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1.
PLoS Negl Trop Dis ; 14(1): e0007862, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31978060

RESUMO

BACKGROUND: Lymphatic filariasis (LF) is targeted for elimination by the year 2020. As of 2017, 67 of the 72 endemic countries have implemented annual Mass Drug Administration (MDA) for interrupting LF transmission. Transmission Assessment Survey (TAS) is the recommended protocol to evaluate the impact of MDA and to decide when to stop MDA in an Evaluation Unit (EU, population ≤2 million). As the human infection levels go down with repeated MDA rounds, it becomes a challenge to select the appropriate survey methods to assess transmission interruption. This study validates a standard protocol for molecular xenomonitoring of infection in vectors (MX) at an EU as a complementary tool for TAS to stop MDA and its utility for post-MDA or post-validation surveillance. METHODOLOGY: The study was conducted in Cuddalore district, Tamil Nadu, India, which was found eligible for TAS after 15 annual rounds of MDA (4 with DEC alone and 11 with DEC plus albendazole). The district was divided into two EUs as per the TAS protocol and one EU was randomly selected for the study. A two-stage cluster design vector sampling, developed and validated at a sub-district level, was implemented in 30 randomly selected clusters in the EU. Female Culex quinquefasciatus were collected placing gravid traps overnight (1800-0600 hrs) inside the premises of systematically selected households. Pools of 20-25 blood-fed, semi-gravid and gravid Cx. quinquefasciatus were subjected to real-time quantitative PCR (polymerase chain reaction) assay for detecting Wuchereria bancrofti DNA. Pool infection rate (% of pools positive for W. bancrofti DNA), and the estimated prevalence of W. bancrofti DNA in mosquitoes and its 95% confidence interval were calculated. Additionally, in these 30 clusters, microfilaria (Mf) survey among individuals >5 years old was carried out. School-based TAS was conducted using Immunochromatographic Card Test (ICT) in the EU. Prepared itemized cost-menu for different cost components of MX survey and TAS were estimated and compared. RESULTS: MX survey showed that only 11 (3.1%) of the 358 pools (8850 Cx.quinquefasciatus females), collected from 30 clusters, were found positive for W. bancrofti DNA. The estimated vector infection rate was 0.13% (95% CI: 0.07-0.22%), below the provisional threshold (0.25%) for transmission interruption. Of 1578 children tested in the TAS, only four (0.25%) were positive for filarial antigenemia, and it is well below the critical cut-off (18 positives) for stopping MDA. Among 9804 persons tested in the 30 clusters, only four were found positive for Mf (0.04%; 95% CI: 0.01-0.1%). The Mf-prevalence was <1% threshold for transmission interruption in humans. The estimated costs for TAS and MX per EU were $14,104 USD and $14,259 USD respectively. CONCLUSIONS: The result of MX protocol was in good agreement with that of TAS, providing evidence to recommend MX as a complementary tool to TAS to decide on stopping MDA. MX can also be a potential surveillance tool for post-MDA and post-validation phases as it could detect sites with residual infection and risk of resurgence of transmission. MX is economically feasible as its cost is slightly higher than that of TAS.


Assuntos
Culex/parasitologia , DNA de Helmintos/análise , Filariose Linfática/prevenção & controle , Administração Massiva de Medicamentos , Wuchereria bancrofti/isolamento & purificação , Animais , Criança , Filariose Linfática/epidemiologia , Feminino , Humanos , Índia/epidemiologia , Mosquitos Vetores/parasitologia , Prevalência , Reação em Cadeia da Polimerase em Tempo Real , Wuchereria bancrofti/genética
2.
Acta Trop ; 199: 105121, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31400299

RESUMO

Lymphatic filariasis (LF) has been known in Egypt since ancient times. By 1930s it was recognized to be a major public health problem in the Nile Delta, and to be caused by Wuchereria bancrofti and transmitted by Culex pipiens. Remarkably, as a result of widespread DEC treatment and intensive vector control by the Ministry of Health and Population (MoHP), the infection rate of LF declined in the 1960s. However, relaxation of these efforts resulted in resurgence of filariasis in the 1980s and 1990s. In 2000, Egypt was among the first countries to join the WHO global efforts to eliminate LF as a public health problem by initiating a national LF elimination programme (NLFEP). This article reviews the history of LF control activities and summarizes the NLFEP extensive interventions to eliminate LF in Egypt. Based on MoHP data, mass drug administration (MDA) with DEC and ALB was started in 2000 in 161 implementation units (IUs). Additional IUs were included in subsequent MDA rounds, with the last IU included in 2007. MDA stopping surveys were conducted based on WHO guidelines (2005; 2011). Information about the presence of those suffering from lymphoedema/elephantiasis and hydrocele patients was collected, and care provided to those needing care in five rural health units (RHU) by primary health care system providers who were given training on LF morbidity management and disability prevention (MMDP). The NLFEP made excellent progress due to strong collaboration between different ministries, through intensive training and supervision, and the use of advocacy for mobilization of endemic communities. The epidemiological coverage for all MDA rounds was effectively ≥80%. Antigenemia levels found in schoolchildren during transmission assessment surveys (TAS) in 166 IUs approximately 10 years after stopping MDA was 0%. In 2017, TAS conducted in additional 29 IUs indicated 0.1% antigenemia and 0% microfilaremia. In 2015, the registration of chronic LF patients was updated to 1472 lymphoedema and 18 hydrocele patients. Lymphoedema patients were trained on self-management, and hydrocele patients were referred to local General Hospitals for surgery. Thus, after over a decade of sustained effort, Egypt met the WHO criteria for successful elimination of LF as a public health problem. In December 2017, WHO validated Egypt as the first country in the Eastern Mediterranean Region to successfully achieve elimination.


