Oral supplementation with postbiotics modulates the immune response produced by myxomatosis vaccination in wild rabbits.

Rabbits (Oryctolagus cuniculus) are vitally important species in the Iberian Peninsula ecosystem. However, since 1950, there has been a significant population decline, with major repercussions. This situation is mainly due to the presence of infectious diseases, such as myxomatosis, which is expanding and is characterized by severe and fatal clinical manifestations. Current control measures, mainly those based on vaccinations, are ineffective. Therefore, new strategies need to be developed and implemented. This study aimed to evaluate whether supplementation with postbiotic products modulates the immune response in wild rabbits vaccinated against myxomatosis. For this purpose, two groups of rabbits were established: a control group fed with standard feed ad libitum from weaning (28 days) until two months of age, and a treated group, which was fed under the same conditions but supplemented with postbiotics (3 kg/Tm). All the studied rabbits were vaccinated against this disease during weaning. In addition, a blood samples were obtained from all animals immediately before vaccination and 30 days later, which allowed us to evaluate the level of antibodies against myxomatosis virus (ELISA detection) and the relative expression of gene encoding to cytokines related to the immune response (IL6, TNFα and IFNγ), at both times of the experience. Weight and length measurements were also taken at both times to calculate body index and mean daily gain (MDG). No statistically significant differences in growth parameters were observed. There were also no differences in the serological response among groups. However, a relative underexpression of gene codifying to TNFα (p-value = 0.03683) and a higher expression on IFNγ (p-value = 0.045) were observed in the treated group. This modulation in cytokines could lead to less severe lesions in wild rabbit naturally infected with myxomatosis virus.

Study of pyrethroid resistance mutations in populations of Varroa destructor across Spain.

The Varroa destructor mite is a serious worldwide pest of honeybees that is usually controlled with pyrethroid-based acaricides. However, the intensive use of these substances over the past decades has led to the development of resistance in these mites. Here, Varroa samples collected between 2006 and 2021 from apiaries across Spain were studied to evaluate the presence of mutations producing pyrethroid resistance, particularly those in the gene encoding the voltage-gated sodium channel (VGSC). Genotyping of the IIS4-IIS5 region of this gene detected the L925V (Leucine 'CTG' to valine 'GTG') mutation at position 925 and confirmed the presence of the M918L (Methionine 'ATG' to Leucine 'TTG') mutation at position 918 in these Spanish Varroa mites. Interestingly, the M918L mutation was always found in combination with L925V, both of which were always homozygous. Over and above the high frequency of pyrethroid-resistant mutations in Spanish Varroa populations, this apparently recent association of the M918L and L925V point mutations is a combination that appears to trigger greater resistance than that produced by L925V alone.