Identifying novel Mycobacterium species in fish using multiple gene phylogenetic analysis

Mycobacteria have, for a long time, been suspected to be causing severe disease in ornamental and farmed fish in Trinidad and Tobago (T&T), however, up to now, these mycobacteria species have not been identified and characterised. Many piscine mycobacteria species are also known to be zoonotic, potentially affecting human health. Objective: To identify and characterize the species of mycobacteria affecting fish (and possibly man) in T&T. Design and Methodology: Homogenised internal organs were collected from a total of 13 fish showing clinical signs consistent with mycobacterial infection. Samples were analysed using Ziehl-Neelsen (acid-fast) staining and real-time Polymerase Chain Reaction (rPCR). The species of mycobacteria were further characterised using conventional PCR targeting the 16s rRNA (564 bp), rpoB (396 bp) and sod (408 bp) genes. PCR products were sequenced and the sequences were compared with those from known and recently identified mycobacteria species through phylogenetic analysis. Results: Acid-fast non-branching bacilli were detected in all samples. All samples were also positive for Mycobacterium sp. by real-time PCR. Multi-gene phylogenetic analysis revealed the presence of two distinct species of mycobacteria. One aligned closely with Mycobacterium marinum, a well known pathogen affecting fish and man, and a second aligned closely with a species also known to affect both fish and humans, Mycobacterium stomatepiae. Conclusions: Phylogenetic analysis demonstrated the presence of two mycobacterium species in organs from fish showing clinical signs of Piscine Mycobacteriosis in T&T. Further work is needed to characterise these mycobacteria species and investigate their zoonotic potential.

Identification of Myxozoa Parasite in the Connective Tissue of a Cascadura Fish (Hoplosternum Littorale) In Trinidad and Tobago

Background: Thirty cascadura (Hoplosternum littorale) fish from 5 different ponds were submitted alive to the Aquatic Animal Health Laboratory of the School of Veterinary Medicine, University of West Indies as part of monitoring and quarantine procedures of a commercial aquaculture farm. Cascadura fish are commercially important in Trinidad. Methodology: Water from the five different ponds was tested for quality. All fish were euthanized and necropsies were performed. Pooled samples from each pond were submitted for microbiology, parasitology, and histopathology. Results: All water samples had low alkalinity, low hardness, and low pH. In general, all ponds had evidence of low to moderate ecto- and endoparasitism. A section of connective tissue from the histopathologic samples of the pond with the lowest pH contained an area of hemorrhage and numerous poorly staining oval to tear-drop shaped organisms. These organisms stained brightly acid fast, and some included two polar capsules and a polar filament. No other signs of infection were noted in these fish. Conclusion: This is the first histopathologic description and report of myxozoan parasites in the cascadura in Trinidad. Myxozoa can be pathogenic, and should be included in the differential for causes of death in farmed cascadura, particularly when there is poor water quality which could affect the immune system of the fish.

Antibiotic-resistance patterns of bacterical pathogens isolated from ornamental fish in Trinidad and Tobago

Ornamental fish farming forms an important part of the local aquaculture industry in Trinidad and Tobago, and the number of farms has been increasing annually. This study was designed to ascertain the prevalence of bacterial pathogens from fish and pond water, and determine the resistance of the bacteria to commonly used antimicrobial agents. A total of 1204 bacterial isolates were recovered: from 575 fish slurry and 111 water samples from 17 aquaculture farms. Isolates from fish were identified as belonging to 19, and those from water samples were grouped in 18 genera. The predominant genera isolated were (in descending order) Aeromonas spp., Pseudomonas spp., Plesiomonas spp., Chromobacterium spp., Enterobacter spp. and Serratia spp. Screening against 8 antimicrobial agents showed that 95.1 percent (774 of 814) of isolates from fish slurry, and 98.4 percent (254 to 258) of isolates from pond water were resistant to one or more antimicrobial agents ( P> 0.05, X2). The highest resistance (55-94 percent) were to ampicillin, oxytetracycline and erythromycin, but relatively lower resistance (4-14 percent) occurred to gentamycin and norfloxacin (P< 0.05; X2). It was concluded that the high prevalence of bacterial pathogens in ornamental fish coupled with their high levels of resistance to antimicrobial agents may pose therapeutic problems as well as health risks to farmers, workers and fish hobbyists

Bacillus subtilis AB1 controls Aeromonas infection in rainbow trout (Oncorhynchus mykiss, Walbaum).

AIM: To develop a probiotic with effectiveness against Aeromonas sp., which was pathogenic to rainbow trout. METHODS AND RESULTS: When Bacillus subtilis AB1, which was obtained from fish intestine, was administered for 14 days to rainbow trout in feed at a concentration of 10(7) cells per gram either as viable, formalized or sonicated cells or as cell-free supernatant, the fish survived challenge with the pathogen. AB1 stimulated immune parameters, specifically stimulating respiratory burst, serum and gut lysozyme, peroxidase, phagocytic killing, total and alpha1-antiprotease and lymphocyte populations. CONCLUSIONS: Bacillus subtilis AB1 was effective as a probiotic at controlling infections by a fish-pathogenic Aeromonas sp. in rainbow trout. SIGNIFICANCE AND IMPACT OF THE STUDY: Disease control in fish is possible by means of the oral application of live and inactivated cells and their subcellular components with the mode of action reflecting stimulation of the innate immune response.

Nerocila benrosei n. sp. (Isopoda: Cymothoidae), an external parasite of hogfishes from the Northern Bahamas

Nerocila benrosei n. sp. is described from the hogfish, Lachnolaimus maximus (Walbaum), the Spanish hogfish, Bodianus rufus (Linnaeus), (Perciformes: Labridae) from the Northern Bahamas. Nerocila benrosei differs from all species of Nerocila by having the body of females 1.4 to 1.9 times as wide, as long, instead of 2.0 - 3.0 times) and pleopods 1 and 2 lacking accessory lamellae. It differs from the only species of Nerocila with which it overlaps geographically, N. lanceolata (Say, 1818), by having the lateral margins of pleonites 1-5 strongly produced ventrally, coxae 5-7 manifestly shorter than the posterolateral projection of the respective pereonite, and a vaulted dorsal surface. The species of Nerocila in the northwestern Atlantic have almost mutually exclusive geographic ranges: New England to Panama, including Bermuda and the northern coast of Cuba (Nerocila lanceolata); Brazil to Trinidad and Tobago (Nerocila fluviatilis Schiodte and Meinert, 1881); and the northern Bahamas and Bermuda (Nerocila benrosei). No species of Nerocila have been reported from the insular Caribbean. Nerocila benrosei appears to be highly host and site specific. (AU)

Ergasilid copepods (Poecilostomatoida) from the gills of primitive Mugilidae (grey mullets)

All representatives of the subfamily Agonostominae of grey mullets in the collections of The Natural History Museum in London were examined for parasitic copepods. Agonostomus monticola, Joturus pichardi, Aldrichetta forsteri and Cestraeus goldiei. Three new species of Acusicola and two new species of Ergasilus were found: E. parabahiensis n. sp. on A. monticola from Guyana and E. acusicestraeus n. sp. on C. goldiei from Papua New Guinea. Acusicola spinuloderma n. sp. was found on A. monticola and J. pichardi collected from different localities in Central America, A. mazatlanesis n. sp. on the same host from West Mexico (Mazatlan) and A. joturicola n. sp. on J. pichardi from Panama. Descriptions of E. australiensis Roubal, from Aldrichetta forsteri, are presented. The host-parasite relationships and geographical distributions of hosts and their parasitic copepods are analyzed. (AU)