Assuntos
Culex/parasitologia , Filariose Linfática/prevenção & controle , Filaricidas/administração & dosagem , Mosquitos Vetores/parasitologia , Wuchereria bancrofti , Animais , Criança , Egito/epidemiologia , Filariose Linfática/epidemiologia , Filariose Linfática/transmissão , Filaricidas/farmacologia , Filaricidas/uso terapêutico , Humanos , Masculino , Administração Massiva de Medicamentos , Saúde Pública , Saúde da População Rural , Inquéritos e Questionários , Wuchereria bancrofti/efeitos dos fármacos
3.
Parasitol Res ; 118(7): 2097-2105, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31154526

RESUMO

In Germany, knowledge of disease agents transmitted by arthropods in zoological gardens is scarce. In the framework of ecological studies, mosquitoes were therefore collected in German zoological gardens and examined for mosquito-borne pathogen DNA and RNA. In total, 3840 mosquitoes were screened for filarial nematodes and three groups of viruses (orthobunyaviruses, flaviviruses, alphaviruses) while 405 mosquitoes were tested for avian malaria parasites. In addition to the filarial nematode species Dirofilaria repens (n = 1) and Setaria tundra (n = 8), Sindbis virus (n = 1) and the haemosporidian genera Haemoproteus (n = 8), Leucocytozoon (n = 10) and Plasmodium (n = 1) were demonstrated. Identified pathogens have the potential to cause disease in zoo and wild animals, but some of them also in humans. Positive mosquitoes were collected most often in July, indicating the highest infection risk during this month. Most of the pathogens were found in mosquito specimens of the Culex pipiens complex, suggesting that its members possibly act as the most important vectors in the surveyed zoos, although the mere demonstration of pathogen DNA/RNA in a homogenised complete mosquito is not finally indicative for a vector role. Outcomes of the study are not only significant for arthropod management in zoological gardens, but also for the general understanding of the occurrence and spread of mosquito-borne disease agents.


Assuntos
Culicidae/parasitologia , Filarioidea/classificação , Haemosporida/classificação , Malária Aviária/parasitologia , Mosquitos Vetores/parasitologia , Plasmodium/classificação , Animais , Culex/parasitologia , Feminino , Filarioidea/genética , Filarioidea/isolamento & purificação , Jardins , Alemanha/epidemiologia , Haemosporida/genética , Haemosporida/isolamento & purificação , Humanos , Malária Aviária/epidemiologia , Malária Aviária/transmissão , Plasmodium/genética , Plasmodium/isolamento & purificação
4.
Parasit Vectors ; 12(1): 295, 2019 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-31186055

RESUMO

BACKGROUND: Baseline information that is essential for determining the areas to target with larval control includes estimates of vector diversity and larval habitat preferences. Due to a lack of such information in Baringo County, Kenya, this study assessed species diversity and larval habitat preference of potential mosquito vectors of Rift Valley fever (RVF) and malaria. METHODS: Mosquito larvae were sampled from nine types of larval habitats and were identified morphologically. Species diversity was estimated by the Shannon's diversity index while larval habitat preference by RVF and malaria vectors was determined by ANOVA. RESULTS: A total of 7724 immature mosquitoes comprising 17 species belonging to four genera, namely Anopheles, Culex, Aedes and Mansonia, were identified. Among the 17 species, three Anopheles species are responsible for malaria transmission: An. gambiae (s.l.), An. funestus (s.l.) and An. pharoensis. Rift Valley fever vectors included Mansonia spp. and Culex spp. The highest Shannon's diversity index was observed during the cold dry season (H = 2.487) and in the highland zone (H = 2.539) while the lowest diversity was recorded during the long rain season (H = 2.354) and in the riverine zone (H = 2.085). Ditches had the highest mean number of Anopheles larvae (16.6 larvae per sample) followed by swamp (12.4) and seasonal riverbed (10.7). Water pit and water pan had low mean numbers of Anopheles larvae (1.4 and 1.8, respectively) but relatively high mean numbers of culicines (16.9 and 13.7, respectively). Concrete tank was the least sampled type of habitat but had highest mean number of culicine larvae (333.7 l) followed distantly by water spring (38.9) and swamp (23.5). Overall, larval habitats were significantly different in terms of larval density (F(8,334) = 2.090, P = 0.036). CONCLUSIONS: To our knowledge, the present study reports culicine larval species diversity in Baringo for the first time and the most preferred habitats were concrete tanks, water springs and swamps. Habitats preferred by Anopheles were mainly riverbed pools, ditches and swamps. Environmental management targeting the habitats most preferred by potential vectors can be part of integrated vector control in Baringo, especially during dry seasons.


Assuntos
Biodiversidade , Ecossistema , Mosquitos Vetores/classificação , Aedes/classificação , Aedes/parasitologia , Aedes/virologia , Animais , Anopheles/classificação , Anopheles/parasitologia , Anopheles/virologia , Culex/classificação , Culex/parasitologia , Culex/virologia , Quênia , Larva , Mosquitos Vetores/parasitologia , Mosquitos Vetores/virologia , Plasmodium , Vírus da Febre do Vale do Rift , Estações do Ano , Áreas Alagadas
5.
PLoS One ; 14(5): e0216360, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31048933

