scholarly journals Variation in tolerance to parasites in natural Asian tiger mosquito populations and its effect on vectorial capacity

2018 ◽  
Author(s):  
Guha Dharmarajan ◽  
Kathryne D. Walker ◽  
Tovi Lehmann
Keyword(s):  
Disease Transmission ◽  
Disease Risk ◽  
Negative Relationship ◽  
Parasite Load ◽  
Parasite Prevalence ◽  
Resistance Mechanisms ◽  
Vectorial Capacity ◽  
Transmission Intensity ◽  
Population Variation ◽  
High Transmission

AbstractThe vectorial capacity of mosquitoes depends upon the magnitude of reduction of parasite load upon infection through resistance mechanisms (e.g., immune-mediated killing) and the ability of mosquitoes to offset infection-mediated costs through tolerance mechanisms (e.g., tissue repair). Here we use a common-garden experimental framework to measure variation in resistance and tolerance to dog heartworm (Dirofilaria immitis) between natural Aedes albopictus mosquito populations representing areas of low and high transmission intensity. Our data revealed that survival to the extrinsic incubation period, the earliest time point at which infective L3 larvae develop, significantly differed between populations (ranging from 10-60%) when mosquitoes infected with D. immitis at both the low (15 microfilaria/μl blood) and high (30 microfilaria/μl blood) infection dose (Dose: χ2 = 191.473; P < 0.001; Population: χ2 = 24.485; P = 0.001; Dose × Population: χ2 = 35.566; P = 0.001). Contrary to expectations, we found that mosquito populations with highest resistance (i.e., greatest reduction in parasite load) also exhibited highest mortality upon infection (F1,12 = 6.781, P = 0.023; Dose: F1,12 = 6.747; P = 0.023; Mortality × Dose: F1,12 = 0.111, P = 0.744). Expressing the effect of the number of killed (NKILLED) and live (NLIVE) parasite on survival of mosquitoes from the different population, we document a significant inter-population variation in the survival cost of additional parasite (i.e., tolerance to infection (NLIVE × Population: χ2 = 22.845; P = 0.002; NKILLED × Population: χ2 = 31.959; P = < 0.001; NLIVE × NKILLED × Population: χ2 = 22.266; P = 0.002), in conjunction with negative relationship between tolerance and resistance (Resistance: F1,12 = 11.870, P = 0.005; Dose: F1,12 = 16.0170, P = 0.002; Resistance × Dose: F1,12 = 9.699, P =0.009). Importantly, populations from areas with high transmission intensity (as measured by parasite prevalence in dogs) showed elevated tolerance (Prevalence: F1,12 = 9.5, P = 0.012; Prevalence2: F1,12 = 4.353, P = 0.064; Dose: F1,12 = 38.855, P = <0.001), and these populations were also associated with increased vectorial capacity (Tolerance: F1,12 = 8.175, P = 0.014; Dose: F1,12 = 0.005, P = 0.946; Tolerance × Dose: F1,12 = 0.920, P = 0.356). Consequently, our data indicate that spatial variation in disease transmission intensity is linked to the evolution of tolerance in natural mosquito populations, which in turn can feedback to impact disease risk.

scholarly journals Mosquito diversity and dog heartworm prevalence in suburban areas

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Meredith R. Spence Beaulieu ◽  
Jennifer L. Federico ◽  
Michael H. Reiskind
Keyword(s):  
Disease Transmission ◽  
Disease Risk ◽  
Mosquito Species ◽  
Negative Relationship ◽  
Global Scale ◽  
Vector Borne Diseases ◽  
Suburban Areas ◽  
Host Seeking ◽  
Vector Borne ◽  
Wake County

