monensin and Fish-Diseases

Previous work in our group has identified the scavenger endothelial cells (SECs) of heart endocardium in cod, Gadus morhua L., as the major site for elimination of both physiological and foreign macromolecular waste from the circulation. The present study was undertaken to establish the role of cod SECs in the clearance of virus. We focused on infectious pancreatic necrosis virus (IPNV) as it is a well-known virus with a broad host range, and causes significant economic losses in the salmon industry. Our results showed that cod SEC cultures infected by the IPNV produce high titres of new virus. Ligand-receptor inhibition experiments suggested that the virus did not enter the cells through any of the major endocytosis receptors of cod SECs. Yet, the infection lowered the capacity of the cells to endocytose ligands via the scavenger receptor. Inhibitors of receptor recycling and vesicle acidification did not affect virus infectivity. The finding that SEC cultures prepared from 25% of the cod produced high titres of IPNV without being infected in the laboratory, suggests that SECs of cod may serve as reservoirs for IPNV in persistently infected cod.

Topics: Animals; Antiprotozoal Agents; Birnaviridae Infections; Chloroquine; Endocytosis; Endothelial Cells; Fish Diseases; Gadus morhua; Infectious pancreatic necrosis virus; Iodine Radioisotopes; Ligands; Monensin; Receptors, Virus; Time Factors; Virus Replication

The chemotherapeutic efficacy of 6 in-feed compounds against Ichthyophthirius multifiliis Fouquet, 1876 was assessed using experimental infections of rainbow trout Oncorhynchus mykiss (Walbaum) fingerlings. Trial doses of 104 ppm amprolium hydrochloride or 65 ppm clopidol fed to fish for 10 d prior to infection significantly reduced the number of trophonts establishing in trout fingerlings by 62.0 and 35.2% respectively. In-feed treatments of infected trout with either 63 or 75 ppm amprolium hydrochloride, 92 ppm clopidol, or 38, 43 or 47 ppm salinomycin sodium for 10 d also significantly reduced the number of surviving trophonts by 77.6 and 32.2% for amprolium, 20.1% for clopidol and 80.2, 71.9 and 93.3% respectively for salinomycin sodium.

Topics: Administration, Oral; Amprolium; Animal Feed; Animals; Antiprotozoal Agents; Ciliophora; Ciliophora Infections; Clopidol; Decoquinate; Dose-Response Relationship, Drug; Fish Diseases; Monensin; Nicarbazin; Oncorhynchus mykiss; Pyrans; Random Allocation; Treatment Outcome

Streptococcosis is a major disease of several fish species in Australia, Japan and South Africa. The minimum inhibitory concentration of some ionophores (lasalocid, monensin, narasin and salinomycin) was determined in vitro for an Enterococcus-like species pathogenic for rainbow trout (Oncorhynchus mykiss) in Australia. Forty isolates of the fish pathogen were tested, together with control strains of Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212 and Streptococcus bovis ATCC 9809. The minimum inhibitory concentrations (MIC) of erythromycin, the drug of choice for controlling streptococcosis, ranged between 0.1 and 0.8 microgram/ml whereas the MIC values for the ionophores ranged between 0.2 and 1.5 micrograms/ml. Of the ionophores tested, narasin was the most inhibitory (0.2-0.4 microgram/ml), while monensin was the least inhibitory (0.4-1.5 micrograms/ml). Salinomycin was marginally more inhibitory (0.4-0.8 microgram/ml) than lasalocid (0.8 microgram/ml).

Topics: Animals; Anti-Bacterial Agents; Enterococcus; Erythromycin; Fish Diseases; Gram-Positive Bacterial Infections; Ionophores; Lasalocid; Microbial Sensitivity Tests; Monensin; Oncorhynchus mykiss; Pyrans

Epizootics of Eimeria funduli involved estuarine killifishes (Fundulus grandis, F. pulvereus, F. similis, and F. heteroclitus) in Mississippi, Alabama, and Virginia. All of more than 500 specimens examined of F. grandis from Mississippi during 1977 though 1979 had infections, regardless of age, sex, or season collected. Oocysts occurred primarily in the liver and pancreas, replacing up to 85% of both those organs. Infrequent sites of infection were fatty tissue of the body cavity, ovary, intestine, and caudal peduncle. Living fish did not discharge oocysts. Eimeria funduli is the first known eimerian to require a second host. To complete the life cycle, an infective stage in the grass shrimp Palaemonetes pugio had to be eaten. In 6-mo-old killifish reared in the laboratory at 24 C, young schizonts were first observed in hepatic and pancreatic cells 5 days postfeeding, followed by first generation merzoites by day 10, differentiation of sexual stages during days 15 to 20, fertilization between days 19 and 26, sporoblasts from days 25 to 30, and sporozoites about day 60. Unique sporopodia developed on sporocysts by day 35 when still unsporulated. Temperatures of 7 to 10 C irreversibly halted schizogony. Both schizogony and sporogony progressed slower as age of host increased. When infective shrimp in doses ranging from 1 to 10% of a fish's body weight were eaten, the level of intensity of resulting infections did not differ significantly. Pathogenesis followed a specific sequence, with the host response apparently unable to contend with extensive infections as seen typically in nature and in our experiments. Premunition was indicated. When administered Monensin orally, infected fish exhibited a reduction in oocysts by 50 to 70% within 20 days as compared with untreated fish. Furthermore, infected killifish exclusively on a diet of TetraMin for 3 mo completely lost their infections.

Topics: Animals; Coccidiosis; Eimeria; Fish Diseases; Fishes; Killifishes; Liver; Monensin