Mosquito-parasite interactions can shape filariasis transmission dynamics and impact elimination programs

Mathematical study of the dynamics of lymphatic filariasis infection via fractional-calculus

The infection of lymphatic filariasis (LF) is the primary cause of poverty and disability in individuals living with the disease. Many organizations globally are working toward mitigating the disease's impact and enhancing the quality of life of the affected patients. It is paramount to inspect the transmission pattern of this infection to provide effective interventions for its prevention and control. Here, we formulate an epidemic model for the progression process of LF with acute and chronic infection in the fractional framework. The basic concept of the novel Atangana-Baleanu operator is presented for the analysis of suggested system. We determine the basic reproduction number of the system via the approach of next-generation matrix and investigate the equilibria of the system for stability analysis. We have shown the impact of input factors on the outcomes of reproduction parameter with the help of partial rank correlation coefficient approach and visualize the most critical factors. To conceptualize the time series analysis of the suggested dynamics, we propose utilizing a numerical approach. The solution pathways of the system are illustrated to demonstrate how different settings affect the system. We demonstrate the dynamics of the infection numerically to educate the policy makers and health authorities about the mechanisms necessary for management and control.

Mosquito-Borne Diseases Emergence/Resurgence and How to Effectively Control It Biologically

Deadly pathogens and parasites are transmitted by vectors and the mosquito is considered the most threatening vector in public health, transmitting these pathogens to humans and animals. We are currently witnessing the emergence/resurgence in new regions/populations of the most important mosquito-borne diseases, such as arboviruses and malaria. This resurgence may be the consequence of numerous complex parameters, but the major cause remains the mismanagement of insecticide use and the emergence of resistance. Biological control programmes have rendered promising results but several highly effective techniques, such as genetic manipulation, remain insufficiently considered as a control mechanism. Currently, new strategies based on attractive toxic sugar baits and new agents, such as Wolbachia and Asaia, are being intensively studied for potential use as alternatives to chemicals. Research into new insecticides, Insect Growth Regulators, and repellent compounds is pressing, and the improvement of biological strategies may provide key solutions to prevent outbreaks, decrease the danger to at-risk populations, and mitigate resistance.

Human Migration and the Spread of the Nematode Parasite Wuchereria bancrofti

The human disease lymphatic filariasis causes the debilitating effects of elephantiasis and hydrocele. Lymphatic filariasis currently affects the lives of 90 million people in 52 countries. There are three nematodes that cause lymphatic filariasis, Brugia malayi, Brugia timori, and Wuchereria bancrofti, but 90% of all cases of lymphatic filariasis are caused solely by W. bancrofti (Wb). Here we use population genomics to reconstruct the probable route and timing of migration of Wb strains that currently infect Africa, Haiti, and Papua New Guinea (PNG). We used selective whole genome amplification to sequence 42 whole genomes of single Wb worms from populations in Haiti, Mali, Kenya, and PNG. Our results are consistent with a hypothesis of an Island Southeast Asia or East Asian origin of Wb. Our demographic models support divergence times that correlate with the migration of human populations. We hypothesize that PNG was infected at two separate times, first by the Melanesians and later by the migrating Austronesians. The migrating Austronesians also likely introduced Wb to Madagascar where later migrations spread it to continental Africa. From Africa, Wb spread to the New World during the transatlantic slave trade. Genome scans identified 17 genes that were highly differentiated among Wb populations. Among these are genes associated with human immune suppression, insecticide sensitivity, and proposed drug targets. Identifying the distribution of genetic diversity in Wb populations and selection forces acting on the genome will build a foundation to test future hypotheses and help predict response to current eradication efforts.

