Isolation of members of the Haemophilus-Pasteurella-Actinobacillus group from feral rodents

46 feral rodents, including a common vole (Microtus arvalis), house mice (Mus musculus), muskrats (ondatra zibetica), house rats (Rattus rattus) and brown rats (R. norvegicus) were examined for bacteria of the Haemophilus-Pasteurella-Actinobacillus group. Haemophilus spp. (only M. musculus examined) were not obtained. All animal species were found contaminated by P. pneumotropica and/or Actinobacillus spp. Almost all M. musculus (96%) and most Rattus spp. (76%) were contaminated by P. pneumotropica and/or Actinobacillus spp. These bacteria were obtained most frequently from the upper respiratory tract, to a lesser extent from the lung and rarely from caecal contents. It is concluded that feral rodents might constitute an important source of contamination of laboratory rodents by members of the HPA-group.     

Cross-species transmission of Giardia spp.: inoculation of beavers and muskrats with cysts of human, beaver, mouse, and muskrat origin

Giardia cysts isolated from humans, beavers, mice, and muskrats were tested in cross-species transmission experiments for their ability to infect either beavers or muskrats. Giardia cysts, derived from multiple symptomatic human donors and used for inoculation of beavers or muskrats, were shown to be viable by incorporation of fluorogenic dyes, excystation, and their ability to produce infections in the Mongolian gerbil model. Inoculation of beavers with 5 x 10(5) Giardia lamblia cysts resulted in the infection of 75% of the animals (n = 8), as judged by the presence of fecal cysts or intestinal trophozoites at necropsy. The mean prepatent period was 13.1 days. An infective dose experiment, using 5 x 10(1) to 5 x 10(5) viable G. lamblia cysts collected by fluorescence-activated cell sorting, demonstrated that doses of between, less than 50, and less than 500 viable cysts were required to produce infection in beavers. Scanning electron microscopy of beaver small intestine revealed that attachment of G. lamblia trophozoites produced lesions in the microvillous border. Inoculation of muskrats with G. lamblia cysts produced infections when the dose of cysts was equal to or greater than 1.25 x 10(5). The inoculation of beavers with Giardia ondatrae or Giardia muris cysts did not produce any infection; however, the administration to muskrats of Giardia cysts of beaver origin resulted in the infection of 62% of the animals (n = 8), with a prepatent period of 5 days. Our results demonstrated that beavers and muskrats could be infected with Giardia cysts derived from humans, but only by using large numbers of cysts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cross-species transmission of Giardia spp.: inoculation of beavers and muskrats with cysts of human, beaver, mouse, and muskrat origin.

Giardia cysts isolated from humans, beavers, mice, and muskrats were tested in cross-species transmission experiments for their ability to infect either beavers or muskrats. Giardia cysts, derived from multiple symptomatic human donors and used for inoculation of beavers or muskrats, were shown to be viable by incorporation of fluorogenic dyes, excystation, and their ability to produce infections in the Mongolian gerbil model. Inoculation of beavers with 5 x 10(5) Giardia lamblia cysts resulted in the infection of 75% of the animals (n = 8), as judged by the presence of fecal cysts or intestinal trophozoites at necropsy. The mean prepatent period was 13.1 days. An infective dose experiment, using 5 x 10(1) to 5 x 10(5) viable G. lamblia cysts collected by fluorescence-activated cell sorting, demonstrated that doses of between, less than 50, and less than 500 viable cysts were required to produce infection in beavers. Scanning electron microscopy of beaver small intestine revealed that attachment of G. lamblia trophozoites produced lesions in the microvillous border. Inoculation of muskrats with G. lamblia cysts produced infections when the dose of cysts was equal to or greater than 1.25 x 10(5). The inoculation of beavers with Giardia ondatrae or Giardia muris cysts did not produce any infection; however, the administration to muskrats of Giardia cysts of beaver origin resulted in the infection of 62% of the animals (n = 8), with a prepatent period of 5 days. Our results demonstrated that beavers and muskrats could be infected with Giardia cysts derived from humans, but only by using large numbers of cysts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inapparent Streptococcus pneumoniae type 35 infections in commercial rats and mice

