Animal pathogens and their impact on animal health, the economy, food security, food safety and public health.

Animal pathogens attract attention in both the livestock and public health sectors for their impacts on socio-economics, food safety and security, and human health. These impacts are felt at the household, national, regional and global levels. Whereas the World Organisation for Animal Health (OIE) has identified 118 animal diseases as notifiable, based on their potential for impact on trade, there is a selected subset that have been classified as posing a greater threat to countries due to unique characteristics, such as being highly transmissible, spreading rapidly within and between countries, and requiring cooperation between several countries to control their spread or exclude them. While these 'transboundary diseases' are endemic in much of the world, particularly the developing nations, many countries are classified as disease free. Following the terrorist events of 11 September 2001 in the United States, a small group of zoonotic pathogens and a group of animal-specific pathogens (those that cause what are referred to as `high-consequence foreign animal diseases'), were classified as high-risk, biothreat 'select agents'. Rather than providing a comprehensive review of all animal pathogens, the authors briefly review the impact of these high-risk biothreat agents on animal health, the economy, food security and safety, and public health, using highly pathogenic avian influenza, foot and mouth disease and brucellosis as examples. They focus on the impact of these diseases in the context of high-income countries and low- and middle-income countries, comparing and contrasting their impact at the national and individual household levels.

Les agents pathogènes d'origine animale revêtent une grande importance tant pour le secteur de l'élevage que pour celui de la santé publique, en raison de leurs conséquences sur la société et l'économie, sur la sécurité alimentaire, sur la sécurité sanitaire des aliments et sur la santé publique. Ces impacts sont perceptibles à l'échelle des ménages, des pays, des régions et du monde. L'Organisation mondiale de la santé animale (OIE) a établi une liste de 118 maladies animales à déclaration obligatoire en se basant principalement sur leurs conséquences potentielles pour le commerce ; néanmoins, un sous-ensemble de la liste concerne les maladies qui font peser un risque élevé sur les pays, de par leurs caractéristiques uniques, par exemple leur contagiosité, la rapidité de leur potentiel de propagation dans le territoire national ou d'un pays à l'autre, ou la nécessité de mettre en place une coopération internationale en vue de maîtriser leur propagation ou de les éliminer. Ces « maladies transfrontalières ¼ sont présentes à l'état endémique dans une grande partie du monde, en particulier dans les pays en développement, tandis que d'autres pays sont considérés comme « indemnes ¼. Suite aux attaques terroristes du 11 septembre 2001 aux États-Unis d'Amérique, les maladies animales dites « exotiques ¼ ainsi qu'un petit nombre d'agents pathogènes zoonotiques ont été classés dans la catégorie des « agents biologiques à haut risque ¼. Plutôt que de fournir un inventaire exhaustif des agents pathogènes d'origine animale, les auteurs résument l'impact de ces agents biologiques à haut risque sur la santé animale, l'économie, la sécurité alimentaire, la sécurité sanitaire des aliments et la santé publique, en illustrant leur propos avec les exemples de l'influenza aviaire hautement pathogène, la fièvre aphteuse et la brucellose. Ils examinent l'impact de ces maladies dans le contexte des pays à revenus élevés, mais aussi des pays à revenus faibles ou intermédiaires, en comparant et en détaillant les impacts respectifs à l'échelle nationale ainsi qu'à l'échelle des ménages.

