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Papers by Philip Samuel

Journal of Vector Borne Diseases, 2021

Background & objectives: Dengue emerged as an important public health problem in Tamil Nadu f... more Background & objectives: Dengue emerged as an important public health problem in Tamil Nadu from 2000 onwards, reported in all the districts as an endemic disease of Tamil Nadu except Nilgiris district. So this study was carried out to understand the dengue epidemiology in Nilgiris district. Methods: Block-wise study was made at the Nilgiris district. The clinicians at the Nilgiris Adivasi Welfare Association hospitals (NAWA) situated in Kotagiri, Kozhikarai and Primary Health Centers from Kunjpannai, Arayoor, and Soloor Mattam, examined and recorded symptoms and collected blood samples from the dengue-suspected patients. These samples were centrifuged at 4°C and stored. Serum samples (267 nos.) collected from dengue-suspected patients for two years period from 2014 to 2016 were screened for dengue infection. Results: First year study conducted during 2014-15 showed 13 dengue positives (8.39%) mainly from Kotagiri block (9 nos. - 69.2%) and the second year study conducted during 2015-16 showed 12 dengue positives (10.71%) found mostly from Udagamandalam block (6 nos.- 50%). People belonging to 6 different tribes - Irular, Toda, Kota, Kurumba, Kattunaickan, and Paniya were found infected with dengue and more Irular positives were recorded in both the years (5 Irular-2014-15 & 11 Irular -2015-16). First year detected more female positives (92.3%) whereas the second year showed 5 males (41.7%) and 7 females (58.3%). Interpretation & conclusion: This study unearthed the hidden disease dengue to be prevalent among the tribal community and emphasized the need for the establishment of a permanent dengue surveillance system with improved disease diagnostics, to initiate effective vector control efforts to stop dengue transmission from this hilly region.

Journal of Entomological and Acarological Research, Dec 19, 2016

An entomological monitoring of Japanese encephalitis vectors from the Cuddalore district, Tamil N... more An entomological monitoring of Japanese encephalitis vectors from the Cuddalore district, Tamil Nadu was undertaken at biweekly intervals for 1 hr after dusk for five years to find out the abundance and JE virus activity longitudinally in three villages. A total of 95,644 vectors belonging to 31 species constituted predominantly by Culex vishnui subgroup and Culex gelidus 98.5%. JE virus was identified from Cx. tritaeniorhynchus (18), Cx. vishnui (1) and Cx. gelidus (6) giving infection rate of 0.482, 0.608 and 0.221 respectively. Abundance of Cx. tritaeniorhynchus and Cx. gelidus differed significantly by area, season and year (P<0.05) whereas Cx. vishuni differed significantly by season and year (P<0.05). Transmission was not observed throughout all the seasons and the infection rate was recorded maximum during Hot-Wet season 0.46 (confidence interval: 0.17-1.02). Culex tritaeniorhynchus dominated the catch and the Culex gelidus steadily increased in its abundance during this period compared to the earlier studies conducted from these areas which acts as a secondary vector along with the major vector, Cx. tritaeniorhynchus.

PubMed, Dec 1, 2014

Background & objectives: A longitudinal, entomological and virological study was conducted from 2... more Background & objectives: A longitudinal, entomological and virological study was conducted from 2007 to 2010 in four dengue fever affected areas of Thiruvananthapuram district, Kerala to understand the risk factors involved in the dengue transmission. Methods: Aedes surveys were carried out seasonally in the selected localities both indoors and peridomestic sites. Water holding containers were sampled for the presence of immature. Outdoor and indoor resting/landing mosquitoes were collected. Blood meal identification was performed by gel diffusion test and viral assay using the ELISA test. Results: The species found were Aedes (Stegomyia) aegypti (Linn.), Ae. (Stegomyia) albopictus (Skuse) and Ae. (Stegomyia) vittatus (Bigot). Aedes aegypti and Ae. albopictus immature stages were also found during the study period. Aedes aegypti was the only prevalent species in the water-starved Vizhinjam, a rural coastal area with breteau index (BI) ranging from 40 to 271. Aedes albopictus was recorded in rest of the three surveyed localities—two urban and one rural ghat areas of Thiruvananthapuram district. Interpretation & conclusion: The vector control measures should be focused mainly on source reduction of water storage containers present in both outdoor (Ae. albopictus and Ae. vittatus) and indoor (Ae. aegypti). To achieve effective vector management, a public health response beyond routine larviciding or focal spraying is essential throughout the year.

