One Health initiative in the Bolivian Altiplano human fascioliasis hyperendemic area: Lymnaeid biology, population dynamics, microecology and climatic factor influences

Abstract

Fascioliasis is a freshwater snail-borne zoonotic disease. The Northern Bolivian Altiplano is a very high altitude endemic area where the highest human prevalences and intensities have been reported. Preventive chemotherapy by treatment campaigns is yearly applied. However, liver fluke infection of cattle, sheep, pigs and donkeys assures endemicity and consequent human infection and re-infection risks. A One Health action has therefore been implemented. Activity concerns lymnaeid vectors and environment diversity. Studies included growth, egg-laying and life span in laboratory-reared lymnaeids. Different habitat types and influencing factors were assessed. All populations proved to belong to Galba truncatula by rDNA sequencing. Analyses comprised physico-chemical characteristics and monthly follow-up of water temperature, pH and quantity, and lymnaeid abundance and density. Population dynamics in the transmission foci differed. Mean environmental temperature was lower than fluke development minimum temperature threshold, but water temperature was higher, except during winter. A two generations/year pattern appeared in permanent water habitats, and one generation/year pattern in habitats drying out for months. The multidisciplinary control measures can be extended from one part of the endemic area to another. These studies, made for the first time at very high altitude, constitute a baseline useful for fascioliasis control in other countries.

One Health Action against Human Fascioliasis in the Bolivian Altiplano: Food, Water, Housing, Behavioural Traditions, Social Aspects, and Livestock Management Linked to Disease Transmission and Infection Sources

“…Only results on the physico-chemical composition of the water, and of air and water temperature in these collections have been published in previous reports [27,51]. To assess the stability of the transmission foci, a total of nine foci were selected for re-visits and reanalyses throughout all seasons and months of the year [51], as well as along different years between 1992 up to 2019 to ascertain potential long-term modifications due to influences of climate change and anthropogenic modifications of the environment [46].…”

“…DNA multi-marker sequencing showed that there is a monomorphic, genetically unique strain, which pronouncedly simplifies control measures because of their homogeneous ecology and ethology [46]. A wide environmental and climatic assessment of the distribution of lymnaeid snails demonstrated that most of the Altiplanic vector populations are linked to permanent freshwater collections [51]. However, recent field surveys of transmission foci showed that the endemic area is spreading thanks to an adaptation to higher altitudes.…”

“…Assessing the distribution of lymnaeid snails allowing for liver fluke transmission: Lymnaeid snails were differentiated from other freshwater snails by their pair of triangular tentacles with darkly pigmented eyes at their bases and their typical small, smooth, and dextral conical shell. In the Northern Altiplano, there are no other snails in the freshwater collections which may be confused with lymnaeids [51]. To distinguish between lymnaeid species with liver fluke transmission capacity, i.e., lymnaeid intermediate hosts or vectors, and non-transmitting lymnaeid species potentially present because known to also inhabit Andean high altitude areas [22], lymnaeids from each population collected were molecularly characterized by the sequencing of two ribosomal DNA markers (ITS-2 and ITS-1) and two mitochondrial DNA markers (16S and cox1).…”

“…Municipalities directly involved because they include transmission foci and those affected due to close neighbourhoods are shown in Figure 2. To ascertain the stability of the endemic area, field studies were performed both throughout all seasons and months of the year [51] and along different years of the 1990, 2000, and 2010 decades.…”

Fascioliasis in Llama, Lama glama, in Andean Endemic Areas: Experimental Transmission Capacity by the High Altitude Snail Vector Galba truncatula and Epidemiological Analysis of Its Reservoir Role

“…In these areas, the aforementioned preventive chemotherapy strategy is now being complemented by One Health interventions to decrease the risks of infection and reinfection. Control measures implemented within these interventions include the assessment of the contributions of the different livestock reservoir species to the transmission and epidemiology of the disease [24][25][26], among many other action axes [27][28][29].…”