La minería como “locomotora” de la economía colombiana y su costo ambiental

RESUMEN: La preservación de la vida -la riqueza más preciada del planeta - solo se logra preservando sus recursos naturales no renovables. Cuando se afirma que la minería es una de las principales “locomotoras” de la economía Colombiana, o que el país debe “saber explotar sus recursos naturales de manera responsable y sostenible” sólo se están buscando beneficios económicos a corto plazo y su consiguiente conveniencia política, sin considerar las consecuencias generacionales que la minería ocasiona al destruir los ecosistemas. Es más, dado que los recursos minerales son no-renovables, es absurdo hablar de minería como una actividad “sostenible”

Resistencia de tres poblaciones de Rhipicephalus microplus a la ivermectina por el ensayo de inmersión de larvas

ABSTRACT: in Colombia, the control of tick infestation in cattle is almost exclusively performed with chemical acaricides. It is important to determine the degree of resistance of Riphicephalus microplus field populations to ivermectins (IVM) as the first step to design strategies to increase the useful life of acaricides and decrease the reliance on chemical controls. Objective: to test the degree of resistance to IVM. Methods: three cattle farms in Antioquia (Colombia) where IVM had previously failed to control infestations of R. microplus ticks were studied. Ticks were collected several months apart in 2013, and the larval immersion test (LIT) was performed on the progeny of the adult females. Concentration-mortality data were subjected to probit analysis. Results: the three populations showed lethal concentrations (LC) 50 and 99 of ≥ 30 ppm and ≥ 400 ppm, respectively. There was no difference observed in the LC at different times of collection for each population studied. Such high values for LC, together with very low regression slopes (≤ 2), indicated a very heterogeneous response to increasing concentrations of IVM, which is common for resistant populations. At two farms, subcutaneous injection with a long-acting formulation of IVM at a dosage of 630 μg/Kg was ineffective at eliminating existing infestations and protecting against reinfestations, confirming farmer suspicions of lost efficacy. Conclusion: epidemiological studies are necessary to assess the current status of resistance to IVM in this region of Colombia, and it is likely that the intensive use of IVM will aggravate this situation in the future.RESUMEN: en Colombia, el control de la infestación de garrapatas en el ganado se ha realizado casi exclusivamente con acaricidas químicos y es importante determinar el grado de resistencia de las poblaciones de campo de Riphicephalus microplus a ivermectinas (IVM) como el primer paso para diseñar tácticas que aumenten su vida útil y disminuyan la dependencia de los controles químicos. Objetivo: probar el grado de resistencia a IVM. Métodos: se evaluó la resistencia de R. microplus a IVM en tres fincas ganaderas en Antioquia (Colombia) donde se sospechaba que productos con IVM estaban fracasando para controlar infestaciones por garrapatas. Se recolectaron garrapatas con varios meses de diferencia durante el año 2013 y se empleó la prueba de inmersión de larvas (LIT) con la descendencia de las hembras adultas. Los datos de concentraciónmortalidad fueron sometidos a análisis probit. Resultados: los resultados para las tres poblaciones estudiadas mostraron concentraciones letales (LC) 50 y 99 de ≥ 30 ppm y ≥ 400 ppm, respectivamente. No se observó diferencia en las LC obtenidas en diferentes momentos de recogida para cada población estudiada. Los altos valores de LC, junto con pendientes muy bajas en las rectas de regresión (≤ 2), indicaron una respuesta muy heterogénea a concentraciones crecientes de IVM, propio de poblaciones resistentes. En dos de las granjas, la administración de inyecciones subcutáneas con una formulación de acción prolongada de la IVM a dosis de 630 μg/Kg fue incapaz de eliminar las infestaciones y proteger frente a reinfestaciones, confirmando las sospechas de los ganaderos de pérdida de eficacia. Conclusión: estudios epidemiológicos son necesarios para evaluar el estado actual de la resistencia a IVM en esta región de Colombia, y es probable que el uso intensivo de IVM agrave esta situación en el futuro

Complex interactions in microbial food webs : stoichiometric and functional approaches

