The future of therapeutic agents in aquaculture.

The implementation and monitoring of fish health regulations vary extensively in aquaculture throughout the world. In the main salmon-producing countries, there is strict regulatory oversight of the use of pharmaceutical drugs. Such controls have supported the sustainable growth of the aquaculture industry and, in Norway, aquaculture has been able to reduce its total consumption of antibiotics by more than 99% between 1995 and today, yet there has been a 20-fold rise in production volume. Other countries on other continents may have less control, with no mandatory prescription regulations and variable quality of the pharmaceutical products available. A good regulatory framework, with control and monitoring systems, should be established in all countries where aquaculture is practised and veterinary medicinal products should only be available under veterinary prescription and supervision. Many drug resistance genes have been identified, and molecular methods should be applied to control drug resistance in the microbial and parasitic populations of all major aquaculture-producing regions.

Les niveaux de mise en place et de suivi des réglementations applicables à la santé des poissons en aquaculture sont extrêmement variables d'une région à l'autre. Les pays où la salmoniculture prédomine pratiquent un contrôle réglementaire strict de l'utilisation de produits médicamenteux. Ces contrôles ont permis une croissance durable du secteur ; ainsi, en Norvège l'aquaculture a pu réduire sa consommation totale d'antibiotiques de plus de 99 % depuis 1995 tout en multipliant par vingt le volume de production. Le niveau des contrôles est parfois moindre dans d'autres pays d'autres continents, où aucune réglementation n'impose l'obligation d'une prescription vétérinaire et où les produits pharmaceutiques disponibles sont de qualité variable. Tous les pays ayant une production aquacole devraient mettre en place un cadre réglementaire solide doté de systèmes de contrôle et de suivi ; par ailleurs, les produits pharmaceutiques vétérinaires ne devraient pouvoir être obtenus que sous prescription et supervision vétérinaires. Plusieurs gènes responsables de résistances aux agents médicamenteux ont été identifiés ; il conviendrait que toutes les régions dédiées à l'aquaculture recourent à des méthodes moléculaires pour contrôler le phénomène de la résistance aux agents médicamenteux dans les populations de microbes et de parasites.

La aplicación de reglamentos de salud piscícola y las actividades de control reglamentario en la acuicultura varían sobremanera según el lugar del mundo de que se trate. En los principales países productores de salmón, el uso de productos farmacéuticos está sujeto a una estricta supervisión reglamentaria. Estos controles han favorecido el crecimiento sostenible del sector de la acuicultura, sector que en Noruega ha logrado reducir su consumo total de antibióticos en más de un 99% entre 1995 y la actualidad, pese a haber multiplicado por veinte su producción. En otros países de otros continentes hay a veces un menor control, debido a la ausencia de reglamentos de carácter prescriptivo y a la irregular calidad de los productos farmacéuticos disponibles. Sería menester que todos los países donde se practica la acuicultura contaran con un buen ordenamiento reglamentario, dotado de sistemas de control y seguimiento, y que en ellos solo se pudieran obtener productos de uso veterinario con receta y bajo supervisión veterinarias. Sabiendo que se han encontrado muchos genes que determinan resistencia a los medicamentos, convendría aplicar métodos moleculares para controlar la aparición de farmacorresistencias en las poblaciones microbianas y parasitarias de todas las regiones que albergan un importante sector acuícola.

How can we objectively categorise partnership type? A novel classification of population survey data to inform epidemiological research and clinical practice.

BACKGROUND: Partnership type is a determinant of STI risk; yet, it is poorly and inconsistently recorded in clinical practice and research. We identify a novel, empirical-based categorisation of partnership type, and examine whether reporting STI diagnoses varies by the resulting typologies. METHODS: Analyses of probability survey data collected from 15 162 people aged 16-74 who participated in Britain's third National Survey of Sexual Attitudes and Lifestyles were undertaken during 2010-2012. Computer-assisted self-interviews asked about participants' ≤3 most recent partners (N=14 322 partners/past year). Analysis of variance and regression tested for differences in partnership duration and perceived likelihood of sex again across 21 'partnership progression types' (PPTs) derived from relationship status at first and most recent sex. Multivariable regression examined the association between reporting STI diagnoses and partnership type(s) net of age and reported partner numbers (all past year). RESULTS: The 21 PPTs were grouped into four summary types: 'cohabiting', 'now steady', 'casual' and 'ex-steady' according to the average duration and likelihood of sex again. 11 combinations of these summary types accounted for 94.5% of all men; 13 combinations accounted for 96.9% of all women. Reporting STI diagnoses varied by partnership-type combination, including after adjusting for age and partner numbers, for example, adjusted OR: 6.03 (95% CI 2.01 to 18.1) for men with two 'casual' and one 'now steady' partners versus men with one 'cohabiting' partner. CONCLUSIONS: This typology provides an objective method for measuring partnership type and demonstrates its importance in understanding STI risk, net of partner numbers. Epidemiological research and clinical practice should use these methods and results to maximise individual and public health benefit.

Experimental challenge studies in Vietnamese catfish, Pangasianodon hypophthalmus (Sauvage), exposed to Edwardsiella ictaluri and Aeromonas hydrophila.

The two main diseases in the pangasius catfish industry are bacillary necrosis of Pangasianodon (BNP) and motile aeromonas septicaemia (MAS), where the aetiological agents have been identified as Edwardsiella ictaluri and Aeromonas hydrophila, respectively. In this study, apparently healthy Pangasianodon hypophthalmus were exposed to E. ictaluri, A. hydrophila or both bacterial species by intraperitoneal injection or immersion. There were 20 fish per treatment group, and the bacterial isolates used for the study were recovered from natural infections of BNP or MAS in farmed Vietnamese P. hypophthalmus. The results of the experimental infections mimicked the natural disease outbreaks reported from these pathogens in P. hypophthalmus. Furthermore, it was clearly demonstrated that E. ictaluri was only recovered from the fish exposed to the bacterium and not recovered from the animals receiving A. hydrophila.

