Pleistophora infestation in fathead minnows, Pimephales promelas (Rafinesque)

Pleistophora infestation was observed in adult fathead minnows, Pimephales promelas, held under laboratory conditions. Fish were clinically healthy, and presented no gross findings at necropsy. Histopathology revealed parasitic stages only in the ovaries. Spores within sporophorous vesicles were mainly encountered in late vitellogenic oocytes and were ultrastructurally identified as a microsporidian parasite. Heavily parasitized oocytes underwent degeneration followed by the release of spores into the ovarian interstitium. Degenerating oocytes and interstitial spores caused ovarian inflammation. Male fish showed no parasites in the testes. Parasitic infestation was compared with body length, body weight, gonadal weight, gonadosomatic index and plasma vitellogenin levels, and revealed no statistically significant differences between non-parasitized and parasitized females. The isolated holding conditions of the fish and the presence of parasitic stages in the ovaries suggested that an infestation with Pleistophora ovariaeSummerfelt, 1964 was more probable than that with Pleistophora mirandellae (Vaney & Conte, 1901).     

Pharmacological treatments against Ichthyobodo necator (Henneguy, 1883) in rainbow trout, Oncorhynchus mykiss (Walbaum)

Abstract. Various antiparasitic drugs belonging to several pharmacological groups were tested by bath administration for in vivo activity against a natural infestation of rainbow trout. Oncorhynchus mykiss (Walbaum), by he flagellate protozoan Ichthyobodo necator. Fish were also monitored for signs of drug toxicity. Complete elimination of infestation in all fish was achieved only by bithionol (25 mgl^-1 for 3h on two consecutive days). Ketoconazole, toltrazuril, amprolium, sulphaquinoxaline, quinacrine, N-metylglucamine, chloroquine, 1,3-di-6-quinolylurea, diminazene aceturate and paromomycin were not effective. Diminazene aceturate (100 mgl^-1, 3h) was the only drug which was clearly toxic. The comparison of the response of symptomatic and asymptomatic infested fish to a formaldehyde bath indicates that poor health caused by I. necator may greatly increase the susceptibility of fish to the toxic effects of a drug or chemical.     

Leech (Myzobdella lugubris) infestations in largemouth bass (Micropterus salmoides) in Back Bay,Virginia, USA

Back Bay is an oligohaline, coastal bay in southeast Virginia, USA. Since 2004, leeches have been observed in the oral cavities of largemouth bass (Micropterus salmoides) in this body of water. Leeches (Myzobdella lugubris) have previously been documented in the oral cavities of largemouth bass in the Currituck Sound, which is confluent with Back Bay on its southern border. Supplemental stocking of largemouth bass in Back Bay since 2009 has resulted in an increasing population; however, concern exists that leech infestation may be negatively affecting health of larger fish, which are still less abundant than expected. Despite the wide distribution of this leech, there is little available literature regarding its health impacts on hosts. In this study, we examine potential impacts of oral leech infestations on stress markers and haematological parameters of largemouth bass in Back Bay. No significant changes in plasma glucose or cortisol were observed between leech‐infested and uninfested fish, and haematological parameters were not significantly different between the groups. Further, there was no evidence of systemic infections associated with leech infestation.     

Susceptibility,behaviour, and retention of the parasitic salmon louse (Lepeophtheirus salmonis) differ with Atlantic salmon population origin

Atlantic salmon populations across the world have diverse ecological and evolutionary histories, from wild anadromous or landlocked, to domestication and genetic modification. The natural host behaviours confer protection from infestation by ectoparasitic salmon lice Lepeophtheirus salmonis, yet whether genetic origin results in different behaviours and thus susceptibility to infestation is unknown. In common garden experiments, we tested antiparasite behaviours, susceptibility and retention of salmon lice in wild anadromous, wild landlocked, domesticated and genetically modified domesticated strains. Within domesticated strains, we tested two infestation histories (previously infested and naïve) and a new phenotype (albino colouring). Farmed stocks initially acquired 24%–44% higher levels of parasite density than the wild and landlocked strains. Burst swimming and displacement behaviours were higher in the domesticated groups, and jumping was more prevalent in the domesticated strains. At 34 days post‐infestation, domesticated strains and the wild anadromous strain did not differ significantly from each other; however, landlocked salmon had increased infestation levels considerably. Domesticated strains lost ~20% (±9.9%–16.5%; 95% CI) of their initial parasite load, while parasite load increased by 5.5% (±30.1%) for wild salmon and 20.1% (±28.5%) in landlocked salmon. This study provides early evidence for diverged host–parasite interactions associated with domestication in this system.     

