Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: an emerging tool for studying the vectors of human infectious diseases.

Arthropod vectors have historically been identified morphologically, and more recently using molecular biology methods. However, both of these methods are time-consuming and require specific expertise and equipment. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry, which has revolutionized the routine identification of microorganisms in clinical microbiology laboratories, was recently successfully applied to the identification of arthropod vectors. Since then, the robustness of this identification technique has been confirmed, extended to a large panel of arthropod vectors, and assessed for detecting blood feeding behavior and identifying the infection status in regard to certain pathogenic agents. In this study, we summarize the state-of-the-art of matrix-assisted laser desorption ionization time-of-flight mass spectrometry applied to the identification of arthropod vectors (ticks, mosquitoes, phlebotomine sand-flies, fleas, triatomines, lice and Culicoides), their trophic preferences and their ability to discriminate between infection statuses.

Using MALDI-TOF MS to identify mosquitoes collected in Mali and their blood meals.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been recently described as an innovative and effective tool for identifying arthropods and mosquito blood meal sources. To test this approach in the context of an entomological survey in the field, mosquitoes were collected from five ecologically distinct areas of Mali. We successfully analysed the blood meals from 651 mosquito abdomens crushed on Whatman filter paper (WFPs) in the field using MALDI-TOF MS. The legs of 826 mosquitoes were then submitted for MALDI-TOF MS analysis in order to identify the different mosquito species. Eight mosquito species were identified, including Anopheles gambiae Giles, Anopheles coluzzii, Anopheles arabiensis, Culex quinquefasciatus, Culex neavei, Culex perexiguus, Aedes aegypti and Aedes fowleri in Mali. The field mosquitoes for which MALDI-TOF MS did not provide successful identification were not previously available in our database. These specimens were subsequently molecularly identified. The WFP blood meal sources found in this study were matched against human blood (n = 619), chicken blood (n = 9), cow blood (n = 9), donkey blood (n = 6), dog blood (n = 5) and sheep blood (n = 3). This study reinforces the fact that MALDI-TOF MS is a promising tool for entomological surveys.

Spatial Patterns of Plasmodium falciparum Clinical Incidence, Asymptomatic Parasite Carriage and Anopheles Density in Two Villages in Mali.

Heterogeneity in malaria exposure is most readily recognized in areas with low-transmission patterns. By comparison, little research has been done on spatial patterns in malaria exposure in high-endemic settings. We determined the spatial clustering of clinical malaria incidence, asymptomatic parasite carriage, and Anopheles density in two villages in Mali exposed to low- and mesoendemic-malaria transmission. In the two study areas that were < 1 km(2) in size, we observed evidence for spatial clustering of Anopheles densities or malaria parasite carriage during the dry season. Anopheles density and malaria prevalence appeared associated in some of our detected hotspots. However, many households with high parasite prevalence or high Anopheles densities were located outside the identified hotspots. Our findings indicate that within small villages exposed to low- or mesoendemic-malaria transmission, spatial patterns in mosquito densities and parasite carriage are best detected in the dry season. Considering the high prevalence of parasite carriage outside detected hotspots, the suitability of the area for targeting control efforts to households or areas of more intense malaria transmission may be limited.

Urban schistosomiasis and associated determinant factors among school children in Bamako, Mali, West Africa.

BACKGROUND: Schistosomiasis is classically described as a rural disease that occurs in areas with poor sanitary conditions. However, over recent decades, there has been an expansion of schistosomiasis foci towards urban areas faced with a rapid and disordered urbanization. In Bamako, Mali, the impact of environmental change on vector-borne diseases such as schistosomiasis is not well known. This study sought to identify the presence of schistosomiasis transmission hotspots in Bamako. Using this perspective, we aimed to describe the risk factors of the endemization and maintenance of schistosomiasis. MATERIALS AND METHODS: A cross-sectional study was carried out in the six municipalities (communes) in Bamako. Environmental information was obtained from earth observation satellites in order to maximize ecological contrasts. Twenty-nine blocks of 200 m x 200 m were identified. We selected a school inside or nearest to each block for urine and stool samples examination. The study cohort was school children aged between eight and 15 years. The Kato-Katz technique and filtration were used for Schistosoma mansoni and S. haematobium ova research in stools and urine, respectively. The schools and snail breeding sites were georeferenced. Four malacological surveys were conducted between October 2011 and February 2012. Bivariate analysis was used to identify independent predictors of being infected with schistosomiasis. RESULTS: The prevalence rate of S. haematobium was 14.7% (n = 1,761) and that of S. mansoni 1.5% (n = 1,491). Overall, the urinary form was endemic in 76.6% of schools. The infection significantly varied between the municipalities (p < 0.001). It was also more prevalent on the left side of the Niger River than the right side (17.4% vs. 9.5% respectively; p < 0.001). The vicinity to snail breeding sites (OR = 3.677; 95% IC [2.765-4.889]; p < 10 (-3) ) and parents' occupations (OR = 7.647; 95% IC [2.406-24.305]; p < 0.001) were the most important risk factors associated with S. haematobium infection exposure. Biomphalaria pfeifferi, Bulinus truncatus, and B. globosus were the intermediate hosts captured. The schistosome natural infection rates (SNIRs), which were low or nil in October and November, rose to 2.8% in January and 8.3% in February for B. pfeifferi and B. truncatus, respectively. CONCLUSION: Our findings show that there is a high transmission risk for schistosomiasis in Bamako. Appropriate integrated control measures need to be introduced to control the transmission of this disease in the study area.

First detection of Leishmania major DNA in Sergentomyia (Spelaeomyia) darlingi from cutaneous leishmaniasis foci in Mali.

BACKGROUND: Leishmania major complex is the main causative agent of zoonotic cutaneous leishmaniasis (ZCL) in the Old World. Phlebotomus papatasi and Phlebotomus duboscqi are recognized vectors of L. major complex in Northern and Southern Sahara, respectively. In Mali, ZCL due to L. major is an emerging public health problem, with several cases reported from different parts of the country. The main objective of the present study was to identify the vectors of Leishmania major in the Bandiagara area, in Mali. METHODOLOGY/PRINCIPAL FINDINGS: An entomological survey was carried out in the ZCL foci of Bandiagara area. Sandflies were collected using CDC miniature light traps and sticky papers. In the field, live female Phlebotomine sandflies were identified and examined for the presence of promastigotes. The remaining sandflies were identified morphologically and tested for Leishmania by PCR in the ITS2 gene. The source of blood meal of the engorged females was determined using the cyt-b sequence. Out of the 3,259 collected sandflies, 1,324 were identified morphologically, and consisted of 20 species, of which four belonged to the genus Phlebotomus and 16 to the genus Sergentomyia. Leishmania major DNA was detected by PCR in 7 of the 446 females (1.6%), specifically 2 out of 115 Phlebotomus duboscqi specimens, and 5 from 198 Sergentomyia darlingi specimens. Human DNA was detected in one blood-fed female S. darlingi positive for L. major DNA. CONCLUSION: Our data suggest the possible involvement of P. duboscqi and potentially S. darlingi in the transmission of ZCL in Mali.