THE THEO PROJECT - FIRST DATA REPORT

56 unique cases | 11 countries | April 21st 2026

⚠️ Trigger warning: This report contains data on outcomes including the loss of dogs to MUE. Please read with care.

About this report

The Theo Project launched on April 3rd 2026. In just 18 days we received 56 unique submissions from dog owners across 11countries - Canada, the United States, England, Scotland, Spain, Poland, Finland, the Netherlands, New Zealand, Australia and Singapore. This is our first data snapshot. It is crowd-sourced from dog owners and has not been independently verified by veterinary professionals. As the registry grows, the data will become more powerful. Every submission counts.

We are aware that individual researchers may require more detailed clinical information than our form captures. This is why we ask submitters for an optional contact email - so that if a researcher wishes to follow up directly with a specific case, that door is open.

Diagnoses represented

Of our 56 submissions, dogs were diagnosed with MUE/MUO (confirmed), SRMA, GME and related conditions. A small number remain suspected but unconfirmed due to incomplete diagnostic testing - often because of financial constraints or because the dog deteriorated too rapidly for full testing to be completed.

Outcomes

Approximately 20% of dogs in our registry have sadly passed away from their condition. Of the remaining dogs, the majority are stable on medication, with a smaller number in full remission and off medication entirely. A significant number are experiencing ongoing flare ups. These figures are consistent with published research on MUE, which suggests roughly one third of dogs respond well and achieve remission, one third remain on lifelong medication, and one third do not survive.

Age at diagnosis

The vast majority of dogs in our registry were diagnosed under 2 years of age, with several diagnosed as young as 10 weeks old. This is consistent with published research which identifies young dogs as the most commonly affected. However our data also includes older dogs - the oldest in our registry was 11 years old at diagnosis - confirming that no age is immune.

Area affected

Approximately half of all dogs in our registry had both their brain and spinal cord affected. Around a quarter had brain involvement only, and approximately one in five had spinal involvement only. A small number had unknown or unconfirmed areas of involvement.

Breeds represented

While MUE can affect any breed, certain breeds appear repeatedly in our registry. Maltese and Maltipoo dogs appear most frequently, followed by Chihuahuas, Pomeranians, Labradors, Dachshunds, Boston Terriers, Golden Retrievers and Cavapoos. This is broadly consistent with published research which identifies small and toy breeds as most commonly affected - though the presence of larger breeds such as Labradors, Golden Retrievers and Bernese Mountain Dogs in our data is notable.

Treatment response

The overwhelming majority of dogs in our registry responded to steroids - primarily prednisone or prednisolone - within days of starting treatment. This is consistent with the immune-mediated nature of the disease. Additional medications used across submissions included cyclosporine, cytarabine, leflunomide, azathioprine, Keppra and gabapentin among others.

Vaccinations before symptoms

Approximately 68% of dogs in our registry had received vaccinations in the months before symptoms started. Several owners specifically noted a close temporal relationship between vaccination and onset of symptoms. The most notable case in our registry involves four dogs from the same litter, all diagnosed within four days of receiving the same rabies vaccine. Another dog relapsed three days after receiving booster vaccines. A third was diagnosed three days after receiving puppy vaccines while simultaneously unwell with two separate infections.

It is important to note that the majority of dogs receive vaccinations routinely, which means this figure alone cannot establish causation. The Theo Project remains neutral on vaccination - we recognise it is a vital and important part of protecting dog health for most dogs. We are simply collecting and reporting what owners have shared with us, so that researchers can investigate patterns that owners are observing in the real world. We are not drawing conclusions - we are asking questions. If the data ultimately shows no meaningful relationship, that is a valuable finding too.

Flea and tick treatment before symptoms

Approximately 54% of dogs in our registry had received flea and tick treatment before symptoms started. The most commonly named products were Simparica and Simparica Trio, Nexgard and Nexgard Spectra, and Bravecto - all of which belong to the isoxazoline class of drugs, which carry an existing FDA warning regarding neurological side effects in some dogs.

Several owners noted a specific temporal relationship between flea and tick treatment and onset or relapse of symptoms. Most notably, one owner reports that two separate relapses coincided directly with doses of Simparica Trio, with no relapse occurring after the product was discontinued. Another owner directly attributes her dog's blindness to Simparica. A third dog relapsed after accidentally receiving another dog's flea medication.

As with vaccinations, the majority of dogs receive flea and tick treatment routinely, so this figure alone cannot establish causation. The Theo Project remains neutral on flea and tick prevention - we recognise it plays an important role in protecting dog health. We are simply recording what owners have reported so that researchers can investigate further. We are not making claims. We are collecting data - and we believe that data, whatever it ultimately shows, belongs in the hands of people who can properly analyse it.

Misdiagnosis

Misdiagnosis before the correct diagnosis was reached was extremely common across our submissions. The most frequent misdiagnoses included intervertebral disc disease (IVDD), Lyme disease, a pulled muscle, vestibular disease, and in some cases brain tumour. Several owners describe being sent home by vets multiple times before a neurologist was eventually consulted. This highlights the urgent need for greater awareness of MUE among general veterinary practitioners.

The financial impact

The financial devastation of MUE is a theme that runs through almost every submission in our registry. Owners describe spending thousands - and in some cases tens of thousands - of pounds, dollars and euros on diagnosis and treatment. Many describe using savings, credit cards and crowdfunding platforms. Several describe stopping chemotherapy because they could no longer afford it. Insurance frequently did not cover the full cost. This is a disease that does not just affect dogs - it devastates families.

What this data cannot yet tell us

Our registry is 18 days old and 56 cases strong. This is a beginning, not a conclusion. The patterns we are observing - particularly around vaccinations, flea and tick treatments, breed predisposition and outcomes - are compelling, but they require a much larger dataset to be statistically meaningful. We are not scientists and we are not drawing clinical conclusions. We are collecting the data that doesn't yet exist and making it available to those who can.

What happens next

We will continue to publish updated data reports as the registry grows. We are in the process of reaching out to veterinary neurology research departments to share our data with those who are actively researching this disease. Every submission brings us one step closer to turning the unknown into the known.

If you haven't yet submitted your dog's story - please do. It takes 10 minutes and could change everything for the next family sitting in a waiting room not knowing what is happening to their dog.

The Theo Project is run by dog owners, not veterinary professionals. All data is crowd-sourced and has not been independently verified. Nothing in this report constitutes veterinary advice.