Seroprevalence of leptospiral antibodies in rodents from riverside communities of Santa Fe, Argentina.

BACKGROUND: Leptospirosis is a zoonotic disease that can be transmitted by contact with the urine of infected mammals. Rodents play a mayor role in the transmission of leptospires to humans. The province of Santa Fe reports the greatest number of cases in Argentina. Yet, in this region, there are still knowledge gaps regarding the diversity of rodent species that may be hosts of pathogenic leptospires. The aims of this study were to evaluate the presence of leptospiral antibodies in rodents from three riverside communities of Santa Fe, and to identify factors associated with leptospiral infection. METHODOLOGY/PRINCIPAL FINDINGS: Each community was divided into three environmental settings based on the level of human disturbance, and sampled during two springs (Sep-Oct 2014 and 2015) and one autumn (Mar-Apr 2015). Serum samples of captured sigmodontine and murine rodents were tested for leptospiral antibodies by enzyme-linked immunosorbent assay (ELISA), and microagglutination test (MAT) was used to assess the infecting serovar in seropositive individuals. Factors influencing seropositivity were analyzed using logistic regression models. We caught 119 rodents, of which 101 serums were suitable for analysis. Most frequently trapped species were Scapteromys aquaticus, Akodon azarae and Oligoryzomys spp., with seroprevalences of 41.3%, 42.9% and 55% respectively. Seropositivity was higher in individuals with an average body condition score and in those that were sexually mature, but in the latter the differences were marginally significant. CONCLUSIONS/SIGNIFICANCE: Our results suggest that native rodents may be playing a role in the environmental circulation of pathogenic leptospires and provide relevant information for public health policies in the area.

Detection of New World Hantavirus Antibodies in Rodents of Eastern New Mexico, USA.

Hantaviruses, causal agents of the potentially lethal hantavirus pulmonary syndrome, have widely distributed rodent hosts. Using an enzyme-linked immunosorbent assay, we tested blood from 398 wild rodents captured in eastern New Mexico, US in 2015-17 and found 42 antibody-positive samples representing six genera.

Trypanosoma cruzi load in synanthropic rodents from rural areas in Chile.

BACKGROUND: Trypanosoma cruzi is the agent of Chagas disease, a major public health problem in Latin America. Many wild and domestic animals are naturally infected with T. cruzi; rodents are one of the groups which have been consistently detected infected in different countries. The aim of this work was to characterize blood T. cruzi load in naturally infected rodents from a Chagas disease endemic region in Chile. METHODS: Baited traps were set in domestic and peridomestic areas of rural dwellings. The rodents were anesthetized and blood sampled; DNA was extracted and the parasite load was quantified by T. cruzi satellite DNA real-time PCR assays. RESULTS: Seventy-one rodents of four species, Rattus rattus, Mus musculus, Phyllotis darwini and Octodon degus, were captured; R. rattus was the most abundant species. Fifty-nine samples (83.1%) were T. cruzi-positive and the median value of the parasite load was 2.99 parasite equivalents (par-eq)/ml. The comparison of frequency of infection or parasite load by species showed no differences. However, one R. rattus presented very elevated parasitemia (1644 par-eq/ml). CONCLUSIONS: The overall levels of parasitemia were similar to those found in humans in Chile. The high infection levels in exotic and endemic rodents very near to rural settlements increases their relevance as T. cruzi hosts.

Rodent Abundance and Hantavirus Infection in Protected Area, East-Central Argentina.

We captured 3 hantavirus rodent hosts in Otamendi Natural Reserve, Argentina, during 2007-2012. Hantavirus antibodies were found only in Akodon azarae grass mice, mainly in males and old animals. Higher abundance of this species was associated with warm and rainy weather and high water levels, which peaked after a strong El Niño event.

Occurrence of anti-Leptospira spp. antibodies in Rhipidomys spp. from a forest fragment of the Brazilian Cerrado.