PubMed, May 1, 2013

Sir, Vector-borne diseases are a major cause of human suffering both in terms of morbidity and mo... more Sir, Vector-borne diseases are a major cause of human suffering both in terms of morbidity and mortality. Japanese encephalitis (JE) is a mosquito-borne disease, caused by flavivirus that infects vertebrate hosts, primarily birds belonging to the family Ardeidae and swine, naturally maintained in an enzootic cycle1,2. An outbreak, suspected to be JE occurred in the Muzaffarpur district, Bihar in June, 2011. The symptoms were high fever, followed by bouts of unconsciousness and convulsions akin to a type of JE were noticed. Several children died in Tirhut division alone with the maximum number of deaths concentrated in and around Muzaffarpur district. During the month of June, 125 cases and 43 deaths were reported from both Sri Krishna Medical College and Hospital (SKMCH) and Krishna Daviprasad Kesarival Institution (KDKM) in the district. Although all the afflicted children uniformly suffered from high fever, which gave way to convulsions and seizures, and brought in a semi-consciousness state for treatment, but the possibility of JE was ruled out based on the analysis of human serum samples in Muzaffarpur district during July 2011. As no confirmed reports were available on the aetiology of the present outbreak, the secondary data available confirmed that the mysterious fever was not JE and the cases were also negative for Chandipura and Nipah3,4,5. The Centre for Research in Medical Entomology (CRME), Madurai, Tamil Nadu undertook an investigation in July 2011 on entomo-virological aspects to confirm/rule out the JE virus involvement in the vector mosquitoes. Investigation of a mosquito borne epidemic is mainly based on clinical case reporting and abundance of vector mosquitoes. The monitoring of virus infection in vector mosquitoes is an essential component for the confirmation of the same6. The main objective of the investigation was to determine the JEV infection in mosquito vector populations to understand their role in the present outbreak. During the investigation, the mosquito vector species composition in the affected villages of the district was recorded to know the density and diversity of the prevalent vector. Mosquitoes resting on vegetation and bushes around cattle sheds and pigstys were collected after dusk with the help of oral aspirator and flash torch, and transported to the laboratory for identification to the species level based on standard identification keys available for Culex vishnui subgroup7,8. In the Nawada village of Musahari primary health centre (PHC), only Culex quinquefasciatus and Armigeres subalbatus were collected and in Manickpur village of the same PHC Cx. tritaeniorhynchus, Cx. gelidus, Cx. quinquefasciatus, Mansonia uniformis, Anopeles subpictus, An. vagus and Aedes lineatopennis were collected. In Tiwari Tola village of Kanti PHC, the mosquito species namely Cx. tritaeniorhynchus, Cx. gelidus, Cx. quinquefasciatus, Cx. pseudovishnui, An. vagus, Ae. lineatopennis and Ar. subalbatus were collected. In the village Choppara of Bochahan PHC the mosquitoes like Cx. tritaeniorhynchus, Cx. gelidus, Cx. quinquefasciatus, Mn. uniformis, An. vagus, Ae. lineatopennis and Ar. subalbatus were collected. Subsequently collections were carried out in the village Nakta situated in the Motipur PHC where the mosquitoes like Cx. tritaeniorhynchus, Cx. gelidus and Ar. subalbatus were collected. Lastly in the Ganipur Beja village from Sakra PHC, mosquitoes like Cx. pseudovishnui, Cx. fuscocephala, Cx. (Lut.) fuscanus. An. subpictus, Ae. lineatopennis and Ar.subalbatus were collected. Thus, a total of 11 species of mosquitoes (Cx. tritaeniorhynchus, Cx. gelidus, Cx. pseudovishnui, Cx. fuscocephala, Cx. quinquefasciatus, Cx. (Lut.) fuscanus, Ae. lineatopennis, Mn. uniformis, An. subpictus, An. vagus and Ar. subalbatus) were collected. In addition, Cx. infula, An. subpictus, Ae. vittatus and Ae. lineatopennis were also collected from the larval survey conducted in paddy fields, cement cisterns, etc. Antigen capture ELISA was carried out to detect the JE antigen in the pools prepared with Cx. tritaeniorhynchus (5 pools), Cx. quinquefasciatus (8), Cx. gelidus (4), Cx. pseudovishnui (2), Cx. fuscocephala (1), Cx. fuscanus (1), Cx. infula (1), An. subpictus (5), Ar. subalbatus (8), An. vagus (3), and Mn. uniformis (3) pools. All the 41 pools tested were found negative for JEV. Mosquito pools, Ae. vittatus (2 pools) and Ae. lineatopennis (2 pools) were also tested for dengue and found negative. So far JE virus infection in vector mosquitoes has not been reported from this district of Bihar. Even though Bihar State is prone to many vector borne diseases, information on vector biodiversity is scanty. The JEV infection in mosquitoes could not be detected from the collected samples of the affected areas. The absence of JEV infection in vector mosquitoes further supports the absence of JE positives in the serological investigations. A detailed in-depth longitudinal study need to be undertaken further…

