| 1. |
- Bray, Daniel
(författare)
-
Multi-modal Analysis of Courtship Behaviour in the Old World Leishmaniasis Vector Phlebotomus argentipes
- 2014
-
Ingår i: PLoS Neglected Tropical Diseases. - : Public Library of Science (PLoS). - 1935-2727 .- 1935-2735. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The sand fly Phlebotomus argentipes is arguably the most important vector of leishmaniasis worldwide. As there is no vaccine against the parasites that cause leishmaniasis, disease prevention focuses on control of the insect vector. Understanding reproductive behaviour will be essential to controlling populations of P. argentipes, and developing new strategies for reducing leishmaniasis transmission. Through statistical analysis of male-female interactions, this study provides a detailed description of P. argentipes courtship, and behaviours critical to mating success are highlighted. The potential for a role of cuticular hydrocarbons in P. argentipes courtship is also investigated, by comparing chemicals extracted from the surface of male and female flies.Principal Findings: P. argentipes courtship shared many similarities with that of both Phlebotomus papatasi and the New World leishmaniasis vector Lutzomyia longipalpis. Male wing-flapping while approaching the female during courtship predicted mating success, and touching between males and females was a common and frequent occurrence. Both sexes were able to reject a potential partner. Significant differences were found in the profile of chemicals extracted from the surface of males and females. Results of GC analysis indicate that female extracts contained a number of peaks with relatively short retention times not present in males. Extracts from males had higher peaks for chemicals with relatively long retention times.Conclusions: The importance of male approach flapping suggests that production of audio signals through wing beating, or dispersal of sex pheromones, are important to mating in this species. Frequent touching as a means of communication, and the differences in the chemical profiles extracted from males and females, may also indicate a role for cuticular hydrocarbons in P. argentipes courtship. Comparing characteristics of successful and unsuccessful mates could aid in identifying the modality of signals involved in P. argentipes courtship, and their potential for use in developing new strategies for vector control.
|
|
| 2. |
- Carrasco, David
(författare)
-
Trypanosomes Modify the Behavior of Their Insect Hosts: Effects on Locomotion and on the Expression of a Related Gene
- 2015
-
Ingår i: PLoS Neglected Tropical Diseases. - : Public Library of Science (PLoS). - 1935-2727 .- 1935-2735. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- BackgroundAs a result of evolution, the biology of triatomines must have been significantly adapted to accommodate trypanosome infection in a complex network of vector-vertebrate-parasite interactions. Arthropod-borne parasites have probably developed mechanisms, largely still unknown, to exploit the vector-vertebrate host interactions to ensure their transmission to suitable hosts. Triatomines exhibit a strong negative phototaxis and nocturnal activity, believed to be important for insect survival against its predators.Methodology/Principal FindingsIn this study we quantified phototaxis and locomotion in starved fifth instar nymphs of Rhodnius prolixus infected with Trypanosoma cruzi or Trypanosoma rangeli. T. cruzi infection did not alter insect phototaxis, but induced an overall 20% decrease in the number of bug locomotory events. Furthermore, the significant differences induced by this parasite were concentrated at the beginning of the scotophase. Conversely, T. rangeli modified both behaviors, as it significantly decreased bug negative phototaxis, while it induced a 23% increase in the number of locomotory events in infected bugs. In this case, the significant effects were observed during the photophase. We also investigated the expression of Rpfor, the triatomine ortholog of the foraging gene known to modulate locomotion in other insects, and found a 4.8 fold increase for T. rangeli infected insects.Conclusions/SignificanceWe demonstrated for the first time that trypanosome infection modulates the locomotory activity of the invertebrate host. T. rangeli infection seems to be more broadly effective, as besides affecting the intensity of locomotion this parasite also diminished negative phototaxis and the expression of a behavior-associated gene in the triatomine vector.
|
|
| 3. |
- Ha, Tuyen V., et al.
