Expanded safety and immunogenicity of a bivalent, oral, attenuated cholera vaccine, CVD 103-HgR plus CVD 111, in United States military personnel stationed in Panama.
To provide optimum protection against classical and El Tor biotypes of Vibrio cholerae O1, a single-dose, oral cholera vaccine was developed by combining two live, attenuated vaccine strains, CVD 103-HgR (classical, Inaba) and CVD 111 (El Tor, Ogawa). The vaccines were formulated in a double-chamber sachet; one chamber contained lyophilized bacteria, and the other contained buffer. A total of 170 partially-immune American soldiers stationed in Panama received one of the following five formulations: (a) CVD 103-HgR at 10(8) CFU plus CVD 111 at 10(7) CFU, (b) CVD 103-HgR at 10(8) CFU plus CVD 111 at 10(6) CFU, (c) CVD 103-HgR alone at 10(8) CFU, (d) CVD 111 alone at 10(7) CFU, or (e) inactivated Escherichia coli placebo. Among those who received CVD 111 at the high or low dose either alone or in combination with CVD 103-HgR, 8 of 103 had diarrhea, defined as three or more liquid stools. None of the 32 volunteers who received CVD 103-HgR alone or the 35 placebo recipients had diarrhea. CVD 111 was detected in the stools of 46% of the 103 volunteers who received it. About 65% of all persons who received CVD 103-HgR either alone or in combination had a fourfold rise in Inaba vibriocidal titers. The postvaccination geometric mean titers were comparable among groups, ranging from 450 to 550. Ogawa vibriocidal titers were about twice as high in persons who received CVD 111 as in those who received CVD 103-HgR alone (600 versus 300). The addition of CVD 111 improved the overall seroconversion rate and doubled the serum Ogawa vibriocidal titers, suggesting that the combination of an El Tor and a classical cholera strain is desirable. While CVD 111 was previously found to be well tolerated in semiimmune Peruvians, the adverse effects observed in this study indicate that this strain requires further attenuation before it can be safely used in nonimmune populations. (+info)
Use of base excision sequence scanning for detection of genetic variations in St. Louis encephalitis virus isolates.
Twenty-two isolates of St. Louis encephalitis (SLE) virus of various geographical origins (Brazil, Argentina, Panama, Texas, Missouri, Maryland, California, and Florida) were examined for genetic variation by the base excision sequence scanning (BESS T-scan) method. A fragment was amplified in the envelope gene with the forward primer labeled in the PCR. The BESS T-scan method determined different clusters according to the profiles generated for the isolates and successfully grouped the isolates according to their geographical origins. Two major clusters, the North American cluster (cluster A) and the South and Central American cluster (cluster B), were defined. Two subgroups, the Texas-California subgroup (subgroup A1) and the Missouri-Maryland-Florida subgroup (subgroup A2), were distinguished within group A. Similarly, group B strains were subclustered to a South American subgroup (subgroup B1) and a Central American subgroup (subgroup B2). These results were consistent with those obtained by DNA sequencing analysis. The ability of the BESS T-scan method to discriminate between strains that present with high degrees of nucleotide sequence similarity indicated that this method provides reliable results and multiple applications for other virus families. The method has proven to be suitable for phylogenetic comparison and molecular epidemiology studies and may be an alternative to DNA sequencing. (+info)
Susceptibility of Panamanian Aotus lemurinus lemurinus to sporozoite-induced Plasmodium falciparum (Santa Lucia) infection.
Aotus monkeys are good models for erythrocyte-induced Plasmodium falciparum and P. vivax infections and have been extensively used in malarial drug and vaccine development. Recently, it has been shown that certain species of Aotus can be infected with sporozoites, and that the degree of susceptibility varies among species. We demonstrate here that Panamanian Aotus lemurinus lemurinus are susceptible to a sporozoite-induced infection, opening the possibility that this species of Aotus could be used as models for testing the efficacy of pre-erythrocytic P. falciparum vaccines and drug candidates directed at the pre-erythrocytic stages of P. falciparum and P. vivax malaria. In this species, we compared sporozoite infection rates. Two of four animals splenectomized prior to infection with sporozoites developed patent parasitemias. Seven of eight animals splenectomized either 7 or 35 days after infection became parasitemic. Additionally, we used a P. falciparum-specific polymerase chain reaction (PCR) method to detect the early appearance of parasitized erythrocytes in the blood prior to detection by conventional microscopy, and found that the parasitemia was detected first in five animals by the PCR method, first in three animals by blood film, with one parasitemia detected simultaneously. We also demonstrated the feasibility of infecting monkeys located in Panama with sporozoites isolated at an insectary in Atlanta, thus documenting the feasibility of similar studies where the insectary and monkey colony are not in the same location. A subsequent attempt to infect these monkeys using sporozoites was not successful, suggesting that this model of human malaria is not yet ready for routine use in vaccine or drug efficacy screening. This model merits further study because of the importance of testing pre-erythrocytic P. falciparum malaria vaccines and drugs in animals. (+info)
Risk factors for human T cell lymphotropic virus type II infection among the Guaymi Indians of Panama.
