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Biomedical subjects

V Vorndam

Publications and source records attributed to V Vorndam.

15 recordsLinked to original sources
PubMed1999

Urbanisation of yellow fever in Santa Cruz, Bolivia.

BACKGROUND: Reinvasion by Aedes aegypti of cities in the Americas poses a threat of urbanisation of yellow fever. After detection of yellow-fever infection in a resident of the city of Santa Cruz, Bolivia, in December, 1997, we investigated all subsequent suspected cases. METHODS: We introduced active surveillance of yellow fever in the Santa Cruz area. Hospitals and selected urban and rural health centres reported all suspected cases. Patients were serologically screened for yellow fever, dengue, hepatitis A and B, and leptospirosis. We collected clinical and epidemiological information from patients' records and through interviews. We also carried out a population-based serosurvey in the neighbourhood of one case. FINDINGS: Between December, 1997, and June, 1998, symptomatic yellow-fever infection was confirmed in six residents of Santa Cruz, five of whom died. Five lived in the southern sector of the city. Two had not left the city during the incubation period, and one had visited only an area in which sylvatic transmission was deemed impossible. Of the 281 people covered in the serosurvey 16 (6%) were positive for IgM antibody to yellow fever. Among five people for whom this result could not be explained by recent vaccination, there were two pairs of neighbours. INTERPRETATION: Urban transmission of yellow fever in Santa Cruz was limited in space and time. Low yellow-fever immunisation coverage and high infestation with A. aegypti in the city, and the existence of endemic areas in the region present a risk for future urban outbreaks. We recommend immediate large-scale immunisation of the urban population, as well as tightened surveillance and appropriate vector control.

Adult↗
PubMed1999

Diagnostic value of dengue virus-specific IgA and IgM serum antibody detection.

The diagnostic value of dengue virus (DV)-specific immunoglobulin A (IgA) serum antibody detection, by an indirect immunofluorescence assay (IFA) was evaluated. For this study, the kinetics of DV-specific IgA serum antibodies was analysed in two experimentally immunised macaques, paired samples from 35 patients suspected of a primary or secondary DV infection, paired sera from patients with high levels of IgA specific antibodies against influenza virus (n = 15), sera from patients with other viral infections (n = 40) and healthy blood donors (n = 10), which served as controls. The presence of DV-specific IgA serum antibodies in humans and in monkeys was compared with that of DV-specific IgM demonstrated in a capture enzyme-linked immunosorbent assay (ELISA). The development of DV-specific IgA and IgM antibodies in macaques proved to be similar to that observed in humans with a DV infection. In sera obtained from suspected primary DV patients during the acute phase and convalescent phase, DV-specific IgA was detected in 1/6 (17%) and 6/6 (100%), whereas IgM was detected in 4/6 (67%) and 5/6 (83%), respectively. In sera from suspected secondary DV patients during the acute phase and convalescent phase, DV-specific IgA was detected in 18/29 (62%) and 28/29 (97%), whereas IgM was detected in 20/29 (69%) and 28/29 (97%), respectively. The control group consisted of five paired serum samples from yellow fever vaccinated individuals and a patient with acute tick-borne encephalitis, 15 paired serum samples from patients with high levels of IgA antibodies specific for influenza virus and 40 serum samples from patients with specific IgM antibodies against other viruses. Ten serum samples from healthy blood donors were included. Among the control serum samples, in one patient, both DV-specific IgA and IgM antibodies were present, and in three sera DV-specific IgM antibodies could be demonstrated. These data suggest that detection of DV-specific IgA serum antibodies by IFA may have additional value for the diagnosis of DV infection.

Animals↗
PubMed1999

Evaluation of an IgG enzyme-linked immunosorbent assay for dengue diagnosis.

BACKGROUND: The hemagglutination inhibition (HI) test has been one of the standards, with the IgM antibody capture ELISA (MAC-ELISA), for the diagnosis of dengue virus infections. The spread of dengue throughout the world and the increasing number of cases to be tested makes an ELISA-format test for IgG antibodies to replace the HI test highly desirable. OBJECTIVES: Evaluate the use of the IgG-ELISA as a substitute for the HI test in dengue diagnosis. STUDY DESIGN: Paired serum samples defined as being from primary or secondary dengue virus infections by HI, were tested by an ELISA that detects IgG antibodies. The correlations of titers and serologic interpretations between these two tests were examined. RESULTS: The IgG-ELISA showed a low correlation with the HI in primary infections, and a higher correlation in secondary infections because of the influence of IgM antibodies in the HI test. Nevertheless, IgG ELISA titers could be reliably associated with primary or secondary infections when analyzed by days after onset of symptoms, and can be used to characterize the immune response after flavivirus infections. CONCLUSION: The combination of the IgM and IgG ELISAs may be used to serologically diagnose dengue virus infections, since the IgG ELISA can substitute for the HI test in characterizing the immune response to dengue virus infections.

