Rapid and sensitive detection of Bartonella bacilliformis in experimentally infected sand flies by loop-mediated isothermal amplification (LAMP) of the Pap31 gene.

BACKGROUND: Carrion' disease, caused by Bartonella bacilliformis, remains truly neglected due to its focal geographical nature. A wide spectrum of clinical manifestations, including asymptomatic bacteremia, and lack of a sensitive diagnostic test can potentially lead to a spread of the disease into non-endemic regions where competent sand fly vectors may be present. A reliable test capable of detecting B. bacilliformis is urgently needed. Our objective is to develop a loop-mediated isothermal amplification (LAMP) assay targeting the pap31 gene to detect B. bacilliformis. METHODS AND FINDINGS: The sensitivity of the LAMP was evaluated in comparison to qPCR using plasmid DNA containing the target gene and genomic DNA in the absence and presence of human or sand fly DNA. The detection limit of LAMP was 1 to 10 copies/µL, depending on the sample metrics. No cross-reaction was observed when testing against a panel of various closely related bacteria. The utility of the LAMP was further compared to qPCR by the examination of 74 Lutzomyia longipalpis sand flies artificially fed on blood spiked with B. bacilliformis and harvested at days (D) 1, 3, 5, 7 and 9 post feeding. Only 86% of sand flies at D1 and 63% of flies at D3 were positive by qPCR. LAMP was able to detect B. bacilliformis in all those flies confirmed positive by qPCR. However, none of the flies after D3 were positive by either LAMP or qPCR. In addition to demonstrating the sensitivity of the LAMP assay, these results suggest that B. bacilliformis cannot propagate in artificially fed L. longipalpis. CONCLUSIONS: The LAMP assay is as sensitive as qPCR for the detection of B. bacilliformis and could be useful to support diagnosis of patients in low-resource settings and also to identify B. bacilliformis in the sand fly vector.

Mosquito vector abundance immediately before and after tropical storms Alma and Arthur, northern Belize, 2008.

OBJECTIVE: To monitor adult mosquito abundance in northern Belize before/after the first tropical storm of the wet season to estimate the time required for development/recovery of potential vector populations; determine which species predominate post-storm; and compare the effectiveness of two types of mosquito traps-octenol-baited Mosquito Magnets® and U.S. Centers for Disease Control and Prevention (CDC) light traps (with/without octenol). METHODS: Field experiments were conducted in Orange Walk Town, Belize, 21 May to 3 June 2008. Incidence rate ratios and exact binomial 95% confidence intervals were reported and trap-nights calculated to compare species abundance pre- and post-storm as well as trap-type effectiveness. RESULTS: Twice as many species and three times more Anopheles spp. were trapped pre-storm versus post-storm. However, greater numbers of Aedes taeniorhynchus and Culex (Culex) spp. were trapped post-storm. Mosquito Magnets® were consistently more effective than the CDC traps, obtaining twice as many Anopheles spp. and four times as many culicine species as the octenol-baited version (which collected 14 times more mosquitoes overall and 3.5 times more culicine species than the unbaited version). The unbaited CDC trap did not trap any Anopheles spp. during the study period. CONCLUSIONS: Results indicated octenol is an effective attractant for An. crucians in northern Belize; malaria risk in Belize declines immediately post-storm (i.e., mosquito abundance drops); and arboviral risk associated with the rapid increase in culicine mosquitoes post-storm may represent a greater public health threat than malaria (although further research and active disease surveillance is necessary to validate this hypothesis).

Mosquito vector abundance immediately before and after tropical storms Alma and Arthur, northern Belize, 2008 / Abundancia de mosquitos vectores inmediatamente antes y después de las tormentas tropicales Alma y Arthur, norte de Belice, 2008

