Health Management in Tilapia Production

PRESENTATION

BROCHURE

HEALTH MANAGEMENT IN TILAPIA PRODUCTION Carlos Arturo Iregui Castro, Alba Lucía Rey Castaño, Ignacio de Blas Giral, Imanol Ruiz-Zarzuela, Ana Muniesa del Campo

Health Management in Tilapia Production

HEALTH MANAGEMENT IN TILAPIA PRODUCTION Carlos Arturo Iregui Castro, Alba Lucía Rey Castaño, Ignacio de Blas Giral, Imanol Ruiz-Zarzuela, Ana Muniesa del Campo

AUTHORS: Carlos Arturo Iregui Castro, Alba Lucía

Rey Castaño, Ignacio de Blas Giral, Imanol Ruiz-Zarzuela, Ana Muniesa del Campo.

DIMENSIONS: 11 × 20.

PAGE COUNT: 104.

NUMBER OF IMAGES: 35.

BINDING: hardcover, wire-o.

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This book serves as a useful tool for learning about the most com-

eBook included

mon diseases of tilapia (both red and Nile) raised in intensive and semi-intensive systems. It covers both macroscopic and microscopic lesions as well as elements of production and parameters of water quality which are critical to determining the health and disease of these fish.

Presentation of the book This book covers the most common diseases of the two main varieties of tilapia: Nile tilapia Oreochromis niloticus) and red tilapia (Oreochromis spp.), produced in intensive and semi-intensive farming systems in our area of work. It does not cover all the diseases that we have diagnosed in our area, as it is not a scholarly work for specialists, but a useful, easily accessible tool for anyone who wants or needs a basic understanding of health on the farms that produce these fish species.

The book particularly focuses on macroscopic and microscopic anatomical pathology, for two reasons:

• Firstly, unlike other species of fish and indeed animals, and except in the case of a few diseases, tilapia do not show clear macroscopic lesions that would enable one pathological entity to be distinguished from another by observation of clinical signs. Therefore, microscopic analysis must be used for a reliable diagnosis.

• Secondly, tilapia are often farmed in poor quality, warm water, so a diagnosis based solely on a search for a causative agent, especially an infectious one, can be very frustrating and lead to some very costly mistakes. Many micro-organisms that can cause disease in tilapia are normal inhabitants of the water and of the fish themselves, so how should their presence be interpreted by means of microbiology, parasitology or molecular techniques? A thorough inspection of the fish is required, including a microscopic examination. This is all presented to the reader in a most user-friendly manner in the book.

Particular reference is also made to aspects of production and characteristics of the water that the authors’ experience over the years has been shown to be critical to the health, good or poor, of these fish.

Finally, the biosecurity measures proposed are based on a comprehensive approach to disease phenomenon, taking into account the fish’s aquatic environment, the production method used, the detailed examination of the fish and the results from various laboratories.

We hope, therefore, that this book will be a rigorous reference work, both useful and simple, for everyone involved in tilapia farming.

The authors

Health Management in Tilapia Production

The authors Carlos Arturo Iregui Castro Carlos Arturo Iregui Castro earned a degree in veterinary medicine from the National University of Colombia (1979) as well as a specialisation in pathology and a PhD in veterinary medicine from the University of Hanover, Germany (1985).

He has been an assistant lecturer at the Faculty of Veterinary Medicine and Animal Husbandry of the National University of Colombia since 1980 and a lecturer for the Veterinary Pathophysiology track of the Master’s Degree Programme in Animal Health and Production (Mechanisms of Disease and Respiratory Pathophysiology). Since 1994, he has been a lecturer for the Veterinary Pathology Specialisation, and since 2000, he has been a pathologist in the diagnostic department of the Veterinary Pathology and Fish Pathology Laboratory. He is also a leader of the Veterinary Pathobiology Group. His work through this group earned him an award for meritorious research in 2006.

He has published large numbers of scientific articles and book chapters in various international publications. He has also participated in conferences and seminars in Colombia and elsewhere, and has supervised various research projects, undergraduate and master’s dissertations, and doctoral theses on topics relating to mammals and farmed fish, with a special emphasis on diseases of tilapia.

