Abstract
The ticks Amblyomma hebraeum and A. variegatum are the main vectors of heartwater, a disease of ruminants caused by Cowdria ruminantium, in the agricultural areas of Zimbabwe. At present, A. hebraeum is widely distributed in the dry southern lowveld, and occurs in at least seven foci in the higher rainfall highveld. Amblyomma variegatum occurs in the Zambezi valley and surrounding dry lowveld areas in the northwest. The distribution of A. hebraeum has changed considerably over the past 70 years, while that of A. variegatum appears to have remained fairly static. The distribution patterns of both species in Zimbabwe display anomalous features; the ticks occur in areas of lowest predicted climatic suitability for survival and development and in areas where the densities of cattle, the most important domestic host, are lowest. The only factor favouring the survival of the species in the lowveld habitats in which they occur is the presence of alternative wildlife hosts for the adult stage. Their absence from more climatically favourable highveld habitats appears to have been the result of intensive acaricide treatment of cattle over a long period and a historic absence of significant numbers of wildlife hosts. Eradication of A. hebraeum and A. variegatum by intensive acaricide treatment of cattle can be achieved in the absence of significant numbers of alternative hosts, because of the long attachment and feeding periods of the adults of these tick species. However, eradication becomes impossible when alternative hosts for the adult stage are present, because a pheromone emitted by attached males attracts the unfed nymphal and adult stages to infested hosts. The unfed ticks are not attracted to uninfested hosts, such as acaricide-treated cattle.
Regular acaricide treatment of cattle is expensive and so, for economic reasons, the Government of Zimbabwe is no longer enforcing a policy of strict tick control. It is likely that reduced tick control will result in the spread of Amblyomma ticks to previously uninfested areas. Added to this, recent introductions of various wildlife species to highveld commercial farming areas have created conditions in which the ticks could become established in higher rainfall areas. Amblyomma hebraeum is more likely to spread than A. variegatum, because its adults parasitize a wider range of wildlife hosts (warthogs, medium to large-sized antelope, giraffe, buffalo and rhinoceros), whereas adults of A. variegatum appear to be largely restricted to one wildlife species (buffalo) in Zimbabwe, the distribution of which is now confined to very limited areas of the country, as part of foot and mouth disease control measures. A model to predict the rate of spread of A. hebraeum through the highveld is described.
Possible control options for dealing with the spread of Amblyomma ticks and heartwater to previous unaffected highveld areas, include (1) continuation of intensive acaricide treatment of cattle to prevent the spread, (2) establishment of a buffer zone of intensive tick control around affected areas to contain the spread and (3) allow the spread to occur and control heartwater by means of immunization. An economic analysis to determine the costs and benefits of the control options, which takes into account the development of Amblyomma-specific tick control technologies and improved heartwater vaccines, is recommended.
This is a preview of subscription content, access via your institution.
References
Asselbergs, M.J. and Lopes Pereira, C.M., 1989. Damage by Amblyomma hebraeum in local (Bos indicus) cattle in Mozambique. Proc. 6th Int. Conf. Inst. Trop. Vet. Med., University of Utrecht, pp. 197–200.
Bell, R.H.V., 1982. The effect of soil nutrient availability on community structure in African ecosystems. In: Ecology of Tropical Savanna, (Huntley, B.J. & Walker, B.H. eds), Springer Verlag, Berlin, 193–216.
Booth, T.H., Stein, J.A., Hutchinson, M.F. and Nix, H.A., 1990. Identifying areas within a country for particular tree species: An example using Zimbabwe. Int. Tree Crops J., 6:1–16.
Centurier, V.C. and Klima, R., 1978. Ein Beitrag zur Kenntnis der Biologie von Amblyomma variegatum (Fabricius). Zeit. Agnew. Entomol., 87:131–142.
Condy, J.B., 1979. A history of foot and mouth disease in Rhodesia. Rhod. Vet. J., 10:2–10.
de, Vries, N., Mahan, S.M., Ushewokunze-Obatolu, U., Norval, R.A.I. and Jongejan, F., 1993. Correlation between antibodies to Cowdria ruminantium (Rickettsiales) in cattle and the distribution of Amblyomma vector ticks in Zimbabwe. Exp. Appl. Acarol. 17, 799–810.
Du, Plessis, J.L., Loock, P.J. and Lüdemann, C.J.F., 1992. Adult Amblyomma hebraeum burdens and heartwater endemic stability in cattle. Onderstepoort J. Vet. Res., 59:75–89.
Garris, G.I., 1984. Colonization and life cycle of Amblyomma variegatum (Acari: Ixodidae) in the laboratory in Puerto Rico. J. Med. Entomol., 21:86–90.
