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PubMed2006

Molecular characterisation of Mycobacterium tuberculosis isolates in the First National Survey of Anti-tuberculosis Drug Resistance from Venezuela.

BACKGROUND: Molecular typing of Mycobacterium tuberculosis strains has become a valuable tool in the epidemiology of tuberculosis (TB) by allowing detection of outbreaks, tracking of epidemics, identification of genotypes and transmission events among patients who would have remained undetected by conventional contact investigation. This is the first genetic biodiversity study of M. tuberculosis in Venezuela. Thus, we investigated the genetic patterns of strains isolated in the first survey of anti-tuberculosis drug-resistance realised as part of the Global Project of Anti-tuberculosis Drug Resistance Surveillance (WHO/IUATLD). RESULTS: Clinical isolates (670/873) were genotyped by spoligotyping. The results were compared with the international spoligotyping database (SpolDB4). Multidrug resistant (MDR) strains (14/18) were also analysed by IS6110-RFLP assays, and resistance to isoniazid and rifampicin was characterised. Spoligotyping grouped 82% (548/670) of the strains into 59 clusters. Twenty new spoligotypes (SITs) specific to Venezuela were identified. Eight new inter-regional clusters were created. The Beijing genotype was not found. The genetic network shows that the Latin American and Mediterranean family constitutes the backbone of the genetic TB population-structure in Venezuela, responsible of >60% of total TB cases studied. MDR was 0.5% in never treated patients and 13.5% in previously treated patients. Mutations in rpoB gene and katG genes were detected in 64% and 43% of the MDR strains, respectively. Two clusters were found to be identical by the four different analysis methods, presumably representing cases of recent transmission of MDR tuberculosis. CONCLUSION: This study gives a first overview of the M. tuberculosis strains circulating in Venezuela during the first survey of anti-tuberculosis drug-resistance. It may aid in the creation of a national database that will be a valuable support for further studies.

Antitubercular Agents↗
PubMedDate not supplied

[Prevalence of human infections by Trypanosoma cruzi in blood banks in Venezuela].

Primary investigations carried out in blood banks in Venezuela during the 1950s, indicated that overall seroprevalence for Trypanosoma cruzi infection was 12% amongst blood donors. In Venezuela, blood donation is free. All public and private blood banks are controlled by the Ministry of Health. As from 1988 the ELISA technique was uniformly used in blood banks for the detection of T. cruzi infections. Annual median seroprevalence, between 1988 to 1992, was 1.20% (1.09-1.94%), with geographical variations between localities in several States. States with higher prevalence rates are located in the western and central part of Venezuela: Portuguesa, Lara, Trujillo, Cojedes and Carabobo. Due to difficulties in obtaining incidence rates for Chagas disease, it seems proper to use prevalence rates due to its greater stability; and in the specific case of Venezuela, due to a lesser severity and a higher survival of this disease at present. Considering that there is little to be offered to the seropositive individual, repeatability is avowed for serological diagnosis. Specificity should be strived for in the light of lower prevalence rates at present.

Adolescent↗
PubMed2002

[Primary care and alcohol use disorders: evaluation of a faculty-development program in Venezuela].

OBJECTIVE: Primary care offers an opportunity to identify and treat persons who drink alcohol above permissible levels. In order to prepare primary care practitioners around the world to prevent and treat alcohol-related problems, the National Institute on Alcohol Abuse and Alcoholism of the United States of America has developed and tested a model international program for educating physicians about such problems. The model was designed to increase the clinical, teaching, and research skills of medical school faculty who work with medical students, residents, and primary care physicians. Venezuela was one of the countries selected for the initiative. METHODS: During September 1999 a five-day faculty-development course consisting of 19 workshops was conducted at the University of Zulia, which is located in the city of Maracaibo, Zulia, Venezuela. Teaching strategies included class presentations, role plays, case presentations, skills-building workshops, and having each participant develop a teaching plan that he or she would use. RESULTS: Thirty-three faculty members from 9 of Venezuela's 10 medical schools participated in the project. The 18 female and 15 male participants had an average age of 44 years. The areas of specialization of the 33 participants were: family medicine (9 participants), psychiatry (7), pediatrics (6), obstetrics (4), internal medicine (3), and unspecified (4). Of the 33 participants, 25 of them (76%) completed a six-month follow-up interview. This group said they had significantly increased their competence in 14 clinical areas and that they had successfully implemented new teaching activities within their respective medical schools and residency programs. CONCLUSIONS: This model proved to be an effective strategy for increasing training for physicians in the prevention and treatment of alcohol-related problems in Venezuela. The evaluation confirms similar findings in other countries where the program has been implemented.