Antibodies, Viral↗
PubMed1999

Age-specific decrease in seroprevalence of schistosomiasis in Puerto Rico.

In our previous work, we reported the first systematic, island-wide, serologic survey for schistosomiasis in Puerto Rico in 40 years. In that study, approximately 3,000 serum samples from the 76 municipalities comprising the island of Puerto Rico were tested for the detection of antibodies to S. mansoni microsomal antigens by the Falcon assay screening test-enzyme-linked immunosorbent assay (FAST-ELISA) and those positive were confirmed by an enzyme-linked immunoelectrotransfer blot (EITB). The highest EITB positivity was found in 17 municipalities, which comprised 48% of all seropositive samples. An additional finding was that 10% of the 215 EITB-positive samples were from individuals 25 years or younger and were for the most part of residents from the high seroprevalence areas. Thus, for this study we focused on 766 individuals 25 years of age or younger (45.5% males and 54.4% females), two-thirds of which were from 10 municipalities with the highest EITB seropositivity, and one-third from the 10 municipalities with the lowest EITB seropositivity found in our previous study. Of all samples, the results showed an overall FAST-ELISA positivity of 11.6%, with males similar to females (12.6 versus 10.7%, respectively). Confirmation by EITB was only 1.8%, with a males three-fold higher than females (3% versus 0.7%). When seropositivity was measured by age in five-year increments, a clear age-specific decrease in seropositivity was observed. Thus, by FAST-ELISA, 16.7% of the 21-25-year-old age group was positive, decreasing to 14.6%, 9.9%, 7.9%, and 9.3% in the 16-20-, 11-15-, 6-10-, and 1-5-year-old age groups, respectively. Confirmatory EITB showed even more impressive results: 4.7%, 2.6%, 1.2%, 0.7%, and 0% in the same age brackets. With regard to the high prevalence municipalities, only four of 10 (11 of 228 = 4.8%) had confirmatory EITB-positive samples and most were from municipalities of the Rio Grande de Loiza River basin and tributaries. The male to female positivity ratio was 4:1. Of the low prevalence municipalities, only single positive cases (by EITB) were found in three disperse municipalities. These results support the concept that there has been little transmission of S. mansoni in Puerto Rico during the first half of the 1990s and confirms anecdotal comments of local physicians who have seen virtually no new infections during the past three years. This makes the documentation of eradication of schistosomiasis from Puerto Rico feasible, a goal that should be set as being before the 100th anniversary of its discovery on the island by Isaac Gonzalez-Martinez in 1904.

Adolescent↗
PubMed1998

Short communication: dengue serotype 2 subtype III ('Jamaica') epidemic in Santa Cruz, Bolivia.

BACKGROUND: During the past decade, dengue and dengue haemorrhagic fever (DHF) have become a public health problem in various Latin American countries. Indications of increased dengue cases in the city of Santa Cruz, Bolivia, early in 1997 were promptly investigated. METHODS: We conducted a sample sero-survey in one district of the city. Levels of antidengue IgM were determined and genetic analysis was performed on virus isolates. RESULTS: IgM antibodies were detected in 6.5% (95% CI: 3.4%-9.6%) of adults (over 15 years old) and 5.1% (2.0%-8.2%) of children (5-7 years old). Dengue virus serotype 2 subtype III ('Jamaica') was isolated. CONCLUSIONS: The estimated attack rates are compatible with a dengue epidemic in Santa Cruz. Isolation of dengue-2 'Jamaica' virus documents the further spread of this subtype from the Caribbean via Brazil into South America. Increased DHF preparedness seems mandatory.

Adult↗
PubMed1998

Epidemic of dengue-4 virus in Yap State, Federated States of Micronesia, and implication of Aedes hensilli as an epidemic vector.

