Josefina Gutiérrez^1,2 | Mauricio Seguel³ | Pablo Saenz-Agudelo⁴ | Gerardo Acosta-Jamett⁵ | Claudio Verdugo¹

1. Ecology and Evolution of infectious Diseases Lab, Instituto de Patología Animal, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia, Chile; 2. Programa Doctorado en Ciencias mención Ecología y Evolución, Escuela de Graduados, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile; 3. Department of Pathobiology, Ontario Veterinary College, University of Guelph, Canada; 4. Instituto de Ecología y Evolución, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile; 5. Instituto de Medicina Preventiva Veterinaria, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia, Chile.

Ponente: Josefina Gutiérrez Domínguez, josefinagutierrezd@gmail.com

Genetic variability is correlated to infection resistance in wildlife, however it is a challenge to evaluate this in natural populations. Hookworm disease (Uncinaria sp.) is one of the main causes of pup mortality in several Otariid species, including the South American fur seal (Arctocephalus australis, SAFS), although many of the factors that influence infection susceptibility are still unknown. We evaluated whether the individual genetic diversity is associated with resistance to hookworm infection in SAFS pups from the largest colony of the Pacific Ocean. Using 15 microstallites, we genotyped 107 pups with different hookworm burden and calculated the individual homozygosity by loci (HL), a negative estimate of genetic variability, and other physiological parameters that influence disease susceptibility and severity (i.e., Scaled Mass Index (SMI) and anti-hookworm IgG levels). Uninfected pups had higher heterozygosity (lower HL values) compared to parasitized individuals (t=-2.799, df=15.326, p=0.013), suggesting an association between heterozygosity and parasite resistance (i.e. heterozygosity advantage). Likewise, pups that died of hookworm infection had lower heterozygosity (higher HL values) than those that died of non-infectious causes (t=2.246, df=10.277, p=0.024). Thus, the relationship between the HL and chances of infection increases proportionally and is maximized in high levels of homozygosity (df=90, z-value=2.149, p=0.032; OR=1.075; CI95%1.011-1.157). Interestingly, pups that cleared hookworm infection, and survived, had similar heterozygosity compared to pups that died of hookworm disease (df=2, F-value=1.896, p=0.159). However, pups that cleared infection had higher SMI (df=2, F-value=12.04, p=0.00004) and parasite specific IgG levels compared to those that died of hookworm disease. This study reinforces that genetic variability plays a significant role in the resistance and mortality to hookworm infection in SAFS pups. However, once infected, parasite clearance is more significantly associated with factors such as the individual condition and the adaptive immune response which depend on maternal care and nutrition quality in lactating pups. ANID scholarship N° 21201700.