Labuschagne_343-347.indd Culicoides biting midges are responsible for the trans mission of several globally significant arbovi- ruses of livestock, along with many other pathogens of local importance (Linley 1985; Mellor, Boorman & Baylis, 2000; Meiswinkel, Venter & Nevill 2004). In sub-Saharan Africa, they are of interest primarily as vectors of bluetongue virus (BTV) and African horse sickness virus (AHSV), which cause two devastat- ing diseases of ovinae and equidae, respectively. While the impact of both these viruses in South Africa is limited, because of high endemic immunity in those hosts in which they commonly cause dis- ease and the use of polyvalent live attenuated vac- cines, sporadic and severe outbreaks of these dis- eases still occur (Meiswinkel et al. 2004). Outbreaks of African horse sickness (AHS) in 1999 and 2004 in the surveillance zone of the declared AHS-free area in the Stellenbosch district had considerable financial implications and on both occasions led to a 2-year embargo on the export of horses from South Africa (Venter, Koekemoer & Paweska 2006). Of the approximately 120 species of Culicoides identified in southern Africa (Meiswinkel, unpublished data 1996), the vast majority remain uninvestigated as potential vectors of disease. However, Culicoides imicola Kiefer, 1913 and Culicoides bolitinos Meis- winkel, 1989 two species that are closely associated with both livestock and game (Meiswinkel 1989, 1995) have been identified as primary candidates for this role. Both AHSV and BTV have been shown to replicate under laboratory conditions to what are presumed to be transmissible levels in these spe- 343 Onderstepoort Journal of Veterinary Research, 74:343–347 (2007) RESEARCH COMMUNICATION Culicoides biting midges at the National Zoological Gardens of South Africa K. LABUSCHAGNE1, L.J. GERBER2, I. ESPIE3 and S. CARPENTER4 ABSTRACT LABUSCHAGNE, K., GERBER, L.J., ESPIE, I. & CARPENTER, S. 2007. Culicoides biting midges at the National Zoological Gardens of South Africa. Onderstepoort Journal of Veterinary Research, 74: 343–347 Culicoides biting midges (Diptera: Ceratopogonidae) are responsible for the transmission of a large number of pathogens to livestock and wild animals. In this study the presence of the genus, using light traps based at four different sites within the National Zoological Gardens of South Africa, was inves- tigated during 2002–2004. In total, 37 species were recorded, including large numbers of Culicoides imicola Kieffer, 1913, which is responsible for the transmission of economically important arboviruses in South Africa, Europe, Middle and Far East. These results are discussed with reference to the wider Culicoides fauna in the Onderstepoort area of South Africa, their vector competence as well as bio- security at the National Zoological Gardens. Keywords: Abundance, biosecurity, Culicoides, light trap, National Zoological Gardens, survey ¹ Agricultural Research Council, Onderstepoort Veterinary Insti- tute, Division of Entomology, Private Bag X05, Onderste poort, 0110 South Africa. E-mail: labuschagnek@arc.agric.za 2 Tshwane University of Technology, Department Biomedical Sciences, Private Bag X680, Pretoria, 0001 South Africa 3 National Zoological Gardens of South Africa, Boom Street, P.O. Box 754, Pretoria, 0001 South Africa 4 Institute of Animal Health, Pirbright Laboratory, Pirbright, Sur- rey, GU24-0NF UK Accepted for publication 19 March 2007—Editor 344 Culicoides biting midges at the National Zoological Gardens of South Africa cies (Venter, Paweska, Van Dijk, Mellor & Tabach- nick 1998; Venter, Graham & Hamblin 2000). In this paper, the results of a light trap-based survey carried out over 2 years in which the Culicoides spp. occurring in the zoo is presented and their