Multi-disease panel for the Swiss White Shepherd that groups the three tests of its components: MDR-1 defect (ABCB1, drug hypersensitivity), congenital pituitary dwarfism (LHX3) and degenerative myelopathy (DM, SOD1 exon 2). Each test reports clear/carrier/affected status for the corresponding variant and allows matings to be planned. The panel does not replace clinical follow-up: MDR-1 sensitivity requires lifelong therapeutic caution and DM has incomplete penetrance.

Applicable breed: Swiss White Shepherd. Carrier frequencies are not systematically published for the three variants (limited data). The MDR-1 defect is documented in related herding breeds and in the Swiss White Shepherd. LHX3 pituitary dwarfism is documented in the Swiss White Shepherd (Schils et al., 2025), with frequencies described in other breeds for the same variant (allele frequency 0.094 in German Shepherd Dogs from the Netherlands, 31 % carriers in Saarloos and 21 % in Czechoslovakian Wolfdog), not in this breed. Cases of dwarfism in the Swiss White Shepherd are scarce.

- Neurotoxicity (tremors, ataxia, salivation, mydriasis, coma) after ivermectin or other P-glycoprotein substrates (MDR-1)\n- Normal growth in the first weeks followed by slowing, proportionate short stature, persistent puppy coat with symmetrical alopecia and hyperpigmentation (pituitary dwarfism)\n- GH, TSH and reproductive hormone deficiency; neurological signs due to atlantoaxial instability in some cases (pituitary dwarfism)\n- Progressive pelvic limb paresis with proprioceptive ataxia in the adult (DM)

The MDR-1 defect was associated with a deletion in ABCB1 initially described in collies (Mealey et al., 2001) and extended to herding breeds, including the Swiss White Shepherd. Pituitary dwarfism was linked to a contracted 7-bp repeat in intron 5 of LHX3 (Voorbij et al., 2011), later confirmed in other breeds; Schils et al. (2025) documented it specifically in a Swiss White Shepherd with ACTH deficiency. Canine DM was associated with the SOD1 exon 2 variant (Awano et al., 2009).

- Genotype breeding animals before mating, including the intron 5 deletion of LHX3 (main variant)\n- For the recessive conditions (pituitary dwarfism and DM): do not mate carrier x carrier (25 % risk of affected homozygotes); carrier x clear produces no affected animals and yields 50 % carriers\n- For MDR-1: avoid mating two mutated homozygotes (the whole litter would be sensitive to ivermectin and other P-gp drugs); heterozygotes may be mated to clear animals; communicate the drug sensitivity to the buyer\n- After a confirmed clinical case, do not repeat the parental mating and record the status with the breed club

MDR-1 sensitivity requires reviewing the list of problematic drugs (ivermectin at high antiparasitic doses, loperamide, several chemotherapeutic agents, certain anaesthetics) before any treatment. Pituitary dwarfism is distinguished from other causes of short stature (isolated GH deficiency, disproportionate dwarfism, hypothyroidism, malnutrition) and is confirmed by hormone profile (GH/IGF-1, TSH, sex hormones) and LHX3 DNA test. DM is a diagnosis of exclusion: rule out spinal cord compression, disc herniation and neoplasia before attributing the picture to SOD1.

Componente MDR-1 (samk):
1. Mealey KL et al. 2001. Ivermectin sensitivity in collies is associated with a deletion mutation of the mdr1 gene. Pharmacogenetics. PMID: 11692082
2. Mealey KL. 2004. Therapeutic implications of the MDR-1 gene. J Vet Pharmacol Ther. PMID: 15500562

Componente enanismo hipofisario (kwdz):
3. Voorbij AM et al. 2011. A contracted DNA repeat in LHX3 intron 5 is associated with aberrant splicing and pituitary dwarfism in German shepherd dogs. PLoS One. PMID: 22132174
4. Voorbij AM et al. 2014. Pituitary dwarfism in Saarloos and Czechoslovakian wolfdogs is associated with a mutation in LHX3. J Vet Intern Med. PMID: 25273400
5. Thaiwong T et al. 2021. Dwarfism in Tibetan Terrier dogs with an LHX3 mutation. J Vet Diagn Invest. PMID: 33890524
6. Kyöstilä K et al. 2021. Intronic variant in POU1F1 associated with canine pituitary dwarfism. Hum Genet. PMID: 33550451
7. Schils G et al. 2025. Pituitary dwarfism and adrenocorticotropic hormone deficiency in a White Swiss Shepherd dog with LHX3 mutation. J Vet Intern Med. PMID: 40833232
8. OMIA:002314-9615. Pituitary hormone deficiency, LHX3-related.

Componente DM (dnvf):
9. Awano T et al. 2009. Genome-wide association analysis reveals a SOD1 mutation in canine degenerative myelopathy. Proc Natl Acad Sci U S A. PMID: 19188595
10. Coates JR et al. 2010. Canine degenerative myelopathy. Vet Clin North Am Small Anim Pract. PMID: 20732599
11. OMIA:000263-9615. Degenerative myelopathy.