Leptospirosis is a zoonotic disease of world importance, and its transmission depends on the interaction between humans and animals. Given the necessity to investigate potential hosts of Leptospira spp., this study verified the prevalence of different serovars in the species of Rhipidomys spp., a widespread sigmodont rodent in Brazil. The studied population originates from a semi-evergreen forest located in the county of Uberlândia, in the state of Minas Gerais. The microscopic agglutination test (MAT) was performed with 14 serovars. Thirteen out of the 43 wild rodents captured showed a positive agglutination reaction, with a greater prevalence of the serovars Pyrogenes, Copenhageni, and Canicola. This study found a prevalence of 30.3% anti-Leptospira spp. antibodies; all positive animals were reactive to more than one serovar.

Serology, isolation, and molecular detection of Leptospira spp. from the tissues and blood of rats captured in a wild animal preservation centre in Brazil.

To elucidate the occurrence and epidemiology of leptospirosis in rats cohabitating with forest animals, 13 rats were captured at seven locations of the Centre for the Conservation of Wild Fauna (CCWF) in Sao Paulo state, Brazil, and samples of their blood, liver, and kidneys were collected. The diagnostic techniques utilized were the microscopic agglutination test (MAT), polymerase chain reaction (PCR) for Leptospira spp., and cultures of rat kidneys and liver in Fletcher's medium. The MAT results showed that 13 (100%) of the samples were reactive to 12 serovars among the 29 Leptospira spp. tested, and the Australis and Tarassovi serovars were the most frequently identified serovars. To research the agent in fragments of the liver and kidney, 13 samples from each tissue were cultured in Fletcher's medium, and the results revealed seven positive samples (53.8%; three from the kidneys and four from the livers). The analysis of the blood samples by PCR for Leptospira spp. showed that six animals (46.1%) were positive, whereas the analysis of the organs (kidneys and liver) by PCR revealed that nine animals (69.2%) were positive, and the culture of the organs revealed four positive animals (30.8%). These results suggest that the presence of Leptospira spp. infection in rats at the study site and the knowledge of the serovars that exist in this environment are important for the epidemiological comprehension of the disease and for the identification of control measures that should be considered to reduce the risk of transmission of the disease through this animal reservoir.

Occurrence of Toxoplasma gondii antibodies in Dasyprocta aguti from Brazil: comparison of diagnostic techniques.

In this study, the occurrence of antibodies to Toxoplasma gondii in Brazilian agouti (Dasyprocta aguti) was compared by modified agglutination test (MAT) and indirect fluorescent antibody test (IFAT) using anti-capybara conjugate. Sera from 109 animals were tested using MAT (1:25 cut-off) and IFAT (1:16 cut-off); 19% were positive by MAT, and 18% were positive by IFAT. Overall, the 17 IFAT-positive samples were also positive for MAT. The four positive MAT samples with a titer < or = 200 were IFAT negative. All negative samples obtained by MAT matched with the results of the IFAT. Comparing both tests, and considering MAT as the gold standard, the sensitivity of IFAT was 81%, the specificity was 100%, the accuracy was 97%, the positive predictive value (PPV) was 100%, and the negative predictive value 96%. The kappa value agreement was 87.3% (75.1-99.6%). The anti-capybara conjugate can be successfully used to perform IFAT in Brazilian agouti with maximum specificity and PPV.

Molecular detection of Leishmania braziliensis in Rattus norvegicus in an area endemic for cutaneous leishmaniasis in Brazil.

Leishmania nested PCR (LnPCR) targeted to the SSUrRNA gene and DNA sequencing were used to analyze 315 tissue samples from 80 Rattus norvegicus specimens trapped in an area endemic for leishmaniasis in Belo Horizonte, Minas Gerais, Brazil. Of the samples analyzed, 17.46% (55/315) of all tissues, 10% (8/80) of skin, 26.92% (21/78) of blood, 30.76% (24/78) of bone marrow and 2.53% (2/79) of spleen were positive for Leishmania. The overall infection prevalence was 36.25% (29/80) The DNA sequencing showed that 65.51% (19/29) of the positive animals were infected by parasites belonging to the Leishmania braziliensis complex. The identification of L. braziliensis DNA in R. norvegicus in an area with a high prevalence of leishmaniasis might imply a zoonotic role of this species. The rodent control programs and health education may represent important measures toward the control of leishmaniasis.

