First report of a severe nasopulmonary acariasis caused by Doetschman, 1944 (Acari: Halarachnidae) in a captive South American sea lion ( Shaw, 1800).

Obligatory endoparasitic mites of the genera Allman, 1847 and Newell, 1947 (Acari: Halarachnidae) parasitize different segments of the respiratory tract of marine mammals, including pinnipeds and sea otters, and infestations can cause asymptomatic to serious respiratory diseases. However, knowledge on biology, pathogenic potential and occurrence of halarachnid mites infesting pinnipeds, especially in captivity, is scarce. A two-year-old South American sea lion ( Shaw, 1800) male, born and held at the Vienna Zoo, was anesthesized for routine pre-transport examinations, including computed tomography, bronchoalveolar lavage, and blood sampling. During the final phase of general anesthesia, the individual abruptly became apneic and died despite all attempts at resuscitation. At necropsy, 45 highly motile whitish millimeter-sized structures were macroscopically detected in the trachea, and main bronchi and were identified as adult stages of Doetschman, 1944 following morphological descriptions. After trepanation of the nasal cavity and , a total of 407 larval and 3 nymphal specimens distributed in clusters were detected. Macroscopically, sinus mucosa showed hyperemia and multiple petechial hemorrhages. Histopathological analyses of paranasal sinuses revealed mite cross-sections surrounded by sanioserous exudate and epithelial exfoliation. For the first time, was molecularly characterized and phylogenetically analyzed based on its 16S rDNA. Our study constitutes the first record of a severe infestation in captive and one of the few host-parasite records in general. We present clinical data and pathological results, the first scanning electron microscopic images of a larval stage and discuss the etiology of this autochthonous infestation, possible transmission pathways and detrimental effects. Further studies on biology and pathogenic effects of halarachnid mites, as well as on the development of non-invasive sampling techniques are essentially required for a better understanding of (ortho-)halarachnosis in pinnipeds held in zoological gardens.