Borriello, Giuliano (2020) Ultrasound liver monitoring as precision farming technique for the assessment of cystic echinococcosis in sheep. [Tesi di dottorato]

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Abstract

Echinococcus granulosus (E. granulosus) is a cestode causing cystic echinococcosis (CE) in intermediate hosts (human and livestock) and dwelling in the small intestines of the definitive hosts (canids) in its adult form. CE is a widespread zoonotic parasitic disease having a negative effect on human-animal health and livestock production. Early in vivo diagnosis, control and prevention of the infection of E.granulosus in sheep are crucial steps to reduce its diffusion. Currently, liver ultrasonography is one of the most reliable diagnostic techniques for CE assessment in the intermediate hosts. So, the aims of the present thesis were: (i) to evaluate the sensibility and specificity of a new fast ultrasonographic method in different sheep’s breeds; (ii) to compare the latter with the protocol developed on the Italian Sarda sheep, based on a single hypochondrial acoustic window (HYP), as well as (iii) to try to define a new and fast-focused technique for CE detection under field conditions. One-hundred-seventy-two (172) female sheep of different breeds were submitted to a complete liver ultrasound examination (cUS) starting from the right hypochondrium to the 5th intercostal space (IS). The evaluated scan area was divided in: Zone 1 (Z1, from the right hypochondrium to the 11th IS), Zone 2 (Z2, from the 10th IS to the 8th IS and Zone 3 (Z3, from the 7th IS to 5th IS). Moreover, also the HYP technique was employed. Each zone (ZONAL scan) was analysed individually along with the contiguous ones (HYP+ Z1; Z1+Z2, Z2+Z3). During each scanning, the hydatid lesions detected were localized in the corresponding zones. After the clinical procedures, the animals were slaughtered and necropsy’s results were recorded (gold standard). All US techniques were compared using sensitivity and specificity as well as the number and percentage of positive zone detected. Because of the non-homogenous weight distribution, the sample population was later divided into Group 1 (G1, weight ≤ 50 kg: 22/172 - 13%), Group 2 (G2, 51≤ weight ≤ 75: 69/172 – 40%), Group 3 (G3, weight ≥76: 81/172 – 47%). cUs showed the highest level of sensitivity and specificity, as well as the highest number of positive zones when compared to all the other techniques (p≤0.01). cUS, resulted the best technique also during the comparison by weight distribution; HYP and HYP+Z1 showed performance similar in lighter sheep (Group 1). The current thesis represents the first investigation evaluating the use of the US as a potential fast-focused technique for CE hepatic lesions detection in different breeds of sheep under field conditions. The present investigation confirmed that ultrasonography could be considered a reliable intra-vitam technique for CE assessment. Indeed, scanning the entire organ, from the hypochondrium to the 5th intercostal space is recommended under field conditions to optimize the diagnostic performance. However, the time needed for the exam execution can represent a limit especially for screening in large flocks; further strategies to reduce the time consuming under field condition should be evaluated to improve the widespread of ultrasound use for CE diagnosis in sheep flock.

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