Adult↗
PubMed2006

Poverty rates in Venezuela: getting the numbers right.

This article looks at household and individual poverty rates in Venezuela over the past seven years. For more than a year, the statement that poverty in Venezuela has increased under the government of President Hugo Chávez has appeared in scores of major newspapers, on major television and radio programs, and even in publications devoted to foreign policy. There are no data to support such statements, and in fact the available data show a decline in poverty for both individuals and households over the seven-year period: the percentage of people in poverty declined from 50 percent in the first quarter of 1999 to 43.7 percent in 2005. Further, there is no evidence to suggest any change in the methodology for measuring poverty during this period, as has been alleged in a number of reports. The article also examines briefly the impact of significant changes in non-cash benefits such as free health care, which are not taken into account in the measured poverty rate, on poor people in Venezuela. Finally, the authors look at how the mistakes in reporting on Venezuela's poverty rate were made; an appendix gives examples of mistakes in major media and foreign policy publications.

Data Collection↗
PubMed1996

[Mycetoma: report of 3 cases in Falcón State, Venezuela].

This is a report of three cases of mycetome studied in our laboratory during the last four years. We also informed about the evolution of the first case produced by Pyrenochaeta romeroi nova species reported by Borelli in 1959. All the patients were farmer men, 18, 42 and 54 years old, from the semiarid and subhumid zones of Falcon State, located on the northwest region of Venezuela. Clinically, all patients presented the mycetome syndrome (subcutaneous edema, sinus tract and "granules"), with a evolution of six months to three years. The lesions were localized in the inferior limbs in two of the patients and in the thorax in one of them. The clinical diagnose was confirmed by microbiological and mycological studies, isolating Nocardia brasiliensis in two cases and Madurella grisea in one. Two patients treated with Sulfas showed remission of the disease in a two years follow up. Including this report, 15 cases of mycetome have been reported in the Falcon State (Venezuela) in a period of thirty five years, representing only 9, 14% of the national casuistic. Actinomadura madurae and N. brasiliensis have been the most frequently isolated agents in this region. In order to determine the real endemicity of the mycetome in Venezuela, multidisciplinary clinical, inmunological, microbiological and epidemiological studies are recommended. According to the reported casuistic (15 cases), the mycetome should be a low frequency disease in Falcon State, Venezuela. We confirm that early diagnosis favors an efficient therapy.

Adolescent↗
PubMed2003

Beta-glucosylation as a part of self-resistance mechanism in methymycin/pikromycin producing strain Streptomyces venezuelae.

In our study of the biosynthesis of D-desosamine in Streptomyces venezuelae, we have cloned and sequenced the entire desosamine biosynthetic cluster. The deduced product of one of the genes, desR, in this cluster shows high sequence homology to beta-glucosidases, which catalyze the hydrolysis of the glycosidic linkages, a function not required for the biosynthesis of desosamine. Disruption of the desR gene led to the accumulation of glucosylated methymycin/neomethymycin products, all of which are biologically inactive. It is thus conceivable that methymycin/neomethymycin may be produced as inert diglycosides, and the DesR protein is responsible for transforming these antibiotics from their dormant to their active forms. This hypothesis is supported by the fact that the translated desR gene has a leader sequence characteristic of secretory proteins, allowing it to be transported through the cell membrane and hydrolyze the modified antibiotics extracellularly to activate them. Expression of desR and biochemical characterization of the purified protein confirmed the catalytic function of this enzyme as a beta-glycosidase capable of catalyzing the hydrolysis of glucosylated methymycin/neomethymycin produced by S. venezuelae. These results provide strong evidence substantiating glycosylation/deglycosylation as a likely self-resistance mechanism of S. venezuelae. However, further experiments have suggested that such a glycosylation/deglycosylation is only a secondary self-defense mechanism in S. venezuelae, whereas modification of 23S rRNA, which is the target site for methymycin and its derivatives, by PikR1 and PikR2 is a primary self-resistance mechanism. Considering that postsynthetic glycosylation is an effective means to control the biological activity of macrolide antibiotics, the availability of macrolide glycosidases, which can be used for the activation of newly formed antibiotics that have been deliberately deactivated by engineered glycosyltransferases, may be a valuable part of an overall strategy for the development of novel antibiotics using the combinatorial biosynthetic approach.

