Resumen de Pathophysiology of sarcoptic mange in iberian ibex
Sarcoptic mange is a parasitic skin disease caused by the burrowing mite Sarcoptes scabiei. It affects mammals worldwide, including humans. Sarcoptic mange in wildlife is considered an emerging disease, and can cause severe population declines. Iberian ibex (Capra pyrenaica) is a medium-sized mountain ungulate endemic to the Iberian Peninsula. Since the end of the ‘80s, the Iberian Ibex populations of southern and eastern Spain have been affected by mange, suffering variables mortalities reported to reach up to 90%. Most of the studies on sarcoptic mange in Iberian ibex have focused on the epidemiology and the population consequences of the diseases, thus existing a lack of knowledge about the pathophysiology and pathogenesis of this disease in this species.
The two first studies of this thesis analysed the acute phase proteins (APPs) (Study I) and validated a test for the detection of immunoglobulins G (IgG) against S. scabiei (Study II) in free-ranging Iberian ibexes, both healthy and affected by sarcoptic mange. In the Study I, an increase of serum amyloid A (SAA) and in lower magnitude of alpha-1 acid glycoprotein (AGP) concentrations was observed, in correlation with the extent of the skin lesions caused by sarcoptic mange. Conversely, haptoglobin (Hp) concentration was not different between the healthy and infested ibexes. Since there is not an effective laboratory diagnostic method, in the Study II three enzyme-linked immunosorbent assays (ELISAs) were evaluated for IgG detection against S. scabiei in Iberian ibex, and one of the three showed high specificity and sensitivity by using the avidin-biotin system, which allowed it to be validated.
The Studies III and IV were carried out on Iberian ibexes with different alleles of the DRB1 gen of the major histocompatibility complex (MHC) class II, experimentally infested with S. scabiei. Although all the infested ibexes developed lesions compatible with sarcoptic mange, the clinical evolution varied from extensive lesions affecting most of the body surface to mild lesions and clinical recovering of the disease (Study III). However, such clinical differences seemed unrelated to MHC differences. The severely affected ibexes showed anaemia, possibly related to the inflammation caused by the mite, as well as neutrophilia and lymphopenia, probably due to secondary infections favoured by sarcoptic mange. Immunoglobulin G concentration also increased in agreement with the severity of the lesions. Finally, the Study IV addressed the genomic response of Iberian ibexes to the experimental infestation with S. scabiei. The severely affected Iberian ibexes showed an increase in the gene expression of pathways related to immunity and inflammation, agreeing with the exacerbated and non-effective generalized immune response induced by the mite and the response to secondary infections. Moreover, the Iberian ibexes that recovered showed an increase in the local skin expression of genes related with antigen presentation and T-lymphocytes activation.
To summarize, sarcoptic mange induces both systemic and local changes in the Iberian Ibex, causing an increase in APP and antibodies, as well as haematological and local and systemic gene expression disorders. Although the causes of the differences found in the clinical evolution have not been completely elucidated, local skin cellular immunity may be key in controlling the infestation. Immunoglobulin G detection by ELISA can be a useful and effective diagnostic tool for sarcoptic mange in Iberian Ibex, while APP are a prognostic indicator.
