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R. H. Wharton

Bio: R. H. Wharton is an academic researcher from Peninsular Malaysia. The author has contributed to research in topics: Filariasis & Malaria. The author has an hindex of 15, co-authored 27 publications receiving 636 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the efficiency of Mansonia Longipalpis as an experimental vector of Wuchereria Malayi was investigated in the context of Filariasis in Malaya.
Abstract: (1957). Studies on Filariasis in Malaya: The Efficiency of Mansonia Longipalpis as an Experimental Vector of Wuchereria Malayi. Annals of Tropical Medicine & Parasitology: Vol. 51, No. 4, pp. 422-439.

45 citations

Journal ArticleDOI
TL;DR: Feeding experiments with a wide range of mosquitoes showed that Armigeres obturbans is a very efficient host and Mansonia annulatus is also a good host but M. uniformis is less efficient and M. longipalpis is a comparatively poor laboratory host.
Abstract: 1. 1) Brugia pahangi occurs naturally in the domestic cat and dog and in several species of forest animals in areas where B. malayi is endemic. 2. 2) Attempts were made to transmit B. pahangi by the direct inoculation of infective larvae to domestic cats, slow loris, macaque monkeys, civet cats, squirrels, tree-shrews and guinea-pigs. Cats, slow loris and civet cats were successfully infected, but no monkeys became infected. 3. 3) The prepatent period in cats varied from 59–83 days. Microfilaria counts rose to high levels and have been maintained for more than 2 1 2 years. 4. 4) The rate of development in the vertebrate host was followed. 5. 5) Feeding experiments with a wide range of mosquitoes showed that Armigeres obturbans is a very efficient host. Mansonia annulatus is also a good host but M. uniformis is less efficient and M. longipalpis is a comparatively poor laboratory host. M. (C.) crassipes, Anopheles barbirostris, A. umbrosus and small numbers of Aedes aegypti and Culex fatigans also supported development to the infective stage. 6. 6) M. longipalpis and M. annulatus were proved to be vectors in nature.

40 citations

Journal Article
TL;DR: It was concluded that A. balabacensis probably was the vector of both human and monkey malaria and that the risk of cross-infection was considerable if monkey malarias infective to man exist in the area.
Abstract: During the past few years Anopheles balabacensis has come to be recognized as a very important human malaria vector in Thailand and the Indochinese area, but little has been published on its bionomics except from North Borneo.Studies of the feeding habits of A. balabacensis in Cambodia showed it to be predominantly a forest mosquito. It was readily attracted to monkeys in the forest canopy but also readily attacked man on the ground. Very few of this species were attracted to domestic animals. Malaria infections were found more frequently in mosquitos captured in villages, but a significant number were infected from the forest beyond flight range of human habitation.The human population showed a high percentage of persons infected with malaria, Plasmodium falciparum predominating. Cambodian monkeys were found also to be infected with P. cynomolgi. Although none of thirteen monkeys injected with sporozoites from wild-caught mosquitos came down with malaria, it was concluded that A. balabacensis probably was the vector of both human and monkey malaria and that the risk of cross-infection was considerable if monkey malarias infective to man exist in the area.

34 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the small subunit ribosomal RNA and the circumsporozoite protein genes were sequenced for eight isolates that had been microscopically identified as P knowlesi by microscopy.

1,100 citations

Book
16 May 1991
TL;DR: This chapter discusses the evolution of the blood-sucking habit, feeding preferences, host-insect interactions, and the transmission of parasites by blood-Sucking insects.
Abstract: Part 1 The importance of blood-sucking insects. Part 2 The evolution of the blood-sucking habit: prolonged close association with vertebrates morphological pre-adaptation for piercing. Part 3 Feeding preferences of blood-sucking insects: host choice host choice and species complexes. Part 4 Location of the host: the behavioural framework of host location appetitive searching activation and orientation attraction movement between hosts. Part 5 Ingestion of the blood meal: vertebrate haemostasis insect anti-haemostatic factors probing stimulants phagostimulants mouthparts blood intake. Part 6 Managing the blood meal: midgut anatomy the blood meal gonotrophic concordance nutrition host hormones in the blood meal partitioning of resources from the blood meal autogeny. Part 7 Host - insect interactions: insect distribution on the surface of the host morphological specializations for life on the host host immune responses to insect salivary secretions behavioural defences of the host density dependent effects on feeding success. Part 8 Transmission of parasites by blood-sucking insects: transmission routes specificity in vector-parasite relationships origin of vector parasite relationships.

