First Report on the Molecular Detection and Characterization of Rickettsia felis in Laelapidae (Acari: Mesostigmata) Mites in Malaysia

Rickettsiae are Gram-negative and obligate intracellular bacteria that cause rickettsioses. These pathogens are typically transmitted by arthropod vectors, such as ticks, mesostigmatid mites, and fleas. Rickettsiae are responsible for many emerging infectious diseases worldwide and are the second most frequently reported cause of non-malarial febrile illnesses in Southeast Asia. However, in Malaysia, studies on the prevalence and distribution of rickettsiae have primarily focused on humans, with limited data on these bacteria in vectors and small mammal hosts. Thus, this study aims to investigate the presence of <i>Rickettsia</i> spp. in small mammals and their associated mesostigmatid mites collected from potential rickettsioses areas in Selangor. Animal trapping was conducted across three different ecological study sites comprising a recreational area, agricultural land, and coastal area. A total of 41 small mammals and 363 mesostigmatid mites were collected and identified. Ten percent of the total individual mites were processed for morphological examination, and the remaining mites were then pooled by hosts, with five individual mites per tube, for DNA extraction. The collected samples, comprising blood, animal tissue, and pooled mites, were subjected to DNA extraction and were screened for <i>Rickettsia</i> spp. via nested polymerase chain reaction (PCR), targeting the citrate synthase-encoding gene (<i>gltA</i>) and outer membrane protein B gene (<i>ompB</i>). Interestingly, two pools (3.33%) of <i>Laelaps</i> spp. recovered from <i>Maxomys whiteheadi</i> and <i>Bandicota indica</i>, collected from a recreational area, tested positive for <i>Rickettsia</i> spp. Sequence analysis and phylogenetic tree of the <i>ompB</i> gene revealed the presence of <i>Rickettsia felis</i> in both laelapid mite pools. To our knowledge, this study provides the first molecular detection of <i>R. felis</i> in <i>Laelaps</i> spp. in Malaysia.