talk by Dr. Ian Carmichael, B.V.Sc., D.V. Sc Melb,
Chief Veterinary Parisitologist at the South
Australian Research and Development Institute at
Marsupial Society of Australia Inc. General
Meeting, Thursday 21st May, 1998.
Coccidiosis has had a direct effect on everyone: -
twenty or thirty years ago, chicken was an
exceptional dish in Australia and was a similar
price to lobster. This was because up until that
time, it was not possible to intensively house and
produce chickens due to persistent outbreaks of
coccidiosis. The situation changed with the
development of prophylactic drugs against
coccidiosis, when it became possible to
intensively breed chickens.
development of drugs has not happened in relation
to other animal industries nor in relation to
The Life Cycle of Coccidia. Genus Eimeria
are many protozoa in the Subclass Coccidia, but
this talk will deal only with the Family Eimeriina,
in particular, the Genus Eimeria. Within the genus
Eimeria, there are hundreds of different species,
which cause disease in mammals, birds and
reptiles. Each species is identifiable by a
particular size and shape, as well as by various
other distinguishing characteristics.
Coccidia are single-celled protozoan parasites
and are more complex than either bacteria or
viruses. Each individual egg cell, or oocyst,
contains 4 internal bodies, each of which have 2
even smaller bodies within them, called
infect the body by ingestion y. 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
secretions of the animal. When this happens, the 8
sporozoites are released and directly invade cells
of the villi, the actual lining of the gut wall.
they produce a membrane around themselves and
rapidly multiply asexually, by division, up to 800
or 900 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 schizonts, 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 schizonts.
the second or third division, the schizonts invade
further cells, where gametogeny, or sexual
division, occurs. This simply means that each
schizont becomes either male or female, with the
males fertilising the females and the fertilised
oocyts breaking out of the affected cells and
passing out of the infected animal’s body in its
droppings. Under suitable conditions, further
division occurs in the soil and the oocyst becomes
coccidia are now ready to be ingested and repeat
is massive multiplication within and destruction
of, body cells from a single organism and the
period from initial infestation to death may 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 progress, the outside of the
intestine becomes red and swollen.
are no toxins produced by coccidia - the infected
animals die of dehydration, due to the fluid loss
caused by the disease and of shock, caused by the
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.
species of coccidia affect Eastern Grey Kangaroos,
but not all of these coccidia cause serious
disease in them. Some species may only cause a
mild flu-like illness in the animals.
presence of coccidia oocysts in an animals’
dropping does not mean that the animals has been
infected by the disease and conversely, animals
may die without having either large numbers of
coccidia, or many of the different stages of the
them, in their droppings. The immature stages
cause massive cell destruction which may kill an
animal before the mature forms of coccidia even
Macropods are host to many coccidia species,
which can be easily identified, but little
information is available on which particular
coccidia species cause actual 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 animal’s droppings, this is generally
associated with disease. Oocyst counts can be 80
to 90 thousand per gram of faeces - this means 360
thousand would be present per teaspoon of dung.
you have macropods, you will have coccidia oocysts
in the soil on your property.
affecting Oocyte Production
Oocyst production may only need some small change
to make it flare into clinical disease.
- some species of coccidia are
better breeders than others.
- there may be some degree of competition within the gut between
various coccidia species.
- the degree of host immunity has an
effect on oocyte development - while generally
young animals are more susceptible than adults, if
older animals which have never previously been
exposed to coccidia are exposed at the same time
as young ones, they also will become badly
affected. In other words, no previous exposure
whatsoever leads to disease infestation, just as
adults tend to be sicker with chicken pox and
measles than children do.
- when there is “crowding” in the
gut with high numbers of parasites, egg production
of the individual coccidia species falls.
- poor nutrition of the host
increases their susceptibility.
- some strains of coccidia from different geographical locations
may be stronger than others.
- geographical location may have a
bearing - in some areas of Australia, animals are
more likely to get ill than others. Cold, wet
areas appear worse than hot dry areas.