772 citations

Journal ArticleDOI
TL;DR: The impact of IRS alone, and to compare the relative impacts of IRS and ITNs, on key malariological parameters is quantified to help compare IRS with other vector control interventions.
Abstract: BACKGROUND: Primary malaria prevention on a large scale depends on two vector control interventions: indoor residual spraying (IRS) and insecticide-treated mosquito nets (ITNs). Historically, IRS has reduced malaria transmission in many settings in the world, but the health effects of IRS have never been properly quantified. This is important, and will help compare IRS with other vector control interventions. OBJECTIVES: To quantify the impact of IRS alone, and to compare the relative impacts of IRS and ITNs, on key malariological parameters. SEARCH STRATEGY: We searched the Cochrane Infectious Diseases Group Specialized Register (September 2009), CENTRAL (The Cochrane Library 2009, Issue 3), MEDLINE (1966 to September 2009), EMBASE (1974 to September 2009), LILACS (1982 to September 2009), mRCT (September 2009), reference lists, and conference abstracts. We also contacted researchers in the field, organizations, and manufacturers of insecticides (June 2007). SELECTION CRITERIA: Cluster randomized controlled trials (RCTs), controlled before-and-after studies (CBA) and interrupted time series (ITS) of IRS compared to no IRS or ITNs. Studies examining the impact of IRS on special groups not representative of the general population, or using insecticides and dosages not recommended by the World Health Organization (WHO) were excluded. DATA COLLECTION AND ANALYSIS: Two authors independently reviewed trials for inclusion. Two authors extracted data, assessed risk of bias and analysed the data. Where possible, we adjusted confidence intervals (CIs) for clustering. Studies were grouped into those comparing IRS with no IRS, and IRS compared with ITNs, and then stratified by malaria endemicity. MAIN RESULTS: IRS versus no IRSStable malaria (entomological inoculation rate (EIR) 1): Two studies; for incidence and prevalence, the malaria rates were higher in the IRS group compared to the ITN group in one study. Malaria incidence was higher in the IRS arm in India (risk ratio IRS:ITN = 1.48) and in South Africa (risk ratio 1.34 but the cluster unadjusted CIs included 1). For malaria prevalence, ITNs appeared to give better protection against any infection compared to IRS in India (risk ratio IRS:ITN = 1.70) and also for both P. falciparum (risk ratio IRS:ITN = 1.78) and P. vivax (risk ratio IRS:ITN = 1.37). AUTHORS' CONCLUSIONS: Historical and programme documentation has clearly established the impact of IRS. However, the number of high-quality trials are too few to quantify the size of effect in different transmission settings. The evidence from randomized comparisons of IRS versus no IRS confirms that IRS reduces malaria incidence in unstable malaria settings, but randomized trial data from stable malaria settings is very limited. Some limited data suggest that ITN give better protection than IRS in unstable areas, but more trials are needed to compare the effects of ITNs with IRS, as well as to quantify their combined effects

439 citations

Journal ArticleDOI
TL;DR: Current knowledge about eosinophils and their role, both protective and pathogenetic, in parasitic helminth infections is provided.
Abstract: The precise function of eosinophils in parasitic infection in vivo remains poorly understood despite eosinophils having been shown to be potent effectors in killing parasites in vitro. Although it has long been held that the primary function of the eosinophil is protection against helminth parasites, there are little data to prove this unequivocally. Moreover, eosinophils are responsible for a considerable amount of inflammatory pathology accompanying helminth infections. This article will provide an overview of our current knowledge about eosinophils and their role, both protective and pathogenetic, in parasitic helminth infections.

409 citations

Journal ArticleDOI
TL;DR: It is stressed that the best way to avoid emergent and reemergent diseases is through a program encompassing ecological restoration, environmental education, and enhanced understanding of the value of ecosystem services.
Abstract: Haemosporida is a large group of vector-borne intracellular parasites that infect amphibians, reptiles, birds, and mammals. This group includes the different malaria parasites (Plasmodium spp.) that infect humans around the world. Our knowledge on the full life cycle of these parasites is most complete for those parasites that infect humans and, to some extent, birds. However, our current knowledge on haemosporidian life cycles is characterized by a paucity of information concerning the vector species responsible for their transmission among vertebrates. Moreover, our taxonomic and systematic knowledge of haemosporidians is far from complete, in particular because of insufficient sampling in wild vertebrates and in tropical regions. Detailed experimental studies to identify avian haemosporidian vectors are uncommon, with only a few published during the last 25 years. As such, little knowledge has accumulated on haemosporidian life cycles during the last three decades, hindering progress in ecology, evolution, and systematic studies of these avian parasites. Nonetheless, recently developed molecular tools have facilitated advances in haemosporidian research. DNA can now be extracted from vectors' blood meals and the vertebrate host identified; if the blood meal is infected by haemosporidians, the parasite's genetic lineage can also be identified. While this molecular tool should help to identify putative vector species, detailed experimental studies on vector competence are still needed. Furthermore, molecular tools have helped to refine our knowledge on Haemosporida taxonomy and systematics. Herein we review studies conducted on Diptera vectors transmitting avian haemosporidians from the late 1800s to the present. We also review work on Haemosporida taxonomy and systematics since the first application of molecular techniques and provide recommendations and suggest future research directions. Because human encroachment on natural environments brings human populations into contact with novel parasite sources, we stress that the best way to avoid emergent and reemergent diseases is through a program encompassing ecological restoration, environmental education, and enhanced understanding of the value of ecosystem services.

279 citations