Raman Velayudhan - Academia.edu (original) (raw)

Papers by Raman Velayudhan

The Journal of communicable diseases, 1990

Carbosulfan (OMS 3022), a carbamate and pyraclofos (OMS 3040), an organophosphate were evaluated ... more Carbosulfan (OMS 3022), a carbamate and pyraclofos (OMS 3040), an organophosphate were evaluated for their biological activity against vector mosquitoes, both in laboratory and field conditions. Carbosulfan (25% EC), was found to be active against adults and immatures of Culex quinquefasciatus, Anopheles stephensi and Aedes aegypti. The LD values for adults were 6.65, 5.19 and 8.35 micrograms/cm2 and LC 50values for immatures were 5.4 X 10(-5), 1.6 X 10(-4 and 5.4) X 10(-4) 50mg/1 respectively. Pyraclofos (50%) showed neither larvicidal nor adulticidal activities. The residual effect of carbosulfan (25% WP) on cement, thatch and mud surfaces at 400 mg (ai)/m2 lasted for 3, 16 and 21 weeks respectively. In the field, carbosulfan at 2.00 kg (ai)/ha resulted in complete control of C. quinquefasciatus larvae for a period of one week in cement tanks and less than a week in other polluted water bodies, such as cesspits, cesspools and drains. Pyraclofos was not effective at a dose of 2.00 ...

Background: The continued spread of insecticide resistance in mosquito vectors of malaria and arb... more Background: The continued spread of insecticide resistance in mosquito vectors of malaria and arboviral diseases may lead to operational failure of insecticide-based interventions if resistance is not monitored and managed efficiently. This study aimed to develop and validate a new WHO glass bottle bioassay method as an alternative to the WHO standard insecticide tube test to monitor mosquito susceptibility to new public health insecticides with particular modes of action, physical properties or both.Methods: A multi-centre study involving 21 laboratories worldwide generated data on the susceptibility of seven mosquito species (i.e. Aedes aegypti, Ae. albopictus, Anopheles gambiae s.s., An. funestus, An. stephensi, An. minimus and An. albimanus) to seven public health insecticides in five classes, including pyrethroids (metofluthrin, prallethrin, and transfluthrin), neonicotinoids (clothianidin), pyrroles (chlorfenapyr), juvenile hormone mimics (pyriproxyfen) and butenolides (flupyr...

Proceedings: Animal Sciences, 1986

The vector role of thrips in pollinating several fabaceous flowers has been studied. The flowerin... more The vector role of thrips in pollinating several fabaceous flowers has been studied. The flowering phenology showed a coincidence with the life cycle of the thrips species. The population dynamics of the thrips, crop-weed dispersal, the pollen carrying efficiency and the percentage of pod set are discussed.

Additional file 2. STROBE Statement

Details of: selection of major vector-borne diseases and vector control interventions for evaluat... more Details of: selection of major vector-borne diseases and vector control interventions for evaluation, compilation of risk maps for these diseases, and calculation of joint population at risk estimates. (DOCX 2809Â kb)

Includes all the dengue data used in the paper "The current and future global distribution a... more Includes all the dengue data used in the paper "The current and future global distribution and population at risk of dengue, 2019 Nature Microbiology: https://doi.org/10.1038/s41564-019-0476-8" which provides further information on its generation and use in mapping the current and future global distribution of dengue. Three datasets are included: 1. Dengue occurence point dataset: "points_standard_checkedEC.csv" which contains precise point locations where dengue has occurrence in the past 2. Dengue occurrence polygon dataset: "poly_standard_checkedEC.csv" which contains small administrative units in within which dengue has occurred in the past 3. Other disease background points:"dengue_background_full.csv" which contains point locations where other non-dengue infectious diseases have occurred in the past The fillets have a number of common field names including:unique IDcalendar...

