The prevalence of Culicoides spp.in 3 geographic areas of South Africa

The seasonal abundance of Culicoides midges, the vector of Bluetongue and African horse sickness viruses (BTV/AHSV) and the presence of viruses in midges were determined in 3 geographic areas in South Africa. In the Onderstepoort area, more than 500,000 Culicoides midges belonging to 27 species were collected. Eighteen midge species were collected throughout Winter and the presence of AHSV and BTV RNA in midges was detected using real time reverse transcription quantitative polymerase chain reaction. The nucleic acid of AHSV was found in 12 pools out of total pools of 35 Culicoides. Twenty‑five Culicoides species were detected in the Mnisi area. The RNA of BTV was detected in 75.9% of the midge pools collected during Winter and 51.2% of those collected during Autumn. Antibodies for BTV were detected in 95% of cattle sampled using a competitive enzyme‑linked immunosorbent assay (cELISA). The dominant species in these 2 areas was Culicoides imicola. Eight Culicoides species were collected in Namaqualand. Culicoides imicola represented the 0.9% and Culicoides bolitinos the 1.5% of total catches, respectively. Antibodies for AHSV were detected in 4.4% of 874 equines tested using an indirect ELISA. Results showed that transmission of AHSV and BTV can carry on throughout Winter and the outbreak may begin as soon as Culicoides populations reach a certain critical level. [Abstract] I Culicoides sono noti vettori del virus della Bluetongue (BTV) e del virus della Peste equina africana (AHSV). Il lavoro riporta i risultati sull'abbondanza stagionale di Culicoides e sulla presenza di BTV e AHSV in diversi vettori, in tre aree geografiche del Sudafrica. Nell'area di Onderstepoort sono stati individuati più di 500.000 esemplari di Culicoides appartenenti a 27 specie diverse. Durante la stagione invernale sono state individuate 18 specie. Frammenti di RNA di AHSV e BTV sono stati rilevati mediante specifiche RT-qPCR. L'RNA del virus AHSV è stato individuato in 12 pool di Culicoides su 35 esaminati. Nell'area di Mnisi sono state identificate 25 specie di Culicoides. L'RNA di BTV è stato rilevato nel 75,9% dei pool di Culicoides catturati durante la stagione invernale e nel 51,2% di quelli catturati durante la stagione autunnale. Anticorpi contro BTV sono stati osservati nel 95% dei sieri prelevati da bovini dell'area di Mnisi ed esaminati con il metodo c‑ELISA. La specie dominante in queste due aree è risultata Culicoides imicola. Nella regione di Namaqualand sono state individuate otto specie, C. imicola ha rappresentato lo 0,9% delle specie catturate e Culicoides bolitinos l'1,5%. Anticorpi contro il virus AHSV sono stati individuati mediante ELISA nel 4,4% degli 874 equini esaminati. I risultati ottenuti hanno dimostrato che in Sudafrica la trasmissione di BTV e AHSV può continuare durante la stagione invernale mentre, con ogni probabilità, si ha la comparsa dei primi focolai quando le diverse popolazioni di Culicoides raggiungono un livello riproduttivo critico

Possible over-wintering of bluetongue virus in Culicoides 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

Zoonotic alphaviruses in fatal and neurologic infections in wildlife and nonequine domestic animals, South Africa

Alphaviruses from Africa, such as Middelburg virus (MIDV), and Sindbis virus (SINV), were detected in horses with neurologic disease in South Africa, but their host ranges remain unknown. We investigated the contribution of alphaviruses to neurologic infections and death in wildlife and domestic animals in this country. During 2010– 2018, a total of 608 clinical samples from wildlife and nonequine domestic animals that had febrile, neurologic signs or unexplained deaths were tested for alphaviruses. We identified 32 (5.5%) of 608 alphavirus infections (9 SINV and 23 MIDV), mostly in neurotissue of wildlife, domestic animals, and birds. Phylogenetic analysis of the RNA-dependent RNA polymerase gene confirmed either SINV or MIDV. This study implicates MIDV and SINV as potential causes of neurologic disease in wildlife and nonequine domestic species in Africa and suggests a wide host range and pathogenic potential.https://wwwnc.cdc.gov/eidpm2020Medical Virolog

