Habitat and season drive chigger mite diversity and abundance on small mammals in Peninsular Malaysia
Alkathiry H., Al-Rofaai A., Ya’cob Z., Cutmore T.S., Mohd-Azami S.N.I., Husin N.A., Lim F.S., Koosakulnirand S., Mahfodz N.H., Ishak S.N., Loong S.K., Stekolnikov A., Mohd-Taib F.S., Abubakar S., Makepeace B.L., Chaisiri K., Khoo J.J.
Pathogens, 11 (10): 1087 (2022).
S U M M A R Y
Chigger mites are vectors of the bacterial disease scrub typhus, caused by Orientia spp.
The bacterium is vertically transmitted in the vector and horizontally transmitted to terrestrial
vertebrates (primarily wild small mammals), with humans as incidental hosts. Previous studies
have shown that the size of the chigger populations is correlated with the density of small mammals
in scrub typhus-endemic regions. Here, we explore interactions between the small mammals and
chiggers in two oil palm plantations located in the Perak and Johor states of Peninsular Malaysia.
The location in Perak also contained an aboriginal (Orang Asli) settlement. A ~5% sub-sample from
40,736 chigger specimens was identified from five species of small mammals (n = 217), revealing 14
chigger species, including two new records for Malaysia. The abundance and species richness of
chiggers were significantly affected by habitat type (highest in forest border), state (highest in
Perak), and season (highest in dry). The overall prevalence of Orientia tsutsugamushi DNA in small mammal
tissues was 11.7% and was not significantly affected by host or habitat characteristics, but
in Johor, was positively associated with infestation by Leptotrombidium arenicola. These findings
highlight the risk of contracting scrub typhus in oil palm plantations and associated human