embodiments of the invention provide for combating parasites in aquatic animals , including fish , mollusks , and crustaceans . specifically , propyl propane thiosulfonate ( ptso ) and propyl propane thiosulfinate ( pts ) can be used alone or in combination with each other as an anti - parasitic against a variety of parasites , such as flagellate protozoan , helminths , mollusks , crustaceans , and bloodsuckers , in aquatic animals , such as fish , mollusks , and crustaceans , so that parasites invading fish , mollusk , and crustaceans can both be reduced as well as prevented . in further illustration of the invention , fig1 pictorially shows a process for reducing parasites in aquatic animals . of note , in addition to reducing parasites in aquatic animals , it is contemplated that the invention can also be used to eliminate parasites in aquatic animals . upon the detection of a plurality of parasites on and / or in infected aquatic animals 105 , such as in and / or on fish 805 a , crustaceans 805 b , and mollusks 805 c , propyl propane thiosulfonate ( ptso ) 150 b as well as propyl propane thiosulfinate ( pts ) 150 a can be used alone or in combination with each other 150 to reduce the number of parasites in or / and on the aquatic animals 105 . more specifically , upon the detection of a parasite , pts and / or ptso 150 can be administered 115 to an infected aquatic animal 105 . the administration of pts and / or ptso 150 to an infected aquatic animal 105 can be accomplished via an injection 115 a , a bath treatment 115 b , incorporation with a pharmacological composition and orally administered 115 c , incorporation with a pharmacological composition and injected 115 d , or incorporated with food and then orally administrated 115 e . in this way , after the administration of pts and / or ptso 150 , the parasites in and / or on the infected aquatic animal 105 are reduced ( and / or eliminated ). in yet further illustration of the invention , fig2 a is a flow chart illustrating a process for reducing parasites in aquatic animals . beginning in block 212 , an aquatic animal can be selected . the aquatic animal can be a fish ( a member of a paraphyltic group of organisms that includes gill - bearing aquatic craniate animals ), a crustacean , or a mollusk . the selected aquatic animal can be tested for the presence of parasites whether on and / or in the selected aquatic animal , as shown in block 222 , by any method now known or later developed . of note , testing can also include the visual inspection of the aquatic animal . as illustrated in block 232 , upon the detection of a parasite , such as endoparasites and ectoparasites , including , but not limited to , flagellated protozoan , helminth , nematodes , trematodes , cestodes , bloodsuckers , copepods ( such as sea lice ), crustaceans , and mollusks , a determination as to what to administer to the infected aquatic animal can be made , as indicated in block 242 . specifically , a determination can be made as to whether pts , ptso , or a combination of both should be administered . in addition , as shown in block 252 , an optional determination as whether pts , ptso , or both can be administered in conjunction with a pharmacological composition , such as drugs and other anti - parasitic products , can be made . further , a determination can be made as to how to administer pts , ptso , or both , as shown in block 262 . for instance , administration of pts , ptso , or both can be accomplished via an injection , a bath treatment , or incorporated with food and then orally administrated in the aquatic animal . further , if a pharmacological composition is also selected to be added , then pts , ptso , or both can be incorporated with the pharmacological composition and orally administered or incorporated with the pharmacological composition and injected . in yet further illustration of the invention , fig2 b is a flow chart illustrating a process for preventing parasites in aquatic animals . as illustrated in fig2 b , an aquatic animal can be selected , as shown in block 218 . as before , the aquatic animal can be a fish ( a member of a paraphyltic group of organisms that includes gill - bearing aquatic craniate animals ), a crustacean , or a mollusk . optionally , an aquatic animal can be tested , by any method now known or later developed , including by visual inspection , to determining whether the selected aquatic animal is infected by a parasite ( or multiple , different parasites ), as illustrated in block 228 . regardless of whether it is determined that the selected