Integrated diagnosis of paratuberculosis (Johne’s disease) in slaughtered goats: Morphological assessment and seroprevalence insights

Abstract

Paratuberculosis (PTB) or Johne´s disease is a chronic emaciating disease endemic in many parts of the world. PTB is caused by Mycobacterium avium subsp. paratuberculosis (MAP) and affects primarily ruminants causing considerable economic losses. Goat farming plays a pivotal role in the global economy and represents a major socioeconomic and cultural pillar in the Canary Islands. The archipelago holds the fourth largest goat population in Spain. In this study, 91 Majorera goats. slaughtered in 2024 in Gran Canaria were examined. The ileocecal valve (ICV) and mesenteric (MS) and ileocecal (IC) lymph nodes were assessed through gross pathology, his- tological grading, Ziehl-Neelsen (ZN) staining, immunohistochemistry (IHC), serology (PARACHEK® 2), and real-time polymerase chain reaction (PCR) targeting IS900. Macroscopic PTB suggestive findings were detected in 30.8% of animals, while 42.9% showed microscopic granulomatous inflammation. Among the samples with lesions, 46.2%, 53.8%, and 54.1% were positive by ZN, IHC, and PCR, respectively, with the highest agreement observed between IHC and PCR demonstrated greater sensitivity, identifying additional cases missed by other techniques. Seroprevalence was 34.5%, with significant age-related differences (p = 0.046). Additionally, the carcass weight of goats with anti-MAP antibodies and/or PTB lesions tended to be lower compared to unaffected animals. However, these differences were not statistically significant, with mean weights in affected animals ranging from 3.9 kg to 10.6 kg lower. These findings highlight the diagnostic complexity of PTB and support the integration of histological, immunological, and molecular methods, recognizing slaughterhouses as valuable tools for further epidemiological surveillance of MAP infections.