Columnaris also referred to as cottonmouth is a symptom of disease in fish which results from an infection caused by the Gram-negative , aerobic, rod-shaped bacterium Flavobacterium columnare. It was previously known as Bacillus columnaris, Chondrococcus columnaris, Cytophaga columnaris and Flexibacter columnaris. It is often mistaken for a fungal infection. The disease is highly contagious and the outcome is often fatal. It is not zoonotic.
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By Intervet - Columnaris caused by Flavobacterium columnare previously called Flexibacter Columnaris, Cytophaga columnare or Myxobacterium columnare is one of the most common diseases in tilapia culture. Introduction Continuing the theme of diseases in tilapia we have highlighted in the previous two issues Intervet Aquatic Animal Health Newsletter no.
The disease is highly contagious, especially at the fry and fingerling stages. Infected fish often display external lesions such as skin and gill erosion, and necrosis. In acute cases, these lesions may spread quickly and lead to high mortality within a matter of hours.
Oman is looking to join the increased interest in aquaculture that is currently taking place in the Middle East, having …. An non-profit initiative designed to encourage more Americans to set up their own own backyard aquaculture systems has j…. Some of the key means for fish farmers to tackle the threat posed by tilapia lake virus TiLV were outlined in a webina…. Flavobacterium columnare on agar plate Mouth necrosis Tail rot caused by columnaris Saddleback lesion Gill necrosis Causative agent F.
These bacteria have a characteristic rhizoid pattern of growth on a low nutrient agar medium. Outbreaks are known to occur as a result of both temperature and environmental stress. Clinical signs External Most columnaris infections are external manifested and present first as brown to yellowish-brown lesions on the gills, skin and fins. The lesions may first be seen only as a paler area that lacks the normal shiny appearance.
These sores are usually surrounded by a zone with a distinct reddish tinge. Early signs of infection also include fin erosion. On the mouth, the lesions may look moldy or cottony, and the mouth can be severely affected.
The gill lesions are typically necrotic and the filaments disintegrate as the bacteria invade them. Internal Less commonly, the infection will be observed internally. During acute outbreaks, bacteria sometimes reach the blood system, resulting in a systemic infection. Epidemiology Fish are susceptible to columnaris following some degree of stress. Abrupt variations in water temperature are likely to induce and accelerate the progression of this disease. Poor water quality, inadequate diet, handling and overcrowding are also stress factors likely to induce an outbreak.
Columnaris occurs frequently in fry production units hatcheries but also in cages and closed recirculation systems grow-out facilities. Once established, the disease is highly contagious and may spread horizontally from fish to fish, causing high mortality rates.
Infections may also stem from the environment, through contaminated nets, specimen containers and even food. The presence of columnaris may also lead to secondary infection or other diseases; for example, winter saprolegniosis is often preceded by columnaris. Diagnostic methods A presumptive diagnosis is obtained by observation of typical clinical signs such as saddleback lesions, or necrotic gills and mouth. Additionally, the bacteria can be observed in a wet mount of infected tissues observed under light microscopy.
A definitive diagnosis requires bacterial isolation on a low nutrient medium such as cytophaga agar and identification in the laboratory.
Control and treatment The ideal way to eliminate the occurrence of columnaris is to alleviate stress in the cultured fish population. The bacteria thrive on organic wastes and these can be controlled by regular water changes. Proper diet, maintaining good water quality and avoidance of excessive handling will keep the fish from being stressed. To avoid spreading the bacteria, it is important to disinfect all equipment after each use and to use separate equipment at each rearing facility.
But, this can be difficult in practice; however, stress should be minimized as much as possible. Salt ppt can be used to control the disease in hatchery tanks and to reduce the chance of infection during transportation. In many cases, farmers are only able to partially control outbreaks by using antibiotics. However, this is not a sustainable practice. Best results are obtained if affected fish are treated as soon as the disease is detected. Infected fish display a reduced appetite and, consequently, antibiotics applied orally are generally ineffective.
This may lead to selection of resistant bacteria leading to enhanced problems in the future. In general, antibiotics only prevent the infection from developing further. In the future, we hope that a vaccine against F. More articles on freshwater fish Is Oman set for a major upsurge in aquaculture? Non-profit seeks to inspire backyard aquaculture 29 May How to tackle tilapia lake virus TiLV 28 May View more.
Flavobacterium columnare on agar plate. Mouth necrosis. Tail rot caused by columnaris. Saddleback lesion. Gill necrosis.
Columnaris Disease in Aquarium Fish
Metrics details. Flavobacterium columnare F. This bacterium affects both cultured and wild freshwater fish including many susceptible commercially important fish species. Especially in the last decade, various research groups have performed studies aimed at elucidating the pathogenesis of columnaris disease, leading to significant progress in defining the complex interactions between the organism and its host.
Four Flavobacterium columnare strains AJS were isolated from black mollies Poecilia sphenops and platies Xiphophorus maculatus , showing white spots on the back, head and skin ulcers. The isolates developed characteristic rhizoid yellow pigmented colonies on Shieh agar and typical growth in Shieh broth. They were Gram-negative, filamentous bacteria exhibiting flexing movements. When compared to F.