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Culicoides trap comparison in South Africa

Culicoides trap comparison in South Africa Gert Venter, Karien Labuschagne, Ina Hermanides, Daphney Majatladi, Solomon Boikanyo. Culicoides trap comparison in South Africa. 4 traps summer (high abundance) 4 traps winter (low abundance) 5 traps spring. CDC. UK. OP. RIEB.

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Culicoides trap comparison in South Africa

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  1. Culicoides trap comparison in South AfricaGert Venter, Karien Labuschagne, Ina Hermanides, Daphney Majatladi, Solomon Boikanyo

  2. Culicoides trap comparison in South Africa • 4 traps summer (high abundance) • 4 traps winter (low abundance) • 5 traps spring

  3. CDC UK OP RIEB

  4. Light trap comparisons Name: ONDERSTEPOORT South Africa 8W, Black light blue 30cm 220V Relative robust and heavy 4 Kg

  5. Light trap comparisons Name: RIEB 2000-2006 France 4W, UV 15cm 12V Relative light weight and compact 1 Kg + 12V car battery Relative small collecting jar

  6. Light trap comparisons Name: Miniature CDC Spain & Portugal Black light blue 15cm 6V Commercially available from the USA Light weight small 0.8 Kg + 6V battery (2.2 Kg)

  7. Light trap comparisons Name: Pirbright United Kingdom & Europe in the past 4W, Incandescent white 220V Not available anymore 2.4 Kg Relative small collecting jar

  8. Material & Methods (Light trap comparisons) Day/Site 1 2 3 4 Day/Site 1 2 3 4 Day/Site 1 2 3 4 1 OP RIEB UK CDC 1 UK RIEB OP CDC 1 RIEB UK OP CDC 2 OP UK CDC RIEB 2 RIEB OP CDC UK 2 UK RIEB CDC OP 3 CDC UK RIEB OP 3 CDC OP RIEB UK 3 CDC OP UK RIEB 4 RIEB CDC UK OP 4 UK CDC OP RIEB 4 OP CDC RIEB UK Traps were deployed in either 3 replicates of a 4X4 or 2 replicates of a 5X5 randomized Latin square design The advantage being that treatment means were independent of effects due to sites or occasion and, as only one treatment occupied a site on any occasion trap interaction was avoided Traps were operated from dusk to dawn under the eves of a stable housing cattle at the ARC-OVI. Nights with trap failure were repeated the following night. Large collections were sub-sampled and all species were classified according to abdominal pigmentation into: Nulliparous (unpigmented) females Parous (pigmented) females Gravid females Freshly bloodfed females and males Data were analysed using Genstat. Log transformation was used to stabilize the variance

  9. RESULTS & DISCUSION (Light trap comparisons) WINTER 4 931 Culicoides in 48 collections (Avg 102.7) Comparisons were repeated in winter, when Culicoides numbers were low, the Onderstepoort trap still collected more midges. All 4 traps captured Culicoides SUMMER 643 374 Culicoides in 48 collections (Avg 13 403.6) Significant differences in the average number of Culicoides collected per night by each of the 4 traps UK 6% UK b 7% CDC a 18% CDC 26% RIEB 5% OP 63% RIEB ab 12% OP 63%

  10. RESULTS & DISCUSION (Light trap comparisons) Summer: 8-26 January 2008,18 different Culicoides species were collected

  11. RESULTS & DISCUSION (Light trap comparisons) Winter: 18 July – 8 August 2008, 8 different Culicoides species were collected

  12. Light trap comparisons Name: BG-Sentinel Mosquito Design for the collection of mosquitoes Black light blue 220V/12V Light weight, compact, collapsible 1.4 Kg midges do not go through the fan

  13. RESULTS & DISCUSION (Light trap comparisons) 2 repeats of a 5X5 Latin square: 14-27 August 2008 31 358 Culicoides in 50 collections (Avg 627.2)

  14. RESULTS & DISCUSION (Light trap comparisons)Five traps, 50 collections, total of 14 species

  15. RESULTS & DISCUSSION (Light trap comparisons) • As transovarial transmission of orbiviruses are not known to occur in Culicoides the number of parous individuals is of importance in determining the potential vector status of a specific population. I.e. only parous females are considered as being infected • All traps indicated that males, freshly bloodfed and gravid females, especially of C. imicola, were less attracted to light traps than parous and nulliparous females • This was not true for C. exspectator, C. leucostictusC. nigripennis grp, C. pycnostictus, C. tropicalis and C. nivosus where gravid females and males, singly or when combined, predominated in all 4 traps

  16. RESULTS & DISCUSSION (Light trap comparisons) Parous rates in C. imicola as determined by the four traps %Nulliparous %parous Onderstepoort 54.5%a 39.9% a CDC 52.8% b 41.5% b UK 40.6% 48.1% RIEB 55.9% ab 41.0% ab

  17. RESULTS & DISCUSSION (Light trap comparisons) The relative abundance of malesin collections may indicate nearby breeding sites and the collection of males in winter may indicate continuous breeding Abundance of male C. imicola and C. enderleini as determined by the four traps %Males C. imicola C. enderleini Onderstepoort 5.1% a 17.6% CDC 5.1% a 19.8%a UK 8.1% 18.1% RIEB 1.4% 12.8%a

  18. DISCUSSION / CONCLUSIONS (Light trap comparisons) • The Onderstepoort trap will increase monitoring sensitivity where vector abundances are low and it will collect more live midges for vector competence and other laboratory studies • It must be taken into consideration that when a light trap is placed in the immediate vicinity of animals, it intercepts only a portion of the active blood seeking females. The exact size of this portion is not known but is deemed to be <0.0001% • Light traps do not attract male and/or blood fed and gravid females • To facilitate comparison of data and data sharing, standard techniques for measuring the variables of vectorial capacity should be developed and adopted • Despite the a great variety of factors that can influence the numbers of Culicoides midges collected with light traps it is still the most practical way to determine vector abundance • It will be essential that biases in trapping methods be measured and that trapping methods be evaluated against each other

  19. Thank you

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