Project topics and materials
Get Complete Project Material File(s) Now! »
General Introduction
Ticks are haematophagous ectoparasites, capable of transmitting diseases to vertebrates and therefore represent a threat to human, domestic and wildlife health (Norval, 1994). Tick and tick-borne diseases have impacted negatively on development of the livestock industry in Africa (Walker et al. 2003). Ixodid ticks such as Amblyomma variegatum Fabriscius and Rhipicephalus appendiculatus Neumann (Acari: Ixodidae) in particular, are among the most conomically important parasites in the tropics and subtropics (Bram, 1983). Another hardick that is gaining recognition as an important vector of tick-borne pathogens is Rhipicephalus pulchellus Gerstäcker (Acari: Ixodidae) (Walker et al., 2003). Control of this pest largely depends on synthetic acaricides including chlorinated hydrocarbons, pyrethroids, organophosphates and formamidines (amitraz) (Davey et al., 1998; Rodríguez-Vivas and Domínguez-Alpizar, 1998; George et al., 2004). However, extensive use of these chemical as favoured acaricide resistance in ticks (Baker and Shaw, 1965; Solomon et al., 1979; Alonso-Díaz et al., 2006) and led to heightened concerns over health and environmental impact (Dipeolu and Ndungu, 1991; Gassner et al., 1997). Furthermore, synthetic acaricides are expensive to livestock farmers in Africa who mainly practice subsistence farming. These setbacks have motivated the search for alternative tick control strategies that are more environmentally benign. These strategies include the use of entomopathogenic fungi and nematodes, predators, parasitic hymenoptera, tick vaccines, plant extracts, tick pheromones and host kairomones, and integrated use of semiochemicals and acaricides (Mwangi et al., 1991; Kaaya, 2000a; Samish et al., 2004; Maranga et al., 2006).
There is particular interest in microbial control agents, especially entomopathogenic fungi Isolates of Metarhizium anisopliae (Metschnik.) Sorok. and Beauveria bassiana (Bals.) Vuill. (Ascomycota: Hypocreales) are pathogenic against tropical ixodid ticks, Amblyomma variegatum, Rhipicephalus appendiculatus, Rhipicephalus sanguineus Latreille, Rhipicephalus (Boophilus) microplus Canestrini, Rhipicephalus (Boophilus) decoloratus Koch, the deer tick Ixodes scapularis Say (Acari: Ixodidae) and other hard ticks such as Amblyomma americanum Linnaeus and Amblyomma maculatum Koch in the laboratory (Kaaya et al., 1996; Frazzon et al., 2000; Onofre et al., 2001; Benjamin et al. 2002; Kirkland et al., 2004a: 2004b). In field experiments, Kaaya (2000b) and Benjamin et al. (2002) reduced R. appendiculatus larvae and Ixodes scapularis Say (Acari: Ixodidae) unfed adults, in the vegetation by spraying the vegetation with aqueous suspensions of M. anisopliae.
Although these fungi are pathogenic to ticks, different fungal species as well as different fungal isolates of the same species show varying degrees of virulence against ticks (Kirkland et al., 2004a: 2004b and Samish et al., 2001). Therefore, screening of different fungal isolates against different tick species is necessary for the development of an effective biological control agent. So far, no literature is available documenting the susceptibility of R. pulchellus to entomopathogenic fungi. Rhipicephalus pulchellus is one of the most abundant tick species in East Africa (Walker et al., 2003) and evaluation of fungal isolates for pathogenicity against this species is essential to the selection of virulent isolates for further investigation.
CHAPTER ONE General Introduction, Background/Literature Review, Hypotheses and Objectives
1.1 General Introduction
1.2 Background/Literature Review
1.2.1 Project conceptio
1.2.2 Tick biology
1.2.2.1 Tick classification
1.2.2.2 Life cycle of ixodid ticks and development patterns
1.2.2.3 Morphology of ixodid ticks and adaptation
1.2.3 Rhipicephalus pulchellus Gerstäcker, 1873 (Zebra tick)
1.2.4 Ambyomma variegatum Fabricius, 1794 (Bont tick)
1.2.5 Economic importance of ticks
1.2.6 Tick Control
1.3 Hypothesis
1.4 Overall aim of study
1.4.1 Specific Objectives
CHAPTER TWO Laboratory screening of entomopathogenic fungi against Rhipicephalus pulchellus Gerstäcker (Acari: Ixodidae)
2.1 Introduction
2.2 Materials and methods
2.2.1 Ticks
2.2.2 Fungi
2.2.3 Bioassays
2.2.4 Data analyses
2.3 Results
2.4 Discussion
CHAPTER THREE Optimizing techniques of inoculation of Rhipicephalus
ticks (Acari: Ixodidae) with mitosporic entomopathogenic fungus in the
laboratory
3.1 Introduction
3.2 Materials and methods
3.3 Results
3.4 Discussion
CHAPTER FOUR The use of a semiochemical bait to enhance exposure
of Amblyomma variegatum (Acari: Ixodidae) to Metarhizium anisopliae
(Ascomycota: Hypocreales)
4.1 Introduction
4.2 Materials and Methods
4.3 Results
4.4 Discussion