- climatic extremes, in particular
cold, wind and rain, may precipitate outbreaks.
- stress factors, while mainly based
on evidence from mammals, are a very important
factor in both mammals and birds, and it would
appear that this is similar in marsupials. It is
strongly suspected in kangaroos, but it can differ
within species. While Eastern Grey Kangaroos are
well known as “spooky”, or nervous animals and
stress very easily, all macropods stress fairly
easily. Stress factors can act as triggers to
- movement and transporting (In
cattle, the longer the distance they are moved,
the more there is an increase in the likelihood of
them developing Salmonella.)
- handling or disturbance by strangers
- extremes of weather - wind, rain, heat, cold. (A clearly defined
factor in mammals.)
- changes in diet - these must always be introduced gradually.
- specific types of food - e.g. unsuitable food.
- crowding or overcrowding.
- harassment, even if only mild, by other animals or children-
noise or movement.
- faecal contamination of food.
- the size of the infecting dose - the higher number of oocytes
ingested, the more likely it is than active
disease will occur. It is never too late to move
animals off contaminated ground.
species of coccidia live on the surface of the
inner lining of the intestine and cause no
problem. They are sloughed off naturally with
normal body wear and are of biological interest
only. It is only those parasites which burrow deep
into the cells of the intestinal wall and rupture
the nucleus of these cells which are of
no work has been done in relation to macropod
coccidia, it has been established that the
coccidia species which affect chickens can last up
to 20 months in the external environment.
suspected that macropod coccidia species, having
evolved in a hot, dry country, may be capable of
lasting much longer. It is known that wet, shady
conditions help them survive. Certainly they have
developed to cope with various ranges of
traditional disinfectants, Sulphuric Acid and
Sodium Hypochlorite, hardly affect coccidia;
indeed, they are used to clean them up for
presentation for research. Ammonia appears to be
the best disinfectant to use.
illogical for a parasite to kill its host, as this
only leads to self-extermination. Co-evolution
over millions of years has brought about a certain
balance between this parasite and its host.
normal circumstances, the parasite enters its
host, reproduces, and drops out. Only if something
extra happens is this balance thrown out to cause
a diseased state in the host animal.
Clinical disease is suspected to often follow
confinement of animals and as this has been proven
in the case of poultry, there is no reason to
suspect macropods to be any different. Such
enclosure may only be as little as enclosing an
area with a fence, as in a Game Park, which, while
they always try to provide ideal conditions, do
not always provide ideal environments.
Signs and Symptoms
- there may be none at all - the
parasite may be benign.
- a failure to thrive - decreased growth rate, or poor weight gain.
- on-going diarrhoea, which may be only mild, but could be
- blood in the faeces - not always present - may be caused by other
diseases, e.g. typhoid.
- may be eggs in the faeces, but these are not always present.
- may be little fragments of muscle or intestinal lining in the
- great pain and shock.
suspected that recovered animals, like most
animals, are carriers of the disease, but this is
not necessarily a bad thing, as it stimulates
immunity in the next generation. Recovered animals
can, however, develop a recurrence of the disease.
such drugs currently available, such as the
sulfonamides, are purely prophylactic - that is,
they only help in its prevention, but once an
animal has developed coccidiosis, there is no drug
that will cure it. If a particular drug makes an
animal well again, it was probably not suffering
prophylactic drugs available act against the
asexual division by repressing the number of
of any use, prophylactic drugs must be used before
and during periods of change - it is of no use to
start them after changes to the animals’ lives.
sure of giving animals the best chance of
protection, they must be kept on the drugs all the
species differ in their ability to stimulate an
immune response in an animal.
they may reduce the total number of coccidia
present, circulating antibodies play only a minor
role in protecting an animal. Local immunoglobulin
A systems play some role in the lumen of the gut,
but the parasites can evade this. The main
reaction is cell-mediated in the gut wall.