Streptococcus pneumoniae was isolated from specific-pathogen-free rodents in two rooms at a commercial breeding facility during vendor surveillance testing. In a survey of 274 animals from the two rooms over a period of 7 months, capsular serotype 35 S. pneumoniae was isolated from the upper respiratory tracts of 11% (9 of 82) of C57BL/6 mice in room A and 14% (10 of 72) of F344 rats in room B, but not from WKY rats, BALB/c mice or DBA/2 mice from room A. In both C57BL/6 mice and F344 rats, older rodents had higher colonization frequencies. Nasal lavage cultures gave the best results in identifying colonized rodents. No clinical illness or microscopic lesions were associated with pneumococcal colonization in rats or mice, and no other evidence of potential pathogen infection was found except for positive serologic tests for mouse rotavirus in mice. This is the first report of natural pneumococcal infection in mice, and the first report of type 35 S. pneumoniae infection in rodents. The findings support an earlier observation that pneumococcal infections in rat colonies tend to be monotypic and suggest that the same may be true in mice.     

Prevalence of Giardia spp. in beaver and muskrat populations in northeastern states and Minnesota: detection of intestinal trophozoites at necropsy provides greater sensitivity than detection of cysts in fecal samples.

Surveys of the prevalence of the intestinal protozoan Giardia spp. in animal populations have relied almost exclusively on the detection of cysts in fecal samples. We have determined the prevalence of Giardia spp. in beaver and muskrat populations in four northeastern states and Minnesota by using both the detection of trophozoites in mucosal scrapings from live-trapped animals at necropsy and the detection of cysts in fecal samples collected from kill-trapped animals. In muskrats the prevalence of Giardia infection was 36.6% by cyst detection in fecal samples (n = 790) from kill-trapped animals and 95.9% in live-trapped muskrats when the intestinal contents were analyzed for the presence of trophozoites (n = 219). Similarly, in beavers, Giardia infection was 9.2% by cyst detection in fecal samples (n = 662) from kill-trapped beavers and 13.7% in live-trapped animals examined for the presence of intestinal trophozoites (n = 302). The detection of trophozoites in mucosal scrapings from live-trapped animals consistently yielded a significantly higher prevalence for both muskrats and beavers than did the method based on detection of cysts in the fecal samples. The prevalence of Giardia infection in juvenile and adult live-trapped muskrats was similar (92.5 and 94.4%, respectively), but the prevalence in juvenile live-trapped beavers (23.2%) was significantly greater than that seen in the adult animals (12.6%). No difference in Giardia prevalence on the basis of sex was seen in either animal species. Regional variation, often statistically significant, was seen in the prevalence of Giardia in beavers in the northeastern states and Minnesota, but was not detected for muskrats.     

Prevalence of Giardia spp. in beaver and muskrat populations in northeastern states and Minnesota: detection of intestinal trophozoites at necropsy provides greater sensitivity than detection of cysts in fecal samples

Surveys of the prevalence of the intestinal protozoan Giardia spp. in animal populations have relied almost exclusively on the detection of cysts in fecal samples. We have determined the prevalence of Giardia spp. in beaver and muskrat populations in four northeastern states and Minnesota by using both the detection of trophozoites in mucosal scrapings from live-trapped animals at necropsy and the detection of cysts in fecal samples collected from kill-trapped animals. In muskrats the prevalence of Giardia infection was 36.6% by cyst detection in fecal samples (n = 790) from kill-trapped animals and 95.9% in live-trapped muskrats when the intestinal contents were analyzed for the presence of trophozoites (n = 219). Similarly, in beavers, Giardia infection was 9.2% by cyst detection in fecal samples (n = 662) from kill-trapped beavers and 13.7% in live-trapped animals examined for the presence of intestinal trophozoites (n = 302). The detection of trophozoites in mucosal scrapings from live-trapped animals consistently yielded a significantly higher prevalence for both muskrats and beavers than did the method based on detection of cysts in the fecal samples. The prevalence of Giardia infection in juvenile and adult live-trapped muskrats was similar (92.5 and 94.4%, respectively), but the prevalence in juvenile live-trapped beavers (23.2%) was significantly greater than that seen in the adult animals (12.6%). No difference in Giardia prevalence on the basis of sex was seen in either animal species. Regional variation, often statistically significant, was seen in the prevalence of Giardia in beavers in the northeastern states and Minnesota, but was not detected for muskrats.     