biosecu- rity risk is defined. Given the movement of animals as part of breeding programmes or loans into coun- tries with a greater clinical disease risk from e.g. bluetongue (BT) or AHS than that in South Africa, biosecurity practices are important to minimize the risk of accidentally importing these viruses/ diseas- es as happened following the importation of AHSV- infected zebras from Namibia into Spain (Lubroth 1988). Additionally, methods to minimize the num- bers of Culicoides breeding in this habitat are sug- gested. The National Zoological Gardens is located in cen- tral Pretoria (25°45’ S; 28°11’ E) and its inhabitants are isolated from other game and large livestock in the general area by the surrounding urban develop- ment, although poultry and some small livestock such as goats are kept. The zoo covers an area of approximately 80 ha and houses over 100 exotic and indigenous species of mammals and over 160 bird species. The survey was carried out from August 2002 to August 2004 using 220V black light down- draught light traps (Meiswinkel et al. 2004) placed at four sites on the premises of the zoo (Fig. 1). The sites were selected in close proximity of animal spe- cies possessing the potential of filarial, protozoa and viral transmission (Karstad 1979; Meiswinkel et al. 2004). The sites chosen were at the Cape buf- falo (Syncerus caffer), African elephant (Loxodonta africana), white rhinoceros (Ceratotherium simum)/ black-faced impala (Aepyceros melampus petersi) enclosures and the walk-through aviary. Light traps were operated once weekly from dusk until dawn. Collections were made into a 1 % Savlon (containing Clorhexidane gluconate 0.3 g/100 ml and Cetrimide 3.0 g/100 ml [Johnson & Johnson, SA]) -water solution and transferred the following morning to 80 % alcohol for storage purposes. All the collections containing more than 500 Culicoides specimens were sub-sampled using the method of Van Ark & Meiswinkel (1992). Culicoides was identi- fied to species level by examination of wing mark- ings (Meiswinkel 1996), with the exception of the 150 m N S W O FIG. 1 Plan of the National Zoological Gardens of South Africa, Pretoria, South Africa showing placement of light traps. (1) Cape buffalo enclo- sure, (2) African elephant enclosure, (3) walk-through aviary and (4) white rhinoceros/black-faced impala enclosure Culicoides nigripennis Carter, Ingram and Macfie, 1920 and Culicoides accra- ensis Carter, Ingram and Macfie, 1920 species complexes which are extreme ly difficult to separate accurately based on their mor phology. In order to prevent a bias in numbers of the different species at each site, comparisons of the number and species present were made only between those days when all four traps were in operation. Ninety samples from each site were compared and used for analysis. In this subset of 360 samples a total of 478 040 midges was collected and iden- tified, representing a total of 33 species (Table 1). The trap based at the elephant enclosure caught the greatest total num- ber of Culicoides, representing some 28 different species, followed by the white rhinoceros/black-faced impala site (29 species), the buffalo site (17 species) and the aviary (12 species) (Table 1). Pro portionately, C. imicola was by far the most common ly trapped species, con- stituting more than 95 % of all midges caught at the buffalo and elephant sites and 67 % at the white rhinoceros/black- faced impala site, where Culi coides cor- 345 K. LABUSCHAGNE et al. nutus de Meillon, 1937 was also comparatively abundant (19 %) (Table 1). The avi ary site, how ever, was dominated by both Culicoides leucostictus Kief- fer, 1911 (48 %) and C. nigripennis sensu lata (43 %) with C. imicola comprising only 1.5 % of the total catch. This highlighted