Location: Foreign Arthropod Borne Animal Disease Research2022 Annual Report
Objective 1: Identify factors associated with Rift Valley Fever virus infections, pathogenesis and maintenance in vector and animal hosts. • Characterize host, vector and bunyavirus interactions (molecular and cellular) associated with virus infection. • Identify epidemiological and ecological factors affecting the inter-epidemic cycle. • Develop means to detect and characterize emergent arboviral diseases and use these data to generate models that predict future outbreaks. Sub-objective 1.A: Identify cellular factors important for replication and pathogenesis in the vector and the mammalian host cells. Sub-objective 1.B: Examine the effects of temperature on the extrinsic incubation period of RVFV in various mosquito species. Sub-objective 1.C.: Develop deployable tools for rapid diagnosis and characterization of RFVF.
Rift Valley fever (RVF) is a long-recognized disease of domestic livestock in Africa caused by the arthropod-borne virus, Rift Valley Fever virus (RVFV). RVFV is a zoonotic pathogen present on the World Organisation for Animal Health (OIE) list of notifiable animal diseases of concern and the World Health Organization priority disease list. RVFV is a significant threat to U.S. livestock due to the presence of naïve host populations and competent vectors. RVFV transmission is dependent on complex interactions involving virus, arthropod vector, mammalian host, and environment. Despite the importance of this disease, many elements for RVFV replication, pathogenesis, transmission, and disease epidemiology are poorly understood. The objective of this study is to identify factors associated with RVFV infections, pathogenesis and maintenance in vector and animal hosts. This objective is split into three parts: 1) characterize host, vector and bunyavirus interactions associated with virus infection, 2) identify epidemiological and ecological factors affecting the inter-epidemic cycle and 3) develop means to detect and characterize emergent arboviral diseases and use these data to generate models that predict future outbreaks. The objective is addressed by the following sub-objectives. Sub-objective 1A identifies cellular factors important for virus replication and pathogenesis in disparate hosts by examining how Rho GTPases effects RVFV replication. Rho GTPases are key regulators of cytoskeleton rearrangement and play an important role in virus replication. Effects of temperature on RVFV extrinsic incubation period in two mosquito species will be examined for Sub-objective 1B. These studies will ascertain the potential of a mosquito species to maintain and transmit RVFV during the various temperatures associated with inter-epidemic periods. Sub-objective 1C will develop deployable diagnostic and next-generation sequencing assays to rapidly detect and characterize RVFV. These tools will provide data on virus emergence and will assist in surveillance, development of risk assessments, and predictive modeling.
Rift Valley Fever (RVF) virus is a mosquito-borne virus that is transmitted to livestock through the bite of an infected mosquito. Little is known about the virus-vector and virus-animal interactions important for the transmission and survival of the virus in nature. Studies were initiated to examine Objective 1: Identify factors associated with RVF virus infections, pathogenesis and maintenance in vector and animal hosts. Progress was made on the characterization of host, vector and bunyavirus interactions (molecular and cellular) associated with virus infection by confirming cross-reactivity of the antibodies against several Rho-family GTPase in both insect and mammalian cell lines. Rho-GTPase are known to play an important role in the replication of viruses in cells and could play an important role in the diverse pathogenic effects seen in insect cells versus mammalian cells. This is the first time antibodies for these GTPases have been used in mosquito cells and thus can be used to further understand the role of these enzymes in virus replication in the insect. In addition, the activation of these enzymes was detected in RVF virus infected mammalian cells. In collaboration with scientists from Kansas State University and Virginia Polytech Institute and State University, a novel host-virus protein interaction was identified that facilitates RVF virus production. Understanding this interaction could lead to novel control strategies. Through collaboration with researchers at Colorado State University, the effects of the environment on vector-borne disease virus replication transmission were initiated. This data will provide fundamental information for predicting virus epidemiology and ecological factors affecting the inter-epidemic cycle. In addition, RVF virus genetic material related to a 1950 strain of the virus was detected and sequenced from a mosquito pool in, and endemic to, South Africa during an inter-epidemic period. This information supports the hypothesis that RVF virus is very stable and persists through low level endemicity that goes undetected between disease outbreaks. Early detection of RVF virus is critical for a rapid response and to effectively control the associated disease. Thus, the development of a mobile sequencing technology to identify and characterize RVF virus strains was initiated. A protocol has been established to perform whole genome sequencing using a portable device. Using this protocol, virus sequence was obtained from infected cells and whole mosquitoes. This technology will allow us to identify new variants as they emerge in the field.
1. Crowd sourced mosquito surveillance as an education tool. Mosquito surveillance identifies at-risk areas and populations of people and animals by quantifying the distribution and abundance of mosquito species. This information determines when, where, and how to treat mosquito populations to prevent outbreaks of mosquito transmitted pathogens. However, thorough surveillance is time consuming and difficult if targeting mosquitoes that move only 100 m throughout their entire lives. Therefore, students and teachers were enlisted by USDA-ARS in Manhattan, Kansas, to help with mosquito surveillance while learning about mosquitoes and the risks of vector-borne diseases. ARS researchers wrote a new lesson plan which helped teachers collect non-biting mosquito larvae around their schools and the students’ homes before the mosquitoes metamorphosed into blood-feeding adults. The lesson plans were published in the National Association of Biology Teachers and made freely available to all educators and to the public. These collections are used to make mosquito distribution maps and to better survey areas that do not have established governmental mosquito control programs. The participants also learned how to protect themselves and their animals from mosquito bites.
2. Improved surveillance traps using twelve-volt batteries. Mosquito monitoring is dependent on the gold standard Centers for Disease Control (CDC) suction trap to collect disease vector mosquitoes to assess the risk of mosquito-borne pathogen transmission in an area. The well-established trap uses a six-volt battery to power a fan. But the most common reasons for collection failure are the battery runs out, or runs low on power resulting in lower mosquito collection numbers. To avoid this problem, ARS researchers in Manhattan, Kansas, introduced a voltage-regulating device (a buck converter) between the battery and the trap which allows the use of twelve-volt batteries to power the six-volt traps. Twelve-volt batteries, or car and motorcycle batteries, are cheaper and more available internationally (wherever there are motor vehicles). They also power the traps for a longer duration and with greater suction (which improves the trap collections) because they do not lose voltage as the battery runs down. Additionally, there are more recharging options with most solar panels, wall chargers, and power regulation devices aimed at recharging ubiquitous twelve-volt batteries. But the reason they are so effective is the last 30% of the battery life is the same as the first 30% when using a twelve-volt battery to power a six-volt trap. Therefore, this inexpensive and commercially available device can make any twelve-volt power supply power a six-volt trap, ultimately saving hundreds if not thousands of dollars in battery and labor costs from lost trapping nights from battery failures for the life of the CDC trap.
3. Susceptibility of domestic and wildlife to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for a global pandemic that has had significant impact on human health and economies. Since the start of the pandemic, there have been several reports regarding reverse zoonosis, transmission of virus from humans to animals. Understanding the animal species susceptible to infection is important in determining the risk potential of wild or domestic animals becoming a reservoir of the virus. ARS scientists in Manhattan, Kansas, through collaboration with Kansas State University investigators participated in evaluating the susceptibility of domestic and wild animals to SARS-CoV-2 infection. While these studies demonstrated that sheep are not very susceptible to infection, white-tailed deer are. These results suggest that white-tailed deer could play a significant role in SARS-CoV-2 maintenance and possible transmission to other wildlife, livestock, domestic animals, and humans. These results also demonstrate the importance of surveillance of wildlife for emerging pathogens as this could help inform risk assessments.
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