RESUMO
Karyotype and cytotype variations for the large hairy armadillo (Chaetophractus villosus) were studied throughout the species' Argentine distribution. Peripheral blood lymphocyte cultures of 421 animals were used to obtain mitotic metaphases. Preparations were subjected to conventional staining, G- and C-banding, and FISH involving a telomeric probe. Meiotic analysis was performed on testis material from 10 adults. Spermatocytes were examined for synaptonemal complexes in microspreads. The karyotype (2n = 60 XX/XY; FN = 84 without XY) showed an autosomal complement of 6 metacentric and 7 submetacentric chromosomes; the remainder was acrocentric. The X chromosome was submetacentric and the Y acrocentric. Centromeric C+ marks were observed in all chromosomes except pair 16. Three NOR signals were detected in 6q, 12p, and 26p. Two chromosomal rearrangements were characterized in chromosome pair 1 a pericentric inversion seen in the material from Jacinto Aráuz, General Madariaga and Pellegrini and a deletion in the material from Loma Verde. Interstitial telomeric signals were observed in chromosome pairs 4, 12, 16, and 26. Pachytene spermatocyte analysis confirmed the basic chromosome number and morphologies observed in mitotic karyotypes. The evolution of C. villosus involved chromosomal rearrangements as recorded for other species of its superorder. The present results establish the basis for the cytogenetic characterization of this species.
Assuntos
Tatus/genética , Deleção Cromossômica , Inversão Cromossômica , Animais , Argentina , Células Cultivadas , Bandeamento Cromossômico/veterinária , Cromossomos de Mamíferos/genética , Feminino , Variação Genética , Hibridização in Situ Fluorescente/veterinária , Cariótipo , Linfócitos/citologia , Masculino , Meiose/genética , Mitose/genética , Espermatócitos/citologia , Complexo Sinaptonêmico/genéticaRESUMO
The anatomy and histology of the male genital tract of the lesser anteater were studied. Fine details of spermatozoa regarding their genesis and morphology were also studied in six adult specimens. The testes lie in the pelvic cavity. The deferent duct emerges from the epididymis and opens into the ejaculatory duct, which drains into the membranous urethra. Accessory glands (prostate, seminal vesicle and bulbourethral gland) are histologically similar to those described in other mammals. The short penis presents an urethral orifice, while the corpus spongiosum becomes thinner at the end indicating the absence of a histologically defined glans. The seminiferous epithelium shows: (1) Sertoli cells with deep nuclear indentations, (2) spermatogonia with crusty-like chromatin, (3) spermatocytes at different stages of maturation and (4) three morphologically distinct stages of spermatid differentiation according to nuclear shape, acrosome development and chromatin condensation. Sperm heads appear oval. The length of the spermatozoa averages 67.33 ± 1.60 µm. Two specimens with inactive spermatogenesis were azoospermic. Their testes and epididymis presented sizes smaller than those with active spermatogenesis. These studies together with others in anteaters may contribute to successful breeding in conservation programmes.
Assuntos
Genitália Masculina/anatomia & histologia , Genitália Masculina/fisiologia , Espermatogênese/fisiologia , Xenarthra/fisiologia , Animais , Masculino , Estações do AnoRESUMO
The morphological and histological features of the unusual reproductive tract of the female lesser anteater, Tamandua tetradactyla (Myrmecophagidae, Xenarthra), are described for the first time. The present study aimed to establish the main similarities and differences between this species and other xenarthrans. The populations of this species are declining rapidly for a number of reasons and our study is relevant to diverse programs related to its conservation. Studies were carried out on five female genital tracts of adult specimens. Ovaries were ovoid, presenting a medulla completely surrounded by the cortex, differently from that described in other xenarthans. Like in Dasypus but different from all other armadillos studied, single oocyte follicles were observed and a simple the uterus. The uterovaginal canal connects the uterus with the urogenital sinus. The simple columnar epithelium of the uterovaginal canal ends abruptly at a septum which resembles a hymen, where the transitional epithelium of the urogenital sinus appears. This ancestral feature is shared with that of other armadillos, except Tolypeutes matacus, which has a true vagina. Characteristics of the reproductive tract and sperm morphology of other Xenarthra are comparatively discussed. These observations suggest that important reproductive features are shared between the family Myrmecophagidae and the genus Dasypus, a basal group in the phylogeny of Xenarthra.