The food web structure in some high mountain lakes deviates from the established tendency of high heterotrophic bacteria: phytoplankton biomass ratios in oligotrophic ecosystems. Thus, the microbial food web in La Caldera Lake is weakly developed, and bacteria constitute a minor component of the plankton community in terms of abundance, biomass and production. Autotrophic picoplankton is absent, and heterotrophic microbial food web is weakly developed compared to a grazing chain dominated by calanoid copepods and a phytoplankton community mainly composed of mixotrophic flagellates. In order to explain the singular food web structure of this lake, functional, stoichiometric and taxonomical approaches are followed to assess, on various temporal and spatial scales, the relevance of stressful abiotic factors (ultraviolet solar radiation and P-limitation) on the structure and functioning of this ecosystem. P-availability was the main factor controlling the algal biomass whereas bacterial P- limitation was a transient phenomenon. The algae-bacteria relationship was predominately commensalistic. In contrast to algae, full-sunlight radiation had no negative effect on bacterial growth but rather enhanced bacterial dependence on the carbon released by algae. The prevalence of the commensalistic-mutualistic relationship and the development of a more complex microbial food web were related to the stoichiometry of algae and bacteria (N:P ratios). The microbial food web only developed at balanced algal and bacterial N:P ratios, with the appearance of ciliates after a nutrient pulse. However, mixotrophic algae dominated the planktonic community under P-deficit conditions, and they were the main factor controlling bacterioplankton. Their regulatory effect has a dual nature: (i) a resource-based control, where bacteria depend on the photosynthetic carbon released by algae, i.e., a commensalistic interaction ("without you I cannot live"); and (ii) a predatory control, where bacteria is a prey for mixotrophs ("with you I die"). Hence, the niche of microheterotrophs (nanoflagellates and ciliates) is occupied by mixotrophs, and there is a resulting simplification of the planktonic structure. With respect to the carbon cycle, mixotrophic bacterivory constitutes a "by-pass" for the flux of C towards the grazing chain, precluding the development of a complex heterotrophic microbial food web. Mixotrophs thereby improve the energetic transfer efficiency in high mountain lakes through a reduction in the number of trophic levels. Antagonistic effects of UVR x P interactions on the algae-bacteria relationship were caused by an enhancement of dual (resource and predation) control. Based on these results, an alternative model for the flux of C in autotrophic high mountain lakes has been proposed.La estructura de la red trófica en algunos lagos de alta montaña, se aleja de los patrones establecidos para ecosistemas oligotróficos que proponen el predominio de la red trófica microbiana sobre la cadena de pastoreo. Así, en la laguna de La Caldera las bacterias son el componente minoritario de la comunidad planctónica en términos de abundancia, biomasa y producción. El picoplancton autótrofo está ausente y la red microbiana heterotrófica se encuentra escasamente desarrollada frente a una cadena de pastoreo dominada por copépodos calanoides y algas mixotróficas. Para comprender los mecanismos que determinan esta estructura trófica hemos seguido diferentes aproximaciones de análisis: funcional, estequiométrica y taxonómica sobre distintas escalas espaciales y temporales, en relación con los principales factores de estrés abiótico (radiación ultravioleta y limitación por fósforo) que controlan el funcionamiento de los ecosistemas de alta montaña. Nuestros resultados indican que la disponibilidad de fósforo, de forma generalizada, controla la biomasa algal y de manera transitoria la bacteriana, estableciéndose entre ambas comunidades una relación comensalista. La radiación solar completa no afecta negativamente el desarrollo de las bacterias y si el de las algas y potencia la relación de dependencia por el carbono orgánico (comensalismo) entre algas y bacterias. El predominio de la relación comensalista-mutualista y el desarrollo del bucle microbiano esta relacionado con la estequiometría (razón N:P) de algas y bacterias. Así, sólo cuando la razón N:P de algas y bacterias es equilibrada para crecer, un pulso de nutrientes permite el desarrollo del bucle microbiano. En condiciones naturales de déficit de P, sin embargo, existe un predominio de "algas" con metabolismo mixotrófico. Las algas mixotróficas ejercen un efecto regulador dual sobre las bacterias que denominamos Ni contigo ni sin ti, (i) control por depredación, donde las bacterias son consumidas por algas mixotróficas ("contigo me muero"), (ii) control basado en los recursos estableciéndose una relación de dependencia de las bacterias sobre del carbono liberado por las algas ("sin ti no puedo vivir"). La mixotrofia supone un simplificación en la cadena trófica microbiana, donde los mixótrofos ocupan el nicho potencial de nanoflagelados y ciliados. Desde un punto de vista energético implica un cortocircuito en el flujo de energía y un incremento en la eficiencia de transferencia energética en ecosistemas ultraoligotróficos y con alta dosis de radiación ultravioleta (RUV). Los efectos de la interacción entre RUV y pulsos de P tienen un efecto antagónico sobre la interacción alga-bacteria, intensificando la interacción comensal-depredadora. A partir de los resultados obtenidos proponemos un modelo alternativo de flujo de energía para ecosistemas autotróficos de alta montaña

