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Currently, treatments for dengue infection are only symptomatic as no antiviral agents nor vaccines are available to combat this virus. Despite challenges faced by researchers, many efforts are ongoing to reduce cases of dengue infection either by targeting the vector or the virus. Vector population is monitored and reduced by using mechanical, chemical and biological controls. Chemical control is achieved either by using synthetic or natural insecticides where the latter is more preferable. In biological control, bacteria, fungi and larvivorous fish are utilised to reduce the vector population. Moreover, genes of mosquitoes are also explored to produce progenies which are sterile with low survival ability. Vaccines are among the most effective ways to prevent viral infection. Various approaches have been used and are still being explored towards producing vaccines for dengue. These include live attenuated, inactivated, recombinant subunit, nucleic acid and virus-like particles vaccines. The aim is to produce a vaccine which can target all the four serotypes of the virus. Monoclonal antibodies are widely researched on to equip the host defense mechanism against the dengue virus. Deeper understanding of the virus replication cycle warrants the development of antiviral agents which target viral proteins vital for the replication process. Bioactive compounds are also utilised in the development of antiviral agents. The importance of surveillance and supportive therapy are also discussed.

preparations are obtained by boiling the ripe pod pulp of C. fistula with water and filtered through muslin cloth, then evaporated to yield the soft extract for making pills. [11] The ripe pods contain anthraquinone compounds such as rhein, aloe-emodin and sennosides, in both glycosidic and free aglycone forms. [12-15] Anthraquinones are famous for their laxative property of which one of the laxative effects is caused by alteration in colonic absorption and secretion, resulting in fluid accumulation and consequently diarrhea. [16,17] Glycosides of anthraquinones, which are hydrolyzed by β-glucosides enzyme of the intestinal flora to free anthraquinones and further reduced to anthrones, are the active forms responsible for the laxative effect. The potency of the laxative/purgative effect depends on the amount of anthraquinone glycosides. [18,19] Nualkaew S. [20] previously compared the contents of total anthraquinones and total anthraquinone glycosides in four Cassia species, i.e. C. siamea Lamk., C. fistula Linn., C. alata Linn., and C. surattensis Burm.f. subsp. surattensis collected from 4 regions of Thailand. The results showed that the leaves of C. alata and the pod pulp of C. fistula contained the highest amount of total anthraquinone glycosides (1.33%

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Stemona collinsiae exhibits insecticidal resistance against various pests and insect vectors. However, insecticidal activity of S. collinsiae roots has not been tested for some insect vectors, including the American cockroach, Periplaneta americana . The synanthropic insect P. americana is a reservoir of pathogenic and non-pathogenic microorganisms and a cause of infectious diseases and cockroach allergy. This important vector transmits microorganisms to animals and humans to cause vector-borne diseases. This research involved detection of the nymphicidal and adulticidal activities of S. collinsiae root extracts against P. americana through oral administration. The effects of hexane, dichloromethane, ethanol, and water crude extracts were tested on final instar nymphs and adult P. americana . After P. americana ingested bait containing hexane and dichloromethane crude extracts, signs of toxicity occurred, such as hind leg shaking, whole-body tremor, immobility, abdomen swelling, and death. At 48 h, the nymphs and adult P. americana that ingested dichloromethane crude extract-containing bait showed corrected mortality of 65%–100% and 20%–100%, respectively. Whereas none of the nymphs and adult P. americana that ingested the water crude extract-containing bait died (0% corrected mortality). When we dissected alimentary canals of the dead P. americana that had ingested dichloromethane and hexane crude extract-containing baits, the foreguts were found to be swollen. TLC analysis showed the dichloromethane and hexane crude extracts contained the alkaloid didehydrostemofoline and unknown fluorescent substances. Phytochemicals from crude extracts were detected in extracts of dissected alimentary canals using thin-layer chromatography, and didehydrostemofoline alkaloid and unknown fluorescent substances were found in cockroaches that ingested dichloromethane- and hexane-containing baits. The cause of death of P. americana may be attributed to alkaloids and synergistic effects of other substances in S. collinsiae root extract. Mechanisms of action might include several pathways involved in nervous system function. Thus, dichloromethane and hexane crude extracts can be developed as alternative active ingredients in a natural insecticide for cockroach control.