scholarly journals A novel assay to isolate and quantify third-stage filarial larvae emerging from individual mosquitoes

2020 ◽  
Author(s):  
Abigail R. McCrea ◽  
Elizabeth B. Edgerton ◽  
Genevieve T. Oliver ◽  
Fiona M. O’Neill ◽  
Thomas J. Nolan ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Post Infection ◽  
Blood Feeding ◽  
Economic Consequences ◽  
Transmission Potential ◽  
Filarial Nematodes ◽  
Third Stage ◽  
Novel Method ◽  
Parasite Emergence ◽  
New Strategies

AbstractBackgroundMosquitoes transmit filarial nematodes to both human and animal hosts, resulting in worldwide health and economic consequences. Transmission to a vertebrate host requires that ingested microfilariae develop into infective third-stage larvae capable of emerging from the mosquito proboscis onto the skin of the host during blood feeding. Determining the number of microfilariae that successfully develop to infective third-stage larvae in the mosquito host is key to understanding parasite transmission potential and to developing new strategies to block these worms in their vector.MethodsWe developed a novel method to efficiently assess the number of infective third-stage filarial larvae that emerge from experimentally infected mosquitoes. Following infection, individual mosquitoes were placed in wells of a multi-well culture plate and warmed to 37 °C to stimulate parasite emergence. Aedes aegypti infected with Dirofilaria immitis were used to determine infection conditions and assay timing. The assay was also tested with Brugia malayi infected Ae. aegypti.ResultsApproximately 30% of Ae. aegypti infected with D. immitis and 50% of those infected with B. malayi produce emerging third-stage larvae. Once D. immitis third-stage larvae emerge at 13 days post infection, the proportion of mosquitoes producing them, and the number produced per mosquito remain stable until at least day 21. The prevalence and intensity of emerging third-stage B. malayi were similar on days 12-14 days post infection. Increased uptake of D. immitis microfilariae increases the fitness cost to the mosquito but does not increase the number of emerging third-stage larvae.ConclusionsWe provide a new assay with an associated set of infection conditions that will facilitate assessment of the filarial transmission potential of mosquito vectors and promote preparation of uniformly infectious L3 for functional assays. The ability to quantify infection outcome will facilitate analyses of molecular interactions between vectors and filariae, ultimately allowing for the establishment of novel methods to block disease transmission.Graphical Abstract

scholarly journals A novel assay to isolate and quantify third-stage Dirofilaria immitis and Brugia malayi larvae emerging from individual Aedes aegypti

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Abigail R. McCrea ◽  
Elizabeth B. Edgerton ◽  
Genevieve T. Oliver ◽  
Fiona M. O’Neill ◽  
Thomas J. Nolan ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Disease Transmission ◽  
Post Infection ◽  
Dirofilaria Immitis ◽  
Brugia Malayi ◽  
Blood Feeding ◽  
Economic Consequences ◽  
Transmission Potential ◽  
Filarial Nematodes ◽  
Third Stage

Abstract Background Mosquitoes transmit filarial nematodes to both human and animal hosts, with worldwide health and economic consequences. Transmission to a vertebrate host requires that ingested microfilariae develop into infective third-stage larvae capable of emerging from the mosquito proboscis onto the skin of the host during blood-feeding. Determining the number of microfilariae that successfully develop to infective third-stage larvae in the mosquito host is key to understanding parasite transmission potential and to developing new strategies to block these worms in their vector. Methods We developed a novel method to efficiently assess the number of infective third-stage filarial larvae that emerge from experimentally infected mosquitoes. Following infection, individual mosquitoes were placed in wells of a multi-well culture plate and warmed to 37 °C to stimulate parasite emergence. Aedes aegypti infected with Dirofilaria immitis were used to determine infection conditions and assay timing. The assay was also tested with Brugia malayi-infected Ae. aegypti. Results Approximately 30% of Ae. aegypti infected with D. immitis and 50% of those infected with B. malayi produced emerging third-stage larvae. Once D. immitis third-stage larvae emerged at 13 days post infection, the proportion of mosquitoes producing them and the number produced per mosquito remained stable until at least day 21. The prevalence and intensity of emerging third-stage B. malayi were similar on days 12–14 post infection. Increased uptake of D. immitis microfilariae increased the fitness cost to the mosquito but did not increase the number of emerging third-stage larvae. Conclusions We provide a new assay with an associated set of infection conditions that will facilitate assessment of the filarial transmission potential of mosquito vectors and promote preparation of uniformly infectious third-stage larvae for functional assays. The ability to quantify infection outcome will facilitate analyses of molecular interactions between vectors and filariae, ultimately allowing for the establishment of novel methods to block disease transmission.