The impact of invasive fish on an endemic Cyprinodon species flock (Teleostei) from Laguna Chichancanab, Yucatan, Mexico

Abstract –  Species that invade a new environment often may lead to population declines of endemic species. Here I document the invasions of an African cichlid (genus Oreochromis) in 1988 and the Mexican Astyanax fasciatus (Characidae) in 1996 into Laguna Chichancanab (Yucatan, Mexico), and the impact on an endemic Cyprinodon species flock and the poeciliid Gambusia sexradiata . After the invasion of Astyanax fasciatus , their relative abundances decreased enormously, most likely caused by predation on the fry. One species, Cyprinodon simus , might have even gone extinct or just occurs in extremely reduced numbers. Furthermore, it was observed that the percentage abundance of the detritivorous Cyprinodon beltrani increased significantly, in contrast to all other Cyprinodon species. This study also revealed that infestation by metacercaria (black spots) of an ectoparasitic trematode and of an endoparasitic nematode increased in the Cyprinodon spp. following the introduction of Oreochromis . Whereas the infestation by trematodes decreased after a period of 6 years, the prevalence and intensity of infestation by nematodes stayed at a high level. In contrast, in G. sexradiata the parasite load remained always very low.     

Effect of infestation with the isopod, Alitropus typus M. Edwards (Crustacea: Flabellifera: Aegidae) on the haematological parameters of the host fish, Channa striatus (Bloch)

Detailed accounts supported by experimental data are furnished regarding the haematological parameters of the host fish, Channa striatus infested by the isopod, Alitropus typus. Results demonstrate that the infested fish become anaemic through loss of blood as shown by a reduction in the total erythrocyte count, haemoglobin content and haematocrit. Considering the mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration and volume index, the anaemia can be designated as macrocytic and hypochromic. The total and differential counts of white blood corpuscles of the infested fish indicate leucopenia coupled with lymphocytosis. The percentages of monocytes, neutrophils and macrophages, which were 0.65%, 0.39% and 1.04%, respectively, after 24 h of infestation, had increased to 2.31%, 4.91% and 2.02%, respectively, after 96 h of infestation and declined thereafter.     

An unexpected host for the endangered giant freshwater pearl mussel Margaritifera auricularia (Spengler, 1793) as a conservation tool

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Amyloodinium ocellatum (Brown, 1931) (Dinoflagellida) infestations in cultured marine fish at Eilat, Red Sea: epizootiology and pathology

Abstract. Since 1977, repeated outbreaks of infestation by Amyloodinium ocellatum (Dinoflagellida) in cultured gilthead bream Sparus aurata L. and seabass Dicen-trarchus labrax (L.) resulted in sporadic and mass mortalities. Fingerlings and yearlings as well as breeders were affected and, since 1978, larval and post-larval S. aurata in the hatchery. Infestations in juvenile and breeder fish were located predominantly on the gills and mucosal integument but in larval fish only the skin rather than the gills was infested. Histopathological changes of the infested gills are described. Vacuolar degeneration of the cells penetrated by the parasites' rhizoids was evident at the site of attachment and cloudy swelling was apparent in the surrounding epithelial cells. In heavy infestations the entire epithelium of the gill filaments underwent hyperplasia with consequent fusion of the lamellae. Where hyperplasia was extensive the cells gradually degenerated while the inner epithelial layer showed distinct spongiosis and in some cases completely disintegrated. All heavily infested gills lacked mucous cells.     

