Artificial Insemination as an Alternative Transmission Route for African Swine Fever Virus

Abstract

The rapid spread of the African swine fever virus (ASFV), causing severe disease with often high fatality rates in Eurasian suids, prevails as a threat for pig populations and dependent industries worldwide. Although advancing scientific progress continually enhances our understanding of ASFV pathogenesis, alternative transmission routes for ASFV have yet to be assessed. Here, we demonstrate that ASFV can efficiently be transferred from infected boars to naïve recipient gilts through artificial insemination (AI). In modern pig production, semen from boar studs often supplies many sow herds. Thus, the infection of a boar stud presents the risk of rapidly and widely distributing ASFV within or between countries. Daily blood and semen collection from four boars after intramuscular inoculation with ASFV strain ‘Estonia 2014’ resulted in the detection of ASFV genomes in the semen as early as 2 dpi, in blood at 1 dpi while semen quality remained largely unaffected. Ultimately, after insemination with extended semen, 7 of 14 gilts were ASFV positive by 7 days post insemination, and all gilts were ASFV positive by 35 days post insemination. Twelve out of 13 pregnant gilts aborted or resorbed at the onset of fever. A proportion of fetuses originating from the remaining gilt showed both abnormalities and replication of ASFV in fetal tissues. Thus, we present evidence for the efficient transmission of ASFV to gilts via AI and also to implanted embryos. These results underline the critical role that boar semen could play in ASFV transmission.

Composting of Wild Boar Carcasses in Lithuania Leads to Inactivation of African Swine Fever Virus in Wintertime

“…Following the PCR diagnosis at the Lithuanian NRL, the samples were tested at FLI for virus isolation to assess their infectivity. First, each sample was subjected to one blind passage in porcine peripheral blood monocytic cell (PBMC)-derived macrophages, followed by a read-out passage, as previously described [ 15 ]. For the blind passages, 5 × 10 6 PBMCs per well were seeded into 24-well Primaria plates (Corning, Durham, NC, USA) two days before inoculation.…”

Pathology of African Swine Fever in Reproductive Organs of Mature Breeding Boars

“…The initial objective of this study was to assess the detectability of ASFV infections in male breeding animals, especially in the early phase of the disease, and to provide baseline data on the transmissibility via artificial insemination. Samples from this recently published study [ 9 ] were archived to allow for more detailed analyses into the pathology and pathogenesis in male animals.…”

“…Of note, very recently, Friedrichs et al [ 9 ] demonstrated that the efficient transmission of ASFV is possible via the introduction of semen from infected breeding boars to sows by artificial insemination. The authors collected semen from breeding boars infected with the moderately virulent ASFV strain “Estonia 2014” and inseminated gilts.…”

Innovative Research Offers New Hope for Managing African Swine Fever Better in Resource-Limited Smallholder Farming Settings: A Timely Update

“…It has generally been recommended that artificial insemination would be a better alternative, because there was no scientific evidence that the virus could be effectively transmitted in semen, apart from a personal communication cited in a review that a researcher had successfully infected a sow via semen [ 111 ]. However, a recent study reported successful infection of gilts by insemination of semen from boars infected with the Estonia 2014 ASFV strain, which is considered to be moderately virulent [ 112 ]. There was a high abortion rate in the infected gilts, mostly when they developed a high fever, but replicating ASFV was detected in tissues of foetuses [ 112 ].…”

“…However, a recent study reported successful infection of gilts by insemination of semen from boars infected with the Estonia 2014 ASFV strain, which is considered to be moderately virulent [ 112 ]. There was a high abortion rate in the infected gilts, mostly when they developed a high fever, but replicating ASFV was detected in tissues of foetuses [ 112 ]. Transmission via semen from infected boar studs was considered to be a risk for commercial farms, but in practical terms, more evidence would be needed to determine the risk in the smallholder pig sector, where it is not widely used.…”