The eradication of muskrats and coypus from Britain

Introduced vertebrates can cause massive environmental damage but most attempts to remove feral populations have failed. This paper discusses the eradication campaigns against feral muskrats, Ondatra Zibethicus and coypus, Myocastor coypus in Britain. Both specks were introduced in the 1920s to be farmed for pelts and feral populations became established following escapes. The risk of environmental damage by muskrats was well known from Europe and;in eradication campaign started promptly in 1932 making use of overseas expertise and a control strategy designed by pest control specialists. The campaign was brought to a successful conclusion in 1939 when at least 4388 muskrats had been killed.
In the 1930s, few believed that coypus would cause significant environment damage and early trapping efforts were inadequate. An early campaign achieved only limited success partly because of the lack of biological information. The eradication campaign which started in 1981, was based on a long tem study of population ecology. The effect of trapping and cold weather was quantified and detailed population simulations were used to plan the numbers of trappers, the time needed for eradication arid thus the likely cost of the campaign. An incentive bonus scheme was designed to overcome the problem that trappers would be reluctant to work themselves out of a job. Trapper deployment was planned using capture/trapping effort ratios and progress was checked by Ministry of Agriculture field staff.
The muskrat campaigns succeeded because technical information to help plan the work was available and because action was taken quickly. Where an introduced population is well established, as with coypus in Britain, a closely integrated programme involving applied population ecology and a well-planned control organization may he essential for succesful removal.     

Muskrats as carriers of pathogenic leptospires in The Netherlands

Leptospires were isolated from 24 of 327 (7%) muskrats (Ondatra zibethicus) caught in The Netherlands. All isolates were identified asLeptospira interrogans. One isolate was typed as serovarcopenhageni in the Icterohaemorrhagiae serogroup, one as serovarlora in the Australis serogroup. Twenty-one isolates showed a close relationship with serovarsgrippotyphosa, valbuzzi, muelleri andratnapura from the Grippotyphosa serogroup. One isolate was lost. Sera from 196 muskrats were examined by the microscopic agglutination test. Forty-five (23%) sera reacted positively (titers1: 160), 42 (21%) of these 45 sera to Grippotyphosa and 3 (2%) to Sejroe serogroup antigens. This is the first report of serological and cultural evidence of leptospira infection in muskrats in The Netherlands.Abbreviations CAAT cross agglutination absorption test - 5-FU 5-fluorouracil - MAT microscopic agglutination test - MCA monoclonal antibodies - PBS phosphate buffered saline - REA restriction endonuclease analysis - SDS sodium dodecyl sulphate     

Serotyping of Vibrio anguillarum

A serotyping scheme based on the detection of O antigens by slide agglutination in fish-pathogenic strains of Vibrio anguillarum is presented. Over a period of 5 years 270 Vibrio strains from feral and cultured fish, 189 strains from the environment, and 36 strains from invertebrates were collected. The strains were divided into 10 distinct serotypes (O1 through O10). More than 90% of the fish-pathogenic strains, but only 40% of the environmental strains, were typable; 71% of the strains isolated from cultured rainbow trout were serotype O1, whereas 78% of the strains isolated from feral fish were serotype O2. No dominating environmental serotype was found. A serotyping system for V. anguillarum is proposed. A total of 90 strains received from culture collections and laboratories in different countries were typed according to the present system.     

Serotyping of Vibrio anguillarum.

A serotyping scheme based on the detection of O antigens by slide agglutination in fish-pathogenic strains of Vibrio anguillarum is presented. Over a period of 5 years 270 Vibrio strains from feral and cultured fish, 189 strains from the environment, and 36 strains from invertebrates were collected. The strains were divided into 10 distinct serotypes (O1 through O10). More than 90% of the fish-pathogenic strains, but only 40% of the environmental strains, were typable; 71% of the strains isolated from cultured rainbow trout were serotype O1, whereas 78% of the strains isolated from feral fish were serotype O2. No dominating environmental serotype was found. A serotyping system for V. anguillarum is proposed. A total of 90 strains received from culture collections and laboratories in different countries were typed according to the present system.     