Por su influencia en factores socioeconómicos y en temas como la higiene de los alimentos, la seguridad alimentaria o la salud humana, los patógenos animales atraen la atención de los sectores de la producción animal y la salud pública. Dicha influencia se deja sentir tanto a nivel de los hogares como a escala nacional, regional y mundial. Aunque la Organización Mundial de Sanidad Animal (OIE) tiene catalogadas 118 enfermedades animales como «de declaración obligatoria¼, atendiendo a sus posibles consecuencias para el comercio, hay un pequeño subconjunto de ellas que se consideran especialmente peligrosas para los países porque revisten características singulares, como el hecho de ser muy transmisibles, propagarse con gran rapidez entre los países y dentro de ellos o exigir cooperación entre varias naciones para combatir su propagación o atajarlas. Estas «enfermedades transfronterizas¼ son endémicas en gran parte del mundo, especialmente en las naciones en desarrollo, pero también hay muchos países que están considerados «libres¼ de ellas. Después de los atentados terroristas que sufrieron los Estados Unidos el 11 de septiembre de 2001, las llamadas enfermedades animales «extranjeras¼, junto con un pequeño grupo de patógenos zoonóticos, fueron catalogadas como «agentes selectos¼ de alto riesgo de amenaza biológica. En lugar de ofrecer una panorámica completa de todos los patógenos animales, los autores repasan brevemente el impacto de estos agentes calificados de alto riesgo y portadores de una amenaza biológica en la sanidad animal, la economía, la seguridad alimentaria, la higiene de los alimentos y la salud pública, valiéndose para ello de los ejemplos de la influenza aviar altamente patógena, la fiebre aftosa y la brucelosis. Centrándose en el impacto de estas enfermedades en el contexto de los países de renta alta y en el de los países de renta baja o media, comparan y contrastan tal impacto a escala nacional y en el ámbito de los hogares.

A survey of veterinary antimicrobial prescribing practices, Washington State 2015.

Antimicrobial resistance is a growing global health issue. It is also a recognised problem in veterinary medicine. Between September and December 2015 the authors administered a cross-sectional survey to licensed veterinarians in Washington State to assess factors affecting antimicrobial prescribing practices among veterinarians in Washington State. Two hundred and three veterinarians completed the survey. The majority of respondents (166, 82 per cent) were engaged in small animal or exotic animal practice. 24 per cent of respondents reported not ordering culture and sensitivity (C/S) testing in practice. Of the 76 per cent of veterinarians who reported ordering C/S tests, 36 per cent reported ordering such testing 'often' or 'always' when treating presumptive bacterial infections. Most respondents (65 per cent) mentioned cost as the most common barrier to ordering a C/S test. Only 16 (10 per cent) respondents reported having access to or utilising a clinic-specific antibiogram. This survey demonstrated that while antimicrobials are commonly used in veterinary practice, and veterinarians are concerned about antimicrobial resistance, cost is a barrier to obtaining C/S tests to guide antimicrobial therapy. Summaries of antimicrobial resistance patterns are rarely available to the practising veterinarian. Efforts to promote antimicrobial stewardship in a 'One Health' manner should address barriers to the judicious use of antimicrobials in the veterinary practice setting.

Prospects for recombinant vaccines against Babesia bovis and related parasites.

Babesial parasites infect cattle in tropical and temperate regions of the world and cause significant morbidity and mortality. Discovery of protective antigens that could be used in a killed vaccine has been slow and to date there are few promising vaccine candidates for cattle Babesia. This review describes mechanisms of protective innate and adaptive immune responses to babesial parasites and different strategies to identify potentially protective protein antigens of B. bovis, B. bigemina, and B. divergens. Successful parasites often cause persistent infection, and this paper also discusses how B. bovis evades and regulates the immune response to promote survival of parasite and host. Development of successful non-living recombinant vaccines will depend on increased understanding of protective immune mechanisms and availability of parasite genomes.

A unique phospholipid organization in bovine erythrocyte membranes.

Ruminant erythrocytes are remarkable for their choline-phospholipid anomalies; namely, low or absent phosphatidylcholine (PC) along with high sphingomyelin levels. Here, we report another anomaly in bovine erythrocytes that affects aminophospholipids: phosphatidylethanolamine (PE) shows an extreme asymmetry, with only 2% of the total present in the outer leaflet. Furthermore, we found that phospholipase A(2), an enzyme located on the external surface of the erythrocytes, shows higher activity against PC than against PE. In addition, we observed that acylation of PE is by far the most important biosynthetic event in this system. We propose that deacylation of PE and PC by phospholipase A(2) to generate lysocompounds, followed by selective reacylation of lyso-PE in the inner leaflet, can account for the compositional and architectural peculiarities of bovine erythrocyte membranes.

Molecular basis for variable expression of merozoite surface antigen gp45 among American isolates of Babesia bigemina.