(författare)
-
Spatial distribution of Culex mosquito abundance and associated risk factors in Hanoi, Vietnam
- 2021
-
Ingår i: PLoS Neglected Tropical Diseases. - : Public Library of Science (PLoS). - 1935-2727 .- 1935-2735. ; 15:6
-
Tidskriftsartikel (refereegranskat)abstract
- Japanese encephalitis (JE) is the major cause of viral encephalitis (VE) in most AsianPacific countries. In Vietnam, there is no nationwide surveillance system for JE due to lack of medical facilities and diagnoses. Culex tritaeniorhynchus, Culex vishnui, and Culex quin-quefasciatus have been identified as the major JE vectors in Vietnam. The main objective of this study was to forecast a risk map of Culex mosquitoes in Hanoi, which is one of the most densely populated cities in Vietnam. A total of 10,775 female adult Culex mosquitoes were collected from 513 trapping locations. We collected temperature and precipitation information during the study period and its preceding month. In addition, the other predictor variables (e.g., normalized difference vegetation index [NDVI], land use/land cover and human population density), were collected for our analysis. The final model selected for estimating the Culex mosquito abundance included centered rainfall, quadratic term rainfall, rice cover ratio, forest cover ratio, and human population density variables. The estimated spatial distribution of Culex mosquito abundance ranged from 0 to more than 200 mosquitoes per 900m2. Our model estimated that 87% of the Hanoi area had an abundance of mosquitoes from 0 to 50, whereas approximately 1.2% of the area showed more than 150 mosquitoes, which was mostly in the rural/peri-urban districts. Our findings provide better insight into understanding the spatial distribution of Culex mosquitoes and its associated environmental risk factors. Such information can assist local clinicians and public health policymakers to identify potential areas of risk for JE virus. Risk maps can be an efficient way of raising public awareness about the virus and further preventive measures need to be considered in order to prevent outbreaks and onwards transmission of JE virus.
|
|
| 4. |
- Khalil, Hussein
(författare)
-
Poverty, sanitation, and Leptospira transmission pathways in residents from four Brazilian slums
- 2021
-
Ingår i: PLoS Neglected Tropical Diseases. - : Public Library of Science (PLoS). - 1935-2727 .- 1935-2735. ; 15
-
Tidskriftsartikel (refereegranskat)abstract
- Author summaryGlobally, more than 1 billion residents live in urban slums, where inadequate sanitation increases the spread of pathogens and their animal hosts. Leptospirosis is a globally distributed bacterial disease, and in urban areas the bacteria is spread by brown rats. Humans become infected upon exposure to water or soil/mud that was contaminated with the urine of infected rats. In four urban slums in the city of Salvador, Brazil, we used a range of individual, socioeconomic, and environmental variables to understand how they influence to one another and define o leptospirosis exposure in residents. Poverty and sanitation influenced the degree to which residents were exposed to sewer water and mud. Further, we found that while residents tried to improve the physical environment near their household, living in an area with poor sanitation mean that their infection risk remained high. This work highlight the importance of socioeconomic and environmental factors in determining disease risk, and suggests that governmental interventions should focus on improving sanitation changes in the poorest parts of the community.Residents of urban slums suffer from a high burden of zoonotic diseases due to individual, socioeconomic, and environmental factors. We conducted a cross-sectional sero-survey in four urban slums in Salvador, Brazil, to characterize how poverty and sanitation contribute to the transmission of rat-borne leptospirosis. Sero-prevalence in the 1,318 participants ranged between 10.0 and 13.3%. We found that contact with environmental sources of contamination, rather than presence of rat reservoirs, is what leads to higher risk for residents living in areas with inadequate sanitation. Further, poorer residents may be exposed away from the household, and ongoing governmental interventions were not associated with lower transmission risk. Residents at higher risk were aware of their vulnerability, and their efforts improved the physical environment near their household, but did not reduce their infection chances. This study highlights the importance of understanding the socioeconomic and environmental determinants of risk, which ought to guide intervention efforts.