scholarly journals Assessing the blood-host plasticity and dispersal rate of the malaria vector Anopheles coluzzii

2018 ◽  
Author(s):  
James Orsborne ◽  
Luis Furuya-Kanamori ◽  
Claire L. Jeffries ◽  
Mojca Kristan ◽  
Abdul Rahim Mohammed ◽  
...  
Keyword(s):  
Blood Meal ◽  
Disease Transmission ◽  
Blood Feeding ◽  
Host Choice ◽  
Anopheles Coluzzii ◽  
Dispersal Rate ◽  
Blood Digestion ◽  
Novel Method ◽  
Blood Meal Digestion ◽  
Blood Meals

AbstractDifficulties with observing the dispersal of insect vectors in the field have hampered understanding of several aspects of their behaviour linked to disease transmission. Here, a novel method based on detection of blood-meal sources is introduced to inform two critical and understudied mosquito behaviours: plasticity in the malaria vector’s blood-host choice and vector dispersal. Strategically located collections of Anopheles coluzzii from a malaria-endemic village of southern Ghana showed statistically significant variation in host species composition of mosquito blood-meals. Trialling a new sampling approach gave the first estimates for the remarkably local spatial scale across which host choice is plastic. Using quantitative PCR, the blood-meal digestion was then quantified for field-caught mosquitoes and calibrated according to timed blood digestion in colony mosquitoes. We demonstrate how this new ‘molecular Sella score’ approach can be used to estimate the dispersal rate of blood-feeding vectors caught in the field.

scholarly journals Livestock movement informs the risk of disease spread in traditional production systems in East Africa

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Divine Ekwem ◽  
Thomas A. Morrison ◽  
Richard Reeve ◽  
Jessica Enright ◽  
Joram Buza ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Production Systems ◽  
Control Strategies ◽  
Herd Size ◽  
Transmission Risk ◽  
Disease Spread ◽  
Transmission Potential ◽  
Spatial And Temporal Scales ◽  
Transmission Distance ◽  
Risk Of Disease

AbstractIn Africa, livestock are important to local and national economies, but their productivity is constrained by infectious diseases. Comprehensive information on livestock movements and contacts is required to devise appropriate disease control strategies; yet, understanding contact risk in systems where herds mix extensively, and where different pathogens can be transmitted at different spatial and temporal scales, remains a major challenge. We deployed Global Positioning System collars on cattle in 52 herds in a traditional agropastoral system in western Serengeti, Tanzania, to understand fine-scale movements and between-herd contacts, and to identify locations of greatest interaction between herds. We examined contact across spatiotemporal scales relevant to different disease transmission scenarios. Daily cattle movements increased with herd size and rainfall. Generally, contact between herds was greatest away from households, during periods with low rainfall and in locations close to dipping points. We demonstrate how movements and contacts affect the risk of disease spread. For example, transmission risk is relatively sensitive to the survival time of different pathogens in the environment, and less sensitive to transmission distance, at least over the range of the spatiotemporal definitions of contacts that we explored. We identify times and locations of greatest disease transmission potential and that could be targeted through tailored control strategies.

scholarly journals Livestock Movement Informs the Risk of Disease Spread in Traditional Production Systems in East Africa

2021 ◽  
Author(s):  
Divine Ekwem ◽  
Thomas A. Morrison ◽  
Richard Reeve ◽  
Jessica Enright ◽  
Joram Buza ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Production Systems ◽  
Control Strategies ◽  
Herd Size ◽  
Disease Spread ◽  
Transmission Potential ◽  
Spatial And Temporal Scales ◽  
Transmission Distance ◽  
Cattle Movements ◽  
Risk Of Disease

Abstract In Africa, livestock are important to local and national economies, but their productivity is constrained by infectious diseases. Comprehensive information on livestock movements and contacts is required to devise appropriate disease control strategies; yet, understanding contact risk in systems where herds mix extensively, and where different pathogens can be transmitted at different spatial and temporal scales, remains a major challenge. We deployed Global Positioning System collars on cattle in 52 herds in a traditional agropastoral system in western Serengeti, Tanzania, to understand fine-scale movements and between-herd contacts, and to identify locations of greatest interaction between herds. We examined contact across spatiotemporal scales relevant to different disease transmission scenarios. Daily cattle movements increased with herd size and rainfall. Generally, contact was greatest away from households, during periods with low rainfall and in locations close to dipping points. We demonstrate how movements and contacts affect the risk of disease spread. For example, contact rate was relatively sensitive to the survival time of different pathogens in the environment, and less sensitive to transmission distance, at least over the range of values that we explored. We identify times and locations of greatest disease transmission potential and that could be targeted through tailored control strategies.

