Epidemiological study of rift valley fever virus in Kigoma, Tanzania

Rift Valley fever (RVF) is an acute, zoonotic viral disease, caused by a Phlebovirus belonging to the Bunyaviridae family. RVF virus (RVFV) historically has been responsible for large explosive outbreaks of severe human and animal disease throughout Africa and recently in the Arabian Peninsula. In animals, it mainly affects domestic ruminants such as sheep, goats and cattle. RVFV outbreaks among livestock are economically devastating and often characterized by large sweeping abortion storms and significant mortality in adult livestock. This study was conducted to investigate RVF infection in Kigoma region. Regional wide serosurvey and conventional gel based single tube RT-PCR were conducted in Kigoma region on non- vaccinated small ruminants (sheep and goats). The study included 411 animals (32 sheep and 379 goats) sampled in 3 districts namely; Kigoma rural, Kasulu and Kibondo. Sera of animals were tested for the detection of immunoglobulins G (IgG) against RVFV using commercial enzyme-linked immunosorbent assays (ELISA) kit. Past infections were detected in 22 of 411 animals (5.4% at 95% CI 3.5 % to 8.1%) from all three districts. Kigoma rural recorded higher seroprevalence of 12.0% (CI 7.3% to 18.3%; P0.05) and Kasulu districts (0.8% [0.0% to 4.2%]; P>0.05). The prevalence was 12.5% and 4.7% for sheep and goats respectively. RT-PCR results indicated that only 8 samples were found positive (n=63) including 22 positive samples for IgG ELISA, where none was RT-PCR positive. This study has confirmed, for the first time, the presence of RVFV in Kigoma region, 4 years after the 2007 epizootic in Tanzania, and suggests further that the virus activity exists during the interepizootic period (IEP) even in regions with no history of RVF. In-depth studies should be conducted to clarify the complex epidemiology of RVF in the country.Southern African Centre for Infectious Disease Surveillance (SACIDS

Epidemiological study of Rift Valley fever virus in Kigoma, Tanzania

Rift Valley fever virus (RVFV) is an acute, zoonotic viral disease caused by a  Phlebovirus, which belongs to the Bunyaviridae family. Among livestock, outbreaks of the disease are economically devastating. They are often characterised by large, sweeping abortion storms and have significant mortality in adult livestock. The aim of the current study was to investigate RVFV infection in the Kigoma region, which is nestled under the hills of the western arm of the Great Rift Valley on the edge of Lake Tanganyika, Tanzania. A region-wide serosurvey was conducted on non-vaccinated small ruminants (sheep and goats, n = 411). Sera samples were tested for the presence of anti-RVFV antibodies and viral antigen, using commercial enzyme-linked immunosorbent assay and reverse transcriptase polymerase chain reaction, respectively. The overall past infections were detected in 22 of the 411 animals, 5.4% (Confidence Interval (CI) 95% = 3.5% – 8.1%). The Kigoma rural area recorded the higher seroprevalence of 12.0% (CI 95% = 7.3% – 18.3%; p 0.05) and the Kasulu district at 0.8% (CI 95% = 0.0% – 4.2%; p > 0.05). The prevalence was 12.5% and 4.7% for sheep and goats, respectively. Reverse transcriptase polymerase chain reaction results indicated that only eight samples were found to be positive (n = 63). This study has confirmed, for the first time, the presence of the RVFV in the Kigoma region four years after the 2007 epizootic in Tanzania. The study further suggests that the virus activity exists during the inter-epizootic period, even in regions with no history of RVFV

Microparticles as Viral RNA Carriers from Stool for Stable and Sensitive Surveillance

Since its discovery, polymerase chain reaction (PCR) has emerged as an important technology for the diagnosis and identification of infectious diseases. It is a highly sensitive and reliable nucleic acids (NA) detection tool for various sample types. However, stool, which carries the most abundant micro-organisms and physiological byproducts, remains to be the trickiest clinical specimen for molecular detection of pathogens. Herein, we demonstrate the novel application of hydrogel microparticles as carriers of viral RNA from stool samples without prior RNA purification for real-time polymerase chain reaction (qPCR). In each microparticle of primer-incorporated network (PIN) as a self-sufficient reaction compartment, immobilized reverse transcription (RT) primers capture the viral RNA by hybridization and directly initiate RT of RNA to generate a pool of complementary DNA (PIN-cDNA pool). Through a simple operation with a portable thermostat device, a PIN-cDNA pool for influenza A virus (IAV) was obtained in 20 min. The PIN-cDNA pools can be stored at room temperature, or directly used to deliver cDNA templates for qPCR. The viral cDNA templates were freely released in the subsequent qPCR to allow amplification efficiency of over 91%. The assay displayed good linearity, repeatability, and comparable limit of detection (LoD) with a commercialized viral RNA purification kit. As a proof of concept, this technology carries a huge potential for onsite application to improve human and animal infectious disease surveillance activities using stool samples without the need for a laboratory or centrifuge for sample preparation