OBJECTIVE: To monitor adult mosquito abundance in northern Belize before/after the first tropical storm of the wet season to estimate the time required for development/recovery of potential vector populations; determine which species predominate post-storm; and compare the effectiveness of two types of mosquito traps-octenol-baited Mosquito Magnets® and U.S. Centers for Disease Control and Prevention (CDC) light traps (with/without octenol). METHODS: Field experiments were conducted in Orange Walk Town, Belize, 21 May to 3 June 2008. Incidence rate ratios and exact binomial 95 percent confidence intervals were reported and trap-nights calculated to compare species abundance pre- and post-storm as well as trap-type effectiveness. RESULTS: Twice as many species and three times more Anopheles spp. were trapped pre-storm versus post-storm. However, greater numbers of Aedes taeniorhynchus and Culex (Culex) spp. were trapped post-storm. Mosquito Magnets® were consistently more effective than the CDC traps, obtaining twice as many Anopheles spp. and four times as many culicine species as the octenol-baited version (which collected 14 times more mosquitoes overall and 3.5 times more culicine species than the unbaited version). The unbaited CDC trap did not trap any Anopheles spp. during the study period. CONCLUSIONS: Results indicated octenol is an effective attractant for An. crucians in northern Belize; malaria risk in Belize declines immediately post-storm (i.e., mosquito abundance drops); and arboviral risk associated with the rapid increase in culicine mosquitoes post-storm may represent a greater public health threat than malaria (although further research and active disease surveillance is necessary to validate this hypothesis).

OBJETIVO: Comprobar la abundancia de mosquitos adultos en el norte de Belice antes y después de la primera tormenta tropical de la temporada de lluvias, para calcular la cantidad de tiempo que necesitan las poblaciones de vectores potenciales para desarrollarse y recuperarse; determinar cuáles son las especies que predominan después de la tormenta; y comparar la eficacia de dos tipos de trampas de mosquitos: las que utilizan cebos de octenol (Mosquito Magnets®) y las trampas de luz con y sin octenol de los Centros para el Control y la Prevención de Enfermedades de los Estados Unidos (CDC). MÉTODOS: Se llevaron a cabo pruebas de campo en Orange Walk Town, Belice, desde el 21 de mayo hasta el 3 de junio del 2008. Se registraron las razones de las tasas de incidencia y los intervalos de confianza binomiales exactos de 95 por ciento y se evaluaron las trampas nocturnas para comparar la abundancia de las especies y la eficacia del tipo de trampa antes y después de una tormenta. RESULTADOS: Antes de la tormenta, se atrapó el doble de las especies de mosquitos y el triple de Anopheles spp. en comparación con el período que siguió a la tormenta. Sin embargo, el número de Aedes taeniorhynchus y Culex (Culex) spp. atrapados fue mayor después de la tormenta. Las trampas Mosquito Magnets® demostraron uniformemente ser más eficaces que las trampas de los CDC, ya que el número de Anopheles spp. capturados fue dos veces mayor que el de la trampa con cebo de octenol y el número de especies de culícidos fue cuatro veces mayor. En general, el número de mosquitos capturados por la trampa con octenol fue 14 veces mayor que el de la trampa sin octenol y el número de especies de culícidos fue 3,5 veces mayor. La trampa sin cebo de los CDC no capturó ningún Anopheles spp. durante el período de estudio. CONCLUSIONES: Los resultados demostraron que el octenol es un producto eficaz para atraer a la especie Anopheles crucians en el norte de Belice. En este país, el riesgo de malaria disminuye inmediatamente después de las tormentas (es decir, disminuye la abundancia de mosquitos); y el riesgo de contraer una infección por arbovirus, asociado con el rápido aumento de las especies de culícidos después de las tormentas, podría representar una mayor amenaza para la salud pública que la malaria (aunque se necesitaría más investigación y una vigilancia activa de las enfermedades para validar esta hipótesis).

Failure of interior residual sprays as protection against mosquitoes in military-issued two-man tents.

Most studies on interior (or indoor) residual spraying (IRS) have been targeted on permanent/semipermanent structures. We measured the utility of a portable field bioassay, which can be set up quickly to determine the best chemical repellent or irritant for use as an IRS during an emergency or military situation when displaced persons are temporarily housed in tents. If the bioassay were used over an extended period of time, it would also offer a unique way to monitor vector susceptibility and would be able to determine which chemical is most efficient in individual populations. In total, 2193 mosquitoes belonging to seven species in five genera were collected over the study period. No statistical differences were found between any of the treatments, control, and standard tents utilizing the 4 x 4 Latin square design. Therefore, we conclude that IRS with these tested chemicals in military-issued two-person tents are not effective or significant at stopping mosquito entrance. Further studies on implementation of a portable, field bioassay should include utilizing different mosquito traps in the bioassay and looking at the difference between contact irritants and spatial repellents in different-sized tents, as spatial repellency may be more important in smaller-sized tents.