Characterization of Spirocerca lupi in wild and domestic canids

Abstract

Spirocerca lupi is a parasitic nematode that causes spirocercosis predominantly in domestic dogs. This disease is often fatal if not detected early before malignant transformation occurs. The nematodes may also cause serious aortic lesions which may weaken arteries and cause fatal haemorrhaging. There is currently no cure for the disease. Coprophagous dung beetles serve as intermediate hosts for the parasite. Lizards and birds serve as paratenic hosts when they consume dung beetles containing infective larvae. Spirocerca lupi may pose a threat to wild carnivores due to the encroachment of humans with domestic dog pets near wildlife borders. There is very little information available regarding the spread of S. lupi among wild carnivores. In this study nematodes were collected from black backed jackals as well as several domestic dogs around the country. Corresponding haplotypes of cox1 were identified in the black backed jackals and domestic dogs. This is a clear indication of gene flow of S. lupi between these two species. Phylogenetic analysis indicates that S. lupi from South Africa may be a cryptic species. Further analysis is still required to confirm this as only a small section of the cox1 gene was used during the analysis. Further investigation with a larger section of the cox1 gene as well as other genes may be required to further classify S. lupi in South Africa as well as other countries around the world. To further investigate the role of S. lupi infection among wild carnivores a faecal DNA extraction method was designed to screen these carnivores. Many challenges were encountered since S. lupi egg shedding is irregular and faecal samples from various wild carnivores were not always of the correct consistency to be analysed. The eggs of S. lupi were also found to be very resilient and did not yield easily to disruption. Other nematodes were identified with these methods indicating that it is a potential option for other nematodes but not for S. lupi. In addition to these challenges, the methods tested were found to be time consuming and costly without reliable repeatability. Several adult S. lupi nematodes were tested for endosymbiotic bacteria. Targeting endosymbiotic bacteria with antibiotics could be an alternative treatment for nematode infection. No endosymbiotic bacteria were detected in S. lupi from South Africa with the primers tested. Further analysis may yet reveal some symbiotic relationship but current results do not suggest that is a feasible option for alternative treatment.