Direct and indirect effects of vertical mixing, nutrients and ultraviolet radiation on the bacterioplankton metabolism in high-mountain lakes from southern Europe

As a consequence of global change, modifications in the interaction among abiotic stressors on aquatic ecosystems have been predicted. Among other factors, UVR transparency, nutrient inputs and shallower epilimnetic layers could alter the trophic links in the microbial food web. Currently, there are some evidences of higher sensitiveness of aquatic microbial organisms to UVR in opaque lakes. Our aim was to assess the interactive direct and indirect effects of UVR (through the excretion of organic carbon – EOC – by algae), mixing regime and nutrient input on bacterial metabolism. We performed in situ short-term experiments under the following treatments: full sunlight (UVR + PAR, >280 nm) vs. UVR exclusion (PAR only, >400 nm); ambient vs. nutrient addition (phosphorus (P; 30 μg PL−1) and nitrogen (N; up to final N : P molar ratio of 31)); and static vs. mixed regime. The experiments were conducted in three high-mountain lakes of Spain: Enol [LE], Las Yeguas [LY] and La Caldera [LC] which had contrasting UVR transparency characteristics (opaque (LE) vs. clear lakes (LY and LC)). Under ambient nutrient conditions and static regimes, UVR exerted a stimulatory effect on heterotrophic bacterial production (HBP) in the opaque lake but not in the clear ones. Under UVR, vertical mixing and nutrient addition HBP values were lower than under the static and ambient nutrient conditions, and the stimulatory effect that UVR exerted on HBP in the opaque lake disappeared. By contrast, vertical mixing and nutrient addition increased HBP values in the clear lakes, highlighting for a photoinhibitory effect of UVR on HBP. Mixed regime and nutrient addition resulted in negative effects of UVR on HBP more in the opaque than in the clear lakes. Moreover, in the opaque lake, bacterial respiration (BR) increased and EOC did not support the bacterial carbon demand (BCD). In contrast, bacterial metabolic costs did not increase in the clear lakes and the increased nutrient availability even led to higher HBP. Consequently, EOC satisfied BCD in the clear lakes, particularly in the clearest one [LC]. Our results suggest that the higher vulnerability of bacteria to the damaging effects of UVR may be particularly accentuated in the opaque lakes and further recognizes the relevance of light exposure history and biotic interactions on bacterioplankton metabolism when coping with fluctuating radiation and nutrient inputs.Fil: Durán, C.. Universidad de Granada; EspañaFil: Medina Sánchez, J. M.. Universidad de Granada; EspañaFil: Herrera, G.. Universidad de Granada; EspañaFil: Villar Argaiz , M.. Universidad de Granada; EspañaFil: Villafañe, Virginia Estela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Helbling, Eduardo Walter. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Carrillo, P.. Universidad de Granada; Españ

Asociación de los alelos BoLA-DRB3 y TLR4 con mastitis subclínica en vacas de Colombia