Relationship between splenic sequestration and thrombocytopenia in Trypanosoma evansi infection in rats.

Trypanosoma evansi infections in domestic animals are characterized by anemia and thrombocytopenia. The cause of the platelets decrease is unknown, but researchers suggest that thrombocytopenia may result from damage of the bone marrow, reduced survival of platelets, auto-immune thrombocytopenia, disseminated intravascular coagulation and splenic sequestration. Some of these causes have already been tested by our research group and found to be unrelated. Therefore, this study has the objective of testing the hypothesis that splenic sequestration might be responsible for thrombocytopenia in T. evansi-infected rats. A total of 28 rats assigned to four groups were used in the experiment. Group A rats were splenectomized and infected with T. evansi, group B rats were infected with T. evansi, group C rats were splenectomized, but not infected and group D rats were normal controls. Five days post-infection all rats were anesthetized and blood was collected in order to measure the number of circulating platelets, fibrinogen levels, prothrombin time (PT) and activated partial thromboplastin time (aPTT). The spleens of groups B and D were weighed at necropsy. The infected animals (groups A and B) showed a significant reduction in platelets and increased PT and aPTT when compared to negative control groups (groups C and D). Animals from group A showed increased levels of fibrinogen. The mean weight of spleen differed between group B (2.62g) and group D (0.55g). It was concluded that there is no relationship between thrombocytopenia and splenic sequestration in infection by T. evansi.

Evidencia serológica de circulación de Leptospira spp en Rattus norvegicus naturalmente expuestos en una zona urbana colombiana / Serological evidence of Leptospira spp circulation in naturally-exposed rats (Rattusnorvegicus) in a Colombian urban area

Objetivo Determinar la frecuencia de anticuerpos dirigidos contra especies de Leptospira patógenas en reservorios naturales, con el propósito de establecer evidencia de su papel potencial en la dispersión ambiental de Leptospira y por consiguiente su actuación como agente diseminador de la infección tanto al humano como a otras especies susceptibles. Materiales y métodos El muestreo se llevó a cabo en la Plaza Minorista durante el periodo comprendido entre agosto de 2006 y abril de 2007, en el cual se capturaron 254 roedores Rattus norvegicus. Se obtuvo sangre de estos por punción cardiaca y el suero resultante se procesó con la prueba de Microaglutinación. Resultados El análisis serológico para verificar las serovariedades circulantes de Leptospira spp, dio como resultado que 64 roedores (25,2 por ciento, 95 por ciento CI=19,5-30,1) tuvieron títulos positivos para al menos una de las 11 serovariedades probadas. Conclusiones Los datos muestran que no solo la serovariedad Icterohaemorrhagiae está asociada con esta especie reservoria; también lo están otras serovariedades como Grippothyphosa y Canícola. El estudio permitió determinar la frecuencia de anticuerpos contra especies patógenas de Leptospira para reservorios procedentes de una zona urbana colombiana. Estos datos son relevantes para las entidades de salud pública por constituir la base para la implementación de campañas de control adecuadas para esta zona del país y como modelo de otros estudios similares en otras ciudades colombianas.

