ADVANCEMENTS IN DIAGNOSING BESNOITIA BESNOITI IN CATTLE: EVALUATING THE DIAGNOSTIC ACCURACY NASAL AND SCLEROCONJUNCTIVAL SWABS AS NEW DIAGNOSTIC MATRICES

INTRODUCTION: bovine besnoitiosis, caused by the parasite Besnoitia besnoiti, is re-emerging globally, affecting cattle health and causing economic losses (Gentile et al., 2012. vet Parasitol, 184:108- 15). The disease involves acute and chronic phases, with tachyzoites causing clinical symptoms in the former and bradyzoite-containing tissue cysts leading to chronic manifestations. The definitive host remains unidentified, though domestic cats are suspected. Transmission occurs through close contact or via biting flies (Álvarez-García et al., 2013. Trends Parasitol, 29:407-15). Early detection is crucial, with PCR as a reference technique, though invasive skin biopsies are currently used. The aim of our study was to describe the diagnostic accuracy of PCR to identify B. besnoiti in naturally exposed cattle using innovative non-invasive diagnostic matrices as nasal and conjunctival swabs, in comparison to the same PCR protocol applied to skin biopsies and to the histological examination of skin biopsies. MATERIALS AND METHODS: The study involved 57 Limousine cattle from various farms in the Apennines mountains in Italy. Clinical examinations, focusing on mucosae and tegmentum inspection, were conducted. Skin biopsies were obtained from the neck, nasal and scleroconjunctival swabs were sampled. Histopathology was performed on one 8mm biopsy for each animal, while mucosal swabs and one 5mm skin biopsy for each animal underwent DNA extraction and were tested by end-point PCR targeting the ITS gene of B. besnoiti. Diagnostic sensitivity (Se) and specificity (Sp) of histological examination of skin biopsies (HIS-SK), end-point PCR of skin biopsy (PCR-SK), nasal swabs (PCR-NS) and scleroconjunctival swabs (PCR- SC) were assessed using a bayesian Latent Class Model analysis. RESULTS AND CONCLUSIONS: In the selected model, histological examination of skin biopsies (HISSK) exhibited the highest Sp (99.1%), compared to the PCR-SK (71.6%) and PCR-NS-SC (47.6%). Regarding Se, PCR-SK and PCR-NS-SC showed similar results (PCR-SK = 91.0%), compared with 85.0% of PCR-NS-SC, while the Se of HIS-SK resulted lower (33.0%). Overall, the sensitivity of the PCR-NS-SC was adequate to diagnose B. besnoiti, however, it lacked in specificity. Consequently, the PCR-NS-SC could serve as a valuable screening test for detecting bovine besnoitiosis. This new diagnostic approach can be of valuable importance in clinical routine, as the non-invasive matrices used for diagnosis do not require strict containment of the animal, thereby also promoting animal welfare.