Canine echinococcosis in Kyrgyzstan: Using prevalence data adjusted for measurement error to develop transmission dynamics models

Abstract

Echinococcosis is a major emerging zoonosis in central Asia. A cross-sectional study of dogs in four villages in rural Kyrgyzstan was undertaken to investigate the epidemiology and transmission of Echinococcus spp. A total of 466 dogs were examined by arecoline purgation for the presence of Echinococcus granulosus and Echinococcus multilocularis. In addition, a faecal sample from each dog was examined for taeniid eggs. Any taeniid eggs found were investigated using PCR techniques (multiplex and single target PCR) to improve the diagnostic sensitivity by confirming the presence of Echinococcus spp. and to identify E. granulosus strains. A total of 83 (18%) dogs had either E. granulosus adults in purge material and/or E. granulosus eggs in their faeces as confirmed by PCR. Three genotypes of E. granulosus: G1, G4 and the G6/7 complex were shown to be present in these dogs through subsequent sequence analysis. Purge analysis combined with PCR identified 50 dogs that were infected with adult E. multilocularis and/or had E. multilocularis eggs in their faeces (11%). Bayesian techniques were employed to estimate the true prevalence, the diagnostic sensitivity and specificity of the procedures used and the transmission parameters. The sensitivity of arecoline purgation for the detection of echinococcosis in dogs was rather low, with a value of 38% (Credible intervals (CIs) 27-50%) for E. granulosus and 21% (CIs 11-34%) for E. multilocularis. The specificity of arecoline purgation was assumed to be 100%. The sensitivity of coproscopy followed by PCR of the isolated eggs was calculated as 78% (CIs 57-87%) for E. granulosus and 50% (CIs 29-72%) for E. multilocularis with specificity of 93% (CIs 88-96%) and 100% (CIs 97-100), respectively. The 93% specificity of the coprological-PCR for E. granulosus could suggest coprophagia rather than true infections. After adjusting for the sensitivity of the diagnostic procedures, the estimated true prevalence of infection of E. granulosus was 19% (CIs 15-25%) and the infection pressure in the dog population was estimated to be 0.29 infections per year (CIs 0.014-0.75). Logistic regression analysis failed to identify any significant risk factors for infections for E. granulosus. After adjusting for the sensitivity of the test procedures, the estimated true prevalence was 18% (CIs 12-30%). Dogs that were restrained had a significantly lower prevalence of E. multilocularis of 11% (CIs 6-29%) compared with 26% in free-roaming dogs (CIs 17-44%) and

Echinococcosis in pigs and intestinal infection with Echinococcus spp. in dogs in southwestern Lithuania

“…In contrast to other E. granulosus endemic areas, where several genotypes can coexist and can be identified in the domestic dog as the definitive host (Ziadinov et al, 2008), the identification of the E. granulosus genotype G6/7 in all E. granulosus egg isolates from dogs and from all isolates of pig and cattle origin indicate that the pig strain predominates in Lithuania. This hypothesis is further supported by the fact that E. granulosus cysts had only occasionally been recorded in cattle (0.8%) and sheep (2.7%) in a previous study (Danilevičius, 1964).…”

“…The egg F/Si method was recently also shown to have a higher sensitivity for the diagnosis of Echinococcus spp. in dogs (78% for E. granulosus and 50% for E. multilocularis) when compared to arecoline purgation (Ziadinov et al, 2008).…”

Trophic ecology, behaviour and host population dynamics in Echinococcus multilocularis transmission

“…A few studies investigated the contamination of dog populations with E. multilocularis on the mid-and high-altitude grasslands (2000-4500 m) of central Asia, including southeast Kyrgyzstan and central and western China (Sichuan, Qinghai and Xinjiang provinces) where pastoralism is the main activity (Budke et al, 2005;Wang et al, 2007Wang et al, , 2010Ziadinov et al, 2008;Vaniscotte et al, 2011;Van Kesteren et al, 2013). These open landscapes are known to favour population outbreaks of a variety of small mammal species shown to be E. multilocularis intermediate hosts: Ochotona curzoniae and Ochotona cansus, Microtus limnophilus, Cricetulus kamensis in the eastern Tibetan plateau of central China, Ellobius tancrei and Microtus gregalis in Kyrgyzstan .…”

“…teeth were retrieved from one sample). In the high plateau of Kyrgyzstan, Ziadinov et al (2008) showed that domestic dogs that were allowed to completely roam or roam for part of the time and that were used for hunting were more likely to be infected with E. multilocularis based on arecoline purgation combined with PCR diagnosis (11% vs. 26% for tied and non-tied dogs, respectively). A similar result was observed on the eastern Tibetan plateau of western Sichuan (Budke et al, 2005).…”

Ulnar mononeuropathy associated with eosinophilia

“…Classical approaches such as conducting faecal egg examination alone did not provide adequate information for parasite identification especially for the parasites producing morphologically similar eggs. However, as shown in this and in earlier studies (Bruzinskaite et al, 2009;Davidson et al, 2009;Ziadinov et al, 2008), faecal egg examination in combination with the recently developed molecular techniques would provide results with more accuracy, and being a useful tool in surveys of zoonotic parasite infections in dogs.…”