A recent study conducted in Spain suggested that transfer of fecal organisms from warthogs to domestic hogs can confirm a level of immunity to African Swine Fever (ASF). The study did indicate that the composition of intestinal bacteria can be changed by fecal transfer across species at least over the short term.
In challenge studies, there was evidence of sero-conversion against ASF. The investigators were unable to demonstrate protection against ASF virus since there was no mortality in the challenged negative controls.
Given the pathogenicity of ASF virus effective and durable protection under commercial conditions will best be attained 
using a vaccine. A number of candidates are under development and should be available for extensive clinical trials in 2021.
Zhang, J. et al Fecal Microbiota Transplantation from Warthog to Pig Confirms the Influence of the Gut Microbiota on African Swine Fever Susceptibility. Scientific Reports 10:17605 October 2020