Immunization with the merozoite surface glycoprotein gp45 induces protection against challenge using the homologous Babesia bigemina strain. However, gp45 B-cell epitopes are highly polymorphic among B. bigemina strains isolated from different geographical locations within North and South America. The molecular basis for this polymorphism was investigated using the JG-29 biological clone of a Mexico strain of B. bigemina and comparison with the Puerto Rico, St. Croix, and Texcoco strains. The molecular size and antibody reactivity of gp45 expressed by the JG-29 clone were identical to those of the parental Mexico strain. gp45 cDNA and the genomic locus encompassing gp45 were cloned and sequenced from JG-29. The locus sequence and Southern blot data were consistent with a single gp45 copy in the JG-29 genome. The JG-29 cDNA expressed the full-length protein recognized by the gp45-specific monoclonal antibody 14/1.3.2. The genomes of the Puerto Rico and St. Croix strains of B. bigemina were shown to lack a closely related gp45-like gene by PCR using multiple primer sets and by Southern blots using both full-length and region-specific gp45 probes. This genomic difference was confirmed using unpassaged isolates from a 1999 disease outbreak in Puerto Rico. In contrast, the Texcoco strain retains a gp45 gene, encoding an open reading frame identical to that of JG-29. However, the Texcoco gp45 gene is not transcribed. These two mechanisms, lack of a closely related gp45-like gene and failure to transcribe gp45, result in generation of antigenic polymorphism among B. bigemina strains, and the latter mechanism is unique compared to prior mechanisms of antigenic polymorphism identified in babesial parasites.

Characterization of caprine interleukin-4.

Caprine interleukin-4 (IL-4) cDNA was cloned from RNA of mitogen stimulated goat peripheral blood mononuclear cells utilizing reverse transcriptase-polymerase chain reaction. The sequence of caprine IL-4 cDNA corresponds to a 535 nucleotide mRNA with 5'- and 3'-untranslated regions and a 405 nucleotide open reading frame, the first 66 nucleotides of which encode a putative signal peptide. Mature IL-4 is a 12.8kDa protein containing six cysteine residues and two potential N-linked glycosylation sites and is highly homologous with other ruminant IL-4. The predicted molecular mass of mature unglycosylated IL-4 was confirmed by western blot of recombinant caprine IL-4 expressed in bacteria with a monoclonal antibody against a carboxyterminal peptide derived from the predicted amino acid sequence of bovine IL-4. Eukaryotic expression plasmids containing caprine IL-4 cDNA were used to characterize recombinant IL-4. Transcription of IL-4 mRNA was confirmed by transfection of COS-7 and goat synovial membrane cells, and recombinant IL-4 produced by stably transfected L929 cells inhibited inducible nitric oxide synthase in macrophages. Genetic immunization of mice with a caprine IL-4 cDNA expression plasmid induced antibodies against recombinant caprine IL-4 produced in bacteria.

Sensitivity and specificity of the complement fixation test for detection of cattle persistently infected with Anaplasma marginale.

The complement fixation (CF) test commonly is used to identify cattle infected with Anaplasma marginale prior to interstate or international movement. Estimates of the accuracy of the CF test in detecting animals persistently infected with A. marginale vary widely. In this study, the sensitivity and specificity of the CF test for detection of carrier animals was determined using serum from 232 cattle previously defined as A. marginale positive or negative by nested polymerase chain reaction methods and hybridization. Considering results from 2 independent laboratories and interpreting a 1:5 suspect reaction as positive, the best estimate of CF test sensitivity was 20%, with a specificity of 98%. Using a 1:10 cutoff, sensitivity decreased to 14% and specificity increased to 99%. Results of this study indicate that the CF test is ineffective for identifying cattle persistently infected with A. marginale and thus is inadequate for anaplasmosis regulatory and surveillance programs.

Strain composition of the ehrlichia Anaplasma marginale within persistently infected cattle, a mammalian reservoir for tick transmission.

