Effects of vaccination with Brucella melitensis, strains Rev 1 ΔeryCD and Rev 1, on the reproductive system of young male goats.

The present study evaluates the effects of vaccination with Brucella melitensis strains Rev 1 ΔeryCD and Rev 1 on the reproductive system of male goats. Three groups, each of them consisting of 15 six-month-old brucellosis-free male goats, were studied. The first group was vaccinated with the Rev 1 ΔeryCD strain, the second group received Rev 1 and the third group was inoculated with sterile physiological saline solution. The dose of both strains was of 1×109CFU/ml. Over the course of the five months of this study, three males from each group were euthanized every month. Their reproductive tracts, spleens, and lymph nodes were collected to analyze serology, bacteriology PCR, histology, and immunohistochemistry. Results show that vaccination with B. melitensis strains Rev 1 ΔeryCD and Rev 1 does not harm the reproductive system of male goats. Strain B. melitensis Rev 1 ΔeryCD displayed a lower capacity to colonize the reproductive tract than strain Rev 1, which was attributed to its limited catabolic action toward erythritol.

Identification, Biochemical Characterization, and In Vivo Detection of a Zn-Metalloprotease with Collagenase Activity from Mannheimia haemolytica A2.

Respiratory diseases in ruminants are a main cause of economic losses to farmers worldwide. Approximately 25% of ruminants experience at least one episode of respiratory disease during the first year of life. Mannheimia haemolytica is the main etiological bacterial agent in the ruminant respiratory disease complex. M. haemolytica can secrete several virulence factors, such as leukotoxin, lipopolysaccharide, and proteases, that can be targeted to treat infections. At present, little information has been reported on the secretion of M. haemolytica A2 proteases and their host protein targets. Here, we obtained evidence that M. haemolytica A2 proteases promote the degradation of hemoglobin, holo-lactoferrin, albumin, and fibrinogen. Additionally, we performed biochemical characterization for a specific 110 kDa Zn-dependent metalloprotease (110-Mh metalloprotease). This metalloprotease was purified through ion exchange chromatography and characterized using denaturing and chaotropic agents and through zymography assays. Furthermore, mass spectrometry identification and 3D modeling were performed. Then, antibodies against the 110 kDa-Mh metalloprotease were produced, which achieved great inhibition of proteolytic activity. Finally, the antibodies were used to perform immunohistochemical tests on postmortem lung samples from sheep with suggestive histology data of pneumonic mannheimiosis. Taken together, our results strongly suggest that the 110-Mh metalloprotease participates as a virulence mechanism that promotes damage to host tissues.

Effect of the Lacticaseibacillus paracasei JLM Strain Against Brucella abortus Strains in Ripened Cheese.

This study evaluated the antagonistic effect of the Lacticaseibacillus paracasei JLM strain isolated from aguamiel, against Brucella abortus RB51, S19, and 2308 strains, during the manufacture of soft-ripened cheese. First, the tolerance of Lc. paracasei JLM was tested with pH values and bile salt concentrations for 3 h to simulate digestive tract conditions. The antagonistic effect against B. abortus strains was evaluated through double-layer diffusion and agar well diffusion assays. In addition, the stability of the cell-free supernatant (CFS) was tested with the agar well diffusion method under different conditions of temperature, pH, and treatment with digestive enzymes. Finally, the antagonistic effect against B. abortus strains was observed during the manufacture of ripened cheese for 31 days at 4°C and 25°C using the Lc. paracasei JLM strain as starter culture. The results showed that the Lc. paracasei JLM strain remains viable after exposure to different pH values (from 3.00 to 7.00) and concentrations of bile salts (from 0.5% to 7%). Moreover, the results demonstrate that the growth of the three B. abortus strains was inhibited in both antagonism tests and that CFS maintained 86% activity after heat treatment at 100°C, 121°C, or enzymatic digestion (proteinase K, trypsin, chymotrypsin), but it was inactivated at pH levels above 6. Finally, Lc. paracasei JLM completely inhibited the growth of B. abortus in ripened cheese at 25°C from day 17 and showed greater inhibition on the B. abortus RB51 strain in the ripened cheese at 4°C, showing statistical differences for the B. abortus S19 and B. abortus 2308 strains. The current research concluded that the Lc. paracasei JLM strain has an antagonistic effect on B. abortus, enhancing the potential of its use in the future as a probiotic.

