RESUMO
Following the recent discovery of Bourbon virus (BRBV) as a human pathogen, and the isolation of the virus from Amblyomma americanum (L.) collected near the location of a fatal human case, we undertook a series of experiments to assess the laboratory vector competence of this tick species for BRBV. Larval ticks were infected using an immersion technique, and transstadial transmission of virus to the nymphal and then to the adult stages was demonstrated. Transstadially infected nymphs transmitted virus to adult ticks at very high rates during cofeeding, indicating the presence of infectious virus in the saliva of engorging ticks. Vertical transmission by transstadially infected females to their progeny occurred, but at a low rate. Rabbits fed on by infected ticks of all active life stages developed high titers of antibody to the virus, demonstrating host exposure to BRBV antigens/live virus during tick blood feeding. These results demonstrate that A. americanum is a competent vector of BRBV and indicate that cofeeding could be critical for enzootic maintenance.
Assuntos
Amblyomma/virologia , Infecções por Orthomyxoviridae/transmissão , Thogotovirus , Experimentação Animal , Animais , Vetores Aracnídeos/virologia , Vetores de Doenças , Ixodidae/virologia , Coelhos , Saliva/virologiaRESUMO
BACKGROUND: The United States military regularly deploys thousands of service members throughout areas of South America and Africa that are endemic for yellow fever (YF) virus. To determine if booster doses might be needed for service members who are repetitively or continually deployed to YF endemic areas, we evaluated seropositivity among US military personnel receiving a single dose of YF vaccine based on time post-vaccination. METHODS: Serum antibodies were measured using a plaque reduction neutralization test with 50% cutoff in 682 military personnel at 5-39 years post-vaccination. We determined noninferiority of immune response by comparing the proportion seropositive among those vaccinated 10-14 years previously with those vaccinated 5-9 years previously. Noninferiority was supported if the lower-bound of the 2-tailed 95% CI for p10-14years - p5-9years was ≥-0.10. Additionally, the geometric mean antibody titer (GMT) at various timepoints following vaccination were compared to the GMT at 5-9 years. RESULTS: The proportion of military service members with detectable neutralizing antibodies 10-14 years after a single dose of YF vaccine (95.8%, 95% CI 91.2-98.1%) was non-inferior to the proportion 5-9 years after vaccination (97.8%, 95% CI 93.7-99.3%). Additionally, GMT among vaccine recipients at 10-14 years post vaccination (99, 95% CI 82-121) was non-inferior to GMT in YF vaccine recipients at 5-9 years post vaccination (115, 95% CI 96-139). The proportion of vaccinees with neutralizing antibodies remained high, and non-inferior, among those vaccinated 15-19 years prior (98.5%, 95%CI 95.5-99.7%). Although the proportion seropositive decreased among vaccinees ≥ 20 years post vaccination, >90% remained seropositive. CONCLUSIONS: Neutralizing antibodies were present in > 95% of vaccine recipients for at least 19 years after vaccination, suggesting that booster doses every 10 years are not essential for most U.S. military personnel.
Assuntos
Militares , Vacina contra Febre Amarela , Febre Amarela , África , Anticorpos Antivirais , Humanos , América do Sul , Vacinação , Febre Amarela/prevenção & controleRESUMO
When introduced into a naïve population, chikungunya virus generally spreads rapidly, causing large outbreaks of fever and severe polyarthralgia. We randomly selected households in the U.S. Virgin Islands (USVI) to estimate seroprevalence and symptomatic attack rate for chikungunya virus infection at approximately 1 year following the introduction of the virus. Eligible household members were administered a questionnaire and tested for chikungunya virus antibodies. Estimated proportions were calibrated to age and gender of the population. We enrolled 509 participants. The weighted infection rate was 31% (95% confidence interval [CI]: 26-36%). Among those with evidence of chikungunya virus infection, 72% (95% CI: 65-80%) reported symptomatic illness and 31% (95% CI: 23-38%) reported joint pain at least once per week approximately 1 year following the introduction of the virus to USVI. Comparing rates from infected and noninfected study participants, 70% (95% CI: 62-79%) of fever and polyarthralgia and 23% (95% CI: 9-37%) of continuing joint pain in patients infected with chikungunya virus were due to their infection. Overall, an estimated 43% (95% CI: 33-52%) of the febrile illness and polyarthralgia in the USVI population during the outbreak was attributable to chikungunya virus and only 12% (95% CI: 7-17%) of longer term joint pains were attributed to chikungunya virus. Although the rates of infection, symptomatic disease, and longer term joint symptoms identified in USVI are similar to other outbreaks of the disease, a lower proportion of acute fever and joint pain was found to be attributable to chikungunya virus.
