Development and Evaluation of a One-Step Quantitative RT-PCR Assay for Detection of Lassa Virus.

Lassa fever is a severe viral hemorrhagic illness caused by Lassa virus. Based on estimates, the number of LASV infections ranges from 300,000 to 500,000 cases in endemic areas with a fatality rate of 1%. Development of fast and sensitive tools for the control and prevention of Lassa virus infection as well as for clinical diagnostics of Lassa fever are crucial. Here we reported development and evaluation of a one-step quantitative RT-qPCR assay for the Lassa virus detection - LASV-Fl. This assay is suitable for the detection of lineages I-IV of Lassa virus. The limit of detection of the assay ranged from 103 copies/ml to 105 copies/ml and has 96.4% diagnostic sensitivity, whereas analytical and diagnostic specificities both were 100%. Serum, whole blood and tissue are suitable for use with the assay. The assay contains all the necessary components to perform the analysis, including an armored positive control (ARC+) and an armored internal control (IC). The study was done during the mission of specialized anti-epidemic team of the Russian Federation (SAET) in the Republic of Guinea in 2015-2018. Based on sequencing data, LASV-specific assay was developed using synthetic MS2-phage-based armored RNA particles, RNA from Lassa virus strain Josiah, and further, evaluated in field conditions using samples from patients and Mastomys natalensis rodents.

Rodent control to fight Lassa fever: Evaluation and lessons learned from a 4-year study in Upper Guinea.

Lassa fever is a viral haemorrhagic fever caused by an arenavirus. The disease is endemic in West African countries, including Guinea. The rodents Mastomys natalensis and Mastomys erythroleucus have been identified as Lassa virus reservoirs in Guinea. In the absence of a vaccine, rodent control and human behavioural changes are the only options to prevent Lassa fever in highly endemic areas. We performed a 4 year intervention based on chemical rodent control, utilizing anticoagulant rodenticides in 3 villages and evaluating the rodent abundance before and after treatment. Three additional villages were investigated as controls. Analyses to assess the effectiveness of the intervention, bait consumption and rodent dynamics were performed. Anthropological investigations accompanied the intervention to integrate local understandings of human-rodent cohabitation and rodent control intervention. Patterns of bait consumption showed a peak at days 5-7 and no consumption at days 28-30. There was no difference between Bromadiolone and Difenacoum bait consumption. The main rodent species found in the houses was M. natalensis. The abundance of M. natalensis, as measured by the trapping success, varied between 3.6 and 16.7% before treatment and decreased significantly to 1-2% after treatment. Individuals in treated villages welcomed the intervention and trapping because mice are generally regarded as a nuisance. Immediate benefits from controlling rodents included protection of food and belongings. Before the intervention, local awareness of Lassa fever was non-existent. Despite their appreciation for the intervention, local individuals noted its limits and the need for complementary actions. Our results demonstrate that chemical treatment provides an effective tool to control local rodent populations and can serve as part of an effective, holistic approach combining rodent trapping, use of local rodenticides, environmental hygiene, house repairs and rodent-proof storage. These actions should be developed in collaboration with local stakeholders and communities.

Post-Ebola Measles Outbreak in Lola, Guinea, January-June 2015(1).

During public health crises such as the recent outbreaks of Ebola virus disease in West Africa, breakdowns in public health systems can lead to epidemics of vaccine-preventable diseases. We report here on an outbreak of measles in the prefecture of Lola, Guinea, which started in January 2015.

Spatial and temporal evolution of Lassa virus in the natural host population in Upper Guinea.

This study aimed at reconstructing the spatial and temporal evolution of Lassa virus (LASV) in the natural host population. To this end, we generated 132 partial nucleoprotein sequences of LASV from M. natalensis trapped in 12 villages around Faranah, Upper Guinea, over a period of 12 years. This study reveals two main features of LASV evolution in M. natalensis. First, the virus evolves in the reservoir with a molecular clock rate of 9 (7-11) × 10(-4) position(-1) year(-1) implying that contemporary LASV lineages circulate in the Faranah area since less than 100 years. Second, viruses circulating in a specific village are diverse and polyphyletic. We observed, however, there are monophyletic clusters at village and sub-village level at specific points in time. In conclusion, our data indicate that the temporal and spatial pattern of LASV evolution in the natural reservoir is characterized by a combination of stationary circulation within a village and virus movement between villages. The latter feature is relevant for rodent control strategies, as it implies that recurrence of the virus from neighbouring villages may occur in villages where the virus has previously been eradicated.