Field Equipment: Cleaning & Disinfection
Volume 2, Issue 3
Updated November 2002
By G. Russell Danner MS, DVM
It is becoming increasingly evident from epidemiological data on fish pathogens like Myxobolus cerebralis, and Infectious Salmon Anemia virus, that human activities can transport fish pathogens amongst different waters. The introduction of novel fish pathogens on naive fish populations, like M. cerebralis upon Oncorhynchus nerka can have devastating effects. Whirling Disease has decimated the rainbow trout fishery in several western states. Additionally, human activities are largely responsible for the inadvertent spread of harmful nonindigenous species such as: zebra mussel (Dreissena polymorpha Pallas), ruffe (Gymnocephalus cernuus), and Eurasian watermilfoil (Myriophyllum spicatum).
It would be ideal if a single compound would destroy all fish pathogens and nonindigenous species, while causing no harm to treasured native species and the environment. However, there is no such compound. It is up to the applicant to decide what is the pathogen of most concern, and how it is to be reduced or eliminated. It is not necessary to kill pathogens or exotic organisms merely remove them from the person, or equipment being moved from location to location.
Biosecurity via Daily Planning: Organizing your field schedule to travel from pristine “Class A” waters early in the day and to other more contaminated “Class C” waters later in the day. This precautionary procedure helps reduce transport of undesirable organisms to the most pristine waters. Clean equipment at the end of the day, so that it is clean and ready for service the next morning.
"Or if a person touches anything ceremonially unclean-whether the carcasses of unclean wild animals or of unclean livestock or of unclean creatures that move along the ground-even though he is unaware of it, he has become unclean and is guilty." Lev. 5:2
Cleaning Equipment: It is not always be necessary to destroy organisms that you do not want to transport to new locations. Rinsing equipment: boats, boots, nets, tires of accumulations of mud, weeds, slime and other aquatic organisms is a simple method of decreasing the opportunities for pathogens and nuisance organisms to be spread between locations. Rinsing with clean water simply removes the organisms from your equipment; leaving them at their original site. Mild detergents can also be used to remove dirt and organisms from equipment.
"The solution to pollution is dilution." Unknown.
Disinfection: Several factors should be included in an evaluation of disinfectants. A prerequisite for a disinfectant is its effectiveness against the expected spectrum of pathogens. A general guideline for effective killing of pathogens by a disinfectant is a 5-log killing of bacteria and a 4-log killing of viruses. In addition to the activity of the disinfectant, its compatibility with devices should be reviewed in detail; this should include a review of data on devices that have been immersed for longer than recommended times. Instruments can be forgotten after immersion and this mistake should not necessarily result in irreparable damage to the device. Other issues are toxicity, odor, compatibility with other compounds, and residual activity. No single disinfectant destroys all pathogens. It is up to the applicant to decide what is the pathogen of most concern, and how it is to be reduced or eliminated.
Effective Disinfectant Solutions:
A 1:100 dilution of household bleach provides an effective disinfectant for most bacteria and viruses and many other micro-organisms. Items should be allowed to have a minimum contact time of 10 minutes.
A 1% active iodine solution provides an effective antimicrobial disinfectant. Iodophors are relatively free of toxic effects, do not cause irritability, and do not corrode metal surfaces.