GEOFIL: A spatially-explicit agent-based modelling framework for predicting the long-term transmission dynamics of lymphatic filariasis in American Samoa

In this study, a spatially-explicit agent-based modelling framework GEOFIL was developed to predict lymphatic filariasis (LF) transmission dynamics in American Samoa. GEOFIL included individual-level information on age, gender, disease status, household location, household members, workplace/school location and colleagues/schoolmates at each time step during the simulation. In American Samoa, annual mass drug administration from 2000 to 2006 successfully reduced LF prevalence dramatically. However, GEOFIL predicted continual increase in microfilaraemia prevalence in the absence of further intervention. Evidence from seroprevalence and transmission assessment surveys conducted from 2010 to 2016 indicated a resurgence of LF in American Samoa, corroborating GEOFIL's predictions. The microfilaraemia and antigenaemia prevalence in 6-7-yo children were much lower than in the overall population. Mosquito biting rates were found to be a critical determinant of infection risk. Transmission hotspots are likely to disappear with lower biting rates. GEOFIL highlights current knowledge gaps, such as data on mosquito abundance, biting rates and within-host parasite dynamics, which are important for improving the accuracy of model predictions.

A Trial of a Triple-Drug Treatment for Lymphatic Filariasis

BACKGROUND

The World Health Organization has targeted lymphatic filariasis for global elimination by 2020 with a strategy of mass drug administration. This trial tested whether a single dose of a three-drug regimen of ivermectin plus diethylcarbamazine plus albendazole results in a greater sustained clearance of microfilariae than a single dose of a two-drug regimen of diethylcarbamazine plus albendazole and is noninferior to the two-drug regimen administered once a year for 3 years.

METHODS

In a randomized, controlled trial involving adults from Papua New Guinea with Wuchereria bancrofti microfilaremia, we assigned 182 participants to receive a single dose of the three-drug regimen (60 participants), a single dose of the two-drug regimen (61 participants), or the two-drug regimen once a year for 3 years (61 participants). Clearance of microfilariae from the blood was measured at 12, 24, and 36 months after trial initiation.

RESULTS

The three-drug regimen cleared microfilaremia in 55 of 57 participants (96%) at 12 months, in 52 of 54 participants (96%) at 24 months, and in 55 of 57 participants (96%) at 36 months. A single dose of the two-drug regimen cleared microfilaremia in 18 of 56 participants (32%) at 12 months, in 31 of 55 participants (56%) at 24 months, and in 43 of 52 participants (83%) at 36 months (P=0.02 for the three-drug regimen vs. a single dose of the two-drug regimen at 36 months). The two-drug regimen administered once a year for 3 years cleared microfilaremia in 20 of 59 participants (34%) at 12 months, in 42 of 56 participants (75%) at 24 months, and in 51 of 52 participants (98%) at 36 months (P=0.004 for noninferiority of the three-drug regimen vs. the two-drug regimen administered once a year for 3 years at 36 months). Moderate adverse events were more common in the group that received the three-drug regimen than in the combined two-drug-regimen groups (27% vs. 5%, P<0.001). There were no serious adverse events.

CONCLUSIONS

The three-drug regimen induced clearance of microfilariae from the blood for 3 years in almost all participants who received the treatment and was superior to the two-drug regimen administered once and noninferior to the two-drug regimen administered once a year for 3 years. (Funded by the Bill and Melinda Gates Foundation; ClinicalTrials.gov number, NCT01975441 .).

Immune responses of Aedes togoi, Anopheles paraliae and Anopheles lesteri against nocturnally subperiodic Brugia malayi microfilariae during migration from the midgut to the site of development

Background

Lymphatic filariasis is a mosquito-borne disease caused by filarioid nematodes. A comparative understanding of parasite biology and host-parasite interactions can provide information necessary for developing intervention programmes for vector control. Here, to understand such interactions, we choose highly susceptible filariasis vectors (Aedes togoi and Anopheles lesteri) as well as Anopheles paraliae, which has lower susceptibility, infected them with nocturnally subperiodic (NSP) Brugia malayi microfilariae (mf) and studied the exsheathment, migration and innate immune responses among them.

Methods

Mosquito-parasite relationships were systematically investigated from the time mf entered the midgut until they reached their development site in the thoracic musculature (12 time points).

