Monitoring of Rabbit Hemorrhagic Disease Virus in European Wild Rabbit (Oryctolagus cuniculus) Populations by PCR Analysis of Rabbit Fecal Pellets.

European rabbits (Oryctolagus cuniculus) are affected by rabbit hemorrhagic disease (RHD), which is caused by a lagovirus responsible for significant mortality in European wild rabbit populations. Our study aimed to evaluate the potential for detecting viral RNA by duplex real-time PCR in rabbit fecal pellets collected in the field, as a noninvasive method to monitor RHD virus circulation in wild populations. To do this, monthly discoveries of rabbits that died from RHD and detection of viral RNA in fecal pellets were recorded in two enclosed populations of wild rabbits throughout a year. The results suggested a low performance of this procedure to monitor viral infection incidence and a weak concordance with monthly discoveries of rabbits that died from RHD. This poor association was probably due to the low amount of viral RNA in feces, the prolonged time of excretion after infection, and that the number of rabbits found dead from RHD does not necessarily correlate with RHD incidence. Nevertheless, this procedure may be a complementary noninvasive method to assist in determining the presence of RHD viruses in populations. Additional research is needed to determine the suitability of this methodology to perform epidemiologic surveys on wild populations of European rabbits and, especially, other European or North American lagomorph species affected by lagoviruses.

Changes in European wild rabbit population dynamics and the epidemiology of rabbit haemorrhagic disease in response to artificially increased viral transmission.

European wild rabbit (Oryctolagus cuniculus) populations are severely affected by rabbit haemorrhagic disease (RHD), currently aggravated by the spread of the new lagovirus serotype RHDV2 that replaced the classical RHDV strains (RHDV/RHDVa). This virus causes high mortality in both adult and young rabbits and to date, there is no management tool to effectively reduce its impact on wild rabbit populations. This hinders the success of common strategies, such as habitat management or restocking, in areas where rabbits are native. However, the present study, conducted on enclosed wild rabbit populations, showed that spreading RHDV2 on baits during breeding periods induced infection of young rabbits, reducing mortality rates, presumably due to maternal antibody protection. This reduced the young rabbit mortality hazard by a third, and more juvenile rabbits immune to RHDV2 were recruited into the adult breeding population. Young rabbits from populations in which the force of infection of RHDV2 was increased, however, exhibited considerably higher susceptibility to infection by RHDV than those from non-treated control populations. Since co-circulation of classical RHDVs was ruled out, differences in the type and degree of immunization, the level of cross-protection and/or other unknown factors, such as the circulation of undetected non-pathogenic lagoviruses, arose as possible explanations. This meant that although the present study demonstrated the possibility of successfully modulating the impact of RHD in wild populations, the epidemiological complexity of the situation where several lagoviruses circulate requires additional research to determine final applicability of the proposed method.

Infectivity of rabbit haemorrhagic disease virus excreted in rabbit faecal pellets.

Rabbit haemorrhagic disease (RHD) is caused by a lagovirus affecting European rabbits (Oryctolagus cuniculus). Viral RNA is detected in tissues or faeces of convalescent rabbits, suggesting persistent infections; however, this RNA has not been shown to be related to infective viruses to date. In the present work, seven laboratory rabbits were challenged with the RHDV2/b virus variant. Viral RNA was individually detected by duplex qPCR in faeces collected for four weeks after infection, and the infective capacity of viral RNA excreted in the faeces of surviving rabbits was tested by challenging new rabbits with faecal inocula. As results, viral RNA was detected in faeces until the end of the assay. Viral RNA detected in the fourth week was infective only in the case of one rabbit that did not exhibit clear seroconversion, suggesting persistent infection as a result of an impaired immune response. Since the surviving rabbits were apparently healthy individuals, the importance of detecting carriers and the correct management of faeces to control RHD outbreaks in rabbitries are highlighted.

Assessment of targeted selective treatment criteria to control subclinical gastrointestinal nematode infections on sheep farms.

