The respiratory physiology of opioid immobilisation in African antelope

This thesis addresses the mitigation of opioid-induced respiratory depression in wild African antelope species. Potent opioids such as etorphine or thiafentanil are often used for the immobilisation of wild herbivores. One disadvantage of using these potent opioids is that they can cause clinically significant respiratory depression which is due to their potent effect on mu-opioid receptors. Activation of mu-opioid receptors in the respiratory centres of animals depresses neurons that generate the normal respiratory rhythm. At the same time activation of mu-opioid receptors on chemo receptors in the brain stem, on the aortic arch and carotid bodies depresses the normal respiratory drive as these chemo receptors become less sensitive to activation by hypercapnia, hypoxaemia and acidaemia. This effect in turn leads to a reduction of the respiratory frequency and tidal volume. Furthermore, pulmonary vasoconstriction, caused by the sympathomimetic actions of etorphine, decreases pulmonary perfusion. This effect leads to impaired diffusion of oxygen through the alveolar membrane. Studies have found that serotonergic ligands, specifically 8-hydroxy-2-(di-n-propylamino) tetralin (8-OHDPAT), improved blood oxygenation by reducing opioid-induced respiratory depression and improving pulmonary perfusion through their serotonergic effects on the lungs and brain. More specifically, 8-OH-DPAT binds to 5-HT1A and 5-HT7 serotonin receptors in the lungs and brain. This binding results in smooth muscle relaxation and improved pulmonary perfusion without affecting catatonia and sedation caused by opioids. It was thought that the use of the R-enantiomer of 8-OH-DPAT (R-8-OH-DPAT) in comparison to the racemic form (RS-8-OH-DPAT), might produce even better results because of its high specificity at the 5- HT1A receptors. Although some literature on the pharmacokinetic data of 8-OH-DPAT in rats and marmosets existed, there was no published literature available on the pharmacokinetics of 8-OH-DPAT in ungulates. Therefore, the investigation into the pharmacokinetics and bioavailability of R-8-OH-DPAT in goats served as the first step in a series of experiments to understand the viability of adding R-8-OH-DPAT to an opioid-based immobilisation protocol for wild antelope species in order to alleviate respiratory depression. It was hypothesised that the pharmacokinetics and bioavailability of R-8-OH-DPAT in goats would be similar but different to that reported in other species. It was established that the bioavailability of R-8-OH-DPAT when injected intramuscularly (IM) into goats was 66%. At the dosage used in this experiment (0.1 mg kg- 1), signs of serotonin toxicity were observed in some of the goats. The bioavailability results, as well as the encountered side effects in goats, guided the choice of three experimental R-8- OH-DPAT dosages for the next experiment. The second experiment aimed to determine the ability of R-8-OH-DPAT, when administered in combination with etorphine in a dart, to prevent opioid-induced respiratory depression in blesbok (Damaliscus pygargus phillipsi) and impala (Aepyceros melampus). The experiment also aimed to establish the most clinically effective dosage of R-8-OH-DPAT, in these species. Blesbok and impala were chosen for the second experiment as they were abundant and readily available in the study area. Both are antelope species commonly immobilised with potent opioids. Impala are regularly used in immobilisation experiments. It was hypothesised that R-8-OH-DPAT would mitigate opioid-induced respiratory depression in wild ungulates without affecting the quality of immobilisation. R-8-OH-DPAT did not influence induction, immobilisation or recovery scores in either of the species. However, this experiment revealed that there were substantial differences between the two antelope species and their physiological changes after the administration of etorphine alone as well as etorphine in combination with 0.005, 0.02 and 0.07 mg kg-1 R-8-OH-DPAT respectively. Surprisingly, opioid-induced hypoxia was substantially more severe in impala compared to blesbok. Respiratory rate in blesbok, but not impala, increased with an increasing dosage of R-8-OHDPAT but this did not translate into clinically relevant improvements in partial arterial oxygen pressure (PaO2) values in blesbok. In impala, the medium and higher dosages of R-8-OH-DPAT combined with etorphine led to an improved PaO2 and decreased opioid-induced tachycardia during the first ten minutes of immobilisation. It was concluded that species-specific effects and the possibility of serotonin toxicity at higher dosages, which seemed most effective, might not allow the routine use of R-8-OHDPAT at appropriate dosages for wildlife immobilisation. These results lead to the third experiment which aimed at comparing physiological effects of two commonly used potent opioids, namely etorphine and thiafentanil, in both antelope species. It was hypothesised that the time to recumbence, immobilisation quality and physiological variables during immobilisation of blesbok and impala respectively would differ between the two potent opioids. The results of this experiment demonstrate that both opioids used in high dosages are suitable for immobilisation of blesbok and impala without the addition of any sedative or tranquillisers. Both, blesbok and impala developed hypertension with either of the opioids. The thiafentanil treated animals of both species developed higher systemic blood pressure compared to the etorphine treated animals. The healthy animals used for these experiments recovered from hypertension without apparent adverse consequences. Thiafentanil in impala achieved a faster time to recumbence compared to etorphine but thiafentanil also was responsible for more incidences of prolonged apnoea during the beginning of the monitoring period in impala. Overall, there were large differences in the reaction of individual impalas to the opioid immobilisation, which seemed to result in unpredictable immobilisation. In blesbok, opioid-induced respiratory depression, hypoxia and hypercapnia were much less pronounced than in impala. Thiafentanil treated blesbok had higher respiratory rates, higher PaO2 and lower partial arterial carbon dioxide pressure (PaCO2) compared to etorphine treated blesbok. There was no difference in time to recumbence between the two opioids in blesbok. In conclusion, for short term management procedures of impala and blesbok, both opioids are suitable. No matter which opioid is used, both cause hypoxaemia to a greater or lesser degree and oxygen supplementation should be considered for both species. Veterinarians should also be aware that in some species, such as impala, thiafentanil can achieve a faster time to recumbence than etorphine. However, this statement cannot be applied across all species as in blesbok there was no significant difference between both drugs with regards to time to recumbence. In addition, time to recumbence has to be weighed against potential negative respiratory, pulmonary and cardiovascular side-effects of the drug. While these experiments did not give the desired positive results with regards to the use of R-8-OH-DPAT to alleviate opioid-induced respiratory depression, they led to insights into differences between the two opioids which will enable veterinarians to make a more educated decision as to which opioid should be used preferentially. New insights into the differences between blesbok and impala with respect to reaction and physiological changes caused by opioids will also enable researchers to make decisions with regards to species selection for wildlife trials. It may also explain some of the difficulties encountered when immobilising impala