RESUMO

Sex-biased infections are a recurrent observation in vertebrates. In many species, males are more parasitized than females. Two potentially complementary mechanisms are often suggested to explain this pattern: sexual differences in susceptibility mainly caused by the effect of sex hormones on immunity and differential exposure to parasites. Exposure is mostly a consequence of host behavioural traits, but vector-borne parasitic infections involve another degree of complexity due to the active role of vectors in transmission. Blood-sucking insects may make choices based on cues produced by hosts. Regarding malaria, several studies highlighted a male-biased infection by Plasmodium sp in great tits (Parus major). We hypothesize that the mosquito vector, Culex pipiens, might at least partially cause this bias by being more attracted to male birds. Intrinsic variation associated to bird sex would explain a preference of mosquitoes for males. To test this hypothesis, we provide uninfected mosquitoes with a choice between uninfected male and female nestlings. Mosquito choice is assessed by sex typing of the ingested blood. We did not observe any preference for a given sex. This result does not support our prediction of a preference of mosquitoes for male great tits during the nestling period. In conclusion, mosquitoes do not seem to have an intrinsic preference for male nestlings. However, sexually divergent traits (e.g. behaviour, odour, metabolic rate) present in adults may play a role in the attraction of mosquitoes and should be investigated.


Assuntos
Doenças das Aves , Culex/parasitologia , Malária , Mosquitos Vetores/parasitologia , Passeriformes , Plasmodium/metabolismo , Caracteres Sexuais , Animais , Doenças das Aves/sangue , Doenças das Aves/parasitologia , Feminino , Malária/sangue , Malária/transmissão , Masculino , Comportamento de Nidação , Passeriformes/sangue , Passeriformes/parasitologia
6.
PLoS Negl Trop Dis ; 13(4): e0007229, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30943198

RESUMO

BACKGROUND: Culex species are widespread across Cameroon and responsible for high burden of nuisance in most urban settings. However, despite their high nuisance, they remain less studied compared to anophelines. The present study aimed to assess Culex species distribution, susceptibility to insecticide, bionomics and role in Lymphatic Filariasis (LF) transmission in the city of Yaoundé. METHODS: Mosquito collections were conducted from March to December 2017 using Centre for Disease Control light traps (CDC-LT), human landing catches (HLC) and larval collections. Mosquitoes were identified using morphological identification keys. Mosquitoes from the Culex pipiens complex were further identified using Polymerase Chain Reaction (PCR) to assess the presence of sibling species. Bioassays were conducted with 2-5 day-old unfed females to assess mosquito susceptibility to DDT, permethrin, deltamethrin and bendiocarb following WHO guidelines. Dead, control and surviving mosquitoes from bioassays were screened by PCR to detect the presence of knockdown resistance (kdr) alleles. Pools of mosquitoes were examined by PCR to detect the presence of Wuchereria bancrofti. RESULTS: A total of 197,956 mosquitoes belonging to thirteen species were collected. The density of mosquito collected varied according to the collection methods, districts and seasons. Culex quinquefasciatus emerged as the most abundant and the only species of the Culex pipiens complex in Yaoundé. Culex species were found breeding in different types of breeding sites including polluted and unpolluted sites. All Culex species including Cx antennatus, Cx duttoni, Cx perfuscus and Cx tigripes were found to be highly resistant to permethrin, deltamethrin and DDT. Culex quinquefasciatus was also found to be resistant to bendiocarb. A high frequency of the West Africa kdr allele was recorded in resistant Cx. quinquefasciatus. Out of the 247 pooled samples of 25 Culex spp. examined for the presence of Wuchereria bancrofti, none was found infected. CONCLUSION: The study confirms the high adaptation of Culex species particularly Culex quinquefasciatus to the urban environment and no implication of this species in the transmission of LF in Yaoundé Cameroon. Culex species predominance in urban settings highlight potential transmission risk of West Nile and rift valley fever in Yaoundé.


Assuntos
Culex/classificação , Culex/efeitos dos fármacos , Variação Genética , Resistência a Inseticidas , Inseticidas , Mosquitos Vetores/parasitologia , Animais , Camarões/epidemiologia , Culex/parasitologia , Filariose Linfática/epidemiologia , Feminino , Controle de Mosquitos , Nitrilos , Permetrina , Piretrinas , Wuchereria bancrofti/efeitos dos fármacos
7.
Transbound Emerg Dis ; 66(4): 1752-1757, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30874363

RESUMO

Mosquitoes are the main vectors of pathogens affecting wild animals, livestock and humans. Here, we used molecular tools to assess the local circulation of filarial parasites in mosquitoes collected during 2013 from natural, rural and urban habitats from southern Spain. We screened parasites in 22,791 female mosquitoes of the genera Aedes, Culex and Culiseta. Filarial worms were only detected in two mosquito pools. An Ae. caspius pool was positive for Setaria equina and an unidentified worm related to Onchocerca was detected in a Cx. pipiens pool. None of the mosquito pools were positive for Dirofilaria. These results underlay the role of Ae. caspius in the transmission of Setaria parasites among livestock and/or wildlife to humans in southern Spain.


Assuntos
Culicidae/parasitologia , Dirofilaria/isolamento & purificação , Mosquitos Vetores/parasitologia , Onchocerca/isolamento & purificação , Setaria (Nematoide)/isolamento & purificação , Aedes/parasitologia , Animais , Culex/parasitologia , Feminino , Espanha , Urbanização
8.
Malar J ; 18(1): 82, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30876412

RESUMO

BACKGROUND: Some Plasmodium species have the ability to modify the behaviour of their mosquito vectors. This is thought to be an adaptive strategy that maximizes the parasite's transmission. METHODS: The effect of Plasmodium relictum infections on the blood feeding behaviour of Culex pipiens quinquefasciatus mosquitoes was monitored. RESULTS: Plasmodium infections did not alter the proportion of blood fed mosquitoes but they did affect the dynamics and the size of the blood meal. Sporozoite-infected mosquitoes completed their blood meal 1.3 times later than uninfected mosquitoes and ended up with smaller blood meals. CONCLUSION: The potential adaptive nature of this manipulation of mosquito behaviour is discussed in the light of previous studies on other malaria models.


