ABSTRACT
In Argentina, the distribution of Aedes albopictus (Skuse) is limited to two provinces with a subtropical climate and few records. This study aims to describe and compare assemblies of Culicidae that breed in artificial containers in two areas with different degrees of urbanisation where Ae. albopictus is present and to evaluate possible biotic interactions. We sampled container larval habitats of an urban (Eldorado city) and a rural environment (Colonia Aurora village). We performed generalized linear mixed models to evaluate which variables (containers characteristics or environment) are associated with the presence and abundance of Ae. albopictus, Aedes aegypti Linneaus and Culex quinquefasciatus Say, and the presence of mosquito predators (Lutzia bigoti (Bellardi) and Toxorhynchites spp.). Also, the relationship between the most abundant species was quantified in each environment using Hurlbert's C8 association coefficient. Ae. aegypti was the most abundant species in the urban environment, while Cx. quinquefasciatus and Ae. albopictus were the most abundant in the rural area. Predators were more present in the rural environment and affected the abundance of Aedes mosquitoes. Regarding the C8 index, Ae. aegypti was negatively associated with Ae. albopictus in the urban area, whereas in the rural area these species presented a significantly positive relationship. These results show that in urban environments the high abundance of Ae. aegypti could be affecting the Asian tiger mosquito as evidenced by local studies of food larval competition. Also a greater presence of predators could be affecting Ae. albopictus in rural environments.
Subject(s)
Aedes , Culex , Culicidae , Animals , Argentina , Environment , Ecosystem , LarvaABSTRACT
Cities usually offer a suitable environment for the dengue vector Aedes aegypti, providing oviposition sites, accessibility to human hosts and nectar meals. However, large urban centres are highly heterogeneous environments, forming a patched landscape that could affect Ae. aegypti population dynamics and dispersal. Here, we performed a genome-wide analysis using Rad-seq data from 99 Ae. aegypti specimens collected in three areas within Buenos Aires city with varying levels of urbanization/land use: highly urbanized Area 1, intermediate Area 2 and poorly urbanized Area 3. We found an inverse association between urbanization levels and spatial genetic structure. Populations from highly urbanized Area 1 did not present genetic structure whereas two and three clusters were detected in Areas 2 and 3, respectively. In the case of Area 3, initial analyses showed separation in clusters was mostly due to elevated consanguinity within sites although three clusters were still detected after closely related individuals were discarded. Mosquitoes around each site displayed a high degree of isolation, evidencing a close dependence between the vector and human dwellings. Interestingly, specimens from distant boroughs (within the limits of the city) and the city's outskirts formed a single cluster with inner city sites (Area 1), highlighting the role of passive transport in shaping population structure. Genetic distances were poorly correlated with geographic distances in Buenos Aires, suggesting a stronger influence of passive than active dispersal on population structure. Only Area 2 displayed a significant isolation-by-distance pattern (p = 0.046), with males dispersing more than females (p = 0.004 and p = 0.016, respectively). Kinship analyses allowed us to detect full-siblings located 1.5 km apart in Area 1, which could be due to an extreme event of active female dispersal. Effective population size was higher in Area 2 confirming that cemeteries represent highly favourable environments for Ae. aegypti and need to be specifically targeted. Our results suggest that control programs should take into account urban landscape heterogeneity in order to improve vector control.
Subject(s)
Aedes , Aedes/genetics , Animals , Cities , Female , Genetic Structures , Genetics, Population , Humans , Male , Mosquito Vectors/genetics , Urban PopulationABSTRACT
Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse) are worldwide vectors of dengue and yellow fever viruses. These species coexist in many countries and the biotic interactions between them can influence their abundances and distributions. In Argentina, Ae. aegypti is widely distributed in the north and center regions of the country, with temperate and subtropical climate, while both are sympatric only in the northeastern area of the subtropical region. Interspecific and intraspecific larval competition for food was evaluated to assess if their interaction influences on patterns of abundance and distribution. Finite rates of increase and survivorship for each species were estimated and the effects of mosquito density ratio and detritus availability were determined. The Lambda (λ´) index of population performance of both showed there is no competitive exclusion pattern. However, survival of Ae. albopictus was negatively affected by the presence of Ae. aegypti. These results suggest one possible explanation for the codominance pattern of both species display in rural regions of the southernmost distribution of Ae. albopictus in South America. They also show Ae. aegypti as a potential biotic barrier for the expansion of Ae. albopictus as was reported in regions of the United States.