High prevalence of toxoplasmosis in cats from Egypt: isolation of viable Toxoplasma gondii, tissue distribution, and isolate designation

Cats are important in the epidemiology of Toxoplasma gondii because they are the only hosts that excrete environmentally resistant oocysts in feces. In the present study, 158 feral cats from Giza, Egypt, were examined for T. gondii infection. Antibodies to T. gondii were found in 97.4% with the modified agglutination test. Viable T. gondii was isolated from tissues (brain, heart, tongue) of 115 of 137 cats by bioassay in mice. These isolates were designated TgCatEg 1-115; none of these isolates was virulent to out-bred Swiss Webster mice. Of the 112 seropositive cats whose tissues were bioassayed individually, T. gondii was isolated from the hearts of 83 (74.1%), tongues of 53 (47.3%), and brains of 36 (32.1%). Toxoplasma gondii oocysts were not detected in rectal contents of any of the 158 cats, probably related to high seropositivity (chronic infection) of cats surveyed. The high prevalence of T. gondii in feral cats in Egypt reported here indicates a high environmental contamination with oocysts.     

Heat increment of feeding and its thermoregulatory benefit in the muskrat (Ondatra zibethicus)

The calorigenic effect of feeding and its potential benefit in defraying thermoregulatory costs and attenuating immersion hypothermia of adult muskrats were investigated. A single session of feeding on aquatic vegetation was sufficient to raise the metabolic rate of muskrats for a period of at least 5 h. The peak postprandial rate of oxygen consumption averaged 1.42 times the level established for fasted animals, and the heat increment of feeding accounted for about 40% of the metabolizable energy intake of muskrats. There was no evidence of a postprandial rise in oxygen consumption of muskrats that entered water at 18–19°C after feeding. In aquatic trials, average and minimum steady-state oxygen consumption rates of fed muskrats were similar to, or even lower than values recorded from fasted animals, implying substitution of heat increment of feeding for thermoregulatory heat production. Our data did not support the hypothesis that heat increment of feeding retards body cooling in water. Net body temperature decline in water was actually higher in fed animals than in fasted controls. However, since previously fed muskrats also entered water at an elevated body temperature, the final body temperature (at 30 min immersion) was similar in all groups. These findings suggest that metabolic heat generated incidental to preimmersion feeding could provide a thermoregulatory benefit to muskrats by reducing the need for active thermogenesis in water.     

Antibodies to vesicular stomatitis virus in populations of feral swine in the United States

From 1979 to 1985, 941 feral swine (Sus scrofa) from 53 locations in 15 states were serologically tested for antibodies to vesicular stomatitis virus (VSV). Antibodies to New Jersey serotype VSV were present in 75 swine from five locations in Arkansas, Florida, Georgia, and Louisiana. Within these populations, antibody prevalences ranged from 10 to 100%. No antibodies to Indiana serotype were detected.     

Isolation and Genetic Characterization of Toxoplasma gondii from Black Bears (Ursus americanus), Bobcats (Lynx rufus), and Feral Cats (Felis catus) from Pennsylvania

Toxoplasma gondii infects virtually all warm‐blooded hosts worldwide. Recently, attention has been focused on the genetic diversity of the parasite to explain its pathogenicity in different hosts. It has been hypothesized that interaction between feral and domestic cycles of T. gondii may increase unusual genotypes in domestic cats and facilitate transmission of potentially more pathogenic genotypes to humans, domestic animals, and wildlife. In the present study, we tested black bear (Ursus americanus), bobcat (Lynx rufus), and feral cat (Felis catus) from the state of Pennsylvania for T. gondii infection. Antibodies to T. gondii were found in 32 (84.2%) of 38 bears, both bobcats, and 2 of 3 feral cats tested by the modified agglutination test (cut off titer 1:25). Hearts from seropositive animals were bioassayed in mice, and viable T. gondii was isolated from 3 of 32 bears, 2 of 2 bobcats, and 2 of 3 feral cats. DNA isolated from culture‐derived tachyzoites of these isolates was characterized using multilocus PCR‐RFLP markers. Three genotypes were revealed, including ToxoDB PCR‐RFLP genotype #1 or #3 (Type II, 1 isolate), #5 (Type 12, 3 isolates), and #216 (3 isolates), adding to the evidence of genetic diversity of T. gondii in wildlife in Pennsylvania. Pathogenicity of 3 T. gondii isolates (all #216, 1 from bear, and 2 from feral cat) was determined in outbred Swiss Webster mice; all three were virulent causing 100% mortality. Results indicated that highly mouse pathogenic strains of T. gondii are circulating in wildlife, and these strains may pose risk to infect human through consuming of game meat.     