Multiplex assay for the simultaneous detection of antibodies against small ruminant lentivirus, Mycobacterium avium subsp. paratuberculosis, and Brucella melitensis in goats.

Background and Aim: Brucellosis, paratuberculosis (PTb), and infections caused by small ruminant lentivirus (SRLV), formerly known as caprine arthritis encephalitis virus (CAEV), adversely affect goat production systems. Nonetheless, commonly used diagnostic tests can only determine one analyte at a time, increasing disease surveillance costs, and limiting their routine use. This study aimed to design and validate a multiplex assay for antibody detection against these three diseases simultaneously. Materials and Methods: Two recombinant proteins from the SRLV (p16 and gp38), the native hapten of Brucella melitensis, and the paratuberculosis-protoplasmic antigen 3 from Mycobacterium avium subsp. paratuberculosis (MAP) were used to devise and assess a multiplex assay. Conditions for the Luminex® multiplex test were established and validated by sensitivity, specificity, repeatability, and reproducibility parameters. Cut-off points for each antigen were also established. Results: The 3-plex assay had high sensitivity (84%) and specificity (95%). The maximum coefficients of variation were 23.8% and 20.5% for negative and positive control samples, respectively. The p16 and gp38 SRLV antigens are 97% and 95%, similar to the CAEV sequence found in GenBank, respectively. Conclusion: The multiplex test can be effectively used for the simultaneous detection of antibodies against SRLV, MAP and B. melitensis in goats.

Enhancing Therapeutic Efficacy against Brucella canis Infection in a Murine Model Using Rifampicin-Loaded PLGA Nanoparticles.

The in vivo efficacy of rifampicin encapsulated in poly(lactic-co-glycolic acid) (PLGA) nanoparticles was evaluated for the treatment of BALB/c mice experimentally infected with Brucella canis. The PLGA nanoparticles loaded with rifampicin (RNP) were prepared using the single emulsification-solvent evaporation technique, resulting in nanoparticles with a hydrodynamic diameter of 138 ± 6 nm. The zeta potential and polydispersity index values indicated that the system was relatively stable with a narrow size distribution. The release of rifampicin from the nanoparticles was studied in phosphate buffer at pH 7.4 and 37 °C. The release profile showed an initial burst phase, followed by a slower release stage attributed to nanoparticle degradation and relaxation, which continued for approximately 30 days until complete drug release. A combined model of rifampicin release, accounting for both the initial burst and the degradation-relaxation of the nanoparticles, effectively described the experimental data. The efficacy of RNP was studied in vivo; infected mice were treated with free rifampicin at concentrations of 2 mg per kilogram of mice per day (C1) and 4 mg per kilogram of mice per day (C2), as well as equivalent doses of RNP. Administration of four doses of the nanoparticles significantly reduced the B. canis load in the spleen of infected BALB/c mice. RNP demonstrated superior effectiveness compared to the free drug in the spleen, achieving reductions of 85.4 and 49.4%, respectively, when using C1 and 93.3 and 61.8%, respectively, when using C2. These results highlight the improved efficacy of the antibiotic when delivered through nanoparticles in experimentally infected mice. Therefore, the RNP holds promise as a potential alternative for the treatment of B. canis.

Presence of Chlamydia abortus in colostrum, milk, and vaginal discharge samples of sheep

Background: The main transmission route of Chlamydia abortus is by ingesting the microorganism that has been eliminated in vaginal secretions, placental membranes or abortions that contaminate the environment and, possibly, through milk and colostrum. Elimination through vaginal secretions is well documented. However, there are no reports about isolation and identification of C. abortus in the colostrum or milk of infected sheep, so it is important to determine whether or not C. abortus may be present in these secretions, which are the only food of lambs. Objective: To detect C. abortus in colostrum, milk, and vaginal secretions of sheep with a history of reproductive disorders. Methods: Colostrum, milk, and vaginal exudates were collected from 66 sheep. The samples were inoculated in mouse fibroblast cell cultures and the presence of C. abortus determined by direct immunofluorescence. Results: 19 out of 66 colostrum samples (28.7%), 14 out of 66 milk samples (21.2%) and 17 out of 66 vaginal swabs (25.7%) were positive for C. abortus. The 50 samples positive for isolation and detected by immunofluorescence, together with 42 negative samples were subjected to qPCR to amplify a fragment of the ompA gene from C. abortus. Thirty-eight of the 92 samples processed by this technique were positive for C. abortus. Conclusion: The results demonstrated the presence of C. abortus in a high proportion in colostrum, milk and vaginal secretions of infected sheep. To the best of our knowledge, this is the first field study confirming the presence of C. abortus in colostrum, which shows that excretion of Chlamydia by lactogenesis could occur in the first hours after birth.

