Cross-sectional survey of ixodid tick species on grazing cattle in Japan

Hard Tick Species Parasitism Levels in Domestic Ruminants with Their Distribution and Role as Vectors: A Detailed Global Meta-analysis and Systematic Review

PURPOSE

This comprehensive global meta-analysis reviews the parasitism levels of tick genera and species, life stages, seasonality, attachment sites, the global mean ranks of tick species parasitism rates and records, and their distribution and role as vectors.

METHODS

From the 418 papers identified, 390 papers were selected to become part of the study.

RESULTS

The genera recorded as infesting domestic ruminants were Rhipicephalus (42 species), Haemaphysalis (32 species), Hyalomma (19 species), Amblyomma (18 species), Ixodes (10 species), Dermacentor (8 species), Margaropus and Nosomma (1 species). Globally, domestic ruminants are more infested by adult females and males than by the nymphal and larval stages of the tick species. The global tick species parasitism levels at the attachment sites of domestic ruminants were, in order, tail and anal region, neck and dewlap, scrotum or udder, ear region, thigh and abdomen, and dorsal surface.

CONCLUSIONS

Among 131 species of eight genera of hard ticks recorded infesting domestic ruminants, 42 species had mean ranks of tick species parasitism rates up to 10%, and 37 species had mean ranks of tick species parasitism up to 10 records. Briefly, the higher the indexes of tick species parasitism rates and records, the more important their role as vectors. In addition, the majority of them are found among tick species-infested humans with nearly high ranks of tick species parasitism rates and records that double their medical, veterinary, and zoonotic importance to be the most common vectors and reservoirs of bacterial, protozoan, and viral pathogenic microorganisms, causing severe infectious diseases, and as a result, can be more dangerous to humans and domestic ruminants.

Higher sika deer density is associated with higher local abundance of Haemaphysalis longicornis nymphs and adults but not larvae in central Japan

Haemaphysalis longicornis (Acari: Ixodidae) is one of the most common and important arthropod disease vectors in Japan, carrying Japanese spotted fever and bovine theileriosis. The recent expansion of sika deer (Cervus nippon, Artiodactyla: Cervidae) populations, the most common wild host of H. longicornis, has also caused concern about increasing the risk of vector-borne diseases in Japan. We used generalized linear mixed model analysis to determine the relative contribution of deer density and other biological and abiotic factors on the abundance of H. longicornis ticks questing at each developmental stage. A total of 6223 H. longicornis adults, nymphs, and larvae were collected from 70 sites in three regions of central Japan. The abundance of questing adult and nymphal ticks was associated with deer density and other biotic and abiotic factors. However, the abundance of questing larvae showed no association with deer density but did show an association with other biotic and abiotic factors. These findings show that a high density of deer along with other biotic and abiotic factors is associated with increased risk of vector-borne diseases through amplified local abundance of questing nymphal and adult H. longicornis. Further, questing larvae abundance is likely regulated by environmental conditions and is likely correlated with survival potential or the distribution of other host species.

Genetic diversity of Theileria orientalis in tick vectors detected in Hokkaido and Okinawa, Japan

In the present study, we investigated the possible tick vectors that can transmit Theileria orientalis in eastern Hokkaido, Japan. Questing ticks collected from three different districts, Taiki, Otofuke, and Shin-Hidaka, of Hokkaido included Ixodes persulcatus, Haemaphysalis megaspinosa, Haemaphysalis douglasi, and Ixodes ovatus, while all the ticks collected from Yonaguni island of Okinawa were identified as Haemaphysalis longicornis. When the ticks were screened by polymerase chain reaction (PCR) for T. orientalis, the parasite was commonly detected among all tick species. Genotype-specific PCR assays revealed that all tick species in Hokkaido were predominantly detected with type 2, while ticks collected from Okinawa (H. longicornis) were predominantly detected with type 1. Consistent with the genetic diversity of T. orientalis in ticks, genotyping PCR assays from cattle grazed in the same Hokkaido sampling locations identified type 2 as the most prevalent genotype. This study provides the first identification of I. persulcatus, H. megaspinosa, H. douglasi, and I. ovatus as possible tick vectors of T. orientalis, and finds that the variety of vectors apparently capable of transmitting T. orientalis is wider in Japan than expected. The authors suggest that tick control strategies should be modified in Hokkaido based on the seasonal activities of ticks identified in the present study.