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

Abstract

South American camelids are definitive hosts of Fasciola hepatica. However, their capacity to participate in the transmission and epidemiology of fascioliasis has never been appropriately studied. Therefore, an F. hepatica isolate from Argentine llama is for the first time analyzed using Galba truncatula lymnaeids from Bolivia. Experimental follow-up studies included egg embryogenesis, miracidial infection of lymnaeid snails, intramolluscan larval development, cercarial production, chronobiology of cercarial shedding, vector survival to infection, and metacercarial infectivity of mammal host. Shorter prepatent and patent periods were leading to markedly lower cercarial production, shorter cercarial shedding, and a higher negative impact on snail survival. The usually low liver fluke prevalences and intensities and low daily fecal outputs indicate that llamas do not substantially contribute to fascioliasis transmission. The defecating behavior in dung piles far from freshwater collections prevents lymnaeid infection by eggs shed by this camelid. All results suggest the reservoir role of the llama to be negligible and, therefore, no priority within control measures in endemic areas. However, llamas may play a disease-spreading role if used as pack animals in rural areas. In the Northern Bolivian Altiplano human hyperendemic area, neither llamas nor alpacas should be considered for control measures within a One Health action.

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

“…Llamas and alpacas are present in the Northern Altiplano (Figure 9(Ba)) and are known definitive hosts for F. hepatica, but a potential role as reservoirs has been ruled out, as recently proved by experimental and field studies [50]: (i) the liver fluke transmission capacity of llama isolates is not sufficiently efficient; (ii) they do not show liver fluke infection in the Altiplano because they are present in zones where dryness, absence of freshwater collections, and higher altitudes do not allow lymnaeids to be present; (iii) the dung-pile defaecation behaviour of these camelids, always far from freshwater collection, does not allow liver fluke eggs shed by these animals to reach water and infect lymnaeids [50]. Infection of alpacas has been reported from the Northern Bolivian Altiplano, but this only concerned the farm of Belen [76], which is outside the human endemic area.…”

“…Field studies inside the human endemic area were never able to find F. hepatica infection in these camelids. Therefore, control measures for South American camelids are not needed in the Northern Altiplano [50].…”

“…The donkey demonstrated that it was the fourth reservoir species involved, with a problematic role in the geographical diffusion of both liver fluke and snail vector [49]. The llama, previously suggested to participate in the disease transmission in the Altiplano, showed an insufficient transmission capacity and a specific defaecating behaviour which allowed us to neglect South American camelids as reservoirs and consequently indicated that there was no need to include them in control measures [50].…”

“…Donkeys are used for good transport [49]. Llamas and alpacas are very few throughout the endemic area, although several may be seen in the northern part, as in the subcorridor of Peñas and the farms of Belen [50], and meat of llama is sporadically consumed.…”

Host–Parasite Relationships in Veterinary Parasitology: Get to Know Your Enemy before Fighting It

“…This fact has encouraged the development of alternative treatment or other control strategies, such as vaccination trials, for which understanding the cross-talk interactions between hosts and parasites is of paramount importance. The study published by Mas-Coma et al [ 7 ] explored the capacity of llamas to participate in the transmission and epidemiology of fasciolosis in South America. The results showed that although eggs shed by these animals might eventually reach the adult stage, their transmission capacity should be considered negligible, and therefore, llamas should not be considered for control initiatives in fasciolosis.…”