Ectoparasites of brown rats (Rattus norvegicus) in Grenada, West Indies

Comparative analysis of the intestinal microbiome in Rattus norvegicus from different geographies

Rat species Rattus norvegicus, also known as the brown street rat, is the most abundant mammal after humans in urban areas, where they co-exist with humans and domestic animals. The reservoir role of R. norvegicus of zoonotic pathogens in cities among rodent-borne diseases that could endanger the lives of humans and other mammals. Therefore, understanding the normal microbiome of R. norvegicus is crucial for understanding and preventing zoonotic pathogen transmission to humans and animals. We investigated the intestinal microbiome of free-living R. norvegicus collected from the Ruili, Nujiang, and Lianhe regions of Yunnan, China, using 16S rRNA gene sequence analysis. Proteobacteria, followed by Firmicutes, and Bacteroidetes were abundant in the intestines of R. norvegicus; however, bacterial compositions varied significantly between samples from different locations. Following a similar trend, Gammaproteobacteria, Bacilli, and Clostridia were among the top bacterial classes in most intestinal samples. The situation differed slightly for the Lianhe and Nujiang samples, although Phyla Bacteroidota and Spirochaetota were most prevalent. The Alpha diversity, Chao1, and Simpson indexes revealed microbial richness among the R. norvegicus samples. A slight variation was observed among the samples collected from Ruili, Nujiang, and Lianhe. At species levels, several opportunistic and zoonotic bacterial pathogens, including Lactococcus garvieae, Uruburuella suis, Bartonella australis, Clostridium perfringens, Streptococcus azizii, Vibrio vulnificus, etc., were revealed in the R. norvegicus intestines, implying the need for a regular survey to monitor and control rodent populations. In conclusion, we explored diverse microbial communities in R. norvegicus intestines captured from different regions. Further, we identified several opportunistic and potential bacterial pathogens, which still need to be tested for their underlying pathogenesis. The findings of our current study should be considered a warning to the health authorities to implement rat control and surveillance strategies globally.

The pests of a pest: A systematic review of ectoparasitic fauna among synanthropic rodents in the 21st century with meta-analysis

Synanthropic rodents are important urban pests that frequently carry hematophagous ectoparasites. These blood-sucking pests are capable of transmitting epizootic and zoonotic pathogens by landing on one host after feeding on an infected animal. This study aimed to estimate the prevalence of ectoparasites carried by synanthropic rodents and discuss the pathogens that are associated with these external parasites. We searched relevant literatures using predefined criteria in the following databases: EMBASE, PUBMED, Web of Science and Scopus from January 2000 to June 2020. Quality of studies was evaluated using Newcastle-Ottawa scale (NOS). Of 35 included studies from 15 countries in Africa, America, Asia, Europe and Oceania, black rats (R. rattus), brown rats (R. norvegicus), pacific rats (R. exulans) and house mice (Mus musculus) were common synanthropic rodents. Mites (Mesostigmata, Sarcoptiformes and Trombidiformes) were the most prevalent (42.6%, 95% CI 26-59.2), followed by ticks (Ixodida) (21.5%, 95% CI 10.5-32.6), lice (Phthiraptera) (17.8%, 95% CI 7.7-27.9) and fleas (Siphonaptera) (14.1%, 95% CI 10.1-18.1). Heterogeneity (I2>96%) across studies was statistically significant. The ectoparasitic fauna was shared considerably by different urban rodent species and appeared to be more diverse in R. rattus and R. norvegicus. Nonetheless, pathogens carried by these ectoparasites were rarely investigated. In conclusion, ectoparasites are ubiquitous in urban-dwelling rodents but our understanding of the epidemiology and the associated pathogens of these parasites remains limited. Further studies are warranted to unravel the pathogen landscape found in rodent-associated ectoparasites.