TR82-1 7^ // MICHIGAN DEPARTMENT OF NATURAL RESOURCES Fisheries Division Technical Report: No. 82 -1 January, 1982 THE HISTORY OF INFECTIOUS PANCREATIC NECROSIS (IPN) VIRUS IN MICHIGAN John G. Hnath, Fish Pathologist SUMMARY The first positive confirmation of IPN in Michigan was at Marquette Hatchery in 1962. However, high mortality, tentative diagnoses, and an apparent dispersal of IPN from Wolf Lake Hatchery suggested that IPN appeared there first in 1958. Apparently IPN was not endemic to Michigan but arrived at Wolf Lake with brook trout from Pennsylvania. Since then it has been diagnosed at eight hatcheries and in adult coho salmon from Lake Michigan. THE HISTORY OF INFECTIOUS PANCREATIC NECROSIS (IPN) VIRUS IN MICHIGAN John G. Hnath, Fish Pathologist INTRODUCTION "Infectious pancreatic necrosis (IPN) is an acute, highly contagious disease usually characterized by an explosive onset of mortality in salmonid fry. The striking clinical picture of severe illness associated with IPN and its occurrence as epizootics with high mortality, are dreaded and have endangered populations of fish exposed to its ravages. Epizootics in hatchery fish during the past 30 years have characterized it as a major infectious disease of salmonid fishes." (Sonstegard 1970). Because of a lack of suitable techniques for detecting salmonid viruses, litcle was known of this disease prior to M'Gonigle (1940) who is credited with the first description of the disease by the classic symptoms and pathology. However, the virus was not isolated until later (Wolf et al. 1960). Since then, reports of this disease have been numerous and knowledge about the disease has expanded greatly. For a good review of the disease, refer to Sonstegard (1970). The intent of this paper is to trace the history of IPN in the State of Michigan. As with most historical information, much information on IPN has been lost. A history of the disease is desirable because of recent detections of IPN in Michigan, an increased awareness of fish disease problems, and recent state and federal laws regulating transportation and importation of serious fish diseases. RESULTS According to remaining records, IPN was not definitely confirmed in Michigan until May 24, 1962, at the Marquette State Fish Hatchery. However, explosive epizootics with the classical symptoms of IPN infection occurred earlier, and can be presumed (not confirmed) to have been due to IPN. The earliest "suspicion" of IPN in Michigan was in May 1960, but Richard 0. Anderson (personal communication), former manager of the Wolf Lake State Fish Hatchery, is of the opinion that IPN was present at Wolf Lake when he arrived there in June 1959. It is his opinion that IPN was not endemic in Michigan, but had been imported with a strain of brook trout from Pennsylvania. Anderson's suspicions are reinforced by Lyle L. Pettijohn (personal communication) of the Leetown National Fish Hatchery, who suggested that if Michigan received fish or eggs from Pennsylvania, they were probably "... derived from IPN carrier blood stock as the presence of IPN at Pennsylvania State units is well documented." The suspicion of importation of IPN into Michigan is also reinforced by our hatchery records for Wolf Lake (Table 1). During the period from 1951-1957, -2 - mortalities of brook trout from egg through 3 months were quite low. Beginning in 1958 the losses were appreciably higher. The picture for brown trout at Wolf Lake was essentially the same as for brook trout, except that the losses were excessive for only the year after the first high losses of brook trout. The story for rainbow trout is less clear, but no excessively high losses