Possible over-wintering of bluetongue virus in <i>Culicoides</i> populations in the Onderstepoort area, Gauteng, South Africa

Several studies have demonstrated the ability of certain viruses to overwinter in arthropod vectors. The over-wintering mechanism of bluetongue virus (BTV) is unknown. One hypothesis is over-wintering within adult Culicoides midges (Diptera; Ceratopogonidae) that survive mild winters where temperatures seldom drop below 10 °C. The reduced activity of midges and the absence of outbreaks during winter may create the impression that the virus has disappeared from an area. Light traps were used in close association with horses to collect Culicoides midges from July 2010 to September 2011 in the Onderstepoort area, in Gauteng Province, South Africa. More than 500 000 Culicoides midges were collected from 88 collections and sorted to species level, revealing 26 different Culicoides species. Culicoides midges were present throughout the 15 month study. Nine Culicoides species potentially capable of transmitting BTV were present during the winter months. Midges were screened for the presence of BTV ribonucleic acid (RNA) with the aid of a real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) assay. In total 91.2% of midge pools tested positive for BTV RNA. PCR results were compared with previous virus isolation results (VI) that demonstrated the presence of viruses in summer and autumn months. The results indicate that BTV-infected Culicoides vectors are present throughout the year in the study area. Viral RNA-positive midges were also found throughout the year with VI positive midge pools only in summer and early autumn. Midges that survive mild winter temperatures could therefore harbour BTV but with a decreased vector capacity. When the population size, biting rate and viral replication decrease, it could stop BTV transmission. Over-wintering of BTV in the Onderstepoort region could therefore result in re-emergence because of increased vector activity rather than reintroduction from outside the region.

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Interactions vecteurs-virus : diversité des sérotypes et des souches de la peste équine africaine, et populations géographiques

Revue d’élevage et de médecine vétérinaire des pays tropicaux ◽

10.19182/remvt.10023 ◽

2009 ◽

Vol 62 (2-4) ◽

pp. 107

Author(s):

Gert J. Venter ◽

I. Hermanides ◽

D. Majatladi ◽

S. Boikanyo ◽

I. Wright

Keyword(s):

South Africa ◽

Vector Competence ◽

Vectorial Capacity ◽

Infection Prevalence ◽

Culicoides Species ◽

Vector Population ◽

Biting Rate ◽

Critical Components ◽

Susceptibility Tests ◽

Different Strains

The most abundant Culicoides species in an area is not inevitably the most competent vector species for a specific virus. Oral susceptibility, as an indicator of vector competence, is a measure of the portion of vectors taking a blood meal from an infected host that actually becomes infective. Cumulative laboratory oral susceptibility results from South Africa indicate a multivector potential for bluetongue virus (BTV) as well as for African horse sickness virus (AHSV). Considering the unique biology of potential vector competent Culicoides species one can appreciate the complex epidemiology of these diseases. The oral susceptibly of C. imicola, a proven vector of AHSV and BTV, was relatively low for most of the viral isolates and even appeared to be refractory to infection with some of the isolates used. This relatively low oral susceptibility may partly explain the low field infection prevalence of AHSV and BTV recorded in field collected midges. In South Africa, the relatively low oral susceptibility as determined for some of the isolates is easily compensated for by the high abundance of C. imicola. Differences found in the virus recovery rates of various AHSV serotypes/isolates from the various Culicoides species and even different populations of the same species emphasize the fact that, although oral susceptibility tests provide important information about a specific vector population, it provides no predictability about the behaviour of other populations with different strains of virus. Differences found in the oral susceptibility of C. imicola and C. bolitinos for isolates of the same serotypes of AHSV suggest coadaptation between orbiviruses and vectors present in a given locality. Real-time monitoring of vector competence might be difficult as it would require assessing local Culicoides populations using variants of orbiviruses currently in circulation. It needs to be emphasized that laboratory demonstration of oral susceptibility is not the only necessary step to implement a competent vector. It is, however, an indication of the ability of a vector to support virus replication and one of the critical components of vectorial capacity. Vector capacity is the relative measure of a vector population to transmit a virus to a vertebrate population. In addition to vector competence, vectorial capacity depends on the biting rate, host selection, vector survivorship, and the extrinsic incubation period of the virus.

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Ascertaining the Role of Leadership on Employee Satisfaction in Market and Social Research Industries in Gauteng Province of South Africa Using Qualitative Research

International Journal on Leadership ◽

10.21863/ijl/2015.3.2.009 ◽

2015 ◽

Vol 3 (2) ◽

Author(s):

Kingstone Mutsonziwa ◽

Philip Serumaga-Zake

Keyword(s):

South Africa ◽

Employee Satisfaction ◽

Quantitative Research ◽

Social Research ◽

Labour Productivity ◽

Working Environment ◽

Gauteng Province ◽

Career Growth ◽

Quantitative Results ◽

Mixed Approach

This paper is based on the study a Doctor of Business Leadership (DBL) thesis titled A Statistical Model for Employee Satisfaction in the Market and Social Research Industries in Gauteng Province. The purpose of this study was to identify the attributes that affect employee satisfaction in the Market and Social Research Industries in Gauteng Province, South Africa. In order to address the overall objective of this study, the researcher used a two-tiered (mixed) approach in which both qualitative and quantitative research methodologies were used to complement and enrich the results. This paper is only based on the qualitative component of the study on leadership aspects based on six leaders (two from Social research and four from Market research) that were interviewed. The leaders were selected based on their knowledge of the industry and the expertise they have. Participation in the survey was voluntary. This paper illustrates the power of the qualitative techniques to uncover or unmask the leadership aspects in the Market and Social Research Industries and also gives the human touch to the quantitative results. It was found that leadership and management within the Market and Social Research Industries in Gauteng Province must ensure that they are accommodative in terms of mentoring their subordinates. The industry is driven by quality driven processes and strong leadership. More importantly, issues of a good working environment, remuneration, career growth, and recognition must always be addressed in order to increase employee satisfaction, reduce staff turnover, and attempt to optimize labour productivity. The qualitative findings also help a deeper understanding of leadership within the industry.

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