Amino Acid Sequence↗
PubMed1990

Plasmid transformation of Streptomyces venezuelae: modified procedures used to introduce the gene(s) for p-aminobenzoate synthase.

Sucrose was unsuitable as an osmotic stabilizer in buffer solutions and media used for transformation of Streptomyces venezuelae ISP5230. Its replacement with NaCl, together with other modifications in the procedure, allowed efficient formation and regeneration of protoplasts but did not support transformation of S. venezuelae ISP5230 by vectors pIJ41 and pIJ941. With pIJ702, transformants with a low plasmid-copy-number and altered growth characteristics were obtained. Both pIJ702 and pIJ941, but not pIJ41, transformed S. venezuelae 13s; when pIJ941 was used, the plasmid in 18 of 20 transformants contained a deletion in the region reported to code for replication and transfer. The modified plasmid transformed S. venezuelae ISP5230 efficiently and was used to introduce a fragment of DNA from the pab locus of the wild-type into a Cml-1 mutant of ISP5230 blocked in chloramphenicol formation. Transformants that overproduced p-aminobenzoic acid were obtained but they remained blocked in chloramphenicol production; thus, the cloned pab fragment did not contain genes able to complement the cml-1 mutation. The results also suggest that the Cml-1 phenotype is not due to a defective reaction common to the biosynthesis of p-aminobenzoic acid and chloramphenicol.

4-Aminobenzoic Acid↗
PubMed1993

Location of the genes for anthranilate synthase in Streptomyces venezuelae ISP5230: genetic mapping after integration of the cloned genes.

The anthranilate synthase (trpEG) genes in Streptomyces venezuelae ISP5230 were located by allowing a segregationally unstable plasmid carrying cloned S. venezuelae trpEG DNA and a thiostrepton resistance (tsr) marker to integrate into the chromosome. The integrated tsr was mapped by conjugation and transduction to a location close to tyr-2, between arg-6 and trpA13. A genomic DNA fragment containing trpC from S. venezuelae ISP5230 was cloned by complementation of a trpC mutation in Streptomyces lividans. Evidence from restriction enzyme analysis of the cloned DNA fragments, from Southern hybridization using the cloned trp DNA as probes, and from cotransduction frequencies, placed trpEG at a distance of 12-45 kb from the trpCBA cluster. The overall arrangement of tryptophan biosynthesis genes in the S. venezuelae chromosome differs from that in other bacteria examined so far.

Anthranilate Synthase↗
PubMed1996

Cloning, sequencing and disruption of a bromoperoxidase-catalase gene in Streptomyces venezuelae: evidence that it is not required for chlorination in chloramphenicol biosynthesis.

Genomic DNA libraries of Streptomyces venezuelae ISP5230 and of a mutant blocked at the chlorination step of chloramphenicol biosynthesis were probed by hybridization with a synthetic oligonucleotide corresponding to the N-terminal amino acid sequence of a bromoperoxidase-catalase purified from the wild-type strain. Hybridizing fragments obtained from the two strains were cloned and sequenced. Analysis of the nucleotide sequences demonstrated that the fragments contained the same 1449 bp open reading frame with no differences in nucleotide sequence. The deduced polypeptide encoded 483 amino acids with a calculated M(r) of 54,200; the N-terminal sequence was identical to that of the bromoperoxidase-catalase purified from wild-type S. venezuelae. Comparison of the amino acid sequence predicted for the cloned bromoperoxidase-catalase gene (bca) with database protein sequences showed a significant similarity to a group of prokaryotic and eukaryotic catalases, but none to other peroxidases or haloperoxidases. Replacement of the bca gene in the wild-type strain of S. venezuelae with a copy disrupted by insertion of a DNA fragment encoding apramycin resistance did not prevent chloramphenicol production. The results suggest that the role of the enzyme in S. venezuelae is related to its activity as a catalase rather than as a halogenating agent.

Amino Acid Sequence↗
PubMed1996

A role for pabAB, a p-aminobenzoate synthase gene of Streptomyces venezuelae ISP5230, in chloramphenicol biosynthesis.