Antecedentes: La principal vía de transmisión de C. abortus es la ingestión del microorganismo que ha sido eliminado en las secreciones vaginales, membranas placentarias, abortos y, posiblemente, a través de la leche y el calostro. La eliminación a través de secreciones vaginales está bien documentada. Sin embargo, no existen reportes del aislamiento e identificación de C. abortus en el calostro o la leche de ovejas infectadas, por lo que es importante determinar si la bacteria puede o no estar presente en estas secreciones, que son el único alimento de los corderos. Objetivo: Detectar la presencia de C. abortus in calostro, leche y secreciones vaginales de ovejas con antecedentes de problemas reproductivos. Método: Con el propósito de aislar e identificar C. abortus en estas secreciones, se recolectó calostro, leche y exudado vaginal de 66 ovejas. Las muestras fueron inoculadas en cultivos celulares de fibroblastos de ratón y se determinó la presencia de la bacteria por inmunofluorescencia directa. Resultados: Fueron positivas 19 de 66 muestras de calostro (28,7%), 14 de 66 muestras de leche (21,2%) y 17 de 66 hisopos vaginales (25,7%). Las 50 muestras positivas al aislamiento y detectadas por inmunofluorescencia, junto con 42 negativas se sometieron a qPCR para amplificar un fragmento del gen ompA de C. abortus; 38 de las 92 muestras procesadas por esta técnica fueron positivas para C. abortus. Conclusión: Los resultados del presente estudio demostraron la presencia de C. abortus en una alta proporción en el calostro, la leche y las secreciones vaginales de ovejas infectadas. Este es el primer estudio de campo que confirma la presencia de C. abortus en calostro, lo que demuestra que la excreción de clamidia por lactogénesis podría ocurrir en las primeras horas después del nacimiento.

Antecedentes: A principal via de transmissão da Chlamydia abortus é a ingestão do microrganismo que foi eliminado nas secreções vaginais, membranas placentárias ou abortos que contaminam o meio ambiente e, possivelmente, através do leite e colostro. A eliminação pelas secreções vaginais está bem documentada. No entanto, não há relatos de isolamento e identificação de C. Abortus no colostro ou leite de ovelhas infectadas, por isso é importante verificar se a bactéria pode estar ou não presente nessas secreções, único alimento dos cordeiros. Objetivo: Detectar a presença de C. Abortus no colostro, leite e secreções vaginais de ovelhas com histórico de distúrbios reprodutivos Métodos: Para isolar e identificar C. Abortus nessas secreções, foram coletados colostro, leite e exsudato vaginal de 66 ovelhas. As amostras foram inoculadas em cultura de células de fibroblastos de camundongo e a presença da bactéria determinada por imunofluorescência direta. Resultados: 19 de 66 amostras de colostro (28,7%), 14 de 66 amostras de leite (21,2%) e 17 de 66 esfregaços vaginais (25,7%) sendo positivos. As 50 amostras positivas para isolamento e detectadas por imunofluorescência, juntamente com as 42 negativas, foram submetidas a qPCR para amplificar um fragmento do gene ompA de C. Abortus. Trinta e oito das 92 amostras processadas por esta técnica foram positivas para C. Abortus. Conclusão: Os resultados do presente estudo demonstraram a presença de C. Abortus em alta proporção no colostro, leite e secreções vaginais de ovelhas infectadas. Este trabalho é o primeiro estudo de campo na literatura científica confirmando a presença de C. Abortus no colostro, o que mostra que a excreção da clamídia por lactogênese pode ocorrer nas primeiras horas após o nascimento.

Survival of Brucella abortus RB51 and S19 Vaccine Strains in Fresh and Ripened Cheeses.

