• Zoothamniosis disease is one of the parasitic diseases found in vannamei shrimp caused by Zoothamnium penaei which usually lives with poor water quality. It causes the death of shrimps both in pond and hatchery. An abundance of Zoothamnium sp. infested the vannamei shrimp this is still reasonable so long as they do not cause high mortality. But, they can also cause problems in shrimp culture when the environmental conditions are poor and suitable for its development. This parasite that attack shrimps in order to determine the factors causing a decline in growth, meat quality and productivity.
• This disease causes the shrimp to breathe hard, difficult to move and cannot find food, difficult to moult, inhibit growth, reduced economic value and cause death to 91%. In addition, this disease is a predisposing factor of secondary infection by bacteria and viruses.
• Protozoan ectoparasite abundance varies greatly depending on the different physico-chemical conditions of the water bodies. Parasitic groups of protozoans are generally found in environmental conditions that experience instability in the water quality, especially temperature, as Zoothamnium sp. can breed faster in environmental conditions that have a temperature value above 30°C. Giving too much food causes the remaining food to be left in many ponds. This means that the content of the organic matter in the pond is high and spurs on the growth of the parasites which are also able to grow well.

Symptoms

Zoothamnium sp. Infected shrimps show black/ brown gills or appendage discoloration or fuzzy/cottony appearance due to a heavy colony of the organisms. In some cases, the severely affected shrimp die during the molting period.

The base of Zoothamnium forms a circular disc that fuses with the epicuticle but does not penetrate the underlying cuticle or epithelium. Discoloration of the gills is a common symptom of fouling by organisms and also detritus, silt, or iron which are trapped by the fouling organisms. 

Treatment

Chlorine and formalin are often used to treat those commensal organisms if shrimp display heavy infection. Changing water is the most preferable management, which stimulates molting of the shrimp in order to reduce the infestation.

Prevention and Control

Prevention and control of the occurrence of surface fouling are usually done through maintenance of good sanitary conditions at the pond bottom and the overall pond area. Organic matters and suspended solids in the pond should be reduced to prevent the attachment of those fouling organisms. This is achieved by changing the water or applying lime.

Infectious Myonecrosis Virus (IMNV) is an emerging shrimp RNA virus causing the disease, infectious myonecrosis (IMN). The disease was first recorded in Pacific white shrimp, P. vannamei in Brazil in 2002 and then in 2006 in Indonesia including Java island. The disease causes significant economic losses to aquaculture due to associated mortalities in P. vannamei in grow out ponds. The virus infects all the life stages of shrimp including post larvae, juveniles, and adult, but the mortality was observed in the juveniles and adult with a cooked appearance.

Causes

IMN is caused by a putative totivirus. IMNV particles are icosahedral in shape and 40 nm in diameter. Transmission via water and vertical transmission from broodstock (trans-ovarian or by contamination of the spawn eggs) to progeny is also likely to occur. IMNV may also be transmitted among farms by feces of seabirds or shrimp carcasses. Outbreaks of IMN with sudden high mortalities may follow stressful events such as capture by cast-net, feeding, sudden changes in salinity or temperature, etc., in early juvenile, juvenile, or adult P. vannamei in regions where IMNV is enzootic.

Symptoms

IMN disease causes significant mortality in grow out ponds and is characterised by acute onset of gross signs including focal to extensive whitish necrotic areas in the striated muscle, especially of the distal abdominal segments and the tail fan, which may become necrotic and reddened similar to the colour of cooked shrimp.

Juveniles and sub-adults of P. vannamei, farmed in marine or low salinity brackish water, appear to be the most severely affected by IMN disease. The principal target tissues for IMNV include the striated muscles, connective tissues, haemocytes and the lymphoid organ parenchymal cells. Severely affected shrimp become moribund and mortalities can be instantaneously high and continue for several days. Mortalities from IMN range from 40 to 70% in cultivated P. vannamei, and FCR of infected populations increase from normal values of ~ 1.5 to 4.0 or higher.

Prevention

No effective vaccines for IMNV are available. IMN can be prevented using SPF broodstock and practicing BMPs. 

