BLOOD PARASITE SEEN IN YOUNG EASTERN GREY KANGAROOS
Compiled by Cheryl Dooley January 2003
The purpose of this paper is:
To communicate information about a blood parasite, identified in macropods, to carers, vets and all those interested in the care and rehabilitation of macropods.
To ask for cooperation from all wildlife groups to enable further work to identify the parasite and study cases of the disease as a basis for its control and thereafter its causes and possible cures.
This paper continues investigative work started in 1994. I have attached a copy of a paper presented at the Australian Veterinary Association Pathology Meeting in 1996 by the NSW Agriculture, Regional Veterinary Laboratory at Wollongbar (RVL Wollongbar) and a paper written in July 1998 by Liz Drinkwater (FAWNA). These papers could be read first as a background to my paper. Many things have changed since these papers were written, and things will continue to change. I expect to update this paper as this work continues.
I am not a veterinarian, and the information provided here should not be seen as scientifically proven nor should it replace advice from your own vet. I am a wildlife carer of some 2.5 years and a member of Coffs Harbour WIRES. I have provided footnotes to show the sources of documented information wherever possible, and I have worked to sort the suspected from the confirmed, and the anecdotal from the clearly tested and documented. This in no way reflects on those people who have provided information that is anecdotal, indeed at times it is all we have as the basis to develop theories. We need to use words such as "theory" and "could" and "may" , and should avoid passing on information that we do not know to be entirely proven, as "this is the way it definitely is" .
The other constant danger when information passes from person to person in an ad-hoc way is that old story that: "Send reinforcements we're going to advance" becomes: "Send three and four pence we're going to a dance" . When I say, "confirmed" in this paper please be assured that this means confirmed by blood tests and/or necropsy (postmortem examination).
Some of the information in this paper may challenge things that some carers have come to believe as "facts" . This simply shows that "facts" often change as information grows and that any changes to treatment today should in no way suggest we did the wrong thing in the past. The treatment of native animals is far from being an exact science and we are all learning together. Every person I have spoken to has wanted only the best for the animals in their care and no one should take anything in this document as personal criticism. I trust this paper will be of some benefit to you, and that it may inspire you to become a part of the program to investigate this disease further.What to look for:
The parasite infects and causes destruction (haemolysis) of the red cells
circulating in the blood. The result is a
. Necropsies have shown that the parasite localises in massive numbers in
blood vessels of the kidney and brain.
White or light pink gums and conjunctival membranes of the eyes.
Fluid build up in lungs and thoracic and abdominal cavities.
Tendency to bleed from tick attachment sites or veins after blood sampling.
Increased consumption of water and frequent urination (polydipsia and polyuria).
Loss of appetite (though we have one confirmed case where eating remained normal).
Misshapen and desiccated pellets.
Many of these signs occur in other diseases, so it is desirable to seek veterinary advice for diagnosis before treatment is given. Coccidiosis in macropods also causes anaemia, due to blood loss into the gut. In blood loss anaemia a blood sample will have a low number of red cells (anaemia) and a low concentration of plasma protein. In the haemolytic anaemia produced by the blood parasite there is anaemia but also a normal concentration of blood plasma protein. A blood sample collected in EDTA anticoagulant is useful for differentiating these two types of anaemia.
Of course each animal will react individually and there are probably a wide range of signs possible. Could this parasite be the reason for other "unexplained" deaths where animals have simply "faded away"?Prognosis:
At initial examination, it is difficult to determine whether an animal will live or die. Animals with a slower onset of the disease seem to have a better chance of survival than those that go down rapidly. (That was certainly seen in my two cases and has been the case for others.) It would seem that in the cases of a slower onset, the animal's bone marrow has a chance to react to the parasite and start to fight back. These animals also respond to the use of Imizol (see treatment section). Where the onset is fast, the immune system does not appear to be able to cope and Imizol may also not be affective. (Again I saw this in one of my joeys).
The parasite seems to leave them vulnerable to internal bleeding and to spontaneous blood vessel eruption. If a bleed occurs in the brain the joey may go a bit "lop-sided" or develop eye ticks/movements. Generally if this happens the animal cannot be saved. This happened to one of my joeys, she was found going round in circles. Within seconds she was down and lost all coordination and had to be euthanased.