Occurrence of tick-borne haemoparasites in nyala (Tragelaphus angasii) in KwaZulu-Natal and Eastern Cape Province, South Africa

A total of 143 blood samples of nyala (Tragelaphus angasii) from two regions in South Africa were tested for the presence of tick-borne haemoparasites by means of polymerase chain reaction (PCR) and reverse line blot (RLB) hybridisation. While most blood samples taken in EDTA blood turned out negative for the presence of haemoparasites, the majority of blood samples collected on Whatman® filter paper contained several different haemoparasites, often in combination. Samples from the Eastern Cape Province as well as from KwaZulu- Natal turned out positive. Prevalent haemoparasites were Theileria sp. (kudu), T. buffeli, T. bicornis, Theileria sp. (sable), T. taurotragi, Ehrlichia sp. Omatjenne, Anaplasma bovis and A. marginale. This serves as the first report of T. buffeli, T. sp. (kudu), T. bicornis, T. taurotragi, Ehrlichia sp. Omatjenne, A. marginale and A. bovis in nyala. CopyrightDissertation (MSc (Veterinary Tropical Diseases))--University of Pretoria, 2009.Veterinary Tropical Diseasesunrestricte

Malignant catarrhal fever : an emerging disease in the African buffalo (Syncerus caffer)

Within the tribe Bovini in the subfamily Bovinae, the water buffalo (Bubalus Bubalis), American bison (Bison bison), European bison (Bubalus bonasus) and yak (Bos grunniens) are recognized as species highly susceptible to malignant catarrhal fever (MCF). In contrast, the lack of reports describing clinical MCF in the African buffalo (Syncerus caffer) whether free ranging or captive has led to a perception that African buffaloes are resistant to MCF. During the last decade, several cases of MCF in African buffaloes were confirmed in South Africa and experience with seven of these cases is described in this report. Detection of viral nucleic acid in blood or tissues was successful in six African buffaloes that suffered from clinical signs compatible with MCF. Four were positive for infection with ovine herpesvirus type 2 (the causative virus of sheep-associated MCF), and two were positive for alcelaphine herpesvirus type 1 (causative virus of wildebeestassociated MCF). Histopathological examination of tissue samples from all the animals yielded typical lesions that were consistent with those described for MCF in domestic cattle. Developments in the management of African buffaloes translocated from their traditional habitats have likely contributed to the identification of another susceptible host in the subfamily Bovinae.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1865-16822016-06-30hb201

