MFR PAPER 1142 and other hemolymph proteins are not affected significantly. As a result of the loss of hemolymph clotting power, the risk ofa fatal hemorrhage is introduced Gaffkemia, the Fatal Infection of in the event of wounding. Lobsters (Genus Homarus) Caused by THE INFLUENCE OF Aerococcus viridans (var.) homari: A Review ENVIRONMENTAL FACTORS Variations in temperature and salin ity have been examined and shown to JAMES E. STEWART have a marked effect on the disease. Since development of gaffkemia infec tions in lobsters is strictly temperature Abstract-A review of recent literature is given concerning the fatal sep dependent, the disease remains largely ticemia in lobsters caused by the bacterium, Aerococcus vi ridans (var.) homari dormant during the cold-water months. (formerly Gaffkya homari). Decreasing salinity may increase or decrease the At 1°C the pathogen in vivo does not time to death in lobsters, depending upon whether or not the animals have increase in numbers and the infection is been infected before or after the salinity change occurred. As the disease subpatent until the temperature is in progresses, glycogen, ATP, glucose, lactic acid, and nonprotein nitrogen all creased. Then it flourishes and kills the decrease. Impairment of the major metabolic processes is suggested as the host in a time span directly dependent probable cause of death. A degree of host resistance can be induced by upon the ambient temperature. The administration of appropriate vaccines. temperature influence on means for times to death (reported in days) were: INTRODUCTION tegument ofthe host which permit entry 172 at 3°C, 84 at 5°C, 65 at 7°C, 28 at to the hemolymph. The exposure to A. lOoC, 12 at l5°C, and 2 at 20°C. Addi Gaffkemia is a fatal bacterial disease viridans (var.) homari must come simul tionally, the pathogen easily survives which periodically causes heavy mor taneously with or soon after integumen periods at 1°C, in vivo or in vitro, which talities among American and European tal rupture for the pathogen to circum are more than sufficient to carry the bac lobsters (Homarus americanus and vent the lobster's rapid and effective terium from one warm-water season to H omarus vulgaris, respectively). The wound healing mechanism. Transmis the next. disease and the causative agent, sion does not occur when the lobster Salinity also has an influence on the Aerococcus viridans (var.) homari ingests infected material since the acid course ofthe disease; the lobster, which (formerly Gaffkya homari)', were de ity ofthe gastric fluid (pH 5.0) is lethal to is a relatively euryhaline animal, is a scribed originally by Snieszko and A. viridans (var.) homari. Despite the poor osmoregulator or conversely an Taylor (1947) and Hitchner and pathogen's lack of invasive powers, the "osmoconformer" (Dall, 1970) .. De Snieszko (1947). The septicemic nature development of epizootics is aided by spite its osmoconformity, adaptations of the disease and the taxon assigned to the aggressive behavior of lobsters, to salinity reductions occur slowly and the pathogen prompted the name "gaff which provides wounds for entry, and require 75 h at 15°C for complete accli kemia" (Roskam, 1957) for the disease. by the fact that normal lobsters have no mation (Dall, 1970). It would be ex Severe losses from gaffkemia are ex apparent resistance to the pathogen pected then that salinity change should perienced periodically in commercial after entry. Small numbers of a virulent in some way alter the pattern of the dis lobster units. Two recent reviews strain of A. viridans (var.) homari, ease. The nature of the change, how (Stewart and Rabin, 1970; Sindermann, consisting of 10 or less per kilogram of ever, was quite unexpected (Stewart 1971) have dealt in depth with this dis the lobster's weight, injected into the and Arie, 1973a). When lobsters were ease. The background material from hemolymph are sufficient to ensure a acclimated from the normal coastal sa these articles is summarized below. The fatal infection. Injection, however, of linity level of31.80f0o to reduced salinity causative agent, A. viridans (var.) large numbers (6 x lOS/kg) does not ac levels (26.10100 and 21.50100) prior to in homari, is a gram positive, catalase celerate the infection sufficiently to fection, the times to death upon infec negative, beta-hemolytic, tetrad form produce a significant decrease in time to tion were shortened in proportion to the ing coccus which appears to possess no death. There are no external signs ofthe salinity reduction (Fig. I). Control ani exoenzymes (Snieszko and Taylor, disease with the exception that as the mals exhibited no mortalities due to sa 1947; Hitchner and Snieszko, 1947; infection proceeds the lobsters become linity changes. In contrast, when the Hucker, 1957; Stewart et a!., 1969b). lethargic and progressively weaker until salinity was reduced after infection an This lack of exoenzymes and conse they die. entirely different pattern developed. quent lack of invasive powers results in As the disease develops, the lobster Reduction in salinity to 26. 