Objective Assessing the frequency of antibodies directed against pathogenic Leptospira species found in natural reservoirs for establishing evidence of their potential role in the environmental dispersion of Leptospira and consequent dissemination of the infection to humans as well as to other susceptible species. Material and methods A survey was carried out in the Plaza Minorista from August 2006 to April 2007 in which 254 rats (Rattusnorvegicus) were captured. Blood was obtained from these rodents by cardiac puncture and the resulting serum was used for microagglutination tests. Results Serological analysis for verifying Leptospira spp circulating serovars resulted in 64 rodents (25.2 percent;19.5-30.1 95 percentCI) having positive antibody titres for at least 11 of the serovars tested. Conclusions Frequency data regarding the antibodies so detected showed that the Icterohaemorrhagiae serovar was not the only one possibly associated with this reservoir species, but also with others such as the Grippothyphosa and Canícolaserovars. The study determined the frequency of antibodies against pathogenic Leptospira species for reservoirs from an urban area in Colombia. This data is relevant for public health authorities and might constitute the basis for implementing appropriate control campaigns for this area of the country and, likewise, this work could serve as a model for similar studies in other Colombian cities.

[Serological evidence of Leptospira spp circulation in naturally-exposed rats (Rattusnorvegicus) in a Colombian urban area]. / Evidencia serológica de circulación de Leptospira spp en Rattus norvegicus naturalmente expuestos en una zona urbana colombiana.

OBJECTIVE: Assessing the frequency of antibodies directed against pathogenic Leptospira species found in natural reservoirs for establishing evidence of their potential role in the environmental dispersion of Leptospira and consequent dissemination of the infection to humans as well as to other susceptible species. MATERIAL AND METHODS: A survey was carried out in the Plaza Minorista from August 2006 to April 2007 in which 254 rats (Rattusnorvegicus) were captured. Blood was obtained from these rodents by cardiac puncture and the resulting serum was used for microagglutination tests. RESULTS: Serological analysis for verifying Leptospira spp circulating serovars resulted in 64 rodents (25.2 %;19.5-30.1 95 %CI) having positive antibody titres for at least 11 of the serovars tested. CONCLUSIONS: Frequency data regarding the antibodies so detected showed that the Icterohaemorrhagiae serovar was not the only one possibly associated with this reservoir species, but also with others such as the Grippothyphosa and Canícolaserovars. The study determined the frequency of antibodies against pathogenic Leptospira species for reservoirs from an urban area in Colombia. This data is relevant for public health authorities and might constitute the basis for implementing appropriate control campaigns for this area of the country and, likewise, this work could serve as a model for similar studies in other Colombian cities.

Survey for antibody to hantaviruses in Tamaulipas, Mexico.

Wild rodents (n=248) were trapped in two ecologically distinct sites at El Cielo Biosphere Reserve in the state of Tamaulipas, Mexico, during the summer of 2003. Samples from 199 individuals were tested for Hantavirus antibodies by an indirect enzyme-linked immunosorbent assay (ELISA). Hantavirus antibodies to recombinant Sin Nombre virus nucleocapsid protein were found in seven rodents (3.5%) of a single species, Peromyscus levipes. Antibody-positive rodents were found only in the Cloud Forest site, which had lower rodent species diversity than the Tropical Subdecidous Forest site. Although the identity of the virus in P. levipes remains to be determined, our study provides further evidence that Hantavirus antibody-positive individuals are prevalent in the rodent fauna of Mexico. This is the first survey for Hantavirus antibodies in the rodent fauna of Tamaulipas and the first report of P. levipes as a potential host for a Hantavirus.

Hantavirus antibodies in rodents and human cases with pulmonary syndrome, Rio Negro, Argentina.

In Río Negro Province, Argentina, human cases of hantavirus pulmonary syndrome (HPS) appeared in the region of subantarctic forests. The Andes virus (ANDV) has been identified in the region both in Oligoryzomys longicaudatus rodents and in humans, with the main transmission being from rodents to humans but also showing the possibility of human to human transmission. Between 1996 and 2004, in 40 campaigns, 29.960 night-traps for capturing live rodents were set up. Blood samples were obtained from the rodents and processed using enzyme immunoassay with recombinant antigens made from ANDV. A total of 1767 rodents were captured, with a capture success of 5.9% and an antibody prevalence of 2.1%. Important differences were observed among the species captured from Andes and Steppe regions. Seropositive Oligoryzomys longicaudatus, Abrotrix olivaceus, Abrotrix xanhtothinus and Loxodontomus microtus were captured. During the 1993-2004 period, 40 HPS cases were registered.

