PROTOZOAN INFECTION SEEN IN
YOUNG EASTERN GREY KANGAROOS
Compiled by Liz Drinkwater July 1998
In June 1998 an autopsy was performed on an eastern grey kangaroo which had been in my care for a few weeks. (female, 4kg) The following is the conclusion printed on the Laboratory Report from the NSW Agriculture Regional Vet Lab at Wollongbar NSW.
Death and anaemia due to protozoan infection. This protozoon has been seen in North Coast eastern grey kangaroo joeys, most commonly soon after release. Some anaemic animals have responded to treatment with Imizol. The specific identity is unknown. We are collaborating with molecular geneticists at UTS to try and determine its phylogeny. Please contact us if you see further cases.
I spoke with the pathologist who performed the autopsy and with carers around the Coffs Harbour, Bellingen and Clarence Valley areas who have experienced this problem and successfully treated infected animals. All of these people have been very helpful.
The infection is described as a new disease and it is thought that ticks carry the protozoon. Scientists at Wollongbar are co-ordinating studies to confirm or deny this. A molecular biologist at UTS is working to isolate the DNA; other scientists in Queensland are testing ticks from areas where macropods died.
While I hope you never see this problem, this information is being sent to you in case you do - it might help with diagnosis and cure. Alternatively, we have a chance to help identify this disease by having autopsies conducted on eastern greys you suspect may have contracted this infection.
Most macropod carers have heard of sudden and/or unexplainable deaths in animals in our care. Who knows? This may be a chance to alter that unhappy situation.THE DISEASE
This protozoon was first seen 4 years ago. Since then 7 or 8 cases have been seen at Wollongbar, from the Coffs Harbour and McLean areas. Carers noticed that affected animals bled, and continued to bleed after ticks were removed. (This was not noticed in the joey autopsied.) It appears that most of the animals that have died have been around 5kg. However, the infection has also been seen in animals over 15kg.
The protozoon is a single-celled organism. It's seen in small numbers of red blood cells, larger numbers in the endothelial cells - the parasite appears to multiply in these areas, particularly the brain and kidney, leading to death. In the earlier stages of infestation it destroys red blood cells causing anaemia. Destruction of the red cells is probably an important part of the life cycle of the protozoa.
|Endothelium: the tissue which lines blood vessels, lymphatics, serous cavities and the like - Macquarie Dictionary|
Most protozoons are host-specific and it is assumed this one is also - so cannot be transferred to humans or other species.It is unlikely that this problem is heading south. It is thought the protozoon is widespread, but has not been recognised before.CATTLE TICK FEVER
Some carers have had success when using Imizol as part of the treatment. This is a drug which is used in Queensland to treat cattle tick fever. This drug isn't used in the Macleay area because we don't have cattle tick fever here.
Calves are born with a natural immunity to tick fever protozoa. This immunity is age-related - around 12 months after birth the immunity wanes and the cattle become susceptible to the tick fever. If they are exposed to protozoan infected ticks while protected by the age immunity they develop protective antibodies. If they are removed from a tick-free area at the age of (say) 18 months and taken to a site with protozoan infected ticks they will probably get tick fever. The kangaroo protozoan may behave similarly but this remains to be confirmed. Cattle are immune forever once they have recovered from cattle tick fever. It's expected the same will be true for kangaroos.PREVENTION and DIAGNOSIS
There are no preventative measures carers can take for the joeys except perhaps ensuring animals are exposed to ticks from an early age. However, the following may help with diagnosis:
The joey goes flat: stops exercising, loses some interest in food. In the case of the joey autopsied increased water intake was also noticed. The mucous membranes become pale (gums, mouth, eyelids). In some cases carers have simply thought the animal was off colour. Often the first sign was when the joey didn't want its bottle.
Bleeding can occur when ticks are removed, sometimes the bleeding (which can be pinkish) continues for some time. If there's no blood in the faeces (which may indicate coccidia) there's a chance this protozoon may be the problem. If these symptoms are present, take the joey to your vet testing and diagnosis of the presence and extent of anaemia is straightforward. Keep the joey warm, don't encourage exercise.
(I'm passing on information here, not giving advice check with your own vet.)