International Journal of Zoology Studies, Mar 1, 2016

International Journal of Tropical Insect Science, Dec 1, 2008

Bacillus sphaericus (Bs) is a potential mosquito larvicide especially against Culex quinquefascia... more Bacillus sphaericus (Bs) is a potential mosquito larvicide especially against Culex quinquefasciatus (Say), the vector of bancroftian filariasis. It is a gram-positive, aerobic and endospore-forming bacterium. During sporulation, it synthesizes binary endotoxins (molecular weight 42 and 51 kDa proteins) that are highly toxic to mosquito species. The mode of action of the binary toxin of this biolarvicide in the alimentary canal and the ultrastructural events in the tissues of the affected larvae have been demonstrated. Lysosomal components are the most important organelles involved in the metabolism of the foreign molecules encountered by the cells. In this paper, we report the ultrastructural changes in the midgut epithelial cells, with special emphasis on lysosomes (L), in untreated Cx. quinquefasciatus larvae and those treated with the Bs-IAB59 bacterial strain. In the Bstreated larvae, the size of the L gradually increased, and within 16 h, fine filaments appeared and compartmentalized into small lamellar bodies, within the L. After 36 h, these lamellar bodies appeared to be collapsed, and later disintegrated in the 48th hour. In the untreated larvae, such ultrastructural changes in the L were not seen. These observations suggested that, though the target site of action of the Bs toxin is the midgut epithelial cells, ultrastructural changes in the L compartments play a vital role in the mortality of the mosquito larvae.

PubMed, Apr 1, 2009

Background & objective: An outbreak of chikungunya fever characterized by prolonged incapacitatio... more Background & objective: An outbreak of chikungunya fever characterized by prolonged incapacitation in the Lakshadweep islands in Indian Ocean occurred in November 2006. We undertook the entomological and epidemiological investigations on the Chikungunya outbreak in the Lakshadweep islands, Indian Ocean. Methods: Epidemic information in the affected places was obtained from the local hospital records. Entomological observations like larval survey and the adult resting/landing collections by the hand collection methods were individually conducted in the two affected islands Andrott and Kalpeni in November and December 2006. Results: The main breeding sources of the mosquitoes were the rodent-devoured coconuts, coconut shells, areca nut soaking mud and plastic pots, discarded containers, grinding stones, metal containers and plastic containers. Aedes albopictus was pre-dominantly present in the Lakshadweep islands. Interpretation & conclusion: It is concluded that the routine campaigns need to be organized regularly within the community highlighting the potential breeding grounds of mosquitoes and the possible control methods. Source reduction strategies like destruction of coconut shells and rodent-devoured coconuts by burning or by burying them inside the ground. Ae. albopictus played major role as the vector mosquitoes responsible for the chikungunya transmission.

Background: An outbreak of Zika fever occurred in Thiruvananthapuram City, Kerala, India during 2... more Background: An outbreak of Zika fever occurred in Thiruvananthapuram City, Kerala, India during 2021. We investigated the same, on request of Kerala state health administration towards proposing containment strategies. Methods: Epidemiological and entomological investigations as well as genome analysis of ZIKA Virus (ZIKV) involved in the infections were performed, targeting crucial and phylogenetically important mutations in the Capsid-pre Membrane, Envelope and Non-Structural protein -5 gene sequences. Results: A clustering pattern of cases was observed during the outbreak, with the presumed index case from a multi-speciality hospital, in Thiruvananthapuram city. The causative ZIKV belonged to the Asian strain, however, distinct from the pandemic American lineage. The predominant Aedes albopictus (65.55%), Aedes aegypti (22.0%) and Aedes vittatus (12.0%) species were found naturally infected with ZIKV, the Minimum Infection Rates being 17.9, 7.8 and 3.6 respectively. Also, trans-ovarian transmission was recorded in Ae. albopictus. Conclusions: ZIKV isolates presented with four unique non synonymous mutations viz., “I22T” & “I160M” (pre-Membrane) and “D348N” & “V473L” (Envelope) during the outbreak which’s implications remains to be investigated. Phylogenetic analysis of the gene sequences indicated the emergence of a distinct genetic lineage of ZIKV in India. Our investigations evince the urgent need of development of a systematic country-wide surveillance strategy, towards the prevention/ preparedness/ containment of a massive outbreak of this emerging arbo-viral disease. Funding: This study was performed utilizing intramural funds of Indian Council of Medical Research-Vector Control Research Centre. Declaration of Interest: The authors declare no known competing financial interests or personal relationships/interests that could have appeared to influence the work reported in this manuscript. Ethical Approval: As the study was an outbreak investigation carried out on the request of the Department of Health Services, Government of Kerala. India, institutional ethical approval was not essential the time of investigation. Most of the samples processed were from mosquito specimens. Informed consent forms were obtained from all the four patients from whom blood samples were obtained during the investigation. However, towards on going further investigations institutional ethical approval was obtained retrospectively.

