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PubMed1997

Therapeutic antibiotics in animal feeds and antibiotic resistance.

Recent statutory changes involving animal drugs are expected to facilitate the therapeutic use of antibiotics in animal feeds in the United States of America. The use of antibiotics in animal feeds is controversial due to the potential development of resistant bacterial pathogens in food-producing animals which are exposed to the antibiotics and the resultant public health risk. Zoonotic micro-organisms can be transmitted to humans through contact with animal populations, either directly or through the consumption of contaminated food. Recommendations to address the public health concerns include the strengthening of professional education in the areas of infectious diseases and the appropriate selection and use of antimicrobial agents, the development of a comprehensive food safety education programme for food-animal veterinarians and animal producers, and the development of surveillance programmes to monitor antimicrobial resistance among zoonotic pathogens. Early identification of emerging resistance can facilitate a timely and appropriate public health response.

Animal Feed↗
PubMed2004

Blastocystis in humans and animals: new insights using modern methodologies.

Among the waterborne protozoan parasites of medical and veterinary importance, Blastocystis is perhaps one of the less well-understood. However, in recent years, there has been a surge of interest in the organism, fueled in part by the possible association of Blastocystis infection with intestinal disorders, and its unusual taxonomic affiliations. Although there is information on the parasite's morphology, taxonomy and mode of transmission, its pathogenicity, life cycle, and function of certain organelles continue to baffle investigators. The clinical relevance of Blastocystis will be better answered once an animal model is found. Blastocystis infections have a worldwide distribution but prevalence is highest in areas with poor hygiene and deficient sanitation services and facilities. Application of modern molecular tools has advanced knowledge of the organism's genetic diversity, taxonomy and zoonotic potential.

Animals↗
PubMed2002

Detection and subtyping of swine influenza H1N1, H1N2 and H3N2 viruses in clinical samples using two multiplex RT-PCR assays.

A total of 360 type A swine influenza virus-positive samples including cell culture isolates, nasal swabs or lung tissues along with 30 virus-negative samples were tested for the detection and subtyping of H1N1, H1N2 or H3N2 by two multiplex reverse transcription (RT)-PCR assays. The positive samples had been collected between 1999 and 2001 from pigs with respiratory diseases, and type A influenza virus was isolated and subtyped by hemagglutination inhibition (HI) test at the Minnesota Veterinary Diagnostic Laboratory (MVDL). Two multiplex RT-PCR assays specific for H1 and H3, and N1 and N2 were developed. RT-PCR products with unique sizes characteristic of each subtype of influenza A virus were sequenced, and the sequences were demonstrated to be specific for H1N1, H1N2 or H3N2. Genomic RNAs or DNAs from 12 common swine pathogens other than type A influenza viruses were not amplified when the PCR assays were performed with these primer sets. Positive amplification reaction could be visualized with RNA extracted from up to 10(-5) dilution of each reference virus with original infectivity titer of 10(5) TCID(50)/ml. Of the 360 samples tested, swine influenza virus H1N1, H1N2 and H3N2 were identified in 200, 13 and 139 samples, respectively. The remaining eight samples were positive for both H1N1 and H3N2 viruses. The results of multiplex RT-PCR were 100% in agreement with those of virus isolation. These results demonstrate the usefulness of multiplex RT-PCR for detection and identification of influenza A virus subtypes. The results also indicate an increased occurrence of H1N2 in US swine population.

Animals↗
PubMed2005

Application of nox-restriction fragment length polymorphism for the differentiation of Brachyspira intestinal spirochetes isolated from pigs and poultry in Australia.

Sixty-nine intestinal spirochetes isolated from pigs and poultry in eastern Australia were selected to evaluate the effectiveness of a species-specific PCR-based restriction fragment length polymorphism (RFLP) analysis of the Brachyspira nox gene. For comparative purposes, all isolates were subjected to species-specific PCRs for the pathogenic species Brachyspira hyodysenteriae and Brachyspira pilosicoli, and selected isolates were examined further by sequence analysis of the nox and 16S ribosomal RNA genes. Modifications to the original nox-RFLP method included direct inoculation of bacterial cells into the amplification mixture and purification of the PCR product, which further optimized the nox-RFLP for use in a veterinary diagnostic laboratory, producing sufficient product for both species identification and future comparisons. Although some novel profiles that prevented definitive identification were observed, the nox-RFLP method successfully classified 45 of 51 (88%) porcine and 15 of 18 (83%) avian isolates into 5 of the 6 recognized species of Brachyspira. This protocol represents a significant improvement over conventional methods currently used in veterinary diagnostic laboratories for rapid specific identification of Brachyspira spp. isolated from both pigs and poultry.

