Human Otoacariasis in Two Climatically Diverse Districts in Sri Lanka: Seasonality, Risk Factors, and Case Notes

Dermacentor (Indocentor) auratus Supino 1897: Potential geographic range, and medical and veterinary significance

Dermacentor (Indocentor) auratus Supino, 1897 occurs in many regions of Southeast Asia and South Asia. In many regions of Southeast Asia and South Asia, targeted tick sampling and subsequent screening of collected D. auratus ticks have detected pathogenic bacteria and viruses in D. auratus. These disease-causing pathogens that have been detected in D. auratus include Anaplasma, Bartonella, Borrelia, Rickettsia (including spotted fever group rickettsiae), African swine fever virus, Lanjan virus, and Kyasanur forest disease virus. Although D. auratus predominantly infests wild pigs, this tick is also an occasional parasite of humans and other animals. Indeed, some 91 % of human otoacariasis cases in Sri Lanka were due to infestation by D. auratus. With the propensity of this tick to feed on multiple species of hosts, including humans, and the detection of pathogenic bacteria and viruses from this tick, D. auratus is a tick of medical, veterinary, and indeed zoonotic concern. The geographic range of this tick, however, is not well known. Therefore, in the present paper, we used the species distribution model, BIOCLIM, to project the potential geographic range of D. auratus, which may aid pathogen and tick-vector surveillance. We showed that the potential geographic range of D. auratus is far wider than the current geographic distribution of this tick, and that regions in Africa, and in North and South America seem to have suitable climates for D. auratus. Interestingly, in Southeast Asia, Borneo and Philippines also have suitable climates for D. auratus, but D. auratus has not been found in these regions yet despite the apparent close proximity of these regions to Mainland Southeast Asia, where D. auratus occurs. We thus hypothesize that the geographic distribution of D. auratus is largely dependent on the movement of wild pigs and whether or not these wild pigs are able to overcome dispersal barriers. We also review the potential pathogens and the diseases that may be associated with D. auratus and provide an updated host index for this tick.

Ear Mites as an Overlooked Source of Ear Itching and Tinnitus - A Case Series

Otoacariasis is a rare condition characterized by ticks and mites in the ear canal. Human otoacariasis remains underrepresented in literature as otoacariasis is more common in animals. Systemic diseases being transmitted by these arachnids pave the way for potential complications. This case series sheds light on this uncommon condition by highlighting the diverse symptomatology and difficulties in diagnosis and treatment. Three different presentations highlight the diversity of this condition. A 40-year-old male exhibited itching and tinnitus, revealing a mite on the tympanic membrane on otoscopy. A 35-year-old female with persistent itching and tinnitus showed multiple whitish mites on examination. A 50-year-old female complained of ear pain and was found to have a tick attached to the external auditory canal. The relevance and rarity of human otoacariasis are highlighted in this study, thereby encouraging caution in situations of earache. We aim to increase clinician awareness about this condition and the necessary interventions required by conducting a thorough literature review.

Diversity and Geographic Distribution of Dog Tick Species in Sri Lanka and the Life Cycle of Brown Dog Tick, Rhipicephalus sanguineus Under Laboratory Conditions

PURPOSE

This study determined the diversity and distribution of tick species infesting domestic dogs and the life cycle parameters of the dominant dog tick species.

METHODS

An island-wide, cross-sectional survey of tick species infesting domestic dogs was carried out, and the life cycle of the most commonly occurring dog tick, Rhipicephalus sanguineus was studied under laboratory conditions.

RESULTS

A total of 3026 ticks were collected from 1219 dogs in all 25 districts. Eight species in five genera were identified: R. sanguineus (63.4%), R. haemaphysaloides (22.0%), Haemaphysalis bispinosa (12.5%), Haemaphysalis intermedia (0.9%), Haemaphysalis turturis (0.6%), Amblyomma integrum (0.4%), Dermacentor auratus (0.2%) and Hyalomma sp (0.1%). R. sanguineus was the dominant species in the Dry and Wet zones, while R. haemaphysaloides was the dominant species in the Intermediate Zone. Species diversity (Shannon diversity index H) was 1.135, 1.021and 0.849 in the Intermediate, Dry and Wet zones, respectively. The three-host life cycle of R. sanguineus was completed within 70-126 days, and all three stages successfully fed on New Zealand white rabbits under laboratory conditions. The Reproductive Efficiency Index (REI) and Reproductive Fitness Index (RFI) were 50.8 ± 9.69 and 9.1 ± 5.01, respectively. Larger females had higher reproductive success.

CONCLUSIONS

Of the eight species infesting domestic dogs in Sri Lanka, R. sanguineaus was the most frequently occurring tick species. The three-host life cycle of R. sanguineus was successfully completed within an average of 98 days on New Zealand white rabbits. The number of eggs laid, duration of the pre-oviposition period, incubation period and parasitic periods of all three life stages were lower than in previous records.