Scientific Reports, 2021

Insecticides have played a major role in the prevention, control, and elimination of vector-borne... more Insecticides have played a major role in the prevention, control, and elimination of vector-borne diseases, but insecticide resistance threatens the efficacy of available vector control tools. A global survey was conducted to investigate vector control insecticide use from 2010 to 2019. Out of 140 countries selected as sample for the study, 87 countries responded. Also, data on ex-factory deliveries of insecticide-treated nets (ITNs) were analyzed. Insecticide operational use was highest for control of malaria, followed by dengue, leishmaniasis and Chagas disease. Vector control relied on few insecticide classes with pyrethroids the most used overall. Results indicated that IRS programs have been slow to react to detection of pyrethroid resistance, while proactive resistance management using insecticides with unrelated modes of action was generally weak. The intensive use of recently introduced insecticide products raised concern about product stewardship regarding the preservation ...

Tropical Medicine & International Health, 2013

objective To systematically review the literature on the effectiveness of Bacillus thuringiensis ... more objective To systematically review the literature on the effectiveness of Bacillus thuringiensis israelensis (Bti), when used as a single agent in the field, for the control of dengue vectors. method Systematic literature search of the published and grey literature was carried out using the following databases: MEDLINE, EMBASE, Global Health, Web of Science, the Cochrane Library, WHOLIS, ELDIS, the New York Academy of Medicine Gray Literature Report, Africa-Wide and Google. All results were screened for duplicates and assessed for eligibility. Relevant data were extracted, and a quality assessment was conducted using the CONSORT 2010 checklist. results Fourteen studies satisfied the eligibility criteria, incorporating a wide range of interventions and outcome measures. Six studies were classified as effectiveness studies, and the remaining eight examined the efficacy of Bti in more controlled settings. Twelve (all eight efficacy studies and 4 of 6 effectiveness studies) reported reductions in entomological indices with an average duration of control of 2-4 weeks. The two effectiveness studies that did not report significant entomological reductions were both cluster-randomised study designs that utilised basic interventions such as environmental management or general education on environment control practices in their respective control groups. Only one study described a reduction in entomological indices together with epidemiological data, reporting one dengue case in the treated area compared to 15 dengue cases in the untreated area during the observed study period. conclusion While Bti can be effective in reducing the number of immature Aedes in treated containers in the short term, there is very limited evidence that dengue morbidity can be reduced through the use of Bti alone. There is currently insufficient evidence to recommend the use of Bti as a single agent for the long-term control of dengue vectors and prevention of dengue fever. Further studies examining the role of Bti in combination with other strategies to control dengue vectors are warranted.

International Journal of Environmental Health Research, 2004

This paper describes a study undertaken to: (1) determine the prevalence of Ascaris lumbricoides,... more This paper describes a study undertaken to: (1) determine the prevalence of Ascaris lumbricoides, Trichuris trichiura and hookworm infections and nutritional status among Pacific Island school children; (2) identify factors influencing helminthiasis; (3) identify interventions to improve school health. A total of 3,683 children aged 5-12 years attending 27 primary schools in 13 Pacific Island countries were surveyed along with school environmental data. Stool samples were collected from 1996 children (54.2%) and analysed for ova and helminths. Total prevalence of helminthiasis was 32.8%. Anaemia prevalence was 12.4%. Children with helminthiasis and anaemia were found to be 8.7 times more likely to be stunted and 4.3 times more likely to be underweight than non-anaemic and non-infected children. Four significant environmental influences on helminthiasis were identified: (1) an inadequate water supply; (2); availability of a school canteen; (3) regular water/sanitation maintenance regimes; and (4) overcrowded classrooms. Helminthiasis was found to be strongly associated with anaemia, stunting and underweight and environmental influences identified. Although mass anti-helminthic drug administrations (MDA) have been taking place, reinfection is common as drug therapy alone is not enough. Programme effectiveness depends upon upgrading school environments to include an adequate water supply, controlled food preparation/provision, well-maintained water/sanitation facilities and class sizes of 30 students or less.