scholarly journals Infection of highly insecticide-resistant malaria vector Anopheles coluzzii with entomopathogenic bacteria Chromobacterium violaceum reduces its survival, blood feeding propensity and fecundity

2020 ◽  
Author(s):  
Edounou Jacques Gnambani ◽  
Etienne Bilgo ◽  
Adama Sanou ◽  
Roch K. Dabire ◽  
Abdoulaye Diabate
Keyword(s):  
Burkina Faso ◽  
Post Infection ◽  
Blood Feeding ◽  
Egg Laying ◽  
Chromobacterium Violaceum ◽  
Hatching Rate ◽  
Anopheles Coluzzii ◽  
Potential Candidate ◽  
Mosquito Survival ◽  
The Impact

Abstract Background This is now a concern that malaria eradication will not be achieved without the introduction of novel control tools. Microbiological control might be able to make a greater contribution to vector control in the future. The interactions between bacteria and mosquito make mosquito microbiota really promising from a disease control perspective. Here, we studied the impact of Chromobacterium violaceum infections isolated from both larvae and adult of wild caught Anopheles gambiae s.l. mosquitoes in Burkina Faso on mosquito survival, blood feeding and fecundity propensy. Methods To assess entomopathogenic effects of C. violaceum infection on mosquitoes, three different types of bioassays were performed in laboratory. These bioassays aimed to evaluate the impact of C.violaceum infection on mosquito survival, blood feeding and fecundity, respectively. During bioassays mosquitoes were infected through the well-established system of cotton ball soaked with 6% glucose containing C.violaceum . Results C. violaceum kills pyrethroid resistant mosquitoes An. coluzzii (LT80 of 8.78 days ± 0.18 at 10 8 bacteria cell/ml of sugar meal). Interestingly, this bacterium had other negative effects on mosquito lifespan by significantly reducing (~59%, P<0.001) the mosquito feeding willingness from day 4-post infection (~81% would seek a host to blood feed) to 9- day post infection (22 ± 4.62% would seek a host to blood feed). Moreover, C. violaceum considerably jeopardized the egg laying (~16 eggs laid /mosquitoes with C. violaceum infected mosquitoes vs ~129 eggs laid / mosquitoes with control mosquitoes) and hatching of mosquitoes (A reduction of ~22 % of hatching rate with C. violaceum infected mosquitoes). Compared to the bacterial uninfected mosquitoes, mosquitoes infected with C. violaceum showed indeed significantly higher retention rates of immature eggs and follicles. Conclusion These data showed important properties of Burkina Faso C. violaceum strains , which are highly virulent against insecticide resistant Anopheles coluzzii , and reduce both mosquito blood feeding and fecundity propensities. However, additional studies as the sequencing of C. violaceum genome and the potential toxins secreted will certainly provide useful information render it a potential candidate for the biological control strategies of malaria and other disease vectors.

Prion Evolvability and the Hazard of Atypical Scrapie in Small Ruminants

2020 ◽  
Vol 1 (1) ◽  
pp. 1-14
Author(s):  
David B. Adams
Keyword(s):  
Disease Transmission ◽  
Western Europe ◽  
Current Knowledge ◽  
Small Ruminants ◽  
Classical Scrapie ◽  
Atypical Scrapie ◽  
Sheep And Goats ◽  
Preparedness Planning ◽  
Strain Behaviour ◽  
Third Stage

AbstractObservations on strain behaviour and direct demonstrations of natural selection establish that the scrapie agent and prions in general are able to evolve. Accordingly, it is conceivable that atypical non-contagious scrapie in sheep and goats can transform to classical contagious scrapie under particular circumstances. In consequence, atypical scrapie can be regarded as a latent hazard that warrants comprehensive risk assessment and biosecurity preparedness planning. Evidence for this proposition comes from differences in the expression of atypical and classical scrapie that may make scrapie contagious, historical records of scrapie in Western Europe, and contemporary accounts of the epidemiology of atypical scrapie. Biosecurity preparedness can be based on current knowledge of pathophysiology and epidemiology and can be built around a three-stage model for the endogenous emergence of a propagating epidemic of scrapie. The first stage concerns the occurrence of atypical scrapie. The second stage concerns the acquisition of communicability in prion populations provided by atypical scrapie and the third stage concerns circumstances allowing disease transmission and the initiation of a propagating epidemic. The range of component causes envisaged for possible outbreaks of endogenous classical scrapie is broad. However, exposure of sheep and goats to cyanobacterial toxins qualifies for special attention.