Assuntos
Genitália Feminina/anatomia & histologia , Sistema Urogenital/anatomia & histologia , Xenarthra/anatomia & histologia , Animais , Feminino , Ovário/anatomia & histologia , Oviductos/anatomia & histologia , Útero/anatomia & histologiaRESUMO
Spermatocytes from the two armadillo species, C. villosus and D. hybridus were studied in microspreads for synaptonemal complexes (SCs) and in thin sections for electron microscopy (EM). The complete SC karyotype generally agrees with previous reports on mitotic chromosomes, except for the sex chromosomes. The X chromosome is submetacentric in both species and the Y is the shortest one in C. villosus and the second shortest in D. hybridus, and an extremely acrocentric one. A SC is formed along the total length of the Y chromosome, and this SC persists along all the pachytene substages. A single recombination nodule (RN) is located in the region of the SC nearest to the attachment to the nuclear envelope. The lateral element (LE) of the X axis in the SC shows a wavy aspect in most of the SC length distant from the nuclear envelope. Nucleoli are attached to acrocentric or submetacentric bivalents, are visibly double in some cells, and in thin sections show an elaborate nucleolonema. Some differences in the XY are species-specific, as the higher degree of tangling and stronger heteropycnosis in D. hybridus. The effective, single crossover of the XY pair is highly localized, despite the permanence of a long tract of SC.
Assuntos
Tatus/anatomia & histologia , Tatus/genética , Complexo Sinaptonêmico/ultraestrutura , Cromossomo X/ultraestrutura , Cromossomo Y/ultraestrutura , Animais , Argentina , Evolução Biológica , Troca Genética , Cariotipagem , Masculino , Especificidade da Espécie , Espermatócitos/ultraestruturaRESUMO
Spermatocytes from the two armadillo species, C. villosus and D. hybridus were studied in microspreads for synaptonemal complexes (SCs) and in thin sections for electron microscopy (EM). The complete se karyotype generally agrees with previous reports on mitotic chromosomes, except for the sex chromosomes. The X chromosome is submetacentric in both species and the Y is the shortest one in C. villosus and the second shortest in D. hybridus, and an extremely acrocentric one. A SC is formed along the total length of the Y chromosome, and this SC persists along all the pachytene substages. A single recombi-nation nodule (RN) is located in the region of the se nearest to the attachment to the nuclear envelope. The lateral element (LE) of the X axis in the SC shows a wavy aspect in most of the se length distant from the nuclear envelope. Nucleoli are attached to acrocentric or submetacentric bivalents, are visibly double in some cells , and in thin sections show an elaborate nucleolonema. Some differences in the XY are species-specific, as the higher degree of tangling and stronger heteropycnosis in D. hybridus. The effective, single crossover of the XY pair is highly localized, despite the permanence of a long tract of SC
Assuntos
Masculino , Animais , Tatus/anatomia & histologia , Tatus/genética , Complexo Sinaptonêmico/ultraestrutura , Cromossomo X/ultraestrutura , Cromossomo Y/ultraestrutura , Argentina , Meiose , Xenarthra/anatomia & histologia , Xenarthra/genéticaRESUMO
The distribution of the vertebrate telomeric sequence (TTAGGG)(n) in four species of armadillos (Dasypodidae, Xenarthra), i.e. Chaetophractus villosus (2n = 60), Chaetophractus vellerosus (2n = 62), Dasypus hybridus (2n = 64) and Zaedyus pichiy (2n = 62) was examined by FISH with a peptide nucleic acid (PNA) probe. Besides the expected telomeric hybridization, interstitial (centromeric) locations of the (TTAGGG)n sequence were observed in one chromosome pair of Chaetophractus vellerosus and Zaedyus pichiy, suggesting chromosome fusion of ancestral chromosomes occurring during the evolution of Dasypodidae. In addition, all the species analysed showed one to four apparently telocentric chromosomes, exhibiting only two telomeric signals. However, the immunodetection study of kinetochore proteins on synaptonemal complex spreads from C. villosus showed that the apparently telocentric chromosomes have a tiny short arm that can be resolved only in the more elongated pachytene bivalents. This finding suggests that none of the species of armadillos possess true telocentric chromosomes. Our present results support a reduction in the diploid number by fusion of acrocentrics with loss of chromosome material as a tendency in Dasypodidae.