Assuntos
Culex/fisiologia , Culex/parasitologia , Comportamento Alimentar , Plasmodium/crescimento & desenvolvimento , Animais , Feminino , Tempo
9.
Parasit Vectors ; 12(1): 87, 2019 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-30867014

RESUMO

BACKGROUND: The transmission of mosquito-borne pathogens is strongly influenced by the contact rates between mosquitoes and susceptible hosts. The biting rates of mosquitoes depend on different factors including the mosquito species and host-related traits (i.e. odour, heat and behaviour). However, host characteristics potentially affecting intraspecific differences in the biting rate of mosquitoes are poorly known. Here, we assessed the impact of three host-related traits on the biting rate of two mosquito species with different feeding preferences: the ornithophilic Culex pipiens and the mammophilic Ochlerotatus (Aedes) caspius. Seventy-two jackdaws Corvus monedula and 101 house sparrows Passer domesticus were individually exposed to mosquito bites to test the effect of host sex, body mass and infection status by the avian malaria parasite Plasmodium on biting rates. RESULTS: Ochlerotatus caspius showed significantly higher biting rates than Cx. pipiens on jackdaws, but non-significant differences were found on house sparrows. In addition, more Oc. caspius fed on female than on male jackdaws, while no differences were found for Cx. pipiens. The biting rate of mosquitoes on house sparrows increased through the year. The bird infection status and body mass of both avian hosts were not related to the biting rate of both mosquito species. CONCLUSIONS: Host sex was the only host-related trait potentially affecting the biting rate of mosquitoes, although its effect may differ between mosquito and host species.


Assuntos
Doenças das Aves/transmissão , Culex/parasitologia , Malária/veterinária , Mosquitos Vetores/parasitologia , Ochlerotatus/parasitologia , Plasmodium/fisiologia , Animais , Comportamento Animal , Doenças das Aves/parasitologia , Corvos , Comportamento Alimentar , Feminino , Especificidade de Hospedeiro , Interações Hospedeiro-Parasita , Mordeduras e Picadas de Insetos/veterinária , Malária/parasitologia , Malária/transmissão , Masculino , Fenótipo , Fatores Sexuais , Pardais
10.
Parasitol Res ; 118(4): 1261-1269, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30783859

RESUMO

Avian malaria (Plasmodium spp.) and kinetoplastid (Trypanosoma spp.) parasites are common vector-borne pathogens in birds worldwide; however, knowledge about vector competence of different mosquito species is currently lacking. For a pilot project examining vector competence of mosquitoes of the Culex pipiens complex and Culex torrentium for protozoan parasites in the city of Vienna, 316 individual mosquitoes were sampled in the months June-August 2017 around the campus of the Veterinary University of Vienna. Since vector competence for avian Plasmodium can only be ascertained by finding infectious sporozoites in mosquito salivary glands, special emphasis was on examining these, or at least insect thoraxes, which contain the salivary glands. After species identification, the mosquitoes were processed in three different ways to determine the best method of visually detecting protozoan parasites in salivary glands: (1) microscopic examination of individual, fixed and Giemsa-stained salivary glands, (2) microscopic examination of stained sections of individually fixed and embedded mosquito thoraxes and (3) stained sections of individual whole insects. Material from all three groups was also subjected to PCR to detect avian haemosporidian and trypanosomatid parasite DNA. PCR was performed on all 316 collected mosquitoes, with 37 pools (n = 2-10) of 263 individuals and 53 single individuals in all together 90 PCR reactions. Avian Plasmodium was found in 18 (20%) and trypanosomatid parasites were found in 10 (11.1%) of the examined samples and pools yielded a higher proportion of positives than did individual samples. Six different species of protozoan parasites were identified, namely Plasmodium vaughani SYAT05 which was the most common, P. elongatum GRW6, P. relictum SGS1, Trypanosoma avium, T. culicavium and Crithidia dedva. Seventy-seven mosquito salivary glands were dissected and stained with Giemsa solution. Of these, one (1.3%) featured sporozoites and one (1.3%) trypanosomatid parasites. While the trypanosomes were identified as T. avium, the avian Plasmodium species were present in a mixed infection with P. vaughani SYAT05 as the dominant species. In conclusion, mosquitoes of the Culex pipiens complex are very likely vectors of different avian Plasmodium and Trypanosoma species and PCR was the most successful and reliable method for parasite detection in mosquito samples, delivering higher rates and more accurate results. The visual detection of parasite stages in the salivary glands was more difficult and only a few specimens were detected using Giemsa stain and chromogenic in situ hybridization. For further studies on vector competence of different protozoan parasites in mosquitoes, the use of PCR-based methods would be preferable.


Assuntos
Culex/parasitologia , Malária Aviária/transmissão , Mosquitos Vetores/parasitologia , Plasmodium/isolamento & purificação , Glândulas Salivares/parasitologia , Esporozoítos/isolamento & purificação , Trypanosoma/isolamento & purificação , Animais , Aves/parasitologia , DNA de Protozoário/análise , Malária Aviária/parasitologia , Projetos Piloto , Plasmodium/classificação , Plasmodium/genética , Reação em Cadeia da Polimerase , Trypanosoma/classificação , Trypanosoma/genética
11.
Parasite ; 26: 2, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30644356

