Introduction
African swine fever (ASF) is caused by African swine fever virus (ASFV),
a large double-stranded DNA virus, and the sole member of the genusAsfivirus within the Asfarviridae family (Alonso et al.,
2018). African swine fever usually causes an exceptionally high
lethality in domestic pigs and Eurasian wild boar and is a notifiable
disease according to the World Organization for Animal Health (OIE).
Following its introduction to Georgia in 2007, ASFV spread successively
through neighboring countries in the Trans-Caucasian region to several
parts of Europe and Asia (Dixon, Stahl, Jori, Vial, & Pfeiffer, 2020).
Since the virus reached China in 2018 (Zhou et al., 2018), millions of
pigs were culled and effects on the global pork market were severe.
First cases of ASF in Germany in 2020 (Sauter-Louis et al., 2020) sent
another shockwave through the industry, as trade restrictions on pork
took hold even as only wild boar are affected until now. With neither
treatment nor a licensed vaccine available to date, strategies to fight
the disease have to rely solely on strict sanitary measures, an early
and effective diagnosis and the culling of affected herds (Blome,
Franzke, & Beer, 2020). For the wild boar situation, fencing, adapted
hunting and hunting rest practices, trapping, incentives for carcass
search and removal, as well as a general reduction of the wild boar
populations have been implemented (Busch et al., 2021; Chenais et al.,
2019; EFSA et al., 2018).
The OIE lists conventional and real-time PCR assays, virus isolation and
fluorescent antibody tests as proven and reliable diagnostic methods for
the detection of virus genome or antigen (OIE, 2019). However, these
methods are rather time consuming and require laboratory conditions.
During its spread through Europe and Asia, ASF has affected countries
with scarce infrastructure and limited laboratory capacities. Even if
routine laboratory diagnosis is established, infected wild boar could
succumb in remote forest areas, far from centralized testing facilities.
With the effectiveness of disease control measures relying on a timely
implementation after an outbreak (Sanchez-Vizcaino, Mur, &
Martinez-Lopez, 2012) and laboratory analysis being rather
cost-intensive, questions upon the utility point-of-care (POC) assays,
possibly even to replace laboratory testing, have arisen.
Epidemiological investigations can also benefit from the availability of
an effective POC test, e.g. when culling measures take hold in an
outbreak scenario and the status of individual animals or farms is of
scientific interest for back tracing of transmission factors. The
INGEZIM ASFV CROM Ag LFA (Sastre et al., 2016) commercialized by
Eurofins Technologies Ingenasa is designed for the diagnosis of ASFV
antigen in blood under field conditions, possibly suiting these
scenarios.
Rather promising results were obtained in previous studies under
laboratory conditions and when sample quality was ideal or close to
ideal (Pikalo et al., 2021; Pikalo et al., 2020). Here, we aimed to
assess the applicability under field conditions with a total of 237
blood samples of different origins. These investigations complement the
previous studies on the lateral flow assay with a practice-orientated
approach, simulating the possible application as POC test for antigen
detection in carcasses when possible effects of decomposition have
occurred. The results of the antigen LFA were compared to OIE listed
qPCR diagnosis, and the resulting sensitivity and specificity were
evaluated for assessment of the practicability of the on-site test under
realistic conditions with real field samples.