ABSTRACT: molecular markers for genetic resistance can be used to control mastitis in dairy cattle. The Major Histocompatibility Complex and the Toll-like receptor 4 (TLR4) are two promising genes that warrant investigation. Objective: to identify associations between genotypes of BoLA-DRB3 locus and T4CRBR2 fragment and subclinical mastitis (SM). Methods: 996 lactating cows from 32 herds comprising Holstein (80%), Holstein x Jersey cross (12.5%), and other crosses (7.5%) were evaluated monthly during two years, diagnosed for SM and genotyped for the second exon of BoLA DRB3 and the TLR4 coreceptor-binding region 2 (T4CRBR2) using a Polymerase chain reaction-restriction fragment length polymorphism technique (PCR-RFLP). The association between candidate alleles and subclinical mastitis was measured by logistic regression. Results: the most frequently observed alleles for BoLA-DRB3 were DRB3.2 *8, *22, *24, *16, *10, *23, *gba, *11, *2, *mbb, *jba, *3, and *15, accounting for 58.9% of the population. Frequencies for T4CRBR2 alleles A and B were 0.352 and 0.647, respectively. Based on 57,408 observations during the period, the mean SM prevalence was 16.2% (95% CI 13.0 and 19.4) per udder quarter and 37.6% (95% CI 32.1 and 43.2) per cow. The predominant microorganisms isolated from SM quarters were Streptococcus agalactiae and Coagulase-Negative Staphylococci (CNS). Allele DRB3.2 *23 was associated with SM occurrence and CNS infection. No alleles were associated with Streptococcus agalactiae infection. Allele *mbb was associated with occurrence of CNS infection and alleles *jba and *15 were associated with resistance to CNS infection. No significant relationship between T4CRBR2 and SM was observed. Conclusion: DRB3.2 gen may play an important role in the occurrence of SM and certain alleles may confer resistance to specific pathogens.RESUMEN: los marcadores moleculares genéticos de resistencia para mastitis bovina son una herramienta para el control de la enfermedad en rebaños lecheros. Los genes del Complejo Mayor de Histocompatibilidad y el Receptor tipo Toll 4 (TLR4) son dos genes candidatos promisorios que justifica investigar. Objetivo: identificar asociaciones entre los genotipos del locus BoLA-DRB3 y del fragmento T4CRBR2 con la ocurrencia de mastitis subclínica. Métodos: 996 vacas lactantes de 32 hatos de las razas Holstein (80%), Holstein x Jersey (12,5%) y otros cruces (7,5%), fueron visitadas mensualmente por dos años, diagnosticadas para mastitis subclínica y genotipificadas para el segundo exón del DRB3 y para la región 2 de unión al correceptor del TLR4 (T4CRBR2) por medio de las técnicas de Reacción en cadena de la polimerasa y de Longitud del polimorfismo del fragmento de restricción (PCR-RFLP). La asociación entre los alelos candidatos y la mastitis subclínica se midió por regresión logística. Resultados: los alelos más frecuentes para el DRB3.2 fueron *8, *22, *24, *16, *10, *23, *gba, *11, *2, *mbb, *jba, *3 y *15, que suman el 58,9% del total en la población. Las frecuencias para los alelos A y B del T4CRBR2 fueron de 0,352 y 0,647, respectivamente. Basados en 57.408 observaciones, la prevalencia de MS a nivel de cuarto fue 16,2% (95% IC 13,0 y 19,4) y a nivel de vaca fue de 37,6% (95% IC 32,1 y 43,2). Los microorganismos más frecuentes fueron Streptococcus agalactiae y Estafilococo Coagulasa Negativo (ECN). El alelo DRB3.2 *23 fue el más asociado con la ocurrencia de MS y con la infección por ECN. No se hallaron alelos asociados a infección con mastitis por Streptococcus agalactiae. Con respecto a la infección por ECN, el *mbb se asoció con la ocurrencia y los alelos *jba y *15 se asociaron con resistencia. No se observó asociación entre T4CRBR2 y MS. Conclusión: el gen DRB3.2 puede jugar un papel importante en la presencia de MS y ciertos alelos pueden conferir resistencia a patógenos específicos

