Paulo S. D'Andrea

Effects of habitat fragmentation on wild mammal infection by Trypanosoma cruzi

Expansion of human activities frequently results in habitat fragmentation, a phenomenon that has been widely recognized in the last decades as one of the major threats to worlds biodiversity. The transformation of a continuous forest into a fragmented area results in a hyper-dynamic landscape with unpredictable consequences to overall ecosystem health. The effect of the fragmentation process on Trypanosoma cruzi infection among small wild mammals was studied in an Atlantic Rain Forest landscape. Comparing continous forest to fragmented habitat, marsupials were less abundant than rodents in the continuous landscape. An overall decrease in small wild mammal richness was observed in the smaller fragments. An anti-T. cruzi seroprevalence of 18% (82/440) was deteced by immunofluorescence assay. Moreover, this seroprevalence was higher in the fragmented habitat than in the continuous forest. According to the collected data, 3 main factors seem to modulate infection by T. cruzi in small wild mammals: (i) habitat fragmentation; (ii) biodiversity loss; (iii) increase of marsupial abundance in mammal communities. Furthermore, an extremely mild controlled infection by T. cruzi was detected since no patent parasitaemia could be detected in fresh blood samples, and no parasites were isolated by haemoculture.

The parasitism of Schistosoma mansoni (Digenea–Trematoda) in a naturally infected population of water rats, Nectomys squamipes (Rodentia–Sigmodontinae) in Brazil

Schistosomiasis is a health problem in Brazil and the role of rodents in maintaining the schistosome life-cycle requires further clarification. The influence of Schistosoma mansoni on a population of Nectomys squamipes was studied by capture-recapture (1st phase, from June 1991 to November 1995) and removal (2nd phase, from April 1997 to March 1999) studies at Sumidouro, Rio de Janeiro, Brazil. During both phases coproscopic examinations were performed. At the 2nd phase the rodents were perfused and worms were counted. The population dynamics of parasites was studied. During the 1st phase, female reproductive parameters, longevity, recruitment and survivorship rates and migration patterns were studied in relation to schistosome prevalence. Water contamination (source of miracidia), abundance intermediate host and rodent migration were related to prevalence. The N. squamipes population was not obviously influenced by the infection, as shown by the high number of reproductive infected females, high longevity of infected individuals and the absence of a relationship between recruitment or survivorship rates and the intensity of schistosome infection. The data indicate that N. squamipes can increase transmission of S. mansoni in endemic areas and carry it to non-infected areas. Furthermore, this rodent can be used as an indicator of a transmission focus.

Ecology of small mammals in a Brazilian rural area

A small mammal study was carried out in Pamparrao valley, Sumidouro, State of Rio de Janeiro, Brazil, from June 1991 to July 1996. The area was characterised by small rural properties with vegetable plantations, pasture lands and small forest fragments. Small mammals were captured in seven line transects along the valley. Eleven small mammal species were captured: the didelphid marsupials Didelphis aurita, Philander frenata and Monodelphis americana, and the rodents Nectomys squamipes, Akodon cursor, Oligoryzomys nigripes, Bolomys lasiurus, Oecomys concolor (Sigmodontinae), Rattus ratlus (Murinae), Proechimys iheringi and Euryzygo-matomys guiara (Echimyidae). The heterogeneous habitat configuration probably allowed the occurrence of marsupials and more rodent species when compared to studies in monoculture areas.

The chromosomes of Nectomys (Rodentia, Cricetidae) with 2n = 52, 2n = 56, and interspecific hybrids (2n = 54)

Karyologic comparisons of Nectomys with 2n = 52 and 2n = 56, captured in different regions of Brazil, revealed the existence of two presumptive tandem fusions. These differences proved to represent drastic reproductive barriers between these two karyologic groups, based on an analysis of spermatogenesis in captive-bred hybrids (2n = 54). In these hybrid specimens, cytologic and histologic analyses indicated severe meiotic arrest and the presence of two trivalents in the first meiotic division, in which 26 elements were frequently observed. These findings and the sterility of crosses between F1 males and females as well as backcrosses indicated that Nectomys populations with 2n = 52 and 2n = 56 should be considered different species and that the present taxonomic arrangement of this genus must be reviewed.

