Large Rodent Research Articles

Multiscale patterns of habitat and space use by the pacarana Dinomys branickii: factors limiting its distribution and abundance

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 16:273-281 (2012) - DOI: https://doi.org/10.3354/esr00391 Multiscale patterns of habitat and space use by the pacarana Dinomys branickii: factors limiting its distribution and abundance Carlos A. Saavedra-Rodríguez1,2,*, Gustavo H. Kattan3,4, Karin Osbahr5, Juan Guillermo Hoyos4 1Wildlife Conservation Society Colombia Program, Carrera 25 No. 4-39, Cali, Colombia 2Grupo de Investigación en Ecología Animal, Departamento de Biología, Universidad del Valle, A. A. 25360, Cali, Colombia 3Departamento de Ciencias Naturales y Matemáticas, Pontificia Universidad Javeriana, Calle 18 No. 118-250, Cali, Colombia 4Fundación EcoAndina, Carrera 2 A Oeste No. 12-111, Cali, Colombia 5Unidad de Investigación en Fauna Silvestre, Universidad de Ciencias Aplicadas y Ambientales, Calle 222 No. 55-37, Bogotá, Colombia *Email: casaavedrar@yahoo.com ABSTRACT: The factors that influence habitat and space use by animals, and therefore their distribution and abundance, vary with spatial scale. The pacarana Dinomys branickii is a large rodent of the tropical Andes threatened by illegal hunting and habitat loss. We identified variables related to pacarana habitat use at 4 spatial scales in the Colombian Andes: landscape (3.14 km2 circles), forest patch, foraging area, and den. At the landscape scale, pacaranas used areas with 20 to 95% forest cover that were not different from randomly sampled sites. At the forest fragment scale, used patches (mean = 12 ha) were larger than unused patches, but independent of distance to continuous forest. At the foraging area scale, habitat use was related to the presence of rocky caves used as dens and was unrelated to forest structure. At the den scale, pacaranas used deep caves (>4 m) in sloping rocky outcrops with >40% exposed rock (in 100 m2 patches). Pacarana groups (4 to 5 individuals) had a mean home range of 2.45 ha around caves. We estimated a population density of 9.9 and 5.5 groups km−2 based on sign clusters (footprints, latrines, and foraging areas) and dens, respectively. Pacaranas fed on a variety of plant families found in primary and secondary forest and disturbed areas near streams. Our results indicate that pacaranas can survive in forest fragments, and the main factor limiting their distribution and abundance is the availability of adequate dens. Conservation of pacarana populations in rural landscapes may be helped by protecting a network of forest patches connected by riparian vegetation, but these populations would be vulnerable to illegal hunting. KEY WORDS: Den · Forest fragmentation · Habitat use · Home range · Population density Full text in pdf format Supplementary material PreviousNextCite this article as: Saavedra-Rodríguez CA, Kattan GH, Osbahr K, Hoyos JG (2012) Multiscale patterns of habitat and space use by the pacarana Dinomys branickii: factors limiting its distribution and abundance. Endang Species Res 16:273-281. https://doi.org/10.3354/esr00391 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 16, No. 3. Online publication date: March 22, 2012 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2012 Inter-Research.

Classification Tree Methods Provide a Multifactorial Approach to Predicting Insular Body Size Evolution in Rodents

Many hypotheses have been proposed to explain size changes in insular mammals, but no single variable suffices to explain the diversity of responses, particularly within Rodentia. Here in a data set on insular rodents, we observe strong consistency in the direction of size change within islands and within species but (outside of Heteromyidae) little consistency at broader taxonomic scales. Using traits of islands and of species in a classification tree analysis, we find the most important factor predicting direction of change to be mainland body mass (large rodents decrease, small ones increase); other variables (island climate, number of rodent species, and area) were significant, although their roles as revealed by the classification tree were context dependent. Ecological interactions appear relatively uninformative, and on any given island, the largest and smallest rodent species converged or diverged in size with equal frequency. Our approach provides a promising framework for continuing examination of insular body size evolution.

