Liliana Semenas

Bio: Liliana Semenas is an academic researcher from National University of Comahue. The author has contributed to research in topics: Galaxias maculatus & Galaxiidae. The author has an hindex of 14, co-authored 45 publications receiving 471 citations.

Component population study of Acanthocephalus tumescens (Acanthocephala) in fishes from Lake Moreno, Argentina.

Abstract: Seasonal samples of all fish species from Lake Moreno were taken in order to determine the presence of paratenia, to evaluate the status of the hosts and to characterise the transmission of Acanthocephalus tumescens (von Linstow, 1896) at the component population level. Prevalence, mean abundance, mean intensity, numbers of gravid females, relative abundance of the different fish species, relative output of eggs and relative flow rates for each host species were computed. Acanthocephalus tumescens showed low host specificity, successfully parasitizing six out of eight fish species present in the lake. No paratenic infection was registered. If prevalence, mean abundance, and number of gravid females are considered, host species can be placed in a continuum from the most to least suitable as follows: Galaxias platei Steindachner, Diplomystes viedmensis (Mac Donagh), Oncorhynchus mykiss (Walbaum), Salvelinus fontinalis (Mitchill), Percichthys trucha (Cuvier et Valenciennes) and Galaxias maculatus (Jenyns). However, when parasite flow rates and egg output were calculated, including relative abundance of each fish species, the continuum was rearranged as follows: P. trucha, O. mykiss, G. platei / G. maculatus, S. fontinalis and D. viedmensis. The first four species would be the main contributors to the population of A. tumescens in this lake, P. trucha being the major one. Different regulatory and non-regulatory mechanisms are suggested.

New cases of human diphyllobothriosis in Patagonia, Argentine

Abstract: The purpose of the paper is to describe 4 new cases of human diphyllobothriosis in Patagonia, Argentine. Adult parasites recovered were submitted to morphological and histological analyses for taxonomic identification. The etiological agent found was always Diphyllobothrium latum and all the cases were autochthonous. These data combined with previous information make the number of autochthonous human cases of diphyllobothriosis registered in Argentina increase to 18.

Metazoan Parasites of Galaxias maculatus (Osmeriformes: Galaxiidae) from Argentinean Patagonia

Abstract: A checklist, based on bibliographical records and original data from an extensive survey, is presented for the metazoan parasites of Galaxias maculatus (Jenyns, 1842) in Argentinean Patagonia The checklist includes 33 metazoan parasite entries: 5 myxozoans, 12 digeneans, 2 monogeneans, 3 cestodes, 2 acanthocephalans, 7 nematodes, 1 copepod, and 1 bivalve Gyrodactylus sp, Pomphorhynchus patagonicus Ortubay, Ubeda, Semenas and Kennedy, 1991, and Hysterothylacium patagonense Moravec, Urawa and Coria, 1997 are reported for the first time from G maculatus in South America Although this checklist enlarges the knowledge of G maculatus parasites, a large portion of Patagonia remains unexplored, and many of its lakes and rivers have never been surveyed for parasites, especially in the southern part of the region

Gastrointestinal human myiasis for Eristalis tenax

Abstract: Foram caracterizadas as miasis registradas em Bariloche (Patagonia, Argentina) e estabelecidas as provaveis condicoes sob as quais sao produzidas as infestacoes. As larvas obtidas a partir das fezes de dois pacientes foram identificadas como Eristalis tenax (Diptera: Syrphdae). Esses dois casos de miasis gastrointestinal humana foram os primeiros registrados em Bariloche, Argentina, e suas caracteristicas respondem as registradas para esta especie de Diptera em outras partes do mundo. A falta de controle especifico no sistema domiciliario de abastecimento de agua tem sido a causa mais provavel de infestacao. Este registro amplia a distribuicao de E. tenax e das miasis gastrointestinais humanas em America do Sul ate os 41o 03's.

Parasite spillback: A neglected concept in invasion ecology?

Abstract: While there is good evidence linking animal introductions to impacts on native communities via disease emergence, our understanding of how such impacts occur is incomplete. Invasion ecologists have focused on the disease risks to native communities through "spillover" of infectious agents introduced with nonindigenous hosts, while overlooking a potentially more common mechanism of impact, that of "parasite spillback." We hypothesize that parasite spillback could occur when a nonindigenous species is a competent host for a native parasite, with the presence of the additional host increasing disease impacts in native species. Despite its lack of formalization in all recent reviews of the role of parasites in species introductions, aspects of the invasion process actually favor parasite spillback over spillover. We specifically review the animal-parasite literature and show that native species (arthropods, parasitoids, protozoa, and helminths) account for 67% of the parasite fauna of nonindigenous animals from a range of taxonomic groups. We show that nonindigenous species can be highly competent hosts for such parasites and provide evidence that infection by native parasites does spillback from nonindigenous species to native host species, with effects at both the host individual and population scale. We conclude by calling for greater recognition of parasite spillback as a potential threat to native species, discuss possible reasons for its neglect by invasion ecologists, and identify future research directions.