Assuntos
Anticorpos Antivirais/sangue , Febre de Chikungunya/epidemiologia , Febre de Chikungunya/imunologia , Vírus Chikungunya/imunologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Artralgia/epidemiologia , Artralgia/virologia , Vírus Chikungunya/isolamento & purificação , Criança , Pré-Escolar , Surtos de Doenças , Características da Família , Feminino , Febre/epidemiologia , Febre/virologia , Humanos , Incidência , Lactente , Masculino , Pessoa de Meia-Idade , Estudos Soroepidemiológicos , Inquéritos e Questionários , Ilhas Virgens Americanas/epidemiologia , Adulto JovemRESUMO
Cross-reactivity within flavivirus antibody assays, produced by shared epitopes in the envelope proteins, can complicate the serological diagnosis of Zika virus (ZIKAV) infection. We assessed the utility of the plaque reduction neutralization test (PRNT) to confirm recent ZIKAV infections and rule out misleading positive immunoglobulin M (IgM) results in areas with various levels of past dengue virus (DENV) infection incidence. We reviewed PRNT results of sera collected for diagnosis of ZIKAV infection from 1 January through 31 August 2016 with positive ZIKAV IgM results, and ZIKAV and DENV PRNTs were performed. PRNT result interpretations included ZIKAV, unspecified flavivirus, DENV infection, or negative. For this analysis, ZIKAV IgM was considered false positive for samples interpreted as a DENV infection or negative. In U.S. states, 208 (27%) of 759 IgM-positive results were confirmed to be ZIKAV compared to 11 (21%) of 52 in the U.S. Virgin Islands (USVI), 15 (15%) of 103 in American Samoa, and 13 (11%) of 123 in Puerto Rico. In American Samoa and Puerto Rico, more than 80% of IgM-positive results were unspecified flavivirus infections. The false-positivity rate was 27% in U.S. states, 18% in the USVI, 2% in American Samoa, and 6% in Puerto Rico. In U.S. states, the PRNT provided a virus-specific diagnosis or ruled out infection in the majority of IgM-positive samples. Almost a third of ZIKAV IgM-positive results were not confirmed; therefore, providers and patients must understand that IgM results are preliminary. In territories with historically higher rates of DENV transmission, the PRNT usually could not differentiate between ZIKAV and DENV infections.
Assuntos
Anticorpos Antivirais/sangue , Vírus da Dengue/imunologia , Dengue/epidemiologia , Imunoglobulina M/sangue , Infecção por Zika virus/diagnóstico , Zika virus/imunologia , Samoa Americana/epidemiologia , Reações Cruzadas , Reações Falso-Positivas , Feminino , Flavivirus/imunologia , Humanos , Incidência , Masculino , Testes de Neutralização , Porto Rico/epidemiologia , Estados Unidos/epidemiologia , Ilhas Virgens Americanas/epidemiologia , Infecção por Zika virus/epidemiologia , Infecção por Zika virus/virologiaRESUMO
Chikungunya spread throughout the Dominican Republic (DR) after the first identified laboratory-confirmed cases were reported in April 2014. In June 2014, a U.S.-based service organization operating in the DR reported chikungunya-like illnesses among several staff. We assessed the incidence of chikungunya virus (CHIKV) and dengue virus (DENV) infection and illnesses and evaluated adherence to mosquito avoidance measures among volunteers/staff deployed in the DR who returned to the United States during July-August 2014. Investigation participants completed a questionnaire that collected information on demographics, medical history, self-reported illnesses, and mosquito exposures and avoidance behaviors and provided serum for CHIKV and DENV diagnostic testing by reverse transcription polymerase chain reaction and IgM enzyme-linked immunosorbent assay. Of 102 participants, 42 (41%) had evidence of recent CHIKV infection and two (2%) had evidence of recent DENV infection. Of the 41 participants with evidence of recent CHIKV infection only, 39 (95%) reported fever, 37 (90%) reported rash, and 37 (90%) reported joint pain during their assignment. All attended the organization's health trainings, and 89 (87%) sought a pretravel health consultation. Most (â¼95%) used insect repellent; however, only 30% applied it multiple times daily and < 5% stayed in housing with window/door screens. In sum, CHIKV infections were common among these volunteers during the 2014 chikungunya epidemic in the DR. Despite high levels of preparation, reported adherence to mosquito avoidance measures were inconsistent. Clinicians should discuss chikungunya with travelers visiting areas with ongoing CHIKV outbreaks and should consider chikungunya when diagnosing febrile illnesses in travelers returning from affected areas.