallow burial pits. On day 144, only large bones were found in the burial pit. In general, the results of this study indicated that SBC is a potential method for the disposal of ASF-infected carcasses; however, further studies are needed to provide more scientific evidence for the efficacy of SBC in different environment conditions.

Keywords: ASF virus; above ground burial; decomposition; inactivation; shallow burial with carbon.

Figure 1

Four swine carcasses were placed in each SBC pit, facing the same direction.

Figure 2

Pathology of ASF-infected swine carcasses used in this study. (a) Hemorrhagic lymph node. (b) Enlarged hemorrhagic spleen.

Figure 3

Spleen (a) and bone marrow (b) were extracted from buried swine carcasses.

Figure 4

Hemadsorption in ASF virus-infected cells. Arrow indicates HAD rosettes.

Figure 5

Temperature profile of SBC pits. Square dot line (), long dash line (), solid line () is air tempearture, soil temperature, and core temperature, respectively.

Figure 6

Scatter plot of Ct of post-burial spleen and femur bone marrow samples. Green dots are the Ct values of femur bone marrow samples. Orange triangles are the Ct values of spleen samples.

Figure 7

Plot of log₁₀ of the ASFv concentration for spleen samples tested with 99.8% confidence and prediction intervals. Green dots are the raw cell culture data. The green line is the best fit simple linear regression line for log₁₀ of the ASFv concentration regressed on days since burial. The pink shaded area is the 99.8% confidence interval for the best fit regression line. The dashed blue lines represent the lower and upper bounds of the 99.8% prediction interval for the plotted regression line. The orange dot is the estimated mean number of days to log₁₀(0) ASFv concentration, equivalent to 1 ASFv particle. The orange line or interval around the orange dot is the 99.8% prediction interval for the estimated number of days to log₁₀(0) ASFv concentration.

Figure 8

Plot of days since burial vs. log₁₀ of the ASFv concentration for femur bone marrow samples tested with 99.8% confidence and prediction intervals. Green dots are the raw cell culture data. The green line is the best fit simple linear regression line for log₁₀ of the ASFv concentration regressed on days since burial. The pink shaded area is the 99.8% confidence interval for the best fit regression line. The dashed blue lines represent the lower and upper bounds of the 99.8% prediction interval for the plotted regression line. The orange dot is the estimated mean number of days to log₁₀(0) ASFv concentration, equivalent to 1 ASFv particle. The orange line or interval around the orange dot is the 99.8% prediction interval for the estimated number of days to log₁₀(0) ASFv concentration.

Figure 9

The decomposition of carcasses in SBC pits at day 1, 3, 5, 7, 14, 21, 28, 35, 56, and 144.

Figure 9

The decomposition of carcasses in SBC pits at day 1, 3, 5, 7, 14, 21, 28, 35, 56, and 144.