Control of sheep gastrointestinal nematode (GIN) infections mostly relies on the use of anthelmintics. Refugia-based control strategies as targeted selective treatments (TST) can delay anthelmintic resistance development, but the optimal decision criteria for selecting individuals to be treated in subclinical infection scenarios remain unclear. The present study aimed to evaluate the suitability of body condition score (BCS) and faecal egg counts (FEC) as treatment indicators and to determine their optimized threshold values for treatment in TST by determining the relationships of BCS, FEC and anthelmintic treatment with several productive parameters in pre-mating and pre-partum periods at an individual level. Deworming in pre-mating period increased BCS gain, but its magnitude was directly associated with strongyle FEC before treatment. Deworming also increased fertility in ewes with BCS < 2.75 and the proportion of lambing ewes that got pregnant during the first ovulation cycle. Nevertheless, treatment did not yield productive benefits in ewes with higher BCS values. On the other hand, deworming in the pre-partum lowered lamb peri-partum mortality and increased lamb weight at birth and the growth of lambs during lactation, especially in lambs born from ewes with strongyle FEC > 400 epg before treatment. These results showed that FEC and especially BCS can be potential decision criteria for the implementation of TST in these types of scenarios. The TST scheme derived from the present results on the control of GIN infections should include anthelmintic treatment of ewes with BCS lower than ≈ 3 approximately five weeks before mating and lambing. In the pre-lambing period, treatment may be unnecessary if flock mean strongyle FEC is lower than ≈ 200 epg, as the proportion of ewes with individual FEC > 400 epg would be very low. The results suggest that implementation of this TST scheme would provide benefits, such as the improvement of productivity, a rational management of parasites in refugia, and preservation of future efficacy of anthelmintics, in comparison to traditional deworming schemes.

Detection of Rabbit Hemorrhagic Disease Virus GI.2/RHDV2/b in the Mediterranean Pine Vole ( Microtus duodecimcostatus) and White-Toothed Shrew ( Crocidura russula).

The European wild rabbit ( Oryctolagus cuniculus) is a key prey species on the Iberian Peninsula, and several predator species that are at risk of extinction are dependent on them as prey. A new rabbit hemorrhagic disease (RHD) virus genotype (GI.2/RHDV2/b) emerged in 2010 and posed a threat to wild rabbit populations. During a survey aimed at investigating RHD epidemiology in wild rabbits, GI.2/RHDV2/b was detected by duplex real-time PCR in carcasses of one Mediterranean pine vole ( Microtus duodecimcostatus) and two white-toothed shrews ( Crocidura russula). Laboratory New Zealand white rabbits that were challenged with inocula obtained from the liver of the small mammals died showing RHD lesions, confirming the infectiousness of the isolates. Phylogenetic analysis of the VP60 gene nucleotide sequences showed complete homology between the isolates from the two small mammal species and a high degree of similarity, but not complete homology, to GI.2/RHDV2/b sequences from wild rabbits. The GI.2/RHDV2/b genotype has not been reported in species outside the order Lagomorpha.

Preferences of Pet Owners in Regard to the Use of Insecticides for Flea Control.

A survey conducted from 2002 to 2012 of 759 customers from 84 veterinary practices allows us to examine the habits of dog and cat owners regarding the use of insecticides for flea control. The results indicate that the percentage of animals treated during the 12 mo prior to the survey was not very high (71% in dogs and 50% in cats), considering that 100% of animals included in the study were flea-infested. Statistical analysis shows that animals older than 4 mo are treated more frequently and that dogs are more likely to be treated than cats. Among cats, those living in houses with gardens or farms are treated at a higher rate than those that live in houses without gardens or in flats. The main variable associated with the degree of satisfaction and product loyalty is the active ingredient, and the choice of a commercial product is generally associated with high-efficacy products. The mode of application of a flea treatment does not seem to have a strong influence on pet owner satisfaction or loyalty. Likewise, we do not find a clear correlation between owners' satisfaction and loyalty, so pet owners may find the results of the selected product more or less satisfactory for reasons other than simple effectiveness. Finally, because of the complexity of the life cycle of these ectoparasites, the importance of the advice of a veterinarian when planning flea control is emphasized.

Rabbit haemorrhagic disease: Cross-protection and comparative pathogenicity of GI.2/RHDV2/b and GI.1b/RHDV lagoviruses in a challenge trial.