Update on the Human Broad Tapeworm (Genus Diphyllobothrium), Including Clinical Relevance

Abstract: Summary: Tapeworms (Cestoda) continue to be an important cause of morbidity in humans worldwide. Diphyllobothriosis, a human disease caused by tapeworms of the genus Diphyllobothrium, is the most important fish-borne zoonosis caused by a cestode parasite. Up to 20 million humans are estimated to be infected worldwide. Besides humans, definitive hosts of Diphyllobothrium include piscivorous birds and mammals, which represent a significant zoonotic reservoir. The second intermediate hosts include both freshwater and marine fish, especially anadromous species such as salmonids. The zoonosis occurs most commonly in countries where the consumption of raw or marinated fish is a frequent practice. Due to the increasing popularity of dishes utilizing uncooked fish, numerous cases of human infections have appeared recently, even in the most developed countries. As many as 14 valid species of Diphyllobothrium can cause human diphyllobothriosis, with D. latum and D. nihonkaiense being the most important pathogens. In this paper, all taxa from humans reported are reviewed, with brief information on their life history and their current distribution. Data on diagnostics, epidemiology, clinical relevance, and control of the disease are also summarized. The importance of reliable identification of human-infecting species with molecular tools (sequences of mitochondrial genes) as well as the necessity of epidemiological studies aimed at determining the sources of infections are pointed out.

Unified terminology for cestode microtriches: a proposal from the International Workshops on Cestode Systematics in 2002-2008.

Abstract: Terminology for microtriches, the surface features both unique to and ubiquitous among cestodes, is standardised based on discussions that occurred at the International Workshops on Cestode Systematics in Storrs, Connecticut, USA in 2002, in Ceske Budejovice, Czech Republic in 2005 and in Smolenice, Slovakia in 2008. The following terms were endorsed for the components of individual microtriches: The distal, electron-dense portion is the cap, the proximal more electron-lucent region is the base. These two elements are separated from one another by the baseplate. The base is composed of, among other elements, microfilaments. The cap is composed of cap tubules. The electron-lucent central portion of the base is referred to as the core. The core may be surrounded by an electron-dense tunic. The entire microthrix is bounded by a plasma membrane, the external layer of which is referred to as the glycocalyx. Two distinct sizes of microtriches are recognised: those 200 nm in basal width, termed spinitriches. Filitriches are considered to occur in three lengths: papilliform ( 6 times as long as wide). In instances in which filitriches appear to be doubled at their base, the modifier duplicated is used. Spinitriches are much more variable in form. At present a total of 25 spinithrix shapes are recognised. These consist of 13 in which the width greatly exceeds the thickness (i.e., bifid, bifurcate, cordate, gladiate, hamulate, lanceolate, lineate, lingulate, palmate, pectinate, spathulate, trifid, and trifurcate), and 12 in which width and thickness are approximately equal (i.e., chelate, clavate, columnar, coniform, costate, cyrillionate, hastate, rostrate, scolopate, stellate, trullate, and uncinate). Spiniform microtriches can bear marginal (serrate) and/or dorsoventral (gongylate) elaborations; they can also bear apical features (aristate). The latter two modifiers should be used only if the features are present. The terminology to describe the overall form of a spinithrix should be used in the following order: tip, margins, shape. Each type of microthrix variation is defined and illustrated with one or more scanning electron micrographs. An indication of the taxa in which each of the microthrix forms is found is also provided.

Biological invasions and the dynamics of endemic diseases in freshwater ecosystems

Abstract: Summary 1. Biological invasions, still occurring worldwide at an alarming rate, are widely acknowledged as threats to the integrity and functioning of ecosystems. In addition to introducing disease, biological invasions have also been linked to sudden increases in the incidence or severity of previously existing diseases. We review and illustrate the potential direct and indirect impacts of introduced species on the dynamics of endemic parasites in freshwater ecosystems. 2. Introduced species may trigger and sustain disease emergence by acting as competent hosts for endemic parasites in which infection is amplified and then ‘spilled back’ to native hosts. In contrast, if introduced species are not suitable hosts for endemic parasites but become infected anyway, they may act as sinks for parasites and thus dilute disease risk for native hosts. 3. Another mechanism by which introduced species can influence endemic parasitic diseases is by altering the relative abundance of one of the parasite’s hosts in ways that could either enhance or reduce disease transmission to other native hosts in the parasite’s life cycle. 4. Introduced species may also alter disease incidence and severity in native hosts through trait‐mediated indirect effects. For example, the introduced species could change the exposure or susceptibility of native hosts to infection by causing alterations in their behaviour or immunocompetence. Also, by directly changing physicochemical conditions and modifying environmental stressors introduced species may indirectly affect native host exposure and/or resistance to disease. 5. A survey of parasites infecting introduced freshwater fish in four distinct geographical areas revealed that use of non‐indigenous hosts by endemic parasites is widespread, mostly involving parasites transmitted via the food chain. 6. We conclude by presenting a framework, based on risk assessment, for the prediction and possible mitigation of the impact of introduced species on endemic diseases and by calling for greater recognition of the potential role of invasive species as triggers of endemic disease emergence.