OMIA:001402-9685 : Multidrug resistance 1, ABCB1-related in Felis catus (domestic cat)

In other species: dog , taurine cattle , goat

Categories: Homeostasis / metabolism phene

Links to possible relevant human trait(s) and/or gene(s) in OMIM: 171050 (gene) , 120080 (trait)

Mendelian trait/disorder: yes

Considered a defect: yes

Key variant known: yes

Year key variant first reported: 2015

Cross-species summary: MDR1

Inheritance: A recessive mode of inheritance has been considered. In other species an incomplete dominant mode of inheritance is discussed.

Molecular basis: By sequencing the most obvious functional candidate gene in 8 cats that showed "adverse reactions to P-glycoprotein substrate drugs" (including one sensitive to ivermectin), Mealey and Burke (2015) discovered a 2bp deletion in the ABCB1 gene (11930_1931del TC) that was homozygous in the one cat sensitive to ivermectin. However, the other 7 sensitive cats were homozygous for a normal functional ABCB1 allele. In addition, "14 missense mutations were identified in one or more phenotyped cats". Mealey et al. (2021) investigated “whether ABCB11930_1931del TC predisposed cats to macrocyclic-lactone toxicosis and the frequency of the ABCB11930_1931del TC gene mutation in banked feline DNA samples. … 4 of the 5 cats with neurologic signs presumed to be associated with macrocyclic-lactone exposure were homozygous for ABCB11930_1931del TC. The other cat had unilateral vestibular signs not typical of macrocyclic-lactone toxicosis. … Results suggested a strong relationship between homozygosity for ABCB11930_1931del TC and neurologic toxicosis after topical application with eprinomectin-containing antiparasitic products labeled for use in cats … .”

Clinical features: Multidrug resistance 1 results in higher risk of adverse drug reactions to P-glycoprotein substrate drugs such as ivermectin and macrocyclic lactones due to impaired P-glycoprotein synthesis. These drugs are commonly found in flea and tick preventatives for cats and dogs (Mealey et al., 2023). Clinical effects can be neurological such as CNS depression, ataxia, seizure activity, tremors, hypersalivation, vomiting, mydriasis, dyspnoea, and in severe cases, coma, blindness and death. It can also manifest in bone marrow suppression in the form of neutropenia and thrombocytopenia. Gatstrointestinal toxicity has also been reported (Mealey et al., 2021). IT thanks DVM student Wen Yee Tan, who provided the basis of this contribution in May 2023.

Prevalence: Mealey et al. (2021): "The distribution of genotypes from the banked feline DNA samples was as follows: 0 homozygous for ABCB11930_1931del TC, 47 heterozygous for ABCB11930_1931del TC, and 959 homozygous for the wild-type ABCB1 allele. Among the 47 cats with the mutant ABCB1 allele, only 3 were purebred (Ragdoll, Russian Blue, and Siamese)."

Breeds: Balinese (Cat) (VBO_0100036), Domestic Longhair, Domestic medium-haired, Domestic Shorthair, Maine Coon (Cat) (VBO_0100154), Maine Coon Polydactyl (Cat) (VBO_0100155), Ragdoll (Cat) (VBO_0100196), Russian Blue (Cat) (VBO_0100200), Siamese (Cat) (VBO_0100221), Turkish Angora (Cat) (VBO_0100249).
Breeds in which the phene has been documented. (If a likely causal variant has been documented for the phene, see the variant table breeds in which the variant has been reported).

Associated gene:

Symbol Description Species Chr Location OMIA gene details page Other Links
ABCB1 ATP-binding cassette, sub-family B (MDR/TAP), member 1 Felis catus A2 NC_058369.1 (91762620..91528480) ABCB1 Homologene, Ensembl , NCBI gene


By default, variants are sorted chronologically by year of publication, to provide a historical perspective. Readers can re-sort on any column by clicking on the column header. Click it again to sort in a descending order. To create a multiple-field sort, hold down Shift while clicking on the second, third etc relevant column headers.

WARNING! Inclusion of a variant in this table does not automatically mean that it should be used for DNA testing. Anyone contemplating the use of any of these variants for DNA testing should examine critically the relevant evidence (especially in breeds other than the breed in which the variant was first described). If it is decided to proceed, the location and orientation of the variant sequence should be checked very carefully.

Since October 2021, OMIA includes a semiautomated lift-over pipeline to facilitate updates of genomic positions to a recent reference genome position. These changes to genomic positions are not always reflected in the ‘acknowledgements’ or ‘verbal description’ fields in this table.

