The Fish Vet's Blog

Antibiotic resistance might be caused by aquaculture

November 22, 2011 Boston, MA –

Researchers from Tufts University School of Medicine agree on the controversial, non-therapeutic use of antibiotics in food animals and fish farming as a cause of antibiotic resistance. They report that the evidence shows a need for stricter regulation of the practice. “The US lags behind its European counterparts in establishing a ban on the use of antibiotics for growth promotion. For years it was believed that giving low-dose antibiotics via feed to promote growth in cows, swine, chickens and the use of antibiotics in fish farming had no negative consequences. Today, there is overwhelming evidence that non-therapeutic use of antibiotics contributes to antibiotic resistance, even if we do not understand all the mechanisms in the genetic transmission chain,” said Levy, MD, professor of molecular biology and microbiology and director of the Centre for Adaptation Genetics and Drug Resistance at Tufts. Antibiotics have been used for the last 70 years to fight bacterial infections such as streptococcus, meningitis, tuberculosis and urinary tract infections. The misuse and overuse of antibiotics have played a part in antibiotic resistance. Today, antibiotics are less effective when used to save lives. Levy and co-author Bonnie Marshall summarize their findings after reviewing numerous studies:• According to estimates, antibiotics are eight times more likely to be used for non-therapeutic purposes than for treating a sick animal.• Current practices set the stage for the rapid spread of antibiotic-resistant bacteria.• The long-term administration of antibiotics in animal feed creates an optimal environment for antibiotic resistance genes to multiply.• Treated animals become “factories” for the production and distribution of antibiotic-resistant bacteria such as Salmonella and Methicillin-resistant Staphylococcus aureus (MRSA).• Even if farmers turn to antibiotics that are not commonly used to treat people, these drugs – given over long periods of time – can also promote resistance.• Several studies demonstrated that antibiotic-resistant bacteria can easily spread from animals to people in close contact with animals, such as veterinarians, slaughterhouse workers, farmers, and the families of farmers.• As much as 90 per cent of antibiotics given to livestock are excreted into the environment. Resistance spreads directly by contact and indirectly through the food chain, water, air, and manured and sludge-fertilized soils.• The broad use of antibiotics in fish food in farm fishing, particularly overseas, leads to leaching where it can be washed to other sites, exposing wild fish to trace amounts of antibiotics.• The consequences of antibiotic resistance are great. According to the Centres for Disease Control and Prevention, antibiotic-resistant infections cause longer and more expensive hospital stays and greater risk of death.• Bans on the use of non-therapeutic antibiotics are effective in diminishing antibiotic resistance. Bans in European countries have seen less antibiotic resistance. It is common sense to avoid overcrowding food animals to improve hygiene and reduce the practice of routinely giving antibiotics to promote growth. “While the use of non-therapeutic antibiotics remains contentious, the evidence is strong enough to merit precaution. Antibiotics save lives. When infections become resistant to primary antibiotics, and alternative antibiotics must be used, health care costs increase. As more infections become more resistant to more antibiotics, we run the risk of losing more of our arsenal of antibiotics, resulting in needless deaths. It’s important to consider what we stand to gain versus what we stand to lose,” concludes Levy.

Source: http://tinyurl.com/7385dn5  [See http://tinyurl.com/7gn7xdu for Bonnie M. Marshall, BM & SB Levy (2011). Food Animals and Antimicrobials: Impacts on Human Health. Clin. Microbiol. Rev., 24:718-733.  ADS-Mod.]

From: “Dr. David Scarfe” <DScarfe>
Date: 16 December 2011 8:53:08 AWST
Subject: AquaVetMed: US Senate Hearing – Environmental Risks of Genetically Engineered Fish

Check out an article my colleague just published!