Abstract Background Urbanization is occurring rapidly on a global scale and is altering mosquito communities, creating assemblages that are characteristically less diverse. Despite high rates of urbanization and ample examples of vector-borne diseases transmitted by multiple species, the effects of urbanization-driven mosquito diversity losses on disease transmission has not been well explored. We investigated this question using the dog heartworm, a filarial parasite vectored by numerous mosquito species. Methods We trapped host-seeking mosquitoes in undeveloped areas and neighborhoods of different ages in Wake County, North Carolina, USA, analyzing captured mosquitoes for heartworm DNA. We compared within-mosquito heartworm infection across land-use types by Kruskal–Wallis and likelihood ratio tests. Using zip code level data acquired from dogs in a local shelter, we performed linear regressions of within-host heartworm prevalence by within-mosquito heartworm prevalence as well as by three mosquito diversity measures. We also determined the best predictor of host-level prevalence among models including within-mosquito infection, mosquito diversity and abundance, and socioeconomic status as variables. Results Suburban areas had lower within-mosquito heartworm prevalence and lower likelihood of heartworm-positive mosquitoes than did undeveloped field sites, although no differences were seen between suburban and undeveloped wooded sites. No relationships were noted between within-mosquito and within-host heartworm prevalence. However, mosquito diversity metrics were positively correlated with host heartworm prevalence. Model selection revealed within-host prevalence was best predicted by a positive relationship with mosquito Shannon–Wiener diversity and a negative relationship with household income. Conclusions Our results demonstrate that decreases in mosquito diversity due to urbanization alter vector-borne disease risk. With regard to dog heartworm disease, this loss of mosquito diversity is associated with decreased heartworm prevalence within both the vector and the host. Although the response is likely different for diseases transmitted by one or few species, mosquito diversity losses leading to decreased transmission could be generalizable to other pathogens with multiple vectors. This study contributes to better understanding of the effects of urbanization and the role of vector diversity in multi-vectored pathosystems.

scholarly journals To Group or not to group: Group size dynamics and intestinal parasites in Indian peafowl populations

2020 ◽  
Author(s):  
Priyanka Dange ◽  
Pranav Mhaisalkar ◽  
Dhanashree Paranjpe
Keyword(s):  
Group Size ◽  
Group Dynamics ◽  
Disease Transmission ◽  
Intestinal Parasites ◽  
Monsoon Season ◽  
Parasite Load ◽  
Parasite Prevalence ◽  
Post Monsoon ◽  
Pavo Cristatus ◽  
Food Provision

AbstractAnimals can form groups for various reasons that include safety from predators, breeding and benefits of allo-parental care. However, there are also costs associated with living in a group such as competition for food and/or mates with other members of the group, higher chances of disease transmission, etc. In the current study we explored the links between group size dynamics and intestinal parasites of Indian Peafowl (Pavo cristatus) in the context of seasons and food provisioning. Data for group size was collected across three seasons- Pre-monsoon, Monsoon and Post-monsoon at three field sites- Morachi Chincholi, Nashik and Rajasthan. Individual and group sightings of peafowl were noted down along with group size and composition (no. of males, females, adults, juveniles, sub-adults). Faecal samples were collected from food provision and non-provision areas across three seasons- Pre-monsoon, Monsoon and Post-monsoon at same field sites. Parasite load in the samples was quantified using microscopic examination. Group size was significantly higher in Pre-Monsoon season as compared to Monsoon and Post-Monsoon seasons. While, monsoon and post-monsoon seasons had higher parasite prevalence and load as compared to pre-monsoon season. Interestingly, parasite load was significantly greater at food provision sites as compared to non-provision sites while parasite prevalence was comparable. Aggregation of individuals at the food provision sites may influence the parasite transmission and group dynamics in Indian Peafowl.

scholarly journals Domiciliary Cockroaches as Carriers of Human Intestinal Parasites in Lagos Metropolis, Southwest Nigeria: Implications for Public Health

2018 ◽  
pp. 141-151 ◽  
Author(s):  
Adedotun A Adenusi ◽  
Mary I Akinyemi ◽  
Dele Akinsanya
Keyword(s):  
Public Health ◽  
Disease Transmission ◽  
Periplaneta Americana ◽  
Intestinal Parasites ◽  
Low Cost ◽  
Parasite Prevalence ◽  
Strongyloides Stercoralis ◽  
Housing Type ◽  
Public Health Importance ◽  
Southwest Nigeria

