The rapid and extensive anthropogenic alterations of ecosystems are having deep effects on the distribution and ecology of organisms, including parasites.1 Particularly big cities constitute obvious melting pots for the mixing of human and animal parasites and their potential for rapid spread, both locally and internationally.2 This situation is even more pronounced when human and other animal species live in close contact due to structural and/or environmental conditions. In this way, Argentina is characterized by remarkable social and economic fragmentation, which has deepened during the 90′s.3 Therefore, most of the big cities in Latin America are nowadays characterized by the presence of peripheral neighborhoods that present structural and environmental features that favor the presence of synanthropic species, which can act as source of zoonotic diseases.4 Clear examples of synanthropic species are the urban rodents, represented by the Norway rat (Rattus norvegicus Berkenhput, 1769) and the black rat (Rattus rattus Linnaeus, 1758), originally from Southeast Asia and North Africa/West Asia respectively, among others.5,6 A large number of pathogens and parasite species utilize urban rodents to fulfill part of their life cycle.7 One of the most important zoonotic pathogens related to rodents, due to sanitary implications, are the RNA virus Hantavirus, which belong to the Hantaviridae family, genus Orthohantaviridae.8 Hantaviruses are negative-sense, single-stranded RNA viruses with a small (< 11 kb) tripartite genome.9 These viruses are cause of Hemorrhagic Fever with Renal Syndrome (HFRS) in Europe and Asia, and Hantavirus Cardio Pulmonary Syndrome (HCPS) in America.1

Hantaviruses, unlike all other viruses in the family, are not transmitted by arthropod vectors. Most frequently, transmission is through inhalation of virus-contaminated aerosols of rodent excreta. Urban rodents (mainly genus Rattus) are reservoirs of Seoul virus (SEOV).10 This species causes a moderate form of HFRS in urban populations. The infection in rodents is asymptomatic and persistent.11 Although in America there are few records of human cases, in Argentina positive cases of SEOV in R. norvegicus have been reported since the 1980s.11,12 Moreover, in recent years, serological and molecular evidence of SEOV circulation have been recorded in rodents from the Autonomous City of Buenos Aires.13 So far, no human cases of HFRS due to SEOV have been recorded.12 However, Approximately 150,000 to 200,000 cases of HFRS involving hospitalization are reported each year throughout the world.14 In this context, the aim of this study was to identify the presence of Hantavirus in urban rodents from peripheral neighborhoods of Gran La Plata, Argentina.

The area of Gran La Plata includes the capital city of Buenos Aires province. It is located in the northeast of the province of Buenos Aires, Argentina. Sampling was carried out seasonally in seven neighborhoods: Malvinas Argentinas (34.5643°S, 58.0036°W), La Isla (34.5328°S, 57.5925°W), El Retiro (34.5751°S, 58.0017°W), La Latita (34.5831°S, 57.5830°W), Abasto (34.5805°S, 58.0147°W) and El Carmen (34.5533°S, 57.5309°W); Casco Urbano (34.5516°S, 57.5716°W; Fig. 1). These neighborhoods present different levels of urbanization. Most of them are characterized by poor environmental and structural features like inadequate garbage removal, lack of a sanitation network and potable water, with areas susceptible to flooding and with domestic animals without sufficient care. Only Casco Urbano, as part of La Plata city center, presents all services. Rodents were captured using cage live traps (15 × 16 × 31 cm), Sherman traps (8 × 9 × 23 cm) and snap traps (17.5 × 8.5 cm) and then euthanized. After necropsy, blood samples were extracted using the cardiac puncture technique, and stored at −70 °C. The presence of anti-hantavirus IgG antibodies was determined by the Enzyme-Linked Immunosorbent Assay (ELISA), following Calderon et al. 201815 using gamma irradiated Seoul virus antigens (lysate of infected Vero E6 cells). Each sample was processed in parallel with uninfected control antigen. Sera with OD greater than or equal to 0.2, and a titer greater than or equal to 1:400 were considered positive. Specimens were sacrificed following procedures and protocols approved by national laws (Animal Protection National law 14.346 and references in the provincial permits) and the Laboratory, Farm and Wildlife Animals Research Ethics Committee of the National Council of Scientific and Technical Research (CONICET).

Fig. 1.

Map of the neighborhoods of Gran La Plata, Buenos Aires, Argentina. A, Abasto; CU, Casco Urbano; EC, El Carmen; ER, El Retiro; LI, La Isla; LL, La Latita; MA, Malvinas Argentinas.

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For this survey, a total of 42 rodents were captured and analyzed, 25 R. norvegicus and to 17 R. rattus. Six samples resulted positive to SEOV (overall prevalence of 14.3%): five R. norvegicus, representing a prevalence of 20%; and one R. rattus, representing a prevalence of 5.88%. Concerning R. norvegicus, three positive samples were detected in El Retiro neighborhood, one in La Isla, and one in El Carmen. The R. rattus positive sample was recorded in La Isla neighborhood.

These findings correspond to the first records of SEOV in urban rodents in Gran La Plata area and represents the first record of this virus in R. rattus in Argentina, and in the American continent. Concerning R. norvegicus, the prevalence rates here recorded are intermediate compared to previous surveys carried out in other areas of Argentina, which ranged from 11%12,16 and 31%.11 Despite studies that have been carried out, there are no reports of R. rattus in Argentina and in other countries of America;12 in contrast, in Europe and Asia many cases have been reported.17,18

Although no cases of HFRS have not been recorded in humans in Argentina, cases were reported in other countries of America, for example in United States19 and Brazil.20 The record of transmission in other countries of the region and the close contact in which people coexist with urban rodents in neighborhoods favors the establishment and transmission of human infection. Particularly for this scenario, rodents were captured inside households (for example under the beds or into the kitchens), and in the backyards, which in all cases consist in very small surfaces with a mixture of grass and garbage. In any case the number of people living in these households was not less than three, allowing close everyday contact and representing a potential sanitary risk, becoming necessary for the government to incorporate in the agenda actions towards providing better living conditions for people, including rat control programs. Moreover, as other diseases caused by parasitic organisms, the risk represented by SEOV in these regions are examples of inequality and the historical forgetfulness of a portion of society, calling for urgent actions to be take in that regard.