10100 after the bacterium being transmitted only suffers a massive decrease ofcirculating through breaks or ruptures in the in- hemocytes, resulting in impairment of James E. Stewart is with the De partment of the Environment, the clotting mechanism by the removal Fisheries and Marine Service, of the clot initiating factor contained in 1 See Stewart and Arie (1974) for review of name Halifax Laboratory, Halifax, Nova change. the hemocytes. The fibrinogen levels Scotia, Canada. 20 _ 15 20 26.1 %0 In E A 31.8 %. (Fig. 6), and the loss of adenosine >- "- - .. In triphosphate (ATP) from these tissues o a:: 16 w (Figs. 7, 8, and 9). The ATP loss was :r :I'" I- 10 :::> most significant in the hepatopancreas. .. z 12 W o ..J Parallel to these changes is the decline o .. en 8 10.0 >- of the nonprotein nitrogen coincident I B: « W w e :I l- 4 with the disappearance of glucose and ~ I 9.0 the decline of the lactic acid concentra :I: Z '" I- 0 tions of the hemolymph (Fig. 10). ..w 8.0 g « :I 0 L....i~----~---,L--_--.J ..J W e 31.8 26.1 21.5 28 B 31.8·/•• --+ 21.5 %. DISCUSSION WATER SALINITY ("10.) AT 15 C 0 I- 24 The development of the pathogen in Figure 1.-Mean limes to death (MTD) for lobsters w :::;: vivo (Stewart and Arie, 1973b), the abil Infected with A. vlrldans (var.) homarl and accli 20 mated to water sallnilies of31.8, 26.1 and 21.5'/" at I- ity of the pathogen to utilize glucose, (_~ 1S·C prior to Injection MTD; bars indicate z but not complex polysaccharides log bacterial numbers In lobsters). A total of 120 (60 « 16 infected and 60 control) animals were used in w (Aaronson, 1956; Stewart and Cornick, groups of 10 lobsters (4 groups at each salinity :::;: 12 level). All groups were Injected on the seventh day 1972), its reliance on the nonprotein ni dated from the beginning of the salinity change. trogen (Stewart, Arie et aI., 1969; Each point represents the mean value plus slane 8 dard error (SE) for a group of 20 Infected lobsters. Stewart, Foley, and Ackman, 1969) Unlnfected controllobslers Bre not represented on 4 this graph since none of these animals died coupled with its inability to utilize pro (Stewart and Arle, 1973a). teins (Stewart, Arie et at. 1969; Stewart, 0 ° 2 4 6 8 10 12 Foley, and Ackman, 1969) indicate the DAY (POST INFECTION) OF' SALINITY REDUCTION following course of events. After entry infection initially decreased the times to Figure 2.-Mean times to death 'or lobsters in into the hemolymph the pathogen is death and then progressively increased fected with A. vlrldans (var.) homarl and SUbjected concentrated in the hepatopancreas and to water salinity reduction postlnfectlon (over the the times to death (Fig. 2a), while reduc course of 4 h) on the days designated. Columns the heart, possibly as the result of tion to salinity 21.5%0 after infection at represent mean values plus SE for groups of In phagocytic action. The subsequent de fected lobsters only, since none of the control anle any of the post-infection times in mals died. (a) Reduction from normal 31.8 to velopment of bacteria in these two tis 26.1°/00. (b) Reduction of normal 31.8 to 21.5'100. creased the time to death (Fig. 2b) over Each vertical column represents a separate group sues is immediate and rapid, taking that observed for infected lobsters kept of 10 lobsters plus SE (Stewart and Arle, 1973a). place at the expense offree glucose and throughout at salinity 31.8%0 (Fig. I). nonprotein nitrogen. The latter is prob An extensive series of experiments in order in which the dual stresses of dis ably present in greater concentrations in cluding sequential measurements of ease and salinity reduction are applied is the hepatopancreas than in the heart, hemolymph nonprotein nitrogen, total a key factor in understanding the which might account for the difference carbohydrates, glucose, lactic acid, and phenomenon. A point of departure for between the final bacterial numbers in serum osmolalities were performed dur further studies might lie in a thorough these two tissues. As the bacterial num ing the course of the infections using examination of infected lobsters sub bers increase, especially in the both infected and healthy anjmals in an jected to 26.1 %0, where a decreased hepatopancreas, the capacity of the attempt to discover the basic reasons time to death occurs first, followed by a phagocytes to transport the pathogen to for the different responses (Stewart and change in response resulting in in and retain it in the hepatopancreas is Arie, 1973a). The growth of the creased times to death about the sixth lost through the increasing destruction pathogen in the infected animals sub postinfection day (Fig. 2). of hemocytes, thereby permitting the jected to the reduced salinities was ex pathogen to flourish in the hemolymph. amined, but