Background: Domiciliary cockroaches are obnoxious pests of significant medical importance. We investigated the prevalence of human intestinal parasites in cockroaches and its attendant public health importance. Methods: Overall, 749 cockroaches (Periplaneta americana, 509, Blattella germanica, 240) caught by trapping from 120 households comprising 3 different housing types in Somolu, Lagos metropolis, southwest Nigeria, in 2015 were screened for human intestinal parasites using standard parasitological techniques. Results: The prevalence of human intestinal parasites in cockroaches was 96.4%. There was no statistically signifi­cant difference (P> 0.05) in parasite prevalences between P. americana (95.7%) and B. germanica (97.9%). Parasite species identified and their prevalence were as follows: Entamoeba histolytica/dispar (44.1%), E. coli (37.8%), Gi­ardia lamblia (18.7%), Cryptosporidium sp. (13.8%), Ascaris lumbricoides (61.3%), Trichuris trichiura (55.8%), hookworms (11.6%), Strongyloides stercoralis (11.7%), Taenia/Echinococcus spp. (10.5%), Enterobius vermicularis (17.2%) and Hymenolepis nana (11.6%). Parasite prevalence and burdens varied with housing type; the prevalence was significantly higher statistically (P< 0.05) in cockroaches from low-cost bungalow, LCB (100%) and low-cost, 2-storey, LC2-S (100%) houses than in medium-cost flats, MCF (81.3%). Parasite burdens were also significantly higher statistically (P< 0.05) in cockroaches from LCB or LC2-S than in cockroaches from MCF. Parasite preva­lences between cockroach gut and body surfaces were not statistically significant (P> 0.05) but mean parasite bur­dens in gut were significantly higher statistically (P< 0.05) than on body surfaces. Conclusion: Cockroaches types carry transmissive stages of human intestinal parasites and may act as reservoirs and potential mechanical vectors for disease transmission.

A Candide response to Panglossian accusations by Randolph and Dobson: biodiversity buffers disease

Parasitology ◽  
2013 ◽  
Vol 140 (10) ◽  
pp. 1196-1198 ◽  
Author(s):  
RICHARD S. OSTFELD
Keyword(s):  
Infectious Disease ◽  
Disease Risk ◽  
Negative Relationship ◽  
Dilution Effect ◽  
Widespread Phenomenon ◽  
High Diversity

SUMMARYRandolph and Dobson (2012) criticize the dilution effect, which describes the negative relationship between biodiversity and infectious disease risk. Unfortunately, their commentary includes distortions, errors of omission, and errors of commission, which are rebutted herein. Contrary to their claims, the dilution effect is not a ‘mantra’ that asserts that reduced disease risk is a ‘universal’ outcome of high diversity. Although universality of the dilution effect has not been claimed, and conditions under which diversity can amplify disease risk have been described, the growing literature indicates that the dilution effect is indeed a widespread phenomenon.

scholarly journals Impact of Transmission Intensity on the Accuracy of Genotyping To Distinguish Recrudescence from New Infection in Antimalarial Clinical Trials

2007 ◽  
Vol 51 (9) ◽  
pp. 3096-3103 ◽  
Author(s):  
Bryan Greenhouse ◽  
Christian Dokomajilar ◽  
Alan Hubbard ◽  
Philip J. Rosenthal ◽  
Grant Dorsey
Keyword(s):  
Clinical Trials ◽  
Treatment Failure ◽  
Transmission Intensity ◽  
High Transmission ◽  
Risk Of Treatment ◽  
Parasite Strains