Anesthesia and Analgesia in Rabbits and Rodents

Rabbits and rodents are popular pets and are often presented to veterinarians for evaluation and medical treatment. Anesthesia in exotic pets is required for many diagnostic and surgical procedures and is associated with a higher perioperative risk in rabbits and rodents when compared with dogs and cats. Inhalation anesthetic agents are commonly used as the sole source of anesthesia in small rodents, whereas injectable agents in combination with inhalation anesthesia are often used for rabbits and larger rodents. Analgesia is an important component of exotic pet medicine. Although it may be difficult to recognize signs of pain in companion exotic mammals, adequate pain management should always be provided. Opioid and nonsteroidal antiinflammatory drugs are the analgesic medications of choice, but others should be considered (e.g., local anesthetic agents). This article provides an update of the current literature regarding anesthesia and analgesia in rabbits and rodents.

Old World Hantavirus Infection in Rattus Species and Risk Management in Urban Neighborhoods of New Orleans, Louisiana

Author(s): Freeman, Ashley; Cross, Robert; Riegel, Claudia; Waffa, Bradley; Brown, Joyce; Moses, Lina; Bennett, Andrew; Bond, Nell; Greene, Mary; Voss, Tom; Bausch, Daniel | Abstract: Hantaviruses are lipid-enveloped, tri-segmented RNA viruses belonging to the family Bunyaviridae. Hantaviruses are divided taxonomically into Old World and New World groups that typically cause hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome, respectively. Each hantavirus is specific to a rodent reservoir host. In 1983, isolation of an Old World hantavirus similar to Seoul virus (Tchoupitoulas virus) occurred from rats caught in New Orleans, Louisiana, but to date, this virus has not been associated with human disease. Since that time, no hantavirus surveillance has been conducted in this geographic area. We sought to determine if Old World hantaviruses still circulate in rodents in New Orleans and, if so, to decrease rat populations to reduce the risk of human-rodent interaction and the potential for disease transmission. Over a 3-year period, rodents were live-trapped using Sherman and Tomahawk traps. Blood and other tissues were collected and samples tested for the presence of Old World hantaviruses via Reverse transcriptase Polymerase Chain Reaction. Trap sites were identified through selected citizen service requests and routine municipal rodent management activities. Of the 172 roof rats and Norway rats collected, 3.6% tested positive, indicating continued presence of Old World hantaviruses in New Orleans. This study raised awareness of the continued risk of rodent-borne disease in the greater New Orleans area and spawned proactive management strategies on a city-wide basis, including neighborhood surveys, public education and awareness campaigns, and an aggressive rodenticide baiting program in areas with large rodent populations. Continued surveillance and detection of hantaviruses and other rodent-borne pathogens will help preserve the safety and health of New Orleans residents.

Performance and Energy Requirements of Gestating Grasscutters Fed Agro-Industrial By-Products

The grasscutter (Thryonomys swinderianus) is a large herbivorous rodent of the grasslands of Sub-Sahara Africa. It is an important source of much-needed animal protein; and holds promise as an acceptable ‘bushmeat’ substitute for the hunted and endangered wildlife animal species of West Africa. The intensive production of the grasscutter would require the supply of inexpensive and adequate dietary nutrients. Energy requirement was determined using sixteen 8-months old gestating grasscutters. The grasscutters were separated into four groups and fed diets, which differed in their energy contents of 2000, 2200, 2400, and 2600 kilocalories metabolizable energy per kilogram (Kcal ME/kg). The test diets had the same crude protein (CP) level of 18%. The results showed that total feed intake was significantly (P<0.05) higher on the 2200 kcal ME/kg diet than on other diets. Weight gain was highest on the 2200 kcalME/kg diet. Average litter size was significantly (P<0.05) higher on the 2200 kcalME/kg and 2400 kcal ME/kg diets. The average birth weight of grasscutter pups was significantly (P<0.05) higher on the 2200 kcalME/kg and 2600 kcalME/kg diets. Taken together, growth and reproductive performance of gestating grasscutters was superior, on the 2200 kcalME/kg diet, to performance on other diets. The results of this study suggest that agro-industrial by-products, soybean and wheat offal in cassava-based diets, can effectively be used at dietary energy level of 2200 kcalME/kg, to rear gestating grasscutters. It is, therefore, concluded that the optimum dietary energy requirement of gestating grasscutters is 2200 kcal ME/kg.