the host preferences of C. imi cola for larger mammals and increases the ca- pacity of this species being a vector of AHS and BT viruses. The abundance and diversity of the Culicoides fau- na found at the National Zoological Gardens closely correlates with the results of a similar earlier study near livestock in the Onderstepoort area (25°39’ S; 28°11’ E) north of Pretoria (Venter, Meiswinkel, Nevill & Edwards 1996a). As in the case at Onder- stepoort, the presence of substantial populations of C. imicola is likely to pose the most easily identifi- able threat from a biosecurity point of view, espe- cially as light-trap catches tend to represent only a small proportion of the populations sampled. As lar- vae, this species primarily utilizes a wide range of organically enriched habitats and population num- bers could potentially be reduced by chemical treat- ment (Apperson 1975; Holbrook & Agun 1984), or rapid removal (Bishop, Mckenzie, Spohr & Barchia 2005) or dilution of animal waste. The efficiency of habitat removal techniques for African species of TABLE 1 Culicoides spp. recovered from 360 black light trap collections in the National Zoological Gardens, South Africa during August 2002 to August 2004 Species Mean (maximum) no. Culicoides caught/trap night Buffalo Elephant Aviary Rhinoceros/impala C. imicola 203.7 (8 027) 3 033.0 (65 520) 0.1 (10) 1 272.4 (18 288) C. enderleini 9.1 (462) 47.4 (1 386) 91.8 (1 703) C. bolitinos 3.9 (165) 9.5 (86) < 0.1 (1) 5.1 (103) C. cornutus 1.1 (29) 4.3 (54) 0.1 (2) 363.3 (4 699) C. zuluensis 1.0 (35) 9.9 (75) 18.2 (184) C. nigripennis s.l. 0.8 (24) 9.7 (109) 3.8 (268) 40.2 (650) C. nivosus 0.5 (7) 11.3 (126) 0.2 (5) 21.9 (490) C. leucostictus 0.3 (4) 33.3 (325) 4.3 (38) 58.7 (755) C. pycnostictus 0.3 (8) 20.2 (254) 0.3 (6) 19.5 (209) C. magnus 0.1 (3) 0.9 (15) 0.1 (4) C. subschultzei 0.1 (3) 0.2 (10) 2.1 (54) C. brucei 0.1 (3) 0.6 (10) 0.2 (22) C. gulbenkiani 0.1 (5) < 0.1 (2) < 0.1 (1) C. nevilli 0.1 (2) 0.6 (33) 0.5 (31) C. engubandei < 0.1 (1) < 0.1 (1) 0.3 (8) C. huambensis < 0.1 (1) C. tropicalis < 0.1 (1) 0.3 (10) 0.1 (5) C. sp. # 54 0.3 (8) 0.2 (14) C. sp. # 94 < 0.1 (3) < 0.1 (3) C. accraensis s.l. 0.9 (52) 0.1 (1) < 0.1 (5) C. albopunctatus < 0.1 (2) < 0.1 (5) C. nr. angolensis < 0.1 (3) C. bedfordi 0.4 (13) < 0.1 (1) 0.5 (10) C. coarctatus 0.2 (14) 0.1 (8) C. dekeyseri < 0.1 (4) C. eriodendroni < 0.1 (2) C. exspectator 0.4 (7) 0.4 (15) C. sp. # 107 < 0.1 C. loxodontis < 0.1 (1) C. neavei 0.5 (10) 0.4 (14) C. ravus 0.1 (10) < 0.1 (3) 0.3 (31) C. schultzei < 0.1 (1) C. similis 0.5 (10) < 0.1 (2) 0.6 (15) Total 221.0 3 184.5 8.9 1 897.1 346 Culicoides biting midges at the National Zoological Gardens of South Africa Culicoides is unknown. In the case of this isolated habitat, modification to the habitat could be consid- ered. This must, however, be an ongoing process given that re-colonization of areas from other parts of the zoo, or from beyond the zoo’s boundaries (suburban areas), would appear to be likely given the similarities between the Culicoides fauna in the zoo and that of the local (Onderstepoort) area. Chemical treatment can be effective but unfortu- nately non-target organisms are often also killed (Holbrook & Agun 1984). The biosecurity risk posed by species of Culicoides other than C. imicola present in the zoo remains un- clear. While C. bolitinos is known to possess a sub- stantially greater vector competence for both BTV and AHSV than C. imicola (Venter et al. 1998, 2000), it was found in relatively low abundance, and should be relatively easy to control by more rapid removal (Bishop et al. 2005) or treatment of dung (Standfast, Muller & Wilson 1984) from animal holding areas as it is known to breed directly in the dung of large her- bivores (Meiswinkel 1989). The