Animals↗
PubMed2000

An isolated epizootic of hemorrhagic-like fever in cats caused by a novel and highly virulent strain of feline calicivirus.

An isolated epizootic of a highly fatal feline calicivirus (FCV) infection, manifested in its severest form by a systemic hemorrhagic-like fever, occurred over a 1-month period among six cats owned by two different employees and a client of a private veterinary practice. The infection may have started with an unowned shelter kitten that was hospitalized during this same period for a severe atypical upper respiratory infection. The causative agent was isolated from blood and nasal swabs from two cats; the electron microscopic appearance was typical for FCV and capsid gene sequencing showed it to be genetically similar to other less pathogenic field strains. An identical disease syndrome was recreated in laboratory cats through oral inoculation with tissue culture grown virus. During the course of transmission studies in experimental cats, the agent was inadvertently spread by caretakers to an adjoining room containing a group of four normal adult cats. One of the four older cats was found dead and a second was moribund within 48-72h in spite of symptomatic treatment; lesions in these animals were similar to those of the field cats but with the added feature of severe pancreatitis. The mortality in field cats, deliberately infected laboratory cats, and inadvertently infected laboratory cats ranged from 33-50%. This new isolate of calicivirus, named FCV-Ari, was neutralized at negligible to low titer by antiserum against the universal FCV-F9 vaccine strain. Cats orally immunized with FCV-F9, and then challenge-exposed shortly thereafter with FCV-Ari, developed a milder self-limiting form of disease, indicating partial protection. However, all of the field cats, including the three that died, had been previously immunized with parenteral FCV-F9 vaccine. FCV-Ari caused a disease that was reminiscent of Rabbit Hemorrhagic Disease, a highly fatal calicivirus infection of older rabbits.

Animals↗
PubMed1978

[Results of veterinary tumor research and their significance for practice].

Enzootic bovine leucosis and Marek's disease of fowl are the most important tumour diseases of farm animals, with the greatest repercussions on the national economy, today. Experimental findings obtained from either disease in recent years are reported in this paper, and an assessment is made of their importance to practice. In the context of enzootic bovine leucosis, particular reference is made to those findings which helped to establish the presence of virus infection, results by which the pathogen could be characterised, and to studies undertaken with the view to devising methods for virologico-serological diagnosis. In the context of Marek's disease, reference is made to virological, epizootiological, and diagnostic aspects, however, with emphasis being laid on possibilities for immunisation and, in that connection, on known fundamental concepts for successful immunoprophylaxis against that tumour disease.

Animals↗
PubMedDate not supplied

The challenges of emerging infectious diseases. Development and spread of multiply-resistant bacterial pathogens.

Resistance is an emerging problem in human medicine and the effects of resistance are being noted on an ever-increasing scale. Whether it is treatment of nosocomial bacteremia in New York City or community-acquired dysentery in Central Africa, multiresistant organisms are diminishing our ability to control the spread of infectious diseases. Clearly, the rate at which resistant organisms develop is not solely a function of the use of antimicrobials in humans, but is also highly influenced by the use of these agents in veterinary medicine, animal husbandry, agriculture, and aquaculture, as has been emphasized at recent meetings sponsored by organizations such as Rockefeller University and the American Society for Microbiology, and in the report on bacterial resistance recently issued by the US Office of Technology Assessment. We have entered an era where both physicians and patients must take on the responsibility to use antimicrobials wisely and judiciously. Just as in the days at the turn of the century when the public was an integral part of establishing quarantines for infectious diseases, now again the public's cooperation must be sought for this latest threat to public health. The multiresistant organisms of the 1990s are a grim warning of the possibility of the postantibiotic era.

Bacteria↗
PubMed2000

Hygienic aspects of storage and use of semen for artificial insemination.