RESUMO

Dirofilariasis is endemic in Russia, as well as in many other European countries. The aim of this study was to assess the ability of mosquitoes to transfer Dirofilaria immitis and Dirofilaria repens in regions with temperate and subtropical climates. The possible impact of the symbiotic bacterium Wolbachia on Dirofilaria transmission was also investigated. 5333 female mosquitoes were collected at 11 points in central European Russia and on the Black Sea coast during the period 2013-2017. Out of 20 mosquito species examined, 14 were infected with D. repens and 13 with D. immitis. Both species of Dirofilaria were found in different climatic regions. The total Dirofilaria spp. estimated infection rate (EIR) in the central part of Russia varied from 3.1% to 3.7% and, in the southern region, from 1.1% to 3.0%. The highest estimated infection rate was found in Anopheles messeae, the lowest in Culex pipiens. The greatest epidemiological danger was represented by Aedes aegypti, Ae. geniculatus, An. messeae and Ae. communis. Six out of 20 mosquito species were infected with Wolbachia. Pools of Aedes albopictus, Cx. pipiens and Coquillettidia richiardii were simultaneously infected with Dirofilaria and Wolbachia. After checking mosquitoes individually, it was found that there was no development of Dirofilaria to the infective larval stage in specimens infected with Wolbachia. Twenty-two Dirofilaria-infective pools were Wolbachia-free and only two mosquito pools were Wolbachia-infected. The potential for transmission of Dirofilaria in mosquito species naturally uninfected with the symbiotic bacterium Wolbachia is higher than in species infected with the bacterium.


Assuntos
Culicidae/microbiologia , Culicidae/parasitologia , Dirofilariose/epidemiologia , Dirofilariose/transmissão , Wolbachia/isolamento & purificação , Animais , Mar Negro , Culex/microbiologia , Culex/parasitologia , DNA de Helmintos/isolamento & purificação , Dirofilaria immitis/genética , Dirofilaria immitis/isolamento & purificação , Dirofilaria immitis/fisiologia , Dirofilaria repens/isolamento & purificação , Dirofilaria repens/fisiologia , Doenças do Cão/epidemiologia , Cães , Feminino , Larva/microbiologia , Larva/parasitologia , Mosquitos Vetores/microbiologia , Mosquitos Vetores/parasitologia , Federação Russa/epidemiologia , Simbiose , Wolbachia/genética , Wolbachia/fisiologia
12.
Nat Microbiol ; 4(1): 20-34, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30150735

RESUMO

Human pathogens that are transmitted by insects are a global problem, particularly those vectored by mosquitoes; for example, malaria parasites transmitted by Anopheles species, and viruses such as dengue, Zika and chikungunya that are carried by Aedes mosquitoes. Over the past 15 years, the prevalence of malaria has been substantially reduced and virus outbreaks have been contained by controlling mosquito vectors using insecticide-based approaches. However, disease control is now threatened by alarming rates of insecticide resistance in insect populations, prompting the need to develop a new generation of specific strategies that can reduce vector-mediated transmission. Here, we review how increased knowledge in insect biology and insect-pathogen interactions is stimulating new concepts and tools for vector control. We focus on strategies that either interfere with the development of pathogens within their vectors or directly impact insect survival, including enhancement of vector-mediated immune control, manipulation of the insect microbiome, or use of powerful new genetic tools such as CRISPR-Cas systems to edit vector genomes. Finally, we offer a perspective on the implementation hurdles as well as the knowledge gaps that must be filled in the coming years to safely realize the potential of these novel strategies to eliminate the scourge of vector-borne disease.


Assuntos
Controle de Doenças Transmissíveis/métodos , Doenças Transmissíveis/transmissão , Surtos de Doenças/prevenção & controle , Controle de Insetos/métodos , Mosquitos Vetores/microbiologia , Mosquitos Vetores/parasitologia , Aedes/virologia , Animais , Anopheles/microbiologia , Anopheles/parasitologia , Agentes de Controle Biológico/farmacologia , Culex/parasitologia , Culex/virologia , Humanos , Resistência a Inseticidas , Inseticidas/farmacologia , Wolbachia/patogenicidade
13.
Exp Parasitol ; 197: 76-84, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30414843

RESUMO

The prevalence of mosquito vector borne diseases and the resistance of mosquitoes to conventional pesticides have been of important public concern to the mosquito endemic countries. Present study was conducted to identify the native bio-larvicidal potential of the entomopathogenic nematodes; Steinernema siamkayai (KPR-4) Heterohabditis indica (KPR-8), Steinernema glaseri and Steinernema abbasi. The isolated nematodes were subsequently cultured and evaluated their larvicidal potential against the larvae of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. Among the tested four different nematode species, the S. abassi exerted the highest mortality against A. aegypti (97.33%), the H. indica (KPR-8) against A. stephensi (97.33%) and the S. siamkayai (KPR-4) against C. quinquefasciatus (98.67%). The maximal mosquito-larvicidal property of EPNs was found with the LC50 and LC90 values (IJs/larvae): S. abbasi = 12.47 & 54.35 on A. aegypti; H. indica KPR-8 = 19.88 & 66.81 on A. stephensi and S. siamkayai KPR-4 = 16.69 & 58.97 on C. quinquefasciatus, respectively. The presently generated data on the molecular and larvicidal characteristics of the entomopathogenic nematodes form an important baseline data that upon further research would lead to the development of eco-friendly mosquito-control agent.