Hoogstraal, H., 1956. African Ixodoidea. I. Ticks of the Sudan (with special reference to Equatoria Province and with preliminary reviews of the genera Boophilus, Margaropus and Hyalomma). Res. Rep. NM 005 050.29.07 U.S. Govt. Dep. of Navy, Bur. Med. Surg., Washington, D.C., 1101 pp.
Hooper Sharpe G.C., 1935. Report of the Chief Veterinary Surgeon for the year 1935. Salisbury, Southern Rhodesia. 16pp.
Horak, I.G. and Williams, E.J., 1986. Parasites of domestic and wild animals in South Africa. VXIII. The crowned guinea fowl (Numida meleagris), and important host of immature ixodid ticks. Onderstepoort J. Vet. Res., 53:119–122.
Horak, I.G., Maclvor, DE.F., Petney, T.N. and de, Vos, V. 1987. Some avian and mammalian hosts of Amblyomma hebraeum and Amblyomma marmoreum (Acari: Ixodidae). Onderstepoort J. Vet. Res., 54:397–400.
Jack, R.W., 1942. Ticks infesting domestic animals in Southern Rhodesia. Rhod. Agric. J., 39:95–109.
Jooste, K.F., 1967. Newsletter Vet. Res. Lab., Salisbury, Rhodesia. 2:34.
Lawrence, J.A., Foggin, C.M. and Norval, R.A.I., 1980. The effects of war on the control of diseases of livestock in Rhodesia (Zimbabwe). Vet. Rec., 107:82–85.
Lessard, P., L'Eplattenier, R., Norval, R.A.I., Kundert, K., Dolan, T.T., Croze, H., Walker, J.B., Irvin, A.D. and Perry, B.D., 1990. Geographical information systems for studying the epidemiology of cattle diseases caused by Theileria parva. Vet. Rec., 126:225–262.
MacLeod, J. and Mwanaumo, B., 1978. Ecological studies of ixodid ticks (Acari: Ixodidae) in Zambia. IV. Some anomalous infestation patterns in the northern and eastern regions. Bull. Entomol. Res., 68:409–429.
Mahan, S.M., Andrew, H.R., Tebele, N., Burridge, M.J. and Barbet, A.F., 1994. Immunisation of sheep with inactivated Cowdria ruminantium provides protection against heartwater. Res. Ver. Sci. (In press).
Martinez, D., Maillard, J.C., Sheikboudou, C. and Coisne, S., 1993. Protection of goats against heartwater with inactivated elementary bodies of Cowdria ruminantium. Revue Elev. Med. Vet.Pay. Trop., 46, 229.
Matthysse, J.G. and Colbo, M.H., 1987. The ixodid ticks of Uganda together with species pertinent to Uganda because of their present known distribution. Entomol. Soc. Am., College Park, Maryland. 426pp.
Meltzer, M.I. and Norval, R.A.I., 1993. Evaluating the economic damage threshold for bont tick (Amblyomma hebraeum) control in Zimbabwe. Exp. Appl. Acarol., 17:171–185.
Norval, R.A.I., 1974. The life cycle of Amblyomma hebraeum Koch, 1944 (Acarina: Ixodidae). J. Ent. Soc. Sth. Afr., 37:357–367.
Norval, R.A.I., 1977. Studies on the ecology of the tick Amblyomma hebraeum Koch in the Eastern Cape Province of South Africa. II. Survival and development. J. Parasitol., 63:740–747.
Norval, R.A.I., 1979. Tick infestations and tick-borne diseases in Zimbabwe Rhodesia. J. Sth. Afr. Vet. Assoc., 50:289–292.
Norval, R.A.I., 1983. The ticks of Zimbabwe. VII. The genus Amblyomma. Zimb. Vet. J., 14:3–18.
Norval, R.A.I., 1986. Amblyomma variegatum and acute bovine dermatophilosis. Parasitol. Today, 2:23.
Norval, R.A.I., 1990. The impact of pure infestations of Rhipicephalus appendiculatus and Amblyomma hebraeum on the productivity of cattle and implications for tick control strategies in Africa. Parassitologia, 32:155–163.
Norval, R.A.I. and Capitini, L.A., 1974. The rate of feeding, and spermatogenesis, in Amblyomma hebraeum Koch, 1844 (Acarina: Ixodidae). J. Ent. Soc. Sth. Afr., 37:393–401.
Norval, R.A.I. and Deem, S.L., 1994. The development and application of models in the planning and implementation of reduced and strategic-minimal tick control strategies in Zimbabwe. In, Modelling of vector-borne and other parasitic diseases (Perry, B.D. and Hansen, J.W., eds.) ILRAD, Nairobi, Kenya, pp. 283–295.
Norval, R.A.I. and Lawrence, J.A., 1979. The control of heartwater in Zimbabwe Rhodesia. Zimb. Rhod. Agric. J., 76:161–165.