Attenuating (changing their level of virulence by
weakening) parasites by the use of heat, cold and
radiation have not worked. Strains can be
attenuated successfully in chickens by passage
through chick embryos in eggs, but this is not
feasible in mammals.
best option to date appears to be to expose young
animals in the first few weeks of life to very low
levels of virulent oocysts - the egg stage of
Selection is being done to find a species of
coccidia in chickens which is precocious, that is,
has fewer generations, so that there is not as
much damage done in the gut. This would act as a
Eastern Greys are more prone to coccidiosis than
outbreaks can be triggered by overcrowding,
stresses caused by flooding, inclement weather,
shortage of feed, feed supplementation,
contamination of feed (on ground) with droppings.
Outbreaks in captivity can be precipitated by any
of the above stresses, or by strangers, changes to
feeding or routine, transporting or relocating,
confinement, lack of cleanliness or even by the
stress of loneliness or separation.
changes, no matter how minor, should be made
slowly and the strictest of hygiene standards must
be observed at all times - feed should never be
placed on the ground but in containers, to prevent
Animals must be observed vigilantly and
constantly to detect signs of stress.
not going to be easy to develop a vaccine against
coccidiosis. It is not going to be cheap and it
may not even be successful.”
F.E.G. Cox, Division of Life Sciences, Kings
International Journal of Parisitology. January
the Questions and Answers section, Dr. Carmichael
was joined by Michael O’Callaghan, Taxonomist,
also from the South Australian Research and
and Answers about Coccidiosis
How long do coccidia last in the ground?
They may last for years. Other organisms which
evolved in Australia are very tough, so coccidia
probably are too. Oocytes can be dust-borne once
they sporulate and the faeces break down.
Unless conditions are just right in Nature, they
just lie there and build up. If animals are housed
in small enclosed areas over a long period,
oocysts are continually being built up.
If there are such a large number of coccidia, is
it reasonable to think that they mutate in
Species appear to remain consistent all over the
world. They may change, but this is more due to
selection, not actual mutation. They do not
mutate like the flu virus does in humans.
Coccidia fossils have been found on Pearson
Island which are the same form although they are
10,000 years old. There is no evidence of their
Does coccidiosis affect arboreal animals, such as
possums and should you always clean feed trays?
Yes, it affects both possums and platypus, but the
species involved are different to those involved
in macropods and we don’t have any evidence of
clinical disease. Exposure is on the ground,
when the animals come down to the ground or out
onto land. All feed and water containers should be
Can you explain how no Reds, Damas or Euros have
been affected, but Eastern Greys have? There
was no change in their diet or routine.
They may all have been exposed to the same
parasite, but the Eastern Greys could have been
more susceptible. It could also be that that
particular species was more dangerous to the
Much research was carried out on coccidiosis from
1912 to 1972. What of the future?
Australian poultry industry breeds 350,000,000
birds a year and has a turnover of $700,000,000.
The American industry even more. Despite
enormous financial investment, they still have not
been able to come up with a cure. It is hoped to
be able to select a precocious parasite and
introduce this as a living vaccine.
Can people get coccidiosis from macropods?
If coccidiosis is host specific, is there one that
affects both poultry and macropods?
No poultry coccidia affects macropods.
Would soil differences, such as clay or sand, have
any correlation on coccidia survival?
Coccidia have very good survival mechanisms, so it
is unlikely, although moisture and overall season
moisture may have some influence. Fossils found
have proved they can survive over eons. Disease
usually occurs when a large number of coccidia
sporulate. If they are swallowed before they
sporulate, they are harmless.
Would living in a hot, sandy area with a low
rainfall make a difference?
much. Kangaroo coccidia evolved in hot, dry
conditions, so it is likely they are very tough,
although moisture and shade do help their
survival. There may be taxonomical differences
between species found in different areas as they
have found in other animal parasites.
you move animals to a new area, could that cause
Does fire destroy coccidia in the soil?
don’t know. I suspect that fire would go right
over the top of the coccidia which would be
insulated in the dung, so it may very well
If it is going to be a long time till anything is
developed, can we only work to reduce stress and
concentrate on hygiene?
