Past and present of cystic echinococcosis in Bolivia

Abstract

Viable eggs of the canine intestinal tapeworm Echinococcus granulosus sensu lato (s.l.) infect various intermediate hosts causing cystic echinococcosis (CE). Furthermore, CE represents a serious zoonosis causing a significant global burden of disease. CE is highly endemic in South America, including Argentina, Brazil, Chile, Uruguay, and Peru. For Bolivia, no official data concerning the incidence in humans or the number of livestock and dogs infected are available. However, it is well known that CE occurs in Bolivia. We aim here to fill the gap in the current knowledge of the epidemiological situation of CE in Bolivia, providing a historical overview of documents published within the country, which have never been comprehensively reviewed. The very first documentation of E. granulosus infection in animals dates in 1910, while the first human case was reported in 1913. In total, 876 human CE cases have been reported in the scientific literature, with an apparent increase since the 1970s. In the absence of other epidemiological studies, the highest prevalence in human comes from Tupiza, Potosí Department, where 4.1% (51/1,268) of the population showed signs of CE at mass ultrasound screening in 2011. In the same report, 24% of dog faecal samples were positive for coproantigens of E. granulosus s.l. in ELISA. The highest prevalence in intermediate hosts reported at abattoir reached 37.5% in cattle from Potosí, followed by 26.9% in llamas from Oruro, 2.4% in pigs and 1.4% in sheep from La Paz. Finally, Echinococcus granulosus sensu stricto (s.s.), Echinococcus ortleppi (G5), and Echinococcus intermedius (G7) have been identified in Bolivia. Data reviewed here confirm that E. granulosus s.l. is circulating in Bolivia and that a proper prospective nationwide epidemiological study of CE is urgently needed to define transmission patterns as a basis for the planning and implementation of future control measurements.

Fig 1. Distribution of human CE cases in Bolivia reviewed in this study from case reports and retrospective studies; maximum and minimum prevalence recorded in livestock at official postmortem examination at abattoir; and in dogs established at necropsy, arecoline purgation, after treatment with praziquantel, copro-ELISA, and PCR/sequencing.

In total, there are 38 human case reports (for 2 cases, the origin is unknown) and 517 cases from retrospective studies; only 284 cases were included in the figure due to the lack of information about the origin of the patients. Original base layer of the map can be found here: https://commons.wikimedia.org/wiki/File:Bolivia_departments_blank.png. CR, case report; PM, postmortem; PZQ, praziquantel; RS, retrospective study.