Norval, R.A.I. and Rechav, Y., 1979. An assembly pheromone and its perception in the tick Amblyomma variegatum (Acarina: Ixodidae). J. Med. Entomol., 16:507–511.
Norval, R.A.I., Butler, J.F. and Yunker, C.E., 1989a. Use of carbon dioxide and natural or synthetic aggregation-attachment pheromone of the bont tick, Amblyomma hebraeum, to attract and trap unfed adults in the field. Exp. Appl. Acarol., 7:171–180.
Norval, R.A.I., Andrew, H.R. and Yunker, C.E., 1989b. Pheromone-mediation of host-selection in bont ticks (Amblyomma hebraeum Koch). Science, 243:364–365.
Norval, R.A.I., Sutherst, R.W., Jorgensen, O.G., Gibson, J.D. and Kerr, J.D., 1989c. The effect of the bont tick (Amblyomma hebraeum) on the weight gain of Africander stcers. Vet. Parasitol., 33:329–341.
Norval, R.A.I., Perry, B.D., Kruska, R. and Kundert, K., 1991a. The use of climate data interpolation in estimating the distribution of Amblyomma variegatum in Africa. Prev. Vet. Med., 11:365–366.
Norval, R.A.I., Peter, T., Yunker, C.E., Sonenshine, D.E. and Burridge, M.J., 1991b. Responses of the ticks Amblyomma hebraeum and A. variegatum to known or potential components of the aggregation-attachment pheromone. II. Attachment stimulation. Exp. Appl. Acarol., 13:19–26.
Norval, R.A.I., Perry, B.D. and Hargreaves, S.K., 1992a. Tick and tick-borne disease control in Zimbabwe: What might the future hold? Zimb. Vet. J., 23:1–15.
Norval, R.A.I., Barrett, J.C., Perry, B.D. and Mukhebi, A.W., 1992b. Economics, epidemiology and ecology: A multidisciplinary approach to the planning and appraisal of tick and tick-borne disease control in southern Africa. In, Tick vector biology. Medical and veterinary aspects. (Fivaz, B., Petney, T. and Horak, I., eds). Springer-Verlag, Berlin, Heidelberg. pp. 35–54.
Norval, R.A.I., Perry, B.D. and Young, A.S., 1992c. The epidemiology of theileriosis in Africa. Academic Press, London. 481 pp.
Norval, R.A.I., Peter, T., Meltzer, M.I., Sonenshine, D.E. and Burridge, M.J., 1992d. Responses of the ticks Amblyomma hebraeum and A. variegatum to known or potential components of the aggregation-attachment pheromone. IV. Attachment stimulation of nymphs. Exp. Appl. Acarol., 16:247–253.
Norval, R.A.I., Peter, T. and Meltzer, M.I. 1992e. A comparison of the attraction of nymphs and adults of the ticks Amblyomma hebraeum and A. variegatum to carbon dioxide and the maleproduced aggregation-attachment pheromone. Exp. Appl. Acarol., 13:179–186.
Norval, R.A.I., Andrew, H.R., Yunker, C.E. and Burridge, M.J. 1992f. Biological process in the epidemiology of heartwater. In, Tick vector biology. Medical and veterinary aspects. (Fivaz, B., Petney, T. and Horak, I., eds.). Springer-Verlag, Berlin, Heidelberg. pp.71–86.
Norval, R.A.I., Sonenshine, D.E., Meltzer, M.I., Burridge, M.J. and Yunker, C.E. 1993. Attractant decoys for controlling bont ticks and other pests. U.S. patent pending Serial number 07/809, 939.
Perry, B.D., Lessard, P., Norval, R.A.I., Kundert, K. and Kruska, R., 1990a. Climate, vegetation and the distribution of Rhipicephalus appendiculatus in Africa. Parasit, Today, 6, 100–104.
Perry, B.D., Mukhebi, A.W., Norval, R.A.I. and Barrett, J.C. 1990b: A preliminary assessment of current and alternative tick and tick-borne disease control strategies in Zimbabwe. Report to the Director of Veterinary Services. ILRAD, Nairobi. 41pp.
Petney, T.N. and Horak, I.G., 1987. The effect of dipping on parasitic and free-living populations of Amblyomma hebraeum on a farm and on an adjacent nature reserve. Onderstepoort J. Vet. Res., 54:529–533.
Petney, T.N., Horak, I.G. and Rechav, Y., 1987. The ecology of the African vectors of heartwater, with particular reference to Amblyomma hebraeum and Amblyomma variegatum. Onderstepoort J. Vet. Res., 54:381–395.
Rechav, Y. and Zeederberg, M.E., 1986. Tick populations on two breeds of cattle under field conditions, with a note on blood components related to host resistance. In, Morphology, physiology, and behavioral biology of ticks. (Sauer, J.R. and Hair, J.A., eds). Ellis Horwood, Chichester. pp. 445–456.