Alba Lucía Rey Castaño Alba Lucía Rey Castaño earned a degree in veterinary medicine from the National University of Colombia in 1995 and a master’s degree in animal health (specialising in veterinary pathophysiology) in 2002. Her master’s dissertation was entitled “Diagnostic systematisation and characterisation of diseases of red tilapia farmed in the department of Tolima (Colombia) and pathophysiology of septicaemic disease”. She is currently pursuing a PhD in animal medicine and health at the University of Zaragoza, Spain with a doctoral thesis entitled “Development of a histopathology model capable of predicting streptococcosis in farmed tilapia”.

She has been associated with the Veterinary Pathobiology research group (Fish Pathology specialisation) of the National University of Colombia since 1998. One of these research projects earned her an honourable mention from the Colombian Association of Veterinary Surgeons in 2004. She has also published scientific articles and book chapters in Colombian and international journals. She is currently a lecturer at Antonio Nariño University (Bogotá, Colombia), where she teaches Histology, Pathology and Medicine in Fish Production.

Ana Muniesa del Campo Dr Muniesa del Campo holds a degree in veterinary medicine (2010), a master’s degree in preliminary research in veterinary sciences (2011), and a PhD in animal health and medicine from the University of Zaragoza, Spain (2016). She has participated in various Spanish and international research projects. She has also secured research contracts that include the MEXUS project developed in collaboration with the University of California (Davis, USA) and a project at the CIAD (Food and Development Research Centre, Mexico), where she worked on development of a health monitoring system for shrimp.

She is an associate professor and lecturer in Epidemiology, Biostatistics and Integration in Aquatic and Exotic Animals for the veterinary medicine degree at the University of Zaragoza, and she has taught courses for institutions and companies in the veterinary sector. She has also supervised final degree projects and research projects for students in the master’s degree in public health. She is currently overseeing various doctoral theses in human medicine.

Imanol Ruiz-Zarzuela Imanol Ruiz-Zarzuela obtained his degree (1993) and PhD (2003) in veterinary medicine from the University of Zaragoza, Spain. He currently works as an associate lecturer in the Department of Animal Pathology in the Faculty of Veterinary Medicine at the University of Zaragoza and he is a de facto diplomate of the European College of Aquatic Animal Health.

He has coauthored numerous papers published in indexed scientific journals and has also cosupervised various research projects, most of them on fish diseases, which has been his main field of research since 1996, particularly in the area of aquatic animal health. To this effect, Dr Ruiz acts as a veterinary technical consultant on this subject for various government institutions, organisations of fish producers and fish farming organisations, and companies linked to the aquaculture sector.

Health Management in Tilapia Production

Ignacio de Blas Giral Dr de Blas Giral obtained his degree (1991) and PhD (2000) in veterinary medicine from the University of Zaragoza, Spain. He currently works as an associate lecturer in the Department of Animal Pathology in the Faculty of Veterinary Medicine at the University of Zaragoza and he is a de facto diplomate of the European College of Aquatic Animal Health. He has coauthored 85 papers in indexed journals and 11 book chapters, and has also cosupervised 21 doctoral theses and 12 master’s dissertations.

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His main field of research focuses on aquatic epidemiology, and he has developed free software programs, such as Win Episcope and WinEpi, to make epidemiological calculations easier, and platforms for epidemiological surveillance in aquatic populations. His work has included implementing and executing epidemiological surveillance programmes, validating diagnostic tests, developing and evaluating treatments (vaccines, probiotics, and antibiotics), detecting risk factors in wild populations and fish farms, analysing risk and evaluating biosecurity measures. He has collaborated as an external consultant with various institutions such as the Spanish Ministry of Agriculture and Livestock, the European Commission, and the Regional International Organisation for Agricultural Health (OIRSA); with research centres such as Ecuador’s National Centre for Aquaculture and Marine Research (CENAIM), the Food and Development Research Centre (CIAD, Mazatlán, Mexico), the Research Institute of Aquaculture (RIA- 2, Vietnam), and the National University of Colombia in Bogotá; and for numerous Spanish and international aquaculture companies.

