Detection of malaria sporozoites expelled during mosquito sugar feeding

Brugman, Victor A.; Kristan, Mojca; Gibbins, Matthew P.; Angrisano, Fiona; Sala, Katarzyna; Dessens, Johannes T.; Blagborough, Andrew M.; Walker, Thomas

doi:10.1038/s41598-018-26010-6

Cited by 26 publications

(29 citation statements)

References 51 publications

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“…To our knowledge, this is the first study to evaluate the excretion and expectoration of P. falciparum in parallel with parasite development in the mosquito. Our results confirm previous findings that Plasmodium can be detected in mosquito excreta [28] and saliva deposited on filter paper cards after sugar feeding [24].…”

Section: Discussionsupporting

confidence: 92%

“…We were able to detect P. falciparum sporozoites deposited on filter paper cards after sugar feeding on days 15 to 19 PE. Our results expand the results from Brugman et al, who detected sporozoites on cotton wool pledgets from day 18 to 24 [24]. It is likely that the differences in C t values in saliva samples between cohorts are due to differences in sporozoite rates and not in sporozoite loads.…”

Section: Discussionsupporting

confidence: 88%

“…Mosquito saliva has been used for the study of other mosquito-borne diseases, particularly arthropod-borne viruses (arboviruses), both in the field and the laboratory [22, 23]. It had been demonstrated that P. falciparum could be detected in mosquito saliva collected by forced salivation [9], but it was not until recently that P. falciparum sporozoites were detected in saliva expectorated on honey-soaked nucleic acid preservation cards, allowing for detection without killing the mosquito [24]. Alternatively, mosquito excreta has emerged as a promising sample for the study of arboviruses [25–27], filarial parasites and malaria [28].…”

Section: Introductionmentioning

confidence: 99%

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Malaria surveillance from both ends: concurrent detection of Plasmodium falciparum in saliva and excreta harvested from Anopheles mosquitoes

et al. 2019

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Background Malaria is the most important vector-borne disease in the world. Epidemiological and ecological studies of malaria traditionally utilize detection of Plasmodium sporozoites in whole mosquitoes or salivary glands by microscopy or serological or molecular assays. However, these methods are labor-intensive, and can over- or underestimate mosquito transmission potential. To overcome these limitations, alternative sample types have been evaluated for the study of malaria. It was recently shown that Plasmodium could be detected in saliva expectorated on honey-soaked cards by Anopheles stephensi , providing a better estimate of transmission risk. We evaluated whether excretion of Plasmodium falciparum nucleic acid by An. stephensi correlates with expectoration of parasites in saliva, thus providing an additional sample type for estimating transmission potential. Mosquitoes were exposed to infectious blood meals containing cultured gametocytes, and excreta collected at different time points post-exposure. Saliva was collected on honey-soaked filter paper cards, and salivary glands were dissected and examined microscopically for sporozoites. Excreta and saliva samples were tested by real time polymerase chain reaction (RT-rtPCR). Results Plasmodium falciparum RNA was detected in mosquito excreta as early as four days after ingesting a bloodmeal containing gametocytes. Once sporogony (the development of sporozoites) occurred, P. falciparum RNA was detected concurrently in both excreta and saliva samples. In the majority of cases, no difference was observed between the C t values obtained from matched excreta and saliva samples, suggesting that both samples provide equally sensitive results. A positive association was observed between the molecular detection of the parasites in both samples and the proportion of mosquitoes with sporozoites in their salivary glands from each container. No distinguishable parasites were observed when excreta samples were stained and microscopically analyzed. Conclusions Mosquito saliva and excreta are easily collected and are promising for surveillance of malaria-causing parasites, especially in low transmission settings or in places where arboviruses co-circulate. Electronic supplementary material The online version of this article (10.1186/s13071-019-3610-9) contains supplementary material, which is available to authorized users.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

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Malaria surveillance from both ends: concurrent detection of Plasmodium falciparum in saliva and excreta harvested from Anopheles mosquitoes

et al. 2019

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“…After 45 min, the medium containing the saliva was placed in 1.5 ml Eppendorf tubes with 10 μl of MQ water 26 . We chose the isolation of saliva over other conventional methods such as the analysis of mosquito salivary glands because it allows the use of molecular methods for parasite detection and it has been widely used in studies on the competence of mosquitoes to transmit pathogens, such as West Nile virus 49 , Dengue virus 50 , Zika virus 51 , human malaria parasites 52 and avian malaria 26 . This method, however, required the mosquitoes to be alive, which implied stopping the monitoring of mosquito survival at 13 days post exposure.…”