aquatic animal is infected by parasites , as shown in block 248 , a determination can be made as to what to administer to the selected aquatic animal — pts , ptso , both . in addition , as shown in block 258 , an optional determination as whether pts , ptso , or both can be administered in conjunction with a pharmacological composition , such as drugs and other anti - parasitic products , can be made . also , a determination can be made as to how to administer pts , ptso , or both , as shown in block 268 . for instance , administration of pts , ptso , or both can be accomplished via an injection , a bath treatment , or incorporated with food and then orally administrated to the aquatic animal . even yet further , if a pharmacological composition is also selected to be added , then pts , ptso , or both can be incorporated with the pharmacological composition and orally administered or incorporated with the pharmacological composition and injected . in this way , pts , ptso , or both , can be used in the prevention of parasites in aquatic animals . of note , as indicated herein the use of propyl propane thiosulfonate ( ptso ) as well as propyl propane thiosulfinate ( pts ) can be used alone or in combination with each other . in other words , pts and ptso can be used alone or in combination with each other in any relative percentage ( in any ratio ). in addition , pts and ptso can be used in combination with other anti - parasitic methods and products , including natural products or synthetic drugs , where pts and / or ptso can be in any ratio . the parasites can include endoparasites and ectoparasites , including , but are not limited to , flagellated protozoan , helminth , nematodes , trematodes , cestodes , bloodsuckers , copepods ( such as sea lice ), crustaceans , and mollusks . the aquatic animals being treated by pts and / or ptso can include , but are not limited to , fish ( including fresh water and saline ( marine ) water species ) such as salmon , trout , bass , seabream , fishbase , tilapia , turbot , cod , carp , sturgeon , flatfish , eel , tuna , catfish , coho , lobster , crab , mussel , clam , shrimp and prawn , mullet , shell , and oyster . in which r represents n - propyl group (— ch 2 — ch 2 — ch 3 ), and a is 1 for pts and 2 for ptso . of note , ptso is also known as dipropyl thiosulfonate ( cas number 1113 - 13 - 9 ) and pts is also known as dipropyl thiosulfinate ( cas number 1948 - 52 - 3 ). the concentration of pts used in an embodiment of the invention to reduce a plurality of parasites in and / or on a fish ( and also in crustaceans and mollusks ) can be between one and five thousand parts per million ( 1 - 5000 ppm ). in a different embodiment , the concentration of pts can be between five and one thousand parts per million ( 5 - 1000 ppm ). in yet a different embodiment , the concentration of pts can be between ten and three hundred fifty parts per million ( 10 - 350 ppm ). in yet even a different embodiment , the concentration of pts can be between 10 and four hundred parts per million ( 10 - 400 ppm ). the concentration of ptso used in an embodiment of the invention to reduce a plurality of parasites in fish ( as well as on fish ) can be between one and five thousand parts per million ( 1 - 5000 ppm ). in a different embodiment , the concentration of ptso compound can be between five and one thousand parts per million ( 5 - 1000 ppm ). in yet a different embodiment , the concentration of ptso can be between ten and three hundred fifty parts per million ( 10 - 350 ppm ). in yet even a different embodiment , the concentration of ptso can be between 10 and four hundred parts per million ( 10 - 400 ppm ). in addition , pts and / or ptso can be administered to a healthy aquatic animal or an infected aquatic animal by an immersion treatment , such as a bath . in other words , pts and / or ptso can be used to reduce the number of parasites in and / or on an aquatic animal as well as pts and / or ptso can be used in the prevention of parasites in aquatic animals . in addition , pts and / or ptso can be incorporated into feed ; the feed can then be administered to either a healthy aquatic animal or an infected aquatic animal . to that end , in a different embodiment , pts and / or ptso can be administered orally . for example , pts and / or ptso can be incorporated into a pharmacological composition ( including drugs and other anti - parasitic products ) and then the pharmacological composition can be orally administered to the aquatic animal . in another embodiment , pts and / or ptso can be