vector competency for arboviruses of Culicoides enderleini Cornet & Brunhes, 1994, the second most common species at the buffalo and elephant sites and Culicoides zulu ensis de Meillon, 1936, is currently unknown though it was shown that C. zu- luensis is susceptible to oral infection with the live attenuated vaccine strains of AHSV (Paweska, Prinsloo & Venter 2003). These species are com- mon and widespread across South Africa and al- though the former appears to utilize a wide range of hosts (Braverman & Phelps 1981; Meiswinkel et al. 2004), which may mitigate against it being an effi- cient vector, it was identified as a potential risk in a previous study (Venter, Nevill, Van der Linde 1996b). Also of interest are the large numbers of C. cornu- tus at the white rhinoceros/black-faced impala en- closure. Little is known of this species’ vector com- petence for arboviruses or other pathogens, its host preference or its larval habitat requirements. However, C. cornutus is very closely related to Culicoides sonorensis Wirth and Jones, 1957, the vector of BTV in North America and C. cornutus is often the dominant species collected in the BT en- zootic area of Kenya (Glick 1990). There fore, this species remains an unknown risk in terms of dis- ease transmission. Of the remaining species, C. ni- gripennis sensu lata dominated the aviary fauna, but was also found in smaller numbers around all the mammal-based traps. Again, little is known re- garding this group’s competency for transmitting ar- boviruses. However, their apparent host preference for birds (or at least a very wide host preference) would appear to preclude them from representing a major biosecurity risk for the transmission of mam- malian arboviruses, although not of protozoa. At least ten species of protozoa are transmitted by Culicoides spp. to birds (Linley 1985). Imports of sub-clinically infected zoo animals into areas with susceptible hosts for arboviruses have caused outbreaks of a wide range of diseases caused by arboviruses, e.g. the outbreak of AHS in Spain from 1987–1990, which was initiated by the importa- tion of infected zebras (Lubroth 1988). The difficulty of detecting diseases, such as BT and AHS at ports of entry into countries has emphasized the need for routine screening and quarantine. However, these procedures are expensive but quarantine proce- dures could possibly be reduced, especially when captive bred stock is being relocated by reducing the chances of infection with certain arboviruses in the first place, through the methods suggested in this communication. The major difficulty in accom- plishing this process is ensuring that the methods employed in vector control remain ongoing, which, barring the most isolated cases, will require consid- erable effort in endemic areas of arbovirus distribu- tion. ACKNOWLEDGEMENTS The authors thank the personnel of the National Zoological Gardens for all their support and assis- tance. The survey was funded by the Onderstepoort Veterinary Institute (ARC-OVI) and the European Union (EU contract: QLK2-2001-01722 on the de- velopment of a safe, efficacious bluetongue virus vaccination strategy for Europe). We thank Karin Kappmeier Green and Gert Venter for helpful com- ments on drafts of this manuscript. REFERENCES APPERSON, C.S. 1975. Biological activity of insecticides against Culicoides variipennis (Coquillett) (Diptera: Ceratopogonidae). Proceedings of the 43rd Annual Conference of the Mosquito Control Association: 118–119. BISHOP, A.L., MCKENZIE, H.J., SPOHR, L.J. & BARCHIA, I.M. 2005. Interactions between dung beetles (Coleoptera: Scarabaeidae) and the arbovirus vector Culicoides brevitar- sis Kieffer (Diptera: Ceratopogonidae). Australian Journal of Entomology, 44:8996. BRAVERMAN, Y. & PHELPS, R.J. 1981. Species composition in samples of Culicoides (Diptera: Ceratopogonidae) collected near Salisbury, Zimbabwe in 1976–77. Journal of the Ento- mological Society of Southern Africa, 44:315–323. 