Late Miocene large mammals from Ivand (Northwestern Iran)

Large mammalian fossil fauna of the Ivand locality in northwestern Iran is reported for the first time. This new locality is situated north of the city of Tabriz in the geographical proximity of the famous Maragheh fossil sites. A large hipparion, represented by an almost complete skull and mandibles, is recorded from this locality. The skull, most likely of Hipparion giganteum-Hipparion brachypus lineage, represents significant evidence of the presence of large hipparionine horses in northwestern Iran in the Late Miocene. A small number of horn-cores attributed to Oioceros atropatenes Rodler & Weithofer, 1890 and Gazella sp., in addition to some indeterminate dentition, represent the bovid material in the Ivand fossil assemblage. Postcranial evidence also points to the presence of Deinotherium giganteum Kaup, 1829 and Rhinocerotinae indet., while other material adds carnivorans, giraffes and large porcupine rodents to the list of the fauna. Based on the occurrence of these taxa, the Ivand locality can be correlated with the Middle and Upper Maragheh biostratigraphical intervals, thus demonstrating a middle Turolian age (c. 8–7 Ma).

Prevalence of Toxoplasma gondii infection in Myocastor coypus in a protected Italian wetland

BackgroundToxoplasma gondii is the causative agent for a major zoonosis with cosmopolitan distribution. Water has been implicated in outbreaks of toxoplasmosis in recent years. Coypus (Myocastor coypus), commonly nutria, are large semi-aquatic invasive rodents, naturalized throughout European countries, including most wetlands of Central Italy. The habitat of these animals is both terrestrial and aquatic, making them a species highly exposed to the parasite.FindingsThe occurrence of the infection was evaluated using a modified agglutination test (MAT) in 74 adult coypus from a naturalized population living in a wetland of Central Italy. Nested PCR (n-PCR) assay was carried out on some of them. Positive T. gondii MAT results were found in 44 animals (59·4%), 30 males (68·2%) and 14 females (31·8%). Antibody titers were ranging from 20 to 40960, while 12 out of 23 (52·2%), examined animals, 8 males (66·7%) and 4 females (33·3%), resulted positive to n-PCR. All n-PCR positive animals were seropositive, showing antibody titers ranging from 640 to 40960.ConclusionsOur results indicate that examined animals are heavily parasitized with Toxoplasma. This suggests that coypus could be a reservoir of this parasite, because they can be eaten both by scavenger animals and by humans, and that these animals would play a role in maintaining the cycle of T. gondii.

Diet of Eurasian lynx Lynx lynx in the northern Dinaric Mountains (Slovenia and Croatia)

The Eurasian lynx Lynx lynx (Linnaeus 1758) is an opportunistic predator that usually selects the smallest ungulate available. Its diet varies considerably among different regions; therefore it is important to study lynx diet in different parts of the species' range. We studied the diet of lynx from the endangered Dinaric population in Slovenia and Croatia by analyzing lynx scats, prey remains, and stomach contents. Dinaric lynx mainly killed European roe deer Capreolus capreolus (0.64 frequency of occur- rence, 79% of all consumed biomass), which were used more frequently during winter and spring. Ungulates were killed more often by adult males than by lynx of other age and sex groups. In contrast to studies from other regions, lynx in the northern Dinaric Mountains also frequently fed on the edible dormice Glis glis (0.18 frequency of occurrence, 7% of all consumed biomass). This large rodent appears to be an important alternative prey, especially for females and young lynx, and was the reason for the highest use of rodents reported so far for the Eurasian lynx. Edible dormice in Dinaric forests have highly variable numbers of active animals. Seasonal and possibly annual variation in dormouse availability obvious- ly affects lynx diet. This is a rare example where variability in the availability of the alternative prey and not the preferred prey leads to the dietary shift. This study confirms the opportunistic nature of Eurasian lynx and the regional variability of its diet.

