n4 The utilisation of CytB and COI barcodes for the identification of bloodmeals and Culicoides species (Diptera: Ceratopogonidae) reveals a variety of novel wildlife hosts in South Africa

Acta Tropica ◽  
2021 ◽  
pp. 105913
Author(s):  
Jumari Snyman ◽  
Louwrens P. Snyman ◽  
Karien Labuschagne ◽  
Gert J. Venter ◽  
Marietjie Venter
Keyword(s):  
South Africa ◽  
Culicoides Species

Comparison of the efficiency of five suction light traps under field conditions in South Africa for the collection of Culicoides species

2009 ◽  
Vol 166 (3-4) ◽  
pp. 299-307 ◽  
Author(s):  
G.J. Venter ◽  
K. Labuschagne ◽  
K.G. Hermanides ◽  
S.N.B. Boikanyo ◽  
D.M. Majatladi ◽  
...  
Keyword(s):  
South Africa ◽  
Field Conditions ◽  
Culicoides Species ◽  
Light Traps

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

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.

scholarly journals Possible over-wintering of bluetongue virus in Culicoides populations in the Onderstepoort area, Gauteng, South Africa

2016 ◽  
Vol 87 (1) ◽  
Author(s):  
Jumari Steyn ◽  
Gert J. Venter ◽  
Karien Labuschagne ◽  
Daphney Majatladi ◽  
Solomon N.B. Boikanyo ◽  
...  
Keyword(s):  
South Africa ◽  
Bluetongue Virus ◽  
Close Association ◽  
Culicoides Species ◽  
Gauteng Province ◽  
Mild Winter ◽  
Biting Rate ◽  
Winter Temperatures ◽  
Vector Activity ◽  
Vector Capacity

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.

scholarly journals Culicoides imicola, vecteur du virus de sérotype 8 de la fièvre catarrhale ovine

2009 ◽  
Vol 62 (2-4) ◽  
pp. 127
Author(s):  
Gert J. Venter ◽  
I. Wright ◽  
R. Del Rio ◽  
D. Majatladi ◽  
I. Hermanides ◽  
...  
Keyword(s):  
South Africa ◽  
South African ◽  
Field Isolate ◽  
The Other ◽  
Northern Europe ◽  
Culicoides Species ◽  
The South ◽  
South African Isolate ◽  
Virus Recovery ◽  
African Isolate

Based on its abundance near livestock and wide geographical distribution, one of the most important Culicoides virus vector species of orbiviruses is the Afro-Asiatic species C. (Avaritia) imi­cola. It is considered a proven vector of bluetongue virus (BTV) and is one of the world’s most widely distributed Culicoides spe­cies. Strong correlations were found between the presence of C. imicola and outbreaks of BT and African horse sickness (AHS) in Africa and BT in Southern Europe. In 2006, BT serotype 8 (BTV- 8) was responsible for the first outbreaks ever of BT recorded in Northern Europe. Outbreaks first appeared in the Netherlands and Belgium, and subsequently spread to Germany, France, and Luxemburg. The virus apparently overwintered in Northern Europe and, during 2007-2008, spread across the whole of Europe. The outbreaks in Northern Europe happened in the absence of C. imicola. Members of the Culicoides (Culicoides) pulicaris and C. (A.) Obsoletus complexes have been implicated in BTV transmission. In the present study, the oral susceptibil­ity of C. imicola and other South African livestock associated Culicoides species to various isolates of BTV-8 were determined by artificial feeding. During summer 2008, a Belgium and a recent (2004) South African field isolate of BTV-8 were fed to Culicoides collected at two localities in South Africa. Adult Culicoides midges were collected at the Agricultural Research Council; Onderstepoort Veterinary Institute (ARC-OVI) and at Clarens, in a cooler mountainous area of South Africa. At ARC-OVI the dominant species was C. imicola and at Clarens it was C. (A.) bolitinos. The South African field isolate was fed at con­centrations of 5.8 and 7.8 log10TCID50/mL in the blood meal and the Belgium isolate at 6.8 log10 TCID50/mL. The following summer (2009) the same South African (6.8 log10 TCID50/mL) and Belgium (6.8 log10 TCID50/mL), a Dutch (4.8 log10 TCID50/ mL) and a Spanish (6.1 log10 TCID50/mL) isolates of BTV-8 were fed to Culicoides species collected at ARC-OVI. In the same season, the South African and Belgium isolates were also fed to midges collected at Clarens. Virus recovery, after an incubation period of 10 days at 23.5°C in C. imicola, was low for all iso­lates for both years. The South African isolate (5.8 log10 TCID50/ mL) and the Spanish isolate of BTV-8 could not be recovered from 420 and 492 midges tested after incubation. The recov­ery rate for the other isolates ranged from 2/403 (0.5%) (2008: SA isolate) to 1/683 (0.1%) (2009: SA isolate). These relatively low recovery rates make direct comparison between isolates problematic. Virus recovery from C. bolitinos fed on the South African isolate (7.8 log10 TCID50/mL) was significantly higher than any of the other isolates. During 2008 the Belgium iso­late could be recovered from 4/229 (1.7%) C. bolitinos tested. Other Culicoides species from which BTV-8 could be isolated included C. (Meijerehelea) leucostictus, C. (A.) gulbenkiani and C. (unplaced) angolensis. Viral concentrations in infected C. imi­cola ranged from 0.7 to 2.4 and from 0.7 to 3.4 log10 TCID50/ mL in C. bolitinos. These results are in agreement with previous studies indicating a similarly low susceptibly in C. imicola for the reference strain of BTV-8. The relatively low oral susceptibility to near refractory status of C. imicola as determined for some of the isolates in this study will easily be compensated for by the high abundance of C. imicola in South Africa. Cumulative laboratory oral susceptibility results from South Africa indicate a consistently higher susceptibility in C. bolitinos for BTV as well as a multi-vector potential for BTV as well as AHSV. The unique biology of potential vector competent Culicoides species emphasizes the complex epidemiology of these diseases.

Time and Latitude in South Africa

1972 ◽  
Vol 1 ◽  
pp. 27-38
Author(s):  
J. Hers
Keyword(s):  
South Africa ◽  
Cape Town ◽  
Astronomical Observations ◽  
Royal Observatory ◽  
The Republic ◽  
Astronomical Determination ◽  
Limited Accuracy ◽  
Better Than

In South Africa the modern outlook towards time may be said to have started in 1948. Both the two major observatories, The Royal Observatory in Cape Town and the Union Observatory (now known as the Republic Observatory) in Johannesburg had, of course, been involved in the astronomical determination of time almost from their inception, and the Johannesburg Observatory has been responsible for the official time of South Africa since 1908. However the pendulum clocks then in use could not be relied on to provide an accuracy better than about 1/10 second, which was of the same order as that of the astronomical observations. It is doubtful if much use was made of even this limited accuracy outside the two observatories, and although there may – occasionally have been a demand for more accurate time, it was certainly not voiced.

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