The Lancet Infectious Diseases

Additional file 1. Topics of the analysis with corresponding survey questions

The American Journal of Tropical Medicine and Hygiene

The incidence of malaria in Solomon Islands has been decreasing since 1992. The control program u... more The incidence of malaria in Solomon Islands has been decreasing since 1992. The control program used a combination of methods including DDT residual house spraying and insecticide-treated mosquito nets. To determine how much each method contributed to malaria control, data were analyzed on monthly incidence and on control activities for 41 of 110 malaria zones over the same time period (January 1993 to August 1999). After correction for endogeneity, then spraying, insecticide treatment of nets, and education about malaria are all independently associated with reduction in incident cases of malaria or fever, while larviciding with temephos is not. The evidence suggests that although impregnated bed nets cannot entirely replace DDT spraying without substantial increase in incidence, their use permits reduced DDT spraying. The paper shows that non-experimental data can be used to infer causal links in epidemiology, provided that instrumental variables are available to correct for endogeneity.

Policy Research Working Papers, 2003

The incidence of malaria in Solomon Islands has been applied by month and zone, while adjusting f... more The incidence of malaria in Solomon Islands has been applied by month and zone, while adjusting for rainfall declining since 1992, but there is a large geographical and proximity to water. The results showed that DDT variation between areas in the incidence level and the house spraying, insecticide treatment of nets, and rate of decline. The authors used a mix of control education about malaria were all independently interventions, including DDT residual house spraying associated with reduction in incident cases of and insecticide-treated mosquito nets. Data on monthly malaria or fever, while larviciding with temephos was incidence and control activities performed from January not. This was true for confirmed malaria cases even 1993 to August 1999 were gathered for 41 out of the when a variable representing the passage of time was 110 malaria zones in the country. Monthly reports on included in the models. The results show how much each the number of fevers seen at outpatient health clinics in method used was contributing to malaria control in the same zones over the same period were also extracted Solomon Islands and how it can be used to design the from the clinical health information system. The authors most cost-effective package of interventions. The used multivariate random effects regression, including evidence suggests that impregnated bednets cannot easily calendar month as an instrumental variable, to replace DDT spraying without substantial increase in investigate the relationship between the number of incidence, but impregnated nets do permit a substantial malaria or fever cases and the control measures reduction in the amount of DDT spraying.

Parasitology International, 2008

The first two phases of a national prevalence survey of schistosomiasis in The Philippines were c... more The first two phases of a national prevalence survey of schistosomiasis in The Philippines were completed in Mindanao in 2005 and the Visayas in the first quarter of 2007. The design was a stratified two-step systematic cluster sampling, with two Kato-Katz thick smears examined from each participant. In Mindanao, a total of 22 provinces spread in six regions were covered by the survey with five barangays (equivalent to a village) per province for a total of 110 barangays. The response rate was 70.9% with a total of 21,390 individuals examined. The province of Maguindanao, a known endemic area for schistosomiasis japonica, failed to take part in the survey. In the Visayas, 10 out of 11 provinces, spread out in three regions, participated in the survey. There were 6321 respondents for an overall participation rate of 32.2%. Mindanao showed a wider coverage of the disease than the Visayas (60% versus 45%). By region, Caraga or Region 13 ranked first in Mindanao and Region 8 in the Visayas. By province, Agusan del Sur is first on the list, followed by Northern Samar and then Eastern Samar. Overall, the prevalence rate among males is higher than that of females suggesting the occupational hazard of farming and fishing among the males. The higher exposure among farmers and fishermen is also borne out by the age distribution of the disease. Prevalence remains consistently high among the adults compared with the younger age groups. The survey also covered other helminth infections that can be detected in a stool survey, notably soil-transmitted helminthes and food-borne trematodes.

