Person: Álvarez Sánchez, Julio
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First Name
Julio
Last Name
Álvarez Sánchez
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Veterinaria
Department
Sanidad Animal
Area
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17 results
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Item Epidemiological investigation of bovine tuberculosis herd breakdowns in Spain 2009/2011(PLoS ONE, 2014) Guta, Sintayehu; Casal, Jordi; Napp, Sebastian; Saez, Jose Luis; Garcia Saenz, Ariadna; Perez de Val, Bernat; Romero Martínez, Beatriz; Alvarez, Julio; Allepuz, Alberto; Álvarez Sánchez, JulioWe analyzed the most likely cause of 687 bovine tuberculosis (bTB) breakdowns detected in Spain between 2009 and 2011 (i.e., 22% of the total number of breakdowns detected during this period). Seven possible causes were considered: i) residual infection; ii) introduction of infected cattle from other herds; iii) sharing of pastures with infected herds; iv) contiguous spread from infected neighbor herds; v) presence of infected goats in the farm; vi) interaction with wildlife reservoirs and vii) contact with an infected human. For each possible cause a decision tree was developed and key questions were included in each of them. Answers to these key questions lead to different events within each decision tree. In order to assess the likelihood of occurrence of the different events a qualitative risk assessment approach was used. For this purpose, an expert opinion workshop was organized and ordinal values, ranging from 0 to 9 (i.e., null to very high likelihood of occurrence) were assigned. The analysis identified residual infection as the most frequent cause of bTB breakdowns (22.3%; 95%CI: 19.4-25.6), followed by interaction with wildlife reservoirs (13.1%; 95%CI: 10.8-15.8). The introduction of infected cattle, sharing of pastures and contiguous spread from infected neighbour herds were also identified as relevant causes. In 41.6% (95%CI: 38.0-45.4) of the breakdowns the origin of infection remained unknown. Veterinary officers conducting bTB breakdown investigations have to state their opinion about the possible cause of each breakdown. Comparison between the results of our analysis and the opinion from veterinary officers revealed a slight concordance. This slight agreement might reflect a lack of harmonized criteria to assess the most likely cause of bTB breakdowns as well as different perceptions about the importance of the possible causes. This is especially relevant in the case of the role of wildlife reservoirs.Item Epidemiological factors associated with the exposure of cattle to Coxiella burnetii in the Madrid region of Spain(The Veterinary Journal, 2012) Álvarez Sánchez, Julio; Perez, A.; Mardones, F.O.; Pérez Sancho, Marta; García-Seco Romero, María Teresa; Pagés, E.; Mirat, F.; Díaz, R.; Carpintero, J.; Domínguez Rodríguez, Lucas JoséDomestic ruminants are considered to be the major source of Coxiella burnetii, the causative agent of Q fever. Even though Q fever is considered to be present worldwide, its distribution in many areas and countries remains unknown. Here, a serological assay was used to estimate the seroprevalence of C. burnetii in cattle in the Madrid region of Spain, to assess its spatial distribution, and to identify risk factors associated with positive results. Ten animals from each of 110 herds (n=1100) were randomly selected and analyzed using an ELISA test. In addition, epidemiological information, at both the herd and individual level, was collected. Variables for which an association with test results was detected in a bivariate analysis were included as predictors (main effects) in a multivariable logistic regression model. Herd and individual seroprevalences were 30% (95% CI=22.2-39.1) and 6.76% (95% CI=5.42-8.41), respectively, and a strong spatial dependence was identified at the first neighbour level using the Cuzick-Edwards test. Production type (dairy >beef >bullfighting) and age of animals (old vs. young) were the only variables significantly associated (P<0.05) with positive serological results at the herd and individual levels, respectively. These results indicate that cattle are exposed to C. burnetii in the Madrid region The high herd seroprevalence found in dairy herds (75%) indicates a higher risk of infection (probably for management reasons) whereas no C. burnetii positive bullfighting herds were identified.Item Los Oligoquetos terrícolas de la Península Ibérica(2015) Álvarez Sánchez, JulioItem Eradication of bovine tuberculosis at a herd-level in Madrid, Spain: study of within-herd transmission dynamics over a 12 year period(BMC veterinary research, 2012) Alvarez, Julio; Perez, Andres M; Bezos Garrido, Javier; Casal, Carmen; Romero Martínez, Beatriz; Rodriguez Campos, Sabrina; Saez