Journal of Fish Diseases
Volume 35, Number 1 (January 2012)
	The pathology of ‘scale drop syndrome’ in Asian seabass, Lates calcariferBloch, a first description
	Authors:	S Gibson-Kueh 1, D Chee 2, J Chen 2, Y H Wang 2, S Tay 2, L N Leong 3, M L Ng 4, J B Jones 5, P K Nicholls 1, H W Ferguson 6
	Author Affiliations:	1: School of Veterinary and Biomedical Sciences, Murdoch University, Western Australia, Australia  2: Animal & Plant Health Laboratories, AgriFood & Veterinary Authority of Singapore, Singapore  3: Electron Microscopy Unit, Faculty of Medicine, National University of Singapore, Singapore  4: Department of Microbiology, Faculty of Medicine, National University of Singapore, Singapore  5: Fish Health Laboratory, Department of Fisheries, Western Australia, Australia  6: Marine Medicine Program, School of Veterinary Medicine, St George’s University, Grenada, West Indies
	Source:	Journal of Fish Diseases, Volume 35, Number 1 (January 2012)
	Page Numbers:	19 – 27
	Available Full Text:	Full Text: Subscription Required to view full text Format: PDF Size: unknown Location: Publisher’s Site Authentication: EBSCOhost EJS
	Abstract:	This is the first pathological description of ‘scale drop syndrome’ (SDS) in Asian seabass, Lates calcariferBloch. Cumulative mortality was estimated at 40–50%. The vasculitis in all major organs including the skin and associated tissue necrosis was distinctive. The dermis overlying scale beds was often necrotic and associated with scale loss. Necrosis of splenic ellipsoids, renal glomeruli and choroid reteglands of eye were further hallmarks of a disease with systemic vascular involvement. The brain was not spared vascular damage, and the resulting multifocal encephalomalacia probably accounts for the spiral swimming behaviour in some affected fish. Other lesions included accentuated hepatic lobulation and gastric gland necrosis. Nuclear chromatin margination and karyolysis in hepatocytes, renal tubular epithelium and gastric and intestinal epithelium suggest specific targeting of cells. Basophilic cytoplasmic inclusions were present in spleen, kidney, liver, heart and choroid rete,but they were not prominent. Using transmission electron microscopy, two morphological forms of virions were observed: single- and double-enveloped hexagonal virions. Based on size and morphology, these virions resemble iridovirus or herpesvirus. The cause of SDS is unknown, but the pathological changes, especially the vasculitis, suggest an infectious aetiology, possibly viral.
	Citation:	S Gibson-Kueh, D Chee, J Chen, Y H Wang, S Tay, L N Leong, M L Ng, J B Jones, P K Nicholls, H W Ferguson . The pathology of ‘scale drop syndrome’ in Asian seabass, Lates calcariferBloch, a first description. Journal of Fish Diseases, Volume 35, Number 1 (January 2012), pp. 19-27, <http://ejournals.ebsco.com/direct.asp?ArticleID=4212A4D57163E64A7546&gt;
	URL:	http://ejournals.ebsco.com/direct.asp?ArticleID=4212A4D57163E64A7546

More and more work is being done in designing alternative feeds for aquacultured fishes. The reason for this may be one or both reasons:

1. Feeding fish to fish, to grow fish is not sustainable (the majority of aquacultured food fish are carnivorous – compare this with farmed terrestrial animals being herbivorous).
2. Fish/animal protein is more expensive than plant protein.

Trying to turn carnivorous fish into vegetarians is not a simple task because the diet may not meet all their nutritional requirements. This article details the findings of a diet trial in the sole fish.