European rabbits (Oryctolagus cuniculus) are severely affected by rabbit haemorrhagic disease (RHD). Caused by a lagovirus, the disease leads to losses in the rabbit industry and has implications for wildlife conservation. Past RHD outbreaks have been caused by GI.1/RHDV genotype viruses. A new virus belonging to the GI.2/RHDV2/b genotype emerged in 2010, quickly spreading and replacing the former in several countries; however, limited data are available on its pathogenicity and epidemiological factors. The present work extends these issues and evaluates cross-protection between both genotypes. Ninety-four and 88 domestic rabbits were challenged with GI.2/RHDV2/b and GI.1b/RHDV variant isolates, respectively. Cross-protection was determined by a second challenge on survivors with the corresponding strain. Mortality by GI.2/RHDV2/b was highly variable due to unknown individual factors, whereas mortality by GI.1b/RHDV was associated with age. Mortality in rabbits < 4 weeks old was 84%, higher than previously reported. Cross-protection was not identical between the two viruses because the ratio of mortality rate ratios for the first and second challenges was 3.80 ±â€¯2.68 times higher for GI.2/RHDV2/b than it was for GI.1b/RHDV. Rabbit susceptibility to GI.2/RHDV2/b varied greatly and appeared to be modulated by the innate functionality of the immune response and/or its prompt activation by other pathogens. GI.1b/RHDV pathogenicity appeared to be associated with undetermined age-related factors. These results suggest that GI.2/RHDV2/b may interact with other pathogens at the population level but does not satisfactorily explain the GI.1b/RHDV virus's quick replacement.

Proposal for a unified classification system and nomenclature of lagoviruses.

Lagoviruses belong to the Caliciviridae family. They were first recognized as highly pathogenic viruses of the European rabbit (Oryctolagus cuniculus) and European brown hare (Lepus europaeus) that emerged in the 1970-1980s, namely, rabbit haemorrhagic disease virus (RHDV) and European brown hare syndrome virus (EBHSV), according to the host species from which they had been first detected. However, the diversity of lagoviruses has recently expanded to include new related viruses with varying pathogenicity, geographic distribution and host ranges. Together with the frequent recombination observed amongst circulating viruses, there is a clear need to establish precise guidelines for classifying and naming lagovirus strains. Therefore, here we propose a new nomenclature based on phylogenetic relationships. In this new nomenclature, a single species of lagovirus would be recognized and called Lagovirus europaeus. The species would be divided into two genogroups that correspond to RHDV- and EBHSV-related viruses, respectively. Genogroups could be subdivided into genotypes, which could themselves be subdivided into phylogenetically well-supported variants. Based on available sequences, pairwise distance cutoffs have been defined, but with the accumulation of new sequences these cutoffs may need to be revised. We propose that an international working group could coordinate the nomenclature of lagoviruses and any proposals for revision.

Fipronil/(S)-methoprene spot-on to control fleas on cats in a field trial in Spain

The study was conducted in order to evaluate the effect of a fipronil/(S)-methoprene formulation against fleas on naturally infested cats. The study involved a population of 89 cats distributed among 24 veterinary practices in 9 regions of Spain. The product was applied according to label instructions on days 0, 30 and 60. Animals underwent parasitological and clinical assessments on day 0 and thereafter in monthly intervals (every 30 days) until day 90. Ctenocephalides felis was the most abundant species (98.9% of all fleas collected), and flea abundance on Day 0 was associated with the hair type, the location of the household, and the time elapsed from the last anti-flea treatment. Fipronil/(S)-methoprene demonstrated high efficacy and induced the reduction of clinical signs related to the presence of fleas. Clinical signs and flea abundance decreased significantly throughout time (P=0.001) with an efficacy rate of 72.6% at Day 30, 88.4% at Day 60 and 93.9% at Day 90. A high level of flea control and a remission of the clinical signs related to presence of fleas were observed on cats following 3 monthly applications a fipronil/(S)-methoprene formulation.(AU)

Prevalence of Rickettsia and Bartonella species in Spanish cats and their fleas.

The aim of this study was to determine the prevalence of Bartonella henselae, Rickettsia felis, and Rickettsia typhi in fleas and companion cats (serum and claws) and to assess their presence as a function of host, host habitat, and level of parasitism. Eighty-nine serum and claw samples and 90 flea pools were collected. Cat sera were assayed by IFA for Bartonella henselae and Rickettssia species IgG antibodies. Conventional PCRs were performed on DNA extracted from nails and fleas collected from cats. A large portion (55.8%) of the feline population sampled was exposed to at least one of the three tested vector-borne pathogens. Seroreactivity to B. henselae was found in 50% of the feline studied population, and to R. felis in 16.3%. R. typhi antibodies were not found in any cat. No Bartonella sp. DNA was amplified from the claws. Flea samples from 41 cats (46%) showed molecular evidence for at least one pathogen; our study demonstrated a prevalence rate of 43.3 % of Rickettsia sp and 4.4% of Bartonella sp. in the studied flea population. None of the risk factors studied (cat's features, host habitat, and level of parasitation) was associated with either the serology or the PCR results for Bartonella sp. and Rickettsia sp.. Flea-associated infectious agents are common in cats and fleas and support the recommendation that stringent flea control should be maintained on cats.