ABSTRACT Antimalarial clinical trials use genotyping techniques to distinguish new infection from recrudescence. In areas of high transmission, the accuracy of genotyping may be compromised due to the high number of infecting parasite strains. We compared the accuracies of genotyping methods, using up to six genotyping markers, to assign outcomes for two large antimalarial trials performed in areas of Africa with different transmission intensities. We then estimated the probability of genotyping misclassification and its effect on trial results. At a moderate-transmission site, three genotyping markers were sufficient to generate accurate estimates of treatment failure. At a high-transmission site, even with six markers, estimates of treatment failure were 20% for amodiaquine plus artesunate and 17% for artemether-lumefantrine, regimens expected to be highly efficacious. Of the observed treatment failures for these two regimens, we estimated that at least 45% and 35%, respectively, were new infections misclassified as recrudescences. Increasing the number of genotyping markers improved the ability to distinguish new infection from recrudescence at a moderate-transmission site, but using six markers appeared inadequate at a high-transmission site. Genotyping-adjusted estimates of treatment failure from high-transmission sites may represent substantial overestimates of the true risk of treatment failure.

Detrimental effects of larval blow flies (Protocalliphora azurea) on nestlings and breeding success of Tree Sparrows (Passer montanus)

2004 ◽  
Vol 82 (8) ◽  
pp. 1285-1290 ◽  
Author(s):  
Peter Puchala
Keyword(s):  
Breeding Success ◽  
Negative Impact ◽  
Negative Relationship ◽  
Tail Length ◽  
Parasite Load ◽  
The Body ◽  
Blow Fly ◽  
Tree Sparrow ◽  
Passer Montanus ◽  
Negative Effect

The effect of bloodsucking parasitic larvae of the blow fly Protocalliphora azurea (Fallén, 1817) (Diptera) on Tree Sparrow, Passer montanus (L., 1758), breeding success was studied in populations breeding in nest boxes in southwestern Slovakia. Out of 52 examined nests only seven broods (13%) were unparasitized. The mean number of larvae per parasitized nest was 22.6 and the total number of parasites per nest ranged from 1 to 80. Large numbers of blow fly larvae and pupae significantly influenced nestling survival and fledging success. In broods with parasite load per chick higher than nine, at least one nestling died. To record the effects of parasites on the body size of nestlings of different ages, nestlings were measured on days 5, 10, and 13 post hatch. First and second broods were analysed separately. A significant negative effect of parasite load per nestling on the body mass, wing length, tarsal length, and tail length of nestlings was found in the second broods only in the 10- and 13-day-old chicks. Tree Sparrow parents did not prolong nestling provisioning time per nestling, as there was no negative relationship between parasite load per nestling and feeding period. Contradictory to most previous studies of the genus Protocalliphora, the present study suggests that these parasites have an important negative impact on the breeding success of the studied Tree Sparrow populations.

The weight/length profiles of Ascaris lumbricoides within a human community before mass treatment and following reinfection

Parasitology ◽  
1989 ◽  
Vol 99 (2) ◽  
pp. 293-299 ◽  
Author(s):  
D. B. Elkins ◽  
M. Haswell-Elkins
Keyword(s):  
Initial Treatment ◽  
Acquired Resistance ◽  
Negative Relationship ◽  
Resistance Mechanisms ◽  
Positive Influence ◽  
Primary Role ◽  
Distribution Profile ◽  
Human Community ◽  
Age Related ◽  
Multiple Regression Models

SummaryWeight and length profiles are presented of 3505 Ascaris worms recovered after mass anthelmintic treatment of a human community in January 1984 and, after an 11 month period of reinfection, in November 1984. Male and female worms recovered after reinfection were significantly heavier and longer than those expelled after initial treatment (P < 0·0001). Multiple regression models were employed to examine variability in parasite size. A positive influence of host body weight on the weight of parasites recovered in January, but not in November, was observed. No negative relationship was recorded at either date between worm size and the total number of worms harboured, even after controlling for host weight. Striking host age-related variability was observed in the distribution profile of weights and lengths of individual worms recovered in January. Children harboured predominantly smaller worms before initial treatment, while adults expelled mainly heavy worms. In contrast, worms expelled by both children and adults after reinfection were heavier and more homogeneous in size, particularly within the relatively heavily infected group. These patterns argue against a primary role for density- dependent or acquired resistance mechanisms in determining the size of Ascaris in humans. However, the results are consistent with a hypothesis initially suggested by Jung (1954) that established worms may inhibit the development of newly acquired Ascaris larvae, perhaps regulating their own abundance.

