Severity of lymphocytic choriomeningitis virus disease in different strains of suckling mice correlates with increasing amounts of endogenous interferon.

A marked difference was observed in the severity of disease in lymphocytic choriomeningitis (LCM) virus-infected suckling BALB/c, Swiss, and C3H mice. BALB/c mice had minimal liver lesions and none died, whereas C3H mice had extensive liver lesions and all mice died. An intermediate pattern was oberved for Swiss mice (36% mortality). Although there was no difference in the titers of LCM virus in the plasma or liver between these three strains of mice, there was a marked difference in the amount of interferon produced and the duration of interferonemia. C3H mice produced more interferon than Swiss mice which produced more interferon than BALB/c mice, indicating a direct correlation between the amount of interferon induced by LCM virus and the extent of disease. Inoculation of a potent anti-mouse interferon globulin markedly reduced the incidence of mortality in virus-infected C3H mice. BALB/c mice were as sensitive to the effects of interferon as C3H mice because daily administration of potent interferon preparations did induce disease in this strain. This ensemble of results supports our contention that endogenous interferon is in large part responsible for the manifestaions of acute LCM virus disease in suckling mice.

Wild mouse RNA tumor viruses. A nongenetically transmitted virus group closely related to exogenous leukemia viruses of laboratory mouse strains.

Type-C RNA viruses isolated from wild mice are causative of naturally occurring neoplasia and neurologic diseases. Biochemical and immunologic characterization of this virus group revealed that amphotropic viruses isolated from wild mice trapped in separate geographical areas are indistinguishable, whereas amphotropic and ecotropic viruses naturally infecting the same animal are env gene variants. Molecular hybridization studies established that neither host range variant is endogenous to the Mus musculus genome, although each demonstrates partial nucleotide sequence homology. Wild mouse type-C viruses exhibited much closer molecular and antigenic relatedness to the exogenous virus subgroup (Friend-, Moloney-, and Rauscher-MuLV) than to prototype endogenous viruses isolated from laboratory mouse strains. The evidence indicates that exogenous mouse type-C viruses have been maintained in nature over a long period of evolution as a separate virus group, causative of tumors in mice by a mechanism solely involving their transmission as infectious agents.

Advances in understanding disease epidemiology and implications for control and eradication of tuberculosis in livestock: the experience from New Zealand.

A deteriorating tuberculosis problem in cattle and deer in New Zealand has been halted and then reversed over the last decade. Mycobacterium bovis infection in both wild and domestic animal populations has been controlled. This has been achieved by applying a multi-faceted science-based programme. Key features of this have been a comprehensive understanding of the epidemiology of tuberculosis in animals, confidence in sampling wild animal populations, effective application of diagnostic tests in cattle and deer, and the ability to map M. bovis genotypes.

O-antigen structural variation: mechanisms and possible roles in animal/plant-microbe interactions.

Current data from bacterial pathogens of animals and from bacterial symbionts of plants support some of the more general proposed functions for lipopolysaccharides (LPS) and underline the importance of LPS structural versatility and adaptability. Most of the structural heterogeneity of LPS molecules is found in the O-antigen polysaccharide. In this review, the role and mechanisms of this striking flexibility in molecular structure of the O-antigen in bacterial pathogens and symbionts are illustrated by some recent findings. The variation in O-antigen that gives rise to an enormous structural diversity of O-antigens lies in the sugar composition and the linkages between monosaccharides. The chemical composition and structure of the O-antigen is strain-specific (interstrain LPS heterogeneity) but can also vary within one bacterial strain (intrastrain LPS heterogeneity). Both LPS heterogeneities can be achieved through variations at different levels. First of all, O-polysaccharides can be modified non-stoichiometrically with sugar moieties, such as glucosyl and fucosyl residues. The addition of non-carbohydrate substituents, i.e. acetyl or methyl groups, to the O-antigen can also occur with regularity, but in most cases these modifications are again non-stoichiometric. Understanding LPS structural variation in bacterial pathogens is important because several studies have indicated that the composition or size of the O-antigen might be a reliable indicator of virulence potential and that these important features often differ within the same bacterial strain. In general, O-antigen modifications seem to play an important role at several (at least two) stages of the infection process, including the colonization (adherence) step and the ability to bypass or overcome host defense mechanisms. There are many reports of modifications of O-antigen in bacterial pathogens, resulting either from altered gene expression, from lysogenic conversion or from lateral gene transfer followed by recombination. In most cases, the mechanisms underlying these changes have not been resolved. However, in recent studies some progress in understanding has been made. Changes in O-antigen structure mediated by lateral gene transfer, O-antigen conversion and phase variation, including fucosylation, glucosylation, acetylation and changes in O-antigen size, will be discussed. In addition to the observed LPS heterogeneity in bacterial pathogens, the structure of LPS is also altered in bacterial symbionts in response to signals from the plant during symbiosis. It appears to be part of a molecular communication between bacterium and host plant. Experiments ex planta suggest that the bacterium in the rhizosphere prepares its LPS for its roles in symbiosis by refining the LPS structure in response to seed and root compounds and the lower pH at the root surface. Moreover, modifications in LPS induced by conditions associated with infection are another indication that specific structures are important. Also during the differentiation from bacterium to bacteroid, the LPS of Rhizobium undergoes changes in the composition of the O-antigen, presumably in response to the change of environment. Recent findings suggest that, during symbiotic bacteroid development, reduced oxygen tension induces structural modifications in LPS that cause a switch from predominantly hydrophilic to predominantly hydrophobic molecular forms. However, the genetic mechanisms by which the LPS epitope changes are regulated remain unclear. Finally, the possible roles of O-antigen variations in symbiosis will be discussed.