To examine risk factors for human T cell lymphotropic virus type II (HTLV-II) infection, a case-control study was conducted among the Guaymi Indians of Panama. In females, HTLV-II seropositivity was associated with early sexual intercourse (15 years; odds ratio [OR], 2.50; 95% confidence interval [CI], 1.11-6.14) and number of lifetime sex partners. One partner increased risk of seropositivity by 30% (OR, 1.30; CI, 1.05-1.64), and risk increased with number of partners. Similar risk was associated with number of long-term sexual relationships. Among males, intercourse with prostitutes was associated with HTLV-II seropositivity (OR, 1.68; CI, 1.04-2.72). These data support a role for sexual transmission in HTLV-II infection. Association of seropositivity with primary residence in a traditional village (OR, 3.75; CI, 1.02-15.38) and lack of formal education (0 vs. >6 years [OR, 3.89; CI, 1.67-9.82]) observed in males may reflect differences in sexual practices associated with acculturation. (+info)
Genetically distinct dog-derived and human-derived Sarcoptes scabiei in scabies-endemic communities in northern Australia.
Overcrowding is a significant factor contributing to endemic infection with Sarcoptes scabiei in human and animal populations. However, since scabies mites from different host species are indistinguishable morphologically, it is unclear whether people can be infected from scabies-infested animals. Molecular fingerprinting was done using three S. scabiei-specific single locus hypervariable microsatellite markers, with a combined total of 70 known alleles. Multilocus analysis of 712 scabies mites from human and dog hosts in Ohio, Panama and Aboriginal communities in northern Australia now shows that genotypes of dog-derived and human-derived scabies cluster by host species rather than by geographic location. Because of the apparent genetic separation between human scabies and dog scabies, control programs for human scabies in endemic areas do not require resources directed against zoonotic infection from dogs. (+info)
Hantavirus pulmonary syndrome (HPS) is an acute viral rodentborne zoonosis characterized by severe cardiopulmonary illness with a 40%-60% case-fatality rate. Since its identification in the United States in 1993, the recognized clinical spectrum of illnesses associated with human hantavirus infection has expanded to include mild illness, and case-patients have been identified in Canada and South America. This report describes the first confirmed HPS cases from Central America and summarizes preliminary results of clinical, epidemiologic, and ecologic investigations. Investigators identified 12 suspected cases with typical disease and captured four common species of rodents near case households. (+info)
Spatial patterns in the distribution of tropical tree species.
Fully mapped tree census plots of large area, 25 to 52 hectares, have now been completed at six different sites in tropical forests, including dry deciduous to wet evergreen forest on two continents. One of the main goals of these plots has been to evaluate spatial patterns in tropical tree populations. Here the degree of aggregation in the distribution of 1768 tree species is examined based on the average density of conspecific trees in circular neighborhoods around each tree. When all individuals larger than 1 centimeter in stem diameter were included, nearly every species was more aggregated than a random distribution. Considering only larger trees (>/= 10 centimeters in diameter), the pattern persisted, with most species being more aggregated than random. Rare species were more aggregated than common species. All six forests were very similar in all the particulars of these results. (+info)
Relationships of bradyrhizobia from Platypodium and Machaerium (Papilionoideae: tribe Dalbergieae) on Barro Colorado Island, Panama.
Enzyme electrophoresis and rRNA sequencing indicated that root nodule bacteria from the canopy tree Platypodium elegans and the lianas Machaerium milleflorum and Machaerium arboreum on Barro Colorado Island, Panama, were highly diverse on a local scale. A total of 11 distinct multilocus genotypes [ETs (electrophoretic types)] was found among the 33 isolates analysed. On average, ETs differed from one another at 74% of the 11 enzyme loci assayed, and separate nodules on a single host individual were often occupied by genetically divergent ETs. Certain ETs were sampled multiple times from both Platypodium and Machaerium, suggesting a lack of specificity toward the two legume genera. Within the intervening sequence (IVS) region in the 5' end of 23S rRNA, seven ETs had a length variant similar to that of Bradyrhizobium japonicum USDA 110, and the other four ETs had an IVS region 26-28 bp shorter. Parsimony analysis of both partial 23S rRNA and nearly full-length 16S rRNA sequences indicated that all Platypodium and Machaerium isolates were related to B. japonicum rather than Bradyrhizobium elkanii. The 16S rRNA sequence of one isolate was >99% similar to that of B. japonicum USDA 110, and the closest known relatives for other isolates were Philippine bradyrhizobia from the legumes Stylosanthes and Samanea. (+info)