Carriage of Clostridium difficile by Wild Urban Norway Rats (Rattus norvegicus) and Black Rats (Rattus rattus)

Clostridium difficile is an important cause of enteric infections in humans. Recently, concerns have been raised regarding whether animals could be a source of C. difficile spores. Although colonization has been identified in a number of domestic species, the ability of commensal pests to serve as a reservoir for C. difficile has not been well investigated. The objective of this study was to determine whether urban rats (Rattus spp.) from Vancouver, Canada, carry C. difficile. Clostridium difficile was isolated from the colon contents of trapped rats and was characterized using ribotyping, toxinotyping, and toxin gene identification. Generalized linear mixed models and spatial analysis were used to characterize the ecology of C. difficile in rats. Clostridium difficile was isolated from 95 of 724 (13.1%) rats, although prevalence differed from 0% to 46.7% among city blocks. The odds of being C. difficile positive decreased with increasing weight (odds ratio [OR], 0.67; 95% confidence interval [CI], 0.53 to 0.87), suggesting that carriage is more common in younger animals. The strains isolated included 9 ribotypes that matched recognized international designations, 5 identified by our laboratory in previous studies, and 21 “novel” ribotypes. Some strains were clustered geographically; however, the majority were dispersed throughout the study area, supporting environmental sources of exposure and widespread environmental contamination with a variety of C. difficile strains. Given that urban rats are the source of a number of other pathogens responsible for human morbidity and mortality, the potential for rats to be a source of C. difficile for humans deserves further consideration.     

Black rats (Rattus rattus) from medieval Mertola (Baixo Alentejo, Portugal)

This paper is about the analysis and interpretation of micromammal samples from archaeological sites while reporting on a black rat assemblage from XIII^th century Muslim levels in the city of Mertola. Questions concerning skeletal representation, size plus age estimations and bone fragmentation are discussed from a taphonomic standpoint. It is concluded that the tendency to interpret rodent accumulations in anthropic sites as evidence of preybird activities might be an oversimplification in need of substantial revision.     

Frequency of chromosome polymorphism in Rattus rattus collected in Japan

This paper deals with a population survey of chromosome polymorphism of Rattus rattus collected in Japan and the results of their test crosses. All the animals had diploid 42 chromosomes, but three chromosome pairs, Nos. 1, 9 and 13, were polymorphic in respect to acro- and subtelocentric chromosomes. Frequency of No. 1 chromosome polymorphism in 453 rats collected in 19 localities showed 343 rats (75.5%) with acrocentric homomorphic pair (A/A), 90 (19.9%) with aerocentric and subtelocentric heteromorphic pair (A/S) and the remaining 20 (4.4%) with subtelocentric homomorphic pair (S/S). All animals collected in northern and northwestern Japan showed only the A/A pair, while those collected in southern and southeastern Japan showed A/A, A/S and S/S polymorphism. The latter group was also classified into 3 populations (east, southeast and south) by the different frequency of the subtelocentric chromosome. Progeny tests revealed that segregation of A/A, A/S and S/S types from F₁ hybrids between various chromosome combinations was not significantly different from the theoretical one. However, the number of animals with A/S pair was always slightly higher than the other two types, while those with S/S pair slightly fewer. Local differences of the chromosome polymorphism in Japan were considered due to the result of migration and selection of the rats with S/S chromosome type.Contribution No. 817 from the National Institute of Genetics, Japan. Supported in part by a grant-in-aid from the Ministry of Education of Japan (Scientific Expedition in 1968, and No. 8801 in 1969).     

The Black Rat Rattus rattus in the United Kingdom in 1989

The loss of ground by the Black Rat in the late 1950s continued through the next decade. Since then the number of site records has fluctuated and there has been less constancy in the places recording the presence of the rat. This impermanence of populations together with their small size suggests that introductions are short lived and that the species has only a tenuous foothold in the United Kingdom today. Port records show that rats are still arriving regularly by ship and it is suggested that future developments in climate and trade might further assist entry and make the environment more favourable for the Black Rat.     

Litter stimulus factors in maternal retrieval (Rattus rattus)

Maternal retrieval by rats was compared for sedated and control pups at 2, 5, 10, and 15 days of age. The control animals were retrieved more quickly than the experimentals only on day 5. The results were interpreted as demonstrating that stimuli of the pups determining maternal care have varying effects with age.     

Supernumerary (B-) chromosomes in the Malayan house rat,Rattus rattus diardii (Rodentia,Muridae)

Three widely separated Malayan populations of Black rat, Rattus rattus diardii (Jentink), were found to comprise individuals with supernumerary (or B) chromosomes. The number of supernumeraries varied from 0 to 4. The incidence of B's in the three populations did not differ significantly. There was also no difference between the two sexes.     