Mutagenesis of Streptomyces venezuelae ISP5230 and selection for P-aminobenzoic acid-dependent growth in the presence of sulfanilamide yielded pab mutants (VS519 and VS620) that continued to produce chloramphenicol (Cm), although with increased medium dependence. Transforming the mutants with pDQ102 or pDQ103, which carried a pab-complementing fragment from S. venezuelae ISP5230 in alternative orientations, restored uniformly high Cm production in VS620, but did not alter the medium dependence of Cm production in VS519. The cloned S. venezuelae DNA fragment was subcloned and trimmed to the minimum size conferring pab complementation. The resulting 2.8 kb BamHl-Sacl fragment was sequenced. Codon preference analysis showed one complete ORF encoding a polypeptide of 670 amino acids. Comparison of the deduced amino acid sequence with database proteins indicated that the N- and C-terminal regions resembled PabA and PabB, respectively, of numerous bacteria. The gene product showed overall sequence similarity to the product of a fused pabAB gene associated with secondary metabolism in Streptomyces griseus. Insertion of an apramycin resistance gene into pabAB cloned in a segregationally unstable vector and replacement of the S. venezuelae chromosomal pabAB with the disrupted copy lowered sulfanilamide resistance from 25 to 5 micrograms mL-1 and blocked Cm production.

Amino Acid Sequence↗
PubMed1993

Accumulation of intracellular carbon reserves in relation to chloramphenicol biosynthesis by Streptomyces venezuelae.

Two chloramphenicol-producing strains of Streptomyces venezuelae accumulated small amounts of polyhydroxybutyrate during exponential growth; the compound disappeared from the mycelium as the cultures entered stationary phase. Depletion of polyhydroxybutyrate coincided with chloramphenicol production but the amount of polymer stored in the mycelium was insufficient to supply the precursor requirement for biosynthesis of the antibiotic. Accumulation of polyhydroxybutyrate in the S. venezuelae strains was appreciably lower than in two other streptomycetes examined. Glycogen and lipids accumulated in the mycelium of S. venezuelae 13s during the stationary phase, after nitrogen depletion; under the culture conditions used, they were the principal storage compounds in S. venezuelae. Trehalose was absent from the mycelium in vegetative cultures grown under nonsporulating conditions but it was abundant in spores obtained from submerged and surface cultures. Glycogen and polyhydroxybutyrate were absent from spores.

Chloramphenicol↗
PubMed2004

Molecular and serological evaluation of surface antigen negative hepatitis B virus infection in blood donors from Venezuela.

Surface antigen negative hepatitis B virus (HBV) infection was evaluated in Venezuela, by molecular characterization of blood samples positive for antibodies to core antigen (anti-HBc) and negative for surface antigen (HBsAg) in blood donors (residual infections). HBV DNA was found in 11/258 samples (4.3%), and was significantly associated with high levels of anti-HBc antibodies (>25 UI/ml, P < 0.05), while no correlation was found between the presence of HBV DNA and the levels of anti-HBs. Synonymous and non-synonymous mutations were found in the HBV surface region (but not vaccine escape mutants) and in the precore/core region (precore mutants in 2/7 samples and 33-45 bp deletions near the N-terminal core region in 4/19 samples). While HBV genotype F prevails among HBsAg positive samples from blood donors in Venezuela, residual infection isolates were mainly genotypes A and D. Phylogenetic analysis of viral surface and core region revealed discrepancies in genotype designation in 6/9 samples, suggesting the presence of mixed infection or recombination. In conclusion, HBV residual infection in Venezuela does not seem to be frequently observed in HBV genotype F. This type of infection is frequently associated with variants exhibiting mutations in the surface gene that might be affecting the correct recognition by commercial tests, with precore mutants and with core internal deletions. These variants do not seem to cause severe liver disease, and on the contrary, were found circulating at low viremia.

Amino Acid Sequence↗
PubMed2006

Infected dogs as a risk factor in the transmission of human Trypanosoma cruzi infection in western Venezuela.

