Shih Tzus, Lhasa Apsos, and Puppies: Why Some Dogs Are at Higher Risk of Neurological Distemper
3 min read
For years it was thought that canine distemper made no distinction by breed, age, or size. A 2025 retrospective study published in the journal Viruses by a team from the Federal University of Goiás (Brazil) added an important nuance to that idea: when the virus affects the nervous system, not all dogs face the same risk.
The researchers reviewed five years of medical records (2018 to 2022) from the neurology service of a university veterinary hospital, comparing 17 dogs with confirmed neurological distemper against 343 dogs with other diseases of the nervous system. It is the first study to use a real control group to isolate which factors increase the specific risk of the neurological form, rather than just describing individual cases.
What they found
Two breeds showed a statistically significant association: Shih Tzu and Lhasa Apso. No dog of these breeds in the study shared an owner, neighborhood, or visit date with another, which rules out the finding being just a one-off outbreak among related dogs. Younger dogs also showed a higher likelihood of developing neurological signs, in line with what was already known about puppies' vulnerability.
The other finding was seasonal: 41% of cases clustered in autumn, with the highest frequency in May (southern hemisphere). The authors attribute this to the virus surviving longer in the environment at lower temperatures, and to cold possibly favoring a state of transient immunosuppression in young animals.
A number worth looking at carefully
The study also found something uncomfortable: more than a third of the dogs with neurological distemper (35%) had an up-to-date vaccination schedule according to their own clinical records. The authors do not interpret this as the vaccine "not working," but attribute it to possible failures in vaccine storage, administration by unqualified personnel, or a gap between the last dose and the moment of exposure to the virus, factors that could not be traced in the necessary detail in retrospective medical records. The researchers' own practical conclusion is not to doubt the vaccination schedule, but to make sure it is administered by a professional, following the complete protocol and without letting the interval between doses lapse.
What to do with this information
If you have a Shih Tzu or Lhasa Apso puppy, there is no different action to take with your vet: the recommended vaccination schedule is the same for all breeds. What changes is the level of alertness: if you see neurological symptoms (tremors, seizures, behavior changes, lack of coordination) in a dog of these breeds, especially if it is young and it is autumn, it is worth consulting sooner rather than waiting to see whether it improves on its own.
Source: Freire HL, Iara ÍHN, Ribeiro LSR, Gonçalves PAO, Matta DH, Torres BBJ. "Neurological Manifestation of Canine Distemper Virus: Increased Risk in Young Shih Tzu and Lhasa Apso with Seasonal Prevalence in Autumn." Viruses. 2025;17(6):820. DOI: 10.3390/v17060820. Published under a CC BY 4.0 license.