it did not differ materially PATHOGEN GROWTH AND This aspect of the interaction between from that in infected animals kept at the BIOCHEMICAL CHANGES the pathogen and the phagocytic normal salinity (Stewart and Arie, IN THE HOST mechanism is substantiated by the coin 1973a). Subjection ofA. viridans (var.) cident exponential development of the homari to a much wider range ofsalinity It has been concluded that death of pathogen in the hemolymph and the values in vitro did not impair its growth lobsters infected with A. viridans (var.) sharp decline in hemocyte numbers (Stewart and Arie, 1973a). Althol,Jgh the homari is the result of an unsuccessful (Stewart, Arie et aJ., 1969). Glucose is data gained from measuring the various competition on the part of the lobsters the only fraction of the total carbohy physiological parameters and the for their own readily available energy drates in the hemolymph used by A. growth of A. viridans (var.) homari in reserves (Stewart et aI., 1969a). The viridans (var.) homari (Stewart and relation to salinity change was interest evidence for this is found in the pattern Cornick, 1972; Stewart and Arie, 1973a) ing, particularly in terms of the re of development of the pathogen in vivo which the lobster can sustain at the ex sponses of the noninfected control lob in the skeletal muscle, cardiac tissue, pense of its glycogen. After exhaustion sters, none of this data nor a search of hepatopancreas and hemolymph (Fig. ofthe host's glycogen and subsequently the literature suggested an explanation 3). Concomitant with the development glucose, the pathogen can utilize the for the apparently contradictory results of the pathogen is the decline of limited supplies of lactic acid in vitro of the combined studies of salinity re glycogen in the hepatopancreas (Fig. 4), and apparently also in vivo (Stewart and ductions and disease. Obviously the the heart (Fig. 5), and the tail muscle Cornick, 1972; Stewart and Arie, 21 10 TAIL MUSCLE
~ 300 en 0 en lIJ ...--o--:li. 0 0 ::> 1: • • .... en o'" en 0200 I
Figure 3.-Growth curves Illustrating the development 01 A. vlrldans (var.) homarf In the tissues ollnlected Arie et aI., 1969), while hemolymph lobsters (Stewart and Arle, 1973b; Stewart, Arle et aI., 1969). proteins, a ready reserve for the lobster (Stewart et aI., 1967), are drawn upon HEPATOPANCREAS only to a slight degree (Stewart, Arie et 400 1800 aI., 1969). The possibility of replenish w 1600 ing the reserve materials from external :::> w en :::> sources is lost to the lobster by its re ~ .... 300 ~ 1400 fusal to feed after the onset ofthe infec .... CONTROLS o'" 01200 tion. At the standard temperature of 2 o "- o these studies, 15°C, lobsters will feed on ~200 ..... 10DO the second day after being infected but Z E'" W z 800 refuse food thereafter (Stewart et aI., '"o W o ~ 1972). The presumed reason for the re >- 100 '"o 600 ...J \ o fusal offood is the development of mas I~ INFECTED ,.. i ...J '" C) 400 sive numbers of bacteria in the I--I-I", hepatopancreas, an organ which in o L-L-----:'_----'-_--'--_-'---_L------.JL-----:'---.J 200 o 6 8 10 12 [4 crustaceans encompasses the function DAYS of liver and pancreas in vertebrates and 6 8 10 12 14 Figure 4.-Glycogen levels In the hepatopancre DAYS also plays a prominent part in primary stlc tissue 01 inlected and control lobsters. Each point represents the meen value lor live animals food absorption, a role fulfilled in ver Figure 5.-Glycogen levels in the heart tls8ue 01 plus SE. The Inlected animals are those lor which Inlected and control lobsters.The Inlected animals bacterlsl numbers are given in Figure 3 (Stewart tebrates by the small intestine (Vonk, are those represented In Figure 3 (Stewart and and Arle, 1973b). Arle, 1973b). Each point plus SE represents a 1960). A soluble bacterial toxin would group 01 live lobsters. appear to be ruled out as a direct cause 1973a). The drain upon the carbohy of death, since filter sterilized serum drate reserves in turn prevents the pro of biosynthesis, detoxification, and re removed from heavily infected lobsters duction of lobster hepatopancreatic pair (Stewart and Arie, 1973b). Lipid and then injected into healthy animals in ATP and suggests massive impairment reserves remain unchanged throughout amounts equal to more than 13% of the of the vital hepatopancreatic functions the course of the infection (Stewart, lobsters' body weights had no adverse 22 6 .- -- -\ CONTROL glutinin activity and phagocytic action, :J: , _. " ::Ii however, does playa role in protecting > . \ / ...J W 12 o lobsters against infection from microor ::Ii '.1 ::::> w Ul :J: 4 ganisms which otherwise could be as ~ 10 e pathogenic as A. viridans (var.) homari t- o o (Cornick and Stewart, 1968; Stewart .. '- '- 8 W ~ and Zwicker, 1972). The most recent ...J w o 6 :IE o studies on induction of resistance to A. '"U
MFR Paper 1142. From Marine Fisheries Review, Vol. 37, Nos. 5- 24