Fruit Removal and Natural Seed Dispersal of the Brazil Nut Tree (Bertholletia excelsa) in Central Amazonia, Brazil

ABSTRACTExperimental approaches to study seed dispersal of the Brazil nut tree have hitherto relied on exposed seeds deposited on the forest floor. Here we use a new method to study the natural dispersal by large rodents such as agoutis; tracking experimentally manipulated and tagged fruits containing individually marked seeds. Fruit manipulation did not deter agoutis from handling fruits. We found that agoutis usually moved intact fruits away from their original location below the parent tree before either hiding them or gnawing through the pericarp to access the seeds inside. Most fruits were moved to distances of 15–30 m from their original position, but some fruits could be taken as far as 60 m. A large number of seeds extracted from manipulated fruits appeared to be eaten immediately. Only 27 out of 1740 experimental seeds were found buried in shallow caches, generally within 5 m of the opened fruit. Fruit removal distance accounted for a disproportionate amount of total seed movement and seeds in the current study were dispersed significantly farther than in a previous experiment using exposed seeds, suggesting that classic dispersal experiments of this character may severely underestimate seed dispersal distances. We therefore conclude that the new method provides a more realistic and accurate approach to investigate natural seed dispersal of Brazil nuts and that the removal of fruits from underneath parent trees before being opened is the key to the significantly increased distances at which seeds are dispersed.Abstract in Portuguese is available at http://www.blackwell‐synergy.com/loi/btp.

Empty forests, empty stomachs? Bushmeat and livelihoods in the Congo and Amazon Basins

SUMMARY Protein from forest wildlife is crucial to rural food security and livelihoods across the tropics. The harvest of animals such as tapir, duikers, deer, pigs, peccaries, primates and larger rodents, birds and reptiles provides benefits to local people worth millions of US$ annually and represents around 6 million tonnes of animals extracted yearly. Vulnerability to hunting varies, with some species sustaining populations in heavily hunted secondary habitats, while others require intact forests with minimal harvesting to maintain healthy populations. Some species or groups have been characterized as ecosystem engineers and ecological keystone species. They affect plant distribution and structure ecosystems, through seed dispersal and predation, grazing, browsing, rooting and other mechanisms. Global attention has been drawn to their loss through debates regarding bushmeat, the “empty forest” syndrome and their ecological importance. However, information on the harvest remains fragmentary, along with understanding of ecological, socioeconomic and cultural dimensions. Here we assess the consequences, both for ecosystems and local livelihoods, of the loss of these species in the Amazon and Congo basins.

The bite force of the largest fossil rodent (Hystricognathi, Caviomorpha, Dinomyidae)

Blanco R.E., Rinderknecht, A. & Lecuona, G. 2011: The bite force of the largest fossil rodent (Hystricognathi, Caviomorpha, Dinomyidae). Lethaia, Vol. 45, pp. 157–163. An exceptionally well-preserved skull of the largest fossil rodent Josephoartigasia monesi allows the first analysis of the bite mechanics of this group of South American giant rodents. In this study, we reconstructed the main anatomical features of the skull of this Pliocene rodent, relating them to the bite force at incisors. Bite force was estimated using three different techniques. Two methods suggest that bite forces at incisors of around 1000 N were possible for these mammals. However, the incisors seem to be stronger than expected for this bite force implying that the bite forces may have been greater than 3000 N. We consider three hypotheses: allometric effects, teeth digging or defence against predators, to explain our results. □Bite force, Dinomyidae, incisors, largest rodent, Pliocene.