Subject(s)
Aedes , Animals , Argentina , Larva , Mosquito Vectors , South AmericaABSTRACT
Aedes aegypti is the primary vector of arboviruses of great impact on human health. Our goal was to assess the spatial genetic structure of Ae. aegypti at the regional and local levels in Northwestern Argentina, an area with high prevalence of dengue fever. We analyzed 59 Ae. aegypti individuals collected from six locations in Northwestern Argentina using nuclear genome-wide Single Nucleotide Polymorphisms (SNPs) generated with double digest Restriction-site Associated DNA Sequencing. We also performed an entomological survey in 70 households in the cities of Orán and Tartagal. An analysis at the regional level indicated that the populations of Ae. aegypti in Northwestern Argentina are spatially structured and present a significant IBD pattern. Our results suggest that passive transport of eggs/immature stages, in both northward and southward directions, plays an important role in structuring Ae. aegypti populations at a regional scale and also as a source for the introduction of novel genetic variants through migration events into established populations. At a local level, we found neither spatial genetic structure nor significant isolation by distance (IBD) in Tartagal, indicating high gene flow within the city and active dispersal. In contrast, samples from Orán formed two clusters with a significant IBD pattern, although weaker than that at a regional level. Both populations showed signs of recent bottleneck events, probably coincident with past eradication campaigns. The entomological survey revealed a high prevalence of Ae. aegypti in both cities, although significantly higher in Tartagal.
Subject(s)
Aedes/genetics , Gene Flow , Genetic Variation , Mosquito Vectors/genetics , Animal Distribution , Animals , Argentina , FemaleABSTRACT
Las diarreas agudas son una de las afecciones más comunes en personas de todas las edades, especialmente en niños menores de 5 años. Rotavirus (RV) es la principal causa de diarrea en niños a nivel mundial seguido por norovirus (NoV). Sin embargo, a partir de la implementación de la vacunación con RV, NoV pasó a tener un rol preponderante en varios países como EEUU y Nicaragua. En Argentina, luego del inicio de la vacunación obligatoria de RV se logró un alto porcentaje de cobertura vacunal y se evidenció un descenso del 10% en la ocurrencia de diarreas agudas en general y un descenso del 50% de las diarreas causadas específicamente por RV, demostrando el éxito rotundo de la intervención. No existen al momento vacunas contra NoV, lo que lleva al desarrollo de otras estrategias de contención. A través del laboratorio INCUINTA del Instituto Nacional de Tecnología Agropecuaria (INTA), se han desarrollado y patentado nanoanticuerpos VHH contra RV y NoV con propiedades que los transforman en excelentes herramientas para el desarrollo de métodos de diagnóstico y para su utilización en estrategias de inmunidad pasiva oral para el tratamiento y prevención de la infección causada por estos agentes virales. Los nanoanticuerpos anti RV fueron utilizados con éxito para el desarrollo de un kit de ELISA nacional validado junto con el Instituto Malbrán que está siendo registrado para su comercialización. Además, demostraron poseer capacidad neutralizante de la infección contra RV in vitro y protección frente a la diarrea y excreción viralen los modelos de ratones lactantes y cerdos gnotobióticos. Los nano anticueroscontra NoV poseen alta afinidad para la detección del virus y fueron capaces de bloquear la unión del virus a los receptores celulares in vitro, demostrando su potencial como moléculas terapéuticas y de diagnóstico. El objetivo final de este desarrollo es completar la triada diagnostico-prevencióntratamiento para el control de las gastroenteritis virales con una tecnología de vanguardia de industria nacional.
