Comparison of diaphragm meat juice and muscle swab samples to spleen and spleen swab samples for the detection of African swine fever viral nucleic acid

Abstract

Use of meat juice and muscle swabs at slaughterhouses may provide an easy-to-collect sample for African swine fever (ASF) surveillance. Meat juice has been experimentally shown to be a reliable sample for the detection of ASF virus (ASFV). We compared the detection of ASFV nucleic acid from diaphragm meat juice, diaphragm muscle swab, spleen, and spleen swabs from pigs with signs of ASFV infection at slaughterhouses around Kampala, Uganda. Pigs with ≥ 2 clinical or pathology signs at the time of slaughter had a spleen sample, spleen swab, diaphragm muscle sample, and diaphragm muscle swab collected. Meat juice was collected from muscle samples through a freeze–thaw cycle. Each sample was tested individually, and 72 spleen, meat juice, and muscle swab sample pools of 4 negative and 1 positive sample were tested, as well. Standard operating procedures from the USDA–Foreign Animal Disease Diagnostic Laboratory for viral DNA extraction and real-time PCR (rtPCR) were used. Of the 493 pigs evaluated, we classified as positive 357 (72.4%) diaphragm meat juice samples, 218 (44.2%) diaphragm muscle swabs, 247 (50.1%) spleen samples, and 241 (48.9%) spleen swabs. All spleen sample pools were positive (72 of 72; 100%), as were 71 of 72 (98.6%) meat juice pools and 67 of 72 (93.1%) muscle swab pools. Meat juice samples provided a reliable sample type for the detection by rtPCR of ASFV in pigs with natural infections.

Development of Highly Sensitive Conventional PCR for African Swine Fever Virus Diagnosis in East Nusa Tenggara (NTT) Province

“…This is because of the large number of Kupffer cells available as ASFV target cells (Blome et al, 2020). The PCR band for the spleen was thick (Okwasiimire et al, 2023). This is because the spleen has abundant macrophages and monocytes.…”

African Swine Fever Diagnosis in Africa: Challenges and Opportunities

“…Pigs that are infected but not yet showing clinical signs and are active may be shedding ASF in oral fluid therefore applying this method at the first sign of ASF in a herd could assist rapid confirmation [ 41 , 42 , 43 ]. Information exists on other samples that may be required for trade purposes and surveillance and can easily be obtained, such as meat and meat exudate [ 44 , 45 , 46 , 47 , 48 ]. The concurrence between positive spleen and muscle samples in the Ugandan study [ 46 ] indicated that viraemic pigs were presented for slaughter, which is often the case during ASF outbreaks, when farmers rapidly sell their pigs to limit financial losses, as has been reported previously [ 49 , 50 , 51 , 52 , 53 , 54 ].…”

“…Information exists on other samples that may be required for trade purposes and surveillance and can easily be obtained, such as meat and meat exudate [ 44 , 45 , 46 , 47 , 48 ]. The concurrence between positive spleen and muscle samples in the Ugandan study [ 46 ] indicated that viraemic pigs were presented for slaughter, which is often the case during ASF outbreaks, when farmers rapidly sell their pigs to limit financial losses, as has been reported previously [ 49 , 50 , 51 , 52 , 53 , 54 ]. This practice poses a risk for the spread of ASF but does offer opportunities for ASF surveillance and earlier diagnosis at points of sale.…”