Bacterial infection

Bacterial infections seem to be more widespread in shrimps than was thought a few years ago.

There are many different strains of bacteria. Not all of them trigger the same symptoms, and not all of them possess the same infectiousness. Some infections are rather mild, with only few dead shrimps, few and far between, and some shrimps that show some symptoms like e.g. a whiteish abdomen but behave normally otherwise and look relatively healthy. Other infections are ravaging, infection rates are high, and many shrimp die.

The most common infectants are ubiquitous bacteria, i.e. they are found in pretty much every tank and only become infectious if the shrimps' immune system is damaged or if the bacterial load in the aquarium gets too high. Among them are, most commonly, Aeromonas spp. and Pseudomonas spp.

Possible symptoms:

• the large abdominal muscle becomes opaque-whiteish, the reason for which is damage to the gills - this discoloration is a sign for oxygen deficiency (might also be due to other reasons)
• discolorations of the internal organs, often a reddish-pink orange
• whiteish, often asymmetrical discolorations of the skin
• rust or burn spot disease (for treatment and prevention please see Burn spot disease)
• fading colors
• lost limbs
• broken antennae
• a little breach appears between the 3rd and 4th abdominal segment, some shrimps even show a downward kink there
• the shrimps are lethargic
• the shrimps stop eating
• moulting problems
• the shrimps just topple over and die without having shown prior symptoms
• no massive deaths, but some (few) shrimp die every day or so
• dead shrimp are not firm, become opaque and white very soon and fall to pieces when removed from the tank

Photos: the Logemann brothers

Not all of these symptoms may appear - and some of them can be caused by other factors. Before you start an antibacterial treatment you should make absolutely sure that the problem is not caused by (possibly slowly developing) poisoning or if the animals were kept at less-than-optimal conditions or do not get wholesome food.

Reasons for a bacterial infection:

A shrimp's immune system is rather rudimentary, which makes them easy prey for infections when the microbiological load in the tank increases too steeply, when new shrimps are added to the group whose bacterial fauna is different, when the shrimps are stressed or if their immune system is afflicted by outward circumstances like suboptimal keeping conditions.

Especially shrimps from habitats with low microbiological contamination (i.e. shrimps from creeks like e.g. Caridina cf. cantonensis "Bee" or "Tiger", but also shrimps from the Malili Lake System on Sulawesi) have difficulties with high bacterial loads in the water, and they fall prey to diseases relatively quickly.

Prevention:

• all measures that promote a good development of filter bacteria are detrimental for those bacteria that cause diseases in the water
• make sure your water quality is good, and aim for a nitrate content of less than 10 mg/l
• siphon off the substrate at regular intervals, especially in the place where you feed
• remove dead plant parts and dead animals from the tank as soon as possible
• quarantine new shrimp before adding them to the group
• do regular partial water changes with approriate water parameters (make sure the nitrate is low when you use tap water)
• continuously having autumn leaves and black alder cones in the tank also helps

What to do when there is an outbreak:

Remove dead shrimps and shrimps showing one or several symptoms at once! Diseased shrimps may be treated in a quarantine tank (no substrate, few plants, either a small filter or just an air stone, regular water changes and only very little food). The tank where the disease has broken out has to be treated even though all shrimp with symptoms have been taken out.

Treatment without chemical drugs, given that the disease is mild:

• see above, under Prevention - make sure your shrimp are kept at optimal conditions!
• there are several natural remedies you can treat a mild outbreak with, like dried green walnut leaves, Catappa leaves or bark, cinnamon sticks and so on
• change 80% of the water every other day, for at least a week or until no shrimps show symptoms any more

Treatments with chemical drugs:

• see above, under Prevention - make sure your shrimp are kept at optimal conditions!
• when using antibacterial medication, keep in mind that these also kill all filter bacteria - use an air stone when treating the tank and feed only tiny amounts during as well as for two weeks after the treatment!
• ALWAYS dose according to the instructions on the package, do not underdose or you'll promote the proliferation of resistent bacteria
• during treatment, active carbon has to be taken out of the filter. Also remove zeolith from the tank, do not use water conditioner
• for bacterial infections of shrimps, some medications have proven suitable (availability depends on national legislation): Baktopur (agent: acriflavine), Furanol 2 (agent: sodium nifurstyrenate) and medicines containing nifurpirinole
• in the case of persistent infections or infections caused by resistent germs, Desamar B100 is an alternative to the drugs listed above. It is a disinfectant originally used for Koi breeding that has antibacterial, antifungal and antiviral properties. Make a stock solution by diluting 30 ml of Desamar B100 in 1 l of distilled water. Of this, you dose 10 ml to 10 l of tank water. Infected shrimp may still die, but half a week at the latest after Desamar has been added no more shrimp ought to die. If not, you can re-dose. Remove from the tank by taking up your regular water changes. Feed sparingly for four weeks, keep an eye on the nitrite!