Llorente, Jose L; Diaz, Rosa; Carpintero, Jesus; Juan Ferré, Lucía De; Álvarez Sánchez, Julio; Domínguez Rodríguez, Lucas JoséBACKGROUND Eradication of bovine tuberculosis (bTB) through the application of test-and-cull programs is a declared goal of developed countries in which the disease is still endemic. Here, longitudinal data from more than 1,700 cattle herds tested during a 12 year-period in the eradication program in the region of Madrid, Spain, were analyzed to quantify the within-herd transmission coefficient (β) depending on the herd-type (beef/dairy/bullfighting). In addition, the probability to recover the officially bTB free (OTF) status in infected herds depending on the type of herd and the diagnostic strategy implemented was assessed using Cox proportional hazard models. RESULTS Overall, dairy herds showed higher β (median 4.7) than beef or bullfighting herds (2.3 and 2.2 respectively). Introduction of interferon-gamma (IFN-γ) as an ancillary test produced an apparent increase in the β coefficient regardless of production type, likely due to an increase in diagnostic sensitivity. Time to recover OTF status was also significantly lower in dairy herds, and length of bTB episodes was significantly reduced when the IFN-γ was implemented to manage the outbreak. CONCLUSIONS Our results suggest that bTB spreads more rapidly in dairy herds compared to other herd types, a likely cause being management and demographic-related factors. However, outbreaks in dairy herds can be controlled more rapidly than in typically extensive herd types. Finally, IFN-γ proved its usefulness to rapidly eradicate bTB at a herd-level.Item Comparison of depopulation and S19‐RB51 vaccination strategies for control of bovine brucellosis in high prevalence areas(Veterinary Record, 2014) Saez, J. L.; Sanz, C.; Durán, M.; García, P.; Fernández, F.; Minguez, O.; Carbajo, L.; Mardones, F.; Perez, A.; González Domínguez, Sergio; Domínguez Rodríguez, Lucas José; Álvarez Sánchez, JulioRB51 vaccination can minimise the diagnostic problems associated with S19 vaccination of adult cattle, but its use for bovine brucellosis (BB) control remains controversial. Here, the evolution of BB prevalence in five high prevalence areas in Spain subjected to different control measures is described: herd depopulation of infected herds (I–III) or mass vaccination with RB51 and S19‐RB51 vaccination of replacement heifers (IV–V). Annual data from the eradication campaigns were analysed at the special incidence area (SIA) level and the time to obtain herd prevalence levels of <1 per cent (‘controlled status’) was obtained at the local veterinary unit (LVU) level and compared using Cox's proportional hazard model. A higher annual rate of decrease in herd prevalence was observed in the SIAs subjected to vaccination (46.9%, 95% CI 43.5% to 50.0%) compared with those managed using stamping out (14.9%, 95% CI 9.6% to 19.9%). No significant differences in the time to achieve controlled status were observed between the stamping‐out and vaccination strategies used at the LVU level, with median times of 60 (stamping‐out LVUs) and 63 (vaccination LVUs) months. These results suggest that RB51 mass vaccination, in combination with the S19‐RB51 vaccination of replacement heifers and strict implementation of other eradication measures, may provide results at least comparable with those resulting from a herd depopulation based strategy.Item Spatial dynamics of bovine tuberculosis in the Autonomous Community of Madrid, Spain (2010-2012)(PLoS ONE, 2014) Cruz Conty, Maria Luisa de la; Perez, Andres; Bezos Garrido, Javier; Pages, Enrique; Casal, Carmen; Carpintero, Jesus; Romero Martínez, Beatriz; Barker, Christopher M; Diaz, Rosa; Álvarez Sánchez, Julio; Domínguez Rodríguez, Lucas JoséProgress in control of bovine tuberculosis (bTB) is often not uniform, usually due to the effect of one or more sometimes unknown epidemiological factors impairing the success of eradication programs. Use of spatial analysis can help to identify clusters of persistence of disease, leading to the identification of these factors thus allowing the implementation of targeted control measures, and may provide some insights of disease transmission, particularly when combined with molecular typing techniques. Here, the spatial dynamics of bTB in a high prevalence region of Spain were assessed during a three year period (2010-2012) using data from the eradication campaigns to detect clusters of positive bTB herds and of those infected with certain Mycobacterium bovis strains (characterized using spoligotyping and VNTR typing). In addition, the within-herd transmission coefficient (β) was estimated in infected herds and its spatial distribution and association with other potential outbreak and herd variables was evaluated. Significant