Acute diarrhea is a common affection in people ofall ages, especially in children under five years old. Rotavirus (RV) is the major cause of diarrhea in children worldwide followed by norovirus (NoV). However, afterthe introduction of RV vaccine in the vaccination calendar in several countries like the USA and Nicaragua, NoV is having an important role in gastroenteritis incidence. In Argentina, after the introduction of the RV vaccine, high vaccine coverage was reached and the overall acute diarrhea incidence was reduced in a 10% and RV-associated diarrhea was reduced 50%, leading to complete success of the vaccination strategy. At the moment, there are no vaccines against NoV, thus, it is a need to develop therapies to control this disease. INCUINTA has developed and patented two sets of VHH nanobodies against RV and NoV with unique properties that make them suitable for the development of diagnostic tools, as well as to design oral passive immune strategies to preventand treat these two viral infections associated with diarrhea. VHH against rotavirus were able to neutralize RV infection in a suckling mouse model and in a gnotobiotic pig model of human RV infection and disease. Also, they were used to develop an ELISA kit for RV detection in human and animal samples. The ELISA kit was statistically validated in collaboration with the Malbrán Institute and is being registered for commercialization. VHH to NoVs showed high affinity to the virus and blocked the interaction between the virus and histo-blood antigens in target cells in vitro, showing to be a potential tool to detect and treat NoV infection. The final goal of this project is to complete the diagnostic-prevention-treatment triad to control viral gastroenteritis using a vanguard technology made in Argentina.
Subject(s)
Camelids, New World , Rotavirus , Diarrhea , Single-Domain AntibodiesABSTRACT
Species A Rotaviruses (RVA) remain a leading cause of mortality in children under 5 years of age. Current treatment options are limited. We assessed the efficacy of two VP6-specific llama-derived heavy chain antibody fragments (VHH) -2KD1 and 3B2- as an oral prophylactic and therapeutic treatment against RVA-induced diarrhea in a neonatal mouse model inoculated with virulent murine RVA (ECw, G16P[16]I7). Joint therapeutic administration of 2KD1+3B2 (200 µg/dose) successfully reduced diarrhea duration, RVA infection severity and virus shedding in feces. While the same dose of 2KD1 or 3B2 (200 µg) significantly reduced duration of RVA-induced diarrhea, 2KD1 was more effective in diminishing the severity of intestinal infection and RVA shedding in feces, perhaps because 2KD1 presented higher binding affinity for RVA particles than 3B2. Neither prophylactic nor therapeutic administration of the VHH interfered with the host's humoral immune response against RVA. When 2KD1 (200 µg) was administered after diarrhea development, it also significantly reduced RVA intestinal infection and fecal shedding. Host antibody responses against the oral VHH treatment were not detected, nor did viral escape mutants. Our findings show that oral administration of anti-VP6 VHH constitute, not only an effective prophylactic treatment against RVA-associated diarrhea, but also a safe therapeutic tool against RVA infection, even once diarrhea is present. Anti-VP6 VHH could be used complementary to ongoing vaccination, especially in populations that have shown lower immunization efficacy. These VHH could also be scaled-up to develop pediatric medication or functional food like infant milk formulas that might help treat RVA diarrhea.
Subject(s)
Immunoglobulin Heavy Chains/therapeutic use , Immunoglobulin Variable Region/therapeutic use , Rotavirus Infections/drug therapy , Rotavirus Infections/virology , Rotavirus/physiology , Animals , Animals, Newborn , Camelids, New World , Diarrhea/drug therapy , Diarrhea/virology , Feces/virology , Hydrogen-Ion Concentration , Immunity, Humoral/immunology , Immunoglobulin Heavy Chains/administration & dosage , Immunoglobulin Variable Region/administration & dosage , Intestines/pathology , Intestines/virology , Mice, Inbred BALB C , Mutation/genetics , Phylogeny , Proteolysis , Rotavirus Infections/immunology , Virion/metabolism , Virus SheddingABSTRACT
Group A Rotavirus (RVA) remains a leading cause of severe diarrhea and child mortality. The variable domain of camelid heavy chain antibodies (VHH) display potent antigen-binding capacity, have low production costs and are suitable for oral therapies. Two sets of anti-RVA VHHs have been developed: ARP1-ARP3; 2KD1-3B2. Here, we explore the potential of both sets as a prevention strategy complementary to vaccination and a treatment option against RVA-associated diarrhea in endangered populations. Both sets have been expressed in multiple production systems, showing extensive neutralizing capacity against strains of RVA in vitro. They were also tested in the neonatal mouse model with various degrees of success in preventing or treating RVA-induced diarrhea. Interestingly, mitigation of the symptoms was also achieved with freeze-dried ARP1, so that it could be applied in areas where cold chains are difficult to maintain. 3B2 was tested in a pre-clinical trial involving gnotobiotic piglets where it conferred complete protection against RVA-induced diarrhea. ARP1 was used in the first clinical trial for anti-RVA VHHs, successfully reducing stool output in infants with RVA diarrhea, with no detected side effects.
