Many pathogens and bacteria are a natural component of the habitat and normally, under ideal conditions, do not cause any diseases. A healthy shrimp is able to keep these pathogens under control with its immune system. There is a balance, symbiosis, between the host and pathogens. The bacteria e.g. of the intestines are even beneficial digestive aids. These bacteria are apatogenic (non-disease causing) microorganisms. This form of partnership where two organisms live together and benefit from one another is called symbiosis. If this balance is disturbed as a result of stress, the immune system is weakened and diverse bacteria and fungi find an easy target. Intoxication from ammonia, nitrate or nitrite, excessively high or low temperatures, wrong pH level, oxygen deficiency or pollution of the water with toxins are all unmistakable factors which cause stress, and therefore play an important role in connection with outbreaks of disease. Parameters of this kind can be analysed locally by your pet store or you can do it yourself by using common test reagents. Thus your own diligent care is the best weapon against diseases. Even though crustacea kept in an aquarium or aquaculture grow under unnatural conditions which may lead to greater spreading of germs and a higher frequency of disease, you have the advantage of being able to closely follow what is happening in your tank and make sure that everything is working properly. At the same time, you can also see clearly whether your pets are in good health or not. If you suspect that your pets may be ill please make sure to immediately consult a pathobiologist for aquatic animals or your pet store.
In the following, you will find a list of diseases which are frequently described by shrimp keepers. This will help you intervene in time as a result of your observation skills and background knowledge.
Different symptoms may occur in a bacterial infection, depending on which organs have been infected. Usually, though, no more than 2-4 animals die per day. Rather, they usually die one by one over a period of days and weeks. When there is an infection, a large number of different bacteria is usually found in the organs as well as on and under the shell.
In this context, we distinguish between internal and external infections and infections of the organs. You will find more detailed information on the disease and its symptoms and treatment possibilities in our booklet, Crustacea and Shrimp in the Freshwater Aquarium:
In addition to bacteria and parasites, fungi can also cause diseases in shrimp. All fungal diseases are referred to as mycoses. A relatively small group of fungi has specialised in warm-blooded organisms and causes diverse diseases in humans, animals and plants. An infection of internal organs by fungal spores (internal mycoses) usually occurs as a result of food intake. If the immune system is intact, they will not be able to harm the shrimp. However, if the infected organ is damaged too severely by spores, the shrimp will die. It is almost impossible to make an accurate diagnosis externally. This can only be done under a microscope.
Columnaris disease, also referred to as saddleback or cottonmouth, is caused by caused by rod-shaped protozoans (single-celled organisms) which cover the surface of crustacea and fish with a cotton-like layer. They are 200 - 250 um long, can form up to 2 mm long colonies and are also visible with the naked eye. The ciliate, Bell animalcules or Vorticella, attaches to the shell of crayfish in order to feed on bacteria and particles in the water.
Time and again, the tail - more precisely the muscle tissue - of the shrimp turns a white or milky colour. These symptoms are also called muscle necrosis. In biology and medicine, necrosis refers to the destruction of individual or multiple cells which takes place in a living organism. This leads to an inflammatory reaction, causing the surrounding tissue to decay. Protein being released when the cells decay, creating the milky-white discolouration in the tail.
This disease refers more to a symptom than an exact diagnosis of a disease, so that it can also be placed in the category of bacterial infections as well as in the category of fungal infections. The symptoms can be caused by fungi (e.g. Ramularia astaci, Cephalosporium leptodactyli and Didymaria cambari) and/ or gram-negative bacteria (Aeromonas, Pseudomonas and Citrobacter, etc.).
Further information on diagnosing and treating shrimp diseases can be found in our free booklet:
Simply click on the link above and download the information material free of charge.
Text and photos: Michael Wolfinger/www.crustakrankheiten.de