Creutzfeldt-Jakob Disease. Possible transmission to humans by consumption of wild animal brains.

Although the natural mode of spread of the agent responsible for Creutzfeldt-Jakob disease is unknown, several reports suggest oral transmission through consumption of contaminated food or brain. This report summarizes four cases of Creutzfeldt-Jakob disease in which a history of eating the brains of wild goat or squirrel was obtained. These cases support the hypothesis of possible acquisition of Creutzfeldt-Jakob disease by ingestion of the agent from a presumptive reservoir in the central nervous system of wild animals.

Trends in antimicrobial resistance of Salmonella isolated from animals, foods of animal origin, and the environment of animal production in Canada, 1994-1997.

The purpose of our study was to determine the occurrence, magnitude, trends, and relationships regarding antibiotic resistance of Salmonella isolated from animals, animal food products, and the environment of animals. We examined 621 strains of 67 different serovars isolated in 1994, 721 strains of 75 different serovars isolated in 1995, 1,219 strains of 83 different serovars isolated in 1996, and 1,336 Salmonella strains of 92 different serovars isolated in 1997, for resistance to 17 antibiotics at one to three different concentrations with the agar dilution method. The overall resistance magnitude regressed from 9.2% in 1994 to 8.1% in 1997. Resistance to streptomycin (30.4% of 3,897 isolates), tetracycline (27.3%), and sulfisoxazole (23.7%) was highest. Resistance to streptomycin, tetracycline, kanamycin, and gentamicin declined during the 4-year period. Notable increases in resistance to ampicillin, chloramphenicol, and neomycin occurred during the 1994-1997 years. None of the isolates was resistant to amikacin. None of the isolates was resistant to ciprofloxacin at 1, 2, and 4 microg/ml. Salmonella bredeney isolates from turkeys showed a decreased sensitivity to ciprofloxacin and were resistant at the low level of 0.125 microg/ml, but none of these isolates was resistant at 1 microg/ml. Resistance to nalidixic acid correlated significantly with decreased sensitivity to ciprofloxacin; 122 of 127 (96%) isolates resistant to nalidixic acid at 32 microg/ml were resistant to ciprofloxacin at 0.125 microg/ml but sensitive at 1 microg/ml. Resistance to S. typhimurium to each of the seven antibiotics ampicillin, chloramphenicol, kanamycin, neomycin, streptomycin, sulfisoxazole, and tetracycline increased persistently during each of the years 1994-1997, but none of the S. typhimurium isolates showed decreased sensitivity to ciprofloxacin. Clinical isolates of Salmonella were twice as frequently resistant to the antimicrobials in the test panel than isolates obtained during surveys. Salmonella isolates from turkeys were more frequently resistant than isolates from pigs, cattle, and chickens.

Antibiotic resistance in bacteria of animal origin: methods in use to monitor resistance in EU countries.

A study on the ongoing monitoring programmes in 13 European countries was made as part of a concerted action funded by the European Commission. Five main reference systems were used in the surveyed countries and three categories of bacteria were monitored, zoonotic agents, indicator bacteria and veterinary pathogens. The five reference systems and an overview of the national monitoring programmes are described. Differences exist and there is a real need for standardisation at the European level. This harmonisation could be set up both for microbiological methods and the epidemiological results derived from common methods. Disk diffusion methods are most widely used and many of the monitored species and control strains are similar in the action's participating countries.

Antibiotic resistance monitoring in bacteria of animal origin: analysis of national monitoring programmes.

