Rat Rescue
:: Degenerative
Rat Disease
Degenerative Rat Disease
Results of questionnaires concerning degenerative rat disease
by Sally Clark
In the past few years three of my rats died from a degenerative
disease that appears to affect the brain and neurological system.
After writing an article in Pro-Rat-A I realised other people
had lost rats with the same symptoms. I developed a questionnaire
for owners of affected rats to fill in, in an attempt to find
out more about it.
From the start it was clear that the symptoms the rats were
showing could apply to more than one disease. So to be included
in this survey the rats had to show symptoms in at least two
out of three categories covering the rats’ awareness of their
environment, their ability to eat and their ability to move
and balance. This eliminated rats for example with spinal degeneration.
Rats with this condition found it increasingly difficult to
move around but didn’t score in the other two categories.
This gave me 54 questionnaires to analyse. There turned out
to be an exactly equal number of bucks and does aged between
7 months and 3 years when they died. In the majority (46%) the
symptoms increased in severity over a few weeks but for some
it only took days or even hours, the average length of the illness
was around a month. 4 does survived.
| % Of Rats Showing Symptom |
Symptom |
| 92.5% |
Lethargy |
| 92.5% |
Inability to climb |
| 85% |
Unable to hold food in front paws |
| 83% |
Balance problems & tendency to fall off objects |
| 81.5% |
Falling over whilst grooming |
| 79.5% |
Becoming progressively more unaware/unconcerned about
environment |
| 79.5% |
Unable to eat solid food |
| 74% |
Good appetite but problems eating |
| Table 1 |
Whilst it might be expected that a rat may show many of these
symptoms when it is in a collapsed state at the end of a fatal
or serious illness, in the diseases I was looking at these symptoms
often appeared in the early stages when the rat looked healthy
in ever other way.
Problems With Feeding
(74%) of rats kept a good appetite during their illness but
had increasing problems feeding. The most obvious symptom was
that they struggled and eventually were unable to pick up and
hold food in their front paws. Various suggestions have been
put forward as to why this happens.
The rat’s back legs and back are too weak for it to sit up
and hold it’s food. Although the rats did have problems with
their back legs, I’ve seen rats nearly paralysed in their back
legs from spinal degeneration still manage to find ways of holding
food in their front paws.
The rat’s front legs are rigid so the rat is unable to bend
them to get the food to it’s mouth.
This is a symptom which has been connected to pituitary tumours,
but in my survey only 18.5% of rats showed it. Even in those
that did, it was often towards the end of the illness and they’d
had problems feeding with their front paws from the start.
The rat can’t coordinate the paws to hold the food or feels
pain, numbness or weakness in the front legs.
Whilst it’s difficult to know exactly what the rat feels this
could be possible. Certainly the rats seemed to lose their ability
or strength to grip with the front and back paws and this was
the reason they couldn’t climb, tending to slide down the bars
of their cage or down their owners’ front if they tried to climb
onto a shoulder.
In 4 instances where the symptoms came on very quickly the
rats’ front paws knuckled over when they moved as they pushed
themselves along with their back feet, but often owners commented
that even though they couldn’t feed the rats would still use
their paws to clean their faces and walk around.
As well as having problems holding their food many rats progressively
lost the ability to eat solid food, then lap and finally to
swallow.
Problems With Movement & Balance
Many owners commented that the rat’s way of moving changed,
they often appeared drunk or uncoordinated. As can be seen from
the table, falling over whilst grooming or falling off objects
featured for the majority of rats. 50% of rats were unable to
get to their feet at all towards the end of the illness.
Problems With Awareness
For many owners the most distressing symptoms their rats had
related to the fact that they became increasingly unaware and
unconcerned about what was going on around them. It was often
changes in behaviour that were the first symptoms to appear.
Whilst some rats became withdrawn others appeared bolder because
they lost their sense of danger, a few seemed to become claustrophobic
in their cages.
61% of rats would move around in a purposeless way. Owners
described their rats as moving like clockwork toys, if they
bumped into something they would try and keep walking, needing
the owner to pick them up and point them in another direction.
Some got stuck in objects or tangled in their bedding.
61% of rats also seemed to be blind or deaf or unable to smell
at times and 55.5% ceased to recognise or respond to their owners.
At the end stages of the disease a couple of owners reported
their rats squeaking out when touched as if they were startled,
frightened or in pain. What was surprising considering all these
neurological signs was that very few rats had seizures.
Possible Diagnosis’s
There are several diseases which could account for these many
and varied symptoms.
Pituitary Tumours
This was the most common diagnosis by both vets and owners and
could certainly account for many of the rats in this survey.
Pituitary tumours most commonly effect older does and indeed
16 does died at over 18 months old. However pituitary tumours
are considered to be far rarer in bucks and only likely to account
for elderly ones yet 27 bucks had died and 13 of those were
18 months old or younger.
Although many symptoms fitted the diagnosis of a pituitary
tumour very well, other symptoms which are expected to be noticed
with pituitary tumours were rarely seen. These included rigidity
of the legs with the rat unable to flex them, only (18.5%) and
walking in circles (31%).