Tick-borne ehrlichial pathogens of animals and humans require a mammalian reservoir of infection from which ticks acquire the organism for subsequent transmission. In the present study, we examined the strain structure of Anaplasma marginale, a genogroup II ehrlichial pathogen, in both an acute outbreak and in persistently infected cattle that serve as a reservoir for tick transmission. Using the msp1alpha genotype as a stable strain marker, only a single genotype was detected in a disease outbreak in a previously uninfected herd. In contrast, a diverse set of genotypes was detected in a persistently infected reservoir herd within a region where A. marginale is endemic. Genotypic diversity did not appear to be rapidly generated within an individual animal, because only a single genotype, identical to that of the inoculating strain, was detected at time points up to 2 years after experimental infection, and only a single identical genotype was found in repeat sampling of individual naturally infected cattle. Similarly, only a single genotype, identical to that of the experimentally inoculated St. Maries or South Idaho strain, was identified in the bloodmeal taken by Dermacentor andersoni ticks, in the midgut and salivary glands of the infected ticks, and in the blood of acutely infected cattle following tick transmission. The results show that mammalian reservoirs harbor genetically heterogeneous A. marginale and suggest that different genotypes are maintained by transmission within the reservoir population.

Immunization of BALB/c mice with killed Neospora caninum tachyzoite antigen induces a type 2 immune response and exacerbates encephalitis and neurological disease.

BALB/c mice were immunized subcutaneously with soluble Neospora caninum tachyzoite antigen (NSO) entrapped in nonionic surfactant vesicles (NISVs) or administered with Freund's complete adjuvant (FCA). Following virulent parasite challenge, groups of mice immunized with NSO and either NISVs or FCA had clinical neurological disease and increased numbers of brain lesions compared to groups of mice inoculated with FCA, NISVs, or phosphate-buffered saline (PBS) alone. Increased numbers of brain lesions were statistically significant only between mice immunized with NISV-NSO and NISV- or PBS-treated mice. Following parasite challenge, brain inflammatory infiltrates in all experimental and control groups of mice were relatively similar and consisted of compact infiltrates of macrophages admixed with various numbers of lymphoid cells. Increased brain lesions in NSO-immunized mice were associated with increased antigen-specific interleukin 4 (IL-4) secretion and increased IL-4:gamma interferon secretion ratios from splenocytes in vitro and increased antigen-specific immunoglobulin G1 (IgG1):IgG2a ratios in vivo. Thus, immunization with whole killed N. caninum antigen and either liposoidal or Freund's adjuvant induced a type 2 immune response that was associated with worsened disease. The present studies emphasize the need to identify specific N. caninum antigens or other delivery systems that will elicit protective immune responses to neosporosis.

Characterization of allelic variation in the Babesia bovis merozoite surface antigen 1 (MSA-1) locus and identification of a cross-reactive inhibition-sensitive MSA-1 epitope.

The Babesia bovis merozoite surface antigen 1 (MSA-1), a member of the variable merozoite surface antigen (VMSA) family, is an immunodominant glycoprotein which elicits antibodies that inhibit erythrocyte invasion. While antigenic polymorphism is a general feature of vmsa genes, the molecular basis and extent of msa-1 sequence polymorphism have not been well characterized. In this study we defined the msa-1 locus in the biologically cloned Mexico Mo7 strain of B. bovis and identified the sequence differences between MSA-1 antigenically dissimilar strains. We then determined whether sequences conserved between distinct msa-1 alleles would induce cross-reactive CD4(+) T lymphocytes or inhibitory antibodies. The msa-1 locus in Mo7 contains a single msa-1 gene flanked by transcribed genes with no sequence homology to members of the VMSA gene family. Argentina B. bovis strains R1A and S2P have msa-1 genes with amino acid sequences that are 98.8% identical to each other, and antibodies against S2P MSA-1 cross-react with native R1A MSA-1. In contrast, identity between the Argentina and Mexico Mo7 msa-1 alleles is only 52%, with no continuous stretch of identity longer than 16 amino acids. Despite limited sequence conservation, antibodies against R1A MSA-1 were able to inhibit invasion of erythrocytes by Mo7 merozoites. The results indicate that inhibition-sensitive epitopes are conserved despite significant sequence divergence between Mexico and Argentina strain alleles and support a conserved functional role for polymorphic MSA-1 in erythrocyte invasion.