Molecular phylogenetics of an endangered species: the Tamaulipan woodrat (Neotoma angustapalata)

Neotoma angustapalata (Tamaulipan woodrat) is a large cricetid rodent found only in southwestern Tamaulipas and northeastern San Luis Potosi, Mexico. This species currently is listed as endangered due to habitat alteration, its restricted distribution, and relative rarity. Previous taxonomic assessments have allied N. angustapalata with N. albigula (now encompassing N. leucodon), N. mexicana or N. micropus. We sequenced portions of the mitochondrial cytochrome b gene from two skin samples of the Tamaulipan woodrat, including one of two topotypes. We estimated genealogical relationships between N. angustapalata and other species of Neotoma using maximum likelihood and Bayesian inference. In general, our results confirm the phylogeny of woodrats as proposed previously but we also recovered major genetic differentiation within what currently is recognized as N. mexicana and N. albigula. Our data document that the Tamaulipan woodrat is genetically indistinguishable from geographically adjacent haplotypes of N. leucodon. However, mitochondrial introgression from N. leucodon cannot be ruled out inasmuch as we were not able to obtain nuclear sequence data for N. angustapalata. Morphological analyses document that both male and female Tamaulipan woodrats differ morphologically from N. leucodon. Given that the Tamaulipan woodrat is diagnosable morphologically and occurs in habitat that differs from N. leucodon, we recognize N. angustapalata as a species-level entity.

Duration of Spermatogenesis and Spermatogenic Efficiency in 2 Large Neotropical Rodent Species: The Agouti (Dasyprocta leporina) and Paca (Agouti paca)

The agouti (Dasyprocta leporina) and paca (Agouti paca) are among the largest extant rodent species. Although these species have considerable economic potential, there are few reports in the literature concerning male reproductive biology in sexually mature agoutis and pacas. The objectives of the present study were to perform detailed stereologic and histologic analyses of the testis and estimate spermatogenic cycle length in these 2 Neotropical rodent species as well as to compare the data with those from other well-studied rodent members of the Hystricomorpha and Myomorpha suborders. Eight adult agoutis and 6 adult pacas were used. The spermatogenic cycle in agoutis and pacas lasted 9.5 ± 0.03 and 11.5 ± 0.16 days, respectively, whereas the total duration of spermatogenesis for these 2 species was 42.8 ± 0.16 and 51.6 ± 0.7 days, respectively. Most of the parameters investigated were similar to those obtained for the other members of the Hystricomorpha suborder. As a result of the combination of high values of seminiferous tubule volume density, number of Sertoli cells per gram of testis, Sertoli cell efficiency, and a relatively short duration of spermatogenesis, the spermatogenic efficiency found in agoutis (52 ± 2 × 10(6)) and pacas (39 ± 2 × 10(6)) was particularly high when compared with that of previously investigated mammalian species. The data presented in this investigation would be useful for studies related to animal production as well as improvement and conservation programs involving these 2 large Neotropical rodent species.

Mandible morphology, dental microwear, and diet of the extinct giant rats Canariomys (Rodentia: Murinae) of the Canary Islands (Spain)

An ecomorphological approach of mandible shape through Fourier analyses combined with a paleodietary analysis of dental microwear patterns is used to reconstruct the diet of the extinct endemic Canariomys bravoi Crusafont, Pairo & Petter, 1964 and Canariomys tamarani Lopez-Martinez & Lopez-Jurado, 1987. These two large rodents, respectively, lived on Tenerife and Gran Canaria, the central islands of the Canarian Archipelago. Mandible shape and dental microwear respectively inform us on the volume of vegetal matter and on the presence of grass in the diet. Both Canariomys, which are of similar size, possess relatively similar mandible outlines and microwear patterns. For each species, a diet based on plant materials except grass is the most likely. Such results chime with the similar environments offered by the islands in which the species lived. On the contrary, molar morphology suggests different feeding habits of the two Canariomys. Thus, this suggests a case of mosaic evolution between teeth and mandibles, as well as the likely sensitivity of mandible shape to a combination of ecological and allometric factors. These new data obtained from the fossil record underline the propensity of island endemic mammals to yield surprising examples of phenotypic evolution.

