Canine echinococcosis in the eastern Tibetian plateau

Moss, J

Abstract

Echinococcosis caused by E.granulosus or E.multilocularis is a chronic, debilitating and
potentially fatal zoonotic cestode disease of humans. The natural primary definitive host for
E.granulosus is the domestic dog and for E.multilocularis it is wild foxes. In areas of the
eastern Tibetan plateau, it was suspected that the domestic dog played a vital role in the
transmission of both species of parasite to man, contributing to some of the highest
prevalence rates globally. A new species, E.shiquicus is distributed sympatrically in the same
location but its zoonotic potential was unknown. In order to investigate the role of canids in
transmission of E.shiquicus, E.granulosus and E.multilocularis, 197 faecal samples from
Tibetan foxes (Vulpes ferrilata) in Sichuan, Qinghai and Tibet Autonmous Region (TAR) and
more than 600 faecal samples from owned domestic dogs in Sichuan were collected and
analysed by an Echinococcus genus specific coproantigen- ELISA and three species specific
copro-PCR tests. The copro-ELISA was shown to have a sensitivity of 86.6% for E.granulosus
and 72.7% for E.multilocularis. The specificity was 100% when compared with faecal samples
from other taeniid tapeworm infections. Copro-PCR tests were considered the most specific
for use in the eastern Tibetan plateau co-endemic communities. The primary objective
endeavoured to understand the role of the domestic dog in maintaining transmission of
E.multilocularis in Shiqu County, Sichuan. A cohort of 308 dogs were followed up for one
year after a single treatment with praziquantel for a re-infection study at 2 month, 5 months
and 12 months. This research was the first to confirm E.multilocularis is found in foxes across
the plateau into central TAR. The prevalence ranged from 2.6% to 25% dependant on
location. In foxes E.shiquicus was distributed ~350 miles west of Shiqu County (where it was
first described) at a prevalence of 6.1% and the prevalence appeared to be increasing along
a gradient from north to south of the plateau. No dog faecal samples were positive for
E.shiquicus DNA. The prevalence of E.multilocularis in dogs reached 8.9% in one endemic foci
(Shiqu County) whilst E.granulosus was distributed evenly across the study sites. There was
no significant difference between the prevalence of E.multilocularis in the dog and fox
populations. The re-infection study of dogs demonstrated they are Echinococcus copro-ELISA
test positive at a prevalence of 8.4% after 2 months, 2.2% after 5 months and 9.5% after 12
months. No positive copro-PCR results were obtained at 5 months and 12 month post
treatment however knowledge of the parasite biology and host availability/behaviour meant
that some assumptions could be made. It was considered that the infection pressure to dogs
from small mammals infected with E.multilocularis is at a peak in the late spring to early
summer whilst the infection pressure from livestock infected with E.granulosus to dogs is at
a peak in late autumn to early winter. Furthermore, the data indicated that dogs may have
the ability to maintain E.multilocularis transmission without the input of a fox definitive host.
This was based on the significant reduction in copro-prevalence 12 months post treatment
and the probable effect the dosing had on transmission of E.multilocularis to small mammals
in the research area. The only significant risk factor for dog echinococcosis in the current
study was the release of dogs at night by owners which allows them to roam in the villages.
It was thought that these dogs have more access to small mammals or livestock carcasses
infected with Echinococcus spp. Identification of peak Echinococcus transmission periods are
discussed with a view to control via dog dosing schemes on the plateau.

Citation

Moss, J. Canine echinococcosis in the eastern Tibetian plateau. (Thesis). Salford : University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 3, 2012
• Award Date: Jan 1, 2011