Behavioral changes associated with repetitive inoculation of aluminium containing products in sheep

Trabajo presentado en el 9th International Sheep Veterinary Congress, celebrado en Harrowgate (Reino Unido), del 22 al 26 de mayo de 2017

The use of aluminium-containing vaccines has been associated with adverse reactions in sheep. These reactions include, on one hand, acute neurological signs associated with sterile meningoencephalitis that occur few days after a vaccination, and on the other hand, chronic weight lost with neurodegenerative changes that may appear several months after the vaccination. In Spain, these symptoms were widely observed after the bluetongue vaccinations campaigns between 2007 and 2010. All these changes were included as part of the Autoimmune/inflammatory Syndrome induced by Adjuvants (ASIA syndrome).A,B Furthermore, ASIA-affected animals showed an array of behavioural changes as alternant periods of depression and excitement, restlessness, polyphagia and increased aggressiveness, especially noticeable by compulsive wool biting. These symptoms were partially reproduced in a small cohort of animals, but were not fully studied or characterized. The present study aims to reproduce and describe the array of behavioural symptoms following the application of aluminium-containing vaccines and to establish the role of the aluminium used as adjuvant in its development. Three groups (n=7 each) of breed and sex-matched three-month-old lambs were established and maintained in three isolated pens in identical conditions of housing, management and diet along 12 months. Animals followed an inoculation protocol with different substances: Group A received a total of 16 doses of commercial aluminium-adjuvant containing vaccines (following manufacturers’ recommendations); Group B received the same amount of aluminium-adjuvant alone; and Group C received PBS. Cognitive and behavioural studies together with a welfare blood panel were performed twice in two different periods: first in summer (September 2015) and then in winter (February 2016). Cognitive studies included T-maze, open field and novel object tests. Behavioural studies consisted in 12 hours/day recordings during a whole week with assessment of social (aggressions, affiliations, and stereotypes) and individual behaviours. Main differences were observed in the behavioural tests. Vaccinated and adjuvant-inoculated animals showed significantly higher levels of aggressions and stereotypes in both periods of time. Furthermore, both groups showed significantly lower levels of affiliations accompanied by significantly higher values of stress biomarkers in the winter period. These results demonstrated behavioural changes and poor welfare indicators in repetitively vaccinated and adjuvant-inoculated animals. The accumulation of doses along time and, likely, other factors such as cold weather, worsens these indicators. These observations could be the basis to explain the behavioural alterations observed in ASIA-affected animals.

Peer reviewed