Program Chair: Isobel Ronai
Insects (and other arthropods) have a huge impact on the health of humans and animals. The One Health approach highlights that the health of humans, animals and the environment are intertwined. Only by recognizing this animal-environment-human interface can we address complex health threats, such as newly emerging infectious diseases. Entomologists are conducting important research on the determinants of zoonotic and other diseases.
Sandflies and leishmaniasis in Sri Lanka
Leishmaniasis is a neglected tropical disease and a growing health problem in Sri Lanka. Cutaneous leishmaniasis is the predominant clinical form seen in the country with L. donovani as the causative agent. A few cases of visceral and mucosal leishmaniasis were also reported in recent years. The probable vector is Phlebotomus aregentipes var glaucus (Ph. glaucus). Biological and behavioral characteristics of the sandfly fauna in Sri Lanka are poorly understood, and hinder plans for disease control.
A nation-wide multi-site (n=10) longitudinal sandfly samplings was conducted from March 2018 to February 2020. The adult sandflies were collected using two cattle-baited net traps (CBNT) and 20 UV LED CDC light traps per site per month. The collected sandflies were preserved in absolute ethanol and transported to the laboratory for identification and further analysis to enable vector incrimination and identification of likely reservoir hosts through blood meal analysis. Sandfly identification was done using morphological and molecular methods.
Adult sand flies collected live from selected sites in 4 Provinces (north-central, north-western, southern and western) were used to study the pattern of insecticide susceptibility using biological, chemical and molecular methods. The flies were genetically analysed for the presence of known genes that may confer insecticide resistance. F1 progeny of field-collected Ph. argentipes were used for insecticide susceptibility testing based on standard bioassay kits (World Health Organization) with a pre-determined range of concentrations of known insecticides viz. DDT, malathion, deltamethrin and propoxur. The relationship between the concentration versus mortality was determined using Sigma Plot (version 10). ANOVA test was used to determine the extent of variation between tested samples of elevated enzymes and the remaining activities of enzyme of flies in each location. Extracted fly DNA samples were subjected to amplification of domain II VGSC gene sequences and compared and aligned with the NCBI database VGSC domain II sequence of Musca domestica (GenBank: AAB47604) to determine the presence of knockdown-resistance (kdr) type mutations of Ph. argentipes in Sri Lanka. Three molecular markers were used for molecular characterization and the analysis was done to determine the population genetic structure and evolutionary forces that operate within the sand fly population in Sri Lanka.
A total of 38,927 adult sand flies were collected from the 10 sentinel sites. Ph. argentipes was the dominant species that accounted for 99% of the captured flies with the rest identified as Sergentomyia spp. The monthly sand fly collections varied between sites and depending on the time of the year with most sites demonstrating a midyear peak collection. The sand fly collections through CBNT were 150~600-fold higher when compared to CDC light traps. The sandfly infection rate was 2.73%. Blood meal analysis of light trap-collected Ph. argentipes indicated majority of samples (>80%) containing human blood.
Insecticide-susceptibility levels of Ph. argentipes were higher than the discriminating dosages established for Aedes mosquitoes, except in the case of malathion. The percentage of knocked-down sand flies was <75% at any tested concentration, including those, which exhibited 100% mortality after 24 hours. Elevated activity levels of glutathione S-transferase (range: 3-14%) and esterase (2-6,5%) were detected in tested flies, while monooxygenase quantities remained below the cut-off level. Ten to 34.5% of flies were heterozygous for acetylcholinesterases target-site insensitivity, associated with organophosphate and carbamate resistance. Pyrethroid resistance-associated L1014F kdr-type mutation in the voltage gated sodium channel gene was detected in 30/53 flies. The analysis of the population genetic structure revealed unique sequences of ITS2 region and all genomic regions studied except the Cox 1 gene (100%) and Cytb gene (16.7%) with the latter favouring a likely gene flow.