Assuntos
Culicidae/parasitologia , Mosquitos Vetores/parasitologia , Rabditídios/fisiologia , Aedes/crescimento & desenvolvimento , Aedes/parasitologia , Análise de Variância , Animais , Anopheles/crescimento & desenvolvimento , Anopheles/parasitologia , Sequência de Bases , Culex/crescimento & desenvolvimento , Culex/parasitologia , Culicidae/crescimento & desenvolvimento , DNA de Helmintos/química , DNA Ribossômico/química , Índia , Larva , Controle de Mosquitos/economia , Controle de Mosquitos/métodos , Mosquitos Vetores/crescimento & desenvolvimento , Controle Biológico de Vetores , Filogenia , Rabditídios/classificação , Rabditídios/genética , Rabditídios/isolamento & purificação , Solo/parasitologia , Strongyloidea/classificação , Strongyloidea/genética , Strongyloidea/isolamento & purificação , Strongyloidea/fisiologia
14.
Parasitol Res ; 118(1): 127-138, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30535561

RESUMO

In recent years, numerous studies screening mosquitoes for filarioid helminths (xenomonitoring) have been performed in Europe. The entomological monitoring of filarial nematode infections in mosquitoes by molecular xenomonitoring might serve as the measure of the rate at which humans and animals expose mosquitoes to microfilariae and the rate at which animals and humans are exposed to the bites of the infected mosquitoes. We hypothesized that combining the data obtained from molecular xenomonitoring and phenological studies of mosquitoes in the urban environment would provide insights into the transmission risk of filarial diseases. In our search for Dirofilaria spp.-infected mosquitoes, we have found Setaria tundra-infected ones instead, as in many other European studies. We have observed that cross-reactivity in PCR assays for Dirofilaria repens, Dirofilaria immitis, and S. tundra COI gene detection was the rule rather than the exception. S. tundra infections were mainly found in Aedes mosquitoes. The differences in the diurnal rhythm of Aedes and Culex mosquitoes did not seem a likely explanation for the lack of S. tundra infections in Culex mosquitoes. The similarity of S. tundra COI gene sequences found in Aedes vexans and Aedes caspius mosquitoes and in roe deer in many European studies, supported by data on Ae. vexans biology, suggested host preference as the most likely cause of the mosquito genus-biased infections. High diversity of the COI gene sequences isolated in the city of Wroclaw in south western Poland and the presence of identical or almost identical sequences in mosquitoes and roe deer across Europe suggests that S. tundra has been established in most of Europe for a very long time.


Assuntos
Aedes/parasitologia , Culex/parasitologia , Dirofilaria immitis/isolamento & purificação , Dirofilaria repens/isolamento & purificação , Dirofilariose/transmissão , Mosquitos Vetores/parasitologia , Setaria (Nematoide)/isolamento & purificação , Setaríase/transmissão , Aedes/fisiologia , Animais , Culex/fisiologia , Dirofilaria immitis/genética , Dirofilaria repens/genética , Dirofilariose/epidemiologia , Dirofilariose/parasitologia , Humanos , Mosquitos Vetores/fisiologia , Polônia/epidemiologia , Setaria (Nematoide)/genética , Setaríase/epidemiologia , Setaríase/parasitologia
15.
PLoS Negl Trop Dis ; 12(11): e0006962, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30462640

RESUMO

BACKGROUND: Currently, molecular xenomonitoring efforts for lymphatic filariasis rely on PCR or real-time PCR-based detection of Brugia malayi, Brugia timori and Wuchereria bancrofti in mosquito vectors. Most commonly, extraction of DNA from mosquitoes is performed using silica column-based technologies. However, such extractions are both time consuming and costly, and the diagnostic testing which follows typically requires expensive thermal cyclers or real-time PCR instruments. These expenses present significant challenges for laboratories in many endemic areas. Accordingly, in such locations, there exists a need for inexpensive, equipment-minimizing diagnostic options that can be transported to the field and implemented in minimal resource settings. Here we present a novel diagnostic approach for molecular xenomonitoring of filarial parasites in mosquitoes that uses a rapid, NaOH-based DNA extraction methodology coupled with a portable, battery powered PCR platform and a test strip-based DNA detection assay. While the research reported here serves as a proof-of-concept for the backpack PCR methodology for the detection of filarial parasites in mosquitoes, the platform should be easily adaptable to the detection of W. bancrofti and other mosquito-transmitted pathogens. METHODOLOGY/PRINCIPAL FINDINGS: Through comparisons with standard silica column-based DNA extraction techniques, we evaluated the performance of a rapid, NaOH-based methodology for the extraction of total DNA from pools of parasite-spiked vector mosquitoes. We also compared our novel test strip-based detection assay to real-time PCR and conventional PCR coupled with gel electrophoresis, and demonstrated that this method provides sensitive and genus-specific detection of parasite DNA from extracted mosquito pools. Finally, by comparing laboratory-based thermal cycling with a field-friendly miniaturized PCR approach, we have demonstrated the potential for the point-of-collection-based use of this entire diagnostic platform that is compact enough to fit into a small backpack. CONCLUSIONS/SIGNIFICANCE: Because this point-of-collection diagnostic platform eliminates reliance on expensive and bulky instrumentation without compromising sensitivity or specificity of detection, it provides an alternative to cost-prohibitive column-dependent DNA extractions that are typically coupled to detection methodologies requiring advanced laboratory infrastructure. In doing so, this field-ready system should increase the feasibility of molecular xenomonitoring within B. malayi-endemic locations. Of greater importance, this backpack PCR system also provides the proof-of-concept framework for the development of a parallel assay for the detection of W. bancrofti.


