Susceptibility to a sexually-transmitted disease in a wild koala population shows heritable genetic variance but no inbreeding depression

• DOI: 10.22541/au.165874643.34577990/v1
• Publication Date: 2022-07-25T10:54:00Z
• Authors: Romane Cristescu; Kasha Strickland; Anthony Schultz; Loeske Kruuk; Deirdre de Villiers; Celine Frere
• Keywords: 0301 basic medicine; quantitative genetics; Inbreeding Depression; Phascolarctos cinereus; Australia; inbreeding; Chlamydia Infections; 15. Life on land; 3. Good health; 03 medical and health sciences; Chlamydia pecorum; additive genetic effect; Animals; ORIGINAL ARTICLES; Chlamydia; Phascolarctidae

The koala, one of the most iconic Australian wildlife species, is facing several concomitant threats that are driving population declines. Some threats are well known and have clear methods of prevention (e.g. habitat loss can be reduced with stronger land-clearing control), whereas others are less easily addressed. One of the major current threats to koalas is chlamydial disease, which can have major impacts on individual survival and reproduction rates, and can translate into population declines. Effective management strategies for the disease in the wild are currently lacking, and to date we know little about the determinants of individual susceptibility to disease. Here we used a rare opportunity to investigate the genetic basis of variation in susceptibility to chlamydia using one of the most intensively studied wild koala populations. We combine data from veterinary examinations, chlamydia testing, genetic sampling and movement monitoring. Out of our sample of 342 wild koalas, 60 were found to have chlamydia. Using genotype information on 8649 SNPs to investigate the role of genetic characteristics in determining disease status, we found no evidence of inbreeding depression, but a heritability of 0.14 (95%CI: 0.06 – 0.23) for the probability that koalas had chlamydia. Heritability of susceptibility to chlamydia could be relevant for future disease management in koalas, as it suggests the potential to select for disease resilience through assisted breeding.