Stress response of Salmo salar (Linnaeus 1758) facing low abundance infestation of Caligus rogercresseyi (Boxshall & Bravo 2000), an object in the tank,and handling

This study looks at how low infestation loads of adult Caligus rogercresseyi and other stressors affect the physiology of Salmo salar. Experimental fish groups were with (infested) or without (control) exposure to the parasite. The parasite cohort was followed for 78 days post‐infestation (dpi), and only adult lice were observed. Additional stressors were applied at 60 and 75 dpi. The analysis included measurements of fish physiology and weight. Low‐level infestations by adult C. rogercresseyi for more than 50 dpi induced moderate stress in S. salar as well as a high energy demand and increased small skin mucous cells. Threshold lice loads were identified, and above those loads, a high stress response was observed. Additional stressors altered fish physiology, inducing downregulation of the cortisol response after the first stressor and upregulation after the second stressor, but infested fish responded more strongly. Parasitism by C. rogercresseyi is energetically demanding, affecting the primary and secondary responses (e.g. cortisol and glucose levels), as well as the tertiary response (fish weight).     

Trombiculid mite--Neotrombicula autumnalis (Shaw 1790)--in veterinary medicine. Nervous systems in dogs following massive infestation

Initially the biology of chigger mites and the clinical course of Trombiculosis is reviewed. This is followed by a case study dealing for the first time with nervous symptoms associated with this disease. Twenty-four hours after a massive infestation of at least 2000 larvae of N. a. autumnalis two male Yorkshire terriers of approximately three years of age showed initial stages of paresis of the rear extremities in a few hours. The lameness worsened to such an extent that the front extremities were also affected and the dogs could no longer stand. After repeated acaricide treatments and symptomatic therapy these nervous symptoms disappeared within three days.     

Efficacy of manual removal and ivermectin gavage for control of Salmincola californiensis (Wilson) infestation of chinook salmon, Oncorhynchus tshawytscha (Walbaum), captive broodstocks

Captive broodstocks of spring chinook salmon, Oncorhynchus tshawytscha , were initiated from collections of naturally produced parr from the Lemhi River, a tributary of the Salmon River, ID, USA. These fish were subsequently demonstrated to be infested with the copepod parasite Salmincola californiensis . The initial prevalence of visible adult parasites for 4 years of observations made shortly after collection varied from 19.7 to 71.6%. Both the prevalence and intensity of the infestation increased in the freshwater culture of these fish. Manual removal was initiated as a means of control and practiced at monthly intervals. The number of Salmincola removed decreased in the ensuing 5 months, but the prevalence was not greatly affected. Ivermectin (22,23 dihydroavermectin), was diluted with saline and delivered by gavage at the rate of 0.20 mg kg⁻¹ body weight when the groups were being handled for the manual removal of parasites. Either two or three ivermectin treatments were given to four broodstocks of chinook salmon depending on the severity of the infestation and on the extent of gill pathology. The combination of manual removal and ivermectin gavage eliminated live Salmincola and resolved all associated necrosis of the gill tissues. There was no trend to indicate that individual chinook salmon possessed a natural resistance to reinfestation.     

Effect of Trachelobdella lubrica (Hirudinea: Piscicolidae) on biochemical and haematological characteristics of black scorpion fish (Scorpaena porcus, Linnaeus 1758)

Black Scorpion fish (Scorpaena porcus Linnaeus 1758) caught during monthly sampling carried out in 2003 in the Dardanelles, Turkey, were examined for the parasite. Trachelobdella lubrica. Infested fish were caught only during December 2003, and the clinical conditions of the 12 fish naturally infested with T. lubrica included fin rot, swollen foci of skin and haemorrhages of the gill and abdominal skin. The prevalence, intensity and abundance of infestation in December 2003 were 40%, 1.75 and 0.70, respectively. The average hepatosomatic index of the infested fish was lower than that of noninfested fish, while the means of the kidney index, splenosomatic index, condition factor, body weight and length were not significantly different between the infested and noninfested fish groups. Blood analysis was conducted on 12 naturally infested and 12 healthy (noninfested) Black Scorpion fish to determine the possible characteristic changes in blood parameters of the fish in response to natural infestation with T. lubrica. Blood leucocyte counts, haematocrit levels, serum total protein, albumin phosphorus, urea, glucose, globulin, cholesterol and triglyceride concentrations in naturally infested Black Scorpion fish were significantly less than those of the noninfested fish (p < 0.05). No significant decreases were observed in the serum sodium, iron, calcium, potassium, chlorine, blood urea nitrogen and creatinine values of the naturally infested fish. Blood haemoglobin values, erythrocyte counts and serum glutamate aspartate aminotransferase (glutamate oxalacetate transaminase), alanine aminotransferase (glutamate pyruvate transaminase), uric acid and very low-density lipids levels of infested fish were insignificantly greater than those in healthy fish.     