The artificial insemination (AI) industry has developed over the last 50 years to the extent that it is used in almost every country in the world. One of the main factors contributing to its success is the confidence of the farmers that germplasm is not associated with pathogens, so that AI can be performed without risks. This has been achieved as a result of a considerable amount of research based on sound scientific data that has identified the major risk pathogens. A summary of these studies, given in this section, shows that despite the large number of agents that could be transmitted via the semen, there are cost-effective means to prevent such hazards. One of the basic rules is that the males should be housed in strictly protected semen collection centres (SCCs). Such centres should be approved by the veterinary authorities based upon specific criteria, which include special housing and operating specifications. This also includes specific means of monitoring the health of individual males through regular clinical examinations, assessment of semen and testings for various diseases. Two new challenges can now be identified, one relevant to so-called emerging diseases the impact of which on the status of the semen donors should always be assessed, and the second, relates to endangered genetic resources which may become extinct without active conservation programmes. The experience gained by the AI industry over the last 50 years should help to solve those problems. Currently, the use of semen derived from approved SCCs warrants their disease-free status.

Animal Diseases↗
PubMed1976

The development in beef cattle manure of Petriedllidium boydii (Shear) Malloch, a potential pathogen for man and cattle.

Petriellidium boydii (Allescheria boydii) dominated the mycoflora of manure samples form three beef cattle feedlots after incubation at room temperature for 4 months. The possible dangers associated with this pathogenic fungus, which causes mycotic abortion in livestock, pulmonary allescheriasis in man, and mycetomas in both man and animals, are discussed. This fungus could create a health hazard in feedlots where in situ manure decompostion is encouraged.

Abortion, Veterinary↗
PubMed1999

[Swine and wild pigs as carriers of zoonoses].

This paper deals with zoonoses in European pig herds and wild boars in general and in particular with the risk of infection carried by veterinarians, farmers and workers handling pigs and pork in slaughterhouses and meat processing companies. Furthermore the risk of infection and intoxication as a result of pork consumption is discussed. Special reference is made to the responsibility of veterinarians for keeping production animals healthy and informing animal owners and consumers about zoonoses. It would appear that it will be necessary in future to intensify veterinarian herd care, perform regional monitoring and surveillance programmes, participate in establishing specific pathogen-free herds and to foster diagnosis and research into zoonoses together with human medicine.

Agricultural Workers' Diseases↗
PubMed1996

Animal health and the trade in aquatic animals within and to the European Union.

The creation of a single European market has significantly extended the scope of veterinary animal and public health legislation. This extension includes aquatic animals, and a comprehensive set of directives and decisions has been developed to ensure free circulation of aquaculture animals and their products, while guaranteeing a high level of animal health. At the same time, and in the same context, other directives have been adopted which organise checks on animals and products within and to the European Union (EU), as well as accompanying financial measures. Animal health legislation for the movement of aquaculture animals is also based on a number of principles, including the following: --the definition of important pathogens and their hosts --zoning (regionalisation)--the obligation for EU Member States to move animals only from areas or farms with high health status to and between areas and farms with equal or lower health status--the prescription of a testing regime to improve animal health status in zones or farms. In addition, disease control prescriptions have been established or are being considered for adoption. These include the establishment of national and EU reference laboratories, as well as the application of contingency plans and the measures to be taken in the event of a disease outbreak.

Animals↗
PubMed2000

Molecular strategies for interrupting arthropod-borne virus transmission by mosquitoes.

Arthropod-borne virus (arbovirus) infections cause a number of emerging and resurgent human and veterinary infectious diseases. Traditional means of controlling arbovirus diseases include vaccination of susceptible vertebrates and mosquito control, but in many cases these have been unavailable or ineffective, and so novel strategies for disease control are needed. One possibility is genetic manipulation of mosquito vectors to render them unable to transmit arboviruses. This review describes recent work to test the concept of pathogen-derived resistance in arthropods by expression of viral genes in mosquito cell cultures and mosquitoes. Sense and antisense genome sequences from La Crosse virus (LAC) (a member of the Bunyaviridae) and dengue viruses serotypes 1 to 4 (DEN-1 to DEN-4) (members of the Flaviviridae) were expressed in mosquito cells from double-subgenomic and replicon vectors based on Sindbis virus (a member of the Togaviridae). The cells were then challenged with homologous or related viruses. For LAC, expression of antisense sequences from the small (S) genome segment, particularly full-length antisense S RNA, effectively interfered with replication of challenge virus, whereas expression of either antisense or sense RNA from the medium (M) segment was completely ineffective in LAC inhibition. Expression of sense and antisense RNA derived from certain regions of the DEN genome also blocked homologous virus replication more effectively than did RNA from other regions. Other parameters of RNA-mediated interference have been defined, such as the time when replication is blocked and the minimum size of effector RNA. The mechanism of RNA inhibition has not been determined, although it resembles double-stranded RNA interference in other nonvertebrate systems. Prospects for application of molecular strategies to control arbovirus diseases are briefly reviewed.

