My fiancée's family has a Parson Russell Terrier who they adopted at 6 months, he is now 9 and has been deaf all his life that we are aware of. He has always shown aggression towards strangers in the house, but never outdoors away from the house. It seemed like he had territorial aggression, unfortunately due to him being deaf training him out of it was near impossible and the family lived with it.

The past 2 days, he has suddenly turned, completely unprovoked on my fiancée's sister. It is unlike what he has done before, even towards strangers, rather than it being warning to leave, he is actively trying to get at her, snarling, growling and barking viciously. We believe if he was able to get at her he would cause serious injury.

My partner locked him in the kitchen, which is where he sleeps, behind a baby gate and tied it up for extra security. To see if the dog would calm down after a while he called his sister to simply stand there and offer him some treats. He stood there and as soon as he looked at her instantly went from a calm and peaceful state to a really aggressive one, he actually squeezed half of his body through the bars of the baby gate to try to get at her.

My partner left him alone and later he came to check on him, the dog then showed exactly the same signs of aggression towards my partner as he did with his sister, though after 20 seconds the dog calmed down, wagged his tail and seemed his friendly self as though nothing had happened. He has never before shown any signs of aggression towards them other than growling to warn them of doing something (grumpy or tired).

My partner's mother gave the dog a sedative, which the vets had given, in order to calm him down. An hour later, he was sedated, lethargic and could hardly walk. He still showed the same signs of aggression towards them once in sight.

In all the situations over the past 2 days there was no provocation, and no food, toys etc that he could be guarding. My partner is deeply saddened as he thinks he may have to be put down for the family's safety.

Considering this has now happened for 2 days in a row, it is quite worrying. My partner thinks it could be "Mental Lapse Aggression", what do you think?

Can any of you think of any illness which would cause this other than one that requires euthanasia?

I've suggested they take him to the vets to check that nothing physical is going on first before making any decisions.

Sorry for such long post, but wanted to include as much information as possible, any input would be greatly appreciated.

Definitely the vet as a first port of call - then go from there. If a physical cause is ruled out then I would seek the help of a behaviourist immediately rather than seeking advice on an internet forum - seems of a severity where proper assessment and professional help is needed.

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Same as dogless, definately a check up at the vets, if he is in pain because of a problem it will make him edgy and he might just have chosen a couple of people to take it out on
Then a trainer/behaviourist to see if they have any idea on what has suddenly changed.

Hope the little guys gets sorted without the need to be PTS.

*Heidi*

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Dogs in pain, or feeling below parr can suddenly start to react with re-directed aggresssion. If this has suddenly occured and is really over the top out of character behaviour and given his age I deffinately would be making vets a first port or call asking the to give him a full physical exam and blood tests too.

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Thank you all for your replies, i basically wanted to check that the first step of action would be a physical exam and if anyone had experienced Mental Lapse Aggression. In all honesty if there is no physical cause i think the family will have to let him be pts. They have contacted behaviorists in the past regarding his territorial aggression but no one would take him on due to him being deaf. His territorial aggression is nothing like the aggression he is displaying now, its as if he's in some sort of "kill mode". If a behaviorist wouldn't take him on before they certainly wouldn't now unfortunately

hey, Katie!
i am sorry to be so blunt, but being deaf is only an excuse for not hearing - not for Not Training.
there is no reason whatever NOT to train a deaf-dog; i've had clients & friends with both deaf-Dals
& normal-hearing-Dals, & they have told me rather shamefacedly that the deaf dogs were easier to train,
as they were undistracted by noises off: barking, footsteps, a cat crying, children playing...
Vet, Vet, Vet...
could be pain & redirected aggro, could be thyroid, a focal seizure, a past fright which is causing this
severe reaction... the very minimum i'd recommend is a full 5-way thyroid panel, sent to Michigan
State Univ vet-lab for analysis; they have the world's largest breed-specific database for thyroid values.

if his results are borderline low, i would ask the vet about a short course of low-dosage thyroid
supplement - 2 to 3-weeks should be revealing, if his behavior improves, there ya go. Thyroid supplement
is lifelong, but luckily it's also cheap.

i have never heard of this in my life - who came up with that?
and how in heaven's name do we DIAGNOSE a dog we've never seen - not even in a video?!
veterinarians diagnose; trainers can make suggestions to seek a vet's help, we can't diagnose or prescribe.

if his kidneys are failing, toxins in the blood can cause bizarre behavior; ditto for the liver's function.
poisons affect the brain - i am not talking about poisons we might eat, drink, inhale or touch, but body toxins
that are not being removed from the bloodstream, but are accumulating & circulating, instead of removed,
detoxified or excreted.

if he fails to RECOGNIZE familiar people, this would explain it, too - he may think that strangers are in his home.
senior canine-cognitive disorder is not uncommon, but there's a medication for it, too - and it's been quite
effective in a number of older dogs, some of whom sadly would get lost in a corner in their own homes,
& be trapped there, crying, unable to figure out how to get out of the angle of the walls. they are not
doing that anymore - they recognize family members, enjoy walks & play again, & while no younger
nor any more athletic, they're much happier - not wandering the house barking in the middle of the night.

LINK: Cognitive Dysfunction Syndrome
Anipryl is the only medication that i know of specific for CDS.

cataracts? retina deterioration?
he may also be losing his sight - & again, that's not something impossible to cope with.
if he is losing vision & growing reactive because of it, counterintuitively wearing a Calming Cap
& reducing his vision even more, can help - it forces him to rely on his nose, & his olfactory recognition should
still be very accurate; he will literally remember people as a scent better than he does by sight.

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terry pride, APDT-Aus, apdt#1827, CVA, TDF
*wolves R wolves, dogs R dogs, + primates R us.*
tmp, sept-2007

‪Basil's Tricks!‬‏ - YouTube

this is Basil, a pup whose parents were both merle - DoG curse his breeders.
Basil is a sweet dog who is anything but stoopid.

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terry pride, APDT-Aus, apdt#1827, CVA, TDF
*wolves R wolves, dogs R dogs, + primates R us.*
tmp, sept-2007