Splitting placodes: effects of bone morphogenetic protein and Activin on the patterning and identity of mouse incisors

The single large rodent incisor in each jaw quadrant is evolutionarily derived from a mammalian ancestor with many small incisors. The embryonic placode giving rise to the mouse incisor is considerably larger than the molar placode, and the question remains whether this large incisor placode is a developmental requisite to make a thick incisor. Here we used in vitro culture system to experiment with the molecular mechanism regulating tooth placode development and how mice have thick incisors. We found that large placodes are prone to disintegration and formation of two to three small incisor placodes. The balance between one large or multiple small placodes was altered through the regulation of bone morphogenetic protein (BMP) and Activin signaling. Exogenous Noggin, which inhibits BMP signaling, or exogenous Activin cause the development of two to three incisors. These incisors were more slender than normal incisors. Additionally, two inhibitor molecules, Sostdc1 and Follistatin, which regulate the effects of BMPs and Activin and have opposite expression patterns, are likely to be involved in the incisor placode regulation in vivo. Furthermore, inhibition of BMPs by recombinant Noggin has been previously suggested to cause a change in the tooth identity from the incisor to the molar. This evidence has been used to support a homeobox code in determining tooth identity. Our work provides an alternative interpretation, where the inhibition of BMP signaling can lead to splitting of the large incisor placode and the formation of partly separate incisors, thereby acquiring molar-like morphology without a change in tooth identity.

Redundant or complementary? Impact of a colonizing species on community structure and function

Recent studies suggest that species with similar functional traits will have similar effects on ecosystems, but evidence for redundancy of species impacts is limited. Here we use a long-term experiment to gain insight into functional relationships within a desert rodent community. Experimental removal of kangaroo rats, Dipodomys spp., coupled with the recent, serendipitous colonization of a single species of large pocket mouse Chaetodipus baileyi yielded treatments that differed in the diversity of large granivorous rodents present. We evaluated functional overlap of C. baileyi and the other resident large granivores (i.e. the kangaroo rats) by comparing total energy use of granivorous rodents and total abundance and species richness of small granivores across treatments before and after the arrival of C. baileyi. We found that C. baileyi almost completely compensated for the changes in these key ecosystem-level properties caused by kangaroo rat removal, but it differentially impacted the population dynamics of individual small granivorous rodent species. Thus, its effects were largely complementary, rather than redundant, to those of the missing kangaroo rats. Although short-term or single-measure analyses may suggest redundancy, our results support the longstanding dictum that niches of coexisting species are often similar but rarely, if ever, identical.

The Chinese water deer, Hydropotes inermis—A fast-growing and productive ruminant

The Chinese water deer is the most prolific ruminant. The species probably shows other characteristics favouring high productivity and population dynamics. Data on growth, maturity, reproduction and length of life were collected by monitoring a large semi-wild population for 3 years. These data were compared with those known for eight large rodents and 22 other artiodactyls of similar body size. Values for the longevity and age at sexual maturity of water deer are among the lowest of artiodactyls. The young grow faster than most other species and are the most precocious in terms of their age at weaning and at the end of the eruption of most molars. Lastly, both death rate and the renewal of individuals in the population are higher. The water deer appears to be by far the most dynamic ruminant, comparable to large rodents. This enables the species to colonize new areas rapidly. The peculiarities of the water deer fit with other morphological and anatomical features and can be considered as retained ancestral characters. A plausible explanation could lie in the ecological plasticity of the species.

Rapid evaluation of threats to biodiversity: human footprint score and large vertebrate species responses in French Guiana