Hantavirus antibodies in rodents and human cases with pulmonary syndrome, Río Negro, Argentina / Anticuerpos contra hantavirus en roedores y casos humanos con síndrome pulmonar, Río Negro, Argentina

In Río Negro Province, Argentina, human cases of hantavirus pulmonary syndrome (HPS) appeared in the region of subantartic forests. The Andes virus (ANDV) has been identified in the region both in Oligoryzomys longicaudatus rodents and in humans, with the main transmission being from rodents to humans but also showing the possibility of human to human transmission. Between 1996 and 2004, in 40 campaigns, 29.960 night-traps for capturing live rodents were set up. Blood samples were obtained from the rodents and processed using enzyme immunoassay with recombinant antigens made from ANDV. A total of 1767 rodents were captured, with a capture success of 5.9% and an antibody prevalence of 2.1%. Important differences were observed among the species captured from Andes and Steppe regions. Seropositive Oligoryzomys longicaudatus, Abrotrix olivaceus, Abrotrix xanhtothinus and Loxodontomus microtus were captured. During the 1993-2004 period, 40 HPS cases were registered.

En la Provincia de Río Negro, Argentina, se presentaron casos humanos de síndrome pulmonar por hantavirus (SPH) en la región de los bosques subantárticos. El virus Andes (AND) fue identificado en la región, tanto en el roedor Oligoryzomys longicaudatus como en seres humanos, demostrándose la transmisión principalmente del roedor al hombre y la posibilidad de la transmisión de persona a persona. Para ello, se procedió a la colocación de 29.960 trampas para captura viva de roedores, tipo Sherman, en 40 operativos efectuados desde 1996 hasta 2004. Se obtuvieron muestras de sangre de los roedores, las que fueron procesadas mediante enzimoinmunoensayo con antígenos recombinantes elaborados a partir de virus AND. Fueron capturados 1767 roedores, con un éxito de trampeo del 5.9% y una prevalencia de anticuerpos contra hantavirus del 2.1%. Se observaron importantes diferencias en las especies capturadas en cada una de las regiones. Se capturaron O. longicaudatus, Abrothrix olivaceus y Abrothrix xanhtothinus y Loxodontomys microtus seropositivos. Se registraron 40 casos humanos en el período 1993-2004.

Trypanosoma cruzi detection in blood by xenodiagnosis and polymerase chain reaction in the wild rodent Octodon degus.

We detected Trypanosoma cruzi in blood samples of the wild rodent Octodon degus by xenodiagnosis and a polymerase chain reaction (PCR) using the domestic and wild vectors of Chagas disease, Triatoma infestans and Mepraia spinolai, respectively. We captured 35 rodents and extracted DNA from blood samples and intestinal contents of vectors fed on O. degus. Our results indicate that the percentage of rodents naturally infected with T. cruzi depends on the biologic sample used for PCR and on the vector species for xenodiagnosis. The PCR with blood samples did not detect T. cruzi DNA, but the PCR with intestinal contents showed that both vectors were positive for T. cruzi. The PCR performed with M. spinolai intestinal contents detected four times more T. cruzi-positive O. degus than the PCR with Triatoma infestans intestinal contents (22.9% and 5.7%, respectively). We report the improvement of T. cruzi detection in sylvatic animals by a combination of PCR and xenodiagnosis using sylvatic vectors, especially in disease-endemic areas with low parasitemias in mammals.

PCR-based diagnosis for detection of Leishmania in skin and blood of rodents from an endemic area of cutaneous and visceral leishmaniasis in Brazil.

