PAPER SESSION VII: MANAGEMENT AND CONTROL OF MITES AND TICKS

CHAIRPERSON: Dr. E. Kokwaro

LEAD PAPER 2

prospects for innovative methods of tick control in africa

G.P. Kaaya

Department of Biology, University of Namibia, Private Bag 1330, Windhoek, Namibia. E-mail: gkaaya@unam.na

Ticks and tick-borne diseases are considered the greatest animal disease problem in Africa. The 4 major groups of ticks include Amblyomma, Rhipicephalus, Hyalomma and Boophilus species. Amblyomma variegatum has spread beyond the boundaries of the African continent to the Indian ocean islands, Yemen, the Caribbean and now threatens to invade the USA. Ticks harm their animal hosts mechanically by sucking blood, reducing growth rate and milk yield, damaging hides and skins, causing tick worry, introduction of toxins and by predisposing them to myasis. Ticks also transmit devastating diseases e.g. theileriosis, cowdriosis, babesiosis and anaplasmosis to animals. It is generally accepted that theileriosis, cowdriosis and dermatophilosis are the major tick-borne and tick-associated diseases of grazing cattle in Africa. The conventional method of tick control is by application of chemical acaricides, which is fraught with several problems e.g. environmental pollution, chemical residues in meat and milk products and in wool, development of tick resistance and the exorbitant costs. Alternative innovative, environmentally friendly, cost-effective and sustainable methods of tick control will therefore be needed for alleviation of these problems. An integrated approach that will make optimum use of a combination of various strategies will be the most appropriate. Some of the innovative components for integrated tick management are already available in Africa and will be discussed in this paper. These include: traditional and cultural methods e.g. intergrazing and hand deticking; biological control methods using predators, parasitoids and pathogens; anti–tick vegetation e.g. grasses and botanical extracts.

PAPER 26

Studies on the immune defence of cattle and chickens against Boophilus annulatus and Argas persicus ticks

K.M. El Kammah & K.S.E. Abdel-Wahab

Faculty of Agriculture, Cairo University, Giza, Cairo, Egypt, E-mail: kkammah@link.net

Host acquired resistance to tick bite and feeding is the best alternative to the use of acaricides. There is high economic loss in both the meat and poultry industries due to tick infestation in Egypt. Prolonged infestation by Boophilus annulatus ticks induced acquired immunity in cows in Egypt against specific salivary gland, gut proteins and persicus antigens. Antibodies against salivary gland and gut crude, or polyacrylamide gel electrophoresis (PAGE), separated antigens were detected by enzyme linked immune assay (ELISA) and immunoplot. Cell mediated immunity (CMI) was also detected by macrophage migration inhibition assay (MMI). Both antibodies and CMI were related to the extent of tick infestation. Repeated infestation of spring chickens by Argas persicus females stimulated chicken resistance to tick feeding. This resistance was associated with an antibody activity to tick salivary gland antigens which was detected by ELISA. Changes in chicken serum protein band separation by PAGE under reducing conditions were suggestive of immunoglobulin increase. Introduction of chicken resistance to ticks was also achieved by repeated injection with crude Argas persicus salivary gland antigens. Comparison between subcutaneous and intramuscular injection of graded doses of salivary gland antigens showed variation in the serum immunoglobulin content by PAGE and in the antibody activity by ELISA against some of the 26 fractions of salivary gland proteins obtained by column chromatography. Analysis showed that intramuscular "vaccination" was the more efficient in obtaining the desired resistance. Prolonged infestation by Argas persicus and Boophilus annulatus induced an immune defence against the specific tick in chickens and cows. Understanding this relationship is a prelude to the development of anti-tick vaccines in Egypt.

PAPER 27

THE ATTRACTION OF AMBLYOMMA VARIEGATUM (FABRICIUS, 1794) TO THE ATTRACTION AGGREGATION ATTACHMENT PHEROMONE WITH/WITHOUT CO₂ IN THE FIELD

R.O. Maranga^1,2, A. Hassanali¹, G.P. Kaaya¹& J.M. Mueke³

¹International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi, Kenya.

² Present address: Jomo Kenyatta University of Agriculture and Technology (JKUAT), Department of Zoology, P.O. Box 62000, Nairobi, Kenya, E-mail: bellamaranga@yahoo.com, rmaranga@jkuat.ac.ke

³Kenyatta University, Department of Zoology, P.O. Box 43844, Nairobi, Kenya.

The responses of adult Amblyomma variegatum released from various distances to different doses of the synthetic attraction-aggregation-attachment pheromone (AAAP) (made up of ortho-nitrophenol, methyl salicylate and nonanoic acid in paraffin) dispensed from the centres of circular field plots were studied in the presence/absence of elevated levels of carbon dioxide.  Up to 90% of the ticks released were attracted to the pheromone source in the presence of CO₂ within 3hr. CO₂ alone was unattractive, similar to previous findings in Zimbabwe, but unlike the results from a Caribbean A. variegatum population, which was significantly attracted to this signal.  In the absence of CO₂, smaller but significant proportions of the released ticks were attracted to the pheromone, albeit more slowly, suggesting another variation in the responses of this bont tick to inter- and intra-specific signals. Our results are interpreted in the light of a study undertaken elsewhere demonstrating relatively high heterozygosity among tick populations.  Possible directions of further research to explore the use of the pheromone in off-host control of the tick are also highlighted.

PAPER 28

Biological control of cassava green mite in Kenya: persistence of Typhlodromalus aripo DeLeon (ACARI: PHYTOSEIIDAE) and impact on cassava green mite populations

C. W. Kariuki¹, M. Toko² & R. Hanna²

¹KARI, National Agricultural Research Centre Muguga, P.O. Box 30148 Nairobi, KENYA, E-mail: ckariuki@nbnet.co.ke

² Biological Control Centre for Africa, International Institute of Tropical Agriculture, 08 BP 0932, Cotonou, Benin

Since its introduction in 1995 and subsequent establishment in the major cassava growing regions in Kenya, as evidenced through post release surveys, Typhlodromalus aripo DeLeon has continued persisting. It has consistently been recorded in the different agro-ecological zones of the major cassava growing regions around Lake Victoria and along the coast. T. aripo has not only spread to new areas and persisted, but it has also reduced the population of cassava green mite in some areas where it is found. Past CGM monitoring surveys in early 1990s indicated high population densities of up to 150 adult mites per leaf in some sites. Results of CGM survey in areas where T. aripo is already established in some selected sites in 1999 and 2000 indicate a significant reduction in CGM population. This trend in reduction of CGM population is likely to continue as T. aripo population is also increasing. A mean number of up to 15 adult T. aripo have been observed in some areas where it is established.