The efficacy and safety of an oil-based vaccine against Photobacterium damsela subsp. piscicida in yellowtail (Seriola quinqueradiata): a field study.

Protection after intraperitoneal (i.p.) vaccination of yellowtail (Seriola quinqueradiata) against pasteurellosis was studied in a field trial. Yellowtail juveniles captured from the wild or artificially hatched were immunised with an oil-based vaccine against Photobacterium damsela subsp. piscicida, and the fish were observed for 15 weeks after vaccination. Outbreak of pasteurellosis was observed at all five sites (mortality in control group ranged from 7% to 77%), and significant (p<0.01) protection against pasteurellosis relative to non-vaccinated control groups was observed at all sites. The vaccinated fish showed an increased level of agglutinating antibodies against Ph. damsela subsp. piscicida with a peak around 3-4 weeks post vaccination, increased phagocytic activity and increased production of superoxide anions in isolated leucocytes compared to controls, both assessed at 36 and 66 days post vaccination. Transient reduction in fish weight was observed in vaccinated groups until 10 weeks after vaccination; however at 15 weeks, the weight of the vaccinated group was significantly higher than that of the control group. This coincided with the development of side-effect scores at the injection site that had started to wane by 10 weeks, and the downward trend continued up to the last collection time (41 weeks), although with some variation between sites. The study shows that the tested vaccine protects against pasteurellosis in yellowtail under field conditions and that it is safe for use in the target species.

Antigen profiles of the fish pathogen Moritella viscosa and protection in fish.

AIMS: Moritella viscosa is a gram-negative bacterium that causes winter ulcer disease in salmonid fish cultured in sea water below 8 degrees C. The aim of this study was to study the antigen profiles of these bacteria and to reveal the protection which the antigens induce in fish. METHODS AND RESULTS: Lipooligosaccharides (LOS) and an approximately 17-19 kDa outer membrane antigen were shown to be the major specific antigens of M. viscosa. The size of the wall antigen differed between strain groups and even between strains reacting positively in the same sera. Four different serotypes of M. viscosa were determined by producing polyclonal sera. Western blot analysis revealed that sera from vaccinated fish groups that had good or fair protection reacted against the LOS and the 17/19 kDa antigen, while no antibody response was observed with sera from groups that showed no efficacy. CONCLUSIONS: The study provides evidence that LOS and an approximately 17-19 kDa outer membrane antigen are the major specific protective antigens of M. viscosa, and that the M. viscosa species consists of many different serotypes. SIGNIFICANCE AND IMPACT OF THE STUDY: The results are important for the production of vaccines against winter ulcers and should also lead to better methods of verifying the bacteria and monitoring winter ulcers.

Efficacy of injection vaccines against Flavobacterium psychrophilum in rainbow trout, Oncorhynchus mykiss (Walbaum).

Efficacy of mineral oil-based experimental injection vaccines against Flavobacterium psychrophilum were tested in rainbow trout, Oncorhynchus mykiss (Walbaum), under laboratory and field conditions. The vaccines consisted of formalin- or heat-inactivated whole bacterium cell preparations of two different serotypes (Fd and Th) or a combination of serologically different F. psychrophilum (Fd and/or Th and/or Fp(T);Th). Specific antibody responses against the bacterium in plasma and skin mucus were evaluated post-vaccination with enzyme-linked immunosorbent assay. Efficacy of the vaccinations was determined by challenge trials to F. psychrophilum with the vaccinated rainbow trout. Significantly higher antibody levels in plasma were detected in vaccinated fish compared with mock-vaccinated fish. Injection vaccination did not trigger specific antibody production in the skin mucus. Significantly higher survival of i.p. vaccinated fish compared with non-vaccinated fish was observed during the challenge. The results suggest that mineral oil-based injectable vaccines containing formalin- or heat-inactivated virulent cells of F. psychrophilum effectively triggered specific antibody production and protected the fish against bacterial cold water disease.

Fish vaccines.

Fish vaccines can be delivered the same way we immunize warm-blooded animals. Fish can be immunized by immersion in vaccine for a short period of time--30 seconds to 2 minutes. They can be immunized by injection, intramuscularly or intraperitoneally, and orally by mixing vaccines with feed either by top dressing or by incorporating into feed as an ingredient. Fish also respond to vaccine the same way as other animals do, but since fish are cold-blooded animals, the response to vaccine depends largely on the water temperature. In general, the higher the water temperature, the faster the immune response of fish to the vaccine. During the past 20 years fish vaccines have become an established, proven, and cost-effective method of controlling certain infectious diseases in aquaculture worldwide. Fish vaccines can significantly reduce specific disease-related losses resulting in a reduction of antibiotics use. The final result is the decrease of overall unit costs and more predictable production. Fish vaccines are advantageous over antibiotics because they are natural biological materials that leave no residue in the product or environment, and therefore will not induce a resistant strain of the disease organism. Fish vaccines are licensed by the federal government and closely regulated in the same manner as all other veterinary vaccines to ensure safety, potency, and efficacy. Even though commercial vaccines for aquaculture work really well in terms of protecting the fish against certain diseases, they should be used only as part of the overall fish health management program, because fish vaccines are not a cure-all. Animal husbandry is still the key to success in aquaculture.