Capture of farmed Nile crocodiles (Crocodylus niloticus) : comparison of physiological parameters after manual capture and after capture with electrical stunning

The electric stunner (e-stunner) is commonly used to handle Nile crocodiles (Crocodylus niloticus) on commercial farms in South Africa, but while it seems to improve handling and safety for the keepers, no information regarding physiological reactions to e-stunning is currently available. The aim of this study was therefore to compare various physiological parameters in farmed Nile crocodiles captured either manually (noosing) or by using an e-stunner. A total of 45 crocodiles were captured at a South African farm by either e-stunning or noosing, and blood samples were taken immediately as well as four hours after capture. Parameters monitored were serum corticosterone, lactate, glucose, as well as alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, and creatinine kinase. Lactate concentrations were significantly higher in noosed compared to e-stunned animals (P < 0.001). No other blood parameter differed significantly between the two capture methods. In addition, recorded capture time confirmed that noosing takes significantly longer compared to e-stunning (P < 0.001), overall indicating that e-stunning seems the better option for restraint of especially large numbers of crocodiles in a commercial setup because it is quicker, safer, and did not cause a significant increase in any of the parameters measured.http://veterinaryrecord.bmj.com/hb201

Tick-borne blood parasites in nyala (Tragelaphus angasii, Gray 1849) from KwaZulu-Natal, South Africa

A total of 97 blood samples of nyala (Tragelaphus angasii, Gray 1849) from South Africa were tested for the presence of tick-borne haemoparasites by means of polymerase chain reaction (PCR) and reverse line blot (RLB) hybridisation. The majority of blood samples contained several different haemoparasites, often in combination. Prevalent haemoparasites were Theileria sp. (kudu), T. buffeli, T. sp. (sable), T. bicornis, Ehrlichia sp. Omatjenne, Anaplasma marginale and A. bovis. This serves as the first report of T. sp. (kudu), T. buffeli, T. bicornis, Ehrlichia sp.Omatjenne, A. marginale and A. bovis in nyala, who seem to carry multiple haemoparasites without ill effect.This study (V009/08) was approved by the Research Committee of the Faculty of Veterinary Science and the Animal Use and Care Committee of the University of Pretoria. The senior author received a postgraduate bursary from the University of Pretoria. Financial support from the National Research Foundation Grant (GUN 44403) to B.L. Penzhorn is acknowledged.http://www.elsevier.com/locate/vetpa

Physiological parameters of farmed Nile crocodiles (Crocodylus niloticus) captured manually and by electrical immobilisation

During the past 15 years crocodile farming has become more important and sophisticated all over the world. In South Africa there are currently an estimated one million Nile crocodiles (Crocodylus niloticus) on commercial farms, mostly for leather production. The management, especially of crocodiles that are close to slaughter, is very intensive as the skins of these animals have to be in immaculate condition to achieve good prices on the international markets. In this regard, the electric stunner is often used on a daily basis on most farms in South Africa to safely handle crocodiles. However, this technique (electrical immobilisation) has only been scientifically evaluated in the Australian saltwater crocodile (C. porosus). As crocodilian species might react differently to the electrical immobilisation procedure, the aim of the project was to compare certain physiological parameters of Nile crocodiles captured by either electrical immobilisation (stunning) or captured manually by noosing. This study was conducted during the summer of 2012 on a commercial crocodile farm near Pongola, South Africa. In total 45 crocodiles were used of which 23 crocodiles were captured by electrical immobilisation and 22 by means of noosing. Physiological parameters chosen for monitoring were serum corticosterone, blood lactate, blood glucose, as well as alanine aminotransferase (ALT), alkaline phosphatase (ALP), aspartate aminotransferase (AST) and creatinine kinase (CK). The concentrations and activities of these parameters were determined in blood samples collected immediately after capture by the two methods. Animals were then tied and blind-folded and kept in a quiet place. Four hours later blood samples were collected again from each animal to monitor changes in concentrations and activities of these parameters. In all cases the time was recorded that it took to capture each animal. In addition, total handling time until blood collection was also recorded on an individual basis. Our results indicate that although corticosterone increased greatly within the four hour interval in both groups, there was no difference (p> 0.05) between the two methods of capture. Lactate did not increase significantly within the four hour period in both groups, but was higher when animals were noosed. Glucose concentrations rose within four hours, but no significant differences could be detected between the two capture methods. While ALT and ALP did not show any clear trend, increased activities were detected for AST and CK in the four hour period after capture. Both, AST and CK levels were higher in noosed animals. Noosing a crocodile took longer to restrain the animal when compared to the stunning method. On average stunning took 118 seconds from start of capture until an animal was under control while noosing took 186 seconds per animal. As a consequence the noosed animals struggle for a longer time, which most probably caused exhaustion and muscle damage; explaining the higher levels of blood lactate, AST and CK. One helper was injured (bite wound) trying to control a crocodiles using the noose method. Electrical immobilisation is therefore considered to be the better option for commercial farms, from a physiological perspective, as well as an animal welfare and human safety viewpoint.Dissertation (MMedVet)--University of Pretoria, 2013.tm2015Production Animal StudiesMMedVetUnrestricte