clustering of positive herds was identified in the three years of the study in the same location ("high risk area"). Three spoligotypes (SB0339, SB0121 and SB1142) accounted for >70% of the outbreaks detected in the three years. VNTR subtyping revealed the presence of few but highly prevalent strains within the high risk area, suggesting maintained transmission in the area. The spatial autocorrelation found in the distribution of the estimated within-herd transmission coefficients in herds located within distances <14 km and the results of the spatial regression analysis, support the hypothesis of shared local factors affecting disease transmission in farms located at a close proximity.Item Assessment of the sensitivity of the bovine tuberculosis eradication program in a high prevalence region of Spain using scenario tree modeling(Preventive Veterinary Medicine, 2019) De la Cruz, María Luisa; Pozo Piñol, Pilar; Grau, Anna; Nacar, Jesús; Bezos Garrido, Javier; Pérez, Andrés; Domínguez Rodríguez, Lucas José; Sáez, José Luís; Mínguez-González, Olga; Juan Ferré, Lucía De; Álvarez Sánchez, JulioIn spite of the efforts invested to eradicate bovine tuberculosis (bTB) in cattle, the disease is still present in several developed countries, including Spain. Among the factors related with disease persistence in high prevalence areas, the lack of sensitivity of the screening test for detection of infected herds [single intradermal tuberculin (SIT) test] can play a major role. Here, a scenario tree model mimicking the diagnostic test scheme in place in the region of Castilla y Leon (Spain) was developed to estimate the probability of detecting bTB in an infected-non detected officially tuberculosis free (OTF) herd (herd sensitivity, HSe). In order to do so the probability of detecting at least one positive animal in the SIT test with/without post-mortem (detection of lesions and culture) confirmation in an infected herd was estimated using Monte Carlo simulation through @ RISK (Palisade Co, NY, USA). Uncertainty on the accuracy of the diagnostic tests was introduced in the model using distributions based on the literature. The performance of the model was evaluated by comparing the predicted number of SIT/post-mortem positive animals in infected herds with those observed in newly detected bTB-infected herds in the region in 2011–2015. The estimated HSe of the SIT test was 76.2% (95% probability interval: 19.8–97.6). According to the model, bTB infection would be then confirmed through culture in 65.3% (95% PI: 50.0–82.3) of the herds detected through the SIT test, so that overall the proportion of infected-non detected OTF herds in which the infection could be confirmed after the initial SIT test was 49.6% (95% PI: 9.75–80.3). The predicted HSe of both SIT test and culture was directly correlated with herd size. Results from the model suggest a moderate but highly variable HSe of the current surveillance system in place for bTB detection in OTF herds located in high prevalence areas, that could be maximized by performing multiple tests within a year as indicated in the Spanish eradication program (with a median SIT HSe of 87% when two consecutive tests were considered). In addition, these results highlight the usefulness of performing subsequent SIT tests to rule out infection in SIT-positive herds even when the causative agent cannot be isolated.Item Risk factors associated with negative in-vivo diagnostic results in bovine tuberculosis-infected cattle in Spain(BMC veterinary research, 2014) Álvarez Sánchez, Julio; Perez, Andrés; Marqués, Sergio; Bezos Garrido, Javier; Grau, Anna; Cruz Conty, Maria Luisa de la; Romero Martínez, Beatriz; Saez, Jose Luis; del Rosario Esquivel, Maria; Martínez, Maria del Carmen; Mínguez, Olga; Juan Ferré, Lucía De; Domínguez Rodríguez, Lucas JoséBACKGROUND Despite great effort and investment incurred over decades to control bovine tuberculosis (bTB), it is still one of the most important zoonotic diseases in many areas of the world. Test-and-slaughter strategies, the basis of most bTB eradication programs carried out worldwide, have demonstrated its usefulness in the control of the disease. However, in certain countries, eradication has not been achieved due in part to limitations of currently available diagnostic tests. In this study, results of in-vivo and post-mortem diagnostic tests performed on 3,614 animals from 152 bTB-infected cattle herds (beef, dairy, and bullfighting) detected in 2007-2010 in the region of Castilla y León, Spain, were analyzed to identify factors associated with positive bacteriological results in cattle that were non-reactors to the single intradermal tuberculin test, to the interferon-gamma (IFN-γ) assay, or to both tests applied in parallel (Test negative/Culture + animals, T-/C+). The association of individual