PLoS Neglected Tropical Diseases, 2008

Acta Tropica, 2013

Schistosomiasis affects 28 provinces in the Philippines found along the southeastern part where t... more Schistosomiasis affects 28 provinces in the Philippines found along the southeastern part where there is continuous rainfall throughout the year. In 2002 and 2005 respectively, two new endemic foci were reported in the northernmost (Gonzaga, Cagayan) and central (Calatrava, Negros Occidental) parts of the country. This study conducted in March 2008-March 2009 confirmed the presence of the disease by determining its prevalence using four diagnostic tests-Kato-Katz, circum-oval precipitin test (COPT), ELISA and ultrasonography. Oncomelania hupensis quadrasi was identified through snail surveys conducted in possible snail habitats in the seven new endemic villages. Animal surveys through stool examination confirmed the presence of schistosomiasis infection in animals in Gonzaga but not in Calatrava. Compared to Calatrava, Gonzaga demonstrated markedly higher prevalence of schistosomiasis using all four diagnostic methods. Proximity of snail habitats to human habitation including higher snail density and snail infection rate could be responsible for the high prevalence. Snail sites were more widespread in Gonzaga whereas those in Calatrava were confined only in areas not frequented by the general population except by farmers. GIS maps showing spatial distribution of snails in Gonzaga and Calatrava indicated differences in elevation among the snail sites. It is hypothesized that the snail intermediate host has been in these sites for sometime but discovered only lately. Migration of people from endemic provinces into Gonzaga and Calatrava brought in cases and in the presence of snail intermediate hosts, emergence of disease was just a matter of time.

Abstract: In 2001, Urbani and Palmer published a review of the epidemiological situation of helmi... more Abstract: In 2001, Urbani and Palmer published a review of the epidemiological situation of helminthiases in the countries of the Western Pacific Region of the World Health Organization indicating the control needs in the region. Six years after this inspiring article, large-scale preventive chemotherapy for the control of helminthiasis has scaled up dramatically in the region. This paper analyzes the most recent published and unpublished country information on large-scale preventive chemotherapy and summarizes the progress made since 2000. Almost 39 million treatments were provided in 2006 in the region for the control of helminthiasis: nearly 14 million for the control of lymphatic filariasis, more than 22 million for the control of soil-transmitted helminthiasis, and over 2 million for the control of schistosomiasis. In general, control of these helminthiases is progressing well in the Mekong countries and Pacific Islands. In China, despite harboring the majority of the helminth ...

Background: Vector-borne diseases cause a significant proportion of the overall burden of disease... more Background: Vector-borne diseases cause a significant proportion of the overall burden of disease across the globe, accounting for over 10 % of the burden of infectious diseases. Despite the availability of effective interventions for many of these diseases, a lack of resources prevents their effective control. Many existing vector control interventions are known to be effective against multiple diseases, so combining vector control programmes to simultaneously tackle several diseases could offer more cost-effective and therefore sustainable disease reductions. Discussion: The highly successful cross-disease integration of vaccine and mass drug administration programmes in low-resource settings acts a precedent for cross-disease vector control. Whilst deliberate implementation of vector control programmes across multiple diseases has yet to be trialled on a large scale, a number of examples of ‘accidental ’ cross-disease vector control suggest the potential of such an approach. Comb...

BMC Infectious Diseases, 2021

Background Vector control plays a critical role in the prevention, control and elimination of vec... more Background Vector control plays a critical role in the prevention, control and elimination of vector-borne diseases, and interventions of vector control continue to depend largely on the action of chemical insecticides. A global survey was conducted on the management practices of vector control insecticides at country level to identify gaps to inform future strategies on pesticide management, seeking to improve efficacy of interventions and reduce the side-effects of chemicals used on health and the environment. Methods A survey by questionnaire on the management practices of vector control insecticides was disseminated among all WHO Member States. Data were analysed using descriptive statistics in MS Excel. Results Responses were received from 94 countries, or a 48% response rate. Capacity for insecticide resistance monitoring was established in 68–80% of the countries in most regions, often with external support; however, this capacity was largely lacking from the European & Other...