Brucellosis is a zoonotic infection caused by the consumption of contaminated raw milk and dairy products. This study aims to compare survival rates of Brucella abortus RB51 and S19 vaccine strains to that of virulent B. abortus 2308 strain during the manufacture of fresh and ripened cheeses. To do this, we inoculated fresh pasteurized milk with B. abortus RB51, S19, or 2308 at a 6 × 108 colony-forming unit per milliliter concentration during the cheese making process. Cheese was manufactured at room temperature, then, fresh cheeses were conserved at either 4°C or 25°C for 7 days, while ripened cheeses were conserved for 31 days at the same temperatures. We measured B. abortus survival and pH values during different stages of the process. Our results confirm that all three strains can maintain viable cells in both types of cheeses throughout the process. Survival of B. abortus RB51 was 10 times lower than was the survival of the B. abortus S19 and B. abortus 2308 strains in both fresh and ripened cheeses. Our results also suggest that both temperature and pH can condition Brucella survival. In conclusion, B. abortus RB51 and S19 vaccine strains can survive throughout the manufacture and conservation processes of both fresh and ripened cheeses. In turn, this implies a potential health risk if cheeses contaminated with these strains were to be consumed.

Spatial autocorrelation and co-occurrence of six serovarieties of Leptospira in goat herds of the State of Guanajuato, Mexico.

The epidemiological behavior of six Leptospira serovarieties was analyzed by spatial autocorrelation and co-occurrence of leptospirosis, diagnosed in goat herds located in the State of Guanajuato, Mexico. A total of 1650 goat serum samples were analyzed by microscopic agglutination (MAT). True prevalence (Pv) and 95% confidence interval (CI95) were determined. Spatial autocorrelation was calculated using the spdep package, applying the global Moran's I and local Moran's I of Leptospira in Guanajuato. The probabilistic model of co-occurrence was applied using the co-occur package. Seroprevalence in the State was found to be 45.5% (CI95 42.96; 48.06%). The highest registered frequency was for the Icterohemorrhagiae serovar (Pv 34.16%; CI95 31.74, 36.65%), followed by the serovar Hardjo-prajitno (Pv: 6.77%; CI95 5.33, 8.40%). Other serovarieties showed a Pv < 5%. Global spatial autocorrelation, only for the Icterohemorrhagiae serovar, was I > 1, while local Moran's I revealed that five of the six Leptospira serovarieties were spatially correlated. The probabilistic model of co-occurrence detected negative associations between Icterohemorrhagiae and the other serovarieties. The current study demonstrates the presence of Leptospira in goat herds of the State of Guanajuato. The diagnosed serovarieties show an aggregation pattern associated to risk zones and disease-transmitting vectors. Antibody co-occurrence analysis revealed dominance of the Icterohemorrhagiae serovar. A multidisciplinary approach including spatial epidemiology, ecological analyses, and serological vigilance will generate useful information for the prevention and control of leptospirosis in caprine production units.

Effect of apo-lactoferrin on leukotoxin and outer membrane vesicles of Mannheimia haemolytica A2.

Mannheimia haemolytica serotype A2 is the principal cause of pneumonic mannheimiosis in ovine and caprine livestock; this disease is a consequence of immune suppression caused by stress and associated viruses and is responsible for significant economic losses in farm production worldwide. Gram-negative bacteria such as M. haemolytica produce outer membrane (OM)-derived spherical structures named outer membrane vesicles (OMVs) that contain leukotoxin and other biologically active virulence factors. In the present study, the relationship between M. haemolytica A2 and bovine lactoferrin (BLf) was studied. BLf is an 80 kDa glycoprotein that possesses bacteriostatic and bactericidal properties and is part of the mammalian innate immune system. Apo-BLf (iron-free) showed a bactericidal effect against M. haemolytica A2, with an observed minimal inhibitory concentration (MIC) of 16 µM. Sublethal doses (2-8 µM) of apo-BLf increased the release of OMVs, which were quantified by flow cytometry. Apo-BLf modified the normal structure of the OM and OMVs, as observed through transmission electron microscopy. Apo-BLf also induced lipopolysaccharide (LPS) release from bacteria, disrupting OM permeability and functionality, as measured by silver staining and SDS and polymyxin B cell permeability assays. Western blot results showed that apo-BLf increased the secretion of leukotoxin in M. haemolytica A2 culture supernatants, possibly through its iron-chelating activity. In contrast, holo-BLf (with iron) did not have this effect, possibly due to differences in the tertiary structure between these proteins. In summary, apo-BLf affected the levels of several M. haemolytica virulence factors and could be evaluated for use in animals as an adjuvant in the treatment of ovine mannheimiosis.

