Human otoacariasis: a retrospective study from an area of Sri Lanka.

Intra-aural ticks were present in 870 (15.2%) of 5714 patients who reported with ear-related complaints to the ear, nose and throat ward at Ratnapura Hospital, Sabaragamuwa Province, Sri Lanka, from January 2000 to December 2001. A retrospective study of 383 of these otoacariasis cases showed that the majority (70.8%) of surgically-removed ticks were nymphal Amblyomma integrum, together with nymphal and adult Rhipicephalus haemaphysaloides, R. sanguineus, Hyalomma brevipunctata, H. marginatum, and unidentified (damaged) ticks (collectively, 29.2%). Tick infestations peaked during the period November-February. More female than male patients reported with otoacariasis, and more children (aged 0-10 years) and adults (aged >/=21 years) than adolescents. There was no evidence of age-dependent differences in infestation among male and female patients. The tick-infested cases were widespread, spanning 75 km on a north-south axis and 55 km on an east-west axis within Sabaragamuwa Province. The present report represents the largest episode of human otoacariasis recorded in the literature, and may be indicative of a wider, but little-reported, human tick problem in Sri Lanka.