Assuntos
Aedes/parasitologia , Brugia/isolamento & purificação , Culex/parasitologia , Mosquitos Vetores/parasitologia , Reação em Cadeia da Polimerase em Tempo Real/métodos , Animais , Brugia/classificação , Brugia/genética , DNA de Helmintos/genética , Filariose Linfática/parasitologia , Filariose Linfática/transmissão , Humanos , Reação em Cadeia da Polimerase em Tempo Real/instrumentação , Sensibilidade e Especificidade , Wuchereria bancrofti/genética , Wuchereria bancrofti/isolamento & purificação
16.
Parasit Vectors ; 11(1): 588, 2018 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-30424781

RESUMO

BACKGROUND: Control of lymphatic filariasis (LF) in most of the sub-Saharan African countries is based on annual mass drug administration (MDA) using a combination of ivermectin and albendazole. Monitoring the impact of this intervention is crucial for measuring the success of the LF elimination programmes. This study assessed the status of LF infection in Rufiji district, southeastern Tanzania after twelve rounds of MDA. METHODS: Community members aged between 10 and 79 years were examined for Wuchereria bancrofti circulating filarial antigens (CFA) using immunochromatographic test cards (ICTs) and antigen-positive individuals were screened for microfilaraemia. All study participants were examined for clinical manifestation of LF and interviewed for drug uptake during MDA rounds. Filarial mosquito vectors were collected indoor and outdoor and examined for infection with W. bancrofti using a microscope and quantitative real-time polymerase chain reaction (qPCR) techniques. RESULTS: Out of 854 participants tested, nine (1.1%) were positive for CFA and one (0.1%) was found to be microfilaraemic. The prevalence of hydrocele and elephantiasis was 4.8% and 2.9%, respectively. Surveyed drug uptake rates were high, with 70.5% of the respondents reporting having swallowed the drugs in the 2014 MDA round (about seven months before this study). Further, 82.7% of the respondents reported having swallowed the drugs at least once since the inception of MDA programme in 2000. Of the 1054 filarial vectors caught indoors and dissected to detect W. bancrofti infection none was found to be infected. Moreover, analysis by qPCR of 1092 pools of gravid Culex quinquefasciatus collected outdoors resulted in an estimated infection rate of 0.1%. None of the filarial vectors tested with qPCR were found to be infective. CONCLUSION: Analysis of indices of LF infection in the human population and filarial mosquito vectors indicated a substantial decline in the prevalence of LF and other transmission indices, suggesting that local transmission was extremely low if occurring at all in the study areas. We, therefore, recommend a formal transmission assessment survey (TAS) to be conducted in the study areas to make an informed decision on whether Rufiji District satisfied WHO criteria for stopping MDA.


Assuntos
Culex/parasitologia , Filariose Linfática/epidemiologia , Filariose Linfática/transmissão , Administração Massiva de Medicamentos/estatística & dados numéricos , Mosquitos Vetores/parasitologia , Wuchereria bancrofti/isolamento & purificação , Adolescente , Adulto , Idoso , Albendazol/administração & dosagem , Albendazol/efeitos adversos , Animais , Antiprotozoários/administração & dosagem , Antiprotozoários/efeitos adversos , Criança , Filariose Linfática/parasitologia , Filariose Linfática/prevenção & controle , Feminino , Filaricidas/administração & dosagem , Humanos , Ivermectina/administração & dosagem , Ivermectina/efeitos adversos , Masculino , Administração Massiva de Medicamentos/efeitos adversos , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase em Tempo Real , Tanzânia/epidemiologia , Wuchereria bancrofti/genética , Adulto Jovem
17.
Parasitol Res ; 117(11): 3679-3681, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30280219

RESUMO

In recent years, the number of reported cases of human dirofilariasis in Europe has increased and the circulation of Dirofilaria spp. in mosquitoes in several European countries has been proven. We report here two likely autochthonous cases of subcutaneous human dirofilariasis from Barcelona, Spain, caused by Dirofilaria repens. The potential for an increase in human infection is high given the number of cases published recently and the ability of vectors to spread through the Mediterranean basin.


Assuntos
Dirofilaria repens/isolamento & purificação , Dirofilariose , Adulto , Aedes/parasitologia , Animais , Antiparasitários/uso terapêutico , Culex/parasitologia , Dirofilariose/diagnóstico , Dirofilariose/tratamento farmacológico , Dirofilariose/transmissão , Transmissão de Doença Infecciosa , Europa (Continente) , Feminino , Humanos , Ivermectina/uso terapêutico , Mosquitos Vetores/parasitologia , Espanha
18.
PLoS One ; 13(10): e0205358, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30296287

RESUMO

BG-Malaria (BGM) trap is a simple adaptation of the widely-used BG-Sentinel trap (BGS). It is proven to be highly effective for trapping the Brazilian malaria vector, Anopheles darlingi, in field conditions, and the African vector, Anopheles arabiensis, under controlled semi-field environments, but has not been field-tested in Africa. Here, we validated the BGM for field sampling of malaria vectors in south-eastern Tanzania. Using a series of Latin-Square experiments conducted nightly (6pm-7am) in rural villages, we compared mosquito catches between BGM, BGS and human landing catches (HLC). We also compared BGMs baited with different attractants (Ifakara-blend, Mbita-blend, BG-Lure and CO2). Lastly, we tested BGMs baited with Ifakara-blend from three odour-dispensing methods (BG-Cartridge, BG-Sachet and Nylon strips). One-tenth of the field-collected female Anopheles gambiae s.l. and Anopheles funestus were dissected to assess parity. BGM captured more An. gambiae s.l. than BGS (p < 0.001), but HLC caught more than either trap (p < 0.001). However, BGM captured more An. funestus than HLC. Proportions of parous An. gambiae s.l. and An. funestus consistently exceeded 50%, with no significant difference between methods. While the dominant species caught by HLC was An. gambiae s.l. (56.0%), followed by Culex spp. (33.1%) and Mansonia spp. (6.0%), the BGM caught mostly Culex (81.6%), followed by An. gambiae s.l. (10.6%) and Mansonia (5.8%). The attractant-baited BGMs were all significantly superior to un-baited controls (p < 0.001), although no difference was found between the specific attractants. The BG-Sachet was the most efficient dispenser for capturing An. gambiae s.l. (14.5(2.75-42.50) mosquitoes/trap/night), followed by BG-Cartridge (7.5(1.75-26.25)). The BGM caught more mosquitoes than BGS in field-settings, but sampled similar species diversity and physiological states as BGS. The physiological states of malaria vectors caught in BGM and BGS were similar to those naturally attempting to bite humans (HLC). The BGM was most efficient when baited with Ifakara blend, dispensed from BG-Sachet. We conclude that though BGM traps have potential for field-sampling of host-seeking African malaria vectors with representative physiological states, both BGM and BGS predominantly caught more culicines than Anopheles, compared to HLC, which caught mostly An. gambiae s.l.