Assuntos
Tatus/genética , Sequências Repetitivas de Ácido Nucleico/genética , Telômero/ultraestrutura , Xenarthra/genética , Animais , Argentina , Cromossomos/ultraestrutura , Evolução Molecular , Hibridização in Situ Fluorescente , CariotipagemRESUMO
We quantitatively analyzed the spermatogenic process, including evaluation of seminiferous tubules with defective cycles, rates of germ cell death and sperm morphology, in adult male mice with standard telocentric chromosomes (2n = 40, CD1 strain), homozygous (2n = 24, Mil II population) and heterozygous (2n = 24 x 40) for Robertsonian (Rb) rearrangements. The animals were analyzed at three different ages: three, five and seven months after birth. The number and position of crossover events were also determined by chiasmata counting and immunostaining with an antibody against mouse MLH1 protein. Our analysis of spermatogenesis confirms the impairment of the spermatogenic process in multiple simple heterozygotes due to both germ cell and abnormal sperm morphology. The detrimental effects exerted by Rb heterozygosities were found to be at least partially buffered with time: the frequency of defective tubules was lower and germ cell survival and sperm morphology better in 7-month-old animals than in the 3- and 5-month-old mice. While there are previously published data on germ cell death in multiple simple heterozygotes, this is the first report of a partial rescue of spermatogenesis with time. The mean frequency of MLH1 foci was lower in Rb homozygous and heterozygous mice than in mice carrying all telocentric chromosomes. The lower number of foci in Rb mice can be ascribed to a decrease in the number of multiple chiasmata and the maintenance of single chiasmata preferentially located in the terminal region of both the telocentric and metacentric chromosomes.
Assuntos
Troca Genética , Espermatogênese/genética , Espermatozoides/citologia , Translocação Genética , Proteínas Adaptadoras de Transdução de Sinal , Fatores Etários , Animais , Proteínas de Transporte , Heterozigoto , Cariotipagem , Masculino , Meiose , Camundongos , Proteína 1 Homóloga a MutL , Proteínas de Neoplasias/análise , Proteínas Nucleares , Espermatozoides/química , Testículo/anatomia & histologiaRESUMO
Information about the morphology of placentas in armadillos is scarce, except for D. novemcinctus. A comparative study of morphologic placental types in armadillos is important in order to have a comprehensive view of the peculiar reproductive physiology in this family. The aim of this paper is to perform a comparative analysis of the morphological features of the placenta in Chaetophractus villosus, Cabassous chacoensis, Tolypeutes matacus and Dasypus hybridus in order to classify them in accordance with Grosser (1909). The placentas were studied macroscopically and histologically (light microscopy in 1 micron thick sections and electron microscopy for fine structure). The macroscopic study in the 4 studied species showed a similar pear-shaped placenta homogeneously villosus in almost all the surface. The histological analysis showed that the 4 studied species had a hemochorial type of placenta. This type of placenta was also found in D. novemcinctus (Dasypodidae), but it is different from those described for other xenarthrans. Hemochorial types of placenta have also been described in more modern mammals. Despite the many primitive features of the armadillos and the different anatomical and physiological features between the genuses of dasypodids, all the studied species share this structural type of placenta.
Assuntos
Tatus/embriologia , Placenta/anatomia & histologia , Animais , Tatus/classificação , Feminino , Placenta/ultraestrutura , GravidezRESUMO
The karyotype with C-, G- and NOR-banding of Arctocephalus australis is reported for the first time. The chromosomal number is 2n = 36. The X chromosome, identified in G-banded metaphases from males, is metacentric and the Y chromosome is a minute chromosome, also metacentric. Pachytene spermatocytes were used for synaptonemal complexes analysis with a surface spreading technique. A total of 17 autosomal synaptonemal complexes are observed plus the XY pair. During early pachytene, the X and Y axes are thickened and remain unpaired. As pachytene advances, a short SC is formed between the gonosomes, as it is common among eutherian mammals. The particular asymmetrical appearance of the synaptonemal complex in the sex pair is described and compared to other cases among mammals.
Assuntos
Otárias/genética , Animais , Bandeamento Cromossômico , Feminino , Masculino , Meiose , Mitose , Espermatócitos/ultraestrutura , Complexo Sinaptonêmico , Cromossomo X/ultraestrutura , Cromossomo Y/ultraestruturaRESUMO
Little is known about the evolution of vertebrate spermatozoa. In most eutherian taxa a high degree of uniformity in sperm shapes and dimensions among species was observed. The aim of this work is to trace a possible evolutionary change in sperm morphology and morphometry in dasypodids. The main difference between the spermatozoa of the studied armadillos is the shape of the sperm heads. We have classified the spermatozoa into 4 different groups according with their head shapes. Sperm from group 1 (Dasypus) are considered ancestral and are clearly separated from the others. The remaining sperm types are derivative ones; those from group 2 (Tolypeutes) are farther from those of groups 3 (Priodontes and Cabassous) and 4 (Chaetopractus, Zaedyus and Euphractus) which would have recently differentiated from each other. The sperm shape and size are not constant across taxa in armadillos; an important evolutive differentiation was established on the sperm morphology and morphometry between the different genera in Dasypodidae.
