Comparison of Antemortem and Environmental Samples for Zebrafish Health Monitoring and Quarantine.

Molecular diagnostic assays offer both exquisite sensitivity and the ability to test a wide variety of sample types. Varioustypes of environmental sample, such as detritus and concentrated water, might provide a useful adjunct to sentinels in routinezebrafish health monitoring. Similarly, antemortem sampling would be advantageous for expediting zebrafish quarantine,without euthanasia of valuable fish. We evaluated the detection of Mycobacterium chelonae, M. fortuitum, M. peregrinum,Pseudocapillaria tomentosa, and Pseudoloma neurophilia in zebrafish, detritus, pooled feces, and filter membranes after filtration of 1000-, 500-, and 150-mL water samples by real-time PCR analysis. Sensitivity varied according to sample type andpathogen, and environmental sampling was significantly more sensitive than zebrafish sampling for detecting Mycobacteriumspp. but not for Pseudocapillaria neurophilia or Pseudoloma tomentosa. The results of these experiments provide strong evidence of the utility of multiple sample types for detecting pathogens according to each pathogen's life cycle and ecologicalniche within zebrafish systems. In a separate experiment, zebrafish subclinically infected with M. chelonae, M. marinum,Pleistophora hyphessobryconis, Pseudocapillaria tomentosa, or Pseudoloma neurophilia were pair-spawned and individuallytested with subsets of embryos from each clutch that received no rinse, a fluidizing rinse, or were surface-disinfected withsodium hypochlorite. Frequently, one or both parents were subclinically infected with pathogen(s) that were not detected inany embryo subset. Therefore, negative results from embryo samples may not reflect the health status of the parent zebrafish.