ENTOMON, 2020

In India, Japanese Encephalitis (JE) continues to be a public health issue in some parts of our c... more In India, Japanese Encephalitis (JE) continues to be a public health issue in some parts of our country. JE surveillance includes early reporting of clinical cases, sentinel sero-surveys and vector surveillance in the endemic areas. In the present study, JE longitudinal vector surveillance and epidemiological investigations were carried out for the first time during two consecutive years in the endemic district of Tamil Nadu. 22,538 mosquitoes were collected, species identified and screened for JE virus by RT-PCR. Predominant was Culex tritaeniorhynchus (60%) and followed by it Anopheles subpictus (23%), Culex quinquefasciatus (8%) and Culex gelidus (3%). It suggests that Culex tritaeniorhynchus may act as major vector and An. subpictus may act as secondary vector. Monsoon and post-monsoon seasons favour breeding of Cx. tritaeniorhynchus leading to vector abundance. Preferential resting sites for Cx. tritaeniorhynchus were pig and cattle shed. Although clinical cases have been repor...

Journal of Communicable Diseases, 2019

International Journal of Contemporary Medicine, 2019

Tropical doctor, Jan 12, 2016

As original tribal ways of living have morphed from a forest dweller existence, dengue is no long... more As original tribal ways of living have morphed from a forest dweller existence, dengue is no longer an urban infection but is now also found in rural hilly areas. The spread of dengue is enhanced by the frequent movement of people to endemic areas where there is a vector mosquito presence. The impact of the virus is known to be great in the immunologically naive population. Our study reports on the threat of the dengue virus in these hilly areas.

The Indian journal of medical research, 2013

Japanese encephalitis virus (JEV) is a major mosquito-borne encephalitic flavivirus of rural east... more Japanese encephalitis virus (JEV) is a major mosquito-borne encephalitic flavivirus of rural eastern, south eastern and southern Asia. Outbreaks of Japanese encephalitis (JE) have occurred in many States in India 1. An explosive insular outbreak of meningoencephalitis occurred during early 1996 in the Kuttanad area of Allepey district, Kerala 2. Numerous cases of chikungunya virus (CHIKV) infection have been reported from a major outbreak around the Indian Ocean which included southern India 3. In India, during 2006, 14 States and Lakshadweep Island were affected by chikungunya fever 4,5. In Kerala, outbreak of chikungunya began for the first time in 2006 affecting nearly 70,000 persons from 14 districts 5. In May 2007, another outbreak occurred affecting almost all the districts 6. Increased death toll was due to chikungunya in Kerala 7. Alappuzha district lies at the western part of Kerala and was worst affected. During the outbreak in May 2011, 23 cases were recorded in Alappuzha district. An epidemic survey was done by a team of Centre for Research in Medical Entomology (CRME), Madurai and Kerala State Institute of Virology and Infectious Diseases. After obtaining informed written consent from the suspected JE patients blood samples (2 ml) were obtained with the help of Government Tirumala Devaswom (TD) Medical college hospital staff and Kerala State Institute of Virology staff. The serum samples were analyzed for JEV-specific immunoglobulin M (IgM) antibodies, dengue virus (DENV)-specific IgM antibodies and CHIKV specific IgM antibodies separately by using separate and specific MAC ELISA kits supplied by National Institute of Virology, Pune, India. The serum samples