|
|
| 5. |
- Lindahl, Johanna
(författare)
-
A systematic review and meta-analysis of the aetiological agents of non-malarial febrile illnesses in Africa
- 2022
-
Ingår i: PLoS Neglected Tropical Diseases. - 1935-2727 .- 1935-2735. ; 16
-
Tidskriftsartikel (refereegranskat)abstract
- BackgroundThe awareness of non-malarial febrile illnesses (NMFIs) has been on the rise over the last decades. Therefore, we undertook a systematic literature review and meta-analysis of causative agents of non-malarial fevers on the African continent.MethodologyWe searched for literature in African Journals Online, EMBASE, PubMed, Scopus, and Web of Science databases to identify aetiologic agents that had been reported and to determine summary estimates of the proportional morbidity rates (PMr) associated with these pathogens among fever patients.FindingsA total of 133 studies comprising 391,835 patients from 25 of the 54 African countries were eligible. A wide array of aetiologic agents were described with considerable regional differences among the leading agents. Overall, bacterial pathogens tested from blood samples accounted for the largest proportion. The summary estimates from the meta-analysis were low for most of the agents. This may have resulted from a true low prevalence of the agents, the failure to test for many agents or the low sensitivity of the diagnostic methods applied. Our meta-regression analysis of study and population variables showed that diagnostic methods determined the PMr estimates of typhoidal Salmonella and Dengue virus. An increase in the PMr of Klebsiella spp. infections was observed over time. Furthermore, the status of patients as either inpatient or outpatient predicted the PMr of Haemophilus spp. infections.ConclusionThe small number of epidemiological studies and the variety of NMFI agents on the African continent emphasizes the need for harmonized studies with larger sample sizes. In particular, diagnostic procedures for NMFIs should be standardized to facilitate comparability of study results and to improve future meta-analyses. Reliable NMFI burden estimates will inform regional public health strategies.
|
|
| 6. |
- Lindahl, Johanna, et al.
(författare)
-
Circulation of Japanese Encephalitis Virus in Pigs and Mosquito Vectors within Can Tho City, Vietnam
- 2013
-
Ingår i: PLoS Neglected Tropical Diseases. - : Public Library of Science (PLoS). - 1935-2727 .- 1935-2735. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Japanese encephalitis virus (JEV) is a mosquito-borne, zoonotic flavivirus causing encephalitis in humans and reproductive disorder in pigs. JEV is present in large parts of Asia, where urbanization is high. Households within and outside Can Tho city, South Vietnam, were selected to monitor circulation of JEV. A nested RT-PCR was established to detect the presence of JEV in mosquitoes whereas sera from pigs belonging to households within the province were analyzed for the presence of antibodies to JEV. A total of 7885 mosquitoes were collected and divided into 352 pools whereof seven were JEV-positive, six of which were collected within the city. Fragments from four pools clustered with JEV genotype III and three with genotype I. Of the 43 pigs sampled inside the city 100% had JEV antibodies. Our study demonstrates exposure to JEV in pigs, and co-circulation of JEV genotype I and III in mosquitoes within an urban environment in South Vietnam. Thus, although JEV has mainly been considered a rural disease, the potential for transmission in urban areas cannot be ignored.
|
|
| 7. |
- Lindahl Rajala, Elisabeth, et al.
(författare)
-
Detection and characterization of Brucella spp. in bovine milk in small-scale urban and peri-urban farming in Tajikistan
- 2017
-
Ingår i: PLoS Neglected Tropical Diseases. - : Public Library of Science (PLoS). - 1935-2727 .- 1935-2735. ; 11:3
-
Tidskriftsartikel (refereegranskat)abstract
- Brucellosis is one of the most common zoonoses globally, and Central Asia remains a Brucella hotspot. The World Health Organization classifies brucellosis as a neglected zoonotic disease that is rarely in the spotlight for research and mainly affects poor, marginalized people. Urban and peri-urban farming is a common practice in many low-income countries, and it increases the incomes of families that are often restrained by limited economic resources. However, there is a concern that the growing number of people and livestock living close together in these areas will increase the transmission of zoonotic pathogens such as Brucella. This study investigates the presence of Brucella DNA in bovine milk in the urban and peri-urban area of Dushanbe, Tajikistan. Brucella DNA was detected in 10.3% of 564 cow milk samples by IS711-based real-time PCR. This finding is concerning because consumption of unpasteurized dairy products is common in the region. Furthermore, Brucella DNA was detected in the milk of all seropositive cows, but 8.3% of the seronegative cows also showed the presence of Brucella DNA. In addition, sequence analysis of the rpoB gene suggests that one cow was infected with B. abortus and another cow was most likely infected with B. melitensis. The discrepancies between the serology and real-time PCR results highlight the need to further investigate whether there is a need for implementing complementary diagnostic strategies to detect false serological negative individuals in Brucella surveillance, control, and eradication programmes. Furthermore, vaccination of cattle with S19 in addition to vaccination of small ruminants with Rev 1 might be needed in order to control Brucella infections in the livestock population but further research focusing on the isolation of Brucella is required to obtain a comprehensive understanding of the Brucella spp. circulating among the livestock in this region.