A total of 565 mongrel dogs from rural localities of Venezuela were examined by serological (DAT, IFAT and ELISA) and parasitological tests to address the status of Trypanosoma cruzi infection and to evaluate their role in the transmission of the infection to human population. The overall percentage of sero-positive infected dogs shown to be 67.6% (382/565):253 (61.7%) from 47 villages belonging to 8 states located at 4 different geographical regions of western Venezuela and 129 (33.5%) dogs from 48 households located in areas where Chagas disease is endemic. From 101 sampled dogs living in close proximity to 30 acute chagasic patients, 84% expressed specific anti-T. cruzi antibodies (Ab) with 12 of them (14%) showing blood circulating parasites (BCP). In these houses a high proportion of sero-positive people (20%) and frequent indoor infestation by triatomine-bugs (70%) was also recorded. The analysis revealed that from the 47 rural villages sampled during the study, 91.5% had the presence of T. cruzi sero-positive dogs, ranging from 62% positive localities at the states of Falcon and Cojedes to 100% in the other six studied Venezuelan states. This demonstrates that T. cruzi-infected dogs are found throughout all the geographical regions of western Venezuela irrespective of their ecological differences. Molecular typing of T. cruzi isolates from infected dogs using ribosomal and mini-exon gene markers, revealed the presence of both T. cruzi I and T. cruzi II lineages. The coincidence in the circulation of T. cruzi II in dog and human populations at the same locality and at the same time is reported and its significance is discussed. The combined serological, parasitological, epidemiological and molecular data is gathered here to call the attention on the presence of infected dogs as a risk factor in the maintenance of T. cruzi as a source for infection to humans.

Animals↗
PubMed2005

Prevalence and risk factors associated with the metabolic syndrome and dyslipidemia in White, Black, Amerindian and Mixed Hispanics in Zulia State, Venezuela.

Studies have highlighted the association between insulin resistance (IR) and several cardiovascular (CV) risk factors, including hypertension (HTN), obesity, dyslipidemia (i.e. high triglyceride and low HDL-cholesterol) and glucose intolerance, in a cluster known as the metabolic syndrome (MS). There are few data on the frequency of the MS and dyslipidemia in developing countries, and none in South America. To estimate the prevalence of the MS and its components in Zulia State, Venezuela, and to establish associated demographic and clinical factors, we evaluated 3108 Hispanic men and women aged 20 years or older from a cross-sectional survey of a random representative sample from each health district in Zulia State, Venezuela (1999-2001). Prevalence of the MS and dyslipidemia was defined according to the National Cholesterol Education Program (NCEP)/Adult Treatment Panel III (ATP III) criteria. The age-adjusted prevalence of MS and dyslipidemia was 31.2% and 24.1%, respectively, with higher rates in men than in women. Prevalence rates increased with age and with the degree of obesity. MS prevalence was lower in Amerindian (17.%) compared to Black (27.2%), White (33.3%) and Mixed (37.4%) men, but no differences were found among women. Overall, low HDL-cholesterol (65.3%), abdominal obesity (42.9%) and HTN (38.1%) were the most frequent MS components. After adjusting for age, sex and race groups, family history of diabetes, obesity and HTN were associated with the MS. Sedentary lifestyle also increased the risk of MS, event after adjusting for the same covariates, obesity and the degree of IR. These results suggest that MS is found in approximately one-third of the Venezuelan adult population in Zulia State, with higher prevalence in men related to the presence of dyslipidemia. Lifestyle interventions in MS subjects are needed in Venezuela to halt the burden of CV disease and diabetes.

Adult↗
PubMed2005

Diffuse unilateral subacute neuroretinitis in Venezuela.

PURPOSE: To describe the clinical features and management of the largest reported series to date of patients with diffuse unilateral subacute neuroretinitis (DUSN). DESIGN: Observational case series. METHODS: The charts of all patients coded as having DUSN in a vitreoretinal clinic in Caracas, Venezuela between July 1979 and August 2000 were retrospectively reviewed. MAIN OUTCOME MEASURES: Demographic information, presenting visual acuity, clinical course, and treatment were evaluated. RESULTS: We identified 82 eyes of 78 patients with DUSN. The mean age at diagnosis was 16.7 years, significantly younger than the mean age of the Venezuelan population. Sixty-five (83.3%) patients were 20 years old or younger (P<0.001 when compared with the population of Venezuela). Thirty-three (42.3%) of the patients were female. The presenting visual acuity was 20/400 or worse in 69 eyes (84.1%). The subretinal nematode was identified in 33 eyes (40.2%). All nematodes were small, approximately 400 microm in length. CONCLUSIONS: In Venezuela, DUSN is seen primarily in young patients without a significant gender predilection. The vast majority of patients in this population presented with severe vision loss that was irreversible.

Acute Disease↗
PubMed2000

Onchocerca-Simulium complexes in Venezuela: can human onchocerciasis spread outside its present endemic areas?