Journal of Medical Entomology, 1997

2014 International Conference on Recent Trends in Information Technology, 2014

Suppression of mosquito breeding is a mandatory first step to reduce the source of major mosquito... more Suppression of mosquito breeding is a mandatory first step to reduce the source of major mosquito-borne diseases like Malaria and Dengue fever. This paper deals with an innovative method for the identification of mosquito breeding sites (stagnant pools), using wireless networking technologies and removal of stagnant water through electromechanical pumping systems. The stagnant water areas are first identified and reported by public users using a web-based portal or using Short Message Service (SMS) through mobile phones. Based on the complaints stored in the database, a route via the stagnant sites is drawn on a map using a Geographic Information System (GIS). A vehicle carrying a Global Positioning system (GPS), on-board camera, and a pumping system with a tank for removing the stagnant water traverses the via points of stagnant pools. Finally, stagnant water is removed using a pumping system and stored in the onboard tank for emptying later. Results of the implementation of a proof-of-concept prototype system are reported, to illustrate the effectiveness of the proposed approach.

Journal of Clinical Virology, 2004

Zenodo (CERN European Organization for Nuclear Research), Dec 31, 2021

Trombiculid chigger mites were collected from pest rodents and shrews. This study was carried out... more Trombiculid chigger mites were collected from pest rodents and shrews. This study was carried out in different habitats like urban, semi-urban, and rural sites in Madurai district, South Tamil Nadu, India during 2017-2018. A total of 3219 chigger mites comprising 12 different species under three families (Trombiculidae, Dermanyssidae and Laelapidae) and one sub order (Oribatida) were collected from 151 rodents and shrews, belonging to six different species in this study. The chigger infestation rate in these small mammals was 56.47. The following chigger mites and adult mite species were identified from the Madurai district: Leptotrombidium deliense, L. keukenschrijveri, L. indicum, L. rajesthanense, Schoengastiella ligula, Microtrombicula sp., Neotrombicula microti, Trombicula hypodermata, Schoengastia species (Chigger mites); Dermanyssus gallinae, Laelaps echidninus, Liponyssoides sanguineus and Oribatida (Adult mites). The predominant species recorded from these areas are L. deliense (65.94%), L. indicum (11.50) and S. ligula (15.27). Even though maximum chigger mites infestation rate was recorded in rodents and shrews from urban areas (65.5), followed by semi-urban (53.5) and rural (54.5) areas. Trap positivity rate (18.1%), rodents/shrew captures (5.42±2.97) and chigger collection (118.08±188.9) were observed significantly (P <0.05) more in rural clusters compared with urban clusters. This study showed the predominant trombiculid mites activity on small mammals of this place which can forewarn the public health officials to understand the ground-level situation to take up necessary control measures for the prevention of mite borne diseases.

Indian Journal of Medical Research, 2015

Background & objectives: Japanese encephalitis (JE) is the leading cause of viral encephalitis in... more Background & objectives: Japanese encephalitis (JE) is the leading cause of viral encephalitis in Asia. The first major JE outbreak occurred in 1978 and since 1981 several outbreaks had been reported in the Cuddalore district (erstwhile South Arcot), Tamil Nadu, India. Entomological monitoring was carried out during January 2010-March 2013, to determine the seasonal abundance and transmission dynamics of the vectors of JE virus, with emphasis on the role of Culex tritaeniorhynchus and Cx. gelidus. Methods: Mosquito collections were carried out fortnightly during dusk hours in three villages viz. Soundara Solapuram, Pennadam, Erappavur of Cuddalore district. Mosquitoes were collected during dusk for a period of one hour in and around the cattle sheds using oral aspirator and torch light. The collected mosquitoes were later identified and pooled to detect JE virus (JEV) infection by enzyme linked immunosorbent assay (ELISA). Results: A total of 46,343 mosquitoes comprising of 25 species and six genera were collected. Species composition included viz, Cx. tritaeniorhynchus (46.26%), Cx. gelidus (43.12%) and other species (10.62%). A total of 17,678 specimens (403 pools) of Cx. gelidus and 14,358 specimens (309 pools) of Cx. tritaeniorhynchus were tested, of which 12 pools of Cx. gelidus and 14 pools of Cx. tritaeniorhynchus were positive for JE virus antigen. The climatic factors were negatively correlated with minimum infection rate (MIR) for both the species, except mean temperature (P<0.05) for Cx. gelidus. Interpretation & conclusions: High abundance of Cx. tritaeniorhynchus and Cx. gelidus was observed compared to other mosquito species in the study area. Detection of JEV antigen in the two species confirmed the maintenance of virus. Appropriate vector control measures need to be taken to reduce the vector abundance.