Spirocercosis is a canine disease caused by the nematode parasite Spirocerca lupi (Rudolphi, 1809) (Spirurida: Spirocercidae) and is a potentially fatal condition in domestic dogs (Canis familiaris). The larval life cycle of this parasite involves intermediate and paratenic (transport) hosts. Various species of coprophagous dung beetles (Scarabaeidae: Scarabaeinae) serve as the principle intermediate hosts. Despite extraordinary advances in biomedical research, it is unlikely that these alone will alleviate the burden of this parasitic disease in dogs. Recently, there has been growing concern over the upsurge in incidence and reported cases of spirocercosis in domestic dogs in South Africa. There is a plethora of literature on the clinical, diagnostic and epidemiological aspects of this disease in dogs, yet no study has aimed at fully understanding the dynamic interactions between the various hosts and S. lupi, governed by the consequences of their behaviour under different and ever-changing environmental conditions. It is most likely that the impact of this disease is accentuated by constant changes in human demographics and behaviour. Studies on spirocercosis in dogs have considered the consumption of the various paratenic hosts or the deliberate ingestion of dung beetles to be the main cause of the transmission of S. lupi to dogs. However this study suggests that the coprohagous behaviour of dogs and the subsequent accidental ingestion of coprophagous dung beetles in or on faeces are mainly responsible for the transmission of this parasitic nematode to dogs. Changes in urban land use and subsequent changes along urban-rural gradients influence the nature of biological interactions partly due to changes in species assemblage structure and composition. Such alterations in assemblage structure of species pose a particular risk to altered rates of parasitism and disease transmission. It is concluded that these changes in landscape use coupled to altered dung beetle species assemblage structure have influenced the pattern of events observed in this host – parasite relationship. Furthermore, the social organization of domestic dogs (pets versus feral animals) and the availability of exposed excrement as a direct or indirect consequence of human behaviour played a pivotal role in the rate these parasites are transmitted to dogs. / Thesis (PhD)--University of Pretoria, 2012. / Zoology and Entomology / unrestricted

A variety of faecal examination methods have shown variable sensitivity in identifying larvated Spirocerca lupi (S. lupi) eggs. The purpose of this study was to determine which faecal examination method, including a novel modified centrifugal flotation method, was most sensitive in the diagnosis of spirocercosis. Faeces were collected from 33 dogs diagnosed with spirocercosis by oesophageal endoscopy at the Onderstepoort Veterinary Academic Hospital between 2008 and 2009. If the first evaluation was negative, a second faecal sample was evaluated 24-48 h later. Ten faecal examinations using 1 g aliquots of faeces were performed per sample. Four faecal examination methods were evaluated; direct faecal examination using saline, direct faecal flotation, a modified faecal centrifugal flotation and a laboratory performed faecal sedimentation/flotation. The direct and modified centrifugal flotation methods were each performed using four faecal flotation solutions; NaNO3 (Specific gravity (SG) 1.22), MgSO4 (SG 1.29), ZnSO4 (SG 1.30) and saturated sugar (SG 1.27). The sedimentation/flotation method utilized MgSO4 (SG 1.29). The modified centrifugal flotation method required centrifugation (1400 G) of a prepared faecal suspension (1 g faeces suspended in 5 ml of flotation solution) after which 0.1 ml of the supernatant was aspirated from the surface using an adjustable volume micropipette for microscopic examination. The 10 faecal examination tests were statistically analysed using the Friedman test (nonparametric equivalent of analysis of variance) p=0.000, z value = 0.05. The sensitivity of the tests ranged between 42 % and 67 %, with the NaNO3 solution showing the highest sensitivity in both the direct and modified centrifugal flotation methods. The modified NaNO3 centrifugal method ranked first with the highest mean egg cell count (45.24 ± 83). The modified centrifugal NaNO3 method was found to be superior (i.e. higher egg counts) and significantly different (p<0.001) compared with the routine saturated sugar, ZnSO4 and MgSO4 flotation methods. The direct flotation method/technique using NaNO3 flotation fluid was also superior and significantly different (p<0.001) when compared to the same technique using ZnSO4 or MgSO4 flotation fluids. Neoplastic transformation of oesophageal nodules was confirmed in 15 % (n=5) of dogs and a further 18 % (n=6) had both neoplastic and non-neoplastic oesophageal nodules. S. lupi eggs were demonstrated in 40 % of dogs with neoplastic nodules and in 72.9 % of dogs with non-neoplastic nodules. The mean egg count in the non-neoplastic group (61) was statistically greater (p=0.02) than that of the neoplastic group (1). The results show that faecal examination using the direct and modified centrifugal flotation methods with the NaNO3 flotation fluid are the most sensitive methods in the diagnosis of spirocercosis. The modified centrifugal flotation method using this solution has the highest mean egg count. The study also found that dogs with neoplastic nodules shed significantly fewer eggs than dogs with non-neoplastic nodules. Copyright / Dissertation (MMedVet)--University of Pretoria, 2011. / Companion Animal Clinical Studies / unrestricted