Chihuahua — questions to ask before paying a deposit
A responsible breeder will have these readily available. Deflection is a red flag.
Patellar luxation
The kneecap slips out of its groove. A large UK first-opinion veterinary study found 'slipping kneecap' in 4.0% of Chihuahuas, more often than in other dogs, and it is one of the three CHIC-required tests for the breed.
Ask to see: OFA patellar luxation exam (graded 0-4) on both parents from one year of age.
RVC VetCompass - World's smallest dogs prone to health problems despite rising popularity (https://www.rvc.ac.uk/vetcompass/news/world-s-smallest-dogs-prone-to-health-problems-despite-rising-popularity-according-to-latest-rvc-research) · Chihuahua Club of America - AKC Health Statement (https://cdn.akc.org/Marketplace/Health-Statement/Chihuahua.pdf)
Early-onset degenerative mitral valve diseasecan shorten life or cause chronic pain
A heart valve thickens and leaks with age. Heart disease was the leading cause of death in a large UK Chihuahua study (18.8% of deaths). Screening aims to catch early murmurs so breeding can move away from affected lines.
Ask to see: Annual cardiac auscultation (OFA cardiac exam) by a vet or board-certified cardiologist on both parents from one year of age.
Chihuahua Club of America - AKC Health Statement (https://cdn.akc.org/Marketplace/Health-Statement/Chihuahua.pdf) · RVC VetCompass - World's smallest dogs prone to health problems despite rising popularity (https://www.rvc.ac.uk/vetcompass/news/world-s-smallest-dogs-prone-to-health-problems-despite-rising-popularity-according-to-latest-rvc-research)
Persistent fontanelle (molera) and its relationship to skull/brain findings
A soft spot on top of the skull (molera) is long-standing in the breed and is still mentioned in most Chihuahua breed standards. The breed club's own position, based on older veterinary opinion, is that a molera on its own does not predispose to hydrocephalus. More recent peer-reviewed imaging research (2021) found that Chihuahuas with more and larger persistent fontanelles were also more likely to have low body weight, an enlarged fourth ventricle and a crowded craniocervical junction of the kind associated with Chiari-like malformation and syringomyelia — an association with extreme miniaturisation and skull shape, not proof that an ordinary molera itself causes disease.
Ask to see: No genetic test exists. Ask for the parents' adult weight (the recent research finds the strongest association at very low body weight) and whether either parent has shown neurological signs such as an abnormal gait, head pressing or seizures; a domed skull with a normal-sized molera is not, on its own, evidence of hydrocephalus.
Chihuahua Club of America - Official Molera Statement (https://www.chihuahuaclubofamerica.org/thechihuahua/molerastatement) · Persistent fontanelles in Chihuahuas. Part II: Association with craniocervical junction abnormalities, syringomyelia, and ventricular volume (Kiviranta et al., J Vet Intern Med 2021) (https://onlinelibrary.wiley.com/doi/full/10.1111/jvim.16123)