Passive immunity modulates genetic reassortment between rotaviruses in mixedly infected mice.

Genetic reassortment between simian rotavirus SA11 and rhesus rotavirus (RRV) occurs with high frequency following mixed infection of nonimmune suckling mice (J. L. Gombold and R. F. Ramig, J. Virol. 57:110-116, 1986). We examined the effects of passively acquired homotypic or heterotypic immunity on reassortment in vivo. Passively immune suckling mice obtained from dams immune to either serotype 3 simian rotavirus (SA11) or serotype 6 bovine rotavirus (NCDV) were infected orally with either SA11 or RRV or a mixture of SA11 and RRV (both serotype 3 viruses). At various times postinfection, signs of disease were noted and the intestines of individual mice were removed and homogenized for titration of infectious virus and isolation of progeny plaques. Electrophoresis of genomic RNA was used to identify reassortants among the viral progeny isolated from infected animals. No reassortants (less than 0.45%) were detected among 224 clones examined from mixedly infected, homotypically immune mice. Twenty-nine reassortants (10.66%) were identified among 272 progeny clones from mixedly infected, heterotypically immune mice. Thus, reassortment was reduced more than 50-fold by homotypic immunity and approximately threefold by heterotypic immunity compared with prior data obtained from mixed infections of nonimmune mice. In addition, reassortment between SA11 and RRV in nonimmune mice was shown to be dependent on the virus dose. Taken together, these results suggest that immune responses may modulate the frequency of reassortment by reducing the effective multiplicity of infection (by neutralization or other immune mechanisms), thereby preventing efficient mixed infection of enterocytes.     

Horizontal transmission of murine retroviruses.

Both a feral mouse ecotropic virus (WM-E) and Friend ecotropic virus (F-MuLV) were transmitted horizontally among adult mice. Infection resulted in the production of antiviral antibody in the recipients, with no evidence of viremia or clinical disease. However, persistent low-level virus replication was detectable in the spleens of these mice as long as 8 months after initial infection. External secretions, including saliva, semen, and uterine secretions from viremic mice contained high concentrations of infectious virus. Nevertheless, transmission occurred only from viremic males to either males or females. Male-to-male transmission appeared to occur by parenteral inoculation of infectious saliva during fighting behavior. Evidence is presented that infection of females was by the venereal route. Of four mouse strains examined, NFS/N, IRW, and C57L females were all susceptible to venereal infection, whereas AKR mice were not. Since AKR mice are susceptible to infection by WM-E administered parenterally, this resistance appeared to be mediated by local viral interference due to the high-level expression of endogenous Akv gp70 within the female reproductive tract. Although both WM-E and F-MuLV were transmitted from viremic males to females, infection by WM-E was significantly more efficient than that by F-MuLV. This difference correlated with a distinct difference in cellular tropism of WM-E and F-MuLV within the epididymis of viremic males. F-MuLV gp70 was expressed only within stromal elements, whereas WM-E gp70 was seen largely within the epithelial lining cells and luminal contents of the duct. No evidence of virus expression within germ cells was observed. The possible influence of virus expression by epithelial cells of the female reproductive tract on infection of embryos is discussed.     

Distribution of the flagellate Hexamita salmonis Moore, 1922 and the microsporidian Loma salmonae Putz, Hoffman and Dunbar, 1965 in brown trout, Salmo trutta L., and rainbow trout, Salmo gairdneri Richardson, in the River Itchen (U.K.) and three of its fish farms