A head tilt was only seen in a few rats and aggressiveness,
another sign sometimes seen with these tumours in only one.
Some owners reported a staring coat and weight loss, but an
equal number noticed the coat stayed in good condition and some
rats even increased in weight.
Other Brain Tumours
Of the other tumours of the brain, Astrocytomas of the brain
stem are considered the most common brain tumour in younger
rats. The symptoms seen could certainly be caused by this kind
of tumour, however without post mortem examinations it isn’t
possible to tell which, if any tumour is present.
Strokes
Older rats are most likely to get strokes and some of the symptoms
would overlap with those seen in the survey. Strokes are usually
sudden in onset and the body shows varying degrees of paralysis,
often on one side of the body. There can be improvement although
it may be painstakingly slow.
15% of rats showed one sided paralysis so strokes are a possibility.
The fact that in this survey usually the symptoms came on gradually
and didn’t improve and that a lot of younger rats were effected
means strokes couldn’t account for many of the rats.
Infections
An infection did look possible for a few of the rats. 4 rats
in one household came down with very acute symptoms within 24
hours of each other. They were all treated with antibiotics,
first Baytril and then the last surviving rat was switched to
a penicillin based antibiotic.
She seemed to recover but succumbed to pneumonia a few days
later. These rats were knuckling over on their front paws and
close to collapse from the start and it’s possible they had
a form of meningitis. A viral or bacterial infection could also
account for the 4 does who survived. Mycoplasma which is often
responsible for respiratory disease in rats and can cause inner
ear disease, although it can be treated the rat is often left
with a head tilt which one doe was.
Ivermectin
The symptoms of ivermectin toxicity are very similar to the
symptoms seen in these rats. 39% of the rats had been given
ivermectin to treat mites during their lifetime. However animals
that react to ivermectin usually do so within hours of being
dosed with it and only a few rats were dosed with it close to
the time they were ill. So far ivermectin has not been reported
to have a delayed or cumulative effect.
Common Factors
Some of the questions on the survey were to see if rats affected
by symptoms had anything in common. The most significant similarities
between the rats were the age at which they died and where they
originally came from.
Age Of Affected Rats
For does these illnesses were more common in either old age
or at least over 18 months old, only 6 died younger. However
just under half the bucks died at under 18 months. What illness
these young bucks had is far more difficult to explain.
Source Of Affected Rats
As can be seen from Table 2 rats the majority of rats showing
these symptoms came from pet shops. In fact in the young rats
aged 18 months and under only one came from a breeder. If you
consider that many of the rescued rats may have originally come
from pet shops and the homebred rats may have had parents who
also came from there, pet shops are accounting for most of the
rats.
Although I had replies from owners who had bought their rats
from breeders. I had very little response from breeders themselves,
so these figures may not be completely accurate. However of
the breeders I spoke to, the opinion was that they occasionally
saw this problem in elderly rats and this was backed up by the
survey.
| Source of Rats |
Percentage |
| Pet Shop |
59% |
| Rescue |
16.5% |
| Breeder |
13% |
| Home Bred* |
9% |
| Laboratory |
5% |
| *Homebred – the rat was bred by the owner
who breeds the occasional or accidental litter but doesn’t
breed to show. |
| Table 2 |
There could be an inherited susceptibility to this disease.
There are strains of laboratory rat which have been deliberately
bred to be more susceptible to pituitary tumours, and it would
be easy to accidentally breed in a weakness in pet rats by breeding
for numbers rather than sound health. Rodent farms who stock
many of the pet shops have no incentive to breed healthy and
long lived rats.
In fact they are unaware of the fate of their rats once they’ve
left them. They also may not be careful about how inbred their
rats are. Most owners were unable to find out what had happened
to other members of their rat’s family but 5 owners did report
that siblings or mothers had died of the same disease.
The early environment the rats were in could also have contributed
to their susceptibility to this disease. It could well be that
it takes a combination of factors to trigger these problems.
No other significant similarities showed up between the rats.
They tended to be fed one of the commercial rat or rabbit mixes
along with fresh food. Their bedding was usually paper based
or shavings.
The rat’s colour and markings doesn’t appear to be significant
either, most colours were represented, although some of this
data was difficult to interpret because not all owners used
the standard names of colours and markings to describe their
rats.
Probably one of the most common illnesses rats get is respiratory
infections. Within the survey 37% of rats had had respiratory
problems at some point in their life. Only 9% of the does had
had mammary tumours removed which is a low number, but some
of the does in the survey were quite young and the chances of
mammary tumours increase as does get older. Of the drugs given
prior to the illness, 33% had had Baytril which is the most
usual antibiotic to be given to rats and 20% had had an anaesthetic.
Treatment
Not knowing exactly what is wrong with these rats makes them
difficult to help. Just under half the vets consulted thought
it could be a brain/ pituitary tumour. Other diagnosis’s were
inner ear infections or strokes but one poor rat was put under
the cold tap by the vet as she thought he had heatstroke. The
most common treatment was Baytril and steroids or just steroids.
This sometimes improved the rats symptoms but only for a very
short time, usually days.
