Host-Seeking Behavior of Trombiculid Mites on Vegetation in Relation to Sika Deer

Research Advances of Leptotrombidium scutellare in China

Leptotrombidium scutellare is one of the 6 main vectors of scrub typhus in China. It has been found in more than 15 provinces of China. Especially in Yunnan, it was found to be mainly distributed in some mountainous areas with high altitude, low temperature and low precipitation. Rodents and some other small mammals were the most common hosts of L. scutellare. To date, more than 40 host species of L. scutellare have been recorded with very low host specificity, and the main hosts varied in different geographical regions. L. scutellare had a strong resistance against the cold environment, and the temperature and humidity were 2 important factors affecting its growth and development. Among different individuals of their rodent hosts, L. scutellare mites often showed an aggregated distribution pattern, which reflected the interspecific cooperation of the mites. The chromosome karyotype of L. scutellare was 2n=16 and all the 8 pairs of chromosomes were short rod-shaped with metacentric or sub-metacentric types. The isozyme spectrum supported that L. scutellare, L. deliense and L. rubellum were in the same species group. Based on the natural infection, experimental transmission and epidemiological evidence, L. scutellare has been eventually confirmed as the second major vector of scrub typhus in China, which is second only to L. deliense.

Pathology and Distribution of Trombiculosis in Northern Chamois ( Rupicapra rupicapra rupicapra) in the Italian Alps

Trombiculosis has been reported in some wild ruminant species. We investigated the occurrence of trombiculosis in the northern chamois ( Rupicapra rupicapra rupicapra) in the Western Italian Alps, and we describe the related histopathologic changes. Superficial scrapes and skin samples were taken from 191 chamois from the Lombardy and Piedmont regions during the hunting season in September-December 2015. Numbers of eosinophils, mast cells, cluster of differentiation (CD)3-, CD79α-, CD68-positive cells were determined on immunohistochemically stained skin sections using a semiautomatic analysis system. Forty (20.9, 40/191) chamois were positive for trombiculid larvae on skin scrapings. Of the positive animals, 15 were from Lombardy and 25 from Piedmont, with similar prevalences. Macroscopic lesions were light with involvement of body regions that had contact with the ground, especially head (pinnae and areas around eyes and mouth) and limbs, where stylostome was easily formed due to thin skin. Histologically, trombiculosis caused a focal moderate dermatitis with epidermal necrosis, thin crusts, and hyperkeratosis. Inflammatory infiltrates were suggestive of a granulomatous reaction centered on a stylostome, formed by mite saliva and necrotic host tissue debris. However, we detected some difference in cutaneous immune response with some chamois showing a prevalent T-cell response and others having an increased B-cell count associated with a higher number of eosinophils, mast cells and a lower number of T cells.