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Haematophagous ectoparasites are worldwide vectors of many zoonotic bacterial diseases, both emerging and re-emerging, whose incidences are rising. Livestock development alters different environmental characteristics such as the microclimate of a site, changing the availability, density and susceptibility of the hosts to pathogens and vectors, indirectly influencing the spread and persistence of a disease within an ecosystem. The Norway rat (Rattus norvegicus), the most abundant vertebrate pest species found on livestock farms from Argentina, is a reservoir for several important zoonotic bacteria and may harbor ectoparasite species, which act as their vectors. Even though the Norway rat is widely known for its role as an ectoparasite host, the ecological characteristics of their ectoparasite communities and the related factors with parasitism on livestock farms have never been described. In the present study, we describe the ectoparasite community in Norway rats from central Argentina livestock farms, while also depicting the influencing factors on both ectoparasite occurrence and abundance. Ectoparasites were collected from rats captured in 20 sites from Buenos Aires province, between the winter of 2016 and the summer of 2018. A total of 1441 ectoparasite individuals were collected from 159 Norway rat individuals [Total ectoparasite prevalence = 69.2%; Mean ectoparasite specimen abundance (± CI) = 9.06 ± 2.32 ectoparasite individuals per rat; Mean ectoparasite specimen intensity (±CI) = 13.10 ± 3.08 ectoparasite individuals per infested rat found]. Ectoparasite assemblage consisted of four cosmopolitan species, recognized for their sanitary relevance: mites (Laelapidae: Laelaps nuttalli and Laelaps echidninus), lice (Polyplacidae: Polyplax spinulosa) and fleas (Pulicidae: Xenopsylla cheopis). We observed higher Norway rat abundance in sites related to higher ectoparasite occurrence and abundance frequencies on the rats. Additionally, ectoparasites were more abundant on rats in warm seasons and on male individuals, over female rats. Moreover, the geographical location of the studied sites influenced the ectoparasite assemblage structure observed on the rats. This study broadens the knowledge on the role of Norway rats as zoonotic ectoparasites hosts and analyzes the drivers influencing ectoparasite occurrence and abundance on the most populated region of Argentina, which is also the region with the most intensive livestock farming. Therefore, this survey may assist in evaluating potential risks for humans and generate effective sanitary control strategies for ectoparasite-borne infectious diseases.

BACKGROUND: Rodent species are common in livestock production systems, and some of them are considered serious pests because of the sanitary problems and economic losses they cause. Information about microhabitat selection by rodent species in livestock production systems is necessary for understanding rodent requirements and to contribute to effective prevention and development of control measures for pest rodent species. In this work we study microhabitat selection by rodent species that inhabit pig and dairy farms in central Argentina. Rodent trapping was conducted over three years (2008–2011) on 18 livestock farms, each one sampled seasonally during one year. To study habitat selection, microhabitat characterizations were performed describing 22 environmental variables in captured sites and random trap sites without captures. RESULTS: With a trapping effort of 7333 Sherman and 7026 cage live trap-nights, 444 rodents of seven species were captured (including the murine pest species Rattus norvegicus, R. rattus and Mus musculus and four native species). The three murines selected characteristics related to building structure and/or to food sources availability/proximity, while Akodon azarae selected sites with tall herbatious vegetation. CONCLUSIONS: We identified microhabitat characteristics that explain habitat distribution of small rodent species in these complex farm systems. This study contributes to broaden the integrated pest management of rodent pest species and could also contribute to the reduction of the use of rodenticides in these systems. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry

Background Understanding the ecological processes that are involved in the transmission of zoonotic pathogens by small mammals may aid adequate and effective management measures. Few attempts have been made to analyze the ecological aspects that influence pathogen infection in small mammals in livestock production systems. We describe the infection of small mammals with Leptospira spp., Brucella spp., Trichinella spp. and Cysticercus fasciolaris and assess the related intrinsic and extrinsic factors in livestock production systems in central Argentina at the small mammal community, population and individual levels. Methodology/Principal findings Ten pig farms and eight dairy farms were studied by removal trapping of small mammals from 2008 to 2011. Each farm was sampled seasonally over the course of one year with cage and Sherman live traps. The 505 small mammals captured (14,359 trap-nights) included three introduced murine rodents, four native rodents and two opossums. Leptospira spp., anti-Brucella spp. antibodies and Trichinella spp. were found in the three murine rodents and both opossums. Rattus norvegicus was also infected with C. fasciolaris; Akodon azarae and Oligoryzomys flavescens with Leptospira spp.; anti-Brucella spp. antibodies were found in A. azarae. Two or more pathogens occurred simultaneously on 89% of the farms, and each pathogen was found on at least 50% of the farms. Pathogen infections increased with host abundance. Infection by Leptospira spp. also increased with precipitation and during warm seasons. The occurrence of anti-Brucella spp. antibodies was higher on dairy farms and during the winter and summer. The host abundances limit values, from which farms are expected to be free of the studied pathogens, are reported. Conclusions/Significance Murine rodents maintain pathogens within farms, whereas other native species are likely dispersing pathogens among farms. Hence, we recommend preventing and controlling murines in farm dwellings and isolating farms from their surroundings to avoid contact with other wild mammals., Author summary Some rodents and opossums can transmit zoonotic diseases, thereby causing economic losses and sanitary problems, including damage to livestock production systems worldwide. Identifying the factors affecting pathogen transmission will contribute to a better understanding of the mechanisms involved. In this study, the infection of four zoonotic pathogens in small mammals captured on intensive pig and dairy farms in central Argentina and potential environmental drivers of those infections were studied. Seven rodent and two opossum species were trapped on these farms. Murine rodents and opossums were infected with Leptospira spp. and Trichinella spp. and carried anti-Brucella spp. antibodies. Rattus norvegicus was also infected with C. fasciolaris, and some native rodents were infected with some of the studied pathogens. Each pathogen occurred on at least 50% of the farms, and two or more pathogens occurred on 89% of the farms. These results reflect a high circulation of zoonotic pathogens relevant to public health on intensive livestock farms. Moreover, all pathogen infections increased with host abundances. Murine rodents maintain pathogens within farms, whereas other native species are likely dispersing pathogens among farms.