It is important that carers record their cases in a standard format (see Macropod Examination sheet) so that we can develop more reliable information on prognosis and likely response to treatment.Which animals are affected and why?
All confirmed cases so far have been from northern and mid-north coast NSW. This localisation of cases may simply reflect a greater awareness of the disease in this area.
Not all kangaroos in a group seem to be affected. In one group of 8, only 3 were affected and the first to die was the healthiest of the group. The majority of cases seem to be from 5kg upwards, though one anecdotal case is suspected in a 2kg joey. Both males and females are affected. Both sick and healthy animals are affected.
Stress is always a concern in reducing an animals immunity however in several cases stress does not appear to have been a factor eg 3 x 12kg males that had been in one location for six months i.e. they had not been moved or changed handlers and nothing else significant appears to have happened. Cases also seem to appear at varied times of the year. With confirmed cases occurring in all seasons. There is a theory that perhaps more cases occur during drier years but this cannot be proven at this point.
There are only a couple of reports of this parasite in wild eastern greys, however they are not confirmed cases.
In general outbreaks seem to be confined to hand-reared orphans and in "wild" release areas: i.e. not in suburban situations.Are other macropods affected?
The disease has been seen almost exclusively in eastern grey kangaroos. There have been several suspected cases reported in redneck wallabies with blood analysis confirming anaemia though unable to specify this particular parasite without further testing. In several of these cases Vets diagnosed a blood parasite and treated accordingly. In 2002, two cases were suspected in swamp wallabies. Necropsy (post mortem) confirmation is required to demonstrate the organism in these other macropod species.
Could we be assisting this cross over of this parasite into other species by mixing species at our release sites? There is not enough information available to determine this.Detecting the parasite:
This is difficult in the live animal. Only a very small percentage of red cells in the peripheral blood (rarely more than 5%) contain the parasite even in severely affected animals. The parasite is concentrated mainly in the blood vessels of the brain and kidney of affected animals. Therefore a negative blood examination result from an animal with a haemolytic anaemia does not rule out the disease.
It is certainly worthwhile making smears of blood taken from the tip of the tail or ears and sending these smears to a laboratory for staining and examination under a microscope to try and detect the parasite.
A blood sample in EDTA anticoagulant is useful for two reasons:
Testing for severity of anaemia and plasma protein concentration.
Remainder held frozen for research to identify the parasite. (See section: "What can you do to help?")
One thing that sets this parasite apart is that it causes a haemalytic anemia, i.e. only the red blood cells are affected, and the plasma protein concentration is normal. (This is not the case in all anaemias eg; in anaemia related to coccidiosis plasma protein is affected). When red blood cells are broken down from plasma they usually constitute 30% of the total, 20% is considered low and in these cases animals are seen with as low as 10%.What is this parasite?
The following brief layman's guide to microbes lists them from largest to smallest:
Helminth parasites (eg worms).
Protozoan parasites (eg coccidia, and many blood parasites).
The protozoa are Eurcaryotes and have 18S ribosomal DNA. Preliminary electron microscopic examination of the parasite in affected Eastern Grey kangaroos could not confirm its identity as a Eucaryote. It is therefore possible that it belongs to another group of microbes such as the Rickettsia (Prokaryotes with 16S ribosomal DNA). To investigate this question of the identity of the parasites we need to collect and freeze samples of blood in EDTA anticoagulant from all cases.How is the parasite spread?
It is not known how this blood parasite spreads. It could be one of many biting insects including ticks, flies or even mosquitoes. Scientists I have questioned seem to favour ticks as the most likely vector. As an example, with the Babesia sp. blood parasites, (two types that cause cattle tick fever), the parasite is taken from infected cattle when female ticks engorge with blood and transfer the parasite through tick eggs to the larvae. The disease spreads when larval ticks attach to a new host, infecting it by injecting saliva carrying the organisms. A larval tick is the tiniest tick seen and it is doubtful whether a tick of this size would even be detected on some animals.