Why Bacteriophages?

With emergence of highly virulent pathogens in animal health and aquaculture, there is need for highly effective therapeutic product which can reduce usage of sanitisers and antimicrobials. Continuous use of sanitisers and antimicrobials lead to damage of microbiome (the normal non-pathogenic beneficial bacteria) in aquaculture pond ecosystem and shrimp gut. Recent explosion of scientific research has brought to light the importance of maintaining good and unfluctuating microbiome in shrimp and fish health and aquaculture success.

Under this condition Bacteriophages against virulent pathogens in aquaculture will be highly helpful in maintaining the natural ecosystem of the pond while killing the aquaculture pathogens. This strong argument inspired Salem Microbes to initiate Bacteriophage research as early as 2018 and has invested in infrastructure, technology, and technical competence in bacteriophages-based solution development for Aquaculture, Poultry and Food safety.

Salem Microbes possessing 23 years of probiotic tradition has always travelled with Bacteriophages hand in hand from screening to production operations. In the current day scenario, we are ‘embracing the foe as a friend’ to control pathogens of aquaculture. So, we are just jumping sides and exploiting their potential.

Today, we assure that we are in the forefront of bacteriophage research, specialising in isolation, characterisation, and formulation of Phage cocktail within a short turnaround time. Our Research & Development ensures quick screening in case of a sudden disease outbreak to make custom formulation of Bacteriophages from our expansive library of Bacteriophages maintained on-campus.

Phages and Probiotics , a Synergistic combination

Probiotics have played an undeniable role in the environmental management of the shrimp pond and are going to continue to sustain the shrimp ecosystem microbiome, the only catch here is use of quality probiotic inputs which farm owners and technical experts should be aware of.

Probiotics reduce the chances of infection by Competitive Exclusion, but once the critical levels of Vibrio species dominate the environment, it become nearly impossible for probiotic bacteria to exclude Vibrio species. Such critical condition demands quick and sure shot treatment, which is non residual in nature and non-GMO and which does not affect the (microbiome). Here comes the concept of Phage Therapy which is highly specific and quick acting in nature specifically targeting the aquaculture pathogens.

How a Bacteriophage product become relevant to a condition?

A Good Bacteriophage consortia should contains identified lytic phages, specific against pathogens selected from the target environment. Phage cocktails against Pathogens should be continuously upgraded to maintain the pathogen spectrum, specificity and infectivity.

How does a Phage works?

Bacteriophages are Viruses of bacteria which enter the bacteria, use the bacterial source of energy, hijack the bacteria, multiply inside the bacteria and kill them by lysis. When they kill the bacteria, each virus which enter the bacteria multiplies and releases 10 to 100 mature ready-to-attack bacteriophages which are capable of infecting and destroying next set of target pathogenic bacteria.

V PHAGES Consortia

V PHAGES Cocktails for Hatchery and Growout are quite different in their Formulation, Specificity and Purpose. V PHAGES HATCHERY satisfy the need for targeting pathogens specific and prevalent in Hatchery water source, live feeds and also its environment. V PHAGES GROWOUT targets the common pathogens esp Vibrios which are the main cause for bringing down the productivity of a shrimp pond by causing Vibriosis leading to White gut, White faecal disease, off feed, Running Mortality Syndrome and crop loss.

"V PHAGES " cocktails target Vibrio species as,

• Vibrio parahaemolyticus
• Vibrio alginolyticus
• Vibrio harveyi
• Vibrio campbellii and other pathogenic Vibrio sp.

When TO USE IN SHRIMP HATCHERIES?

• To reduce the load Vibrio sp. of the live/ wet/ frozen feed used in brood stocks.
• To reduce Vibrio sp. load in artemia tank.
• To reduce the Vibrio sp. associated problems in Conversion and PL tanks.
• To reduce Vibrio sp. load in intake water thereby preventing biofilm formation in the storage tanks and pipe line downstream of the intake tank.