Results

Results showed that exsheathment of B. malayi mf occurred in the midgut of all mosquito species and was completed within 24 h post-blood meal. The migration of B. malayi mf from the midgut to thoracic muscles of the highly susceptible mosquitoes Ae. togoi and An. lesteri was more rapid than in the low susceptibility mosquito, An. paraliae. Melanisation and degeneration, two distinct refractory phenotypes, of mf were found in the midgut, haemocoel and thoracic musculature of all mosquito species. Melanisation is a complex biochemical cascade that results in deposition of melanin pigment on a capsule around the worms. Also, some biological environments in the body are inhospitable to parasite development and cause direct toxicity that results in vacuolated or degenerated worms. Even though Ae. togoi is highly susceptible to B. malayi, melanisation responses against B. malayi mf were first noted in the haemocoel of Ae. togoi, followed by a degeneration process. In contrast, in An. lesteri and An. paraliae, the degeneration process occurred in the haemocoel and thoracic musculature prior to melanisation responses.

Conclusion

This study provides a thorough description of the comparative pathobiology of responses of mosquitoes against the filarial worm B. malayi.

The History of Bancroftian Lymphatic Filariasis in Australasia and Oceania: Is There a Threat of Re-Occurrence in Mainland Australia?

Lymphatic filariasis (LF) infects an estimated 120 million people worldwide, with a further 856 million considered at risk of infection and requiring preventative chemotherapy. The majority of LF infections are caused by Wuchereria bancrofti, named in honour of the Australian physician Joseph Bancroft, with the remainder due to Brugia malayi and B. timori. Infection with LF through the bite of an infected mosquito, can lead to the development of the condition known as elephantiasis, where swelling due to oedema leads to loss of function in the affected area and thickening of the skin, 'like an elephant'. LF has previously been endemic in Australia, although currently, no autochthonous cases occur there. Human immigration to Australia from LF-endemic countries, including those close to Australia, and the presence of susceptible mosquitoes that can act as suitable vectors, heighten the possibility of the reintroduction of LF into this country. In this review, we examine the history of LF in Australia and Oceania and weigh up the potential risk of its re-occurrence on mainland Australia.

Insulin receptor knockdown blocks filarial parasite development and alters egg production in the southern house mosquito, Culex quinquefasciatus

Lymphatic filariasis, commonly known as elephantiasis, is a painful and profoundly disfiguring disease. Wuchreria bancrofti (Wb) is responsible for >90% of infections and the remainder are caused by Brugia spp. Mosquitoes of the genera Culex (in urban and semi-urban areas), Anopheles (in rural areas of Africa and elsewhere), and Aedes (in Pacific islands) are the major vectors of W. bancrofti. A preventive chemotherapy called mass drug administration (MDA), including albendazole with ivermectin or diethylcarbamazine citrate (DEC) is used in endemic areas. Vector control strategies such as residual insecticide spraying and long-lasting insecticidal nets are supplemental to the core strategy of MDA to enhance elimination efforts. However, increasing insecticide resistance in mosquitoes and drug resistance in parasite limit the effectiveness of existing interventions, and new measures are needed for mosquito population control and disruption of mosquito-parasite interactions to reduce transmission. Mosquito insulin signaling regulates nutrient metabolism and has been implicated in reduced prevalence and intensity of malaria parasite, Plasmodium falciparum, infection in mosquitoes. Currently no data are available to assess how insulin signaling in mosquitoes affects the development of multi-cellular parasites, such as filarial nematodes. Here, we show that insulin receptor knockdown in blood fed C. quinquefasciatus, the major vector of Wb in India, completely blocks the development of filarial nematode parasite to the infective L3 stage, and results in decreased ecdysteroid production and trypsin activity leading to fewer mosquito eggs. These data indicate that a functional mosquito insulin receptor (IR) is necessary for filarial parasite development and mosquito reproduction. Therefore, insulin signaling may represent a new target for the development of vector control or parasite blocking strategies.