Animals↗
PubMed2025

Molecular Detection and Characterization of Bovine Diarrhea Virus (BVDV) in Aborted Fetuses and Semen Samples from Paraguay.

Bovine viral diarrhea virus (BVDV) is the most prevalent pathogen in cattle and causes significant economic losses due to its severe clinical manifestations. It belongs to the family Flaviviridae and is distributed in species A, B, and H within the genus Pestivirus. The objective of this study was to detect and characterize BVDV using molecular techniques (RT-PCR) in semen and aborted fetuses samples that were sent to the CEDIVEP (Veterinary Diagnostic Center of Paraguay) laboratory. Seventy-three samples of semen from bulls were analyzed, and 54.7% of the samples were positive for Pestivirus A. The presence of Pestivirus A and H was detected in 2/8 spontaneously aborted fetuses. The genotypes of four individual samples of type A and four samples of type H organs were confirmed by partial sequencing of the 5-UTR region. The presence of BVDV was confirmed by molecular techniques for the first time in our country through its detection in different types of samples, as well as the presence of two genotypes. This suggests that the circulation of this virus can cause significant losses in cattle production in Paraguay.

Diarrhea Viruses, Bovine Viral↗
PubMed2003

A brief history of the prevention of infectious diseases by immunisations.

Infectious diseases have always been a terrible scourge for humans. The appearance of these plagues, as they were called without distinction, was generally connected to various conditions: asters, climatic changes or religious reasons. The concept of contagious, and then infectious, diseases came slowly. Variolation, i.e. transmission of 'virulent' matter to induce a natural disease and the immunity against it, was brought from Constantinople to England by Lady Montague, in 1721. This 'variolation' technique was also often performed in veterinary medicine against diseases like sheep-pox or pleuropneumonia. As 'vaccination' is the term generally accepted for 'immunisation', variolation can be the word designating such a technique. The second period of the history of immunisation began, in 1880, with the studies of Pasteur and his collaborators. A great number of bacterial vaccines were developed: dead, live but attenuated or only parts of pathogens. The viruses were produced in animals, then in eggs and at last, in tissue cultures. Second generation vaccines appeared with genetic engineering: recombinant vaccines, vector vaccines, nucleic acids vaccines, and markers vaccines, among others. These novel technologies can permit the development of new ones and improve the quality of the vaccines already existing.

Bacterial Infections↗
PubMed1990

Pathogenicity of attenuated peste des petits ruminants virus in sheep and goats.

Progressive loss of virulence for goat kids was noticed when peste des petits ruminants (PPR) virus was passaged in Vero cells. While goats inoculated with the 60th passage suffered from the clinical PPR disease and mortality, goats inoculated with the 80th passage did not show any sign of the disease. If the progressive loss of virulence of the virus with passage continues, it will not be long before a homologous PPR vaccine will be obtained at the National Veterinary Institute, Vom.

Animals↗
PubMed1994

Detection of porcine reproductive and respiratory syndrome virus and efficient differentiation between Canadian and European strains by reverse transcription and PCR amplification.