Risk factors associated with the seroprevalence of paratuberculosis in sheep flocks in the hot-arid region of Sonora, México.

Paratuberculosis is caused by Mycobacterium avium subspecies paratuberculosis (MAP), a chronic disease of a negative economic impact on sheep production. In the state of Sonora, Mexico, there are no reports on the prevalence of MAP in sheep and risk factors associated with it. The objective of this study was to estimate the seroprevalence of MAP and risk factors associated by testing antibody-positive in sheep flocks located in the arid and hot region of Sonora, Mexico. A cross-sectional study was conducted from February 2012 to December 2014, in 43 flocks. Serum samples from 1178 individual sheep were obtained to detect antibodies against MAP by immunodiffusion in agar-gel. During blood sampling, information about animal and flock management risk factors were obtained by applying a questionnaire to the owners. Risk factors associated with seroprevalence of MAP were estimated using binary logistic regression. The true prevalence of MAP was 7.48% (95% CI 5.98, 8.98) and 53.5% of flocks had at least one seropositive animal. An animal was more likely to be seropositive if it was from a large flock (> 300 animals; OR 3.52, 95% CI 1.24, 9.99) and was born outside the farm (OR 6.24; 95% CI 2.9-1, 3.52). This is the first report of Mycobacterium avium subspecies paratuberculosis seroprevalence in sheep, in Sonora, Mexico. Large flocks and the entry of new animals to the flock were critical risk factors associated with MAP seropositivity.

First genome sequencing and comparative analyses of Corynebacterium pseudotuberculosis strains from Mexico.

Corynebacterium pseudotuberculosis is a pathogenic bacterium which has been rapidly spreading all over the world, causing economic losses in the agricultural sector and sporadically infecting humans. Six C. pseudotuberculosis strains were isolated from goats, sheep, and horses with distinct abscess locations. For the first time, Mexican genomes of this bacterium were sequenced and studied in silico. All strains were sequenced using Ion Personal Genome Machine sequencer, assembled using Newbler and SPAdes software. The automatic genome annotation was done using the software RAST and in-house scripts for transference, followed by manual curation using Artemis software and BLAST against NCBI and UniProt databases. The six genomes are publicly available in NCBI database. The analysis of nucleotide sequence similarity and the generated phylogenetic tree led to the observation that the Mexican strains are more similar between strains from the same host, but the genetic structure is probably more influenced by transportation of animals between farms than host preference. Also, a putative drug target was predicted and in silico analysis of 46 strains showed two gene clusters capable of differentiating the biovars equi and ovis: Restriction Modification system and CRISPR-Cas cluster.

Genetic Analysis Method for Staphylococcus chromogenes Associated with Goat Mastitis.

Mastitis in goats is mainly caused by coagulase-negative Staphylococcus (CNS). The identification methods for this group are based on evaluating the expression of phenotypic characteristics such as the ability to metabolize various substrates; however, this is disadvantageous as these methods are dependent on gene expression. In recent years, genotyping methods such as the Multiple Locus Variable-Number Tandem Repeat Analysis (MLVA) and gene identification have been useful for epidemiological study of several bacterial species. To develop a genotyping method, the genome sequence of Staphylococcus chromogenes MU970 was analysed. The analysis showed nine virulence genes described in Staphylococcus aureus. The MLVA was developed using four loci identified in the genome of S. chromogenes MU970. This genotyping method was examined in 23 strains of CNS isolated from goat mastitis. The rate of discrimination for MLVA was 0.8893, and the highest rates of discrimination per the index of Simpson and Hunter-Gaston were 0.926 and 0.968 for the locus 346_06, respectively. The virulence genes were present in all strains of S. chromogenes but not in other CNS. The genotyping method presented in this paper is a viable and easy method for typifying CNS isolates from mastitis cases in different regions and is an ideal mean of tracking this disease.

PATHOGENIC LEPTOSPIRA SEROVARS IN FREE-LIVING SEA LIONS IN THE GULF OF CALIFORNIA AND ALONG THE BAJA CALIFORNIA COAST OF MEXICO.

