Tuesday, November 26, 2013

Dog parasites

The Chinese province of Qinghai on the Qinghai-Tibetan Plateau is one of the most highly endemic areas for Echinococcus parasites. Nomadism of high-altitude adaptive animals,  such as yak and sheep, is very popular, and most farmers keep dogs for protection and for herding.  Together, these conditions favor both endemism and the lifecycle of taeniid cestodes. Dogs are also infected with parasites by eating rodents in the pasture. The prevalence of Echinococcus in humans was determined at 6.1% for Echinococcus granulosus and 5.1% for Echinococcus multilocularis in the Qinghai Province. The prevalence in domestic animals was very high with the reported values reaching over 50 % for Echinococcus granulosus in dogs, yaks and sheep. Dogs also serve as the definitive host for Taenia species which also can infect other domestic animals, such as yaks and sheep, and thus would reduce animal health and affect meat quality. The life cycle of the parasites connects both dogs and livestock (see figure above). 

A variety of methods have been used to diagnose taeniid infection in dogs. One common method for diagnosis in live dogs is the examination of fecal eggs. While this has been difficult in the past as eggs don't show a lot of species specific features DNA Barcoding is used in more recent studies. For a new study, researchers collected dog feces before and after deworming at a pilot site in the Qinghai Province and thereby determined an optimal sampling schedule for egg examination. By using this method, they were able to evaluate the prevalence of taeniid cestodes in dogs at different sites in the Province. Subsequently one site was selected and the team conducted a control trial of taeniid infection in dogs with periodic deworming treatment. 

Analysis of 277 dog feces revealed that taeniid cestodes, including Taenia species and Echinococcus granulosus, were e.g. highly prevalent in one region (34.4%), but no eggs were found in a region where a control trial on canine echinococcosis had been conducted 20 years ago. The first region was chosen for the control trial with the result that he prevalence of taeniid cestodes in the dogs was reduced to 9.6% and 4.9% after one and two years, respectively,  indicating that some dogs did not receive proper treatment. The researchers went back and conducted a survey among the farmers which revealed that most farmers were not familiar with echinococcosis or the transmission route of the disease. All these findings imply that DNA Barcoding utilized for species identification and a program for educating local farmers will greatly improve infection control.

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