A blood sample can be sent to Wollongbar to test for the presence of the protozoon. This is the only way to contain the protozoon infection but probably does not detect all infected animals.
It's important to notice problems early. It appears kangaroos can become profoundly anaemic quickly. The animal becomes badly compromised. It's not getting enough oxygen to vital organs, and it's unlikely to survive. If the problem can be caught very early we have a chance to help the animal survive.WHAT TO TREAT WITH?
This information is not intended to replace advice from your own vet. It is being passed on from carers who have had both success and failure with treating animals known and/or suspected to have contracted the protozoon infection.
Treatment has been to both counter the effects of anaemia and to kill the parasite. Carers have had success with Cellvite E injections (vitamin E) or with Pentavite syrup with iron. There has been improvement with these vitamins (particularly Cellvite E) even before Imizol was added to the treatment. Antibiotics are generally used as well, and often an anabolic steroid. (Vectrin and endomycin have been used but there is no antibiotic of choice, talk to your vet).
Imizol seems to be the drug of choice against the protozoon infection and in one area is routinely used as part of treatment now.
Dosage for Imizol? A 5.5kg joey was treated with .2ml each day for two days, plus an anabolic steroid plus vibravet. It survived.
The treatment with vitamins and antibiotics is probably viewed as supportive treatment it may help prevent secondary infections, which the animals are more prone to when they are anaemic and their system is compromised. If the parasite is invading the red blood cells, this treatment may not be much use. However, Imizol seems to eliminate the parasite so if the parasite is being knocked back while red blood cells are being helped we're on the right track. Otherwise, the parasite is increasing while the red cells are decreasing and the animal can only go down hill.OTHER INFORMATION FROM CARERS
Not all carers are convinced that ticks cause this problem, because animals have had the symptoms outside tick season. Animals bled when ticks were removed. Sometimes the bleeding was so extreme animals were given vitamin K (to help with coagulation). A couple had abdominal ruptures. The joey that died in my care didn't have a problem with bleeding ticks were never seen on her.
(It's not actually ticks that cause the problem; it's the protozoon which infected ticks carry.) It is important to notice any symptoms early there's a much greater chance of successful treatment. Some animals have had a slow onset of symptoms; others have been well one day and dead the next. This may relate to the fact that anaemia can become profound so quickly.
One carer hasn't seen this problem for a couple of years. They went through a period without eastern greys (except pouch young) and think the cycle has been broken they view the problem as seasonal. Another carer hasn't seen the problem since last summer. The latest reported case was October 1997, and that co-ordinator thinks the problem may be passing.
More details are coming to me which should provide information on how many joeys had this infection, how many survived treatment. I'll pass it on when it arrives, but in the meanwhile I thought this information might help anyway.WHAT NEXT?
With any luck you'll read this and remember it but never see it affect any of the animals in your care. If an eastern grey dies from no apparent cause, or with symptoms as described earlier, if you can arrange for your vet to send the complete animal to Wollongbar it can only help to establish the extent of this disease. If possible, please also send fresh blood samples.
It's quite important to send the complete animal the disease is still
new, so they are examining a wide range of tissues. In the meanwhile, if you
have any copies of autopsy reports for eastern greys, particularly those where
the animal was anaemic or had signs as described above, will you please send
1647 Orara Way
Glenreagh NSW 2450
Ph: (02) 6654 3793
I believe it's important that we keep up to date with this and other information which should help us to provide a good level of care for the animals. I'll send you updates if I receive any more news.
If you come across this problem with eastern greys will you please make sure all co-ordinators are aware of it so they can keep the members in their areas informed. I would appreciate receiving any information you have, especially any that includes details of successful treatment.
This episode highlights the benefits of keeping records and spreading information related to care and treatment around. If you have anything you think other carers might benefit from receiving (or more specifically, the animals in their care might benefit from) will you please distribute it. If you prefer, I'm happy for you to send it to me and I'll distribute it with anything else I might receive.
This is not intended to be a scientific document, or advice on how to diagnose and treat. As mentioned before, the intent is simply to pass on what I have found out. Your own vet needs to be included in any diagnosis or treatment.