The occurrence of Hexamita salmonis Moore, 1922 and Loma salmonae Putz, Hoffman and Dunbar, 1965 was investigated at 10 sites on the R. Itchen (five for brown trout only, three for rainbow trout only, and two for both brown trout and rainbow trout) and at three of its nine fish farms (two for rainbow trout, one for brown trout). Hexamita salmonis was recorded in brown trout from three river sites and the farm, and in rainbow trout from both farms and four river sites. Prevalence of Hexamita salmonis in farmed rainbow trout was higher than in farmed brown trout and was consistent with the former species being more susceptible to infection. H. salmonis was at significantly higher prevalence in rainbow trout from farm no. 5 than farm no. 2 for three size classes of fish. In wild brown trout and feral rainbow trout, the highest prevalences of H. salmonis were recorded at sites in the vicinity of farm no. 2. This distribution was consistent with an area of naturally high infection levels, and with infected fish unintentionally released from farm no. 2 serving as a source of infection, the infection subsequently becoming established in the river fish. Loma salmonae was recorded in wild brown trout and in rainbow trout from both farms. This appears to be the first recording of this parasite from British salmonids and also the first recording of the parasite from brown trout. The distribution of the parasite (particularly the prevalence being higher at farm no. 2 than farm no. 5) was consistent with it being introduced into the R. Itchen via rainbow trout from farm no. 2 (and probably no. 3) much of whose stock derived from imported Californian 'Shasta' rainbow trout.     

Detection of Streptobacillus spp. in feral rats by specific polymerase chain reaction

Streptobacillus moniliformis is an etiological agent of rat-bite fever and Haverhill fever in human infection. As the currently available methods for identifying the causative bacteria are not satisfactory, we attempted to establish them by PCR using newly designed primers for the 16S rRNA gene of S. moniliformis. We then determined the prevalence of Streptobacillus spp. in two species of feral rats that inhabit an urban region in Japan, because information on the prevalence of the bacteria in feral rats is obscure. The use of PCR with newly designed primers showed that an extremely high proportion of R. norvegicus harbored the bacteria (61/66, 92%), whereas the prevalence was only 58% in R. rattus (30/52). The nucleotide sequence analysis of the 16S rRNA gene of Streptobacillus spp. isolated from oral swabs of feral rats showed at least two different types of bacteria among isolates from R. norvegicus and R. rattus.     

Oxygen supply of the brain cortex in acute nitrite hypoxia in rodents with different ecological specialization

Microhemodynamics and oxygen tension (pO₂) in the brain cortex tissues as well as the heart rate were studied in rodents with different ecological specialization during hypoxia produced by subcutaneous injection of sodium nitrite (3 mg/100 g body mass). It was shown that the blood flow in animals with low (rats) and high (muskrats) resistance to hypoxia decreased by the 30th min of the nitrite action, with its subsequent restoration to 85% and 83% of the initial level by the 60th min. The interspecies difference consisted in an increase of the brain blood flow (by 24%) in muskrats and a decrease (by 33%) in rats 15 min after the injection. In rats, simultaneously with the blood-flow dynamics, a pO₂ increase was observed in some brain cortex microareas, while in others—a pO₂ decrease 15 min after the NaNO₂ injection: meanwhile, in muskrats, at this time period a significant pO₂ decrease was observed on the background of a blood flow increase. In both animal species, the pO₂ minimal value was reached by the 45th min, while restoration almost to the initial levels—by the 60th min of the nitrite action. Changes in the rats, synchronous and unidirectional with the heart rate frequency, of the brain blood-flow, as well as tachycardia developing throughout the whole experiment in rats allow suggesting that restoration of the oxygen regime in the brain cortex microareas is provided by activation of systemic mechanisms of regulation of circulation.     

Serological surveys of Corynebacterium kutscheri infection in mice and rats

Serological surveys of mice and rats naturally infected with Corynebacterium kutscheri were performed by examining serum samples collected from breeder and laboratory colonies between 1981 and 1983. Among 756 mice from 73 conventional colonies, only 4 animals (0.5%) from 3 colonies (4.1%) developed C. kutscheri antibody of 1:40 to 1:2, 560 titers. Three of them suffered from abscess caused by the organism. Regarding a titer of 1:40 or higher as reliably positive, 87 (13.0%) of 669 conventional rats or 20 (32.8%) of 61 colonies were found to be infected with the organism. The antibodies were detected in both types of animals older than 6 months of age. No lesions caused by C. kutscheri were found in almost all the rats examined. Germ-free and SPF mice and rats were all negative for antibody at 1:5 serum dilution.