In the areas in NSW where this parasite has been confirmed, Boophilus microplus (the cattle tick) does not exist, (or at least it should not), and cattle ticks do not attach to native animals. The common ticks seen are Haemaphysalis longicornis (the bush tick, also known as the grass or bottle tick), which make up about 90% of ticks in NSW, and Ixodes holocyclus (the paralysis tick, also known as the dog, scrub and shell-back tick), which make up about 10%. I have not included detailed information about ticks in this paper, however I would encourage all carers to gain further information via websites (eg http://medent.usyd.edu.au is a website created by the joint work of the University of Sydney and Westmead Hospital, or from relevant authorities eg. NSW Agriculture, so they can clearly identify the different species of common ticks.Could young joeys in the wild be immune?
Let me use cattle tick fever as an example, (and again I would stress that we are not dealing with one of the 3 cattle tick fevers here, I simply use it as an example where we do know how the organism works). Calves younger than nine months do not become sick when infected, but do develop immunity to the organisms. Complete eradication of cattle tick is not recommended because some ticks are needed to reinfest cattle continually to help them develop an immunity to the diseases carried by the ticks. Calves from immune mothers receive temporary protection (maternal antibody) from the colostrums which prevents babesiosis. This protection lasts about 3 months and, in most cases, is followed by an age resistance, which lasts until the animals are about nine months old. Calves exposed to infection when the maternal or age resistance is high rarely show clinical symptoms but develop a solid, long-lasting immunity. It is therefore possible to have both babesia organisms and cattle ticks present on a property without animal losses or clinical disease. This situation is known as endemic stability.
At this point we don't know whether this is true of macropods as well, however as previously stated there are no confirmed cases of wild kangaroos; only suspected cases. Also this problem does not seem to happen to carers of young joeys in what we might call "suburbia"; it only manifests itself in "wild" areas.
In my own situation, I have a mob of some twenty plus wild eastern grey kangaroos that move freely around my house and property. They have come into close contact with the two affected joeys we have had recently and yet I have seen no evidence of the problem in the wild mob. There are also cases where only a few joeys of those in care developed the problem - could it be the others had developed an immunity somewhere in their development - either coming into care at a later age, or having gained some bites whilst in care? I also had a red neck wallaby joey undergoing release that also had contact with the two eastern grey joeys. He too showed no signs of the illness, however he had been exposed to many ticks and flat flies (and probably mosquitoes) for a calendar month before their arrival. Could he have built immunity prior to their arrival?
RVL Wollongbar have seen this parasite in the kidney of a wild kangaroo (brought in for testing for another reason). This animal showed no signs of anaemia so it is possible that, as is the case with coccidia, animals carry this parasite but have a natural immunity to it.
This then raises the question - could this problem be as a result of joeys being raised in care, not being exposed to the range and number of ticks and other biting insects that would be a normal part of their wild world? This question is also raised in the report by Cook, Fraser and Hartley and the Liz Drinkwater Paper.
Although it is natural for carers to want to protect joeys from such biting insects, perhaps some exposure to bites at an early age is as necessary to develop immunities, as dirt is in developing good gut flora?
How would we solve this problem, given we need our suburban carers? One suggestion may be to cut grasses and bushes from the wild and to take them into suburban carers to enable exposure. (Ticks are common in ground and shrub layers; contrary to popular belief ticks do not fall out of trees). This may not solve the problem though given such things as flat flies seem to be a very rare event in suburbia and may not travel on branches or in grasses. Also what degree of exposure is needed? Is one tick enough? Probably not.
It is easy to forget that we should be thinking and acting like eastern grey kangaroos rather than letting our own motherly instincts take over - this could be fatal to our charges, (eg: I have heard of carers who test milk warmth by popping the teat into their own mouths before popping it into the joeys mouth. This may be fine for human babies, but what diseases might we pass on to a kangaroo joey via our saliva)? In the same way too sterile an environment might set animals up for later failure. It is a sad fact that we often do not know what happens to our joeys once they are released but we must try to ensure they have the same chance as wild joeys and that may mean treating them like wild joeys and exposing them to wild elements from an early age.Treatment
Two things must always be considered when treating eastern grey kangaroos:
They have a lower body temperature than domestic animals. Kangaroos, like most marsupials, try to maintain their core body temperatures near 36ºC, slightly lower than most placental mammals.