factors (age, productive type, and number of herd-tests performed since the disclosure of the outbreak) with the bacteriology outcome (positive/negative) was analyzed using a mixed multivariate logistic regression model. RESULTS The proportion of non-reactors with a positive post-mortem result ranged from 24.3% in the case of the SIT test to 12.9% (IFN-γ with 0.05 threshold) and 11.9% (95% CI 9.9-11.4%) using both tests in parallel. Older (>4.5 years) and bullfighting cattle were associated with increased odds of confirmed bTB infection by bacteriology, whereas dairy cattle showed a significantly lower risk. Ancillary use of IFN-γ assay reduced the proportion of T-/C + animals in high risk groups. CONCLUSIONS These results demonstrate the likelihood of positive bacteriological results in non-reactor cattle is influenced by individual epidemiological factors of tested animals. Increased surveillance on non-reactors with an increased probability of being false negative could be helpful to avoid bTB persistence, particularly in chronically infected herds. These findings may aid in the development of effective strategies for eradication of bTB in Spain.Item Assessment of genetic diversity of zoonotic Brucella spp. recovered from livestock in Egypt using multiple locus VNTR analysis(BioMed research international, 2014) Menshawy, Ahmed M S; Hosein, Hosein I; García Benzaquén, Nerea; Martínez Alares, Irene; Sayour, Ashraf E; Goyache Goñi, Joaquín; Azzam, Ragab A A; Álvarez Sánchez, Julio; Domínguez Rodríguez, Lucas José; Pérez Sancho, Marta; García-Seco Romero, María Teresa; Pérez Sancho, MartaBrucellosis is endemic in most parts of Egypt, where it is caused mainly by Brucella melitensis biovar 3, and affects cattle and small ruminants in spite of ongoing efforts devoted to its control. Knowledge of the predominant Brucella species/strains circulating in a region is a prerequisite of a brucellosis control strategy. For this reason a study aiming at the evaluation of the phenotypic and genetic heterogeneity of a panel of 17 Brucella spp. isolates recovered from domestic ruminants (cattle, buffalo, sheep, and goat) from four governorates during a period of five years (2002-2007) was carried out using microbiological tests and molecular biology techniques (PCR, MLVA-15, and sequencing). Thirteen strains were identified as B. melitensis biovar 3 while all phenotypic and genetic techniques classified the remaining isolates as B. abortus (n = 2) and B. suis biovar 1 (n = 2). MLVA-15 yielded a high discriminatory power (h = 0.801), indicating a high genetic diversity among the B. melitensis strains circulating among domestic ruminants in Egypt. This is the first report of the isolation of B. suis from cattle in Egypt which, coupled with the finding of B. abortus, suggests a potential role of livestock as reservoirs of several zoonotic Brucella species in the region.Item Evaluation of the sensitivity and specificity of bovine tuberculosis diagnostic tests in naturally infected cattle herds using a Bayesian approach(Veterinary Microbiology, 2012) Álvarez Sánchez, Julio; Perez, Andrés; Bezos Garrido, Javier; Marqués, Sergio; Grau, Anna; Saez, Jose Luis; Mínguez, Olga; Juan Ferré, Lucía De; Domínguez Rodríguez, Lucas JoséTest-and-slaughter strategies have been the basis of bovine tuberculosis (BT) eradication programs worldwide; however, eradication efforts have not succeeded in certain regions, and imperfect sensitivity and specificity of applied diagnostic techniques have been deemed as one of the possible causes for such failure. Evaluation of tuberculosis diagnostic tools has been impaired by the lack of an adequate gold standard to define positive and negative individuals. Here, a Bayesian approach was formulated to estimate for the first time sensitivity (Se) and specificity (Sp) of the tests [single intradermal tuberculin (SIT) test, and interferon-gamma (IFN-γ) assay] currently used in Spain. Field data from the first implementation of IFN-γ assay (used in parallel with SIT test 2-6months after a first disclosure SIT test) in infected beef, dairy and bullfighting cattle herds from the region of Castilla and Leon were used for the analysis. Model results suggested that in the described situation: (i) Se of SIT test was highly variable (40.1-92.2% for severe interpretation, median=66-69%), and its Sp was high (>99%) regardless interpretation criteria; (ii) IFN-γ assay showed a high Se (median=89-90% and 83.5% for 0.05 and 0.1 cut-off points respectively) and an acceptable Sp (85.7% and 90.3% for 0.05 and 0.1 thresholds) and (iii) parallel application of both tests maximized the combined Se (95.6% using severe SIT and 0.05 cut-off point in the IFN-γ assay). These results support the potential use of the IFN-γ assay as an ancillary technique for routine BT diagnosis.