Parálisis posterior en una vaca Holstein con Leucosis Enzoótica Bovina

ABSTRACT: A 6 year-old Holstein cow was euthanized after a 3 week course of progressive paraplegia. In spite of the increasing difficulties to rise and walk, the animal remained bright, alert, afebrile and with good appetite throughout most of the clinical course. Complete blood counts, biochemical profiles and analysis of the cerebrospinal fluid were reported within normal limits. Antibody was detected for bovine leukaemia virus using an enzyme-linked immunosorbent assay, supporting a tentative diagnosis of bovine leukosis. Post-mortem examination revealed a localized form of lymphosarcoma with few 2-5 cm nodular tumors confined to the walls of the gastrointestinal tract, particularly in the abomasum. In addition, soft grey tumors were found within the vertebral canal surrounding the lumbar spinal cord and associated nerve roots. Microscopic examination revealed the nodular masses were composed of neoplastic lymphocytes. Mass in the lumbar vertebral canal had extradural neoplastic lymphocytes infiltrating connective tissues around the spinal cord and spinal nerve roots. Unlike the more common chronic and wasting presentation of the disease with widespread lymphadenopathy, the rapid progression of the disease to total paraplegia in this animal could be explained by the localized presence of tumors in the spinal canal.RESUMEN: Una vaca Holstein de 6 años de edad fue sacrificada después de un curso de paraplejía progresiva de 3 semanas de duración. A pesar de las crecientes dificultades para levantarse y caminar, el animal se mantuvo alerta, sin fiebre y con buen apetito casi todo el transcurso de la enfermedad. Los análisis del hemograma, perfil bioquímico y líquido cefalorraquídeo no mostraron alteraciones fuera del rango normal. El análisis de ELISA frente al virus de la Leucosis Bovina resultó positivo, apoyando el diagnóstico diferencial de leucemia. El examen post-mortem reveló una forma localizada de linfosarcoma, con escasas y pequeñas tumoraciones nodulares de 2-5 cm confinadas a las paredes del tracto gastrointestinal, sobre todo en el abomaso. Además, los tumores estaban presentes en el canal vertebral rodeando la médula lumbar espinal y raíces nerviosas adyacentes. El examen microscópico reveló que las masas nodulares estaban compuestas de linfocitos neoplásicos; igualmente, el tejido conectivo rodeando la medula lumbar presentaba gran infiltración de dichos linfocitos. A diferencia de la presentación más corriente y crónica de la enfermedad en que existe un desgaste progresivo del animal asociado a una linfadenopatía generalizada, en este caso la rápida progresión de la enfermedad hacia una paraplejia total se podría explicar por la presencia de tumores localizados en el canal espinal

Nucleic Acid Content in Crustacean Zooplankton: Bridging Metabolic and Stoichiometric Predictions

Metabolic and stoichiometric theories of ecology have provided broad complementary principles to understand ecosystem processes across different levels of biological organization. We tested several of their cornerstone hypotheses by measuring the nucleic acid (NA) and phosphorus (P) content of crustacean zooplankton species in 22 high mountain lakes (Sierra Nevada and the Pyrenees mountains, Spain). The P-allocation hypothesis (PAH) proposes that the genome size is smaller in cladocerans than in copepods as a result of selection for fast growth towards P-allocation from DNA to RNA under P limitation. Consistent with the PAH, the RNA:DNA ratio was >8-fold higher in cladocerans than in copepods, although ‘fast-growth’ cladocerans did not always exhibit higher RNA and lower DNA contents in comparison to ‘slow-growth’ copepods. We also showed strong associations among growth rate, RNA, and total P content supporting the growth rate hypothesis, which predicts that fast-growing organisms have high P content because of the preferential allocation to P-rich ribosomal RNA. In addition, we found that ontogenetic variability in NA content of the copepod Mixodiaptomus laciniatus (intra- and interstage variability) was comparable to the interspecific variability across other zooplankton species. Further, according to the metabolic theory of ecology, temperature should enhance growth rate and hence RNA demands. RNA content in zooplankton was correlated with temperature, but the relationships were nutrient-dependent, with a positive correlation in nutrient-rich ecosystems and a negative one in those with scarce nutrients. Overall our results illustrate the mechanistic connections among organismal NA content, growth rate, nutrients and temperature, contributing to the conceptual unification of metabolic and stoichiometric theories.This research was supported by the Spanish Ministries of Science and Innovation (CGL2011-23681/BOS), and Environment, Rural and Marine Affairs (OAPN2009/067); ‘Consejería de Innovación, Ciencia y Empresa – Junta de Andalucía’ (Excelencia CVI-02598; P09-RNM-5376); The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS) and Stockholm University’s strategic marine environmental research program ‘Baltic Ecosystem Adaptive Management’, and a Spanish government ‘Formación de Profesorado Universitario’ fellowship to F.J. Bullejos

