Culicoides trap comparison in South Africa Gert Venter

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

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

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

Light trap comparisons Name: Miniature CDC Spain & Portugal Black light blue 15 cm 6 V Commercially available from the USA Light weight small 0. 8 Kg + 6 V battery (2. 2 Kg)

Light trap comparisons Name: Pirbright United Kingdom & Europe in the past 4 W, Incandescent white 220 V Not available anymore 2. 4 Kg Relative small collecting jar

Material & Methods (Light trap comparisons) Traps were deployed in either 3 replicates of a 4 X 4 or 2 replicates of a 5 X 5 randomized Latin square design Day/S ite 1 2 3 4 1 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 OP RIEB UK CDC 2 RIEB OP CDC UK 3 CDC UK RIEB OP 4 UK CDC OP RIEB 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. Day/S ite 1 1 RIEB UK OP CDC 2 UK RIEB CDC OP 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 3 CDC OP UK RIEB 4 OP CDC RIEB UK Day/S ite 2 1 3 2 4 3 4 UK RIEB OP CDC 2 OP UK CDC RIEB 3 Data were analysed using Genstat. Log transformation was used to stabilize the variance 1 CDC OP RIEB UK 4 RIEB CDC UK OP

RESULTS & DISCUSION (Light trap comparisons) SUMMER 643 374 Culicoides in 48 collections (Avg 13 403. 6) WINTER 4 931 Culicoides in 48 collections (Avg 102. 7) Significant differences in the average number of Culicoides collected per night by each of the 4 traps Comparisons were repeated in winter, when Culicoides numbers were low, the Onderstepoort trap still collected more midges. All 4 traps captured Culicoides CDC 26% RIEB 5% UK 6% CDC a 18% OP 63% RIEB ab 12% UK b 7% OP 63%

RESULTS & DISCUSION (Light trap comparisons) Summer: 8 -26 January 2008, 18 different Culicoides species were collected Trap OP RIEB CDC UK Max 97 290 19 152 31 977 12 617 Avg 33 950. 9 2 670. 1 (7. 9%) 13 732. 8 (40. 4%) 3 260. 8 (9. 6%) Min Non Cul : Cul 2 484 1: 11 174 1: 7 791 1: 6 90 1: 5 % C. imicola % C. enderleini 95. 0 a 4. 5 a 91. 8 7. 6 94. 3 b 5. 4 b 94. 5 ab 4. 6 ab 12 12 7 13 No of species Unique C. expectator (183) C. brucei (48) C. schultzei (92) C. nivosus (5) C. nevilli (12) C. similis (4) C. gulbenkiani (3)

RESULTS & DISCUSION (Light trap comparisons) Winter: 18 July – 8 August 2008, 8 different Culicoides species were collected Trap OP RIEB CDC UK Max 680 213 191 103 Avg 256. 5 49. 9 (19. 5%) ab 73. 9 (28. 8) a 30. 5 (11. 9) b Min Non Cul : Cul 6 1: 11 a 3 1: 10 a 1 1: 5 1 1: 2 % C. imicola % C. bolitinos 95. 0 a 2. 1 b 94. 5 a 3. 0 b 94. 8 a 2. 5 b 92. 9 a 2. 5 b No of species 8 5 7 5 53. 5 185. 8 106. 9 a Unique Reduction from summer C. pycnostictus 132. 6 a

Light trap comparisons Name: BG-Sentinel Mosquito Design for the collection of mosquitoes Black light blue 220 V/12 V Light weight, compact, collapsible 1. 4 Kg midges do not go through the fan

RESULTS & DISCUSION (Light trap comparisons) 2 repeats of a 5 X 5 Latin square: 14 -27 August 2008 31 358 Culicoides in 50 collections (Avg 627. 2)

RESULTS & DISCUSION (Light trap comparisons) Five traps, 50 collections, total of 14 species OP RIEB CDC UK BG-Sentinel Max 2 820 440 2 524 313 879 Avg 1 597. 9 (1) 134 (8. 4%) 807. 4 (50. 5%) 85. 1 (5. 3%) 511. 4 (32. 0%) Min 457 1: 12 15 1: 8 148 1: 10 1 1: 1 a 223 1: 1 a 97. 5 a 0. 6 a 0. 5 a 97. 4 a 0. 7 ab 0. 6 ab 0. 4 a 98. 0 a 0. 2 0. 7 abc 0. 4 a 93. 4 1. 2 ab 2. 2 1. 6 97. 4 a 0. 5 ab 0. 9 bc 0. 4 a 13 C. bedfordi (1) 6 10 10 12 C. neavei (1) Non Cul : Cul %C. imicola C. bolitinos C. nevilli C. magnus No of species

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. leucostictus C. nigripennis grp, C. pycnostictus, C. tropicalis and C. nivosus where gravid females and males, singly or when combined, predominated in all 4 traps

RESULTS & DISCUSSION (Light trap comparisons) Parous rates in C. imicola as determined by the four traps Onderstepoort CDC UK RIEB %Nulliparous 54. 5%a 52. 8% b 40. 6% 55. 9% ab %parous 39. 9% a 41. 5% b 48. 1% 41. 0% ab

RESULTS & DISCUSSION (Light trap comparisons) The relative abundance of males in 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 Onderstepoort CDC UK RIEB %Males C. imicola 5. 1% a 8. 1% 1. 4% C. enderleini 17. 6% 19. 8%a 18. 1% 12. 8%a

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

• Thank you