The technique of polymerase chain reaction (PCR) associated to hybridization was used to screen 123 samples collected from wild and synanthropic rodents captured in a cutaneous and visceral leishmaniasis endemic area in the State of Minas Gerais, Brazil. The detection of Leishmania spp in naturally infected rodents is of fundamental importance for incriminating them as possible reservoir hosts of the diseases in Minas Gerais. A total of 62 specimens belonging to wild (Thrichomys apereoides, Oryzomys subflavus, Galea spixii, Bolomys lasiurus and Wiedomys pyrrhorhinos) and synanthropic (R. rattus) rodent species were captured in different ecotopes. Blood and skin samples were submitted for PCR analyses followed by molecular hybridization with specific probes for the three Leishmania-species complexes. Fifteen samples were found positive after PCR-hybridization and identified as follows: nine belonging to the L. mexicana complex, three to the L. braziliensis complex and three to the L. donovani complex. Positive PCR results were found in 11 out of the 61 (18%) blood samples and in four out of the 62 (6.4%) skin fragments screened. R. rattus and T. apereoides were the most abundant species in the area also presenting high prevalence of natural infection. The presence of parasite DNA belonging to L. braziliensis, L. mexicana and L. donovani complexes was confirmed in several individuals of a rodent species, R. rattus. This work is the first report of the detection of L. (L.) chagasi in a naturally infected T. apereoides. The utility of filter paper as a substrate for PCR analyses and the efficacy of the procedure associated to the hybridization is emphasized.

[Development of an antigen for the diagnosis of Kilham rat parvovirus by hemagglutination inhibition test]. / Desarrollo de un antígeno para diagnóstico del parvovirus de las ratas (virus Kilham) por la técnica de inhibición de la hemaglutinación.

An antigen of rat parvovirus (Kilham virus) was developed for the diagnosis of viral infection in rat colonies by using hemagglutination inhibition (HAI) test. Primary cell cultures from rat embryos were infected with Kilham rat virus. Infected cells obtained at different time post infection were scraped, centrifuged, concentrated one hundred times, sonicated and centrifuged again. The supernatants obtained were titrated by hemagglutination. The specificity was confirmed with positive and negative reference sera. Ninety eight serum samples were studied by using HAI test. The results coincided with those obtained in a reference laboratory. Kilham rat parvovirus antigen obtained from 5 days-infected-cells was specific, sensitive, easy to prepare, with a high yield and it is useful to detect this virus in experimental and production rat colonies.

Associations between leptospiral infection and seropositivity in rodents and environmental characteristics in Argentina.

Our objective was to look for associations between leptospiral infection in rodents and selected environmental and rodent characteristics in Santa Fe, Argentina. Rodents (n = 214) were trapped alive from January 1998 to December 1999 in three environmental settings. Kidneys from 118 rodents were cultured and serum samples from 201 were processed by enzyme-linked immunosorbent assay (ELISA). Logistic regression was performed with ELISA seropositivity as the dependent variable and rodent characteristics were offered as independent variables. Overall prevalence of positive ELISA reactions was 42% (84/201). In urban areas, leptospiral isolations belonged to the Ballum serogroup; in natural corridors, they belonged to the Icterohaemorragiae serogroup. M. musculus (house mouse) was the most-frequently captured species and the predominant one in urban areas. Most isolates and seropositivity results were obtained on this species. Adults and subadults had higher seroprevalences than juvenile rodents. Oligoryzomys flavescens had higher seroprevalence than Akodon azarae, Mus musculus, Rattus rattus and Rattus norvegicus.

Coinfection of laboratory rats with Mycoplasma pulmonis and Chlamydia pneumoniae.

Routine examinations of conventional outbred Wistar rats in our laboratory showed increased serum levels of alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, and urea. Electron microscopy and specific reactions showed C. pneumoniae and M. pulmonis in lung, liver, spleen, heart, and kidney sections. We could not exclude the fact that other infectious microorganisms detected through routine health surveillance affected the Wistar rat colony; however, we have not identified any of those microorganisms by electron microscopy of the organs listed. Natural coinfection of C. pneumoniae and M. pulmonis can occur in laboratory rats and is associated with histopathological and functional compromise of many organs. Further studies comparing different conventional animals and specific pathogen-free animals are necessary to better understand the present findings and to define whether coinfection influences the results of experimental studies with rats.