Caseous lymphadenitis (CL) or pseudotuberculosis is a pyogenic disease, caused by Corynebacterium pseudotuberculosis, affecting mainly small ruminants, although it has also been described in deer, cows, horses, pigs, and humans. Despite its worldwide distribution and its economic impact on sheep and goat production, its real prevalence and distribution are underestimated in countries where CL it is not considered a notifiable disease. The present work is the first seroprevalence study in CL carried out in Alto Alentejo, the main livestock region of Portugal, with the aim of (1) assessing the validity and usefulness of various serological and molecular diagnostic techniques, (2) conducting a cross-sectional survey of the seroprevalence of C. pseudotuberculosis in small ruminants, (3) conducting a preliminary study of the risk factors associated with seropositivity and (4) describing the clinical cases found. To meet this aim, serum samples were taken from 756 animals in 82 farms, as well as abscess and pus samples from 58 animals with skin and visceral pyogranulomatous lesions. Prior to the study and to improve the sensitivity of multiplex PCR for the identification of C. pseudotuberculosis from purulent samples, the validity of this test was determined after including a dilution (1:10) of the DNA samples. The results obtained showed no improvement in their diagnostic validity, so we consider that the dilution should only be applied in highly purulent lesions that are negative to the classical protocol. The comparison of the direct ELISA test (ELITEST CLA # CK105A®) with the multiplex PCR (reference test) showed a diagnostic sensitivity and specificity of 100% and 76.1%, respectively, with a Probability Ratio of 4.78 for positive results and greater than 100 for negative ones. On this basis, the ELISA would offer 100% certainty in discarding CL, regardless of the pretest probability, but the credibility of positive results would only be ≥ 80% when the real prevalence in the group was ≥ 46%. The epidemiological study of C. pseudotuberculosis infection reflected a seroprevalence at the farm level (dispersion) of 75.4% (95% CI [66.4% -84.5%]), with 16.7% of affected small ruminants (95% CI [14.1% -19.4%]), finding significantly greater susceptibility in the caprine species (PR 4.0 95% CI [3.31-4.84]), in dairy animals (PR 2.91 95% CI [2.49 -3.42]) and in those raised in a non-extensive production regime (PR 4.19 95% CI [3.67- 4.79]) and / or in medium and large farms. Finally, the pathological study confirmed the importance of the visceral form of the disease, especially in sheep species. The results found in this thesis confirm an actual problem and point out the importance of CL in small ruminants in Portugal, as also the usefulness of the direct ELISA technique in the detection of subclinical cases and as a screening test in disease control programs.

La Tesis presentada por la doctoranda Dña. Lina Luis Costa Salgueiro, titulada en Medicina Veterinaria por la Facultad de Medicina Veterinaria de la Universidad de Lisboa (Portugal), se ha realizado dentro de la línea de investigación "Diagnóstico y control de enfermedades" del departamento de Sanidad Animal. Este trabajo de tesis doctoral es el primer estudio de seroprevalencia de Linfadenitis Caseosa (LC) realizado en la principal región ganadera de Portugal en el cual se planteó una validación de una prueba ELISA comercial para la detección de animales portadores asintomáticos, a fin de aplicarla al estudio epidemiológico de la LC en la región del Alto Alentejo (Portugal) y, a largo plazo, en los programas nacionales de control y erradicación de la enfermedad. El proyecto de investigación planteado supuso la toma de muestras y colección de información para el estudio epidemiológico en explotaciones de pequeños rumiantes portuguesas y un matadero regional, bien como el aprendizaje y realización de técnicas de diagnóstico molecular y serológico con trabajo de laboratorio intenso. Los resultados obtenidos, de notable calidad científica e importancia epidemiológica, han sido aceptados para su divulgación en congresos de ámbito internacional (World Buiatrics Congress - Madrid), y publicados en la revista científica Veterinary Medicine and Science, indexada en Journal of Citation Reports (JCR) dentro del tercero cuartil. Asimismo, otro de los artículos derivados de la tesis se encuentra publicado en la revista Journal of Veterinary Science & Animal Husbandry (Revista referenciada en el NCBI DBs). Los resultados hallados confirman la importancia sanitaria de la Linfadenitis caseosa en los pequeños rumiantes en Portugal, así como la utilidad de la técnica ELISA en la detección de casos subclínicos y como prueba de cribado en programas de lucha

{"references": ["Costa, Lina (2021). Epidemiological study on Caseous Lymphadenitis in small ruminants in the Alto Alentejo region (Portugal) and evaluation of molecular and serological techniques in the diagnosis of the disease. Tesis Doctorales UCO.http://hdl.handle.net/10396/21531."]}