Lymphatic filariasis (LF) is caused by infection with nematodes of the family Filarioidea. 90% of infections are caused by Wuchereria bancrofti and the remainder by Brugia spp. In endemic countries, LF has a major social and economic impact with an estimated annual loss of $1 billion. Filarial infection can cause a variety of clinical manifestations, including lymphoedema of the limbs, genital disease (hydrocele, and swelling of the scrotum and penis) and recurrent acute attacks, which are extremely painful and are accompanied by fever. As one of the leading causes of global disability, LF accounts for at least 2.8 million disability-adjusted life year (DALY). Mass drug administration (MDA) is used prophylactically on the community level where the infection is present to decrease disease transmission. These drugs have limited effect on adult parasites but effectively reduce microfilariae in the bloodstream and prevent the spread of microfilaria to mosquitoes. Use of mosquito population control strategies is supplemental to the core strategy of MDA. However, increasing insecticide resistance in mosquitoes and drug resistant nematode parasites are complicating elimination efforts and emphasizes the need for novel interventions for vector control and parasite transmission. Insulin signaling is a highly conserved signaling pathway that regulates growth and nutrient homeostasis in animals. Our previous work in Aedes aegypti mosquitoes showed additional roles of insulin receptor signaling in blood digestion and reproduction. The present data strongly supports our previous findings in a different mosquito species and further explores the role of mosquito insulin receptor in the development of the filarial nematode to the infective stage. This information is pertinent to ongoing efforts to control and eradicate filariasis because insulin signaling may represent a new target for the development of vector control or transmission blocking strategies.

Mosquito Immunobiology: The Intersection of Vector Health and Vector Competence

As holometabolous insects that occupy distinct aquatic and terrestrial environments in larval and adult stages and utilize hematophagy for nutrient acquisition, mosquitoes are subjected to a wide variety of symbiotic interactions. Indeed, mosquitoes play host to endosymbiotic, entomopathogenic, and mosquito-borne organisms, including protozoa, viruses, bacteria, fungi, fungal-like organisms, and metazoans, all of which trigger and shape innate infection-response capacity. Depending on the infection or interaction, the mosquito may employ, for example, cellular and humoral immune effectors for septic infections in the hemocoel, humoral infection responses in the midgut lumen, and RNA interference and programmed cell death for intracellular pathogens. These responses often function in concert, regardless of the infection type, and provide a robust front to combat infection. Mosquito-borne pathogens and entomopathogens overcome these immune responses, employing avoidance or suppression strategies. Burgeoning methodologies are capitalizing on this concerted deployment of immune responses to control mosquito-borne disease.

Mathematical analysis of a lymphatic filariasis model with quarantine and treatment

BACKGROUND

Lymphatic filariasis is a globally neglected tropical parasitic disease which affects individuals of all ages and leads to an altered lymphatic system and abnormal enlargement of body parts.

METHODS

A mathematical model of lymphatic filariaris with intervention strategies is developed and analyzed. Control of infections is analyzed within the model through medical treatment of infected-acute individuals and quarantine of infected-chronic individuals.

RESULTS

We derive the effective reproduction number, [Formula: see text] and its interpretation/investigation suggests that treatment contributes to a reduction in lymphatic filariasis cases faster than quarantine. However, this reduction is greater when the two intervention approaches are applied concurrently.

CONCLUSIONS

Numerical simulations are carried out to monitor the dynamics of the filariasis model sub-populations for various parameter values of the associated reproduction threshold. Lastly, sensitivity analysis on key parameters that drive the disease dynamics is performed in order to identify their relative importance on the disease transmission.

