Superficial Inguinal Lymph Nodes for Screening Dead Pigs for African Swine Fever.

Kalhari Bandara Goonewardene,Aruna Ambagala,Sandra Blome,Melissa Goolia,Chukwunonso Onyilagha,Van Phan Le

doi:10.3390/v14010083

Abstract

African swine fever (ASF) has spread across the globe and has reached closer to North America since being reported in the Dominican Republic and Haiti. As a result, surveillance measures have been heightened and the utility of alternative samples for herd-level monitoring and dead pig sampling have been investigated. Passive surveillance based on the investigation of dead pigs, both domestic and wild, plays a pivotal role in the early detection of an ASF incursion. The World Organization for Animal Health (OIE)-recommended samples for dead pigs are spleen, lymph nodes, bone marrow, lung, tonsil and kidney. However, obtaining these samples requires opening up the carcasses, which is time-consuming, requires skilled labour and often leads to contamination of the premises. As a result, we investigated the suitability of superficial inguinal lymph nodes (SILNs) for surveillance of dead animals. SILNs can be collected in minutes with no to minimum environmental contamination. Here, we demonstrate that the ASF virus (ASFV) genome copy numbers in SILNs highly correlate with those in the spleen and, by sampling SILN, we can detect all pigs that succumb to highly virulent and moderately virulent ASFV strains (100% sensitivity). ASFV was isolated from all positive SILN samples. Thus, sampling SILNs could be useful for routine surveillance of dead pigs on commercial and backyard farms, holding pens and dead on arrival at slaughter houses, as well as during massive die-offs of pigs due to unknown causes.

Highlights

African swine fever (ASF) is undoubtedly the most critical pig disease affecting the global swine industry at present [1]
In all pigs that succumbed to ASF, found dead, or euthanized as they reached a humane endpoint, ASF virus (ASFV) genomic material was detected in all three sample types—whole blood, spleen and superficial inguinal lymph nodes (SILNs) (Table 1)—except for four pigs found dead in the ASF
When all moderately virulent and highly virulent ASFV strains were considered collectively, the genome copy numbers in the spleen samples positively correlated with the SILN samples (r = 0.77), with high confidence at p < 0.0001 (Figure 2a)

Summary

Introduction

African swine fever (ASF) is undoubtedly the most critical pig disease affecting the global swine industry at present [1]. It continues to spread in Europe, Asia and sub-Saharan. One of the greatest challenges faced by ASF-free countries is detecting an ASFV incursion as quickly as possible to minimize the economic and social impact due to associated high mortality, stamping out, trade sanctions and regaining the disease-free status. For early detection of ASF, many countries have implemented surveillance programs for both domestic and wild pigs [6,7]

Methods

Results

Conclusion