Prevalencia de parásitos gastrointestinales en equinos y factores de riesgo asociados en varias zonas de Antioquia, Colombia

ABSTRACT: There are few reports on the prevalence of gastrointestinal parasites in equines in Colombia. In this study, 946 horses were sampled from a total of 204 farms in the municipalities of Rionegro and those that comprise the Valle de Aburrá, in the department of Antioquia. Fecal samples were taken directly from the rectum and processed by the McMaster, Baermann and Graham techniques. The prevalence of parasites at the farm level was 56.3% for Strongylidae, 10.7% for Strongyloides spp, 2.8% for Oxyuridae and 0.3% for Dictyocaulus spp. From a practical point of view, the most pathogenic parasites and of greatest resistance concern were the Cyathostomids, which are included within the Strongylidae and whose prevalence was greater than 50%. The OR of presenting Strongylidae was 49% lower in equines that participated in fairs compared to those that did not. The OR of presenting Strongylidae was 56% lower in equines that use stables than those not being stalled. Also, the OR of being positive to Oxyuris equi was 88% lower in animals that participate in fairs compared to those that did not, and was 3.66 times higher in equines with body condition ≤ 2 in comparison with those of body condition ≥3. Based on this information, it is important to initiate studies that evaluate the state of antihelminthic resistance and the relationship between parasitic load and clinical condition in order to determine the real impact of these parasites on the equines of these regions.RESUMEN: Existen pocos reportes de la prevalencia de parásitos gastrointestinales en equinos en Colombia. En este estudio se muestrearon 946 caballos de un total de 204 predios en los municipios de Rionegro y los que comprenden el Valle de Aburra departamento de Antioquia. La materia fecal fue tomada directamente del recto y procesada por las tecnicas de McMaster, Baermann y Graham. La prevalencia de parásitos a nivel de predios fue del 56,3% para Strongylidae, 10,7% para Strongyloides spp, 2,8% para Oxyuridae y 0,3% para Dictyocaulus spp. Desde el punto de vista práctico, los más patogénicos y de mayor problema de resistencia son los Cyathostomidos, que se incluyen dentro de los Strongylidae y cuya prevalencia fue superior al 50%. El OR de presentar Strongylidae es 49% menor en equinos que participan en ferias en comparación con los que no lo hacen. El OR de presentar Strongylidae es 56% menor en equinos que usan pesebrera en comparación con los que no la usan. Por su parte, el OR de ser positivo a Oxyuris equi es 88% menor en animales que salen a ferias en comparación con los que no salen a feria y el OR de ser positivo a Oxyuris equi es 3,66 veces mayor en equinos con condición corporal ≤2 en comparación con equinos de condición corporal ≥3. Con base en esta información es importante iniciar estudios de resistencia a antihelminticos y evaluar la relación entre la carga parasitaria y las posibles afecciones clínicas para así determinar el impacto real de estas parasitosis en los equinos de estas regiones

Prevalence of Babesia Caballi, Theileria Equi and Trypanosomiasis and analysis of risk factors in horses of Antioquia, Colombia