scholarly journals Haematophagous arthropod saliva and host defense system: a tale of tear and blood

2005 ◽  
Vol 77 (4) ◽  
pp. 665-693 ◽  
Author(s):  
Bruno B. Andrade ◽  
Clarissa R. Teixeira ◽  
Aldina Barral ◽  
Manoel Barral-Netto
Keyword(s):  
Immune Response ◽  
Immune Responses ◽  
Host Defense ◽  
Blood Meal ◽  
Disease Transmission ◽  
Blood Feeding ◽  
Defense System ◽  
Current Information ◽  
System A ◽  
Host Defense System

The saliva from blood-feeding arthropod vectors is enriched with molecules that display diverse functions that mediate a successful blood meal. They function not only as weapons against host's haemostatic, inflammatory and immune responses but also as important tools to pathogen establishment. Parasites, virus and bacteria taking advantage of vectors' armament have adapted to facilitate their entry in the host. Today, many salivary molecules have been identified and characterized as new targets to the development of future vaccines. Here we focus on current information on vector's saliva and the molecules responsible to modify host's hemostasis and immune response, also regarding their role in disease transmission.

Effect of flubendazole on the number of first-stage larvae of Angiostrongylus cantonensis released in the faeces of treated rats

1990 ◽  
Vol 64 (2) ◽  
pp. 87-95 ◽  
Author(s):  
Jun Maki ◽  
Toshio Yanagisawa
Keyword(s):  
Microscopic Examination ◽  
Post Infection ◽  
Egg Production ◽  
Angiostrongylus Cantonensis ◽  
Control Groups ◽  
Faecal Examination ◽  
Third Stage

ABSTRACTThe effect of flubendazole orally administered at 10 mg/kg/day for 5 consecutive days (the 11th, 20th or 40th post-infection) on the number of first-stage larvae (L1) of Angiostrongylus cantonensis released in the faeces of rats each infected with 40 third-stage larvae was determined. Faecal examination for 5 months, the period from medication to dissection of rats, showed that L1 release ceased in all the rats of medicated groups by about 1 week after the termination of dosing and resumed 1–2 months later in 86% of the rats which were dissected at the end of experiments with the recovery of adult worms of both sexes. Throughout the period of 5 months, about 2–4×104 L1/gram of fresh faeces was recorded in non-medicated control groups. There was a 38–79% reduction in adult worms at the dissection. Microscopic examination of the uteri of the remaining adult worms and lung tissues of rats confirmed no normal egg production in the adult worms from rats of medicated groups, except the rats with the resumption of faecal L1 release.

scholarly journals Observations on the feeding behaviour of parasitic third-stage hookworm larvae

Parasitology ◽  
1993 ◽  
Vol 106 (2) ◽  
pp. 163-169 ◽  
Author(s):  
J. M. Hawdon ◽  
S. W. Volk ◽  
R. Rose ◽  
D. I. Pritchard ◽  
J. M. Behnke ◽  
...  
Keyword(s):  
Small Intestine ◽  
Post Infection ◽  
Feeding Behaviour ◽  
The Other ◽  
Ancylostoma Caninum ◽  
Necator Americanus ◽  
Other Hand ◽  
Third Stage ◽  
Small Intestines

SUMMARYThe feeding behaviour of parasitic 3rd-stage larvae (L3) of the hookworms Ancylostoma caninum, A. ceylanicum and Necator americanus was examined. Less than 11% of A. caninum L3 recovered from the small intestines of dogs infected orally were feeding at 4–48 h post-infection (p.i.). and none of the A. ceylanicum L3 recovered from the intestines of orally infected hamsters had resumed feeding. All L4 of both species recovered at 36 and 48 h p.i. had resumed feeding. On the other hand, approximately 16% of the A. ceylanicum L3 recovered from the skin of percutaneously infected hamsters at 18 h were feeding, and the percentage feeding increased to nearly 58% at 44 h p.i. Necator americanus L3 recovered from the skin of percutaneously infected neonatal hamsters resumed feeding at 6–12 h p.i. and reached 90–94% by 18 h. Feeding began to decline at 66 h, and reached 29% at 120 h p.i. This decrease was associated with the migration of larvae from the skin to the lungs. By 192 h p.i. over 95% of the larvae had reached the small intestine, and all had moulted to the L4. The results indicate that parasitic L3 resume feeding in the skin during percutaneous infections, and suggest that feeding by hookworm L3 correlates with the resumption of development.

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