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J Wildl Dis. 2018 Apr;54(2):380-385. doi: 10.7589/2017-09-214. Epub 2018 Jan 25.

Respiratory Mites ( Orthohalarachne diminuata) and β-hemolytic Streptococci-Associated Bronchopneumonia Outbreak in South American Fur Seal Pups ( Arctocephalus australis).

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1 Department of Pathology, College of Veterinary Medicine, University of Georgia, D. W. Brooks Dr., Athens, Georgia 30602, USA.
2 Instituto de Patología Animal, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Isla Teja s/n, Valdivia 509000, Chile.
3 Programa de Investigación Aplicada en Fauna Silvestre, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Isla Teja s/n, Valdivia 509000, Chile.
4 Facultad de Ciencias, Pontificia Universidad Católica de Chile, 340 Bernardo O'Higgins Ave., Santiago 8320000, Chile.


Although mites of the Orthohalarachne genus are common parasites of otariids, their role as agents of disease and in causing population-level mortality is unknown. In the austral summer of 2016, there was an increase in mortality among South American fur seal ( Arctocephalus australis) pups at Guafo Island, Northern Chilean Patagonia. Pups found dead or terminally ill had moderate to marked, multifocal, mucopurulent bronchopneumonia associated with large numbers of respiratory mites ( Orthohalarachne diminuata) and rare Gram-positive cocci. In lung areas less affected by bronchopneumonia, acute interstitial pneumonia with marked congestion and scant hemorrhage was evident. Bacteria from pups dying of bronchopneumonia were isolated and identified as Streptococcus marimammalium and Streptococcus canis. Respiratory mites obstructed airflow, disrupted airway epithelial lining, and likely facilitated the proliferation of pathogenic β-hemolytic streptococci, leading to severe bronchopneumonia and death of fur seal pups. An abrupt increase in sea surface temperature in Guafo Island corresponded to the timing of the bronchopneumonia outbreak. The potential role of environmental factors in the fur seal pup mortality warrants further study.


Arctocephalus australis; Guafo Island; Orthohalarachne; Streptococcus; bronchopneumonia; marine mammals

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