The farm hygiene status of a pig farm influences how the animals respond to an infection with the African Swine Fever virus. This has been shown in a study by the Swiss Institute of Virology and Immunology in collaboration with the University of Bern. They have published about this research in the scientific journal PLOS Pathogens.
Field viruses and laboratory-attenuated strains of African swine fever cause highly variable clinical disease symptoms and differ in their survival rate. The mechanisms behind this are unclear. The researchers hypothesized that the immunological and hygienic status in which pigs are kept is a determinant of the disease course of African swine fever.
The scientists compared the pre-immune profile and response to African swine fever virus infection in specific pathogen-free (SPF) pigs and animals from a standard pig farm. At baseline, SPF pigs had lower white blood cell counts and a lower basal inflammatory and antiviral transcriptomic profile compared to the other pigs. This difference could be linked to differences in the composition of the gut microbiome.
After artificial infection with a highly virulent strain of African swine fever, severe clinical signs, viraemia and pro-inflammatory cytokines appeared in SPF pigs earlier, indicating a reduced ability to control early virus replication. In contrast, during infection with an attenuated field isolate, SPF pigs showed milder and shorter clinical illness with full recovery, while farm pigs showed severe long-term illness with 50% mortality.
The farm pigs produced more inflammatory cytokines, while SPF pigs produced more anti-inflammatory IL-1ra early after infection. In these animals a stronger increase in leukocytes was found in the recovery phase. The scientists conclude that hygiene-dependent innate immune status influences immune responses in African swine fever infections. Such effects should be considered when developing live vaccines against African swine fever.
Meer informatie is te vinden in de publicatie ‘The baseline immunological and hygienic status of pigs impact disease severity of African swine fever’ in PLOS Pathogens.
bron: PLOS Pathogens, 25/08/2022
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