Assuntos
Tatus , Evolução Biológica , Espermatozoides/ultraestrutura , Animais , MasculinoRESUMO
Most primates studied have the usual XX/XY sex-chromosome system. However, exceptions to this rule among howler monkeys have been suggested by several authors. Recently a quadrivalent was discovered in male meiosis of Alouatta caraya and it was established that this species has an X1X2Y1Y2 sex chromosome system. On that basis, a cytogenetic analysis of 25 males of this species is described, showing the corrected karyotype of this species. Each chromosome involved in the particular sex-chromosome system of this species is identified on the basis of mitotic chromosome measurements, G and C-banding patterns as well as on the relative measurements of synaptonemal complexes. It is now established that A. caraya has a karyotype with 2n = 52 in both sexes, and that the male one shows a single autosome #7 (X2) besides the X (X1) and the two products of the reciprocal translocation between the second autosome #7 and the Y chromosome (Y1 and Y2), while females show a homomorphic pair #7 (X2) and a pair of X1. The evolutionary implications of the exceptional primate species having composite sex-chromosome systems are discussed.
Assuntos
Alouatta/genética , Complexo Sinaptonêmico , Animais , Bandeamento Cromossômico , Cariotipagem , Masculino , Espermatócitos/ultraestruturaRESUMO
A multiple sex chromosome system was found in three unrelated individuals of the primate Alouatta caraya. This mechanism is originated by a translocation between the Y chromosome and one of the autosomes (A7). Mitotic karyotypes show two small, acrocentric chromosomes (AY and YA), which are the translocation products. In metaphase I of male meiosis, there is a very long chain quadrivalent in which the order of the element is: X-YA-A7-AY. Segregation in the quadrivalent is alternate and gives balanced products. Synaptonemal complex karyotypes at pachytene show the structure of the quadrivalent made by the four axes. There is a slight difference in the relative length of AY and YA and the kinetochore of A7 aligns with that of AY. The synaptic pattern and changes in the quadrivalent during pachytene are described. Thin sections of the quadrivalent body show that the chromatin packing in the sex chromosome region is different from that of the autosomal region. This X1X2Y1Y2/X1X1XX2 sex chromosome system may be extended among other members of the genus Alouatta.
Assuntos
Alouatta/genética , Meiose/genética , Cromossomo X/genética , Cromossomo Y/genética , Animais , Bandeamento Cromossômico , Cariotipagem , Masculino , Microscopia Eletrônica , Complexo Sinaptonêmico/genética , Translocação Genética , Cromossomo X/ultraestrutura , Cromossomo Y/ultraestruturaRESUMO
The response to infection with Junin virus, wild strain Cba An 9446, and the antenatal and postnatal transmission of the pathogen in its natural host, Calomys musculinus, were studied. Intranasal infection in adult animals (90-120 days) did not produce mortality or illness during the 150-day period of observation. From day 21 to 150 after infection, 50% of the animals showed viral persistence with shedding of virus in both urine and saliva. The remaining half became seropositive, and no infectious virus was recovered from them. Although the virus did not infect fetuses during gestation, 50% of weaned pups nursed by viremic mothers were infected. Neither persistence nor immunologic response altered the reproductive pattern of the animals. The absence of reproductive failure in the infected host and the efficiency of postnatal transfer of Junin virus indicate that vertical transmission could contribute to the viral maintenance over time.
Assuntos
Arenavirus do Novo Mundo , Febre Hemorrágica Americana/transmissão , Animais , Arvicolinae , Feminino , Febre Hemorrágica Americana/microbiologia , Masculino , Troca Materno-Fetal , Gravidez , Complicações Infecciosas na Gravidez , ReproduçãoRESUMO
Serum samples from urban and laboratory rats, laboratory mice and wild and laboratory cricetids in Argentina were tested by immunofluorescence and plaque reduction neutralization tests to investigate prevalence of anti-Hantavirus antibodies. A total of 102 sera were obtained from laboratory rodents in 4 different animal-rooms, 31 from harbor rats and 30 from wild cricetids in 1985-1987. Anti-Hantavirus antibodies were detected in 22.5% of Rattus norvegicus in 3 of the animal-rooms but harbor rats were found to be free of Hantavirus infection. Previously, the presence of anti-Hantavirus antibodies had been demonstrated in the sera obtained from laboratory workers in these same 3 animal-rooms; it can be concluded that the laboratory rats were the source of this human infection. On the contrary, laboratory mice and cricetids failed to show Hantavirus infection while the wild vesper mouse Calomys musculinus (the main Junin virus reservoir) showed a prevalence of 23.5%. The presence of Hantavirus infection is hereby reported for the first time in wild C. musculinus and in laboratory R. norvegicus in Argentina.