West Nile virus in wildlife and nonequine domestic animals, South Africa, 2010–2018

West Nile virus (WNV) lineage 2 is associated with neurologic disease in horses and humans in South Africa. Surveillance in wildlife and nonequine domestic species during 2010–2018 identified WNV in 11 (1.8%) of 608 animals with severe neurologic and fatal infections, highlighting susceptible hosts and risk for WNV epizootics in Africa.The work was funded through the US Centers for Disease Control and Prevention’s Global Disease Detection grant for zoonotic arboviruses under grant 1U19GH000571-01-GDD Non-Research CoAg with the National Health Laboratory Services project 23 and University of Pretoria Zoonotic Arbo and Respiratory Virus Group income-generated funds. J.S. received doctoral scholarships from the National Research Foundation (grant no. 95175), the Meat Industry Trust (grant no. IT8114/98), and the Poliomyelitis Research Foundation (grant no. 15/112) and a partial studentship from the US Centers for Disease Control and Prevention Cooperative Agreement no. 5 NU2GGH001874-02-00 with the University of Pretoria.http://wwwnc.cdc.gov/eidam2020Medical Virolog

Epidemiology of bluetongue virus with special reference to the Mnisi area, Mpumalanga Province, South Africa

Bluetongue virus (BTV) is the prototype member of the genus Orbivirus in the family Reoviridae. This virus causes an economically important infectious, non-contagious disease, bluetongue, rendering it a notifiable disease at the OIE. Twenty six serotypes of the virus have been identified that are transmitted primarily by certain species of biting midges that belong to the genus Culicoides (Diptera: Ceratopogonidae). The distribution of BTV is determined by the occurrence of competent Culicoides midge species, climatic conditions and susceptible ruminant hosts. During the last decade BTV has become a major concern worldwide as well as the focus point of many epidemiological studies and surveillance programmes. The first experimental study was based in Mnisi, a rural area located in Mpumalanga. This area is adjacent to the Kruger National Park and ideally represents the interphase in a wildlife-domestic animal interaction. Cattle farming is the major source of income of the local community. Chapter 2 focused on determining the prevalent Culicoides spp. in the area as well as to determine whether BTV is circulating among cattle in the area. The epidemiology of bluetongue virus is very complex due to the involvement of several mammalian hosts and vector species. The role of cattle in the epidemiology of BT in SA is not well understood. Light traps were used to collect midges over 16 trap nights during autumn and winter. Culicoides midges were identified to species level and pooled (200 midges/ pool). Midge pools were subjected to real-time RT-qPCR to test for the presence of BTV RNA. Serum samples were randomly collected from 1 260 cattle and screened for antibodies specific to bluetongue virus using a BTV-specific cELISA. Blood samples were collected from seronegative cattle and screened for the presence of BTV RNA with a real-time RT-qPCR. Twenty-five different Culicoides spp. were identified of which C. imicola were found to be the most abundant. Of the 25 species collected, 19 species yielded parous females with 16 Culicoides species demonstrating a vector rating higher than 25%. Bluetongue virus RNA was detected in 51.2% and 75.9% of midge pools collected during autumn and winter, respectively resulting in an infection prevalence of 0.3% and 0.7%. Antibodies specific to BTV were detected in 1 206 (95.7%) of the sera samples tested with significant differences (p < 0.05) in seroprevalence between age groups and between villages. No significant differences in seroprevalence were observed between different breeds or sex. A total of 16 out of 45 (35.5%) blood samples from seronegative cattle tested positive for BTV RNA. These results demonstrate that C. imicola is the most abundant midge species and that BTV is highly prevalent in autumn as well as throughout winter in Mnisi. The second part of the study focused on the overwintering of BTV in Culicoides populations at the ARC-OVI. The exact method(s) of overwintering of BTV is unknown. Recent studies have suggested that the virus is overwintering within the midge vector. Climatic conditions in South Africa are suitable for adult Culicoides midges to remain active throughout much of the year with only certain areas where temperatures can become unsuitable. During such periods ambient temperature might be too low for midge emergence or viral replication within the vector. It is hypothesised