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General introduction, literature review and scope of the thesis
The demand to perform immobilisation and general anaesthesia in wild ungulates, in particular antelope, has surged in the recent past in South Africa. The growing demand is due to the increased value of these antelope in game ranching and zoological collections. Antelope remain a challenging species to immobilise and place under general anaesthesia, mostly due to their anxious disposition (Ball 2007; Ball & Hofmeyr 2014) and physiological response to immobilising drugs (Kock & Burroughs 2012). Impala (Aepyceros melampus) have often been used in research studies as a model for other antelope, especially in research fields focusing on behaviour (Jarman 1970; Cronje et al. 2002; Matson et al. 2004; Rduch 2016), thermoregulation (Maloiy & Hopcraft 1971; Meyer et al. 2008a; Shrestha et al. 2012), predator-prey relationships (Caro et al. 2004; Shorrocks & Cokayne 2005; Tarakini et al. 2014), parasitology in wild (Ezenwa 2004) and captive (Mooring et al. 1996) herds, reproduction (Jarman & Jarman 1973; O’Kane & Macdonald 2016) and physical or chemical capture (Pienaar et al. 1966; Ables & Ables 1969; Drevemo & Karstad 1974; Grootenhuis et al. 1976; Murray et al. 1981; Cheney & Hattingh 1987; Hattingh 1988; Gandini et al. 1989; Hattingh et al. 1990; Knox et al. 1990; Knox et al. 1991; Knox et al. 1992; Knox et al. 1993; Janssen et al. 1993; Pitts & Mitchell 2002; Bush et al. 2004; Meyer et al. 2008b; Meyer et al. 2010; Perrin et al. 2015; Zeiler et al. 2015; Buck et al. 2017; Gerlach et al. 2017). Despite being a popular research model, little is known on what effects intensive research projects have on the impala’s wellbeing. Furthermore, few publications report on physical and chemical capture of impala that have been confined in an outdoor antelope housing structure (boma) (Knox et al. 1992; Bush et al. 2004; Meyer et al. 2008a, b; Meyer et al. 2010). Only a few of these studies have reported mortalities in impala (Knox et al. 1992; Meyer et al. 2008a), but in practice, morbidity and mortality appear to occur more often than reported. Therefore, if impala are to be used in intense studies investigating novel immobilisation and general anaesthetic drug combinations, there is a need to clearly understand the physiological and welfare effects of the drugs and the procedures and management practices used during boma confinement of captured free-ranging impala during these studies. Understanding these aspects will identify the risks of morbidity and mortality associated with these species. Identifying these risks will allow for feasible practical recommendations to be made in order to improve the health and welfare of impala enrolled in boma immobilisation and general anaesthesia related studies.
Chemical immobilisation and general anaesthesia defined
Chemical immobilisation and general anaesthesia are different states, and although definitions of each have been proposed, the specifics of these definitions are not always agreed upon in the literature. Nevertheless, the concepts of chemical immobilisation and general anaesthesia are reviewed and a definition of each will be synthesised from the available information and these will be used for the rest of the thesis. In general chemical immobilisation is when drugs are administered alone or in various combinations with the specific purpose of capturing an animal. The aspects that encompass the administration of the drug(s) and subsequent capture of the animal is termed chemical capture. The most common features used to describe a state of chemical immobilisation include: 1) an animal that, due to drug effects, does not ambulate easily and is often found recumbent or could be easily manipulated into a recumbent state by a member of the capture team; 2) the animal’s level of conscious awareness is obtunded to the extent that they are often unaware of, or only mildly respond to noxious or other external stimuli; 3) the animal’s autonomic and subconscious reflexes remain intact; and 4) chemical immobilisation can typically be reversed by the administration of pharmacological or physiological antagonist drugs (Kock & Burroughs 2012). General anaesthesia can be defined as a state of unconsciousness that is produced by a process of controlled, reversible, depression of the central nervous system, whereby the patient neither perceives nor recalls noxious or other external stimuli. Furthermore, the state of general anaesthesia must fulfil three criteria (called the triad of general anaesthesia), as follows: 1) render patient unconscious, whereby there is no perception or memory of any sensory or motor event; 2) supresses autonomic (haemodynamic, respiratory and thermoregulatory) and somatic (proprioception reflexes such as the righting reflex) reflexes to a point where the patient maintains normal physiological function (or as near to normal as possible) and ensures muscle relaxation; and 3) provides antinociception, whereby the responses to surgical stimulation (nociceptive sensory inputs) are supressed (Eke & Bell 2004).