Ph. argentipes, the incriminated vector of leishmaniasis in Sri Lanka is the more widely prevalent sand fly species in the country, with probable anthroponotic behaviour. Populations of Ph. argentipes studied were largely susceptible to common insecticides, except for malathion (used extensively in the past for malaria control), but with early signs of insecticide tolerance. Presence of insecticide target site insensitivity in a notable proportion of flies and enhanced insecticide metabolizing enzyme activities with a possible gene flow may indicate the potential for the spread of functionally important genes, such as the ones that confer insecticide resistance. Therefore, leishmaniasis control activities that are urgently required in Sri Lanka would need to be carefully planned and executed to enable future success.
Professor Nadira Karunaweera
Faculty of Medicine, University of Colombo
Colombo, Sri Lanka
Prof. Nadira D. Karunaweera is the Chair and Senior Professor of Parasitology at the Faculty of Medicine, University of Colombo and an honorary Visiting Fellow at the School of Public Health, Harvard University, USA. Trained as a Medical Parasitologist she has extensive teaching and research experience in tropical diseases, with special emphases on diseases transmitted by insects. Her achievements have been recognized both at local and international level with many awards, honors and fellowships bestowed upon her.
She functions as a team leader in multidisciplinary research in human infections caused by parasites and is responsible for pioneering work in the field of leishmaniasis; a newly established disease in Sri Lanka, with setting up of the first leishmaniasis diagnostic, training and research laboratory in the country.
Ticks and tick-borne diseases in small-scale farming systems – the Pakistani example
Ticks and tick-borne pathogens (TTBPs) substantially affect the health and production of ruminants, particularly in resource-poor, small-scale farming systems worldwide. Despite being the subject of intermittent studies over the past few decades in Pakistan, comprehensive information on the epidemiology and control of TTBPs is lacking. The microscopic/morphological examination had been the most widely used method for the identification of TTBPs in Pakistan. Ticks fauna comprise at least 40 species in small ruminants and 54 species in large ruminants, mainly belonging to genera Haemaphysalis, Hyalomma and Rhipicephalus. The prevalence of ticks is the highest in summer and it is also higher in goats and cattle than in sheep and buffaloes, respectively. Anaplasma, Babesia and Theileria spp. are the major tick-borne pathogens (TBPs), and their prevalence is usually higher in sheep and cattle than goats and buffalo, respectively. Spatiotemporal distribution, risk factors, genetic diversity, impact of climate change and control methods for ticks and TBPs as well as the competence of tick vectors for various TBPs remain to be explored. Therefore, coordinated, and focused research is required to fill knowledge gaps in these areas to maximise the health, production and welfare of ruminants and minimise economic losses associated with TTBPs in such small-holder farming systems.
Dr. Abdul Ghafar
Department of Veterinary Biosciences, Melbourne Veterinary School, University of Melbourne
I have completed a PhD in Veterinary Parasitology from the University of Melbourne. My PhD research focussed on the molecular epidemiology of ticks and tick-borne diseases in Pakistan using tools of participatory epidemiology (for data collection) and high-throughput molecular tools. I also hold a masters in virology/immunology and a DVM degree. My research interests include epidemiology and diagnosis of vector-borne diseases and socioeconomically important parasites of animals, and the parasite genomics and evolution.
HumBug – an acoustic mosquito monitoring tool for use on budget smartphones
There are over 3500 species of mosquito in the world of which only about 40 can be considered dangerous. These 40 species exhibit varying behavioural traits that influence how well they transmit disease as well as how successful different mosquito interventions are at controlling them. Therefore efficient mosquito control programmes rely on mosquito surveillance, which can be costly and in some cases, expose the vector surveillance team to a significant risk of disease.. We have developed a new surveillance methodology based on the distinct flight tome of these small insects. Our cross disciplinary project uses the inherent behaviour of anthropophagic (human biting) mosquitoes, a smartphone app and an algorithmic pipeline to detect and record their flight tones and subsequently identify these host-seeking mosquitoes inside people's homes.
Marianne Sinka, Department of Zoology, University of Oxford
Marianne is a Senior Postdoctoral Researcher at the Zoology Department at the University of Oxford. She specialises in mapping the spatial distribution of insect vectors of disease as well as understanding how their behaviour and ecology drive disease transmission.
Marianne is currently working with a multidisciplinary team to determine whether the wing beat frequency of a mosquito, alongside other peripheral data, can be used to identify vectors in malaria endemic countries (https://humbug.ox.ac.uk/)