Morpho-phenological diversity among Tunisian natural populations of Brachypodium hybridum

2014 ◽  
Vol 153 (6) ◽  
pp. 1006-1016 ◽  
Author(s):  
M. NEJI ◽  
F. GEUNA ◽  
W. TAAMALLI ◽  
Y. IBRAHIM ◽  
M. SMIDA ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Geographic Distribution ◽  
Phenotypic Diversity ◽  
Average Length ◽  
Natural Populations ◽  
Negative Relationship ◽  
Mantel Test ◽  
Population Variation ◽  
Long Distance ◽  
Temperate Cereal

SUMMARYBrachypodium hybridum belongs to the Poaceae grass subfamily. It has a close genetic relationship with temperate cereal crops, which means that it can be used as a model for temperate cereal and grass crops. In order to improve knowledge on the genetic diversity of this species, 145 lines of B. hybridum representative of nine populations and all the ecoregions of Tunisia were characterized on the basis of 18 morpho-phenologic features. The results show a considerable variation between populations and ecoregions in all traits studied. Variation was relatively higher for reproductive than vegetative traits. The majority of traits showed very low to high heritability with low border value for average length of spikelet (ALS) and an average value of 0·64. It is noticeable that high values of heritability were observed for most vegetative descriptors, with low values for reproductive ones. Differentiation between populations (QST) varied from 0·02 for ALS to 0·78 for average length of leaves with a mean value across traits of 0·4, which confirms the wide intra-population variation in Tunisian natural population of B. hybridum. Pairwise QST showed that the greatest differentiation among populations was registered between Ain Drahem and Jbel Zaghouan and the smallest between Haouria and Raoued. Overall, the Ain Draham population showed the largest differentiation from the rest of the populations. To infer the effect of geographic distribution of the species, a Mantel test was applied between observed pairwise differentiation and geographic distance between populations and between ecoregions: the results show a positive, but not significant, relationship. In addition a significant negative relationship was found between phenotypic diversity and altitude, indicating that genetic diversity decreased with increasing altitude. Taken together, the high levels of intra-population variation and the lack of correlation between genetic differentiation and geographic distribution suggest a potentially important rate of long-distance seed dispersal and confirm the role played by natural selection in the population structure of Tunisian natural populations of B. hybridum.

scholarly journals Direct evidence for increased disease resistance in polyandrous broods exists only in eusocial Hymenoptera

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
D. M. Soper ◽  
A. K. E. Ekroth ◽  
M. J. F. Martins
Keyword(s):  
Genetic Diversity ◽  
Disease Resistance ◽  
Literature Review ◽  
Publication Bias ◽  
Direct Evidence ◽  
Parasite Load ◽  
Parasite Prevalence ◽  
Future Research ◽  
High Dispersal ◽  
Meta Analyses