|
|
| 8. |
- Lundström, Jan O, et al.
(författare)
-
Sindbis virus polyarthritis outbreak signalled by virus prevalence in the mosquito vectors
- 2019
-
Ingår i: PLoS Neglected Tropical Diseases. - : Public Library of Science (PLoS). - 1935-2727 .- 1935-2735. ; 13:8
-
Tidskriftsartikel (refereegranskat)abstract
- Polyarthritis and rash caused by Sindbis virus (SINV), was first recognised in northern Europe about 50 years ago and is known as Ockelbo disease in Sweden and Pogosta disease in Finland. This mosquito-borne virus occurs mainly in tropical and sub-tropical countries, and in northern Europe it is suggested to cause regularly reoccurring outbreaks. Here a seven-year cycle of SINV outbreaks has been referred to in scientific papers, although the hypothesis is based solely on reported human cases. In the search for a more objective outbreak signal, we evaluated mosquito abundance and SINV prevalence in vector mosquitoes from an endemic area in central Sweden. Vector mosquitoes collected in the River Dalalven floodplains during the years before, during, and after the hypothesised 2002 outbreak year were assayed for virus on cell culture. Obtained isolates were partially sequenced, and the nucleotide sequences analysed using Bayesian maximum clade credibility and median joining network analysis. Only one SINV strain was recovered in 2001, and 4 strains in 2003, while 15 strains were recovered in 2002 with significantly increased infection rates in both the enzootic and the bridge-vectors. In 2002, the Maximum Likelihood Estimated infection rates were 10.0/1000 in the enzootic vectors Culex torrentium/pipiens, and 0.62/1000 in the bridge-vector Aedes cinereus, compared to 4.9/1000 and 0.0/1000 in 2001 and 0.0/1000 and 0.32/1000 in 2003 Sequence analysis showed that all isolates belonged to the SINV genotype I (SINV-I). The genetic analysis revealed local maintenance of four SINV-I clades in the River Dalalven floodplains over the years. Our findings suggest that increased SINV-I prevalence in vector mosquitoes constitutes the most valuable outbreak marker for further scrutinising the hypothesized seven-year cycle of SINV-I outbreaks and the mechanisms behind.
|
|
| 9. |
- Mwololo, Damaris, et al.
(författare)
-
Sero-epidemiological survey of Coxiella burnetii in livestock and humans in Tana river and garissa counties in Kenya
- 2022
-
Ingår i: PLoS Neglected Tropical Diseases. - : PUBLIC LIBRARY SCIENCE. - 1935-2727 .- 1935-2735. ; 16:3
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Coxiella burnetii is a widely distributed pathogen, but data on its epidemiology in livestock, and human populations remains scanty, especially in developing countries such as Kenya. We used the One Health approach to estimate the seroprevalance of C. burnetii in cattle, sheep, goats and human populations in Tana River county, and in humans in Garissa county, Kenya. We also identified potential determinants of exposure among these hosts.Methods: Data were collected through a cross-sectional study with a cluster sampling design. Serum samples were taken from 2,727 animals (466 cattle, 1,333 goats, and 928 sheep) and 974 humans and screened for Phase I/II IgG antibodies against C. burnetii using enzyme-linked immunosorbent assay (ELISA). Data on potential factors associated with animal and human exposure were collected using a structured questionnaire. Multivariable analyses were performed with households as random effects to adjust for the within-household correlation of C. burnetii exposure among animals and humans, respectively.Results: The overall apparent seroprevalence estimates of C. burnetii in livestock and humans were 12.80% (95% confidence interval [CI]: 11.57-14.11) and 24.44% (95% CI: 21.77-27.26), respectively. In livestock, the seroprevalence differed significantly by species (p < 0.01). The highest seroprevalence estimates were observed in goats 15.22% (95% CI: 13.34-17.27), then sheep 14.22% (95% CI: 12.04-16.64) and with cattle 3.00% (95% CI; 1.65-4.99) showing lower values. Herd-level seropositivity of C. burnetii in livestock was not positively associated with human exposure. Multivariable results showed that female animals had higher odds of seropositivity for C. burnetii than males, while for animal age groups, adult animals had higher odds of seropositivity than calves, kids or lambs. For livestock species, both sheep and goats had significantly higher odds of seropositivity than cattle. In human populations, men had a significantly higher odds of testing positive for C. burnetii than women.Conclusions: This study provides evidence of livestock and human exposure to C. burnetii which could have serious economic implications on livestock production and impact on human health. These results also highlight the need to establish active surveillance in the study area to reduce the disease burden associated with this pathogen.
