Detection of dengue virus serotype 2 (DENV-2) in population of Aedes mosquitoes from Sibu and Miri divisions of Sarawak using reverse transcription polymerase chain reaction (RT-PCR) and semi-nested PCR.

Dengue has been a public health concern for many years in Malaysia. Having knowledge on the current circulating dengue serotypes and population of vector mosquitoes is key in controlling outbreaks and future outbreak predictions. The current study reports the first study on detecting dengue virus serotypes in the Aedes mosquito population in Sibu and Miri divisions of Sarawak. Mosquito samples were collected at selected localities from September 2016 to December 2017. Localities were selected mainly focussing on urban residential areas. The mosquitoes collected comprises of the field-caught adults and immatures collected from artificial and natural water containers. Collected mosquitoes were identified to species level and screened for the presence of dengue virus using conventional reverse transcription polymerase chain reaction (RT-PCR). Dengue virus serotype 2 (DENV-2) was identified in 3 pools of field-caught female Aedes albopictus adults collected from Jalan Tong Sang, Sibu, Sibu Lake Garden, and Taman Ceria, Permyjaya, Miri, respectively. DENV-2 was also detected in one pool of adult male Ae. albopictus emerged from immatures collected from Taman Ceria, Permyjaya, Miri. The findings in this study revealed that Ae. albopictus was the main species colonizing the study areas, and the current circulating dengue virus serotype was DENV-2. This study also reports the first natural evidence of transovarial transmission of dengue in the natural population of Ae. albopictus within the study area and provides information as reference for further vector-pathogen studies.

Detection of dengue virus serotype 2 (DENV-2) in population of Aedes mosquitoes from Sibu and Miri divisions of Sarawak using reverse transcription polymerase chain reaction (RT-PCR) and semi-nested PCR

@#Dengue has been a public health concern for many years in Malaysia. Having knowledge on the current circulating dengue serotypes and population of vector mosquitoes is key in controlling outbreaks and future outbreak predictions. The current study reports the first study on detecting dengue virus serotypes in the Aedes mosquito population in Sibu and Miri divisions of Sarawak. Mosquito samples were collected at selected localities from September 2016 to December 2017. Localities were selected mainly focussing on urban residential areas. The mosquitoes collected comprises of the field-caught adults and immatures collected from artificial and natural water containers. Collected mosquitoes were identified to species level and screened for the presence of dengue virus using conventional reverse transcription polymerase chain reaction (RT-PCR). Dengue virus serotype 2 (DENV-2) was identified in 3 pools of field-caught female Aedes albopictus adults collected from Jalan Tong Sang, Sibu, Sibu Lake Garden, and Taman Ceria, Permyjaya, Miri, respectively. DENV-2 was also detected in one pool of adult male Ae. albopictus emerged from immatures collected from Taman Ceria, Permyjaya, Miri. The findings in this study revealed that Ae. albopictus was the main species colonizing the study areas, and the current circulating dengue virus serotype was DENV-2. This study also reports the first natural evidence of transovarial transmission of dengue in the natural population of Ae. albopictus within the study area and provides information as reference for further vector-pathogen studies.

Serovar diversity of Leptospira sp. infecting wild rodents in Sarawak, Malaysia.