Improving the detection of anthelmintic resistance: evaluation of faecal egg count reduction test procedures suitable for farm routines.

The faecal egg count reduction test (FECRT) is the main method of detection of anthelmintic resistance (AR) in nematodes of veterinary importance. However, although the FECRT is standardised, the diagnostic performance of this method has not been fully characterised. In this survey Monte Carlo routines were used to simulate the estimation of faecal egg count reduction (FECR) with several FECRT protocols that were performed under different field and laboratory conditions. The goal was to determine, from a practical viewpoint, the most suitable protocols for farm routines and to evaluate the diagnostic performance of FECRTs across different parasitological scenarios with several levels of AR. The simulated field procedures included variations in the sample size and the sampling (or not) of a control group, whereas the simulated laboratory procedures comprised group mean individual-based vs. composite-based FECR estimations and variations in the egg detection threshold of the McMaster technique. For composite procedures, the random weight variations among individual samples and an increased number of McMaster chamber counts were also simulated. The results showed that FECRTs were moderately affected by inaccuracy but crucially affected by imprecision, and both parameters were clearly dependent on the parasitological conditions and the laboratory and field procedures used. An individual-based FECRT method performed without a control group was the most appropriate to quantify the AR, whereas a composite-based method with a control group was the easiest method for discriminating susceptible and resistant parasite populations. More interestingly, the diagnostic performance of the simulated FECRT methods was low for the procedures that are currently recommended by the World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) and for many of the typical field and laboratory procedures that are currently implemented. Therefore, the results suggest that the diagnostic performance of the FECRT should be re-evaluated, and the recommendations of the W.A.A.V.P. should be redefined. Finally, theoretic critical conditions for FECRT procedures have been defined to improve future AR surveys and to allow the interpretation of FECRT results with the necessary caution according to the diagnostic performance expected for every FECRT procedure and parasitological scenario.

Modelling the effects of past and future climate on the risk of bluetongue emergence in Europe.

Vector-borne diseases are among those most sensitive to climate because the ecology of vectors and the development rate of pathogens within them are highly dependent on environmental conditions. Bluetongue (BT), a recently emerged arboviral disease of ruminants in Europe, is often cited as an illustration of climate's impact on disease emergence, although no study has yet tested this association. Here, we develop a framework to quantitatively evaluate the effects of climate on BT's emergence in Europe by integrating high-resolution climate observations and model simulations within a mechanistic model of BT transmission risk. We demonstrate that a climate-driven model explains, in both space and time, many aspects of BT's recent emergence and spread, including the 2006 BT outbreak in northwest Europe which occurred in the year of highest projected risk since at least 1960. Furthermore, the model provides mechanistic insight into BT's emergence, suggesting that the drivers of emergence across Europe differ between the South and the North. Driven by simulated future climate from an ensemble of 11 regional climate models, the model projects increase in the future risk of BT emergence across most of Europe with uncertainty in rate but not in trend. The framework described here is adaptable and applicable to other diseases, where the link between climate and disease transmission risk can be quantified, permitting the evaluation of scale and uncertainty in climate change's impact on the future of such diseases.

Epidemiology of Oestrus ovis infection of sheep in northeast Spain (mid-Ebro Valley).

Slaughterhouse surveys to determine the prevalence and intensity of larval Oestrus ovis Linnaeus (Diptera: Oestridae) in sheep, were conducted monthly for 1 year in northeastern Spain. The prevalence of O. ovis in 120 sheep in northeast Spain was 84.2%. The monthly prevalence ranged from 62.5% in January to 100% in June and October. Of the 3,831 larvae collected, 3,005 were first instar larvae (78.4%), 744 second instar larvae (19.4%), and 82 third instar larvae (2.1%). The mean larval burden per infected sheep was 37.9, throughout the year although infection was higher in October. The high number of first stage larvae in winter (especially October, November, and December) may be due to a period of slower larval maturation. Third-stage larvae were always present but sometimes in very low numbers compared to the total. According to the results, oestrosis appears to be a serious problem in the region.

Modeling the effect of population dynamics on the impact of rabbit hemorrhagic disease.