Hantavirus Reservoirs: Current Status with an Emphasis on Data from Brazil

Since the recognition of hantavirus as the agent responsible for haemorrhagic fever in Eurasia in the 1970s and, 20 years later, the descovery of hantavirus pulmonary syndrome in the Americas, the genus Hantavirus has been continually described throughout the World in a variety of wild animals. The diversity of wild animals infected with hantaviruses has only recently come into focus as a result of expanded wildlife studies. The known reservoirs are more than 80, belonging to 51 species of rodents, 7 bats (order Chiroptera) and 20 shrews and moles (order Soricomorpha). More than 80genetically related viruses have been classified within Hantavirus genus; 25 recognized as human pathogens responsible for a large spectrum of diseases in the Old and New World. In Brazil, where the diversity of mammals and especially rodents is considered one of the largest in the world, 9 hantavirus genotypes have been identified in 12 rodent species belonging to the genus Akodon, Calomys, Holochilus, Oligoryzomys, Oxymycterus, Necromys and Rattus. Considering the increasing number of animals that have been implicated as reservoirs of different hantaviruses, the understanding of this diversity is important for evaluating the risk of distinct hantavirus species as human pathogens.

Investigation of Chagas disease in four periurban areas in northeastern Brazil: epidemiologic survey in man, vectors, non-human hosts and reservoirs

Chagas disease was investigated in four periurban areas of Ceará state, northeastern Brazil, through serological, parasitological and molecular methods in humans, reservoirs and vectors. A cross-sectional survey revealed a seroprevalence rate of 1.2% (13/1076 residents, six also proving positive through PCR). Trypanosoma cruzi infection was not detected in children under 10 years old. Triatoma pseudomaculata prevailed in the peridomiciles: 63 specimens, 69% (34/49) infected with trypanosomatids. Rhodnius nasutus was captured in Copernicia prunifera palm trees (n=280; 25.0% infected with trypanosomatids) and inside dwellings (n=8, all uninfected). Trypanosoma cruzi seropositive reservoirs, represented by Didelphis albiventris (n=27), Rattus rattus (n=24), Thrichomys laurentius (n=2), Mus musculus (n=1) and Monodelphis domestica (n=1), were identified. Among domestic dogs (n=96) seroprevalence reached 21.9%. Miniexon multiplex PCR assays characterized TcI in triatomines. Both TcI and TcII were detected in wild mammal hosts. We conclude that Trypanosoma cruzi circulates within a domestic zoonotic cycle, requiring continuous surveillance. Insecticide application to domiciles does not appear to prevent continuous reintroduction of wild triatomine specimens, presenting a challenge to authorities involved in Chagas disease control.

Phylogenetic characterization of hantaviruses from wild rodents and hantavirus pulmonary syndrome cases in the state of Paraná (southern Brazil).

Over 1,100 cases of hantavirus pulmonary syndrome (HPS) have occurred in Brazil since 1993, but little is known about Brazilian hantaviruses, and many of their rodent hosts remain unknown. The Araucaria hantavirus (ARAUV) was described recently from HPS patients from Paraná, in southern Brazil, but its host could not be identified. In this study, rodents were captured from regions with high HPS prevalence to address this issue. ARAUV RNA was detected in three distantly related rodent species: Oligoryzomys nigripes, Oxymycterus judex and Akodon montensis. Furthermore, a specimen of A. montensis was infected with a Jaborá-like virus, implying that A. montensis can be infected by at least two different hantaviruses. The presence of the same hantavirus strain in three different rodent species and the co-circulation of two different strains in the same rodent species highlight the potential for genomic reassortment, which could have an impact on hantavirus transmission dynamics in nature and on human epidemiology.