Section: Methodsmentioning

confidence: 99%

Experimental reduction of host Plasmodium infection load affects mosquito survival

Gutiérrez‐López

Puente

Gangoso

et al. 2019

Sci Rep

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Plasmodium transmission success depends upon the trade-off between the use of host resources to favour parasite reproduction and the negative effects on host health, which can be mediated by infection intensity. Despite its potential influence on parasite dynamics, the effects of infection intensity on both, birds and vectors, and on Plasmodium transmission success are still poorly understood. Here, we experimentally reduced the Plasmodium load in naturally infected wild house sparrows with the antimalarial primaquine to assess the effects of intensity of infection in the vertebrate hosts on Plasmodium transmission to and by mosquitoes. We monitored the survival of Culex pipiens mosquitoes throughout the development of the parasite and the infection status of the mosquitoes by analysing the head-thorax and saliva at 13 days post-exposure to birds. The proportion of mosquitoes infected by Plasmodium and the presence of Plasmodium in saliva were not associated with the medication treatment of birds. However, the experimental treatment affected vector survival with mosquitoes fed on medicated birds showing a higher survival rate than those fed on control individuals. These results provide strong experimental evidence of the impact of parasite load of vertebrate hosts on the survival probability of malaria vectors.

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“…Another study observed no difference in the survivorship of wild caught A. gambiae mosquitoes due to malaria infection, yet P. falciparum detection did decline over time (49). So, it is possible that mosquito survivorship was not behind these observed declines and alternative explanations, such as sporozoite loss during sugar-feeding (50,51) or sporozoite mortality could require further investigation.…”

Section: Discussionmentioning

confidence: 98%

Estimating the extrinsic incubation period of malaria using a mechanistic model of sporogony

Stopard

Churcher

Lambert

2020

Preprint

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During sporogony, malaria-causing parasites infect a mosquito, reproduce and migrate to the mosquito salivary glands where they can be transmitted the next time blood-feeding occurs. The time required for sporogony, or extrinsic incubation period (EIP), is a crucial determinant of malaria transmission intensity. The EIP is typically estimated as the time for a given percentile of infected mosquitoes to have salivary gland sporozoites (the infectious parasite life stage). Many mechanisms, however, affect the observed sporozoite prevalence including the human-to-mosquito transmission probability and possibly differences in mosquito mortality according to infection status. To account for these various mechanisms, we present a mechanistic mathematical model (“mSOS”), which explicitly models key processes at the parasite, mosquito and observational scales. Fitting this model to experimental data, we find greater variation in EIP than previously thought: we estimated the range between two percentiles of the distribution, EIP10–EIP90 (at 27°C), as 4.5 days, compared to 0.9 days using existing methods. This pattern holds over the range of study temperatures included in the dataset. Increasing temperature from 21°C to 34°C decreased the EIP50 from 16.1 to 8.8 days and the human-to-mosquito transmission probability from 84% to 42%. Our work highlights the importance of mechanistic modelling of sporogony to (1) improve estimates of malaria transmission under different environmental conditions or disease control programs and (2) evaluate novel interventions that target the mosquito life stages of the parasite.Author summaryAnopheles mosquitoes become infected with malaria-causing parasites when blood feeding on an infectious human host. The parasites then process through a number of life stages, which begin in the mosquito gut and end in the salivary glands, where the newly formed infectious parasites can be transmitted to another host the next time a mosquito blood-feeds. The large variability in parasite numbers and development times that exists between mosquitoes, environments and parasites, mean that understanding parasite population dynamics from individual mosquito dissections is difficult. Here, we introduce a mathematical model of the mosquito life stages of parasites that mimics key characteristics of the biology. We show that the model’s parameters can be chosen so that its predictions correspond with experimental observations. In doing so, we estimate key system characteristics that are crucial determinants of malaria transmission intensity. Our work is a step towards a realistic model of within-mosquito parasite dynamics, which is increasingly important given that many recently proposed disease interventions specifically target mosquito life stages of the parasite.

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Detection of malaria sporozoites expelled during mosquito sugar feeding

Cited by 26 publications

References 51 publications

Malaria surveillance from both ends: concurrent detection of Plasmodium falciparum in saliva and excreta harvested from Anopheles mosquitoes

Malaria surveillance from both ends: concurrent detection of Plasmodium falciparum in saliva and excreta harvested from Anopheles mosquitoes

Experimental reduction of host Plasmodium infection load affects mosquito survival

Estimating the extrinsic incubation period of malaria using a mechanistic model of sporogony

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