Methods of antibiotic resistance monitoring of bacteria from animals in 12 European countries were surveyed in 1998. Most laboratories used disk diffusion methods, usually expressing results qualitatively, although a few also expressed the results either as MICs or zone diameters. The number of antibiotics used ranged from 5 to 37 (mean 15) and the most common antibacterials were streptomycin, gentamicin, neomycin, ampicillin, tetracyclines, chloramphenicol and sulphonamides. Salmonellae were monitored by most centres but few-tested campylobacter regularly. Escherichia coli from a wide range of animal species were tested in nine countries. Enterococci were tested on a limited ad hoc basis in six countries. Staphylococci, streptococci and pasteurellae were also frequently monitored but the number of isolates tested showed wide variation. Overall the presentation of the results differed, but most programmes used disk diffusion, control strains and monitored similar bacteria. Thus, it may be possible to harmonise monitoring programmes within the EU.

Isolation of Leptospira from wild forest animals in Amazonian Brazil.

The role of wild, forest animals as reservoirs of Leptospira was investigated in Pará State, north Brazil. 696 animals were examined by culture of kidney tissue; isolates of serovar ballum were made from the rodent Proechimys sp. and the opossum Didelphis marsupialis; leptospires of the serogroups hebdomadis, grippotyphosa and cynopteri were isolated from the armadillo Dasypus novemcinctus, and as yet untyped leptospires were isolated from Proechimys and the procyonid carnivore Nasua nasua. Antibodies to serovars bataviae, butembo, canicola, castellonis, celledoni, grippotyphosa, panama, icterohaemorrhagiae and wolffi were demonstrated among 222 other animals examined by serological methods.

Rotavirus infection in wild marsupials (Didelphis marsupialis) of the Amazon region.

Rotavirus was detected by enzyme-linked immunosorbent assay in faecal specimens collected from two (1.35%) of 148 marsupials trapped in the Amazon jungle environment. The positive samples were both from the "common opossum", Didelphis marsupialis. No infections were found in the stools of 198 animals belonging to other mammalian species: the latter included small rodents, chiropterans and primates. Electron microscopic examination of one (MA 5928) rotavirus-positive specimen showed a large number of empty particles. However, both rotavirus strains grew when inoculated in MA 104 cells (foetal Rhesus monkey kidney cells) producing clear cytopathogenic effect; indirect immunofluorescence technique of these cells showed a typical granular cytoplasmic fluorescence. The electrophoretic profile of strain MA 5928 showed a high grade of homology with that of SA 11, but also showed minor differences.

Arbovirus isolations from, and serological studies on, wild and domestic vertebrates from Kano Plain, Kenya.

Arbovirus infection and presence of haemagglutination-inhibiting antibodies in small mammals, birds and livestock were examined over a period of five years on the Kano Plain in western Kenya. Eleven isolations were made from mammals and birds. The viruses were identified as Arumowot and Germiston while three different agents could not be shown to be related to 188 African arboviruses. Prevalence of antibodies against arboviruses suspected of occurring in the area was generally low.

Neutralising antibodies to wildebeest-derived malignant catarrhal fever virus in African wildlife.

A total of 2,722 sera collected between 1963 and 1983, from 43 different species of wildlife in 11 African countries was examined for neutralising antibodies against the wildebeest-derived strain of malignant catarrhal fever (MCF) virus. Antibodies were demonstrated in 10 species of Bovidae which included eight species from the sub-family Hippotraginae and one species each from Bovinae and Antilopinae. Neutralising antibodies were also recorded in hippopotamus. It is suggested that the high prevalence of antibodies recorded in sera from waterbuck and reedbuck indicate infection with MCF. However, titres in other species may be due to antigenically related viruses.

Experimental Newcastle disease virus infections in three species of wild birds.

Three species of wild birds--the red-winged blackbird (Agelaius phoeniceus), an African weaver finch (Quelea quelea), and the sandhill crane (Grus canadensis)--were exposed to Newcastle disease virus (NDV) to determine susceptibility and host response. The NDV used were a vaccine strain (LaSota) and a viscerotropic velogenic strain (New York Parrot). Host response was monitored by virus isolation, signs of disease, and serologic response. Both the red-winged blackbirds and the quelea shed little virus and developed low antibody titers. A low mortality in the blackbirds did not appear to be due to ND alone. Vaccinated cranes were well protected against velogenic challenge, whereas unvaccinated cranes shed the velogenic virus from the cloaca for weeks. The ramifications of the low antibody titers produced in birds of two species are discussed, as well as the potential involvement of each species in transmission of the virus.

Pathogenicity for chickens of avian influenza viruses isolated from whistling swans and a black-tailed gull in Japan.

