Culicoides trap comparison in South Africa
Gert Venter, Karien Labuschagne, Ina Hermanides, Daphney Majatladi, Solomon Boikanyo
• 4 traps summer (high abundance)• 4 traps winter (low abundance)• 5 traps spring
Culicoides trap comparison in South Africa
CDCUK
OPRIEB
Name: ONDERSTEPOORTSouth Africa8W, Black light blue 30cm220VRelative robust and heavy4 Kg
Light trap comparisons
Name: RIEB2000-2006 France4W, UV 15cm12VRelative light weight and compact1 Kg + 12V car batteryRelative small collecting jar
Light trap comparisons
Name: Miniature CDCSpain & PortugalBlack light blue 15cm6VCommercially available from the USALight weight small0.8 Kg + 6V battery (2.2 Kg)
Light trap comparisons
Name: PirbrightUnited Kingdom & Europe in the past4W, Incandescent white220VNot available anymore2.4 KgRelative small collecting jar
Light trap comparisons
RIEBOPCDCUK4
OPRIEBUKCDC3
UKCDCOPRIEB2
CDCUKRIEBOP1
4321Day/Site
4321
Day/Site
UKRIEBCDCOP4
RIEBUKOPCDC3
OPCDCRIEBUK2
CDCOPUKRIEB1
OPUKCDCRIEB4
UKRIEBOPCDC3
RIEBCDCUKOP2
CDCOPRIEBUK1
4321Day/Site
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
Material & Methods (Light trap comparisons)
SUMMER643 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
RESULTS & DISCUSION (Light trap comparisons)
OP63%
OP63%
UK b7%
UK6% CDC a
18%CDC26%
RIEB ab12%
RIEB5%
WINTER4 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
RESULTS & DISCUSION (Light trap comparisons)
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%)
MinNon Cul : Cul
2 4841:11
1741:7
7911:6
901:5
% C. imicola% C. enderleini
95.0 a4.5 a
91.87.6
94.3 b5.4 b
94.5 ab4.6 ab
No of species 12 12 7 13
Unique C. expectator (183)C. schultzei (92)C. nivosus (5)
C. brucei (48) C. nevilli (12)C. similis (4)C. gulbenkiani (3)
Summer: 8-26 January 2008,18 different Culicoides species were collected
Trap
RESULTS & DISCUSION (Light trap comparisons)
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
MinNon Cul : Cul
61:11 a
31:10 a
11:5
11:2
% C. imicola% C. bolitinos
95.0 a2.1 b
94.5 a3.0 b
94.8 a2.5 b
92.9 a2.5 b
No of species 8 5 7 5
Unique C. pycnostictus
Reduction from summer
132.6 a 53.5 185.8 106.9 a
Winter: 18 July – 8 August 2008, 8 different Culicoides species were collected
Trap
Name: BG-Sentinel MosquitoDesign for the collection of mosquitoesBlack light blue220V/12VLight weight, compact, collapsible1.4 Kgmidges do not go through the fan
Light trap comparisons
CDC26% a
OP51%
RIEB4% b
UK3% b
BG16% a
2 repeats of a 5X5 Latin square: 14-27 August 2008 31 358 Culicoides in 50 collections (Avg 627.2)
RESULTS & DISCUSION (Light trap comparisons)
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%)
MinNon Cul : Cul
4571:12
151:8
1481:10
11:1 a
2231:1 a
%C. imicolaC. bolitinosC. nevilliC. magnus
97.5 a0.6 a0.6 a0.5 a
97.4 a0.7 ab0.6 ab0.4 a
98.0 a0.2
0.7 abc0.4 a
93.41.2 ab
2.21.6
97.4 a0.5 ab0.9 bc0.4 a
No of species
13C. bedfordi (1)
6 10 10 12C. neavei (1)
RESULTS & DISCUSION (Light trap comparisons)
Five traps, 50 collections, total of 14 species
• 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
%Nulliparous %parousOnderstepoort 54.5%a 39.9% aCDC 52.8% b 41.5% bUK 40.6% 48.1%RIEB 55.9% ab 41.0% ab
RESULTS & DISCUSSION (Light trap comparisons)
0
10000
20000
OP RIEB CDC UK
C. imicola nulliparous C. imicola parous
0
10000
20000
30000
OP RIEB CDC UK
Nu
mb
er
co
llecte
d
Avg C. imicola Avg males
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
%MalesC. imicola C. enderleini
Onderstepoort 5.1% a 17.6% CDC 5.1% a 19.8%aUK 8.1% 18.1%RIEB 1.4% 12.8%a
RESULTS & DISCUSSION (Light trap comparisons)
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