ABSTRACT: This research was carried out due to the little existing national information on equine hemoparasites; the objective was to determine babesiosis and trypanosomiasis prevalence in the Aburrá Valley and Rionegro Antioquia (Colombia) as well as some risk factors associated with the seropositivitie of these diseases. In 223 lots with a population of 1.008 equine venous blood sample was taken for serological diagnosis and molecular. Epidemiological information was obtained through the application of a survey addressed to persons in charge of the animals. For the statistical analysis, Chi square of independence or Fisher’s Exact Test was applied when necessary. For the bivariate associations, risk estimates (OR) were calculated by explanatory variable, with their respective 95% confidence intervals (95% CI).It was found a prevalence of 11.9% for babesiosis and 1.9% for trypanosomiasis and as protection factor found the fact of going to trade fairs. Geographic location, sex and being neutered, be positive for Equine Infectious Anemia (AIE), strongyles or oxiurus was a risk factor for piroplasmosis. For Trypanosomiasis the risk factor was to be infested with ticks Dermacentor nitens or be mule. Methods of active epidemiological surveillance should be reinforced, especially in cases of continuous mobilization of equines or development of events that involve massive presence of horses.RESUMEN: La investigación se llevó a cabo debido a la poca información nacional existente en hemoparásitos equinos y su objetivo fue determinar la prevalencia de babesiosis y tripanosomiasis, en el Valle de Aburrá y Rionegro, municipios de Antioquia (Colombia), así como algunos factores de riesgo asociados a la presentación de seropositividad, a estas enfermedades. En 223 predios, con una población de 1.008 equinos, se tomó muestra de sangre venosa, para realizar el diagnóstico serológico y molecular. La información epidemiológica fue obtenida a través de la aplicación de una encuesta dirigida a las personas a cargo de los animales. Para el análisis estadístico, se aplicó Chi cuadrado de independencia y la Prueba Exacta de Fisher, cuando fue necesario. Para las asociaciones bivariadas, se calcularon estimaciones del riesgo (OR) por variable explicativa, con sus respectivos intervalos de confianza, del 95% (I.C. 95%). Se encontró una prevalencia del 11,9%, para babesiosis y de 1,9%, para tripanosomiasis; como factor de protección, se encontró el hecho de salir a una feria. Para la piroplasmosis, el lugar geográfico, el sexo, estar castrado, ser positivos a Anemia Infecciosa Equina (AIE), estrongilidos u oxiurus fueron factores de riesgo. Para tripanosomiasis, el factor de riesgo fue estar infestado con Dermacentor nitens o ser mular. Se deben reforzar métodos de vigilancia epidemiológica activa, sobre todo, en casos de movilización continua de equinos o desarrollo de eventos, que involucren presencia masiva de ejemplares

Maximum in the Middle: Nonlinear Response of Microbial Plankton to Ultraviolet Radiation and Phosphorus

The responses of heterotrophic microbial food webs (HMFW) to the joint action of abiotic stressors related to global change have been studied in an oligotrophic high-mountain lake. A 2×5 factorial design field experiment performed with large mesocosms for >2 months was used to quantify the dynamics of the entire HMFW (bacteria, heterotrophic nanoflagellates, ciliates, and viruses) after an experimental P-enrichment gradient which approximated or surpassed current atmospheric P pulses in the presence vs. absence of ultraviolet radiation. HMFW underwent a mid-term (<20 days) acute development following a noticeable unimodal response to P enrichment, which peaked at intermediate P-enrichment levels and, unexpectedly, was more accentuated under ultraviolet radiation. However, after depletion of dissolved inorganic P, the HMFW collapsed and was outcompeted by a low-diversity autotrophic compartment, which constrained the development of HMFW and caused a significant loss of functional biodiversity. The dynamics and relationships among variables, and the response patterns found, suggest the importance of biotic interactions (predation/parasitism and competition) in restricting HMFW development, in contrast to the role of abiotic factors as main drivers of autotrophic compartment. The response of HMFW may contribute to ecosystem resilience by favoring the maintenance of the peculiar paths of energy and nutrient-mobilization in these pristine ecosystems, which are vulnerable to threats by the joint action of abiotic stressors related to global change.This research was supported by Junta de Andalucía (Excelencia P07-CVI-02598 to PC, and P09-RNM-5376 to JMMS), the Spanish Ministries of Medio Ambiente, Rural y Marino (PN2009/067 to PC) and Ciencia e Innovación (GLC2008-01127/BOS and CGL2011-23681 to PC), the ERC Advanced Grant project number 250254 “MINOS” (to GB), and two Spanish government grants (to JADM and FJB)