Although there is an extensive literature demonstrating the impact of human activities on both species extinction risk and local ecological processes, the methodological tools that allow for the visualization and quantification of the intensity of the observed and forthcoming impacts are lacking. Here we propose a Footprint index for French Guiana, (northern Atlantic coast of South America) which sums up the expected and proven disturbances on biodiversity. The index was developed by superimposing geographical and human data, including human population densities, land use, settlements and camps, mining and forest activities, tracks, roads and rivers. The relevance of the index as a general measure of anthropic impact on large terrestrial fauna was estimated by investigating the structure of the large terrestrial vertebrate assemblages, including primates, large frugivorous birds, rodents and ungulates, in relation to the extent of disturbances. The abundance of large terrestrial fauna was assessed using the line-transect sampling method in 34 forest sites facing different disturbance levels, including hunting, logging and fragmentation, and consequently different footprint scores. A Self Organizing Map was used to combine species abundances and disturbance scores. It allowed us to rank species in accordance to their sensitivity towards disturbances, identifying the response of fauna to different concomitant threats. The index provided correct identification of sites with similar threats which proves it is a relevant estimator of human disturbance. In addition, the richness of animal communities and abundances of several seed dispersers and predators were negatively correlated to the index (e.g. large monkeys and frugivorous birds, r 2 = 0.49, P < 0.0001 and r 2 = 0.48, P < 0.0001, respectively), indicating its reliability in identifying areas where animal communities are disturbed. The index could, therefore, constitute a useful tool to identify areas where ecological processes supported by those species are expected to be disrupted, and where they are already disrupted. Furthermore, the footprint index can deal with lack of field data or with only partially valid information, and so may directly help land managers forecast and, hopefully, mitigate forthcoming impacts resulting from the development of human activities.

Experimental Leptospirosis in Capybaras (Hydrochaeris hydrochaeris) Infected with Leptospira interrogans Serovar Pomona

Capybara (Hydrochaeris hydrochaeris), the largest rodent in the world, is widely distributed in South America. These animals live in areas with abundant water, which makes them a potential reservoir for Leptospira. The objective of this study was to investigate seroconversion, leptospiremia, and leptospiruria in capybaras experimentally infected with a virulent strain of Leptospira interrogans serovar Pomona. Seven capybaras were used: one control and six infected. Agglutinins against serovar Pomona were initially detected in serum 6 or 7 day after innoculation with Leptospira (10(9)-10(11) organisms, given i.v.), peaked (titer, approximately 3,200) between 9 and 27 day, and were still present at 83 day (end of study). The earliest and latest isolation of leptospires from the blood was from 2-12 day and from urine, 9-19 day after exposure. However, polymerase chain reaction and isolation results from kidney and liver samples were negative for leptospires. The control animal tested negative on all diagnostic tests. Hence, the capybara can serve as a host for Leptospira.

Rat model of metastatic breast cancer monitored by MRI at 3 tesla and bioluminescence imaging with histological correlation

BackgroundEstablishing a large rodent model of brain metastasis that can be monitored using clinically relevant magnetic resonance imaging (MRI) techniques is challenging. Non-invasive imaging of brain metastasis in mice usually requires high field strength MR units and long imaging acquisition times. Using the brain seeking MDA-MB-231BR transfected with luciferase gene, a metastatic breast cancer brain tumor model was investigated in the nude rat. Serial MRI and bioluminescence imaging (BLI) was performed and findings were correlated with histology. Results demonstrated the utility of multimodality imaging in identifying unexpected sights of metastasis and monitoring the progression of disease in the nude rat.MethodsBrain seeking breast cancer cells MDA-MB-231BR transfected with firefly luciferase (231BRL) were labeled with ferumoxides-protamine sulfate (FEPro) and 1-3 × 106 cells were intracardiac (IC) injected. MRI and BLI were performed up to 4 weeks to monitor the early breast cancer cell infiltration into the brain and formation of metastases. Rats were euthanized at different time points and the imaging findings were correlated with histological analysis to validate the presence of metastases in tissues.ResultsEarly metastasis of the FEPro labeled 231BRL were demonstrated onT2*-weighted MRI and BLI within 1 week post IC injection of cells. Micro-metastatic tumors were detected in the brain on T2-weighted MRI as early as 2 weeks post-injection in greater than 85% of rats. Unexpected skeletal metastases from the 231BRL cells were demonstrated and validated by multimodal imaging. Brain metastases were clearly visible on T2 weighted MRI by 3-4 weeks post infusion of 231BRL cells, however BLI did not demonstrate photon flux activity originating from the brain in all animals due to scattering of the photons from tumors.ConclusionA model of metastatic breast cancer in the nude rat was successfully developed and evaluated using multimodal imaging including MRI and BLI providing the ability to study the temporal and spatial distribution of metastases in the brain and skeleton.