Trichinellosis is a zoonotic disease caused by nematodes of the genus Trichinella. Humans, who are the final hosts, acquire the infection by eating raw or undercooked meat of different animal origin. Trichinella spiralis is an encapsulated species that infects mammals and is widely distributed in different continents. In Argentina, this parasite has been reported in the domestic cycle that includes pigs and synanthropic hosts (mainly rats and some carnivores). This is the first report of T. spiralis in the opossums Didelphis albiventris and Lutreolina crassicaudata in Argentina, and the first report in opossums in South America. In this survey, Trichinella larvae were detected by enzymatic digestion in three D. albiventris and one L. crassicaudata captured on pig and dairy farms located in the northeast of Buenos Aires province. The microscopic examination of the 32 larvae isolated presented the diagnostic characteristic of the genus Trichinella. Two larvae isolated from two D. albiventris and one from L. crassicaudata were identified as T. spiralis by nested multiplex PCR and confirmed by sequencing. Further research to determine the burdens of T. spiralis in opossums may contribute to a better understanding of the risk of T. spiralis transmission to the synanthropic populations. Instituto de Patobiología Fil: Castaño Zubieta, Mirta Raquel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patobiología; Argentina Fil: Ruiz, M.. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patobiología; Argentina Fil: Morici, Gabriel Edgardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patobiología; Argentina Fil: Lovera, Rosario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Fernández, María Soledad. Ministerio de Salud. Centro Nacional de Diagnóstico e Investigación en Endemo-Epidemias ANLIS; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina Fil: Caracostantogolo, Jorge Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patobiología; Argentina Fil: Cavia, Regino. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina

En un estudio exploratorio de roedores de la especie Rattus norvegicus de la provincia de Buenos Aires, se observó que ciertos metacestodos de tenias se encontraban enquis- tados en el hígado del hospedador. Nuestro objetivo fue identificar esta forma larval, basándonos en estudios morfológicos y moleculares. Para la caracterización molecular del parásito, se amplificó y secuenció el ADN ribosomal (28S) y mitocondrial (COI). Sobre la base de los datos tanto morfológicos como moleculares, y utilizando herramientas bio- informáticas, el metacestodo se identificó como Cysticercus fasciolaris. La forma adulta (Taenia taeniaeformis) comúnmente infecta hospedadores mamíferos félidos y cánidos. Esta es la primera vez que se caracteriza molecularmente este helminto, aislado de roe- dores de la provincia de Buenos Aires. Fil: Martinez, Mara Leila. Instituto Nacional de Tecnologia Agropecuaria. Centro Nacional de Inv. Agropecuarias. Centro de Invest.de Cs.veterinarias y Agronomicas. Instituto de Patobiologia; Argentina; Fil: Dominguez, Mariana Gabriela. Instituto Nacional de Tecnologia Agropecuaria. Centro Nacional de Inv. Agropecuarias. Centro de Invest.de Cs.veterinarias y Agronomicas. Instituto de Patobiologia; Argentina; Fil: Morici, Gabriel E.. Instituto Nacional de Tecnologia Agropecuaria. Centro Nacional de Inv. Agropecuarias. Centro de Invest.de Cs.veterinarias y Agronomicas. Instituto de Patobiologia; Argentina; Fil: Cavia, Regino. Consejo Nacional de Invest. Científ.y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Bs. As; Argentina; Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; Argentina; Fil: Montes de Oca, Daniela Paula. INSTITUTO DE ECOLOGIA, GENETICA Y EVOLUCION DE BS. AS; ecologia; Fil: Lovera, Rosario. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; Argentina; Consejo Nacional de Invest. Científ.y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Bs. As; Argentina; Fil: Schapiro, Javier Hernan. Instituto Nacional de Tecnologia Agropecuaria. Centro Nacional de Inv. Agropecuarias. Centro de Invest.de Cs.veterinarias y Agronomicas. Instituto de Patobiologia; Argentina; Fil: Caracostantogolo, Jorge Luis. Consejo Nacional de Invest.cientif.y Tecnicas. Ultraestructura, Microanalisis y Espectroscopia; Arggentina