Assuntos
Anopheles/parasitologia , Malária/parasitologia , Malária/transmissão , Controle de Mosquitos , Animais , Anopheles/genética , Anopheles/patogenicidade , Brasil , Culex/parasitologia , Vetores de Doenças , Meio Ambiente , Humanos , Malária/epidemiologia , Malária/genética , Mosquitos Vetores/genética , Mosquitos Vetores/parasitologia , Tanzânia/epidemiologia
19.
Parasit Vectors ; 11(1): 541, 2018 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-30314510

RESUMO

BACKGROUND: Functional analysis of animal parasitic nematode genes is often quite challenging due to the unavailability of standardised in vitro culture conditions and lack of adequate tools to manipulate these genes. Therefore, this study was undertaken to investigate the suitability of Culex quinquefasciatus, as an in vivo culture platform for Setaria digitata larvae and RNA interference (RNAi), as a post-transcriptional gene silencing tool to study the roles of a vital gene that encodes a novel parasitic nematode-specific protein (SDNP). RESULTS: The red colour fluorescence detected following RNAi injection to the thorax of C. quinquefasciatus indicated the uptake of dsRNA by S. digitata larvae. The reduction of SDNP transcripts in siRNA treated larvae compared to non-treated larvae, as determined by qPCR, indicated that the siRNA pathway is operational in S. digitata larvae. The observation of motility reductions and deformities during the development indicated the association of SDNP in larvae locomotion and development processes, respectively. The irregularities in the migration of larvae in mosquitoes and elevated survival rates of mosquitoes compared to their untreated counterparts indicated reduced parasitism of S. digitata larvae in mosquitoes upon targeted downregulation of SDNP by siRNA treatment. CONCLUSION: SDNP plays vital roles in muscle contraction, locomotion, development processes, larval development and parasitism of S. digitata. Its ubiquitous presence in parasitic nematodes and its absence in their hosts provide a tantalising prospect of the possibility of targeting SDNP for future development of anthelmintic drugs. The susceptibility of the larval stages of S. digitata for RNAi in Culex quinquefasciatus was also demonstrated for the first time in this study.


Assuntos
Culex/parasitologia , Proteínas de Helminto/genética , Larva/genética , Interferência de RNA , RNA Interferente Pequeno , Setaria (Nematoide)/genética , Animais , Técnicas de Silenciamento de Genes , Proteínas de Helminto/isolamento & purificação , Proteínas de Helminto/metabolismo , Larva/fisiologia , Setaria (Nematoide)/fisiologia
20.
J Vector Borne Dis ; 55(2): 151-158, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30280714

RESUMO

Background & objectives: Dirofilaria immitis is a filarial nematode that causes heartworm disease in domestic as well as wild canines and felines; and cutaneous or pulmonary infections in humans. The purpose of the study was to estimate the prevalence of D. immitis in domestic dogs in Tabasco, Mexico and to assay mosquitoes temporally and spatially associated with dogs for evidence of infection. Methods: Blood was collected from 1050 dogs in 1039 houses during a random household survey performed in 2016 and 2017. Genomic DNA was extracted and assayed by polymerase chain reaction (PCR) using pan-filarial primers and various species-specific primers. Dog owners were interviewed using a structured questionnaire designed to collect information on factors that may impact the occurrence of filarial infection. The association between canine dirofilariasis prevalence and factors likely to impact infection was determined by univariate logistic regression analysis, followed by multivariate binomial logistic regression analysis. Indoor and outdoor resting mosquitoes were collected from houses by manual aspiration. Mosquitoes were identified according to species, homogenized and tested by PCR for filarial nematodes. Results: A total of 84 (8%) dogs were positive for D. immitis DNA, while 3 (0.3%) dogs contained Acanthocheilonema reconditum DNA. Several factors were significantly associated with D. immitis infection. For example, dogs that lived <100 m from a large source of open standing water were significantly more likely (p = 0.002) to become infected with D. immitis than other dogs. Additionally, dogs with infrequent or no anthelmintic treatment were significantly more likely (p = 0.0) to become infected than dogs that were regularly treated. The entomologic investigation yielded 2618 female mosquitoes from 14 species. Four pools of Culex quinquefasciatus were positive for D. immitis DNA and the minimum infection rate, calculated as the number of positive pools per 1000 mosquitoes tested, was 2.9. Interpretation & conclusion: The study identified several factors positively associated with an increased risk of D. immitis infection in domestic dogs in Tabasco and provides evidence that Cx. quinquefasciatus is potentially an important vector in this region. This information can be used by local veterinarians and dog owners to reduce the burden of D. immitis on canine health.


Assuntos
Aedes/parasitologia , Culex/parasitologia , Dirofilaria immitis/isolamento & purificação , Dirofilariose/parasitologia , Doenças do Cão/parasitologia , Mosquitos Vetores/parasitologia , Animais , Primers do DNA/genética , DNA de Helmintos/genética , Dirofilaria immitis/classificação , Dirofilaria immitis/genética , Cães , Feminino , México , Reação em Cadeia da Polimerase
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