The compatibility between sympatric and allopatric combinations of Onchocerca volvulus-anthropophilic species of Simulium was studied in the north-eastern focus of human onchocerciasis as well as in a densely populated locality of the Amazonas State in Venezuela. The objectives were to test the conjecture that local adaptation exists between the parasite and its vectors (the Onchocerca-Simulium complex hypothesis), and assess the possibility of the infection spreading from its present distributional range. For the homologous combination, O. volvulus-S. metallicum cytospecies E in Anzoátegui State (north-eastern focus), parasite yield was 45% in contrast to 1% for the heterologous, southern parasite-S. metallicum infection. This was significantly lower than the parasite yield (4-10%) expected after allowing for the effect of density-dependent limitation of infective larval output described in this paper for S. metallicum. The population of S. exiguum s.l. from southern Venezuela allowed no larval development beyond the L1 stage of either northern or southern parasites. Mechanisms for such refractoriness probably operate at the level of the thoracic muscles, not affecting microfilarial uptake or migration out of the bloodmeal. The parasite yield of southern O. volvulus in S. oyapockense s.l. flies biting man at Puerto Ayacucho (Amazonas) was about 1%, in agreement with the figures recorded for highly compatible sympatric combinations such as O. volvulus-S. ochraceum s.l. in Guatemala. No infective larval development of the northern parasite was observed in southern S. oyapockense. These results, together with considerations of typical worm burdens in the human host, presence/absence of armed cibaria in the simuliids, parasite-induced vector mortality, and fly biting rates, suggest a lower potential for onchocerciasis to spread between the northern and southern endemic areas of Venezuela than that between Amazonian hyperendemic locations and settlements outside this focus with high densities of S. oyapockense s.l.

Adult↗
PubMed2001

Analysis of HIV type 1 protease and reverse transcriptase sequences from Venezuela for drug resistance-associated mutations and subtype classification: a UNAIDS study.

We report the first study on prevalence of antiretroviral drug-associated resistance mutations in Venezuela. Protease and reverse transcriptase (RT) coding regions were analyzed in DNA samples obtained from 100 HIV-1-infected individuals. Primary resistance mutations to RT inhibitors were identified in 26% of patients treated with these drugs. Transmission of HIV-1-resistant strains was detected in a drug-naive patient (3%). Primary resistance mutations to protease inhibitors (PIs) were present in 9% of the 44 PI-treated patients and in 1 PI-naive individual. Phylogenetic analysis of these samples has resulted in the most extensive survey, to date, of HIV-1 genetic forms circulating in Venezuela. Ninety-nine samples clustered with subtype B, and 1 individual harbored the first B/F recombinant virus reported in Venezuela, with protease clustering with subtype F and RT with subtype B. In addition, this isolate had a new insertion (Glu-34 duplication) in the protease gene.

Anti-HIV Agents↗
PubMed1976

Studies of arboviruses in Southwestern Venezuela: I. Isolations of Venezuelan and Eastern Equine Encephalitis viruses from sentinel hamsters in the Catatumbo region.

The purpose of this report is to describe isolations of Venezuelan (VEE) and Eastern (EEE) Equine Encephalitis virus made in the lowland moist tropical forest of the Catatumbo region on the southwestern part of the State of Zulia, Venezuela. We have isolated four strains of EEEV from sentinel hamsters exposed at Caño Mocho and Madre Vieja sites in 1973 and 1974, and three strains of EEEV in Hacienda (Hda.) Las Nubes in 1975. Both viruses were recovered during silent interepidemic periods and we believe these viruses are maintained in this region in sylvatic conditions. The recovered virus strains were detected within 24 to 48 hours, both in SMB and Vero Cell monolayer cultures and the sentinel hamsters yielded virus infectivities up to 10(4) PFU ml. Our VEEV isolate (IVIC PAn 23645-47), recovered during the silent interepizodemic period had an elution profile on the hydroxylapatite column corresponding to that of a I-D (VEEV-3880) or a I-E (VEEV-63A216) 'enzootic' subtype. However, considering other in vitro criteria (KHI; HA pH 5.8-6.0; small plaque size in Vero monolayers with suitable overlay media), this later and other previous isolates had some very distinct properties of the 'epizootic' strains. Thus, the evidence suggests that in Venezuela the VEEV cycle in nature is maintained either by the so called 'enzootic' and/or 'epizootic' virus types, or the virus population of the isolates have particular in vitro properties which do not correlate to the virulence markers in vivo. We consider this important question must be further clarified, and in addition, the isolation of three strains of EEEV are reported; this is the first report of the presence of this virus in Venezuela. Although the EEEV isolates may be of the South American type, they must be considered as potentially dangerous in the case of outbreaks.

Animals↗