Yes, this is all you can do. This is why we need
the research. We need to be able to recognise
exactly which species of parasites are responsible
for death and or disease.
Could we develop a test kit for coccidiosis?
Aspects of immunity can be measured already. In
the first week, there is a very high antibody
level, which is gone by week four - but with
coccidiosis in mammals and chickens, this doesn’t
work. Immunoglobulin A movement does not work
with coccidiosis. A test kit of any sort would
need a great deal of work done on it.
Would colostrum substitute help prevent
would be of considerable benefit in decreasing
other stresses and infections which may predispose
young animals to coccidia. Colostrum deficiency
is a common cause of many diseases in young
animals and a substitute is a good general immune
Christine Irving from Native Animal Network, who
is a qualified laboratory technician with many
years experience, stated that she and NAN’s
President, Dot Berris, have been working on the
subject for some five years now. Over the last
couple of years, she has been isolating,
identifying and documenting coccidia in faecal
specimens and has made the following findings over
- Red Kangaroos and Euros do not carry as many
species of coccidia in their droppings as do
Eastern Greys - Reds carry three species and Euros
carry only one.
- Reds and Euros carry the parasites without them being pathogenic
(causing clinical disease) to them. Disease only
occurs if the animals become overburdened with the
- the isolation of many species from Dot Berris’s yard, two of
which are pathogenic to Dot’s kangaroos.
Berris stated that she has found that the
immediate start of a high dose of Baycox as soon
as clinical disease is suspected, gradually
decreasing in dose, can help an animal survive.
Baycox is no good
once animals are symptomatic. She also said she has found that Gamma globulin
helps kangaroo joeys and Manfred Heide said he as
found this helps wombat joeys, also. She said she
has been investigating and experimenting with
various treatments for coccidiosis for 8 years.
feels it is vital to follow the rules:-
your animals well and watch them carefully.
- if you even suspect one is sick - get Baycox
into it in a high dose and fast.
- watch all your other animals extra carefully if
one of them becomes sick.
- do not ever feed them on the ground.
- be constantly vigilant and act quickly.
I had a highly infected youngster, with many
species of coccidia in its droppings, including
cat coccidia, which I treated with Baycox. Its
droppings were clear from coccidia on the last
faecal testing. Could you give a reason?
Baycox is “relatively” new and interferes with the
sporozoite stage. By giving it at such an early
stage, it could well be helping animals survive.
Is coccidia self-limiting.
Is coccidia part of the normal bowel flora?
How would we go about developing a register for
all kangaroos who die from coccidiosis?
They would need to be clinically diagnosed, by
autopsy. Ideally, every vet, would have to
submit a sample of their gut for analysis.
Coccidiosis seems to have been only more commonly
diagnosed in the last ten years. Would there be
any tie up between this and climate changes?
doubt it. I think there is just much more
awareness now. There was much good pathology
work done in 1927.
animals are treated with Baycox, will they build
up a resistance?
Coccidia have shown resistance to other drugs
already, although this is more common in the
poultry industry where there is high dose,
on-going drug use. There is not a high concern
that it will happen with coccidia in macropods.
it correct that most kangaroos seem to die of it
at about 18 to 20 months?
am not aware of this.
Is there likely to be the same level of immunity
to coccidia in wild and hand-raised animals?
don’t know. To find out if orphaned and
hand-reared animals have similar problems to wild
ones, they would have to be compared at maturity.
You may be able to look into this, as you’ve
said you already take surplus bucks and joeys from
Dot’s actions are a perfect example of prompt and
good action in animal care. If you have a new
animal coming in, you would be wise to isolate it,
as you do not know what it carries. Kangaroos and
Euros may be carriers, but may not be affected by
the parasites themselves, maybe because they come
from hotter, drier areas. It is vital that you
know your animals well and can detect small
changes in them and act accordingly.
much admire the work that Christine Irving is
doing, as she is in the field and not in a
laboratory and can do a lot of valuable work. I
would suggest that we all give her our full
support in her research.