incorporated into a pharmacological composition ( including drugs and other anti - parasitic products ) and then the pharmacological composition can be injected into the aquatic animal . in addition , pts and / or ptso can be administered to an aquatic animal directly by injection alone ( with just pts , just ptso , or only a mixture of pts and ptso ). in further illustration of the invention , the following examples are presented . of note , as will be understood by one skilled in the art , the invention is not limited to just these examples . the parasiticide efficacy of a mixture of propyl propane thiosulfinate ( pts ) and propyl propane thiosulfonate ( ptso ) was measured in vitro against caligus rogercresseyi . upon receipt in the laboratory , the wild adult females and males were kept in filtered seawater ( 125 μm membranes ) in absolute darkness inside a thermo - regulated chamber at 12 ° c . the egg sacs were removed gently from females using a fine - tipped forceps and placed in separate beakers with 500 ml of filtered seawater in the conditions described above until spawning . the fish were then separated into the different stages : nauplius i , nauplius ii , copepodite and adult for subsequent in vitro susceptibility studies . in order to evaluate effectiveness , several bioassays were performed in triplicate with different concentrations of propyl propane thiosulfinate ( pts ) and propyl propane thiosulfonate ( ptso ) at each stage : nauplio i , nauplio ii , copepodite and adult . in total , 40 caligus were used per test and placed at a rate of 10 individuals per sterile petri plate . a mixture of propyl propane thiosulfinate ( pts ) and propyl propane thiosulfonate ( ptso ) at concentrations of 100 , 200 and 300 ppm was added to each plate over a 30 - minute exposure period . after that , the water was changed and the fish were incubated at 12 ° c . during a 12 - hour photoperiod . a control group was also included . in order to estimate the effective lethal concentration and the survival ratio , observations were registered after treatment using the kaplan - meir function for each of the stages and treatments studied . in this example , a study of oral treatments of ichthyobodosis in rainbow trout with different concentrations of propyl propane thiosulphonate ( ptso ) administered into feed was conducted . rainbow trout oncornynchus mykiss were obtained from a local fish farm and acclimatized for at least 10 days before assay in 1001 tanks with aeration in closed systems of water ( 15 ± 2 ° c ., ph 7 - 7 . 5 ). the natural light - dark cycle was simulated ( 12 h light : 12 h dark ). fish were fed twice per day with a commercial feed ( efico , biomar , spain ). parasite - free fish were experimentally infested by holding the parasite - free fish 25 days in a 100 l tank that also contained fish showing high - intensity infestation ( 20 uninfected fish to 10 infected fish ). twenty ( 20 ) fish were then sampled at random for determination of infestation intensity , which was determined to be a high intensity infestation in at least 50 % of fish . fish were anaesthetized by immersion in bath with 100 ppm of tricaine methanesulfonate until respiration became weak . a mucus sample was then taken by gently scraping the body surface after examination of a sample area of 24 × 32 mm . the sample was mixed with 30 μl of distilled water on a slide , cover - slipped and examined to optic microscopy ( 400 ×). each treatment was assayed in 20 infected fish maintained in 100 l tanks with aeration in closed systems of water . the fish received feed containing three different treatments . the first group received a diet with 100 ppm of propyl propane thiosulphonate ( ptso ), the second received a diet supplemented with 300 ppm of ptso , and the third received a diet with 300 ppm of metronidazole . all treatments were applied during a 10 day period . in all cases , feed was supplied at 2 % of total body weight per day . simultaneously , a positive control assay ( also on 20 infected fish treated identically , but without any ptso ) and negative control assay ( with 20 uninfected animals ) were performed . tanks conditions were identical to those during the acclimatization period . throughout the assay period the fish were monitored regularly to ensure that the fish were eating the food , and to check for signs of toxicity . the objective of example 3 was to examine the activity of propyl propane thiosulphonate ( ptso ) and propyl propane thiosulfinate ( pts ) against l3 larvae of type i anisakis and hysterotylacium aduncum to explore the possible use of these compounds for prophylaxis treatments . l3 of anisakis type i and hysterotylacium aduncum were collected by dissecting the fish micromesistius poutassou ( blue whiting ) and trachurus trachurus ( mackerel ) fished in the cantabric sea , and selecting only larvae with a length greater than (& gt ;) 2 . 