The effect of artificial light treatment and depth on the infestation of the sea louse Lepeophtheirus salmonis on Atlantic salmon (Salmo salar L.) culture

Two field studies were carried out with farmed Atlantic salmon (Salmo salarL.) in sea cages to examine various effects of artificial light (AL) and the vertical distribution of salmon on lice infestation.

The use of AL light caused an overall increase in lice infestation in both experiments. The first study showed that salmon held at 0–4 m depth in cages developed higher infestation than salmon held at greater depths (4–8 and 8–12 m) under both natural light (NL) and AL. In the second study, salmon maintained in 14-m deep sea cages that were exposed to AL with different light intensities. The AL treatments resulted directly in different diel and seasonal patterns of vertical distribution of the salmon and also different temporal patterns in lice infestations. So indirectly the infestation pattern appeared to be correlated with median day-time swimming depth of the salmon.     

Physiological responses of reared sea bream (Sparus aurata Linnaeus, 1758) to an Amyloodinium ocellatum outbreak

Amyloodiniosis represents a major bottleneck for semi‐intensive aquaculture production in Southern Europe, causing extremely high mortalities. Amyloodinium ocellatum is a parasitic dinoflagellate that can infest almost all fish, crustacean and bivalves that live within its ecological range. Fish mortalities are usually attributed to anoxia, associated with serious gill hyperplasia, inflammation, haemorrhage and necrosis in heavy infestations; or with osmoregulatory impairment and secondary microbial infections due to severe epithelial damage in mild infestation. However, physiological information about the host responses to A. ocellatum infestation is scarce. In this work, we analysed the proteome of gilthead sea bream (Sparus aurata) plasma and relate it with haematological and immunological indicators, in order to enlighten the different physiological responses when exposed to an A. ocellatum outbreak. Using 2D‐DIGE, immunological and haematological analysis and in response to the A. ocellatum contamination we have identified several proteins associated with acute‐phase response, inflammation, lipid transport, homoeostasis, and osmoregulation, wound healing, neoplasia and iron transport. Overall, this preliminary study revealed that amyloodiniosis affects some fish functional pathways as revealed by the changes in the plasma proteome of S. aurata, and that the innate immunological system is not activated in the presence of the parasite.     

Does the AquasmartTM feeding system reduce sea louse [Lepeophtheirus salmonis (Krøyer)] infestation on farmed Atlantic salmon (Salmo salar L.) in winter?

Infections of sea lice [Lepeophtheirus salmonis (Krøyer)] were studied over winter on a working, commercial salmon farm in relation to two types of feeding system: a regular, pneumatic spray feeder and an irregular, ‘demand feed’ sensor system (Aquasmart^TM). Contrary to prediction, the Aquasmart^TM system alone had no significant effect on chalimus infestation compared with fish fed by pneumatic spray. However, it was associated with significantly reduced numbers of mobile stages, both at the beginning of the study (P < 0.05) and, more particularly, in conjunction with treatment of all pens using hydrogen peroxide (P < 0.001). It is suggested that feeding regime may represent a useful tool in reducing lice infestation when co‐ordinated with other methods of control, such as peroxide treatment, and that further work in this field is merited.     