It is unlikely to do any harm to try these two drugs as early
on in the illness as possible if you have an affected rat. They
may ease some of the symptoms for a short time. One rat also
seemed more comfortable on the painkiller Meloxicam (Metacam).
If you suspect a bacterial infection and Baytril isn’t effective
it may be worth switching to a different antibiotic.
All the owners had tried hard to find foods their rats could
manage to eat. It was also necessary as the rats became more
unaware of their environment to monitor them closely as there
were reports of rats falling off objects, or getting stuck or
tangled in their cages sometimes fatally.
Apart from 4 rats who recovered all the rats were either euthanased
or died naturally. Some rats were obviously suffering whilst
with others it was more difficult to tell because they became
so oblivious to everything they didn’t look distressed. My own
bucks came into this category and died in their sleep. However
since doing this research I would favour euthanasia as the neurological
symptoms are difficult to interpret. Whilst it’s easy to tell
if a rat is distressed with the symptoms of something like respiratory
disease. It’s very hard to tell if they are suffering with head
pain or whether the way they are experiencing the world has
become distressing.
Prevention
Clearly a lot more needs to be known about these diseases before
we will know how to prevent them occurring. However from the
research I did three general points emerged.
Breeding
With such a high proportion of affected rats, particularly the
ones who died young coming from pet shops. It would be advisable
to buy from a breeder who keeps good health records of their
stock and keeps their own rats for their full life span.
If you do have an affected rat from a breeder it is probably
worth letting them know, however don’t automatically blame the
breeder. Only if a breeder starts to have several rats from
one family or strain affected, especially if they die young
would they need to be suspicious of an hereditary condition.
Weight
In laboratory rats it has been repeatedly shown that overweight
animals are more likely to develop tumours and pituitary tumours
develop slower on a restricted diet. Whilst comparisons can’t
always be made between pet and lab rats and very few of the
rats in the questionnaire were reported to be overweight. It
seems sensible to try and keep pet rats at their correct weight
as there are so many health problems associated with obesity.
Ivermectin
It’s worth being cautious in the use of ivermectin as it’s very
easy to overdose an animal the size of a rat. There is also
a much higher risk of toxicity if the rat is unhealthy or on
any other medication.
These diseases are clearly distressing for both the rats and
their owners trying to help them. My hope in doing this survey
is that the more these conditions are discussed, the more clues
can be found as to what they are and how to treat and prevent
them. Whilst the most common diagnosis is a pituitary tumour,
because post mortems are rarely done there is often little evidence
as to whether this is the correct diagnosis.
To give useful information a post mortem needs to be done by
a specialist who is familiar with examining rats as opposed
to other species like dogs and cats. This can be expensive.
The survey brought to light that there are a number of bucks
suffering from this problem at 18 months old or younger and
it is not known exactly which disease they are suffering from.
The NFRS has a fund for pathology investigations into unidentified
diseases, and is willing to arrange and pay the cost of post
mortems on bucks showing these symptoms who are 18 months old
or younger, if they are owned by NFRS members. If you are unfortunate
enough to have a buck affected in this way and are willing for
a post mortem to be carried out please contact Ann Storey in
advance for consent and advice on how to proceed. Tel: 01322
285788 Email: president@nfrs.org
Many thanks to all the owners who helped me in this research
by filling in questionnaires and to Ann Storey for her advice.
REFERENCES
Common tumours of the rat Ann Storey Pro-Rat-A supplement 1999
Rat Health Care Debbie Ducummon
Pro-Rat-A 99 pp17-18 Letter from Andrea Withers & advice
from Esther Rawlinson MRCVS concerning possible bacterial infections
in the CNS.
Rat & Mouse Gazette Jan/Feb 2000 Weakness in older rats:
A paralysis primer. Kathy Barrett available at www.rmca.org/articles/paralysis.htm
Modulation of estrogen action in the rat pituitary and mammary
glands by dietary energy consumption. Thomas J. Spady et al.
The American Society For Nutritional Sciences Journal of Nutrition
1999 available at www.nutrition.org/cgi/content/full/129/2/5875
Effect of diet or reproductive status on the histology of spontaneous
pituitary tumours in female Wistar rats. P.H. Berry Veterinary
Pathology Vol 23 Issue 5 pp610-618 1986 Available at www.vetpathology.org/cgi/content/abstract/23/5/610
Genetic separation of tumor growth & hemorrhagic phenotypes
in an estrogen-induced tumor. Douglas L.Wendell, Allison Herman,
Jack Gorski 1996
Available on www.pnas.org/cgi/reprint/93/15/8112.pdf
www.radil.missouri.edu/RADILinfo/dora/RATPAGE/neo.htm photograph
of pituitary adenoma & brief description
www.petrats.org/infoforvetsetc.html#Pituitary Brief info on
diagnosis & treatment of pituitary tumours
www.guinealynx.info/ivermectin.html information on ivermectin
www.guinealynx.info/NADAVetMedInteractions.html for reported
reactions to ivermectin
Sally Clark can be contacted via email at: Sally.Clark@bigfoot.com