occurred in the period of 1951-1958. The above information provides some support for the assumption that IPN entered Michigan with brook trout in late 1958. Since infectious viral diseases of salmonids were unknown at that time, it is not surprising that no mention of IPN virus was made. However, high mortalities after 1957 as compared to low mortalities in earlier years, indicated that a new cause of mortality appeared in 1958. Since 1960, when the virus was first isolated, IPN was confirmed many times at most of our State fish hatcheries (Table 2). It is interesting to note that of all the confirmed IPN virus cases in Michigan, only those at Watersmeet were from fish that had never been at Wolf Lake. However, Watersrneet had received fish from Wolf Lake on other occasions. The facts that Wolf Lake fish were commonly infected, even at other stations, and that the earliest IPN diagnosis in Michigan was from Wolf Lake strongly support the suspicion that Wolf Lake was the center of IPN dispersal in Michigan. DISCUSSION The story of IPN in Michigan is a growing one with many facets still being explored and many unknowns yet to be discovered. For instance, the detections of IPN virus in coho salmon at the Sturgeon River Rearing Station and in adult coho salmon from Lake Michigan raise many questions. Where did this IPN originate? Is it from the Wolf Lake center, or from somewhere else? Does the virus in coho pose a threat to other fish species? Another question is what happened to IPN virus in Michigan between 1967 and 1971 when there was no mention of it in our records? Did it disappear, or was there a balance reached between our host fishes and the virus so that excessive mortalities no longer occurred? Perhaps the virus remained unnoticed because our management techniques were more suitable for fish than for viral epizootics. I think that this latter factor is important because infectivity trials with the 1971 isolate of virus from wild coho using young brook and brown trout showed mortalities as high as 50% (Hnath letter of 2-25-72, ref. #7201). The available records of examination for IPN virus in Michigan from 1960 to 1971 are given in appendix I. ACKNOWLEDGMENTS Special thanks go to Warren G. Yoder for his assistance throughout the compilation of the data for this report, and for his review of the final draft. Thanks also to Tom Stauffer for his editorial review of the manuscript. -3 - Table 1.--Percentage mortality ' of trout from egg to 3 months at Wolf Lake Hatchery, 1951-1964. Year(s)Species of trout Brook Brown Rainbow 1951-1957 8-24 1951-1958 4-20 4-29 1958 65 1959 66 45-100 18-21 1960 b 16-47 19-44 1961 21-28 1962 8 11 1960-1963 8-14 1964 43-46 For individual years, mortality is the range for one to three lots. /IPN was tentatively diagnosed in one lot of brook trout and was suspected in the lots of rainbow trout. -4 - Table 2.--Locations in Michigan where IPN was diagnosed, 1960-1980. Loc ation and date Species Designation or lotN6ý/ Report No.-! Baldwin Station 9-16-64 Brook Little Manistee weir 4-7-75 10-5-77 Steelhead Coho Marquette Hatchery BKT- 64-PA-WL-OD-BA STT (wild) Lake Michigoan spawners BKT - 62-WL(PENN) -T H RBT-63-WL(Wisc)-CD P-BKT-W-77--AS-CD P-BKT-D-77-PA-OD (fall) P-BKT-D-77-PA-CD (spring) 5-24- 62 112 Brook Oden Hatchery 3-11-63 4-19-78 4-19-78 4-19-78 Rainbow Brook Brook Brook Platte River spawning' wei: 10-21-75 10-26-'76 10-25-77 10-26-78 10-28-80 Coho Coho Coho Coho Coho Lake Lake Lake Lake Lake Michigan Michigan Michigan Michigan Michigan spawners spawners spawners sp awners spawners Platte River Hatchery SC-04-75 SC-10-77-2 51 71 SC-04-78 SC-04-78 SC-0 4-78 SC-11-75 SC-09-76 