Four novel DNA viruses from four different families have been found in rodents and shrews across various regions of Kenya. According to a recently published study by Dr Priyom Bose, human pathogens with zoonotic origin cause over 70% of emerging infectious diseases
“Humans and animals are increasingly interacting, resulting in interspecies viral transmission that is expected to increase dramatically. The global economy and health security could suffer drastically if we are not prepared to combat newly emerged pathogens. Hence, it is imperative to conduct regular virus surveillance among potential wildlife hosts for early identification of potential pathogens before they spill over to humans,” she said. Bose holds a Ph.D. in plant biology and biotechnology from the University of Madras, India.
Dangers lurking in rodents
“Previous studies have shown that rodents and shrews are two large mammalian orders with widespread distribution and are reservoirs of many viruses. Several zoonotic viruses, such as hantaviruses, and arenaviruses, cause severe viral hemorrhagic fever diseases in humans,” she added.
For example, in Europe the Borna virus – which is commonly found in white-toothed shrews – can cause fatal encephalitis in humans. Rodents can harbour a wide range of DNA, and because of urbanisation, more pullover of pathogens takes place between humans and rodents.
“Kenya is an East African country rich in fauna and harbours multiple species of rodents and shrews and a particular species of hedgehog. With extended agricultural practices, there is an increased risk of human contact with rodents and, inevitably, rodent-borne pathogens. However, researchers indicated minimal evidence regarding viruses hosted by rodents and shrews in Kenya,” Bose explained.
“A new study published as a pre-proof in the journal Virologica Sinica is follow-up research to a previous study on the discovery of novel rodent viruses of various RNA viral families in Kenya. In this study, researchers integrated extensive sampling sites across various geographic zones in Kenya and included multiple families of DNA viruses. They conducted fieldwork between August 2016 and March 2019, in specific localities belonging to five counties of Kenya, namely, Kilifi, Nakuru, Trans-Nzoia, Nairobi, and Kajiado. These areas were selected based on human activity, climate, and altitude.
Kenya home to several monkeypox outbreaks
“Although previous studies have shown that RNA viruses possess a high rate of mutation and the capability to adapt to new hosts, the etiological role of DNA viruses in zoonotic diseases must not be ignored. For instance, the monkeypox virus (DNA virus) can infect humans along with rodents and non-human primates. In the past decades, Kenya has suffered several monkeypox outbreaks in humans.”
Kilifi county has been subject to much scientific research on how climate change impacts agricultural activity in the coastal town, while Nakuru county was Kenya’s pre-independence commercial agricultural hub. Trans-Nzoia is a known agricultural hub, as it is home to coffee, potato, tea, and maize farms, among others. Kajiado county is one of Kenya’s beef-farming and livestock-rearing counties.
“Adenoviruses (AdVs) infect almost all major vertebrate classes and are a family of DNA viruses. The largest genus of the family Adenoviridae is Mastadenovirus. A novel AdV in Mastomys natalensis (MnAdV) was discovered by scientists in the current study, which is closely related to a species of murine AdV (MAdV), namely, MAdV-2. Researchers stated that it was difficult to be conclusive whether the novel MnAdV from Kenya represented a new species or was a new subtype of MAdV-2, without knowing the complete sequence of the polymerase gene,” Bose said.
Adenoviruses are common viruses that typically cause mild cold- or flu-like illness. Adenoviruses can cause illness in people of all ages any time of year, according to the Centre for Disease Control (CDC).
“Adeno-associated viruses (AAVs) have been frequently used in gene therapy research as viral vectors. These are highly diverse among mammalian and avian hosts. In the current study, researchers reported the first detection of AAVs in African rodents, and it must be noted that the knowledge of AAV diversity in rodents is quite insufficient. This discovery should help comprehend the evolutionary patterns of mammalian AAVs,” she added.
“The results from this study reveal four novel DNA viruses from four different families in the wild as well as synanthropic rodents and shrews from Kenya.”
Most of these viruses were analysed, and following studie, should identify more sequences from these viruses to have a more robust phylogenetic conclusion.
More research needed
Furthermore, because these viruses are not closely linked to any viruses known to cause disease in people or small mammals, more research is needed to assess their pathogenicity and risk of zoonotic transmission.
“Despite the shortcomings to be addressed later, this study has increased our understanding of DNA virus diversity and evolution in small mammal reservoirs. There is a growing agricultural activity into the natural habitats of rodents in Africa, which highlights the need to continue surveillance over a wide-scale area and apply more high-throughput detection methods. Further research is also required on the pathogenicity of novel viral pathogens. Efforts such as these contribute to preventing and controlling emerging zoonotic diseases.”