Impact of farm management on expression of early mortality syndrome/acute hepatopancreatic necrosis disease (EMS/AHPND) on penaeid shrimp farms in Thailand.

Asian shrimp farming industry has experienced massive production losses due to a disease caused by toxins of Vibrio bacteria, known as early mortality syndrome/acute hepatopancreatic necrosis disease (EMS/AHPND) for the last 5 years. The disease can cause up to 100% cumulative pond mortality within a week. The objective of this study was to identify factors associated with AHPND occurrence on shrimp farms. A case-control study was carried out on shrimp farms in four provinces of Thailand. Factors related to farm characteristics, farm management, pond and water preparation, feed management, post-larvae (PL) shrimp and stock management were evaluated. Multivariable logistic regression analysis identified factors affecting AHPND occurrence at the pond level. Chlorine treatment, reservoir availability, use of predator fish in the water preparation, culture of multiple shrimp species in one farm and increased PL stocking density contributed to an increased risk of AHPND infection, while delayed first day of feeding, polyculture and water ageing were likely to promote outbreak protection. Additionally, the source of PL was found to be associated with AHPND occurrence in shrimp ponds, which requires further study at the hatchery level. Identification of these factors will facilitate the development of effective control strategies for AHPND on shrimp farms.

Estimation of the repeatability and reproducibility of three diagnostic tests for infectious salmon anaemia virus.

Reverse transcriptase polymerase chain reaction (RT-PCR), virus isolation (VI) and indirect fluorescent antibody tests (IFAT) are three assays currently used by the salmon industry to identify fish infected with infectious salmon anaemia virus (ISAV). However, no data are available on the repeatability (within-laboratory consistency) and reproducibility (between-laboratory consistency) of these assays and very limited information is available on the effect of freezing samples on test results. In order to evaluate these assays, five laboratories participated in a blinded study of 400 kidney samples representing four populations of farmed Atlantic salmon with different prevalence of ISAV. Each laboratory used its own testing protocols. Repeatability and reproducibility were evaluated using kappa as the measure of agreement. The effect of freezing was evaluated using the McNemar test. Freezing did not affect VI but improved the sensitivity of RT-PCR. The repeatability and reproducibility of VI was almost perfect. There was a substantial difference in repeatability of RT-PCR among the three laboratories with kappa ranging from 0.5 to 0.96. The repeatability for RT-PCR was generally low. The repeatability of IFAT was moderate when the results were analysed using 1+ and above as a positive result. The results of the study show the need to standardize the protocol and interpretation of RT-PCR.

Estimation of specificity and sensitivity of three diagnostic tests for infectious salmon anaemia virus in the absence of a gold standard.

Reverse transcriptase-polymerase chain reaction (RT-PCR), virus isolation (VI) and indirect fluorescent antibody test (IFAT) are three tests currently used by the salmon industry to identify fish infected with the infectious salmon anaemia virus (ISAV). However, very limited information is available on the sensitivity and specificity of these methods. In order to evaluate these tests in fish representing a range of farmed Atlantic salmon populations, five laboratories participated in a blind study of 400 kidney samples from four groups of fish with different prevalences of ISAV. Each laboratory used its own testing protocols. Estimates of the specificity of each test were determined directly from a population assumed to be free of infection. Indirect estimates of the sensitivity and specificity of each test were obtained using maximum likelihood estimation of a latent class model (i.e. no gold standard test result available). There was a substantial difference in sensitivity and specificity of RT-PCR among the three laboratories using this test. If only the best results for the RT-PCR tests are taken into account, the maximum likelihood estimates obtained from this study suggest RT-PCR and VI are of similar high sensitivity (range 92-100%), IFAT is the least sensitive method (range 65-76%) while the three tests have similar high specificities (range 96-100%). The results of the study suggest: (1) RT-PCR tests should be standardized before they are used as a diagnostic test for prevention and control of ISAV, (2) the sensitivity of VI was higher than expected and (3) IFAT has a low sensitivity but might be a good screening test because of its low cost.

Pericardial drainage: subxiphoid vs. transthoracic approach.

The optimal management of effusive pericardial disease remains controversial. Subxiphoid drainage has been criticized for a high recurrence rate while transthoracic procedures (window or pericardiectomy) are more invasive operations with greater potential for morbidity. We compared subxiphoid (SX group) and transthoracic (TT group) drainage in 131 patients (age range from 1 month to 81 years) treated from 1979 to the present. The etiology of effusion included cancer (38), uremia (24), infection (27), radiation (9), and other (33) causes. The two groups had similar age and sex distribution, etiology, and fluid volume. There was no difference in the operative mortality between the two groups (SX 15%, TT 13%, p = NS). Patients undergoing thoracotomy for treatment of effusive pericardial disease had a higher incidence of respiratory complications as defined by the presence of pneumonia, pleural effusion, prolonged ventilation, and need for reintubation (SX 11%, TT 35%, p less than 0.005). This may account, in part, for the longer mean hospital stay in transthoracic group (14.4 vs. 11.4 days). Nine patients were lost to follow-up after hospital discharge. The remaining 104 hospital survivors were followed for between 1 month and 11 years (mean 34 months, cumulative of 297 patient years). Three patients in each group experienced fluid recurrence and all but one were successfully treated by needle aspiration or percutaneous catheter placement. Following discharge, no patient required reoperation for effusive or constrictive pericardial disease or died from tamponade. There were no significant differences in 5-year actuarial survival (SX 54%, TT 49%) or actuarial freedom from recurrence (SX 89%, TT 93%).(ABSTRACT TRUNCATED AT 250 WORDS)