High Prevalence of the Liver Fluke Amphimerus sp. in Domestic Cats and Dogs in an Area for Human Amphimeriasis in Ecuador

Abstract

Background Amphimerus sp. is a liver fluke which recently has been shown to have a high prevalence of infection among an indigenous group, Chachi, who reside in a tropical rainforest in the northwestern region of Ecuador. Since it is unknown which animals can act as a reservoir and/or definitive hosts for Amphimerus sp. in this endemic area, a study was done to determine the prevalence of infection in domestic cats and dogs. This information is important to understand the epidemiology, life cycle and control of this parasite.Methodology/FindingsIn July 2012, three Chachi communities located on Rio Cayapas, province of Esmeraldas, were surveyed. A total of 89 of the 109 registered households participated in the study. Of the 27 cats and 43 dogs found residing in the communities, stool samples were collected from 14 cats and 31 dogs (total of 45 animals) and examined microscopically for the presence of Amphimerus eggs. The prevalence of infection was 71.4% in cats and 38.7% in dogs, with similar rates of infection in all three communities. Significantly more cats were infected than dogs (p = 0.042).Conclusions/SignificanceThe data show a high rate of Amphimerus sp. infection in domestic cats and dogs residing in Chachi communities. It can be concluded that these animals act as definitive and reservoir hosts for this liver fluke and that amphimeriasis is a zoonotic disease. These findings provide important epidemiological data which will aid in the development and implementation of control strategies against the transmission of Amphimerus.

A comparison of Kato-Katz technique to three other methods for diagnosis of Amphimerus spp. liver fluke infection and the prevalence of infection in Chachi Amerindians of Ecuador

“…It is important to note that trematode species-specific diagnosis based on egg morphology poses a problem for liver flukes of the Opisthorchiidae and for minute intestinal flukes of Heterophyidae families [ 27 ]. The size and shapes of eggs of the members of the above-mentioned families are similar to Amphimerus eggs [ 1 , 2 ]. However, these liver and intestinal flukes have not been reported in humans of the Americas [ 3 ].…”

“…The only means of transportation to reach this community is by boat and is located approximately ~135 km inland from the coast. The ecosystem and characteristics of the region has been described in previous studies [ 1 , 2 , 15 , 16 ].…”

“…The prevalence, which varied from 15.5 to 34.1%, was associated with the inland distance from the coast [ 1 ]. More recently, a high prevalence of infection in cats and dogs living in the same communities where humans were infected was documented [ 2 ]. Amphimerus is a genus of trematodes belonging to the Opisthorchiidae family.…”

“…Amphimerus has not been reported in other geographical regions such as Africa, Oceania, or Europe. Adult worms are hermaphrodites that parasitize the bile ducts and gall bladder, eliminating their eggs via stools, thus, microscopy examination of stool samples searching for eggs is the most commonly used technique for diagnosing Amphimerus infection [ 1 , 2 ]. Recently, an ELISA to detect anti- Amphimerus IgG in human serum, and LAMPhimerus to detect DNA in feces have been developed [ 7 , 8 ].…”

“…In the previous studies of human and domestic animals in Ecuador, diagnosis was made by microscopic observation of Amphimerus eggs in stools [ 1 , 2 ]. The only coproparasitological technique used was the formalin-ether concentration (FEC) because the direct smear microscopy (DM) showed a low sensitivity [ 1 ].…”