They have a lower metabolism than domestic animals. As a general characteristic, kangaroos have basal metabolic rates that are about 70% of those of comparable placental mammals.
This means there can be the risk of prescribing too much medication, which could do immediate or long-term damage.
The following are treatments being used by four different groups who have seen this infection.Group 1 -
Gives one shot of Imizol sub-cutaneously (no specific location for shot), using the dosage rate of 0.12ml per 5kg (0.024ml per kg). Vets sometimes also prescribe antibiotics if there are signs of fluid build-ups or chest infections. They keep fluids up, using Lectade or by administering Hartmann's sub-cutaneously. They use pentavite with iron or Incremin. Prior to the use of Imizol this group managed to save about half of the joeys that suffered from this problem using various treatments including vitamin supplements such as pentavite, cellvite E and also antibiotics.Group 2 -
Two shots of Imizol. One shot and then a second given 24 hours later. Dosage rate 0.1ml per 2 kg (0.05ml per 1kg). Shot is given in the back of the neck. Antibiotics are given on the first and third days into the muscle. Anabolic steroids were given to one animal, as it was very debilitated. They sometimes also use a natural tonic (similar to Pentavite) and Vytrate, (similar to Lectade), to keep fluids up.Group 3 -
Pentavite with iron, Incremin, keep them well fed and watered. This group has lost 2 out of 5 joeys in the past 10 years that have presented with the problem.Group 4 -
Two shots of Imizol, one day one, the second one week later. Dosage rate is 0.2ml per 4kg (0.05ml per kg). Given sub-cutaneously, no specific location.The use of Imizol
When this drug was initially used, the main concern was its possible toxic effect on macropods. Given the number of animals that have now been treated with the drug, and in varying amounts, it could probably be safely concluded that it does no short-term damage to the animal being treated. (Group 2 has seen side effects of localized swelling and a scab that falls off).
In the 3 groups using it, all believe that a majority of the animals recover with the use of Imizol, though some confirmed cases did die and a greater number of cases are "suspected" rather than confirmed, and so some recovering animals may not have had the parasite. As previously stated, those with a regenerative anaemia (even with haemocrits as low as 0.11 and 0.12 L/L) do seem to improve clinically with the use of Imizol. Anecdotally it would seem that those that are going to die usually do so within a few days and those that will recover respond to the Imizol within 24 hours.
A single dose sterilizes Babesia spp. infections and is effective, though less so against Anaplasma spp. Therefore if the drug is active against the kangaroo organism a single dose may be sufficient treatment. One Vet I discussed this with said in some cases where a second dose was given it appeared that the animal was probably going to recover anyway and that the second dose probably had little effect. This may be confirmed by the Department of Agriculture (WA), which states "Imidocarb (the active ingredient in Imizol) is highly effective for treating tick fever. However a single dose sterilises the bloodstream for up to 12 weeks, negating the development of immunity". This then raises the question of immunity in those cases which have survived. So far there have been no cases reported of second infections, however given surviving animals are released to the wild, not all animals can be tracked for the duration of their life. One Vet I spoke to felt if their immune systems have started to fight the problem then they should gain a degree of immunity despite the use of Imizol.
The Department of Primary Industry Queensland states the recommended dosage of Imizol when used for the treatment of vaccine reactions in cattle as follows:
For the two babesia strains - Imizol dose rate: 1ml/100kg (0.01ml/1kg) live weight (treatment). Imizol must be given under the skin, preferably in the neck. Depending on the volume given, it may cause some tissue damage and it is advisable to split the dose into two inoculations if it exceeds 5mls.
For anaplasma reactions and if using it as a short-term preventative - dose rate 2.5ml/100kg (0.025ml/1kg) live weight.
With regard to where the dose should be given, the scientific consensus seemed to be it probably doesn't matter where it is given but it should certainly be sub-cutaneous and not intravenous.
