Report of Pseudosuccinea columella, infected with Fasciola hepatica at Sierra de los Cuchumatanes, Guatemala

Objective. Identify the natural infection of freshwater snails as an intermediate host of Fasciola hepatica in Guatemala. Materials and methods. Freshwater snails were collected in a highaltitude village (3.000 mamsl) from Huehuetenango department, where fasciolasis is endemic. The identification of the snail species was based on the morphological characteristics observed under the stereoscope using an identification key. The trematode phases were searched externally by visual inspection using a light source, and internally by dissection and visual inspection of the tissues under a stereoscope and microscope. Results. 260 snails were found and identified as Pseudosuccinea columella. Two of them were found naturally infected with larval phases of F. hepatica. Conclusions. This is the first report of P. columella carrying phases of F. hepatica in the highlands of Guatemala. It is necessary to increase the research of the ecology of this parasite in other understudied areas in Guatemala and Central America, due to the latent risk of infection for populations of herbivorous animals and humans.


INTRODUCTION
Fascioliasis is a parasitic disease affecting humans and animals. It is associated with the cattle and sheep production in endemic tropical areas (1). Fasciola hepatica (Linnaeus, 1761) is the species of liver fluke present in America. A fundamental part of the life cycle of this trematode is carried out in a freshwater snail intermediate host (2). After the hatching of the eggs, the miracidium seeks and penetrates a snail, developing various parasitic phases (sporocyst, redia and cercaria). The cercariae abandon the snail and become infective metacercariae encysted in the aquatic vegetation, being then consumed by herbivorous animals or humans. In Latin America, fascioliasis is frequently reported in Bolivia, Paraguay and Argentina (3,4). However, the notification of the clinical cases is scarce in poor countries, where this illness is classified as a Neglected Tropical Disease (NTD) (5).
Pseudosuccinea (Lymnaea) columella (Say, 1817) was first reported in Guatemala in 1982 by Paraense. The specimen was collected at ~1,500 mamsl in Purulhá locality at Baja Verapaz department ( Figure 1). Nevertheless, this species of snail has never been looked for in other locations, in the highlands of Guatemala, were human fascioliasis cases have been reported (6). The main purpose of this communication is to report for the first time the natural infection of Pseudosuccinea columella with F. hepatica in the highlands of Guatemala.

MATERIALS AND METHODS
Sampling was carried out during the dry season of 2008 in Paquix locality, at Huehuetenango department in Guatemala (Figure 1, dot 1). This area belongs to the Sierra de los Cuchumatanes mountainous system, at 3,300 mamsl, were sheep breeding and watercress cultivation (Nasturtium officinale, W.T. Aiton 1812) are the livelihood for native persons. We collected snails along water creeks and transferred live specimens in plastic boxes to the parasitology laboratory at the veterinary faculty of University of San Carlos in Guatemala City. The identification was based on the morphological description provided by Paraense (7) and the identification key of freshwater snails provided by Burch (8). The shell was measured to 0.1mm using a caliper. The search for possible infected snails with trematode phases was made by visual inspection using a stereoscope and a light source for transillumination. Furthermore, dissection and visual internal inspection under stereoscope and microscope was made to confirm the presence of parasites phases.

RESULT
We collected 260 snails ( Figure 1) in a water creek (15°26'03.4"N, 91°26'50.2"W). Two individuals were positive to trematode phases by visual inspection. Shell morphology of the collected snails was consistent with the characteristics of P. columella described by Paraense and Burch (shell succiniform, thin and fragile, with a large, oval aperture and body whorl, and small spire; surface sculptured with microscopic, raised, spiral periostracal threads, [ Figure 2]).

DISCUSSION
This is the first report of P. columella with natural infection of F. hepatica in the highlands of Guatemala. We assume that the dispersion of this snail species covers different altitudes of  (9).
In terms of NTD it is important to recognize the need to establish a specific monitoring program for zoonotic fascioliasis in Guatemala. For human onchocerciasis, another parasitic NTD in Huehuetenango caused by Onchocerca volvulus (Leuckart, 1894), a surveillance program of World Health Organization and the local health system, confirmed the prevalence, and made possible the interruption the transmission using mass treatment (10). Until now, some unofficial reports at the same locality of our snail collection, refer fascioliasis cases in children and adults (11).
P. colummella has been confirmed as intermediate host of F. hepatica in Egypt, New Zealand, Brazil, Argentina, France and Cuba (9,12,13,14,15,16). The presence of trematode phases inside the mollusks by visual inspection is valid to report natural infection (16). It is important to replicate these efforts in different regions of Central America, exploring the possibility of strict absence given the variation of altitudes (between zero and 4000 mamsl) and the identified potential zoonotic risk areas.

Conflict of interest
The authors declare that there is no conflict of interests.