347 K. LABUSCHAGNE et al. GLICK, J.J. 1990. Culicoides biting midges (Diptera: Cerato po go- nidae) of Kenya. Journal of Medical Entomology, 27:85–195. HOLBROOK, F.R. & AGUN, S.K. 1984. Field trials of pesticides to control larval Culicoides variipennis (Ceratopogonidae). Mosquito News, 44:233–236. KARSTAD, L. 1979. A partly annotated bibliography on infec- tions, parasites, and diseases of African wild animals. Inter- national Development Research Centre, Canada: 1–111. LINLEY, J.R. 1985. Biting midges (Diptera: Ceratopogonidae) as vectors of nonviral animal pathogens. Journal of Medical Entomology, 22:589–599. LUBROTH, J. 1988. African horse sickness and the epizootic in Spain 1987. Equine Practise, 10:26–33. MEISWINKEL, R. 1989. Afrotropical Culicoides: A redescription of C. (Avaritia) imicola Kieffer, 1913 (Diptera: Ceratopogo ni- dae) with description of the closely allied C. (A) bolitinos sp. nov. reared from dung of the African buffalo, blue wildebeest and cattle in South Africa. Onderstepoort Journal of Veter i- nary Research, 56:23–39. MEISWINKEL, R. 1995. Afrotropical Culicoides: biosystematics of the Imicola group, subgenus Avaritia (Diptera: Cerato po- gonidae). With special reference to the epidemiology of African horse sickness. M.Sc. thesis, University of Pretoria. MEISWINKEL, R., VENTER, G.J. & NEVILL, E.M. 2004. Vectors: Culicoides spp., in Infectious diseases of livestock, 2nd ed, edited by J.A.W. Coetzer & R.C. Tustin. Cape Town: Oxford University Press. MELLOR, P.S., BOORMAN, J. & BAYLIS, M. 2000. Culicoides biting midges: Their role as arbovirus vectors. Annual Review of Entomology, 45:307–340. PAWESKA, J.T., PRINSLOO, S., VENTER, G.J. 2003. Oral sus- ceptibility of South African Culicoides species to live-attenu- ated serotype-specific vaccine strains of African horse sick- ness virus (AHSV). Medical and Veterinary Entomology, 15: 436–447. STANDFAST, H.A., MULLER, M.J. & WILSON, D.D. 1984. Mor- tality of Culicoides brevitarsis (Diptera: Ceratopogonidae) fed on cattle treated with Ivermectin. Journal of Medical Ento- mology, 77:419–421. VAN ARK, H. & MEISWINKEL, R. 1992. Sub-sampling of large light trap catches of Culicoides (Diptera: Ceratopogonidae). Onderstepoort Journal of Veterinary Research, 59:183–189. VENTER, G.J., GRAHAM, S.D. & HAMBLIN, C. 2000. African horse sickness epidemiology: vector competence of South African Culicoides species for African horse sickness virus serotypes 3, 5 and 8. Medical and Veterinary Entomology, 14:245–250. VENTER, G.J., KOEKEMOER, J.J.O. &. PAWESKA, J.T. 2006. Investigations on outbreaks of African horse sickness in the surveillance zone of South Africa. Revue scienfique et tech- nique, Office International des Epizooties, 25:1097–1109. VENTER, G.J., MEISWINKEL, R., NEVILL, E.M. & EDWARDES, M. 1996a. Culicoides (Diptera: Ceratopogonidae) associated with livestock in the Onderstepoort area, Gauteng, South Africa as determined by light-trap collections. Onderstepoort Journal of Veterinary Research, 63:315–325. VENTER, G.J., NEVILL, E.M. & VAN DER LINDE, T.C. DE K. 1996b. Geographical distribution and relative abundance of stock-associated Culicoides species (Diptera: Ceratopogoni- dae) in southern Africa, in relation to their potential as viral vectors. Onderstepoort Journal of Veterinary Research, 63: 25–38. VENTER, G.J., PAWESKA, J.T., VAN DIJK, A.A., MELLOR, P.S. & TABACHNICK, W.J. 1998. Vector competence of Culicoi- des bolitinos and C. imicola (Diptera: Ceratopogonidae) for South African bluetongue virus serotypes 1, 3 and 4. Medical and Veterinary Entomology, 12:101–108.