The California sea lion ( Zalophus californianus ), a permanent inhabitant of the Gulf of California in Mexico, is susceptible to pathogenic Leptospira spp. infection, which can result in hepatic and renal damage and may lead to renal failure and death. During summer 2013, we used the microscopic agglutination test (MAT) to investigate the prevalence of anti-Leptospira antibodies in blood of clinically healthy sea lion pups from seven rookery islands on the Pacific Coast of Baja California (Pacific Ocean) and in the Gulf of California. We also used PCR to examine blood for Leptospira DNA. Isolation of Leptospira in liquid media was unsuccessful. We found higher antibody prevalence in sea lions from the rookery islands in the gulf than in those from the Pacific Coast. Antibodies against 11 serovars were identified in the Gulf of California population; the most frequent reactions were against serovars Bataviae (90%), Pyrogenes (86%), Wolffi (86%), Celledoni (71%), and Pomona (65%). In the Pacific Ocean population, MAT was positive against eight serovars, where Wolffi (88%), Pomona (75%), and Bataviae (70%) were the most frequent. Serum samples agglutinated with more than one Leptospira serovar. The maximum titer was 3,200. Each island had a different serology profile, and islands combined showed a distinct profile for each region. We detected pathogenic Leptospira DNA in 63% of blood samples, but we found no saprophytic Leptospira. Positive PCR results were obtained in blood samples with high and low MAT titers. Together, these two methods enhance the diagnosis and interpretation of sea lion leptospirosis. Our results may be related to human activities or the presence of other reservoirs with which sea lions interact, and they may also be related to sea lion stranding.

Survival of Brucella abortus aqpX mutant in fresh and ripened cheeses.

The objective of this work was to evaluate the survival of a Brucella abortus aqpX mutant during the elaboration and conservation of fresh and ripened cheeses at 4 °C and 24 °C. The pH values and water activity were monitored for each type of cheese. The fresh cheese was elaborated with raw milk inoculated with 6×108 colony-forming units (CFU)/mL each of parental and mutant strain. Ripening cheeses were elaborated with both raw and pasteurized milk and inoculated with 12×108 CFU/mL each of parental and mutant strains. In fresh cheese, survival was observed during elaboration and conservation for 7 days at 4 °C in mutant and parental strains. The number of survivors of the mutant strain was 10 times lower compared with the parental strain at pH 5 and a(w) of 0.930. In the cheese elaborated with raw milk and ripened at 24 °C, both strains survived until day 17 at pH 4.0 and a(w) of 0.89. However, when the cheese was elaborated with pasteurized milk, the parental strain survived until day 31 of ripening, and the mutant strain survived 24 days at pH 4 and a(w) of 0.886. The survival of the mutant strain showed a diminution of one logarithm during elaboration and ripening of cheese as compared with the parental strain. When the cheese was elaborated with raw milk and ripened at 4 °C, survival of the parental strain was 24 days, whereas the mutant strain survived only 17 days (pH 5 and a(w) 0.90). Regarding the cheese elaborated with pasteurized milk and maturated at 4 °C, both strains survived 31 days (pH 5 and a(w) 0.90), with the same survival diminution during elaboration and ripening. Our results show that in both types of cheese, the mutated aqpX strain survived 10 times less than the parental strain, which shows that the aqpX gene can be related to the survival of Brucella abortus in this type of cheese.

Análisis de riesgos de la brucelosis en el estado de Tlaxcala / Risk analysis of brucelosis in the state of Tlaxcala

Objetivo. Identificar los riesgos de la brucelosis en el estado de Tlaxcala, México. Material y métodos. Se realizó un diagnóstico de tipo social en los municipios de Huamantla, Ixtenco y Teacalco, localizadas en la región oriente del estado. Se determinó la seroprevalencia de brucelosis en cabras y humanos. Resultados. El 46.9% de productores conoce los programas de la vacunación contra brucelosis; 19.7% aplica vacuna y 80.3% no aplica vacuna. Huamantla presentó la mayor seroprevalencia de brucelosis animal en 66.8 por ciento. San José Teacalco distribuye y comercializa quesos no pasteurizados en una distancia mayor de 270 km, lo que amplía los riesgos de contagio por brucelosis. Ixtenco registró la mayor prevalencia de brucelosis en humanos con 1.51 por ciento. Conclusión. Los municipios estudiados presentan riesgos de contagio y propagación de la brucelosis.