Use of Onion (Allium cepa) and Garlic (Allium sativum) Wastes for the Prevention of Fungal Disease (Saprolegnia parasitica) on Eggs of Rainbow Trout (Oncorhynchus mykiss)

This study was designed to prevent fungal disease (Saprolegnia parasitica) that occurs on rainbow trout eggs (Oncorhynchus mykiss) by using wastes of onion (Allium cepa) and garlic (Allium sativum) plants. For this purpose, fertilized rainbow trout eggs were exposed to garlic skin, garlic stem and onion skin aqueous methanolic extracts by bathing in concentrations of 0.4, 0.8, 1.6 and 3.2 g/L, whereas the control group was left untreated. The larvae in all groups were monitored until they become free-swimming larvae, the number of eggs died due to fungus was recorded, and the data obtained from experimental groups and control group were compared. As a result, it was determined that onion skin had no effect on the number of eggs that died due to fungus (p > .05), while garlic skin and garlic stem extracts significantly reduced the number of fungal infestations without affecting the number of live larvae or the embryological development of the eggs (p < .05). In light of these data, we conclude that garlic skin (0.4, 0.8, and 1.6 g/L) and garlic stem (0.8 and 1.6 g/L) aqueous methanolic extracts are effective at preventing Saprolegnia parasitica infestation on rainbow trout eggs and may be used in aquaculture.     

Use of neem oil (Azadirachta indica) to control caligid copepod infestation on Asian seabass (Lates calcarifer)

Asian seabass (Lates calcarifer) culture in marine cages have been developed rapidly in Malaysia. The high intensity of culture might facilitate several disease infection including caligid infestation. This study was conducted to evaluate the effect of neem oil (Azadirachta indica) against caligid parasites on seabass. The prevalence and clinical pathogen of Caligus infection has been described through a sampling of 150 fish from floating cage at different cultured periods. Acute toxic tests with different concentrations of neem oil were carried out on the parasite and fish host. Results revealed that the 96‐hr median lethal concentration (LC₅₀) of Caligus and fish (10.3 ± 2.5 g of body weight) were 2 and 20 ppm respectively. The in vivo test indicated that 10 ppm of neem oil could result in 100% antiparasitic efficacy within 96 hr. These results therapeutically demonstrated the efficacy of neem oil in caligid control.     

Time-series models of sea lice Caligus elongatus (Nordmann) abundance on Atlantic salmon Salmo salar L. in Loch Sunart, Scotland

Most lice infestations on salmon farmed in the North Atlantic are attributed to Caligus elongatus and Lepeophtheirus salmonis. This study reports findings from time‐series analysis conducted on observations of the lesser‐studied C. elongatus, in four farms on the west coast of Scotland over the period 1996–2000. Least‐squares and Poisson regression techniques were applied to one individual site and to the aggregated data of four sites. Models were fitted and tested for goodness of fit using appropriate statistical methods. Findings indicate that infestation levels are highly seasonal with rapidly increasing numbers after week 22 of the year followed by a steady decline from week 40. Abundance is much lower in the second year of the production cycle than the first. Neither of the models indicated that treatment application has a significant effect on C. elongatus infestations.     

Infestation parameters for Lepeophtheirus salmonis (Kroyer) (Copepoda: Caligidae) parasitic on sea trout, Salmo trutta L., off the west coast of Ireland during 1990 and 1991

Abstract. Infestation parameters for the calígíd copepod Lepeophtheirus salmonis (Kroyer) infesting sea trout, Salmo trutta L., were established for a number of locations off the west coast of Ireland during 1990 and 1991. Based on these parameters sites were classified into two groups in 1990 and three in 1991. Median parasitic intensity in these groups was 11·6 and 77 in 1990 and 9·5, 29·5 and 55 in 1991. Fish were parasitized mainly by chalimus stages of the parasite which attached preferentially to the fins. Heaviest infestations were invariably due to chalimus stages and early pre-adult lice and there was a progressive decrease in the correlation between parasitic intensity and the number of each successive stage in the life cycle. This suggested either host or parasite mortality as the parasite matured. Large numbers of lice-infested fish returned prematurely from the sea to estuarine areas at a number of sites. Extensive morphological damage, especially to the fins, was apparent on a proportion of these fish as a result of the infestation. Mortality of heavily infested fish was directly observed.