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New records of Ornithodoros puertoricensis Fox 1947 (Ixodida: Argasidae) parasitizing humans in rural and urban dwellings, Panama

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Abstract

The presence of ticks inside human constructions was evaluated in two localities from Colon province (Charco La Piedra and Espinar) and one from Panama province (Ancon, City of Panama). In two of houses, eight people from Charco La Piedra and one from Ancón reported “insect bites,” which produced blisters for several weeks. The investigation resulted in the collection of argasid ticks, which were identified by morphology and sequencing the 16 s ribosomal RNA gene, and later evaluated for the presence of relapsing fever Borrelia DNA. All ticks were identified as Ornithodoros puertoricensis. While spirochetal DNA was not detected by PCR in the ticks, our report highlights the potential for relapsing fever borreliosis in rural and urban localities in Panama.

Introduction

The genus Ornithodoros Koch genus comprises approximately 120 species worldwide, and near 60 species occur in the Neotropics (Nava et al., 2013, Venzal et al., 2015, Muñoz-Leal et al., 2016). These ticks are parasites of a wide range of vertebrates, and similar to other Argasidae, Ornithodoros spp. primarily inhabit host burrows or nests (Vial, 2009, Gray et al., 2014). In anthropic environments, Ornithodoros spp. can survive parasitizing both domestic animals and humans, and thus representing a public health concern (Vargas, 1984, Labruna et al., 2014, Gray et al., 2014). Bites of Ornithodoros spp. can cause irritation, allergies, toxicosis, or paralysis (Vargas, 1984, Mans et al., 2008, Reck et al., 2011), and are also vectors of pathogenic microorganisms (Labuda and Nuttall, 2008, Vial, 2009, Cutler et al., 2012).

In Panama, several studies from 1907 to 1944 described the ecology of Ornithodoros ticks and its relationships with cases of tick-borne relapsing fever (TBRF) (Bates et al., 1921, Dunn, 1933, Dunn and Clark, 1933). During these years, over 120 cases of TBRF were confirmed; however, because the patients came from Panama City and villages around the former Canal Zone the reports likely represented a fraction of the total cases (Dunn and Clark, 1933, Calero, 1946). Argasid Tick species reported to bite humans in Panama include Ornithodoros rudis Karsch, 1880 (cited as Ornithodoros venezuelensis), Ornithodoros talaje (Guérin-Méneville, 1849) and Ornithodoros puertoricensis Fox, 1947; however, only O. talaje and O. rudis were implicated as vectors of TBRF (Dunn, 1933, Dunn and Clark, 1933).

Since 1944, there has been a paucity of studies reporting human exposure to Ornithodoros ticks or TBRF in Panama, which may be attributed to the extensive use of insecticides for malaria control and its secondary lethal effect in soft tick populations (Fairchild et al., 1966). Recently, Ornithodoros ticks have been reported in human houses in Panama (Rangel and Bermúdez, 2013, Bermúdez et al., 2013, Bermúdez et al., 2015). In this current report we present recent findings of people parasitized by O. puertoricensis in rural and urban localities of Panama.

Section snippets

Investigation sites

From March-April 2015 two houses where inhabitants complained of “insect bites” and a former U.S. Army bunker were investigated by personnel from the Departamento de Control de Vectores (DCV) and Instituto Conmemorativo Gorgas de Estudios de la Salud (ICGES).

Site 1

The first house was located in the rural community of Charco La Piedra, in Colon province (9° 31′14.60″ N, 79° 19′40.62″ W) (Fig. 1A and B). The house had a large paddock that covers approximately 12,000 m2 around the house. The residence

Results

In Charco La Piedra and Ancón a total of 42 ticks were collected, correspond to 23 nymphs and 19 adults (11 females and eight males). In the sample of the substrate from Espinar, we found a proportion of 23% larvae, 59% nymphs and 18% adults. In the laboratory, we obtained the offspring from three engorged females, and collected 20 of the F1 larvae for morphological studies.

Discussion

We report the presence of O. puertoricensis parasitizing humans in rural and urban settings, which is the first indication of this species impacting human health in Panama in recent years. The damage produced by bites of Ornithodoros varies according to the affected individual (Dunn, 1933, Dantas-Torres et al., 2012), a fact that was also noted during this study. All bitten people exhibited blisters and lesions during the following weeks; however, patients from Charco La Piedra reported that

Acknowledgments

We thanks Julio De León, Agustín Rodríguez, Víctor Herrera and Ramón Garcia (Vectors Control) and Samaniego family for their assistance in Charco La Piedra; Gesabel Navarro, Nadili Lassen, John Cleghorn and Rito Herrera, for their assistance in the collection from Ancón and Espinar; Lance Durden for his final revision. This work was partially supported by grant AI123652 (National Institutes of Health).

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