HEALTH MANAGEMENT IN TILAPIA PRODUCTION Carlos Arturo Iregui Castro, Alba Lucía Rey Castaño, Ignacio de Blas Giral, Imanol Ruiz-Zarzuela, Ana Muniesa del Campo

Table of contents 1. Introduction Principles of tilapia anatomy Principles of tilapia histology Principles of animal pathology

2. Viral diseases Syncytial hepatitis of tilapia (TiLV)

3. Main bacterial diseases Streptococcal infection caused by Streptococcus agalactiae Other streptococcal infections Aeromoniasis caused by Aeromonas hydrophila Edwardsiellosis caused by Edwardsiella tarda Columnaris caused by Flavobacterium columnare Francisellosis caused by Francisella sp.

4. Main parasitic diseases Trichodinosis caused by Trichodina Chilodonellosis caused by Chilodonella White spot disease or freshwater ich (Ichthyophthirius multifiliis) Intestinal coccidiosis Infestation by digeneans Infestation by monogeneans

5. Diet-related diseases Excess or poor-quality protein in commercial feeds Deterioration in the quality of one or more of the feed components Feed contamination Unidentifiable material in the gastrointestinal tract

6. Changes in water quality Thermal stress Environmental hypoxia Low or high pH Ammonium and ammonia Fish waste and other pollutants

7. Biosecurity measures Sampling Measures of control and prevention

8. Bibliography

HEALTH MANAGEMENT IN TILAPIA PRODUCTION 3 Main bacterial diseases

STREPTOCOCCAL INFECTION CAUSED BY STREPTOCOCCUS AGALACTIAE

• α-Haemolytic strains (approximately 1 % of cases).

• Non-haemolytic strains (all S. agalactiae strains isolated by the authors in their study area, which also belong to the serotype IB).

Streptococcus agalactiae is one of the most important bacterial pathogens in the tilapia industry and is the only member of

Streptococcus agalactiae is often found in humans, cattle and fish, but differences between strains makes cross-infection rare.

group B in the Lancefield classification system. This classification system is based on the serological reactions of the carbohydrates in the Streptococcus cell wall, which are differentiated by letters of the alphabet. Streptococcus agalactiae is sometimes referred to as group B Streptococcus (GBS), and there are other Streptococcus species and related genera that also cause disease in tilapia.

Other bacteria that are regularly identified in disease outbreaks in tilapia include Aeromonas hydrophila, Edwardsiella tarda and Flavobacterium columnare, but the incidence of these bacteria is much smaller and they are usually opportunistic, mainly due to poor water quality, de-

PRESENTATIONS • Acute: 80 % mortality. Mainly characterised by haemorrhages.

• Chronic: 20 % mortality. The main clinical signs are: • Lethargy.

• Exophthalmia, corneal opacity.

• Erratic swimming.

• Spinal curvature.

• Asymptomatic.

cay of food in the water from excessive feeding, poor fish handling, etc.

Streptococcus agalactiae causes significant mortality and morbidity in freshwater and saltwater fish throughout the world.

GENERAL CHARACTERISTICS OF THE GENUS STREPTOCOCCUS • Gram-positive, spherical bacteria (cocci) of less than 2 μm in diameter that usually grow in pairs and form chains when growing in a liquid medium.

• Most are facultative anaerobes (they grow in the absence of oxygen, or at very low oxygen concentrations).

CLINICAL SIGNS AND LESIONS The main clinical signs of streptococcal infection in tilapia are: loss of appetite, unilateral or bilateral exophthalmia, intraocular haemorrhages, corneal opacity, abdominal distension, curvature

• They tend to multiply in media supplemented with red blood

of the spinal cord, rigidity, erratic swimming, and haemorrhages

cells, which allow preliminary classification to be made based

at the base of the fins. However, in many cases, no clinical signs

on the haemolysis they cause:

may be seen before the death of the fish.

• β-Haemolytic strains, such as S. iniae (see next section).

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HEALTH MANAGEMENT IN TILAPIA PRODUCTION 3 Main bacterial diseases

Figure 1. Nile tilapia (Oreochromis niloticus). Adult of approximately 500 g in weight. Eye damage caused

by Streptococcus agalactiae.

Yellowish exudate in the anterior and posterior chambers of the eye, mainly consisting of mononuclear leukocytes and fibrin, and most certainly affecting the lens; also multiple linear haemorrhages in different parts of the eye.

