Try to contact Dr Leszek Guz from Depatment of Fish Diseases and Biology, Faculty of Vet Med, University of Life Sciences in Lublin, Poland. He is available via ResGate.

It is recommended to resolve this question via using molecular diagnosis after a preliminary morphological studies. please check this article and its references http://www.ncbi.nlm.nih.gov/pubmed/23556024

Balantidium coli is the only species foundas human parasite. You have to look this organisms carefully carefully, since there are many other ciliate protozoan that parasite fishes, frogs, lizard, etc. Whashing this picture, the citostome does not look like a Balantidium citostome. In addition the nucleus is not similar to the Balantidium species. To differentiate genus or species sometimes it is neccesary to perform silver stain like Klein stain the easier one, or others (i.e. Protargol technique)

Thanks for your answers.There are some other photos of Balantidium, including H& E staining and light microscopic views. Please look at them!

Dear Misael,

Thanks for your nice suggestion for pathological staining. If it is not a Balantidium, what do you think it is?

Other images!

The Balantidia (species) were reported in fish:

Balantidium ctenopharyngodoni

Balantidium polyvacuolum

Balantidium barbi

Balantidium sigani

and, etc.

Whashing the the brown color picture, I see a nucleus and a special cytostome characteristic of the genus Nycthotherus a ciliate that is present in some cold blood animals. Let me chekc a little bet more in this subject and I willl let you know any additional information

Additional information. some new species of Nyctotherus in fishes have been described, but usually all of them are just commensal parasites. Could you explain me how did you get the tissue invasion? It probably help me in order to give you a better advise.

We performed this study in different seasons (spring, summer, autumn and winter) in four separated sampling areas. During the sampling, a total of 176 fish were captured and transferred to our laboratory and were kept in aquaria. Each fish were then eviscerated using standard method and the last third part of intestine has been checked for protozoan parasites using wet mount. If any parasite were found in light microscopic observation (36.9% of captured fish were infected by this parasite), the intestine were fixed by 10% formalin and then stained by H&E for Histopathological investigation.

O.K. it looks like that parasite could be invasive. Have you check the Nyctotherus species. As far as I know they did not produce tissue lesions( I will check a little bet more), but anyway Let me review something else to thes respect.

The more Known invasite cilate for fishes belong to the genus Ichthyophthirius, specially at the skin level. However there has been found I. multifillisin the peritoneal cavity. This species is morphological similar to Nyctotherus, but not to Balantidium. Why you do not chect it. I hope this new information will help you in your research.

Dear Dr Chinchilla,

Thanks for your help.

In this study we checked skin, gills and digestive track for protozoan and metazoan parasites. In this respect, the only protozoa, which have been found in skin, were Trichodina and Ichthyophtrius mulifilis. In the intestine, we observed Myxobolus and Myxidium and Balantidium(???). Other nematodes, digenean and monogenean Trematodes have been also found.

Anyway, please lead us to recognize this species, is that a Balantidium or not? If it is a Nyctotherus, please let us know according to which character(s) you can make sure us about it.

Washing your brown photos the organisms present a expanden macronucleusand over it a shadow of a Nycthotherus like cytostome is seen. As you probably know this organelle in Balantidium is just in one apice and it has a cone like form. Nycthotherus present a bigger and somehow curved cytostome. If you have the material take a look on these details; it will help.

Thanks Dr Chinchilla,

I will try to find these details in our specimen.

Hello Pedram, sorry to comment your post so late. The images are not very clear, however it is possible that the parasites correspond to Nyctotherus. Besides the comments made by Dr. Chinchilla about the citostomes (sort and straight in Balantidium, large and curved in Nyctotherus), it is also possible to differentiate them by the shape of the macronucleus. In Balantidium, it is bean-shaped, usually clearly bent and U-shaped; in Nyctotherus, the macronucleus has an elongate to triangular-like shape. Maybe this also helps you.

simon correa mrc unit the Gambia

Balantidium is ciliated all round and is larger than a round worm egg.It is covered with many small cilia which helps it to move with rapid strokes.It also have a large kidney shaped nucleus next to a small round nucleus

Balantidium coli is a miscellaneous intestinal protozoa that has a kidney bean shaped macronucleus and is the largest protozoa that is ciliated. It mainly resides to the colon of the large intestine in the terminal ileum and the term Balantidium is also termed as “little bag”. It is associated with Balantidiasis which is a large intestine disease wherein stool can be diagnosed in the labor by DFS or Sigmoidoscopy.