OMIA Variant ID Breed(s) Variant Phenotype Gene Allele Type of Variant Source of Genetic Variant Reference Sequence Chr. g. or m. c. or n. p. Verbal Description EVA ID Year Published PubMed ID(s) Acknowledgements
1322 Balinese (Cat) Domestic Longhair Domestic medium-haired Domestic Shorthair Maine Coon (Cat) Maine Coon Polydactyl (Cat) Ragdoll (Cat) Russian Blue (Cat) Siamese (Cat) Turkish Angora (Cat) Adverse reaction to certain drugs ABCB1 deletion, small (<=20) Naturally occurring variant Felis_catus_9.0 A2 g.93144355_93144356del c.1930_1931del NM_001171064.2; published as ABCB1:1930_1931delTC; resuling in a frameshift generating a series of stop codons immediately downstream from the deletion. The protein product is predicted to be severely truncated (~50%) and non functional (Mealey and Burke, 2015).  2015 25660379 Genomic position in Felis_catus_9.0 provided by Leslie Lyons and Reuben Buckley. Additional breeds reported based on PMID:34125616 and PMID:35709088

Cite this entry

Nicholas, F. W., Tammen, I., & Sydney Informatics Hub. (2024). OMIA:001402-9685: Online Mendelian Inheritance in Animals (OMIA) [dataset].


Note: the references are listed in reverse chronological order (from the most recent year to the earliest year), and alphabetically by first author within a year.

2024 Mealey, K.L., Burke, N.S., Villarino, N.F., Court, M.H., Heusser, J.P. :
Application of eprinomectin-containing parasiticides at label doses causes neurological toxicosis in cats homozygous for ABCB11930_1931del TC. J Vet Pharmacol Ther 47:226-230, 2024. Pubmed reference: 38366723. DOI: 10.1111/jvp.13431.
2023 Mealey, K.L., Owens, J.G., Freeman, E. :
Canine and feline P-glycoprotein deficiency: What we know and where we need to go. J Vet Pharmacol Ther 46:1-16, 2023. Pubmed reference: 36326478. DOI: 10.1111/jvp.13102.
Mealey, K.L., Burke, N.S. :
Assessment of verdinexor as a canine P-glycoprotein substrate. J Vet Pharmacol Ther 46:264-267, 2023. Pubmed reference: 36924353. DOI: 10.1111/jvp.13123.
2022 Anderson, H., Davison, S., Lytle, K.M., Honkanen, L., Freyer, J., Mathlin, J., Kyöstilä, K., Inman, L., Louviere, A., Chodroff Foran, R., Forman, O.P., Lohi, H., Donner, J. :
Genetic epidemiology of blood type, disease and trait variants, and genome-wide genetic diversity in over 11,000 domestic cats. PLoS Genet 18:e1009804, 2022. Pubmed reference: 35709088. DOI: 10.1371/journal.pgen.1009804.
2021 Mealey, K.L., Burke, N.S., Connors, R.L. :
ABCB11930_1931del TC gene mutation in a temporal cluster of macrocyclic lactone-induced neurologic toxicosis in cats associated with products labeled for companion animal use. J Am Vet Med Assoc 259:72-76, 2021. Pubmed reference: 34125616. DOI: 10.2460/javma.259.1.72.
Nürnberger, D., Wagner, L., Müller, S.F., Leiting, S., Leidolf, R., Alber, J., Hamann, M., Geyer, J. :
Detection of the ABCB11930_1931del TC mutation in two suspected ivermectin-sensitive cats and their relatives by a novel TaqMan allelic discrimination assay. Front Vet Sci 8:808392, 2021. Pubmed reference: 35265692. DOI: 10.3389/fvets.2021.808392.
2019 Jenkins, E.L., De Souza, N.J., Beatty, J.A., Barrs, V.R. :
Suspected adverse drug interaction between spinosad and milbemycin oxime in a cat. Journal of Feline Medicine and Surgery 5(1), 5:2055116918820733, 2019.
2015 Mealey, K.L., Burke, N.S. :
Identification of a nonsense mutation in feline ABCB1. J Vet Pharmacol Ther 38:429-33, 2015. Pubmed reference: 25660379. DOI: 10.1111/jvp.12212.

Edit History

  • Created by Frank Nicholas on 14 Nov 2015
  • Changed by Frank Nicholas on 14 Nov 2015
  • Changed by Imke Tammen2 on 18 Jun 2021
  • Changed by Imke Tammen2 on 19 Feb 2022
  • Changed by Imke Tammen2 on 28 Apr 2023
  • Changed by Imke Tammen2 on 12 Jun 2023
  • Changed by Imke Tammen2 on 16 Jan 2024
  • Changed by Imke Tammen2 on 21 Jun 2024