Two sets of oligonucleotide primers (1008PS-1009PR and 1010PLS-1011PLR) were designed according to the sequence of the nucleocapsid protein (N) gene of Quebec reference strain IAF-exp91 of porcine reproductive and respiratory syndrome virus (PRRSV). The primers were used in reverse transcription and PCR (RT-PCR) experiments for detection of viral genomic RNA either from infected porcine alveolar macrophages (PAM) or tissues from experimentally infected specific-pathogen-free pigs. Considering the high degree of variation detected between the nucleotide sequences of the N genes of IAF-exp91 and Lelystad virus (LV) strains of PRRSV, the primers 1008PS-1009PR were referred to as the specific primers, since they were chosen in such a manner that they could amplify only sequences from IAF-exp91 RNA and not from LV. On the other hand, the primer pair 1010PLS-1011PLR was common to both strains of PRRSV. When analyzed by agarose gel electrophoresis, the products of RT-PCR from each set of primers were resolved as single band of the predicted size, the specificity of amplified products being confirmed by Southern blotting with a specific IAF-exp91 N gene probe. No amplification was observed when RNA was extracted from uninfected PAM or from other porcine viruses. As expected, only the common primer pair was able to amplify RNA from the Quebec reference strain and two European strains (LV and Weybridge). The resulting bands displayed differences in electrophoretic mobilities due to the absence of 37 nucleotides in both European strains, thus allowing their differentiation from the IAF-exp91 strain. Most of the tissue culture-adapted Quebec isolates were detected with both primer pairs. The sensitivity of the enzymatic amplification method for detection of PRRSV from lung tissues was a 50% tissue culture infective dose of 5. RT-PCR was found to be more sensitive than indirect immunofluorescence assay for detection of PRRSV in tissues from experimentally infected pigs and as sensitive as virus isolation in PAM, especially when combined with Southern blotting with the digoxigenin-labeled N probe and chemiluminescence detection.

Abortion, Veterinary↗
PubMed2002

Genomics and the prospects for the discovery of new targets for antibacterial and antifungal agents.

The current increase in the number of microbes resistant to antibacterial or antifungal agents represents a potential crisis in human and veterinary medicine. Some believe that we are entering a post-antibiotic era where most antibiotics no longer will be efficacious. Therefore, it is important that new antibiotics be developed. However, because of the potential for cross-resistance, new targets for the discovery of antibiotics are needed particularly where resistance does not currently exist. The results obtained from the sequencing of genomes from pathogenic bacterial and fungal microbes provide an opportunity to ameliorate this problem. Genomic sequence data can be used to identify new genes that could be used as targets for new antibiotic discoveries. Viable new target genes might represent those that are widely distributed among pathogens or that have homologs and are essential for the viability of the organism. Chemical compounds that attack such targets would be expected to have classical antibiotic activities. Less widely distributed genes still could be valuable targets for narrow spectrum antibiotics. While many of these genes will have known or putative functions based on DNA sequence homology, the most interesting genes are the newly discovered genes with unknown functions. In this paper, it is suggested that novel, non-traditional targets also will be found through the analysis of genome sequences: those that are involved in disease pathogenesis and those that are involved in adaptation and growth in infection sites. The advantage of the non-classical targets is that targeting these sites may not result in the same degree of selective pressure that encourages resistance, and these could have a longer therapeutic life time.

Animals↗
PubMed2002

The evolution of bovine viral diarrhea: a review.

The economic importance of bovine viral diarrhea is increasing with the emergence of seemingly more virulent viruses, as evidenced by outbreaks of hemorrhagic syndrome and severe acute bovine viral diarrhea beginning in the 1980s and 1990s. It appears that evolutionary changes in bovine viral diarrhea virus were responsible for these outbreaks. The genetic properties of the classical bovine viral diarrhea virus that contribute to the basis of current diagnostic tests, vaccines, and our understanding of pathogenic mechanisms are now being reevaluated because of these "new" virus strains. This shift in virulence has confounded both nomenclature and the significance of current bovine viral diarrhea virus categorization. The purpose of this review is to summarize our current understanding of bovine viral diarrhea virus with a chronological review of prevailing scientific tenets and practices as described in clinical and scientific North American veterinary journals and textbooks. The first part of this review describes how we have arrived at our current understanding of the viruses, the diseases, and their nomenclature. The second part of the review deals with current concepts in virology and how these concepts may both explain and predict bovine viral diarrhea virus pathogenesis. By reviewing how knowledge of bovine viral diarrhea has evolved and the theories of how the virus itself is able to evolve, the interpretation of diagnostic tests are more effectively utilized in the control and treatment of bovine viral diarrhea virus associated disease.

Animals↗