Vectors and The Infection Rates of Zoonotic Diseases Caused by Rats at Bangkok Port

Abstract

       A cross-sectional survey study was performed to determine types and numbers of rats and vectors carrying zoonotic diseases at point of entry, Bangkok Port. The survey was conducted by placing rat cage traps at various points around the areas of the Bangkok Port. After classification, samples of blood, kidney, spleen, heart and lungs were collected for laboratory tests as well as identification of ectoparasites. The study results showed that among 130 laying cage traps, a total of 37 rats were trapped. The trap success rate was 28.46%. The majority of trapped rats were Rattus rattus (81.08%) while the minority of them were Rattus exulans (18.92%). The ectoparasite infestation rate was 35.14%. The flea index was 1.00. Adult rat lung parasite (Angiostrongylus sp.) was not found. The detection of antibodies to rickettsia infection by Indirect immunofluorescent assay of 35 blood specimens collected from hearts was demonstrated that 42.86%, 40% and 26.67% were positive for Murine typhus, Scrub typhus and Tick typhus, respectively. It was also found that 4 specimens (26.67%) were positive for both Murine typhus and Scrub typhus. Furthermore, 7 blood samples (20%) positive for rickettsia infections were found with rat fleas. Nevertheless, Leptospira infection was not found in any specimens. The index of the rat fleas suggested no possibility of a spread of plague at the port. In addition, the finding of rats with Murine typhus infection and living fleas at a high percentage of 66.67 indicated a high risk of Murine typhus spreading by fleas, particularly via Xenopsylla cheopis carrying Murine typhus. Based on the results, it is suggested that authorities at the Bangkok Port should expedite rat and rat flea control as control measures and further monitoring should be conducted to evaluate performance efficiency as determined by the rat flea index. In addition, surveillance of vectors at the port should be conducted every year to obtain information for risk assessment.