Origin of agouti-melanistic polymorphism in Wild Black Rats (Rattus rattus) inferred from Mc1r gene sequences

We examined nucleotide changes that underlie coat color variation in Black Rats (the Rattus rattus species complex), which show polymorphism in dorsal fur color, including either grayish brown (agouti) or black (melanistic) forms. We examined the full coding sequence of a gene known to produce melanism in other vertebrates-melanocortin-1-receptor gene Mc1r (954 bp) -using samples of both R. rattus (with 2n = 38) and its close relative Asian Black Rat (R. tanezumi; 2n = 42). We used 61 specimens from Japan with karyotype-known individuals and four samples from Pakistan. We found 11 allele sequences and constructed a network tree that shows two distinct clusters, with allelic segregation according to karyotype and by inference, representing the two species. We found that a nucleotide substitution from G to A at site 280, producing an amino acid change from glutamic acid to lysine, was associated with the dominant trait of the melanistic form of the coat color in R. rattus. Notably, the derived SNP 280A was found in a single allele, with the ancestral SNP 280G present in seven alleles. By contrast, all three alleles for R. tanezumi retain the ancestral SNP 280G. These results suggest a possible recent origin of melanism in R. rattus.     

Frugivory by introduced black rats (Rattus rattus) promotes dispersal of invasive plant seeds

Oceanic islands have been colonized by numerous non-native and invasive plants and animals. An understanding of the degree to which introduced rats (Rattus spp.) may be spreading or destroying seeds of invasive plants can improve our knowledge of plant-animal interactions, and assist efforts to control invasive species. Feeding trials in which fruits and seeds were offered to wild-caught rats were used to assess the effects of the most common rat, the black rat (R. rattus), on 25 of the most problematic invasive plant species in the Hawaiian Islands. Rats ate pericarps (fruit tissues) and seeds of most species, and the impacts on these plants ranged from potential dispersal of small-seeded (≤1.5 mm length) species via gut passage (e.g., Clidemia hirta, Buddleia asiatica, Ficus microcarpa, Miconia calvescens, Rubus rosifolius) to predation where <15% of the seeds survived (e.g., Bischofia javanica, Casuarina equisetifolia, Prosopis pallida, Setaria palmifolia). Rats consumed proportionally more seed mass of the smaller fruits and seeds than the larger ones, but fruit and seed size did not predict seed survival following rat interactions. Although invasive rat control efforts focus on native species protection, non-native plant species, especially those with small seeds that may pass internally through rats, also deserve rat control in order to help limit the spread of such seeds. Black rats may be facilitating the spread of many of the most problematic invasive plants through frugivory and seed dispersal in Hawaii and in other ecosystems where rats and plants have been introduced.     

Identification of glandular (preputial and clitoral) proteins in house rat (Rattus rattus) involved in pheromonal communication

Proteins (18-20 kDa) belonging to lipocalin family have been reported to act as carriers for ligands binding to pheromones in mouse urine, pig saliva, hamster vaginal fluid and human sweat, that are involved in pheromonal communication. As the preputial gland is a major pheromonal source, the present study was aimed to detect the specific protein bands (around 18-20 kDa) in the preputial and clitoral glands of the house rat, R. rattus. The amount of protein was higher in preputial gland of the male than that of female (clitoral) gland. A 20 kDa protein was noted in male and female glands; however, the intensity of the band was much higher in male than in female. In addition, 70, 60, 35 kDa bands, identified in male preputial gland, were absent in females. The presence of higher concentration of glandular proteins in the male preputial gland suggests that male rats may depend more on these glandular proteins for the maintenance of reproductive and dominance behaviours. The results further suggest that these glandular proteins (20 kDa) may act as a carrier for ligand binding.     

Genetic characterization of black rat (Rattus rattus) of the Canary Islands: origin and colonization

In the Canary Islands two invasive rat species, Rattus rattus and Rattus norvegicus are present, but little is known about the origin and colonization. To this end, a molecular study was performed on R. rattus from the Archipelago and from the nearest continents. Partial cytochrome b gene sequencing offered very low levels of haplotype and nucleotide diversities, with only seven haplotypes identified. All of them belong to the European Lineage I, specifically to the “ship rat” cluster. The haplotype network showed a star-like topology. Haplotype distribution showed a genetic subdivision between eastern and central/western islands, suggesting a double colonization event. This hypothesis is congruent with historical human colonization and it is similar to that proposed for the rodent parasite Hymenolepis diminuta. In addition, a possible role of the Canary Islands as a faunal link with the European and American continents is discussed.     

Salmonella ochiogu: experimental infection of laboratory rats (Rattus rattus)

Oral infection of experimental rats with 10(8) colony forming units of Salmonella ochiogu resulted in clinical salmonellosis in 42 of 98 (43%) rats and a carrier state in 56 of 98 (57%). Infection was characterized by septicaemia, pneumonia and loss of condition. Organisms were shed in faeces on the first day after infection and cultures of most visceral organs revealed good systemic dissemination of the serotype, which was pathogenic to experimental rats.     

Neurohistological observations on the kidney of Rattus rattus rufescens (Indian black rat) as revealed by cholinesterase technique.

The intrinsic innervation of the kidney in Rattus rattus rufescens (Indian black rat) has been studied by cholinesterase technique, under various temperatures, incubation periods and different pH values. The percentage of myelinated nerves was rather high in the medulla region, whereas the non-myelinated nerves dominated in association with the uriniferous tubules and their branches, glomerulus and renal vein in the cortex region. Periarterial AChE-positive ganglia were recorded in the medulla region. The perivenous and periglomerulus plexuses were formed by the non-myelinated nerves and their branches.