A dengue fever/dengue hemorrhagic fever (DF/DHF) outbreak in Yap State caused by dengue-4 virus was confirmed serologically and by virus isolation from serum samples collected on each of three island groups. Most DF/DHF cases occurred during a three-month period between mid-May and early August 1995. Five fatal cases, three of which were in children between the ages of four and 11, occurred between June 20 and July 26. A serosurvey conducted in late August revealed anti-dengue IgM prevalence rates of 18% on Yap, 36% on Eauripik, and 6% on Woleai. The majority of residents (93-100%) on the three islands were positive for anti-dengue IgG antibodies, indicating widespread exposure to dengue viruses. The IgG titers indicative of secondary antibody response were noted on Eauripik (6.5%) and Woleai (17%), but were rare on Yap (0.7%). Entomologic investigations implicated the native mosquito species, Aedes hensilli, a member of the Scutellaris Group of Aedes (Stegomyia), as a previously unrecognized epidemic vector of dengue viruses. Aedes hensilli was the most abundant and widespread member of Ae. (Stegomyia) in Yap State, the only species of Ae. (Stegomyia) on Woleai, and the only mosquito species present on Eauripik. New distribution records for mosquito species are reported.

Adolescent↗
PubMed1996

Multicentre evaluation of dengue IgM dot enzyme immunoassay.

BACKGROUND: The traditional methods used in the diagnosis of dengue infection do not lend themselves to field application. As such, clinical specimens have to be sent to a central laboratory for processing which invariably leads to delay. This affects patient management and disease control. The development of the dengue IgM dot enzyme immunoassay has opened up the possibility of carrying out the test in peripheral health settings. OBJECTIVES: This multicentre study was conducted to evaluate a new, commercial nitrocellulose membrane based IgM capture enzyme immunoassay. STUDY DESIGN: The sensitivity and specificity of the test were compared with in-house dengue IgM enzyme-linked immunoassays routinely performed by each of the selected centres. Known positive and negative dengue specimens, as well as specimens from non-dengue cases, were included in the evaluation. RESULTS: Based on 402 specimens tested by the six centres, the sensitivity was 92.1% and specificity 88.1%, with an overall agreement of 92.8% when compared with IgM EIA assays performed on microplates. CONCLUSIONS: The results suggest that this commercial kit has a role to play in the diagnosis of dengue infection, especially in peripheral health settings.

Antibodies, Viral↗
PubMed1995

Symptoms of dengue fever in relation to host immunologic response and virus serotype, Puerto Rico, 1990-1991.

The authors investigated the role of secondary immunologic response, virus serotype, age, and sex on the clinical manifestations of dengue fever in Puerto Rico. From surveillance data for 1990 and 1991, this study identified 3,926 laboratory-positive cases, including 889 for whom dengue immunologic status and symptoms could be ascertained. Of those, 622 cases were virologically confirmed, and 267 cases were serologically confirmed. More than 50% of all positive patients reported fever, chills, headache, eye pain, body pains, joint pains, nausea, vomiting, or skin rash. The frequency of reporting signs, symptoms, and hospitalization was significantly higher among persons with secondary infections diagnosed by serological methods. Only rash was more common among those with primary infections. Symptom reporting increased with age; body pains, joint pains, and rash were significantly more frequently reported by female patients. No significant difference in symptom frequency was found among the virologically confirmed cases, comparing primary and secondary cases or infections due to different serotypes. The data for serologically confirmed cases suggest that in Puerto Rico the manifestations of dengue fever are, as with dengue hemorrhagic fever in Asia, more prominent among those who are experiencing secondary infections, and this effect may be more marked in the younger age groups.

Adolescent↗
PubMed1994

Restriction enzyme analysis of American region dengue viruses.

Restriction fragment heterogeneity of Hae III digestion products of cDNA to virion RNA was used to map the distribution of dengue virus topotypes found in the American region. By comparing the electrophoretic patterns of fragments produced, dengue virus isolates were placed in groups that agreed with those previously determined by oligonucleotide fingerprinting. Dengue-1 and dengue-4 viruses occur throughout the western hemisphere as single genetic types, with most of the isolates sharing at least 70% of their Hae III restriction enzyme fragments. Dengue-2 virus exists as two topotypes in the region with apparently non-overlapping distributions. The Puerto Rico topotype, which has been in the Caribbean for at least 40 years, is genetically diverse, while the Jamaica topotype, first isolated in 1981, is more homogeneous and has expanded its range from the original Caribbean focus to South America.

Aedes↗
PubMed1994

A PCR-restriction enzyme technique for determining dengue virus subgroups within serotypes.