Necropsy findings (Fig. 2) are: accumulation of bloody fluid in the abdominal cavity, reddish-brown mucus in the intestinal lu-

Figure 2. Nile tilapia. Streptococcus agalactiae infection. Significant accumulation of gelatinous exudate (fibrin and albumin) in the abdominal cavity (ascites), with the liver adhering to parts of the intestine. The liver looks friable and fragmented, with haemorrhagic areas in the cranial region. The intestine is moderately distended and severely congested.

men, pale liver (occasionally enlarged), enlarged spleen, fibrin deposits in the epicardium, and a brownish to haemorrhagic appearance of the retrobulbar tissue and meninges.

Microscopically, there tends to be a mononuclear inflammatory response with subsequent granuloma formation in the affected organs:

• Meningoencephalitis: from haemorrhagic to granulomatous, with large areas of encephalomalacia (softening of brain tissue) (Fig. 3).

• Inflammatory damage to the choroid, sclera and globe.

• Epicarditis at varying stages of development.

Figure 3. Tilapia brain. Very severe and widespread mononuclear meningitis: two large colonies of cocci can be seen (arrows) in the blood vessel on the right of the photo, one of which is mainly surrounded by macrophages: the red blood cells have also separated from the blood plasma. This is the result of Streptococcus agalactiae infection.

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HEALTH MANAGEMENT IN TILAPIA PRODUCTION 3 Main bacterial diseases

OTHER STREPTOCOCCAL INFECTIONS

Microscopically, a multifocal granulomatous reaction could be

STREPTOCOCCAL INFECTION CAUSED BY STREPTOCOCCUS INIAE

ed the liver, spleen, and eye (which presented endophthalmitis,

Streptococcus iniae was isolated for the first time in Amazon river

bres of the heart. Interstitial nephritis was observed in the kidney,

dolphins (Inia geoffrensis). It was later diagnosed as the cause of

and there was severe diffuse mononuclear meningoencephalitis

mortality in tilapia hybrids that became lethargic, swam erratically

of the central nervous system.

and displayed signs of dorsal rigidity. In the case of the Nile tilapia, it has been demonstrated that mortality can occur in cases of coinfection with the parasite Ichthyophthirius. Like other members of the Streptococcus group, S. iniae is a gram-positive micro-organism that forms structures that vary from pairs to chainlike structures, and it causes complete β-haemolysis.

Huge losses caused by S. iniae are recorded in tilapia farmed in cages in Southeast Asia, especially Indonesia.

seen in various organs, with abundant macrophages, low numbers of lymphocytes and eosinophilic granular cells. This includchoroiditis, and corneal oedema), and areas such as the serosa and epicardium. Degeneration and necrosis were seen in the fi-

It should be noted, however, that all of these findings are similar to infection by other Streptococcus in tilapia.

STREPTOCOCCAL OR LACTOCOCCAL INFECTION CAUSED BY LACTOCOCCUS GARVIEAE Lactococcus garvieae (formerly classified as a Streptococcus) is another member of the family Streptococcaceae, and it infects a wide range of fish species, including tilapia and spotted sorubim (Pseudoplathystoma corruscans) in Brazil.

High mortality rates were recorded in fish weighing 150–250 g in a trial in farmed tilapia in Mexico. Clinical signs were erratic swim-

Both S. iniae and L. garvieae are considered to be emerging zoonotic pathogens.

ming in some of the fish. Macroscopic lesions included corneal opacity and exophthalmia, poor body condition, haemorrhages at the base of the caudal peduncle, and abscesses and ulcers on the jaw. All of these are considered typical of septicaemia. All affected fish exhibited cachexia, pale gills, and darkening of the body, which are lesions typical of other Streptococcus coinfections.

Internal signs were serosanguineous ascites, adhesions, and a mottled liver. Most of the fish displayed enlarged spleen, liver, and kidneys; others presented cerebral oedema and haemorrhage.

The membranes surrounding the fish hearts were whitish-grey

Lactococcus garvieae is a facultatively anaerobic non-motile gram-positive coccus that grows in short chains. Capsulated cultures of this micro-organism are thought to be more pathogenic than noncapsulated forms.

The disease develops as a haemorrhagic septicaemia, with macroscopic and microscopic lesions similar to those mentioned previously, which makes specific diagnosis difficult.

and purulent.

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