Epidemiology of Parasitic Nematodes

The nematode parasite Spirocerca lupi causes spirocercosis in canids. It forms nodules in the oesophagous of the dog which may become cancerous and be fatal. Anthelminthic treatment is only effective if administered soon after infestation. Most dogs remain asymptomatic until the disease progression is advanced. At this stage treatment is both risky and expensive.
Nothing is known about the genetic landscape of the S. lupi population. Similarly, there is very little molecular data available. Recent evidence suggests a substantial increase in the reported incidence of the disease over the last ten years. This increase may be due to an increased prevalence or to an increase in the virulence of the parasite.

Spirocerca lupi occurs globally in tropical and sub-tropical areas. The incidence of S. lupi is considerably higher in urban as opposed to rural areas. We have estimated an urban density in the order of 1775 dogs per km2 in South Africa. This high density combined with the observed increased prevalence may result in a breeding ground for more virulent strains of S. lupi. This may in turn serve as a source of infection for wild canids, such as wild dogs, hyenas and jackals, in surrounding areas. Wild canids have much larger territories and are found in much lower densities than urban domestic canids. As such, their immune systems are naïve and contact with a more virulent strain of S. lupi could decimate local populations.

Based on the number of dogs infested with S. lupi, current reports of the incidence of the parasite determined by faecal flotation assays may be an underestimate. The sensitivity of faecal flotation assays is variable. Also, egg shedding is intermittent. Development of diagnostic tools for identification of S. lupi, quantification of population structure over a large region and assessment of genetic variation would greatly enhance our understanding of the dispersal and distribution of the worm. This knowledge would assist in the management and prevention of the disease.
 

Primary Investigator:
Dr Pamela de Waal

Collaborators:
Dr Sarah Clift 
Prof Jaco Greeff
 

Research objectives:
This programme aims to investigate the population structure, prevalence and genetic diversity of Spirocerca lupi in its primary, secondary and paratenic hosts. Specific objectives include:
 

  • The development of diagnostic tools for specific detection;
  • The development of genetic markers for quantification of genetic variation;
  • Evaluation of genetic variation within and between the primary canid host, the secondary coprophagus beetle host and various paratenic hosts;
  • Determining the incidence and genetic variation of S. lupi in wild canids, and
  • Assessing prevalence and genetic diversity of S. lupi at the interface between urban and rural areas.

 

 

Published by Annel Smit

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