Modeling the Parasitic Filariasis Spread by Mosquito in Periodic Environment

In this paper a mosquito-borne parasitic infection model in periodic environment is considered. Threshold parameter R0 is given by linear next infection operator, which determined the dynamic behaviors of system. We obtain that when R0 < 1, the disease-free periodic solution is globally asymptotically stable and when R0 > 1 by Poincaré map we obtain that disease is uniformly persistent. Numerical simulations support the results and sensitivity analysis shows effects of parameters on R0, which provided references to seek optimal measures to control the transmission of lymphatic filariasis.

Filarial infection influences mosquito behaviour and fecundity

Understanding vector-parasite interactions is increasingly important as we move towards the endpoint goals set by the Global Programme for the Elimination of Lymphatic Filariasis (GPELF), as interaction dynamics may change with reduced transmission pressure. Elimination models used to predict programmatic endpoints include parameters for vector-specific transmission dynamics, despite the fact that our knowledge of the host-seeking behaviour of filariasis infected mosquitoes is lacking. We observed a dynamic, stage-specific and density dependent change in Aedes aegypti behaviour towards host cues when exposed to Brugia malayi filarial parasites. Infected mosquitoes exhibited reduced activation and flight towards a host during the period of larval development (L1/L2), transitioning to a 5 fold increase in activation and flight towards a host when infective stage larvae (L3) were present (p < 0.001). In uninfected control mosquitoes, we observed a reduction in convergence towards a host during the same period. Furthermore, this behaviour was density dependent with non-activated mosquitoes harbouring a greater burden of L1 and L2 larvae while activated mosquitoes harboured a greater number of L3 (p < 0.001). Reductions in fecundity were also density-dependent, and extended to mosquitoes that were exposed to microfilariae but did not support larval development.

Population genomics of the filarial nematode parasite Wuchereria bancrofti from mosquitoes

Wuchereria bancrofti is a parasitic nematode and the primary cause of lymphatic filariasis--a disease specific to humans. W. bancrofti currently infects over 90 million people throughout the tropics and has been acknowledged by the world health organization as a vulnerable parasite. Current research has focused primarily on the clinical manifestations of disease and little is known about the evolutionary history of W. bancrofti. To improve upon knowledge of the evolutionary history of W. bancrofti, we whole genome sequenced 13 W. bancrofti larvae. We circumvent many of the difficulties of multiple infections by sampling larvae directly from mosquitoes that were experimentally inoculated with infected blood. To begin, we used whole genome data to reconstruct the historical population size. Our results support a history of fluctuating population sizes that can be correlated with human migration and fluctuating mosquito abundances. Next, we reconstructed the putative pedigree of W. bancrofti worms within an infection using the kinship coefficient. We deduced that there are full-sib and half-sib relationships residing within the same larval cohort. Through combined analysis of the mitochondrial and nuclear genomes we concluded that this is likely a results of polyandrous mating, the first time reported for W. bancrofti. Lastly, we scanned the genomes for signatures of natural selection. Annotation of putative selected regions identified proteins that may have aided in a parasitic life style or may have evolved to protect against current drug treatments. We discuss our results in the greater context of understanding the biology of an animal with a unique life history and ecology.

Fit for purpose: do we have the right tools to sustain NTD elimination?

Priorities for NTD control programmes will shift over the next 10-20 years as the elimination phase reaches the ‘end game’ for some NTDs, and the recognition that the control of other NTDs is much more problematic. The current goal of scaling up programmes based on preventive chemotherapy (PCT) will alter to sustaining NTD prevention, through sensitive surveillance and rapid response to resurgence. A new suite of tools and approaches will be required for both PCT and Intensive Disease Management (IDM) diseases in this timeframe to enable disease endemic countries to:

1. Sensitively and sustainably survey NTD transmission and prevalence in order to identify and respond quickly to resurgence.

2. Set relevant control targets based not only on epidemiological indicators but also entomological and ecological metrics and use decision support technology to help meet those targets.

3. Implement verified and cost-effective tools to prevent transmission throughout the elimination phase.

Liverpool School of Tropical Medicine (LSTM) and partners propose to evaluate and implement existing tools from other disease systems as well as new tools in the pipeline in order to support endemic country ownership in NTD decision-making during the elimination phase and beyond.