We isolated 24 Hav1 Neq1 and 18 Hav6 Nav3 influenza viruses from such free-living wild waterfowl as whistling swans, black-tailed gulls, and tufted ducks in western Japan in 1980. Two Hav1 Neq1 viruses isolated from a whistling swan and a black-tailed gull and a Hav6 Nav3 virus from a whistling swan were examined for their pathogenicity for chickens. Five-week-old specific-pathogen-free chickens were inoculated with the viruses intratracheally or intraperitoneally. Virus was recovered successfully from all the organs, including the brain, despite the absence of signs of disease. The intracerebral pathogenicity index scores obtained for the Hav1 Neq1 viruses were 0.43 and 0.87; the score for the Hav6 Nav3 virus was 0.43. No virus produced plaques in cultivated chick embryo fibroblast cells in the absence of trypsin.

Experimental transmission of Chlamydia psittaci to turkeys from wild birds.

Wild birds were inoculated with Chlamydia psittaci to determine species that could be potential hosts and vectors in transmitting the agent to domestic turkeys. Infection occurred in turkeys exposed to starlings (Sturnus vulgaris), common grackles (Quiscalus quiscula), brown-headed cowbirds (Molothrus ater), and Inca doves (Cardafella inca). Mourning doves (Zenaidura macroura) shed the agent sparingly, but turkeys exposed to them did not become infected, These findings and knowledge of the habits of these various species are discussed. It was concluded that the Inca dove should be considered a potential source of turkey chlamydiosis in Texas. The species studied and other species not studied should be included in serologic surveys and surveillance studies attempting isolation of chlamydiae.

Influenza virus surveillance in waterfowl in Pennsylvania after the H5N2 avian outbreak.

During the latter stages of the lethal H5N2 influenza eradication program in domestic poultry in Pennsylvania in 1983-84, surveillance of waterfowl was done to determine if these birds harbored influenza viruses that might subsequently appear in poultry. From late June to November 1984, 182 hemagglutinating viruses were isolated from 2043 wild birds, primarily ducks, in the same geographical area as the earlier lethal H5N2 avian influenza outbreak. The virus isolates from waterfowl included paramyxoviruses (PMV-1, -4, and -6) and influenza viruses of 13 antigenic combinations. There was only one H5N2 isolate from a duck. Although this virus was antigenically related to the lethal H5N2 virus, genetic and antigenic analysis indicated that it could be discriminated from the virulent family of H5N2 viruses, and it did not originate from chickens. Many of the influenza viruses obtained from wild ducks were capable of replicating in chickens after experimental inoculation but did not cause disease. These studies show that many influenza A virus strains circulating in waterfowl in the vicinity of domestic poultry in Pennsylvania did not originate from domestic poultry. These influenza viruses from wild ducks were capable of infecting poultry; however, transmission of these viruses to poultry apparently was avoided by good husbandry and control measures.

Influenza viruses related to A/Shearwater/Australia/1/72 (Hav6 Nav5) in domestic and feral birds.

One influenza-A virus isolated from domestic turkeys in California in 1964 and two from migrating ducks in Delaware in 1973 were classified as Hav6 and Nav5, i.e., antigenically the same as A/Shearwater/Australia/1/72. The detection of antigenically related viruses in three different species over a ten-year period suggests a broad host range, contributing to continued circulation in nature. The turkeys suffered severe respiratory disease although infected migratory birds have not revealed signs of disease. These results suggest migratory birds, which travel over vast areas, as a source of influenza viruses infecting domestic species.

Isolation of a Mycoplasma sp. from three buzzards (Buteo spp.).

Mycoplasma spp. were isolated from the respiratory tissues of three buzzards. Bird I, a rough-legged buzzard (Buteo lagopus), showed airsacculitis, catarrhal-fibrinous pneumonia, and catarrhal tracheitis. Bird II, a common buzzard (Buteo buteo), revealed mycotic airsacculitis, bronchitis and pneumonia. Bird III was a healthy rough-legged buzzard. All isolates metabolized glucose but not arginine and were serologically identical by immunofluorescence and growth-inhibition tests. No serological cross-reactions were seen with several known Mycoplasma species.

Serovar identification of leptospires of the Australis serogroup isolated from free-living and domestic species in the United Kingdom.

Eighteen isolates from the Australis serogroup from free-living and domestic animals were identified using the cross agglutination absorption test. Serovar muenchen was found only in England and Wales in wood mice, short tailed and bank voles, a grey squirrel and a pig. Serovar bratislava was found in hedgehogs in England, Wales and Northern Ireland and also in a brown rat from Northern Ireland. Serovar bratislava was isolated from sheep in both England and Northern Ireland and from horses in Northern Ireland. The distribution of these serovars in relation to possible maintenance hosts is discussed.

Experimental infection of Columba livia with paramyxovirus Yucaipa.

The town pigeons (Columba livia) were inoculated intranasally with a Yucaipa-like virus (PLOC/Senegal/273/77). They were then surveyed for virus production in the cloaca over a 10 day period. The virus could be isolated at two, three and four days after inoculation.