When TO USE IN SHRIMP GROWOUT PONDS

• Drop in feed intake with increase in yellow or green colonies in TCBS plates
• White gut and White faecal matter appearance coupled with more green colonies in TCBS plates
• Early stages of Running mortality syndrome with empty gut symptom.
• During stocking to safeguard against survival loss of PL’s.
• To increase the efficacy of Probiotics by reducing their primary enemies, the pathogenic

Comparing with Other Therapies

V PHAGES are Natural isolates screened and selected for their strong and fast action against their challenged targets. They do not disturb the Probiotics and other non-pathogenic natural microbiome which are otherwise destroyed by other treatment approaches as Sanitisers, Disinfectants and any products of anti-microbial action. These Phages does not leave any residues on the shrimp or environment as they are Natural. All  bacteriophages in V PHAGES cocktail are Genotypically characterized to ensure proprietary formulation and traceability, which makes them special.

Conclusion

Though Bacteriophage research and applications are known for many years very few products have seen the light of the day. Even these products become irrelevant when they are not supported by a strong expertise in the field and research infrastructure. Salem Microbes has established these capabilities and commits to be in the forefront of giving the Best to its farmers to make their Shrimps Healthy, Productive and Profitable.

Black gills, black gill syndrome, black gill disease, or melanization of the gills is symptomatic of several causes of gills disease. Shrimp Black Gill Disease has been one of the most frequent shrimp farming problems and caused many deaths, especially in the late rearing period. There are infectious and noninfectious causes of black gill disease. Infectious causes include Fusarium solani, Vibrios, and Lagenophrys, while noninfectious causes include nutrient deficiencies and exposure to pollutants and contaminants.

A number of abiotic and biotic reasons have been attributed to the black gill in shrimps. Presence of excessive levels of toxic substances such as nitrite, ammonia, heavy metals, crude oils etc. in the culture water may lead to black gill disease. High organic load, heavy siltation and reducing conditions in rearing pond can also cause this disease in shrimps. Attack of certain bacterial, fungal and protozoan pathogens can also cause black gill condition in shrimp.

Causes:

Black gills in shrimp can be caused by several things.

• Accumulation of debris in gills: This is usually associated with poor pond bottom conditions. Lack of proper preparation of the pond before stocking, large amounts of black soil, lack of aeration, irregular water change during rearing, and organic contaminants, and nutrtional deficiency could trigger the disease.
• Some fungal species including Fusarium solani, Aspergillus flavus, and A. awamori  causes disease. This disease is epizootic and can cause mass mortalities. In infected shrimp, the gills have a very dark, deep black colour.
• In the initial stages of this disease, the gills turn orange-yellow or light brown. Eventually, the gills turn darker until they are black. Vibrio-related diseases spread rapidly. Bacterial agents including Vibrio harveyi and Photobacterium damselae  were reported to cause black gill syndrome.

Symptoms:

• Affected shrimps have gills with brown to black discoloration, in acute cases necrosis and atrophy of the gill lamellae may be apparent. The blackening is due to the deposition of melanin at sites of massive haemocyte accumulation, followed by dysfunction and destruction of whole gill processes.
• Shrimp comes to surface in spite of sufficient dissolved oxygen in the water
• Mortality in severe cases

Prevention:

• Absolute control over feeding is very important in preventing black gill.
• Use good quality probiotics at regular intervals with optimum dosages. This helps in reducing the organic load and toxins in the pond.
• Controlling water colour and preventing excessive blooms during culture prevents algae crash and accumulation of organic matter in the pond.
• Provide sufficient aeration to the ponds.

Remedies:

Treatment of the black gill disease depends upon the cause of the disease. 

• Preventive or corrective measure may be adopted to avoid or reduce the biotic / abiotic factors in the rearing pond to control the disease condition.
• If noticed black gill in some shrimps, suggested to change the water more often and also provide more aerators.
• Reduce feeding till water quality improves.
• Apply good quality oxygen enhancers daily till complete recovery.
• Use probiotics to clean the ponds and absorb toxic gases.
• Addition of agricultural lime (CaCO3) according to the pH concentration is also recommended.