The polymerase chain reaction (PCR) and restriction enzyme analysis were used to develop a rapid and simple procedure for identifying geographic subgroups of dengue virus within serotypes for epidemiologic investigations. The entire structural protein region of dengue viruses was amplified and the products were digested with the endonucleases AluI or DdeI. By comparing the restriction fragment length polymorphisms (RFLPs), we recognized dengue-2 and dengue-3 subgroups that corresponded to those previously determined by oligonucleotide fingerprinting or genomic sequencing. This procedure can be performed in 2 days without the use of radioisotopes, and results can be interpreted without computer analysis. For those analyses which require only subgroup affiliations, this is a useful tool for rapidly screening multiple virus isolates.

Aedes↗
PubMed1993

Molecular and biological characterization of a non-glycosylated isolate of St Louis encephalitis virus.

The glycosylation patterns of the envelope (E) glycoprotein of several naturally occurring strains of St Louis encephalitis (SLE) virus were investigated. SLE viruses were found that contained both glycosylated and non-glycosylated E proteins, and one isolate (Tr 9464) that lacks N-linked glycosylation sites on its E protein was identified. SLE virus monoclonal antibodies that define E protein B cell epitopes and demonstrate biological activities reacted essentially to the same extent with glycosylated and non-glycosylated virions. These results indicate that glycosylation is not essential for epitope conformation or recognition. However, failure to glycosylate the E protein was associated with possible morphogenetic differences as manifested by reduced virus yields and differences in specific infectivity.

Amino Acid Sequence↗
PubMed1991

Sensitivity and specificity of a universal primer set for the rapid diagnosis of dengue virus infections by polymerase chain reaction and nucleic acid hybridization.

A set of sense and anti-sense oligomeric DNA primers, degenerate in the third "wobble" base position of codons so as to match all known dengue virus sequences, was evaluated as universal primers in a polymerase chain reaction (PCR) assay for the rapid diagnosis of dengue virus infections. Virus-specific complementary DNA (cDNA) was prepared by reverse transcription (RT) of total RNA extracted from serum. Amplified cDNA was identified by nucleic acid hybridization with four serotype-specific, oligomeric DNA probes. Using sera from patients admitted with dengue fever, RT/PCR followed by nucleic acid hybridization using radiolabeled probes was 68% sensitive (50/74; 95% confidence interval [CI] = 57-78%) and 100% specific. Chemiluminescent detection of hybridized products was 62% sensitive (26/42; 95% CI = 46-75%). Using specimens from which a virus isolate had been obtained, RT/PCR followed by nucleic acid hybridization with radiolabeled probes was 80% sensitive (40/50; 95% CI = 69-91%) and 100% specific. The results suggest that RT/PCR using degenerate primers is a sensitive and specific method for the detection of dengue viruses in clinical specimens.

DNA Probes↗
PubMed1979

A comparison of La Crosse virus isolated obtained from different ecological niches and an analysis of the structural components of California encephalitis serogroup viruses and other bunyaviruses.

Analyses of the oligonucleotide fingerprints of the three genome ribonucleic acid (RNA) species of 11 isolates of La Crosse (LAC) virus, obtained from various ecological niches in the northern United States and compared to those of prototype LAC virus, showed that in each place from which these isolates were obtained LAC variants and varieties were present with related, but distinguishable, nucleotide sequences for their large, medium, or small RNA species. The RNA genomes of prototypes trivittatus (TVT), snowshoe hare (SSH), Tahyna (TAH), and Lumbo (a variety of TAH) viruses of the California encephalitis (CE) serogroup, and Guaroa of the Bunyamwera serogroup also consist of three RNA species, each with unique and distinguishable nucleotide sequences which bear little resemblance to those of the LAC virus isolates. The virions of CE group viruses (CE, Jamestown Canyon, Keystone, LAC, Melao, SSH, TVT, TAH viruses and South River, an unregistered virus) have three major viral polypeptides, designated G1, G2, and N.

Arboviruses↗
PubMedDate not supplied

Dengue reemergence in Argentina.

Aedes aegypti, eradicated from Argentina in 1963, has now reinfested the country as far south as Buenos Aires. In 1997, four persons with travel histories to Brazil, Ecuador, or Venezuela had confirmed dengue, and surveillance for indigenous transmission allowed the detection of 19 dengue cases in Salta Province. These cases of dengue are the first in Argentina since 1916 and represent a new southern extension of dengue virus.

Aedes↗