Miniature American Shepherd: percent of dogs surveyed carrying at least one copy of the mdr1-1delta (ABCB1 nt230(del4)) multidrug-sensitivity mutation -- heterozygous + homozygous combined (Neff et al. 2004, Table 1, studied as 'Australian Shepherd, Miniature')

as of 2026-09-20 · license: facts-only

• A 2004 convenience sample of client-owned/breeder dogs (not a random population sample), n=56, the smallest breed sample in this table.
• The mutation is incompletely dominant, so both heterozygous and homozygous carriers can show drug sensitivity (e.g. to ivermectin, loperamide) -- this figure is not 'affected' in the sense of a fully penetrant disease.
• Studied under the breed's pre-2015 name, 'Australian Shepherd, Miniature' -- mapped here to this breed via its Miniature Australian Shepherd alias, not re-surveyed under the current AKC name.
• Gramer et al. 2011 (Vet J), a more recent MDR1 breed-distribution study also naming this breed, is paywalled (Elsevier) and not open access; not fetched or substituted (docs/sources.md).

Source

Proceedings of the National Academy of Sciences (PNAS), via PMC — Neff MW, Robertson KR, Wong AK, Safra N, Broman KW, Slatkin M, Mealey KL, Pedersen NC (2004). Breed distribution and history of canine mdr1-1Delta, a pharmacogenetic mutation that marks the emergence of breeds from the collie lineage. Proc Natl Acad Sci U S A 101(32):11725-11730.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC511012/
retrieved 2026-09-20

Method

Table 1 mut/wt (heterozygous) percent + mut/mut (homozygous) percent, summed

n = 56

from: data/mdr1-neff2004.json

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