Subject(s)
Diarrhea/drug therapy , Diarrhea/virology , Immunoglobulin Fragments/therapeutic use , Rotavirus Infections/drug therapy , Animals , Animals, Newborn , Bangladesh , Child , Diarrhea/prevention & control , Humans , Mice , Plants, Genetically Modified , Probiotics , Randomized Controlled Trials as Topic , Rotavirus Infections/prevention & control , SwineABSTRACT
Los rotavirus del grupo A (RVA) constituyen la principal causa de diarrea grave y mortalidad infantil. La porción variable de los anticuerpos de cadena pesada derivados de camélidos presentan una amplia capacidad de unión antigénica (reconocen sitios antigénicos no accesibles a los anticuerpos tradicionales, con elevada afinidad) tienen bajos costos de producción y resultan ideales para las terapias orales. A la fecha, se desarrollaron 2 pares de nanoanticuerpos VHH contra RVA: ARP1-ARP3 y 2KD1-3B2. En este trabajo, exploramos el potencial de ambos grupos de nanoanticuerpos como estrategias de prevención complementarias a la vacunación y como una opción de tratamiento frente a la diarrea asociada a RVA en poblaciones de riesgo. Ambos pares de nanoanticuerpos fueron expresados en diferentes sistemas de producción y mostraron amplia capacidad neutralizante contra diversas cepas de RVA in vitro. También fueron usados en el modelo de ratón lactante, en el que evidenciaron distintos grados de éxito en la prevención o el tratamiento de la diarrea inducida por RVA. Es interesante destacar que la mitigación de los síntomas también se logró con ARP1 liofilizado y conservado, por lo que podría ser utilizado en áreas donde es difícil mantener la cadena de frío. Asimismo, 3B2 fue testeado en una prueba preclínica utilizando como modelo al cerdo gnotobiótico, al cual confirió completa protección contra la diarrea inducida por RVA. ARP1 fue usado en la primera prueba clínica de nanoanticuerpos VHH contra RVA, donde redujo significativamente las deposiciones en pacientes pediátricos con diarrea positivos para RVA, sin evidenciar ninguna reacción adversa
Group A Rotavirus (RVA) remains a leading cause of severe diarrhea and child mortality. The variable domain of camelid heavy chain antibodies (VHH) display potent antigen-binding capacity, have low production costs and are suitable for oral therapies. Two sets of anti-RVA VHHs have been developed: ARP1-ARP3; 2KD1-3B2. Here, we explore the potential of both sets as a prevention strategy complementary to vaccination and a treatment option against RVA-associated diarrhea in endangered populations. Both sets have been expressed in multiple production systems, showing extensive neutralizing capacity against strains of RVA in vitro. They were also tested in the neonatal mouse model with various degrees of success in preventing or treating RVA-induced diarrhea. Interestingly, mitigation of the symptoms was also achieved with freeze-dried ARP1, so that it could be applied in areas where cold chains are difficult to maintain. 3B2 was tested in a pre-clinical trial involving gnotobiotic piglets where it conferred complete protection against RVA-induced diarrhea. ARP1 was used in the first clinical trial for anti-RVA VHHs, successfully reducing stool output in infants with RVA diarrhea, with no detected side effects