Genetic Characterization of Hantaviruses Associated with Sigmodontine Rodents in an Endemic Area for Hantavirus Pulmonary Syndrome in Southern Brazil

An ecological assessment of reservoir species was conducted in a rural area (Jaborá) in the mid-west of the state of Santa Catarina in southern Brazil, where hantavirus pulmonary syndrome is endemic, to evaluate the prevalence of hantavirus infection in wild rodents. Blood and tissue samples were collected from 507 rodents during seven field trips from March 2004 to April 2006. Some of the animals were karyotyped to confirm morphological identification. Phylogenetic reconstructions of rodent specimens, based on the mitochondrial DNA cytochrome b gene sequences, were also obtained. Hantavirus antibody was found in 22 (4.3%) of the 507 rodents: 5 Akodon montensis, 2 Akodon paranaensis, 14 Oligoryzomys nigripes, and 1 Sooretamys angouya. Viral RNAs detected in O. nigripes and A. montensis were amplified and sequenced. O. nigripes virus genome was 97.5% (nt) and 98.4% (nt) identical to sequences published for Araucaria (Juquitiba-like) virus based on N and G2 fragment sequences. Viral sequences from A. montensis strain showed 89% and 88% nucleotide identities in a 905-nt fragment of the nucleocapsid (N) protein-coding region of the S segment when it was compared with two other Akodontine rodent-associated viruses from Paraguay, A. montensis and Akodon cursor, respectively. Phylogenetic analysis showed the cocirculation of two genetic hantavirus lineages in the state of Santa Catarina, one from O. nigripes and the other from A. montensis, previously characterized in Brazil and Paraguay, respectively. The hantavirus associated with A. montensis, designed Jaborá virus, represents a distinct phylogenetic lineage among the Brazilian hantaviruses.

Genetic characterization of a Juquitiba-like viral lineage in Oligoryzomys nigripes in Rio de Janeiro, Brazil

Hantaviruses, family Bunyaviridae, are rodent-borne RNA viruses that have caused cases of hantavirus cardiopulmonary syndrome (HCPS) in various regions of the Americas. There are five hantaviral lineages associated with HCPS in Brazil: Juquitiba virus (JUQV), Araraquara virus (ARAV), Laguna Negra-like virus (LNV), Castelo dos Sonhos virus (CASV), and Anajatuba virus (ANAJV). Three additional hantaviruses have been described in rodents alone: Rio Mearim virus, Jaborá virus, and a hantavirus lineage related to Seoul virus. This study describes the genetic detection and characterization of a Juquitiba-like hantavirus in Oligoryzomys nigripes, or the black-footed pygmy rice rat, in the Serra dos Orgãos National Park, Rio de Janeiro State, where so far no cases of HCPS have been reported.

An ecological field study of the water-rat Nectomys squamipes as a wild reservoir indicator of Schistosoma mansoni transmission in an endemic area

Small mammals are found naturally infected by Schistosoma mansoni, becoming a confounding factor for control programs of schistosomiasis in endemic areas. The aims of this study were: to investigate the infection rates by S. mansoni on the water-rat Nectomys squamipes during four years in endemic areas of Sumidouro, state of Rio de Janeiro, using mark-recapture technique; to compare two diagnostic methods for schistosomiasis; and to evaluate the effects of the chemotherapy in the human infected population on the rodent infection rates. The rodent infection rates of S. mansoni increased when rodent population sizes were lower. Coprology and serology results presented the same trends along time and were correlated. Serology could detect recent infection, including the false negatives in the coprology. The chemotherapy in the humans could not interrupt the rodent infection. Rodents can increase the schistosomiaisis transmission where it already exists, they probably maintain the transmission cycle in the nature and can be considered as biological indicators of the transmission sites of this parasite since they are highly susceptible to infection. The water-rats may present different levels of importance in the transmission dynamics of S. mansoni infection cycle for each area, and can be considered important wild-reservoirs of this human disease.