Because of the difficulty of obtaining Imizol in the affected area, sometimes it may have been used when passed its use by date. The manufacturers advice is that this should not happen. I have been unable to ascertain, at this point, what changes may occur in the product after it expires. There are drugs whose properties change post expiry and may create neurological problems. It is probably safest not to use Imizol past its use by date if possible.The use of Antibiotics
The use of antibiotics will not kill the parasite, but could be helpful if there are secondary problems such as fluid build-up (oedema) within the lungs, which can predispose to pneumonia. Antibiotic use is the same in animals as in humans in that most may have some toxic effects, and over use may reduce future resistance. Whether antibiotics should be given sub-cutaneously or intra-muscularly depends on the type of antibiotic used.Is Imizol the only drug?
At this point it would seem so. In some of my research I came across reference to quinuronium sulphate (Ludobal). This drug is an old babesiacide developed in the 1930s and no longer available. It is, however, very stable and old stock of this product has still worked for cattle tick fever.Recovery:
May takes two weeks or longer, with the animal slowly gaining energy. Meanwhile, their heart may be under strain, as it is working so much harder to pump the blood around. Rest with plenty of fluids and food is recommended. Some animals are so lethargic that they cannot move themselves out of the sun and this obviously needs to be monitored.Preventative Measures:
Imizol is only used as a preventative on cattle as a temporary measure (eg the cattle tick vaccine can create problems for pregnant cows and therefore Imizol may be used as a temporary measure, but does wear off after a short time.) It is registered with the claim of providing protection for 4 weeks. The conclusion seems to be that it should only be given to macropods as a treatment and not as a preventative.Where to from here?
There is a need to:
Identify the organism (from DNA studies using EDTA blood samples collected from cases and frozen for future testing. For this work we need to collect samples from a substantial number of cases.
Collect clinical and treatment data in a standard format for ease of collation.
Sometimes poor documentation of cases by carers.
Information not shared between wildlife groups.
Unclear definition of cases (anecdotal versus confirmed cases). It is important to have laboratory tests done to support the diagnosis and be sure of what the problem is. If we are tempted to see this parasite as the possible cause of all ills and Imizol as the cure we run the risk of losing animals to other diseases as well as being unable to come to scientific conclusions.
Lack of funding for research for native animals.
When you have a LIVE suspected case you are encouraged to collect the following information in a standardised format and samples for diagnosis and research:
Air-dried blood smears from tip of tail or ear (for staining and detection of the organism).
EDTA blood sample A blood sample in EDTA anticoagulant is useful for two reasons:
a): Test immediately to assess severity of anaemia and plasma protein concentration
b): Freeze remainder for research to identify the organism.
Collect any ticks from affected animals and hold them in a 70% by volume alcohol mix. (This can be pure alcohol, or even metholated spirits can be used, but in a 70% alcohol/30%water mix). In a clean jar. These do not require freezing.
Complete the Macropod Exam Sheet attached, so we can gain consistent information from all sources.
Arrange for these frozen EDTA blood samples, ticks in 70% alcohol, and Macropod Exam Sheets and any other details to be sent to or collected by:
1647 Orara Way
Glenreagh NSW 2450
Ph: (02) 6654 3793
When you have a DEAD suspected case , you are encouraged to arrange necropsy (a postmortem examination).
Bodies for necropsy should be chilled NOT FROZEN (i.e. use the fridge not the freezer). The approximate cost is $100 (current January 2003). Post mortem examination can be by a local veterinarian who can collect specimens to send to the laboratory, (these should include fresh and formalin-fixed kidney and brain at minimum. Fresh faeces and a range of other formalin-fixed tissues heart, lung, liver, intestines, bone marrow should also be collected to diagnose other possible diseases such as coccidiosis), or the chilled carcass can be sent directly to the laboratory, eg:
NSW Agriculture Regional Veterinary Laboratory
Bruxner Highway. Wollongbar NSW 2477
Ph: (02) 6626 1261
Fax: (02) 6626 1276
Send all information to Cheryl Dooley (contact details above). This will enable us to have a central contact point so that this paper can be updated.
Distribute this paper to all known macropod carers and vets who may be involved in macropod care.