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INTERESTING ASPECTS OF COCCIDIOSIS

By Enid Latham - Keeper Western Plains Zoo.
Jan 1998


Since late last year I have been sending faecal samples to Christine Irving a hospital scientist in Adelaide. Christine is very interested in native wildlife. She is a member of Native Animal Network, a wildlife group in South Australia of which I am also a member.

Christine tests the faeces and identifies the strains of coccidia present in the sample. To do this she places the faeces in a solution of Potassium Dichromate to encourage the oocysts to sporulate; a process that can sometimes take months . This is the only way to obtain an accurate diagnosis. This sample is then tested under the microscope by oil immersion and the strains are then identified.

On my property I have six out of a possible seven strains of coccidia that affect Eastern Grey Kangaroos. Until recently there were only five strains present . The sixth strain appeared after two Red Kangaroos were brought from Newcastle without being tested for oocysts. After the loss of one Eastern Grey with a much larger oocyst than had been previously seen on testing ,all animals on the property were tested. The only ones testing positive to these oocysts were the two Reds from Newcastle leading us to believe this strain had been brought by the faeces of these two joeys .

To explain a little on Coccidia I would like to present part of a lecture given by Dr. Ian Carmichial B.V.Sc. D.V.Sc. Melb. given to members of the Marsupial Soc of Aust on research by Michael O'Callaghan:

“There are many protozoa in the sub class coccidia, we will only deal with the Family Eimeriina in particular the sub class Eimeria. There are hundreds of different species, which cause disease in mammals, birds, and reptiles. Each species is identifiable by it's particular size and shape, as well as by various other distinguishing characteristics.

Coccidia are a single celled protozoan parasite and are more complex than either bacteria or virus. Each individual egg cell, or oocyst, contains four internal bodies, each of which have two even smaller bodies within them called sporozoites.

Eimeria enters the body by ingestion only. Firstly the egg or oocyst, is ingested by an animal as it grazes. It then enters the intestine of the animal and its outer shell is digested by the normal gastric secretion of the animal. When this happens, the eight sporozoites are released and directly invade the villi - the actual lining of the gut wall.

Here they produce a membrane around themselves and rapidly multiply asexually by division, up to eight or nine hundred times, to produce what are called schizonts, The infected cells in the gut wall rupture due to this massive production and this releases the enormous number of schizont, which invade more cells within the gut wall and continue this process of rapid asexual reproduction.

Each time a cell ruptures, it is destroyed and there is massive death of cells due to the extremely rapid and enormous production of the schionts.

After the second or third division, the schizonts invade further cells, where gametogony, or sexual division occurs. This simply means each schizont become either male or female. The males then fertilising the females and the fertilised oocysts breaking out of the infected animal's body in its droppings. Under suitable conditions further divisions occur in the soil and the oocysts become infective. The coccidia are now ready to be ingested and repeat the cycle.

There is massive multiplication within and destruction of body cells from a single organism and the period between initial infestation to death can be only three or four days. The infected animal suffers acute pain as the coccidia invade the wall of the intestine, they cause the cells to slough off and the area becomes like a huge ulcer. As the disease progresses, the outside of the intestine becomes red and swollen.

There are no toxins produced by coccidia. The infected animal dies of dehydration, due to the fluid loss caused by the disease and of shock, caused by extreme pain.

Coccidia are strongly host specific and while there is some sharing of parasites between kangaroos and wallabies, there are still species specific ones; that is, some will cause disease in one particular species of animal, but will not cause disease in another species.

Many species of coccidia affect Eastern Grey Kangaroos but not all of these coccidia cause disease in them. Some species may only cause a mild flu-like illness in the animal.

The presence of coccidia oocyst in an animals faeces does not mean that the animal has been infected by the disease, and conversely animals may die without having large numbers of coccidia, or many of the different stages of them, in their faeces. The immature stages cause massive cell destruction, which may kill an animal before the mature form of coccidia even develop.

Macropods are host to many coccidia species, which can easily be identified, but little information is available on which particular coccidia species cause disease, or at what particular stage in their life cycle this occurs. Other species of coccidia infest the liver, particularly of rabbits, but the importance of these parasites in macropods is not known.

However if there is a very high level of oocysts in an animals faeces, this is generally associated with disease. Oocyst count can be eighty to ninety thousand to a gram of faeces, this means three hundred and sixty thousand would be present per teaspoon of dung.”

“If you have macropods, you will have coccidia oocysts on your property.”

(These notes have been used with permission from the Marsupial Soc of Australia).

Christine has explained much about coccidia, as this is a very difficult disease for the lay person to understand. The pathogenicity or ability to cause disease is dependant on the ability of the coccidia to sporulate. The potassium dichromate is used as a solution to encourage sporulation.

In situations where large numbers of coccidia are present that will not sporulate under laboratory conditions, it doesn't mean that they are not pathogenic, as they are affected by the state of the intestine bacterial flora. Stomach contents, acids, and even diet, can damage the coccidia, which does not allow them to sporulate under laboratory conditions. They may also be immature. Some of these coccidia are so fastidious that they will only attack certain parts of the villi.

NO PARASITE IS OUT TO DESTROY IT'S HOST , as it's host is it's essential partner. They co- habitate. It is only in changed conditions that you will get the destruction of the host. Without the host the parasite will die. The environment that we provide for our joeys is artificial and overcrowded, and so we get destruction of the host.

If you were to test the faeces of one animal on a regular basis They will at some time host all strains in your soil. As the gut sheds it's lining regularly the coccidia can be shed without even invading the gut lining.

May I stress to all wildlife carers that when transferring animals between carers to always have the animal checked for coccidia, so that you do not introduce different strains into areas where they have not previously been found. In my situation the Red Kangaroo's were never affected , but it meant devastation to the Grey population on my property.




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