—
Now on: Twitter – Blog – Facebook – Linkedin

Aquaculture
Volume 323, Number 1 (December 2011)
	Replacement of fishmeal by increasing levels of plant protein blends in diets for Senegalese sole (Solea senegalensis) juveniles
	Authors:	E.M. Cabral, M. Bacelar, S. Batista, M. Castro-Cunha, R.O.A. Ozório, L.M.P. Valente
	Author Affiliations:	no affiliations available
	Source:	Aquaculture, Volume 323, Number 1 (December 2011)
	Page Numbers:	74 – 81
	Available Full Text:	Full Text: Subscription Required to view full text Format: PDF Size: Unknown Location: Publisher’s Site Authentication: Publisher’s Site
	Abstract:	A growth trial was conducted to evaluate the growth potential and nutrient utilization of Senegalese sole fed diets containing increasing replacement levels of dietary fishmeal (FM) by mixtures of plant protein (PP) sources. Six extruded isonitrogenous and isolipidic diets (55% crude protein and 8% crude fat on a dry matter basis) were fed to juvenile sole (mean initial body weight: 8g±0.06) during 92days. A reference diet containing FM as the main protein source (Control) was compared with five PP based-diets with increasing PP levels: 25% (PP25), 35% (PP35), 45% (PP45), 60% (PP60) and 75% (PP75). PP45, PP60 and PP75 diets were supplemented with crystalline amino acids to simulate the level present in the Control diet. The environmental impact of the tested diets was assessed through the determination of N and P budgets and calculating approximate Fish-in:Fish-out (Fi:Fo) ratios. Fish fed PP25 and PP75 reached a final body weight and daily growth index (DGI) similar to the Control group (P0.05). Diet PP45 displayed the lowest DGI (0.8 vs 1.3%), lowest protein efficiency ratio (1.03 vs 1.8) and highest FCR (1.7 vs 1.01). The dietary treatments with highest percentage of FM replacement (PP60 and PP75) displayed similar FCR values as the Control (1.2–1.0). Apparent digestibility coefficients (ADCs) of protein varied between 77 and 85% and were not significantly affected by the PP inclusion level. Whole body protein and energy content did not differ significantly among treatments, but protein gain was significantly higher in the Control group compared to PP35, PP45 and PP60 groups. The results indicate that Senegalese sole can effectively cope with plant protein-based diets, but growth rate and nutrient gain mainly depend on the selection of adequate plant protein blends, rather than on the plant protein incorporation level. Sole fed the highest PP level (PP75) showed good growth performance, efficient dietary nutrient utilization and a lower Fi:Fo ratio compared to the Control. The present results clearly show that increasing FM replacement level can have a positive environmental impact as reduces P fecal waste and the fishmeal used per kg of sole produced.
	Citation:	E.M. Cabral, M. Bacelar, S. Batista, M. Castro-Cunha, R.O.A. Ozório, L.M.P. Valente . Replacement of fishmeal by increasing levels of plant protein blends in diets for Senegalese sole (Solea senegalensis) juveniles. Aquaculture, Volume 323, Number 1 (December 2011), pp. 74-81, <http://ejournals.ebsco.com/direct.asp?ArticleID=456681144978879A27C9&gt;
	URL:	http://ejournals.ebsco.com/direct.asp?ArticleID=456681144978879A27C9

Have you ever wondered what all that “slime” on the side of you tanks and ponds are? Scientists call this the “biofilm”. In healthy systems, the biofilm is integral to maintaining good water quality and fish health. You can think of it as “yoghurt” for the pond/tank. The article below talks a bit about this and how it helps with crayfish health.

Aquaculture   Volume 325, Number 9 (January 2012)      Contribution of biofilm to water quality, survival and growth of juveniles of the freshwater crayfish Cherax quadricarinatus(Decapoda, Parastacidae)        Authors: Verónica E. Viau, Juan M. Ostera, Analía Tolivia, Eduardo L.C. Ballester, Paulo C. Abreu, Enrique M. Rodríguez     Author Affiliations:

Source: Aquaculture, Volume 325, Number 9 (January 2012)     Page Numbers: 70 – 78      Available Full Text:

Abstract: The effect of biofilm as an alternative food source and/or a complement for improving culture was assayed for early and advanced juveniles of Cherax quadricarinatus.For both kinds of juveniles, higher values of survival were seen in the experimental groups provided with either biofilm (B) or a combination of both formulated food and biofilm (B+F), compared to the group only receiving formulated food (F). Such higher survival was associated to a better water quality maintained by biofilm, in terms of low levels of both ammonium and nitrite, together with high levels of pH and dissolved oxygen. As for growing, specific growth rate was higher in the groups fed with formulated food, but only for early juveniles. Considering the crayfish biomass at the end of the experiment (i.e., an integrative index of both survival and growth), the best results were seen in the B+F group, for both kind of juveniles. The main micro-organisms present in biofilm were chlorophytas, xantophytas, pennate diatoms, cyanobacteria, flagellates, ciliates, rotifers and nematodes. Most of these items were found in the stomach of crayfishes fed on biofilm. The hepatopancreatic levels of total lipids were higher in animals of both B+F and F groups, compared to those of B group, while energetic reserves in the abdominal muscle showed no differences among experimental groups, for any kind of juveniles. Therefore, biofilm could be considered as a good complement for the culture system of C. quadricarinatusjuveniles, mainly by improving survival through the maintenance of a good water quality. Combination of biofilm and formulated food has shown the best results, in terms of both survival and growth of juvenile crayfish.      Citation: Verónica E. Viau, Juan M. Ostera, Analía Tolivia, Eduardo L.C. Ballester, Paulo C. Abreu, Enrique M. Rodríguez . Contribution of biofilm to water quality, survival and growth of juveniles of the freshwater crayfish Cherax quadricarinatus(Decapoda, Parastacidae). Aquaculture, Volume 325, Number 9 (January 2012), pp. 70-78, <http://ejournals.ebsco.com/direct.asp?ArticleID=407EAE81898163FD4E34&gt;      URL: http://ejournals.ebsco.com/direct.asp?ArticleID=407EAE81898163FD4E34