Abstract Background The ‘genetic diversity’ hypothesis posits that polyandry evolved as a mechanism to increase genetic diversity within broods. One extension of this hypothesis is the ‘genetic diversity for disease resistance’ hypothesis (GDDRH). Originally designed for eusocial Hymenoptera, GDDRH states that polyandry will evolve as an effect of lower parasite prevalence in genetically variable broods. However, this hypothesis has been broadly applied to several other taxa. It is unclear how much empirical evidence supports GDDRH specifically, especially outside eusocial Hymenoptera. Results This question was addressed by conducting a literature review and posteriorly conducting meta-analyses on the data available using Hedges’s g. The literature review found 10 direct and 32 indirect studies with both having a strong publication bias towards Hymenoptera. Two meta-analyses were conducted and both found increased polyandry (direct tests; n = 8, g = 0.2283, p =  < 0.0001) and genetic diversity generated by other mechanisms (indirect tests; n = 10, g = 0.21, p =  < 0.0001) reduced parasite load. A subsequent moderator analysis revealed that there were no differences among Orders, indicating there may be applicability outside of Hymenoptera. However, due to publication bias and low sample size we must exercise caution with these results. Conclusion Despite the fact that the GDDRH was developed for Hymenoptera, it is frequently applied to other taxa. This study highlights the low amount of direct evidence supporting GDDRH, particularly outside of eusocial Hymenoptera. It calls for future research to address species that have high dispersal rates and contain mixes of solitary and communal nesting.

scholarly journals Heterogeneity in response to serological exposure markers of recent Plasmodium vivax infections

2020 ◽  
Author(s):  
Jason Rosado ◽  
Michael T. White ◽  
Rhea J. Longley ◽  
Wuelton Monteiro ◽  
Marcus Lacerda ◽  
...  
Keyword(s):  
Plasmodium Vivax ◽  
Malaria Elimination ◽  
Antibody Responses ◽  
Blood Stage ◽  
Transmission Intensity ◽  
Low Transmission ◽  
Recent Exposure ◽  
High Transmission ◽  
Antibody Titers

AbstractBackgroundAntibody responses to serological markers of Plasmodium vivax infection have been shown to correlate with exposure, but little is known about the other factors which affect antibody responses in naturally infected people from endemic settings. To address this question, we studied IgG responses to novel serological exposure markers (SEMs) of P. vivax in three settings with different transmission intensity.MethodologyWe validated a panel of 34 SEMs in a Peruvian cohort with up to three years’ longitudinal follow-up using the Luminex® platform and compared results to data from cohorts in Thailand and Brazil. Linear regression models were used to characterize the association between antibody responses and age, the number of detected blood-stage infections during follow-up, and time since the last infection. Receiver Operating Characteristic (ROC) analysis was used to test the performance of SEMs to identify P. vivax infections in the last 9 months.Principal findingsAntibody titers were associated with age, the number of blood-stage infections, and time since last P. vivax infection in all three study sites. The association between antibody titers and time since last P. vivax infection was stronger in the low transmission settings of Thailand and Brazil compared to the high transmission setting in Peru. Of the SEMs tested, antibody responses to RBP2b had the highest performance of classifying recent exposure in all sites, with area under the ROC curve (AUC) = 0.83 in Thailand, AUC = 0.79 in Brazil, and AUC = 0.68 in Peru.ConclusionsIn low transmission settings, P. vivax SEMs can accurately identify individuals with recent blood-stage infections. In high transmission settings, the accuracy of this approach diminishes substantially. We recommend the application of P. vivax SEMs for use in low transmission settings pursuing malaria elimination, but they appear less useful in high transmission settings focused on malaria control.Author SummaryPlasmodium vivax still poses a threat in many countries due to its ability to cause recurrent infections. Key to achieving the goal of malaria elimination is the ability to quickly detect and treat carriers of relapsing parasites. Failing to identify this transmission reservoir will hinder progress towards malaria elimination. Recently, novel serological markers of recent exposure to P. vivax (SEM) have been developed and validated in low transmission settings. It is still poorly understood what factors affect the antibody response to these markers when evaluated in contrasting endemic contexts. To determine the factors that influence the antibody response to SEM, we compare the antibody levels in three sites with different transmission intensity: Thailand (low), Brazil (moderate) and Peru (high). In this study, we found that transmission intensity plays a key role in the acquisition of the antibody repertoire to P. vivax. In highly endemic sites, the immunological memory resulting from a constant and sustained exposure will impact the performance of SEMs to detect individuals with recent exposure to P. vivax. In summary, SEMs that perform well in low transmission sites do not perform as well in high transmission regions.

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