Leptopsirosis is a zoonotic disease with global distribution and rodents, in particular rats, have been identified as the main reservoir host. A study was conducted to determine the prevalence of antibodies against Leptospira sp. in wild rodents caught in selected areas of Sibu, Sarikei and Kapit in Sarawak during the period of July 2011 to May 2014. In total, 241 sera samples were collected from rodents caught from these three administrative divisions in Sarawak. Ninety-eight rodents (40.7%) were positive with antibody titre >1:50 by microscopic agglutination test (MAT) against 13 out of 20 common local leptospiral serovars tested. Sera of rodents caught in Sibu, Kapit and Sarikei divisions were positive at 43.9%, 37.5% and 36.4%, respectively. The top five serovars detected were: Autumnalis (25.5%), Tarassovi (23.5%), Bataviae (15.3%), Hebdomadis (8.2%) and Celledoni (7.2%). The main species of rodent positive for antibodies against Leptopsira sp. were Sundamys muelleri (50.0%), Rattus rattus (37.5%), Callociurus notatus (35.6%) and Rattus exulans (32.6%). This study indicates that leptospiral antibodies are prevalent amongst wild rodents in central Sarawak, which could be translated as high leptospiral carriage. The close interaction that exists between the local community and the environment could potentially propagate the transmission of Leptospira sp. to human in these areas. This study also provided essential information about local circulating Leptospira serovars, which could be useful for eventual prevention measures in disease transmission.

Eicosanoids in insect immunity: bacterial infection stimulates hemocytic phospholipase A2 activity in tobacco hornworms.

Intracellular phospholipase A(2) (PLA(2)) is responsible for releasing arachidonic acid from cellular phospholipids, and is thought to be the first step in eicosanoid biosynthesis. Intracellular PLA(2)s have been characterized in fat body and hemocytes from tobacco hornworms, Manduca sexta. Here we show that bacterial challenge stimulated increased PLA(2) activity in isolated hemocyte preparations, relative to control hemocyte preparations that were challenged with water. The increased activity was detected as early as 15 s post-challenge and lasted for at least 1 h. The increased activity depended on a minimum bacterial challenge dose, and was inhibited in reactions conducted in the presence of oleyoxyethylphosphorylcholine, a site-specific PLA(2) inhibitor. In independent experiments with serum prepared from whole hemolymph, we found no PLA(2) activity was secreted into serum during the first 24 h following bacterial infection. We infer that a hemocytic intracellular PLA(2) activity is increased immediately an infection is detected. The significance of this enzyme lies in its role in launching the biosynthesis of eicosanoids, which mediate cellular immune reactions to bacterial infection.

Eicosanoids in Insect Biology / Eicosanóides na Biologia de Insetos

Prostaglandinas e eicosanóides relacionados são metabolitos oxigenados de certos ácidos graxos poli-insaturados C20 . Eicosanóides são melhor entendidos em relação à sua significância clínica em medicina humana. Sugerimos um novo e mais amplo significado para os eicosanóides, o qual chamamos 'paradigma biológico'. Sob esse aspecto, notamos que eicosanóides desempenhavam funções como sinalizadores celulares antes da origem dos Metazoa. Durante a diversificação evolucionária dos animais, os eicosanóides têm sido envolvidos em uma serie de funções biológicas, algumas das quais ocorrendo somente em insetos e em outros invertebrados. Essas ações múltiplas dos eicosanóides permitem o melhor entendimento dos fenômenos biológicos. Para desenvolver essas idéias nós revisamos os papéis dos eicosanóides em duas áreas da biologia de invertebrados: mediação das reações da imunidade de insetos a bactérias e interações hospedeiro-parasita. Numa visão ampla, os eicosanóides desempenham importantes funções na organização biológica ao nível das células, dos organismos e das interações ecológicas. Sugerimos que os questionamentos contínuos sobre a significância dos eicosanóides levarão a novos entendimentos na biologia dos insetos.

Prostaglandins and related eicosanoids are oxygenated metabolites of certain C20 polyunsaturated fatty acids. Eicosanoids are best understood in the context of their clinical significance in human medicine. We suggest a new and broader view of eicosanoids, which we have been calling a 'biological paradigm'. Under this view, we note that eicosanoids were taken into roles as cellular signal moieties long before the origins of the Metazoa. During the evolutionary diversification of animals, eicosanoids have been recruited into an array of biological roles, some of which occur only in insects and other invertebrates. These multiple actions endow eicosanoids with unusual explanatory power in understanding biological phenomena. We review the roles of eicosanoids in two areas of invertebrate biology: mediation of insect immune reactions to bacteria and host-parasite interactions. Seen broadly, eicosanoids play important roles at the cellular, organismal and ecological levels of biological organization. We suggest that continued inquiry into the significance of eicosanoids will yield important new insights into insect biology.

