Genetic Diversity of Rift Valley Fever Strains Circulating in Namibia in 2010 and 2011

Outbreaks of Rift Valley fever (RVF) occurred in Namibia in 2010 and 2011. Complete genome characterization was obtained from virus isolates collected during disease outbreaks in southern Namibia in 2010 and from wildlife in Etosha National Park in 2011, close to the area where RVF outbreaks occurred in domestic livestock. The virus strains were sequenced using Sanger sequencing (Namibia_2010) or next generation sequencing (Namibia_2011). A sequence-independent, single-primer amplification (SISPA) protocol was used in combination with the Illumina Next 500 sequencer. Phylogenetic analysis of the sequences of the small (S), medium (M), and large (L) genome segments of RVF virus (RVFV) provided evidence that two distinct RVFV strains circulated in the country. The strain collected in Namibia in 2010 is genetically similar to RVFV strains circulating in South Africa in 2009 and 2010, confirming that the outbreaks reported in the southern part of Namibia in 2010 were caused by possible dissemination of the infection from South Africa. Isolates collected in 2011 were close to RVFV isolates from 2010 collected in humans in Sudan and which belong to the large lineage containing RVFV strains that caused an outbreak in 2006–2008 in eastern Africa. This investigation showed that the RVFV strains circulating in Namibia in 2010 and 2011 were from two different introductions and that RVFV has the ability to move across regions. This supports the need for risk-based surveillance and monitoring.

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Phylogeny of Rift Valley fever virus isolates recovered from humans during 2008-2011 disease outbreaks in South Africa

International Journal of Infectious Diseases ◽

10.1016/j.ijid.2014.03.887 ◽

2014 ◽

Vol 21 ◽

pp. 224

Author(s):

A.A. Grobbelaar ◽

J. Weyer ◽

P. Leman ◽

A. Kemp ◽

J.T. Paweska

Keyword(s):

South Africa ◽

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Disease Outbreaks ◽

Fever Virus ◽

Valley Fever ◽

Virus Isolates

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Antigenic analysis of Rift valley fever virus isolates: monoclonal antibodies distinguish between wild-type and neurotropic virus strains

Research in Virology ◽

10.1016/0923-2516(91)90069-f ◽

1991 ◽

Vol 142 (6) ◽

pp. 469-474 ◽

Cited By ~ 15

Author(s):

T.G Besselaar ◽

N.K Blackburn ◽

G.M Meenehan

Keyword(s):

Monoclonal Antibodies ◽

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Wild Type ◽

Antigenic Analysis ◽

Valley Fever ◽

Neurotropic Virus ◽

Virus Isolates ◽

Virus Strains

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A comparative genome analysis of Rift Valley Fever virus isolates from foci of the disease outbreak in South Africa in 2008-2010

10.1101/338251 ◽

2018 ◽

Author(s):

Moabi R. Maluleke ◽

Maanda Phosiwa ◽

Antoinette van Schalkwyk ◽

George Michuki ◽

Baratang A. Lubisi ◽

...

Keyword(s):

South Africa ◽

Amino Acid ◽

Rift Valley ◽

Rift Valley Fever ◽

Evolutionary Dynamics ◽

Amino Acid Substitutions ◽

Valley Fever ◽

Virus Serotype ◽

Northern Cape ◽

Virus Isolates

AbstractRift Valley fever (RVF) is a re-emerging zoonotic disease responsible for major losses in livestock production, with negative impact on the livelihoods of both commercial and resource-poor farmers in sub-Sahara African countries. The disease remains a threat in countries where its mosquito vectors thrives. Outbreaks of RVF usually follow weather conditions which favour increase in mosquito populations. Such outbreaks are usually cyclical, occurring every 10-15 years.Recent outbreaks of the disease in South Africa have occurred unpredictably and with increased frequency. In 2008 outbreaks were reported in Mpumalanga, Limpopo and Gauteng provinces, followed by a 2009 outbreak in KwaZulu-Natal, Mpumalanga and Northern Cape provinces and in 2010 in the Eastern Cape, Northern Cape, Western Cape, North West, Free State and Mpumalanga provinces. By August 2010, 232 confirmed infections had been reported in humans, with 26 confirmed deaths.To investigate the evolutionary dynamics of RVF viruses (RVFVs) circulating in South Africa, we undertook complete genome sequence analysis of isolates from animals at discrete foci of the 2008-2010 outbreaks. The genome sequences of these viruses were compared with viruses from earlier outbreaks in South Africa and in other countries. The data indicates that one 2009 and all the 2008 isolates from South Africa and Madagascar (M49/08) cluster in Lineage C or Kenya-1. The remaining of the 2009 and 2010 isolates cluster within Lineage H, except isolate M259_RSA_09, a probable segment M reassortant.Author summaryA single RVF virus serotype exists, yet differences in virulence and pathogenicity of the virus have been observed. This necessitates the need for detailed genetic characterization of various isolates of the virus. The RVF virus isolates that caused the 2008-2010 disease outbreaks in South Africa were most probably reassortants. Reassortment results from exchange of portions of the genome, particularly those of segment M. Although clear association between RVFV genotype and phenotype has not been established, various amino acid substitutions have been implicated in the phenotype. Viruses with amino acid substitutions from glycine to glutamic acid at position 277 of segment M have been shown to be more virulent in mice in comparison to viruses with glycine at the same position. Phylogenetic analysis indicated the viruses responsible for the 2008-2010 RVF outbreaks in South Africa were not introduced from outside the country, but mutated in time and caused the outbreaks when environmental conditions became favourable.

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