|
|
| 10. |
- Schorkopf, Dirk louis, et al.
(författare)
-
Combining Attractants and Larvicides in Biodegradable Matrices for Sustainable Mosquito Vector Control
- 2016
-
Ingår i: PLoS Neglected Tropical Diseases. - : Public Library of Science (PLoS). - 1935-2727 .- 1935-2735. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- BackgroundThere is a global need for cost-effective and environmentally friendly tools for control of mosquitoes and mosquito-borne diseases. One potential way to achieve this is to combine already available tools to gain synergistic effects to reduce vector mosquito populations. Another possible way to improve mosquito control is to extend the active period of a given control agent, enabling less frequent applications and consequently, more efficient and longer lasting vector population suppression.Methodology/principal findingsWe investigated the potential of biodegradable wax emulsions to improve the performance of semiochemical attractants for gravid female culicine vectors of disease, as well as to achieve more effective control of their aquatic larval offspring. As an attractant for gravid females, we selected acetoxy hexadecanolide (AHD), the Culex oviposition pheromone. As toxicant for mosquito larvae, we chose the biological larvicides Bacillus thuringiensis israelensis (Bti) and Bacillus sphaericus (Bs). These attractant and larvicidal agents were incorporated, separately and in combination, into a biodegradable wax emulsion, a commercially available product called SPLAT (Specialized Pheromone & Lure Application Technology) and SPLATbac, which contains 8.33% Bti and 8.33% Bs. Wax emulsions were applied to water surfaces as buoyant pellets of 20 mg each. Dose-mortality analyses of Culex quinquefasciatus Say larvae demonstrated that a single 20 mg pellet of a 10(-1) dilution of SPLATbac in a larval tray containing 1 L of water caused 100% mortality of neonate (1st instar) larvae for at least five weeks after application. Mortality of 3rd instar larvae remained equally high with SPLATbac dilutions down to 10(-2) for over two weeks post application. Subsequently, AHD was added to SPLAT (emulsion only, without Bs or Bti) to attract gravid females (SPLATahd), or together with biological larvicides to attract ovipositing females and kill emerging larvae (SPLATbacAHD, 10(-1) dilution) in both laboratory and semi-field settings. The formulations containing AHD, irrespective of presence of larvicides, were strongly preferred as an oviposition substrate by gravid female mosquitoes over controls for more than two weeks post application. Experiments conducted under semi-field settings (large screened greenhouse, emulating field conditions) confirmed the results obtained in the laboratory. The combination of attractant and larvicidal agents in a single formulation resulted in a substantial increase in larval mosquito mortality when compared to formulations containing the larvicide agents alone. Conclusions/significanceCollectively, our data demonstrate the potential for the effective use of wax emulsions as slow release matrices for mosquito attractants and control agents. The results indicate that the combination of an oviposition attractant with larvicides could synergize the control of mosquito disease vectors, specifically Cx. quinquefasciatus, a nuisance pest and circumtropical vector of lymphatic filariasis and encephalitis.
|
|