Presence of Wuchereria bancrofti microfilaremia despite 7 years of annual ivermectin monotherapy mass drug administration for onchocerciasis control: a study in north-west Ethiopia

BACKGROUND

There is considerable interest in determining whether mass drug administration (MDA) with ivermectin for onchocerciasis control will eliminate coendemic lymphatic filariasis (LF). The objective of this study was to determine the prevalence of LF microfilaremia in onchocerciasis endemic districts that had received 7 years of MDA with ivermectin.

METHOD

Three villages with a 2010 LF circulating antigenaemia prevalence (determined in a mapping exercise using immunochromatography tests) ranging from 23 to 56% were surveyed for the presence of Wuchereria bancrofti microfilaria (mf) in 2012. These villages had been treated with ivermectin MDA for onchocerciasis with reported total population coverage of ≥65%. A total of 774 residents aged 2 years and above, of both genders, provided 60 μl nocturnal blood samples between 10 pm and 2 am. Standard thick smears were prepared and examined microscopically after Giemsa staining for the presence of W. bancrofti mf.

RESULTS

The mean mf prevalence was 4.7% (village range 1.1-11.0%). The mean mf density was 9.8 mf/60 μl (village range 9-13.1) among the positive individuals. Children in the 2-4-year-old and 5-9-year-old age groups were infected suggesting transmission occurred during the MDA period. A village level review of MDA treatment coverage records showed an average total population coverage of 66.4% over a 7-year period, but with a considerable range of annual coverage (43.0-89.9%). In addition, village level treatment coverage data were missing from the village with the highest mf prevalence (11%) for 2 of the 7 years.

CONCLUSION

7 years of annual mass treatment with ivermectin monotherapy for onchocerciasis did not interrupt LF transmission. In expanding the onchocerciasis ivermectin MDA programme to include LF, albendazole should be added and treatment coverage improved.

How effective is integrated vector management against malaria and lymphatic filariasis where the diseases are transmitted by the same vector?

BACKGROUND

The opportunity to integrate vector management across multiple vector-borne diseases is particularly plausible for malaria and lymphatic filariasis (LF) control where both diseases are transmitted by the same vector. To date most examples of integrated control targeting these diseases have been unanticipated consequences of malaria vector control, rather than planned strategies that aim to maximize the efficacy and take the complex ecological and biological interactions between the two diseases into account.

METHODOLOGY/PRINCIPAL FINDINGS

We developed a general model of malaria and LF transmission and derived expressions for the basic reproductive number (R0) for each disease. Transmission of both diseases was most sensitive to vector mortality and biting rate. Simulating different levels of coverage of long lasting-insecticidal nets (LLINs) and larval control confirms the effectiveness of these interventions for the control of both diseases. When LF was maintained near the critical density of mosquitoes, minor levels of vector control (8% coverage of LLINs or treatment of 20% of larval sites) were sufficient to eliminate the disease. Malaria had a far greater R0 and required a 90% population coverage of LLINs in order to eliminate it. When the mosquito density was doubled, 36% and 58% coverage of LLINs and larval control, respectively, were required for LF elimination; and malaria elimination was possible with a combined coverage of 78% of LLINs and larval control.

CONCLUSIONS/SIGNIFICANCE

Despite the low level of vector control required to eliminate LF, simulations suggest that prevalence of LF will decrease at a slower rate than malaria, even at high levels of coverage. If representative of field situations, integrated management should take into account not only how malaria control can facilitate filariasis elimination, but strike a balance between the high levels of coverage of (multiple) interventions required for malaria with the long duration predicted to be required for filariasis elimination.