Physical and chemical techniques used to capture impala
Various physical and chemical capture techniques used in medium sized antelope have been evaluated, mainly in impala, over the last seven decades. These techniques are studied either in free-ranging impala in the wild or in impala captured from the wild, relocated to a boma, and kept in captivity during the investigations. Prior to the introduction of the potent opioid etorphine in the early 1960s, physical capture techniques were commonly used to capture wild antelope, and often they were the only method available (Harthoorn 1967; Haigh 1990). Hand-capture and net-capture techniques have been described for medium sized antelope.
General anaesthesia techniques used to anaesthetise impala
Most of the drugs used to capture wild animals do not usually cause an adequate depth of anaesthesia for surgical intervention (Stage 3 Plane II and III). If general anaesthesia is required, anaesthetic drugs can be given to induce the necessary plane of general anaesthesia once the animal is chemically immobilised (Dugdale 2010; West et al. 2014; Grimm et al. 2015). General anaesthesia can be induced by administering a hypnotic (propofol, thiopentone, alfaxalone) or dissociative (ketamine) drug intravenously (most common technique in impala) or intramuscularly (ketamine or alfaxalone; only necessary in impala that are not effectively immobilised). In practice, the end-point of induction of general anaesthesia is usually defined as the state where an orotracheal tube can be placed without purposeful avoidance movements of the head (Dugdale 2010; Grimm et al. 2015). Other end-points for induction of general anesthesia have been used, such as the loss of the righting reflex, and loss of complex, purposeful movement during noxious stimulation, such as a pedal withdrawal reflex. Once induced into general anaesthesia then this state can be maintained by either administering inhalation or intravenous drugs (Ball 2007; Ball & Hofmeyr 2014).
DECLARATION
ACKNOWLEDGEMENTS
Chapter 1
General introduction, literature review, scope of the thesis
General introduction
1.2.1 Chemical immobilisation and general anaesthesia defined
1.2.2 Physical and chemical techniques used to capture impala
1.2.3 General anaesthesia techniques used to anaesthetise impala
1.2.4 Drugs used during chemical capture and general anaesthesia of impala
1.2.5 Physiological effects of chemical capture and general anaesthesia in impala
1.2.6 Capture and anaesthesia associated mortalities in impala
1.2.7 Behaviour characteristics of impala
1.2.8 Impala research models
1.2.9 Short and long-term captive management of impala
1.2.10 Welfare and ethics related to captive management of impala in research Scope of the thesis
1.3.1 Problem statement
1.3.2 Aims of the thesis
Chapter 2
Comparison of thiafentanil-medetomidine to etorphine-medetomidine immobilisation of impalas (Aepyceros melampus)
Abstract
Introduction
Materials and Methods
Results
Discussion
Conclusions
Chapter 3
Etorphine-ketamine-medetomidine total intravenous anaesthesia in wild impala (Aepyceros melampus) of 120 minute duration
Abstract
Introduction
Materials and Methods
Results
Discussion
Conclusions
Chapter 4
Blood acid-base status in impala (Aepyceros melampus) immobilised and maintained under total intravenous anaesthesia using two different drug protocols
Abstract
Introduction
Materials and Methods
Results
Discussion
Conclusions
Chapter 5
Captive management of wild impala (Aepyceros melampus) during intensive immobilisation and general anaesthesia study trials
Abstract
Introduction
Materials and Methods
Results
Discussion
Conclusions
Chapter 6
Chemical capture of impala (Aepyceros melampus): a review of factors contributing to morbidity and mortality
Abstract
Introduction
Morbidity and Mortality Rates
Factors Contributing to Morbidity and Mortality
Environmental Factors
Drug and Drug Delivery Factors
Animal Factors
Conclusions
Chapter 7
Discussion and general conclusions
Drug effects of chemical immobilisation and general anaesthesia
Welfare and ethics of using impala as a research model
Final summary and recommendations
REFERENCES
Addendums
Animal Ethics Certificates
A.1 Certificate V099/13
A.2 Certificate V012/16
Proof of published articles
A.3 Comparison of thiafentanil-medetomidine to etorphine-medetomidine immobilisation of impalas (Aepyceros melampus)
A.4 Etorphine-ketamine-medetomidine total intravenous anaesthesia in wild impala (Aepyceros elampus) of 120-minute duration
A.5 Blood acid-base status in impala (Aepyceros melampus) immobilised and maintained under total intravenous anaesthesia using two different drug protocols
A.6 Captive management of wild impala (Aepyceros melampus) during intensive immobilisation and general anaesthesia study trials
A.7 Chemical capture of impala (Aepyceros melampus): a review of factors contributing to morbidity and mortality
