Practical scoring system for diagnosis presumptive of acute necrosis of the hepatopancreas (AHPND) in shrimp Penaeus vannamei

The evaluation of clinical signs is a practical tool commonly used to monitor the health status and detect diseases in shrimp farms. The usefulness of a practical scoring system (PSS) for the presumptive detection of AHPND was evaluated. The presence or absence of food in the stomach and intestine and the changes in the external and internal appearance of the hepatopancreas (Hp) were included. Each criterion and the whole of the PSS were contrasted with the histopathological result (gold test) and evaluated the association of each criterion vs the presence of AHPND and the presence of lesions. We present PSS values <= 3 in 77.6% of non-diseased cases, and PSS values >= 4 were present in 87.5% of diseased cases. An association (X-2 = 83.196, df = 8, p = 0.000) was observed between PSS values vs the presence of AHPND and between PSS values >= 5 (X-2 = 93.136, df = 4, p = 0.000) vs the development of AHPND lesions. The receiver operating characteristic (ROC) curve showed that the highest pooled sensitivity and specificity (87.5 and 77.6%, respectively) were observed at cut-off point PSS >= 4, but cut-off point PSS >= 5 showed high utility with a positive likelihood ratio (+ LR = 16) and negative likelihood ratio (- LR = 0.28). The absence of content in the intestine and stomach and a discoloured Hp on external and internal observation are useful clinical signs to recognise 87.5% of organisms with hepatopancreas lesions. PSS is proposed as an in situ detection test in shrimp culture for greater certainty when seeking a confirmatory diagnosis for AHPND.