SINDERMANN: POLLUTION-ASSOCIATED DISEASES AND ABNORMALITIES 



mal effluents on parasitism of largemouth bass, 

 Micropterus salmoides, by the acanthocephalan 

 Neoechinorhynchus cylindratus were examined by 

 Eure and Esch ( 1974). Parasite densities were sig- 

 nificantly higher in fish from heated water during 

 the winter months, a possible reflection of greater 

 densities of larval parasites and intermediate host 

 populations in the effluent. River pollution from 

 domestic and industrial sources was considered to 

 be a contributing factor in increased parasite bur- 

 dens found in fish from areas of heaviest pollution 

 in Poland (Dabrowska 1974). 



For marine species, good evidence relating pol- 

 lutants with changes in parasite abundance is 

 scarce. Results of an extensive survey of external 

 parasites and disease conditions in North Sea fish 

 (Moller''') did not disclose clear-cut relationships 

 between parasitism and pollution, although the 

 higher prevalence of vibriosis and lymphocystis in 

 southern sectors which are most polluted indi- 

 cated a possible influence of pollution. Other fac- 

 tors seemed responsible for differential abun- 

 dances reported for the larger external parasites. 



Several parasites of estuarine fishes from the 

 Gulf of Mexico were examined by Overstreet and 

 Howse (1977) in a search for associations with 

 environmental pollution. Samples of Atlantic 

 croaker were collected in 1970-72, and again in 

 1975. Large variations in prevalences of helminth 

 parasites occurred, but clear associations with pol- 

 lutants and changes in pollutant levels were not 

 established. A myxosporidan protozoan seemed to 

 be more promising. Infections of sheepshead min- 

 nows by Myxobolus lintoni were very abundant in 

 one polluted bayou of Mississippi, but were absent 

 in seemingly healthy habitats. 



The stalked peritrich ciWdiie Epistylis sp., men- 

 tioned in an earlier section in connection with fin 

 erosion and red sores, seems to be related to high 

 organic content and possibly other stresses in 

 freshwater and brackish water habitats. The 

 ciliate, together with secondary bacterial invaders 

 (principally Aeromonas liquifaciens (= A. hy- 

 drophila), produces a hemorrhagic hyperplastic 

 condition beneath the scales that is referred to as 

 red sore (Overstreet and Howse 1977). The ciliate 

 infests a wide range offish species in low salinity 

 waters of Mississippi, especially centrarchids, 



"Moller, H. 1977. Distribution of some parasites and dis- 

 eases of fishes from the North Sea in February, 1977. Int. 

 Counc. Explor. Sea, Fish. Improv. Comm., Doc. CM1977/E:20, 16 

 P- 



sheepshead, and black drum (the drum is a marine 

 invader in brackish water). Secondary bacterial 

 infections associated with the ciliate m.ay become 

 systemic, and mortalities may result. 



In addition to field observations, there is some 

 experimental evidence for a causal relationship 

 between specific pollutant chemicals and fungus 

 parasitization offish and shellfish. In one study, 

 oysters exposed to pesticides (DDT, Toxaphene, 

 and parathion) became infected with a mycelial 

 fungus that caused lysis of the mantle, gut, 

 gonads, gills, visceral ganglion, and kidney 

 tubules (Lowe et al. 1971). None of the control 

 oysters became infected, indicating a role for one 

 or several of the pesticides in altering the host- 

 parasite relationships of the oysters and the fun- 

 gus. Presence of fungus infections made it difficult 

 to differentiate histopathological effects of pes- 

 ticide exposure from those due to the parasite. 



CONCLUSIONS 



In considering pollution-associated diseases of 

 fish and shellfish, a number of conclusions seem 

 warranted: 



1. Environmental stress from pollutants seems 

 to be an important determining factor in sev- 

 eral fish and shellfish diseases. Effects in- 

 clude direct chemical-physical damage to cell 

 membranes or tissues, modification of 

 physiological and biochemical reactions, in- 

 creased infection pressure from facultative 

 microbial pathogens, and reduced resistance 

 to infection. 



2. The multifactorial genesis of disease in 

 marine species is becoming apparent, involv- 

 ing environmental stress, facultative patho- 

 gens, resistance of hosts, and latent infec- 

 tions. 



3. Some circumstantial evidence for the role of 

 environmental carcinogens in the etiology of 

 neoplasms offish and shellfish is accumulat- 

 ing, but at present definitive conclusions are 

 not justified. 



4. The presence of marginal or degraded 

 estuarine/coastal environments may be sig- 

 nalled by the appearance of, or the increase 

 in prevalence of a number of diseases, includ- 

 ing fin erosion, "red sores," ulcers, and possi- 

 bly lymphocystis in fish; by "shell disease" in 

 crustaceans; and by certain neoplasms in 

 bivalve molluscs, but an absolute cause and 



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