ZIRC Fish Health Program
The Zebrafish International Resource Center is committed to maintaining and providing healthy stocks of zebrafish. Our Fish Health Program is designed to prevent the entry of infectious agents, monitor fish health, minimize any potential for disease transmission within the facility, and prevent accidental distribution of pathogens to other facilities.
Animal Health Report
This report summarizes diagnostic testing performed on sentinel fish from the ZIRC aquaculture facility. The facility has recirculating water systems with particle bead filters, large biological sand filters, and UV sterilization. There are sentinel fish in two locations on each water system. The pre-filtration sentinel fish receive water that is returning from the main fish room to the pre-filtration water sump. There are also sentinel control tanks that receive water that has passed through filtration and UV (post-filtration). Prior to stocking the sentinel tanks, fish from the source tank are screened for microsporidia infection by PCR. For each sampling period, the pre- and post-filtration sentinel tanks are stocked with three to four month old fish from the same breeding event. Histopathology is performed on whole fish. Results are reported as the number of positive results. Sentinel results are representative of fish raised in the ZIRC main fish facility. The majority of embryos generated from frozen sperm and shipped directly to customers are one generation removed from the submitting facility of origin and neither the embryos nor parental stocks have been on the ZIRC water system. Please contact Dr. Katy Murray with questions regarding this report or any other animal healthy related issues.
|Location of Sentinel Fish Relative to Filtration||Pre-||Post-||Pre-||Post-||Pre-||Post-||Pre-||Post-||Pre-||Post-||Pre-||Post-||Pre-||Post-||Pre-||Post-|
|Time in Sentinel Tank (Months)||3||3||6||6||3||3||6||6||3||3||6||6||3||3||6||6|
|GROSS PATHOLOGY (N = Normal)||N||N||N||N||N||N||N||N||N||N||N||N||N||N||N||N|
|Encysted metacercariae (digenetic trematodes)des)||0||0||0||0||0||0||0||0||0||0||0||0||0||0||0||0|
|Myxidium sp./Zschokkella sp. (Myxozoa)||0||0||0||0||0||0||0||0||0||0||0||0||0||0||0||0|
|Pseudoloma neurophilia (Microsporidia)||0||0||0||0||0||0||0||0||0||0||0||0||0||0||0||0|
A single species of Mycobacterium, M. chelonae, has been identified from zebrafish and biofilms sampled from the ZIRC aquaculture facility. As with most bacterial pathogens of fish, mycobacterial infections in zebrafish are most often opportunistic in nature. Mycobacteria are nonmotile, weakly staining Gram-positive, pleomorphic bacterial rods that stain acid-fast. Many species of atypical (non-tuberculosis) Mycobacterium are found ubiquitously in the environment in soil, water, and biofilms
ZIRC Quarantine Recommendations
Bringing new fish or embryos into a facility can also bring in new pathogens. The use of strict quarantine practices (i.e., introducing only surface sanitized embryos) can eliminate a large number of potential pathogens from entering a facility and is strongly recommended for all laboratory zebrafish colonies regardless of the source. When adult fish are acquired, they should be held in quarantine until they can successfully breed and all embryos introduced into the main facility or system should be bleached. The ideal quarantine area is a room on a flow-through water system that is both spatially and procedurally separated from the main fish facility. Small facilities often utilize individual aquaria or small recirculating systems in a designated quarantine area. Fish should be observed and acclimated in quarantine for a minimum of two weeks before breeding. If fish show clinical disease within this period, they should be treated or euthanized, depending on the value of the particular fish. Quarantined fish are bred, and only bleached embryos leave the quarantine area. Once the line has been established in the main facility, the fish in quarantine are culled. Fish should be disposed of in a manner that will not contaminate the main facility.
Embryos received from other facilities within 36 hours post-fertilization can often be bleached upon arrival and introduced immediately into the facility, thus avoiding quarantine. If the embryos are too old to be bleached (embryos with a compromised chorion or already hatched) when they arrive, they should be reared and bred in quarantine similar to adult fish.
A procedure for bleaching embryos can be found in The Zebrafish Book (Westerfield, 2000), which is available on-line through ZFIN, and is distributed in print by ZIRC. The specific ZIRC bleaching procedure is also outlined in the protocols link from the ZIRC homepage. Organisms can be protected from bleach exposure when sequestered within detritus or nonviable embryos. Embryos should therefore be cleaned of all debris, fecal material, and unfertilized or dead eggs before the bleaching procedure.
The "sanitized egg only" type of quarantine is the preferred and recommended procedure. Other approaches allow greater possibility of pathogen introduction and spread. However, sanitized egg approach requires the ability to raise larval fish and is a limitation for some facilities. In these cases, it is recommended that new arrivals be quarantined for observation for a minimum of three to four weeks before being introduced into the main system. A sample of fish can be sacrificed for diagnostic workup along with any fish showing signs of disease. Treatment of the entire group can then be instituted based on the diagnostic evaluation.