0 cm in the case of anisakis , and greater than 0 . 8 cm for hysterotylacium . larvae were axenised in antibiotic solution ( iglesias et al ., 1997 ), introduced into polystyrene plate wells with 2 ml of sterile solution of 0 . 9 % nacl and the different concentrations of pts alone , ptso alone , and both pts and ptso ( 75 , 200 , 300 and 500 ppm ) and then incubated at 36 ° c . in a 5 % co 2 atmosphere . as controls , larvae were assayed without test compound under identical experimental conditions , and using only the solvent dmso 1 % ( dimethyl sulfoxide ). larvae were examined under stereoscopic microscope at 4 , 8 , 24 , and 48 hours to test the biocidal effect of the compounds . larvae with no mobility at all were considered dead . each dilution was tested three times on larvae from fish captured on different days . the administration of pts and ptso demonstrated anti - parasitic activity against stages of the life c . rogercresseyi . for example , fig3 illustrates the survival probability of caligus rogercresseyi copepodites at different concentrations of pts and ptso . in addition , fig4 illustrates the survival probability of caligus rogercresseyi nauplius i at different concentrations of pts and ptso . in further illustration of the exemplary results , fig5 illustrates the survival probability of caligus rogercresseyi nauplius ii at different concentrations of pts and ptso . finally , fig6 illustrates the survival probability of caligus rogercresseyi adults at different concentrations of pts and ptso . it is further noted that ptso demonstrated antiparasitic activity against icthyobodo necator in rainbow trout with significant reduction of infestation intensity as shown in table 1 . for each treatment and each dosage tested , infestation intensity 24 hours after the end of the assay is shown for each of the 20 fish included in each assay . also shown is infestation intensity : high , moderate , low , minimal and zero ( i . e . no icthyobodo necator detected in body scrapings ). of note , infestation intensity was based on a 5 - point scale , as follows : zero equals ichthyobodo necator not being detected in the sample ; minimal equals only 1 individual of i . necator being detected in the sample ; low equals more than 1 individual of parasite being detected in the sample , the average number per microscope field being less than 10 ; moderate equals an average number of individuals per microscope field of 10 to 50 ; high equals an average number of individuals per microscope field of more than 50 . further , fig7 illustrates assay effectiveness at different concentrations of ptso on the control of icthyobodo necator in rainbow trout . in addition , pts and ptso demonstrated significant anti - parasitic activity against l3 larvae of hysterotylacium aduncum and anisakis type i , as shown in fig8 . specifically , fig8 illustrates in vitro activity of pts , ptso , and a mixture of both ( 1 : 1 ) against l3 larvae of hysterotylacium aduncum at the concentration tested ( 75 ppm ), where activity is expressed as mortality . in addition , in fig9 , in vitro activity of ptso against l3 larvae of anisakis type i at the concentrations tested ( 200 , 300 and 500 ppm ), where activity is expressed as mortality is illustrated .
a method for reducing parasites in aquatic animals is provided . the method includes reducing a plurality of parasites infecting an aquatic animal by administrating to the aquatic animal a compound comprising propyl propane thiosulfonate having the formula r — soa - s — r , where r represents n - propyl group and a is 2 . in yet a different embodiment , a method for reducing a plurality of parasites infecting an aquatic animal includes administrating to the aquatic animal a compound comprising and propyl propane thiosulfinate having the formula r — soa - s — r , where r represents n - propyl group and a is 1 . in even yet another embodiment , a method for preventing a plurality of parasites in aquatic animals is provided and includes administrating to an aquatic animal a compound including pts . in a different embodiment , a method for preventing a plurality of parasites in aquatic animals is provided and includes administrating to an aquatic animal a compound including ptso .