Perineal urethrostomy to treat obstructive urolithiasis in a captive hand-raised steenbok (<i>Raphicerus campestris</i>)

The steenbok (Raphicerus campestris) is a small antelope of the family Bovidae native to the African continent. Urolithiasis, the formation of urinary calculi in the urinary tract, can be caused by a variety of factors such as diet, dehydration, infection and anatomical predisposition. Urolithiasis, with uroliths identified as magnesium calcium phosphate carbonate in composition, was diagnosed in a hand-reared 5-month-old steenbok. Perineal urethrostomy was performed as a component of the broad treatment regime that included fluid therapy, antibiotic and anti-inflammatory treatment. However, the animal died 4 days later as a result of systemic hypoxia and energy depletion because of stress and cachexia. The challenges of post-surgical treatment, the importance of positive energy balance in small ruminants under stressful circumstances, as well as the role of diet of hand-reared antelope in predisposition to urolith formation are highlighted

Perineal urethrostomy to treat obstructive urolithiasis in a captive hand-raised steenbok (Raphicerus campestris)

The steenbok (Raphicerus campestris) is a small antelope of the family Bovidae native to the African continent. Urolithiasis, the formation of urinary calculi in the urinary tract, can be caused by a variety of factors such as diet, dehydration, infection and anatomical predisposition. Urolithiasis, with uroliths identified as magnesium calcium phosphate carbonate in composition, was diagnosed in a hand-reared 5-month-old steenbok. Perineal urethrostomy was performed as a component of the broad treatment regime that included fluid therapy, antibiotic and anti-inflammatory treatment. However, the animal died 4 days later as a result of systemic hypoxia and energy depletion because of stress and cachexia. The challenges of post-surgical treatment, the importance of positive energy balance in small ruminants under stressful circumstances, as well as the role of diet of hand-reared antelope in predisposition to urolith formation are highlighted.http://www.jsava.co.zaam2018Companion Animal Clinical StudiesParaclinical SciencesProduction Animal Studie

Evaluation of the reliability of pulse oximetry, at different attachment sites, to detect hypoxaemia in immobilized impala (Aepyceros melampus)

Please read abstract in the article.The University of Pretoria, Faculty of Veterinary Science, Department of Paraclinical Science, South African Veterinary Association (Wildlife Group) and the National Research Foundation.https://www.journals.elsevier.com/veterinary-anaesthesia-and-analgesia2021-05-01hj2020Centre for Veterinary Wildlife StudiesCompanion Animal Clinical StudiesParaclinical Science

Adenoviral hepatitis in two Nile crocodile (Crocodylus niloticus) hatchlings from South Africa

Adenoviral infections may cause mild to severe morbidity or fatality in a large array of animal species. In crocodilians, hatchlings under 5 months of age are usually affected. However, there is a paucity of information on actual incidences in hatchlings originating from South Africa. Two cases of adenoviral hepatitis in crocodile hatchlings about 2 weeks old, bred on a commercial farm in South Africa, are described. Both hatchlings showed typical clinical signs of hepatitis. The identification of intranuclear inclusion bodies in the liver was used to differentiate between adenoviral hepatitis and chlamydial hepatitis. Although vertical transmission has never been proven in crocodiles, the young age of the affected hatchlings raises the possibility of vertical transmission. The lack of epidemiological information on adenoviral hepatitis in crocodiles highlights the need for further characterisation of the virus and targeted surveillance.http://www.jsava.co.za/index.php/jsavapm2020Anatomy and Physiolog