SC-11-77 SC-09-78 SC-08-80 SC-13-71 SC-02-73 SC-05-74 SC-05-74 SC-07-75 SC-07-75 SC-01-76 SC-01-76 SC-04-77 SC-04-79 SC-05-79 SD-14-70 SR SD - 11-71 SC-06-72) SC-06-72 11-4-7 1 1-2-73 to 2-2-73 8-19-74 8-19-74 7-7-75 7-7-75 2-10-76 2-10-76 2-9-77 3-26-79 5-1-79 Coho Rainbow Coho Coho Steelhead Coho Steelhead Coho Coho Rainbow Coho Lake Michigan spawners RBT-71-HA-CH-PL COM -73-W-PL CO-WC-73-W-PL STT - 74-LM-PL COM-74-PL (outdoor) S TT - W -75- LM - P L COM-W-74-PL P-COM-W-75-PL P-RBT -D- 77-HA-OD-WL--PL P-COM-W-77-PL CO - 69-WL-CH-SR. CO-70-PR-WL-CH-SR RBT - 70 -HA-WL-PR-WL-'C('-'H-SR RBT-71-HA-CD-CH-SRT Z CC- 71-PD-SR - Sturgeon River Rearing Station 7-30-70 7-7-71 12-3-71 9-5-72 9-5-72 Coho Coho Rainbow Rainbow Coho (continued. ne-x - -5 - Table 2.--continued - --- Location and date Species Designation or lot Report No. ' - -- SturQ'eon River Rearinf' Station, cont. (Lj - - - - - - ILD - - - - - - - 9-5-72 9-5-72 3-12-73 3-12-73 2-12-75 Brown Brook Coho Coho Rainbow BNT-71-GY-SR (EXP) BKT-71-GY-SR (EXP) CO-71-PL-SR CO-72-(WA')-WL-SR RBT -73-MI Thompson Hatchery 3-27-63 3-27-63 3-29-72 to 5-31-72 3-12-73 3-12-73 3-12-73 10-18-73 8-12-75 8-12-75 8-12-75 8-12-76 8-12-76 Brook Rainbow (Brook (Brook (Rainbow (Splake Brook Brook Brook Coho Coho Coho Rainbow Rainbow Coho BKT - 63-WL-TH RBT - b2-WL-TH BKT -70-TH-CK (creek) BKT-69-Brood (creek) RBT-70-HA-WL (creek) SPL-70-MQ (creek) BKT-71i-EXP (creek) BKT-70-Brood (creek) BKT -72 (springwater) Lake Michigan spawners COM- 74-PL-OD-CH-TH CGA-74-TH-OD-CH-TH RBT-74-HA-GD-TH P-RBT-D- 75-HA-OD-CH-TH P - C GM - W -75- PL - T H BKT-63 St. Croix Falls BKT (PENN. STRAIN) BNT (Unknown) ATS-69-D-DQ-WL ATS-71-D-DQ-WL P- CGM-W-75-PL-WL P- CGM-W-75-PL-WL P-BNT- 77-D-HA-OD-WL P-RBT -77-D -HA-GD -WL SC-06-72 SC-06-72 SC-01-73 SC-01-73 S C - 02 - 75 76 77 SC-03-72 SC-03-72 SC-03-72 SC-03-72 SC-04-73 SC-04-73 SC-04-73 SC-11-73 SC-08-75 SC-08-75 SC-08-75 SC-07-76 SC-07-76 Watersmeet Hatchery 6-24-63 Brook Wolf Lake Hatchery 5-?-60 7-24-63 5-18-72 8-20-73 7-26-76 11-23-76 2-13-79 2-13-79 Brook Brown Atlantic Atlantic Coho Coho Brown Rainbow W L SC-02-72 SC-09-72 SC-06-76 SC- 06-76 SC-01-79 SC-01-79 aAbbreviations for fish are as follows: ATS Atlantic salmon, Sweden; BKT = brook trout; BNT = brown trout; CGA = coho, Alaska; CGM = coho, Michigan; CG-WC = coho. West Coast; RBT = rainbow trout; SPL splake and STT = steelhead. Michigan hatchery abbreviations are: BA = Baldwin, CH = Charlevoix, GY Grayling, HA = Harrietta, MQ =Marquette, GD den, PA Paris, PL Platte, SR = Sturgeon River, TH = Thompson and WL = Wolf Lake. Other abbreviations are: AS = Assinica, D = domestic, DQ = Domtar Hatchery, Quebec, Canada, CK = creek, LM = Little Manistee, P = production, W wild, WNA = Washington. The numbers represent brood years. 4 Patholooical reports on flie at Wolf Lake Fish 0at'iolo2i Lab. -6 -LITERATURE CITED M'Gonigle, R. H. 1940. Acute catarrhal enteritis of salmonid fingerlings. Trans. Am. Fish. Soc. 70:297-303. Sonstegard, R. A. 1970. Descriptive and epizootiological studies of infectious pancreatic necrosis of salmonids and lymphosarcoma of Esox masquinongy. Ph.D. thesis, University of Guelph, Ontario. 215 pp. Wolf, K., C. E. Dunbar, and S. F. Snieszko. 1960. Infectious pancreatic necrosis of trout. I.A tissue culture study. Prog. Fish-Cult. 22: 64-69. -7 - Appendix I.