Objective. To identify the risk of brucellosis in the state of Tlaxcala, Mexico. Materials and methods. A diagnosis of social type was conducted in the municipalities of Huamantla, Ixtenco and Teacalco, located in the eastern region of the state. The seroprevalence of brucellosis in goats and humans was determined. Results. 46.9% of producers know the programs of vaccination against brucellosis; 19.7% apply the vaccine and 80.3% do not apply the vaccine. Huamantla had the highest seroprevalence of animal brucellosis in 66.8%; San Jose Teacalco distributes unpasteurized cheeses to a distance of 270 km, increasing the risk of infection with brucellosis. Ixtenco recorded the highest prevalence of brucellosis in humans, with 1.51%. Conclusion. The municipalities studied present risks of infection and spread of brucellosis.

Infection of California sea lions (Zalophus californianus) with terrestrial Brucella spp.

Infections with Brucella ceti and pinnipedialis are prevalent in marine mammals worldwide. A total of 22 California sea lions (Zalophus californianus) were examined to determine their exposure to Brucella spp. at San Esteban Island in the Gulf of California, Mexico, in June and July 2011. Although samples of blood, vaginal mucus and milk cultured negative for these bacteria, the application of rose Bengal, agar gel immunodiffusion, PCR and modified fluorescence polarization assays found that five animals (22.7%) had evidence of exposure to Brucella strains. The data also suggested that in two of these five sea lions the strains involved were of terrestrial origin, a novel finding in marine mammals. Further work will be required to validate and determine the epidemiological significance of this finding.

Milk yield and reproductive performance of brucellosis-vaccinated but seropositive Holstein cows.

The aim of this research was to study if seropositivity for brucellosis in vaccinated cows against this disease hampers reproductive performance and milk production in high-yielding Holstein cows. For this purpose 1,026 healthy cows and 372 cows seropositive for brucellosis were enrolled in this study. Cows positive to card test and subsequently to the rivanol test were further subjected to the radial immunodiffusion (RID) test. It was found that only 11% of the presumably infected cows by brucellosis screening tests were really infected with this disease. The reproductive performance of the group of cows with 11% Brucella-infected animals was not impaired; overall pregnancy rate did not differ between seropositive and healthy cows (30.9 vs. 29.6%). The abortion rates were similar between seropositive cows (5.3%) and seronegative animals (6.9%). Cows in the herd with 11% Brucella-infected animals produced significantly more milk than unaffected cows over a 305-day lactation (10,684 ± 1,720 vs. 10,345 ± 1,736; mean ± SD; P < 0.05). It was concluded that in dairy herds vaccinated against brucellosis with both 19 and RB51 strains, supplemental tests such as RID need to be conducted on all reactors in order to maintain diagnostic accuracy. These results also indicate that 11% animal prevalence of brucellosis did not exert a detrimental effect on 305-day milk yield and reproductive performance in high milk-yielding Holstein cows.

[Risk analysis of brucelosis in the state of Tlaxcala]. / Análisis de riesgos de la brucelosis en el estado de Tlaxcala.

OBJECTIVE: To identify the risk of brucellosis in the state of Tlaxcala, Mexico. MATERIALS AND METHODS: A diagnosis of social type was conducted in the municipalities of Huamantla, Ixtenco and Teacalco, located in the eastern region of the state. The seroprevalence of brucellosis in goats and humans was determined. RESULTS: 46.9% of producers know the programs of vaccination against brucellosis; 19.7% apply the vaccine and 80.3% do not apply the vaccine. Huamantla had the highest seroprevalence of animal brucellosis in 66.8%; San Jose Teacalco distributes unpasteurized cheeses to a distance of 270 km, increasing the risk of infection with brucellosis. Ixtenco recorded the highest prevalence of brucellosis in humans, with 1.51%. CONCLUSION: The municipalities studied present risks of infection and spread of brucellosis.