Assuntos
Animais de Laboratório , Animais Selvagens/microbiologia , Anticorpos Antivirais/análise , Reservatórios de Doenças , Febre Hemorrágica com Síndrome Renal/veterinária , Orthohantavírus/imunologia , Animais , Argentina , Arvicolinae/microbiologia , Imunofluorescência , Febre Hemorrágica com Síndrome Renal/transmissão , Camundongos , Testes de Neutralização , RatosRESUMO
Se determinó la presencia de anticuerpos anti-Hantavirus en sueros provenientes de roedores salvajes (de zonas urbanas y de campo) y de laboratorio para estudiar la existencia o no de infección con Hantavirus en la Argentina. Se utilizaron las técnicas de inmunofluorescencia indirecta (IF) y de reducción de placas por neutralización (PRNT). Ciento dos sueros correspondían a roedores de laboratorio pertenecientes a 2 bioterios de Mendoza y a 2 de Buenos Aires; 31 sueros fueron rcogidos de ratas urbanas capturadas en el puerto de Buenos Aires y 30 sueros pertenecían a cricétidos salvajes capturados en campos de Buenos Aires y Mendoza (Tabla 1). Se detectaron anticuerpos anti-Hantavirus en colonias de Rattus norvegicus de 3 de los 4 bioterios estudiados (22,5%) en estos mismos lugares. Previamente se habían detectado anticuerpos en sueros humanos por lo que, descartando otros orígenes para la infección, se determinó que las ratas de laboratorio son los candidatos más probables de diseminación del virus en humanos en estos ambientes. En las ratas del puerto de la ciudad de Buenos Aires no se encontraron anticuerpos ni por IF ni por PRNT. En las colonias de ratones y cricéticos de laboratorio no se encontró infección con Hantavirus, mientras que en cricétidos salvajes se demostró la presencia de Hantavirus tanto en Buenos Aires como en Mendoza. En la naturaleza se encontraron anticuerpos séricos anti-Hantavirus en un cricétido reservorio del virus Junín (agente etiológico de la fiebre...
Assuntos
Camundongos , Ratos , Animais , Anticorpos Antivirais/análise , Reservatórios de Doenças , Vírus Hantaan/imunologia , Febre Hemorrágica com Síndrome Renal/diagnóstico , Animais Selvagens/microbiologia , Argentina , Arvicolinae/microbiologia , Imunofluorescência , Febre Hemorrágica com Síndrome Renal/transmissão , Testes de NeutralizaçãoRESUMO
The husbandry and breeding of Calomys laucha (Rodentia, Cricetidae) in captivity are described. Growth curves based on body weight and length showed statistical differences between sexes after 45 days, males being heavier than females. The overall reproductive efficiency was 53.4% but birth rate was depressed during winter. Gestation length was 21 +/- 1 days and females exhibited postpartum oestrus with a 3-7 day implantation delay (51%). Litter size was 5.3 +/- 1.1 (n = 34). Pup survival at weaning was 84.9%. Mean life span in laboratory conditions was 13.5 months and a cumulative mortality of 90% was reached at 27-28 months of age.
Assuntos
Animais de Laboratório/crescimento & desenvolvimento , Arvicolinae/crescimento & desenvolvimento , Criação de Animais Domésticos , Animais , Cruzamento , Feminino , Longevidade , Masculino , Gravidez , Fatores SexuaisRESUMO
The meiotic behavior of sex chromosomes has been investigated in variant females of Akodon azarae, both in pachytene oocytes and metaphase I. In somatic cells, these females have a heteromorphic sex pair, in which the minor chromosome has been previously interpreted as a major deletion of the long arm of the X chromosome (dX). After microspreading for synaptonemal complex analysis, pachytene oocytes show two axes of very different lengths (100:17.1), which correspond to the sex chromosomes X and dX. True synapsis is abnormally restricted (43.3%) between these sex chromosomes; on the other hand, self-synapsis of both the X and dX chromosomes is frequent (60%). Single, nonsynapsed axes or axial segments are thickened. Strong chromatin condensation occurs around nonsynapsed axes or axial segments, giving many of these sex pairs an appearance similar to an XY body ("sex vesicle"). The minor gonosome axis differs from that of the Y chromosome of male meiosis, as the former is shorter (relative to the X) and has a different synaptic behavior. In 17 metaphases I from XdX variant females, only heteromorphic, end-to-end joined sex pairs were observed. These variant females differ from the variant females of the wood lemming Myopus schisticolor in several respects, but a similar mechanism seems to be prevalent in other species of the genus Akodon. Self-synapsis of unequal gonosomes in oocytes is assumed as an escape from functional deterioration, following the hypothesis put forward by others.