--Records of examination for IPN virus in Michigan from 1960 to 1971. Date, fish size \ Lot designation Percentage mort ality Diagnosis 'ý%nd diagnostician d Report Nc. NV Baldwin Station 8-11-61(F) B] 6-3-64(F) BI 7-28-64(F) BI 9-16-64(F) BI NT(unknown) [{T -64-WL- (PENN) -OD I{T - 64-WL-OD-BA KT - 64-PA-WL-OD -BA 9-16-64(F) BNT-64-HA-BA Grayling Hatchery 5-00-60(L) BKT(unknown) 7-18-60(F) BKT(unknown) 4-23-62(L) RKT (unknown) (up river) 4-27-62(L) B KT (unkno w n) (up river) Harrietta Hatchery 4-11-63(?) RBT-63-WL 5/2 wks Symptoms of JPN(A) 100/day IPN(A) Possible IPN(A) Tissue sections indicate possible IPN(A) <1 Indications of IPN; pancreas will be sectioned(A) Symptoms of IPN specimens sent to E(A) Symptoms of IPN(A) 10 IPN suspected(A) 10 2/day Dam 40 /mo 1 4-16-63(?) 7-26-65(F) 8-30-65(F) 12-29-65(F) 3-1-67(?) RBT-63-WL RBT-65-HA-(MAN) Eggs from Tippy RBT -65-HA(MAN) RBT-66-HA- (WISC) -TH RBT (unknown) IPN behavior and symptoms(A) Specimens to be sent to LaCrosse(?) Sections show no IPN(A) Symptoms of IPN(A) Indications of IPN.(A) Possibly IPN(A) Negative (E) Ne gative (A, E) r 24 102 109 112 111 E 47 79,80 126 128 134 E Marquette Hatchery 5-24-62(L) BKT-62-WL- (PENN) -TH over 2 IPN positive(E) 51 Oden Hatchery 7-11-60(F) E 5-25-62(F) E 6-20-62(F) 1 3-1-63(?) I 3-11-63(L) I 2-24-66(F) 1 3KT (unknown) 3KT (unknown) 3KT(unknown) RBT(unknown) RBT- 63-WL-(WISC) -OD RBT -66-HA- (WISC) -OD 3 <1 Symptoms of IPN(A) none IPN typical behavior(A) 50 IPN suspected among fish when in the building(A) 54 Possible JPN(A) 65 Sections show IPN (Vo-1)(A) 71 Possible IPN(L) L Behavior resembles JPN(A) 140 IPN negative(E) E (continued- nex t page) -8 - Appendix I. - -continued Date, Lot Percentage Diagnosisýr and Report fish size designation ~ mortality diagnostician \d No.'9' Platte River Hatchery 11-4-71(A) CO-68-PR-WL-CH Sturgeon River Station 7-30-70(F) 9-28-70(F) 7-7-71(F) 12- 3-71(?) CO-69-WL-CH-SR CO-6 9-WL-CH-S -R CO-70--PR-WL-CH-SR RBT -70-HA-WL-PRW L - C H - SR low 41/day low Thompson Hatchery 7-16-60(F) BKT(unknown) (Fox R.Sta.) 3-27-63(Y) RBT-62-WL-TH (unit 2) 3-27-63(F) BKT-63-WL-TH (unit 2) 2-28-67(L) RBT-67-HA-(WISC) -TH Watersmeet Hatchery 6-24-63(F) BKT-63-St.Croix Falls 8-13-64(?) BKT (unknown) Wolf Lake Hatchery 5-00-60(F) BKT(PENN strain) 5-00-61(F) BKT(PENN strain) 100-300/ day >20 IPN positive, CPE and characterization (H) IPN suspect virus(H) IPN confirmed(H) LPN positive(H) Confirmed (E) IPN positive--CPE typical of IPN(H) Mucous and whir"ling suggests IPN(A) Sections show IPNJ(A) Tissue sections confirmed IPN slide VT-1(A) Possibility of IPN, sample sent to E(A) IPN slide Vwm 1(A) Tissue section for IPN slide Vwm-2(A). No indication that IPN was diagnosed (Y) IPN tentatively confirmed, samples sent to E(?) IPN check requested of E by WL 5-15-61(?) IPN(A) Mortality due to IPN(A) IPN-tissue section of pancrease, slide Vwl-1(A) SC-13-71 SD-14-70 IPN SD-5-71-1 SR&IPN SD- 11-71 TH 77, T. H 76 1729. WM111 Slide index WL W L W L W L Slide index 2 25 5-00-62(F) 6-00-62(F) 7-24-63(?) BKT(PENN strain) RB T (unknown) BNT (unknown) --- = fry, F = fingerling, Y=yearling, A = adult. b V Abbreviations for fish are as follows: BKT = brook trout; BNT = brown trout; CO = coho; RBT = rainbow trout. Hatchery abbreviations are: BA = Baldwin; CH - Charlevoix; HA = Harrietta; GD = Oden; PA = Paris; PL = Platte River; SR = Sturgeon River; TH = Thompson; WL = Wolf Lake. Other abbreviations -are:MAN = Manchester, Iowa National Fish Hatchery; PENN = Pennsylvania; WISC = Wisconsin. The numbers represent brood years. (continued, next aue) -9 -$/CPE = Cellular pathological effect; IPN = Infectious pancreatic necrosis. SA = Dr. Leonard N. Allison (MDNR, retired); E = Eastern Fish Disease Lab (USBSFW); H = Mr. John Hnath (MDNR); L = LaCrosse, Wisconsin USBSFW (Dr. Robert Piper, USBSFW) and Y = Mr. Warren Yoder (MDNR). Numbered reports are no longer on file. Reports with the prefix "SC", "SD", and indexed slides are on file at Wolf Lake Fish Pathology Lab.