Molecular epidemiology, phylogeny and evolution of the filarial nematode Wuchereria bancrofti

Wuchereria bancrofti (Wb) is the most widely distributed of the three nematodes known to cause lymphatic filariasis (LF), the other two being Brugia malayi and Brugia timori. Current tools available to monitor LF are limited to diagnostic tests targeting DNA repeats, filarial antigens, and anti-filarial antibodies. While these tools are useful for detection and surveillance, elimination programs have yet to take full advantage of molecular typing for inferring infection history, strain fingerprinting, and evolution. To date, molecular typing approaches have included whole mitochondrial genomes, genotyping, targeted sequencing, and random amplified polymorphic DNA (RAPDs). These studies have revealed much about Wb biology. For example, in one study in Papua New Guinea researchers identified 5 major strains that were widespread and many minor strains some of which exhibit geographic stratification. Genome data, while rare, has been utilized to reconstruct evolutionary relationships among taxa of the Onchocercidae (the clade of filarial nematodes) and identify gene synteny. Their phylogeny reveals that speciation from the common ancestor of both B. malayi and Wb occurred around 5-6 millions years ago with shared ancestry to other filarial nematodes as recent as 15 million years ago. These discoveries hold promise for gene discovery and identifying drug targets in species that are more amenable to in vivo experiments. Continued technological developments in whole genome sequencing and data analysis will likely replace many other forms of molecular typing, multiplying the amount of data available on population structure, genetic diversity, and phylogenetics. Once widely available, the addition of population genetic data from genomic studies should hasten the elimination of LF parasites like Wb. Infectious disease control programs have benefited greatly from population genetics data and recently from population genomics data. However, while there is currently a surplus of data for diseases like malaria and HIV, there is a scarcity of this data for filarial nematodes. With the falling cost of genome sequencing, research on filarial nematodes could benefit from the addition of population genetics statistics and phylogenetics especially in dealing with elimination programs. A comprehensive review focusing on population genetics of filarial nematode does not yet exist. Here our goal is to provide a current overview of the molecular epidemiology of W. bancrofti (Wb) the primary causative agent of LF. We begin by reviewing studies utilizing molecular typing techniques with specific focus on genomic and population datasets. Next, we used whole mitochondrial genome data to construct a phylogeny and examine the evolutionary history of the Onchocercidae. Then, we provide a perspective to aid in understanding how population genetic techniques translate to modern epidemiology. Finally, we introduce the concept of genomic epidemiology and provide some examples that will aid in future studies of Wb.

Dual RNA-seq of parasite and host reveals gene expression dynamics during filarial worm-mosquito interactions

BACKGROUND

Parasite biology, by its very nature, cannot be understood without integrating it with that of the host, nor can the host response be adequately explained without considering the activity of the parasite. However, due to experimental limitations, molecular studies of parasite-host systems have been predominantly one-sided investigations focusing on either of the partners involved. Here, we conducted a dual RNA-seq time course analysis of filarial worm parasite and host mosquito to better understand the parasite processes underlying development in and interaction with the host tissue, from the establishment of infection to the development of infective-stage larva.

METHODOLOGY/PRINCIPAL FINDINGS

Using the Brugia malayi-Aedes aegypti system, we report parasite gene transcription dynamics, which exhibited a highly ordered developmental program consisting of a series of cyclical and state-transitioning temporal patterns. In addition, we contextualized these parasite data in relation to the concurrent dynamics of the host transcriptome. Comparative analyses using uninfected tissues and different host strains revealed the influence of parasite development on host gene transcription as well as the influence of the host environment on parasite gene transcription. We also critically evaluated the life-cycle transcriptome of B. malayi by comparing developmental stages in the mosquito relative to those in the mammalian host, providing insight into gene expression changes underpinning the mosquito-borne parasitic lifestyle of this heteroxenous parasite.

CONCLUSIONS/SIGNIFICANCE

The data presented herein provide the research community with information to design wet lab experiments and select candidates for future study to more fully dissect the whole set of molecular interactions of both organisms in this mosquito-filarial worm symbiotic relationship. Furthermore, characterization of the transcriptional program over the complete life cycle of the parasite, including stages within the mosquito, could help devise novel targets for control strategies.