The European wild rabbit (Oryctolagus cuniculus) is a staple prey species in Mediterranean ecosystems. The arrival and subsequent spread of rabbit hemorrhagic disease throughout southwestern Europe, however has caused a decline in rabbit numbers, leading to considerable efforts to enhance wild rabbit populations, especially through habitat management. Because rabbit population dynamics depend on habitat suitability and changes in habitat structure and composition subsequent to habitat management, I evaluated the effects of population dynamics on the long-term impact of rabbit hemorrhagic disease on rabbit populations. I used an age-structured model with varying degrees of population productivity and turnover and different habitat carrying capacities, and I assumed the existence of a unique, highly pathogenic virus. My results suggest that disease impact may be highly dependent on habitat carrying capacity and rabbit population dynamics, and the model provided some insight into the current abundance of wild rabbits in different locations in southwestern Europe. The highest disease impact was estimated for populations located in habitats with low to medium carrying capacity In contrast, disease impact was lower in high-density populations in habitats with high carrying capacity, corresponding to a lower mean age of rabbit infection and a resulting lower mortality from rabbit hemorrhagic disease. The outcomes of the model suggest that management strategies to help rabbit populations recover should be based on improving habitats to their maximum carrying capacity and increasing rabbit population productivity. In contrast, the use of strategies based on temporary increases in rabbit density, including vaccination campaigns, translocations, and temporal habitat improvements at medium carrying capacities, may increase disease impact, resulting in short-term decreases in rabbit population density.

Tratamiento de la tuberculosis en un área urbana / Treatment of tuberculosis in an urban area

Antes de iniciar el trabajo, la atención de la tuberculosis era tipo tradicional, con centralización de pacientes en hospitales especializados, excesiva hospitalización y alta proporción de pérdidas de enfermos bajo tratamiento. En 1977 se comenzaron las actividades de control, orientadas a la descentralización hacia los hospitales generales, al incremento del tratamiento ambulatorio y a la supervisión de la toma de fármacos. La estrategia utiliza consistió en integrar grupos de trabajo a la estructura formal de cada hospital, utilizando los recursos ya existentes. Los logros más importantes fueron la descentralización y el aumento de la frecuencia del tratamiento totalmente ambulatorio, casi al doble de la inicial. La supersición alcanzó a la mitad de los enfermos bacilíferos y las pérdidas se redujeron en todos los servicios. Los resultados comprenden 2 etapas: para la primera y segunda, respectivamente, las pérdidas fueron de 14,8% y 6,7%; los fracasos farmacológicos, de 3,8% y 1,2%, y las recaídas posteriores al año de 8,1% y 0,6%. La estrategia empleada, dirigida exclusivamente a organizar la oferta en los servicios donde ésta no existia, inició un cambio global, estimándose que puede resultar útil en casos similares

Tratamiento de la tuberculosis en un área urbana / Treatment of tuberculosis in an urban area

Antes de iniciar el trabajo, la atención de la tuberculosis era tipo tradicional, con centralización de pacientes en hospitales especializados, excesiva hospitalización y alta proporción de pérdidas de enfermos bajo tratamiento. En 1977 se comenzaron las actividades de control, orientadas a la descentralización hacia los hospitales generales, al incremento del tratamiento ambulatorio y a la supervisión de la toma de fármacos. La estrategia utiliza consistió en integrar grupos de trabajo a la estructura formal de cada hospital, utilizando los recursos ya existentes. Los logros más importantes fueron la descentralización y el aumento de la frecuencia del tratamiento totalmente ambulatorio, casi al doble de la inicial. La supersición alcanzó a la mitad de los enfermos bacilíferos y las pérdidas se redujeron en todos los servicios. Los resultados comprenden 2 etapas: para la primera y segunda, respectivamente, las pérdidas fueron de 14,8% y 6,7%; los fracasos farmacológicos, de 3,8% y 1,2%, y las recaídas posteriores al año de 8,1% y 0,6%. La estrategia empleada, dirigida exclusivamente a organizar la oferta en los servicios donde ésta no existia, inició un cambio global, estimándose que puede resultar útil en casos similares (AU)

Factores de riesgo en la muerte por tuberculosis / The risk factors in death by tuberculosis