Transmisión de Brucella abortus en becerras menores de tres meses diagnosticadas por medio de las pruebas de tarjeta e inmunodifusión radial en dos hatos lecheros del estado de Querétaro / Transmission of Brucella abortus to female calves younger than three months of age, diagnosed by the card and radial immunodiffusion tests in two dairy herds in the state of Queretaro, Mexico

La transmisión de Brucella abortus a becerras de vacas positivas y negativas se determinó a la primera semana de vida y al tercer mes de edad. Se trabajó con dos hatos: el hato 1, con 670 vacas en producción, presentaba una seroprevalencia a brucelosis de 21.6% (145/670). En este hato se formaron dos grupos: vacas positivas y vacas negativas, como resultado de las pruebas de tarjeta y de inmunodifusión radial (IDR) realizadas con hapteno nativo. Se tomaron pruebas de sangre de las vacas en dos ocasiones, a la semana de edad y antes de que los animales fueran vacunados contra B. abortus. De las 22 vacas del grupo positivo, 2 (9.1%) becerras resultaron positivas a la primera semana de vida, pero no se encontraron vacas positivas a los tres meses de edad. En el grupo de becerras nacidas de vacas negativas no se encontraron animales positivos a la semana de vida, pero a los tres meses de edad, 4 de las 22 becerras resultaron positivas con la prueba de IDR. La tasa de prevalencia de vacas positivas a B. abortus fue de 13.6% a los tres meses de edad. De las 20 muestras de leche obtenidas de este hato se aisló B. abortus (100%). Mediante PCR se confirmó que estas cepas correspondían a cepas de campo y no a cepas vacunales. El hato 2, con 1800 vacas en producción, estaba inscrito en la campaña nacional contra la brucelosis animal y presentaba una seroprevalencia de 1.94% (35/1800) detectada de enero a diciembre de 2009. Se analizaron 1 170 registros usando los resultados de las pruebas de tarjeta y rivanol aplicada en becerras menores de tres meses de edad, de las que 24 (2.1%) resultaron positivas a B. abortus de enero de 2009 a junio de 2010. Se concluye que es necesario realizar el diagnóstico de brucelosis en becerras nacidas en establos donde se ha presentado la enfermedad, para prevenir que permanezcan animales positivos en el hato, ya que los anticuerpos posvacunales impedirán detectar la enfermedad, pero posteriormente se manifestará mediante abortos durante la primera gestación, perpetuando así la brucelosis en el establo.

Transmission of Brucella abortus to female calves from positive and negative cows was determined in the first week and third month of age. Two herds were used. Herd 1 consisted of 670 milking cows with a brucellosis seroprevalence of 21.6% (145/670). In this herd, groups of positive and negative cows were formed using the card and radial immunodifussion (RID) tests with native hapten. Blood samples were taken from female calves on two occasions: at one week of age and before animals were vaccinated against B. abortus. Of the 22 calves from the positive group, two (9.1%) were positive in the first week of life, but no more positive calves were found at three months of age. In the group of female calves born to negative cows, there were no positive animals at one week of age, but four out of 22 were found positive with the RID test at three months of age. A prevalence rate of 13.6% of positive calves for B. abortus in the third month of age was calculated. Twenty milk samples were obtained from this herd and B. abortus was isolated from all of them (100%). Using PCR, the strains found were confirmed to be field strains and not vaccine strains. Herd 2 consisted of 1800 milking cows, participating in the National Campaign against Animal Brucellosis, that had a seroprevalence of 1.94% (35/1800) detected from January to December 2009. In this herd, 1 170 records were analyzed using the results of the card and rivanol tests obtained from female calves younger than three months of age, of which 24 (2.1%) were found positive for B. abortus from January 2009 to June 2010. It is concluded that the diagnosis of brucellosis is necessary in female calves born in dairies to cows that have the disease, in order to prevent positive animals from remaining in the herd. Vaccine-induced antibodies will avert disease detection, but brucellosis will later manifest itself through abortions during first pregnancies, thus perpetuating the disease in dairies.

Isolation of a field strain of Brucella abortus from RB51-vaccinated- and brucellosis-seronegative bovine yearlings that calved normally.

A study was carried out in Pichucalco, Chiapas (Mexico) to determine whether recently calved cows or those that aborted shed Brucella. Serological diagnosis of brucellosis was made in all animals (209). Six of the cows that calved normally and two that aborted underwent a bacteriological study of milk and vaginal exudate. Brucella abortus was isolated from vaginal exudate samples in two 3- to 4-year-old seronegative first-birth cows that had calved normally. This was confirmed through bacteriological identification and PCR as a field strain and smooth phenotypes. We conclude that seronegative cows vaccinated with RB51 which calved normally and shed B. abortus in the vaginal exudate after calving could be a serious problem because these cows are overlooked in routine diagnoses and are a source of Brucella infection.