Survival of the Faucet Snail after Chemical Disinfection, pH extremes, and Heated Water Bath Treatments

—The faucet snail Bithynia tentaculata, a nonindigenous aquatic snail from Eurasia, was introduced into Lake Michigan in 1871 and has spread to the mid-Atlantic states, the Great Lakes region, Montana, and most recently, the Mississippi River. The faucet snail serves as intermediate host for several trematodes that have caused large-scale mortality among water birds, primarily in the Great Lakes region and Montana. It is important to limit the spread of the faucet snail; small fisheries equipment can serve as a method of snail distribution. Treatments with chemical disinfection, pH extremes, and heated water baths were tested to determine their effectiveness as a disinfectant for small fisheries equipment. Two treatments eliminated all test snails: (1) a 24-h exposure to Hydrothol 191 at a concentration of at least 20 mg/L and (2) a treatment with 508C heated water for 1 min or longer. Faucet snails were highly resistant to ethanol, NaCl, formalin, Lysol, potassium permanganate, copper sulfate, Baquacil, Virkon, household bleach, and pH extremes (as low as 1 and as high as 13). The faucet snail Bithynia tentaculata (Gastropoda: Prosobranchia), also called the common bithynia or mud bithynia, is a nonindigenous aquatic snail that was introduced into the USA in 1871 (Mills et al. 1993). The faucet snail is found throughout the mid-Atlantic region; in Lakes Erie, Ontario, and Champlain; across New York; in the Potomac River, Virginia; in Chesapeake Bay, Maryland (Ruiz et al. 2000); and in Montana (R.A.C., personal observation). Within the last 10 years, it has been introduced into Lake Onalaska in the Mississippi River system (Sauer et al. 2007). The faucet snail carries larvae of the pathogenic trematodes Cyathocotyle bushiensis (Cyathocotylidae), Sphaeridiotrema globulus (Psilostomidae), and Leyogonimus polyoon (Lecithodendriidae) that mature in the gastrointestinal tracts of water birds. The major bird species affected in die offs along the Mississippi and Wolf rivers (northwestern Wisconsin) are the lesser scaup Aythya affinis and American coot Fulica americana (Cole 2001; Sauer et al. 2007). The estimated number of birds killed by these parasites between spring 2002 and spring 2007 along the Mississippi River is between 32,000 and 40,000 (U.S. Fish and Wildlife Service [USFWS], unpublished data). The faucet snail has a calcareous plate (operculum) borne on the dorsal posterior foot, which closes the aperture when the snail withdraws into the shell (Burch 1982). This operculum helps to seal off the mantel from offending chemicals and renders the faucet snail less susceptible to desiccation. Faucet snails have been recorded to withstand desiccation for over 8 d in dry containers and a temperature of 218C (R.A.C., unpublished data). Faucet snails could incidentally become entrapped and survive on the dry surfaces of small fisheries equipment (e.g., dip nets, boots, or small seines) for a period of several hours to several days. This concern is well founded, because a similar species of nonindigenous operculated snail (red-rim melania Melanoides tuberculatus) has been spread by nets and other small fisheries equipment (Mitchell et al. 2007). Unless it is effectively disinfected (every faucet snail killed), the equipment might serve as a source for expansion of the faucet snail’s range. This study evaluates potential methods for disinfecting small fisheries equipment by chemical disinfection, pH extremes, and heated water bath treatments.