that during summer, BTV infection becomes more prevalent in the Culicoides population and therefore disease only occurs in late summer to early autumn. Real-time RT-qPCR was used to detect BTV in Culicoides midges collected from July 2010 to August 2011. Bluetongue virus RNA was detected in 52 out of 57 (91.2%) midge pools tested. The results obtained strengthen the findings of chapter 2 demonstrating that BTV is present throughout winter in Culicoides populations at various temperatures. It is therefore clear Culicoides are present throughout the year and that BTV are capable of overwintering within the midge even though temperatures fall well below the normal activity range of these midges. This also forms part of a study focussing on overwintering of AHSV in the Culicoides vector. In the last research chapter of the dissertation, segment 10 of BTV isolates previously used as reference strains in the Department of Veterinary Tropical Diseases, from 1972 - 2000 were compared to establish the topotypes of these strains. Bluetongue virus can be divided into five topotypes based on segment 10 i.e. western 1, 2 and 3 and eastern 1 and 2. The groupings are based on evolutionary distinct geographical variants and phylogenetic analysis. It is hypothesised that the segment 10 genes have co-evolved with respect to the specific Culicoides species found in a geographical area. Comparing the highly conserved NS3 gene region to newly isolated strains in South Africa as well as to representative global strains could give us an indication of the degree of variability between strains and serotypes. Segment 10 from these samples were sequenced and compared to global NS3 sequences. A total of 11 sequences were obtained and submitted to GenBank. All sequences demonstrated the conserved cysteine regions as well as the tryptophan residue. Both hydrophobic regions and the proline-rich regions were also conserved throughout all 11 isolates as well as the two glycosylation sights. Both a neighbour-joining and a neighbour-net tree were compiled using MEGA 6 and SplitsTree 4 respectively. Three lineages groups were established with i.e. western group 1 and 2 and eastern group 1. The phylogenetic trees coincide with previous studies done on segment 10 of the BTV genome. These results also confirm that BTV-20, BTV-21 and BTV-23 are exotic to South Africa. BTV-2 demonstrated the ability of strains to cluster together, irrespective of their serotype providing evidence of genetic differences within serotypes. The presence of both competent midges and amplifying host, e.g. cattle and wildlife, contribute in the epidemiology of the disease, especially in episystems where distinct grouping of viruses co-evolved with respect to specific Culicoides species. The epidemiology of BTV is therefore likely to be largely influenced by the level of contact between livestock (and wildlife) and BTV-infected Culicoides species that influences both the distribution and the genetics of the virus.Dissertation (MSc)--University of Pretoria, 2014.tm2015Veterinary Tropical DiseasesMScUnrestricte

Sequence analysis and evaluation of the NS3/A gene region of bluetongue virus isolates from South Africa

Phylogenetic networks and sequence analyses allow for a more accurate understanding of the serotype, genetic relationships and the epidemiology of viruses. Based on gene sequences of the conserved segment 10 (NS3), bluetongue virus can be divided into five topotypes. In this molecular epidemiology study, segment 10 sequence data of 11 isolates obtained from the Virology Section of the Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, were analyzed and compared to sequence data of worldwide BTV strains available on GenBank. The consensus nucleotide sequences of NS3/A showed intermediate levels of nucleotide variation with a nucleotide identity ranging from 79.72% to 100%. All 11 strains demonstrated conserved amino acid characteristics. Phylogenetic networks were used to identify BTV topotypes. The phylogeny obtained from the nucleotide sequence data of the NS3/A-encoding gene presented three major and two minor topotypes. The clustering of strains from different geographical areas into the same group indicated spatial spread of the segment 10 genes, either through gene reassortment or through the introduction of new strains from other geographical areas via trade. The effect of reassortment and genetic drift on BTV and the importance of correct serotyping to identify viral strains are highlighted.The National Research Foundation and the Meat Industry Trust.http://link.springer.com/journal/7052017-04-30hb2016Veterinary Tropical Disease

