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Abstract
Simple SummaryAluminum-hydroxide is an effective vaccine adjuvant used in most commercial sheep vaccines. It facilitates the establishment of a robust immune response against the vaccine antigen. During the first decade of the 21st century, repetitive injections with vaccines containing aluminum-based adjuvants were proposed to be linked to a progressive wasting syndrome in sheep. The aim of this work was to analyze several clinicopathological parameters, including growth performance, clinical data, and histopathological observations in lambs intensively injected with aluminum-containing vaccines, aluminum-hydroxide only, or a saline solution as control. Although aluminum-hydroxide was linked to chronic inflammatory reactions at the injection site and the development of behavioral changes in sheep, the results presented here indicate that injected aluminum-hydroxide, either alone or in combination with vaccine antigens, is not enough to induce relevant changes in the parameters studied. Other factors such as sex, breed, age, production system, diet or climate conditions could play a role in the development of the previously described wasting syndrome.Aluminum (Al) hydroxide is an effective adjuvant used in sheep vaccines. However, Al-adjuvants have been implicated as potential contributors to a severe wasting syndrome in sheep—the so-called ovine autoimmune-inflammatory syndrome induced by adjuvants (ASIA syndrome). This work aimed to characterize the effects of the repetitive injection of Al-hydroxide containing products in lambs. Four flocks (Flocks 1–4; n = 21 each) kept under different conditions were studied. Three groups of seven lambs (Vaccine, Adjuvant-only, and Control) were established in each flock. Mild differences in average daily gain and fattening index were observed, indicating a reduced growth performance in Vaccine groups, likely related to short-term episodes of pyrexia and decreased daily intake. Clinical and hematological parameters remained within normal limits. Histology showed no significant differences between groups, although there was a tendency to present a higher frequency of hyperchromatic, shrunken neurons in the lumbar spinal cord in the Adjuvant-only group. Although Al-hydroxide was linked to granulomas at the injection site and behavioral changes in sheep, the results of the present experimental work indicate that injected Al-hydroxide is not enough to fully reproduce the wasting presentation of the ASIA syndrome. Other factors such as sex, breed, age, production system, diet or climate conditions could play a role.
Highlights
Vaccines are indispensable tools in animal production to control diseases and increase production rates [1]
This data distribution was observed for the average daily gain (ADG) values of all flocks, Flock 2 was the only one where these was observed for the ADG values of all flocks, Flock 2 was the only one where of 18 these differences were statistically significant (p = 0.045)
The has been observed that booster vaccinations against respiratory pathogens in fattening lambs included in this work likely suffered repetitive episodes of hyperthermia and delambs can cause moderate growth retardation, with animals reaching their optimal sacrifice creased daily intake, which could have affected ADG and absolute weight at the end of weight 5 days later than control animals (JM Gonzalez, personal communication)
Summary
Vaccines are indispensable tools in animal production to control diseases and increase production rates [1]. A recent example was the compulsory vaccination campaign against bluetongue virus that took place in most European countries during the first decade of the 21st century [4,5]. This immunization campaign effectively controlled virus circulation and stopped disease progression. The repetitive vaccination caused diverse side effects of variable intensity that affected productive parameters and animal health in several countries [6,7,8,9,10]
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