Variation in modelled force of infection with Haemonchus contortus as a function of climate 

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Economic impact of nematode infection

A number of gastrointestinal (GIT) helminths of the family Trichostrongylidae infect domesticated ruminants and make a significant contribution to the animal health constraints associated with helminth parasitism. Economic impacts are felt by both the rural poor (Perry et al., 2002) in developing countries and commercial farmers in the industrialized countries of the world (Perry and Randolph, 1999; Jackson et al., 2009). In the United Kingdom (UK), for example, nematode infection in sheep alone is estimated to cost the sheep industry more than GBP 84 million per year (Nieuwhof and Bishop, 2005) and this level of impact is likely to be globally typical (Morgan et al., 2013).
In tropical/subtropical regions, Haemonchus contortus (Rudolphi, 1803) is predominant (Levine, 1963; Perry et al., 2002) due to its high biotic potential of up to 10 000 eggs per female per day, and rapid development of infective larvae under favourable warm and moist conditions (Gordon, 1981). It is also ranked the most economically important parasite of small ruminants in these regions due to its high pathogenicity (Perry et al., 2002), resulting in acute disease outbreaks with high levels of mortality, particularly in young animals (Gordon, 1948). As an example, a drop of up to seven percent in haematocrit within seven days at peak season has been reported by Malan et al. (2001). In Kenya and South Africa annual financial losses directly attributable to H. contortus alone are between US$ 26 million and US$ 45 million (Krecek and Waller, 2006), while in India the annual costs associated with control of this parasite have been estimated at US$ 103 million (McLeod, 2004).
Ostertagiasis by the nematode Ostertagia ostertagi is the most important of the GIT helminth infections of cattle in temperate climates (Myers and Taylor, 1989). Even at sub-clinical infections, where the effects can be subtle, non-obvious and not easily measurable, it can have a profound economic impact on the performance of the whole farm, as illustrated by Van Der Voort et al. (2014) in dairy cattle.
These estimates excluded other society-level economic variables, such as uncertainty with regards to social security as a result of helminthosis, which has a huge impact on societies‟ states of well-being as noted by Wood (2003) and Perry and Grace (2009).

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CHAPTER 1: General Introduction
1.1 Economic impact of nematode infection
1.2 Risk factors for nematodosis
1.2.1 Ecological factors
1.2.2 Host factor
1.3 Anthelmintic resistance (AR)
1.3.1 How did AR arise?
1.3.2 Current global AR state of play
1.3.3 Cause for concern about AR
1.3.4 Consensus on arresting AR
1.4 Approaches to sustainable integrated parasite management (sIPM)
1.5 Challenges associated with implementation of sIPM
1.6 Aims of the thesis
CHAPTER 2: A dynamic infection model to optimise targeted selective treatment (TST) application against Haemonchus contortus in South Africa 
2.1 Introduction
2.2 Methods
2.2.1 Model purpose and application
2.2.2 Husbandry practices on data-source farm
2.2.3 Model general structure
2.2.4 Reproduction class group-dependent contact
2.2.5 Data source for model fitting and validation
2.2.6 Model data fits and parameter estimations
2.4 Discussion
2.5 Conclusion
CHAPTER 3: Variation in modelled force of infection with Haemonchus contortus as a function of climate 
3.1 Introduction
3.2 Methods
3.2.1 Reproductive status group-specific force-of-infection (FOI) data
3.2.2 Rainfall data .
3.2.3 Temperature data
3.2.4 Calculation of rainfall entropy
3.2.5 Statistical analysis
3.3 Results
3.4 Discussion
3.5 Conclusion
CHAPTER 4: Evaluation of a prototype radio frequency identification (RFID) system for remote monitoring of individual animal activity level
4.1 Introduction
4.2 Materials and methods
4.2.1 Prototype system set-up
4.2.2 Experimental design
4.3 Results
4.4 Discussion
4.5 Conclusion
CHAPTER 5: Remote longitudinal individual animal activity level monitoring at pasture to deduce changes in sheep and goat behaviour
CHAPTER 6: Activity level as an indicator of clinical infection of individual goats with Haemonchus contortus 
CHAPTER 7: General Discussion 

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