Bagaza virus in Himalayan monal pheasants, South Africa, 2016–2017

Bagaza virus (BAGV) has not been reported in birds in South Africa since 1978. We used phylogenetic analysis and electron microscopy to identify BAGV as the likely etiology in neurologic disease and death in Himalayan monal pheasants in Pretoria, South Africa. Our results suggest circulation of BAGV in South Africa.UP Zoonotic Arbo- and Respiratory Virus Program income- generated funds. J. Steyn received doctoral scholarships from the National Research Foundation (grant no. 95175), the Meat Industry Trust (grant no. IT8114/98) and the Poliomyelitis Research Foundation (grant no. 15/112), as well as the US Centers for Disease Control and Prevention cooperative agreement with the University of Pretoria (no. 5 NU2GGH001874-02-00).http://wwwnc.cdc.gov/eidam2020Medical Virolog

At surface behaviour data of juvenile southern elephant seals from Marion Island between 2001 and 2006 with links to datasets

Marine mammals forage in dynamic environments characterized by variables that are continuously changing in relation to large-scale oceanographic processes. In the present study, behavioural states of satellite-tagged juvenile southern elephant seals (n = 16) from Marion Island were assessed for each reliable location, using variation in turning angle and speed in a state-space modelling framework. A mixed modelling approach was used to analyse the behavioural response of juvenile southern elephant seals to sea-surface temperature and proximity to frontal and bathymetric features. The findings emphasised the importance of frontal features as potentially rewarding areas for foraging juvenile southern elephant seals and provided further evidence of the importance of the area west of Marion Island for higher trophic-level predators. The importance of bathymetric features during the transit phase of juvenile southern elephant seal migrations indicates the use of these features as possible navigational cues

At surface behaviour at location on spot of southern elephant seals from Marion Island in 2004 with links to datasets

A novel classification system was applied to the sea level anomaly (SLA) environment around Marion Island. We classified the SLA seascape into habitat types and calculated percentage of habitat use of ten juvenile southern elephant seals (SES). Movements were compared to SLA and SLA slope values indicative of ocean eddy features. This classification provides a measure of habitat change due to seasonal fluctuations in SLA. Some of the seals made two migrations in different seasons, each of similar duration and proportions of potential foraging behaviour. The seals in this study did not use any intense eddy features, but their behaviours varied with SLA class. Potential foraging behaviour was positively influenced by negative SLA values (i.e. areas of below average sea surface height). Searching behaviour during the winter was more likely at eddy edges where high SLA slope values correlated with low SLA values. Though the seals did not forage within newly spawned eddies, they did forage near the sub-Antarctic front. Plankton and other biological resources transported by eddies formed at the subtropical convergence zone are evidently concentrated in this region and enhance the food chain there, forming a foraging ground for juvenile SES from Marion Island

The importance of seasonal sea surface height anomalies for foraging juvenile southern elephant seals

A novel classification system was applied to the sea level anomaly (SLA) environment around Marion Island. We classified the SLA seascape into habitat types and calculated percentage of habitat use of ten juvenile southern elephant seals (SES). Movements were compared to SLA and SLA slope values indicative of ocean eddy features. This classification provides a measure of habitat change due to seasonal fluctuations in SLA. Some of the seals made two migrations in different seasons, each of similar duration and proportions of potential foraging behaviour. The seals in this study did not use any intense eddy features, but their behaviours varied with SLA class. Potential foraging behaviour was positively influenced by negative SLA values (i.e. areas of below average sea surface height). Searching behaviour during the winter was more likely at eddy edges where high SLA slope values correlated with low SLA values. Though the seals did not forage within newly spawned eddies, they did forage near the sub-Antarctic front. Plankton and other biological resources transported by eddies formed at the subtropical convergence zone are evidently concentrated in this region and enhance the food chain there, forming a foraging ground for juvenile SES from Marion Island