Assuntos
Arvicolinae/genética , Deleção Cromossômica , Meiose , Oócitos/ultraestrutura , Cromossomo X , Animais , Variação Genética , Humanos , Interfase , Cariotipagem , Masculino , Metáfase , Oogênese , Razão de Masculinidade , Espermatócitos/ultraestrutura , Complexo Sinaptonêmico , Cromossomo X/ultraestrutura , Cromossomo Y/ultraestruturaRESUMO
Present knowledge points to horizontal transmission as the most significant mechanism for Junín virus maintenance in the main natural reservoirs, namely Calomys musculinus and Calomys laucha. The existence of naturally infected Akodon azarae, both within and outside the endemic area, as well as the finding that other species, ecologically and phylogenetically related to the main reservoirs, such as Akodon molinae and Calomys callidus, can experimentally develop persistent infections with virus shedding through fauces, suggest a potential role for these cricetids as alternative reservoirs. Furthermore, since those rodents inhabit the borders of the area in which Argentine Hemorrhagic fever is endemic, the risk of spread of this area is to be expected. Whether the establishment of Junín virus persistence in Calomys musculinus and other reservoirs depends on viral or host factors, such as a selective defect in L3T4+ lymphocytes as recently shown for mice, remains to be explored.
Assuntos
Febre Hemorrágica Americana/epidemiologia , Animais , Arenavirus do Novo Mundo/isolamento & purificação , Argentina , Modelos Animais de Doenças , Febre Hemorrágica Americana/transmissão , Humanos , Roedores/microbiologiaRESUMO
The quantitative contribution of vertical transmission to the prevalence rate of Junin virus infection in subsequent generations of its natural reservoir, Calomys musculinus, was analysed. Data on mortality and reproduction of C. musculinus infected at birth with a wild strain of Junin virus were used to estimate the infection-dependent relative survival rate (beta = 0.4849) and relative fertility of the infected host (alpha = 0.2088). Prevalence rates of infection, obtained by mathematical simulation in optimal conditions of vertical transfer, dropped steadily to zero in a few generations. Vertical transmission was found to be insufficient to overcome the effect of highly depressed survival and fertility of the infected host and maintain a stabilized prevalence of Junin virus infection in successive generations; this suggested that viral maintenance is mainly dependent upon horizontal transmission.
Assuntos
Arvicolinae , Reservatórios de Doenças , Febre Hemorrágica Americana/veterinária , Doenças dos Roedores/transmissão , Animais , Arenavirus do Novo Mundo/crescimento & desenvolvimento , Febre Hemorrágica Americana/epidemiologia , Febre Hemorrágica Americana/transmissão , Matemática , Doenças dos Roedores/epidemiologiaRESUMO
The effect of infection with Junin virus on growth and reproduction of its natural reservoir, Calomys musculinus, was studied. Eighty-five C. musculinus were inoculated intranasally at birth with 100 TCID50 of Cba An 9446 strain of Junin virus and observed for 480 days. No clinical signs of neurologic illness were registered. Infected animals showed an increased mortality rate of up to 70% between days 24-40 post-infection. This period of high mortality was preceded by low weight gain during lactation and registered until 60 days. From day 14 post-infection until day 480, Junin virus was recovered from blood, urine, and oral swab in all animals checked at any time. By day 480 post-infection, 100% of survivors showed widespread viral dissemination in brain, spleen, kidneys, and salivary glands. There was marked reduction in reproductive efficiency among infected animals. Out of 15 mating pairs, 2 (13.3%) littered at least once compared to 60% in the control group. The reduction of fertility and the altered survival rate of Junin virus-infected C. musculinus indicate that vertical transmission mechanisms per se are insufficient to maintain the infection in successive generations in the absence of horizontal transmission.