Rechav, Y., Whitehead, G.B. and Knight, M.M., 1976. Aggregation responses of nymphs to pheromone(s) produced by males of the tick Amblyomma hebraeum (Koch). Nature, 259,563–564.
Rechav, Y., Norval, R.A.I. and Oliver, J.H., 1982. Interspecific mating of Amblyomma hebraeum and Amblyomma variegatum (Acari: Ixodidae). J. Med. Entomol., 19:139–142.
Rechav, Y., Dauth, J. and Els, D.A., 1990. Resistance of Brahman and Simmentaler cattle to southern African ticks. Onderstepoort J. Vet. Res., 57:7–12.
Rechav, Y., Kostrzewski, M.W. and Els, D.A., 1991. Resistance of indigenous African cattle to the tick Amblyomma hebraeum. Exp. Appl. Acarol., 12:229–241.
Sachs, L., 1982. Applied statistics. Springer-Verlag, New York. 704pp.
Scholtz, M.M., Spickett, A.M., Lombard, P.E. and Enslin, C.B., 1991. The effect of tick infestation on the productivity of cows of three breeds of cattle. Onderstepoort J. Vet. Res., 58:71–74.
Sinclair J.M., 1920. Report of the Chief Veterinary Surgeon for the year 1920. Salisbury, Southern Rhodesia. 9pp.
Sinclair J.M. 1927. Report of the Chief Veterinary Surgeon for the year 1927. Salisbury, Southern Rhodesia. 6pp.
Spickett, A.M., De, Klerk, D., Enslin, C.B. and Scholtz, M.M. 1989. Resistance of Nguni, Bonsmara and Hereford cattle to ticks in a bushveld region of South Africa. Onderstepoort J. Vet. Res., 56:245–250.
Sutherst, R.W. 1987. The dynamics of hybrid zones between tick (Acari) species. Int. J. Parasitol., 17:921–926.
Sutherst, R.W. and Maywald, G.F., 1985. A computerized system for matching climates in ecology. Agric. Ecosyst. Ecol., 13:281–299.
Taylor, R.D. and Martin, R.B., 1987. Effects of veterinary fences on wildlife conservation in Zimbabwe. Environm. Manag., 11:327–334.
Theiler, G., 1962. The Ixodoidea parasites of vertebrates in Africa South of the Sahara (Ethiopian Region). Rep. Dir. Vet. Serv., Onderstepoort, South Africa (S 9958).
Uilenberg, G., 1983. Heartwater (Cowdria ruminantium infection): Current status. Adv. Vet. Sci. Comp. Med., 27:427–480.
Van der, Merwe, L., 1979. Field experience with heartwater (Cowdria ruminantium) in cattle. J. Sth. Afr. Vet. Ass., 50:323–325.
Walker, J.B., 1974. The ixodid ticks of Kenya. A review of present knowledge of their hosts and distributions. Commonw. Agric. Bur., Commonw. Inst. Entomol., London. 220pp.
Walker, J.B. and Olwage, A., 1987. The tick vectors of Cowdria ruminantium (Ixodoidea, Ixodidae, genus Amblyomma) and their distribution. Onderstepoort J. Vet. Res., 54:353–379.
Walker, J.B. and Schulz, K.C.A., 1984. Records of the bont tick, Amblyomma hebraeum, from the angulate tortoise, Chersina angulata, and the leopard tortoise, Geochelone pardalis. Onderstepoort J. Vet. Res., 51:171–173.
Whitsun Foundation, The, 1983. Land reform in Zimbabwe. Whitsun Foundation, Harare. 172 pp.
Yeoman, G.H. and Walker, J.B., 1967. The ixodid ticks of Tanzania. A study of the zoogeography of the Ixodidae of an East African country. Commonw. Agric. Bur., Commonw. Inst. Entomol., London. 215 pp.
Yunker, C.E., Andrew, H.R., Norval, R.A.I. and Keirans, J.E., 1990. Interspecific attraction to male-produced pheromones of two species of Amblyomma ticks (Acari: Ixodidae). J. Insect Behav., 3:557–567.
Author information
Authors and Affiliations
Additional information
Deceased.
Rights and permissions
About this article
Cite this article
Norval, R.A.I., Perry, B.D., Meltzer, M.I. et al. Factors affecting the distributions of the ticks Amblyomma hebraeum and A. variegatum in Zimbabwe: implications of reduced acaricide usage. Exp Appl Acarol 18, 383–407 (1994). https://doi.org/10.1007/BF00051522
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00051522
Key words
- Amblyomma hebraeum
- Amblyomma variegatum
- acaricides
- tick control
- wild life
- CLIMEX