Eicosanoids act in nodulation reactions to bacterial infections in newly emerged adult honey bees, Apis mellifera, but not in older foragers.

Nodulation is the first, and qualitatively predominant, cellular defense reaction to bacterial infections in insects. We tested the hypothesis that eicosanoids also mediate nodulation reactions to bacterial challenge in adults of a social insect, the honey bee, Apis mellifera. Treating newly-emerged experimental bees with the eicosanoid biosynthesis inhibitor, dexamethasone, impaired nodulation reactions to bacterial infections, and the influence of dexamethasone was reversed by treating infected insects with arachidonic acid, an eicosanoid precursor. Several other eicosanoid biosynthesis inhibitors, including the cyclooxygenase inhibitor, indomethacin, and the dual cyclooxygenase/lipoxygenase inhibitor, phenidone, also impaired the ability of experimental honeybees to form nodules in reaction to bacterial challenge. The influence of phenidone on nodulation was expressed in a dose-dependent manner. However, in experiments with older honey bees foragers, similar bacterial challenge did not evoke nodulation reactions. We infer from our results that while eicosanoids mediate cellular immune responses to bacterial infections in newly emerged honey bees, and more broadly, in most insect species, nodulation reactions to bacterial challenge probably do not occur in all phases of insect life cycles.

Arachidonic and eicosapentaenoic acids in tissues of the firefly, Photinus pyralis (Insecta: Coleoptera).

We report on the presence of high proportions of arachidonic acid (20:4n-6) and eicosapentaenoic acid (20:5n-3) in the tissue lipids of adult fireflies, Photinus pyralis. Arachidonic acid typically occurs in very small proportions in phospholipids (PLs) of terrestrial insects, ranging from no more than traces to less than 1% of PL fatty acids, while 20:5n-3 is often missing entirely from insect lipids. Contrarily, 20:4n-6 made up approximately 21% of the PL fatty acids prepared from whole males and females, and from heads and thoraces prepared from males. Proportions of 20:4n-6 associated with PLs varied among tissues, including approximately 8% for male gut epithelia, 13% for testes, and approximately 25% for light organs and body fat from males. Substantial proportions of 20:5n-3 were also associated with PLs prepared from male firefly tissues, including 5% for body fat and 8% for light organs. Because 20:4n-6 and 20:5n-3 are precursors for biosynthesis of prostaglandins and other eicosanoids, we considered the possibility that firefly tissues might produce eicosanoids at exceptionally high rates. Preliminary experiments indicated otherwise. Hence, fireflies are peculiar among terrestrial insects with respect to maintaining high proportions of PL 20:4n-6 and 20:5n-3.

Eicosanoids mediate nodulation reactions to bacterial infections in larvae of the butterfly, Colias eurytheme.

Nodulation is the first, and qualitatively predominant, cellular defense reaction to bacterial infections in insects. Treating larvae of the butterfly Colias eurytheme with the eicosanoid biosynthesis inhibitor dexamethasone, strongly impaired nodulation reactions to bacterial infections. The influence of dexamethasone was reversed by treating infected insects with arachidonic acid, an eicosanoid precursor. An eicosanoid biosynthesis system in C. eurytheme larvae is documented. Specifically, the presence of eicosanoid-precursor polyunsaturated fatty acids in tissue phospholipids was determined, an intracellular phospholipase A2 that can release arachidonic acid from tissue phospholipids was recorded, and eicosanoid biosynthesis, registered as conversion of exogenous radioactive 20:4n-6 into eicosanoids, was observed. These findings support the hypothesis that eicosanoids mediate cellular immune responses to bacterial infections in these butterfly larvae, and more broadly, in most, if not all, insects.