Se realizó un estudio entre los egresos por tuberculosis del Hospital "E. Tornú" de la ciudad de Buenos Aires. Su propósito fue la identificación de factores asociados al riesgo de morir, con la finalidad de caracterizar el grupo de alto riesgo, fijar criterios para la hospitalización y organizar servicios de atención diferenciada. De los 1.048 pacientes egresados en 1984, 92 correspondieron a defunciones y 956 a altas. El estudio comprendió a 90 egresos del primer grupo y una muestra aleatoria de 199 egresos del segundo grupo. Los factores de riesgo seleccionados fueron: edad de 60 años y más, sexo masculino, complicaciones, asociaciones morbosas, antecedentes de tratamiento previo, formas avanzadas y localizaciones extrapulmonares. Todos los factores estudiados mostraron algún grado de interdependencia con el factor edad avanzada y éste agregó, a cada uno de ellos, riesgos adicionales. Como grupo de alto riesgo se identificó a los enfermos de 60 años y más en todos los casos, sin necesidad de tener en cuenta la concurrencia de otros factores. En los menores de 60 años, las asociaciones morbosas y las complicaciones fueron los más fuertemente asociados con el daño. En el grupo de alto riesgo también deben ser incluidos los pacientes con dos o más factores presentes simultáneamente. Las características de los egresos estudiados son similares a las del conjunto de los enfermos tuberculosos; por lo tanto se presume que los resultados pueden hacerse extensivos, en su mayor parte, a esta población

Factores de riesgo en la muerte por tuberculosis / The risk factors in death by tuberculosis

Se realizó un estudio entre los egresos por tuberculosis del Hospital "E. Tornú" de la ciudad de Buenos Aires. Su propósito fue la identificación de factores asociados al riesgo de morir, con la finalidad de caracterizar el grupo de alto riesgo, fijar criterios para la hospitalización y organizar servicios de atención diferenciada. De los 1.048 pacientes egresados en 1984, 92 correspondieron a defunciones y 956 a altas. El estudio comprendió a 90 egresos del primer grupo y una muestra aleatoria de 199 egresos del segundo grupo. Los factores de riesgo seleccionados fueron: edad de 60 años y más, sexo masculino, complicaciones, asociaciones morbosas, antecedentes de tratamiento previo, formas avanzadas y localizaciones extrapulmonares. Todos los factores estudiados mostraron algún grado de interdependencia con el factor edad avanzada y éste agregó, a cada uno de ellos, riesgos adicionales. Como grupo de alto riesgo se identificó a los enfermos de 60 años y más en todos los casos, sin necesidad de tener en cuenta la concurrencia de otros factores. En los menores de 60 años, las asociaciones morbosas y las complicaciones fueron los más fuertemente asociados con el daño. En el grupo de alto riesgo también deben ser incluidos los pacientes con dos o más factores presentes simultáneamente. Las características de los egresos estudiados son similares a las del conjunto de los enfermos tuberculosos; por lo tanto se presume que los resultados pueden hacerse extensivos, en su mayor parte, a esta población (AU)

Evaluación del efecto protector de la vacunación con BCG / Evaluation of the protective effect of BCG vaccination

Mediante un estudio retrospectivo, en 1981 y 1982 se investigó el efecto protector de la vacuna BCG en menores de 15 años residentes en la ciudad de Buenos Aires y el conglomerado urbano, donde las tasas de morbilidad y mortalidad por tuberculosis son de magnitud intermedia y se cuentan entre las más bajas de América Latina. Se incluyeron 253 casos y 506 casos testigo sanos agrupados por edad, sexo y lugar de residencia, seleccionados según definiciones estipuladas con un criterio riguroso. Em ambos grupos se consideraron vacunados solamente a los que presentaron la cicatriz correspondiente a BCG. El efecto protector se estimó mediante un cociente de probabilidad que relaciona el factor vacunación en el grupo de casos con el factor vacunación en el grupo testigo. Los resultados demostraron un efecto protector de 81,0% para todas las formas y localizaciones de la tuberculosis. Asimismo, en 82 casos graves de tuberculosis y 164 testigos sanos integrantes del grupo, que se estudiaron en forma separada, el efecto protector fue de 99,6%. Debido a que una parte de los vacunados probablemente ya estaban infectados cuando recibieron la vacuna, y a que algunos de los que se clasificaron como no vacunados tenían antecedentes de inoculación sin presentar cicatriz, estos resultados corresponden a la protección mínima que confiere la vacuna BCG. Por último, se señala la conveniencia de continuar con la política de vacunación con BCG y de extender la cobertura con el fin de disminuir la morbilidad y mortalidad por tuberculosis (AU) &P