ABSTRACT
@#Coccidiosis is a major recurring problem in the poultry industry and is caused by infection of one or more of the seven Eimeria species known to infect chickens, with Eimeria tenella among the best studied and economically important. Studies on the genetic diversity of E. tenella strains is essential for the development of universally acceptable diagnostic markers and vaccines against the disease. Eimeria tenella internal transcribed spacer-1 (ITS-1) and apical membrane antigen-1 (AMA-1) sequences from different parts of the world are available in the public domain and therefore provide suitable comparative markers for genetic diversity study. In this study, the ITS-1 and AMA-1 sequence diversity of two local E. tenella strains, namely EtNSN6 and EtSGR6 were characterized. Both ITS-1 and AMA-1 sequences for EtNSN6 and EtSGR6 were retrieved by mapping to their respective genome sequences generated using next generation sequencing. Multiple sequence alignment of the ITS-1 and AMA-1 sequences with selected homologous sequences revealed the presence of a total of five and 13 single nucleotide polymorphisms (SNPs) respectively. All SNPs appeared to occur at random and did not show any unique pattern based on geographical regions while no insertions and deletions (indels) was found to occur in the aligned sequences. However, unique bases that defined certain strains were detected. Phylogenetics analyses performed with Maximum Parsimony (MP) and Maximum Likelihood (ML) methods revealed similar topology for the internal groups with all the E. tenella ITS-1 and AMA-1 sequences grouped in the same clade supported by high bootstrap confidence. This confirmed that both EtNSN6 and EtSGR6 samples are E. tenella strains. Sequence comparison and phylogenetics analyses further suggest the possibility of low genetic diversity among E. tenella strains.
ABSTRACT
@#The continued absence of an effective and safe tetravalent dengue vaccine and the lack of specific anti-viral treatment have made mosquito vector control using chemical insecticides as the mainstream for dengue prevention and control. However, the long-term use of chemical insecticides may induce resistance. Hence detection of insecticide resistance in dengue vectors is crucially important in ensuring the insecticide-based intervention in dengue control program is still effective and reliable. In this study, the susceptibility status of Aedes aegypti from five selected dengue hotspots in Klang Valley, Malaysia against pyrethroids was determined by employing the World Health Organization (WHO) protocol of adult bioassay. Four types of pyrethroids were tested against adult female Aedes aegypti to determine the knockdown rate, post 24-h adult mortality and resistance ratio. All field-collected Aedes aegypti strains were resistant to the four pyrethroids tested, except for the Taman Sungai Jelok (TSJ) strain. Permethrin exhibited the lowest knockdown rate against Aedes aegypti, followed by deltamethrin, cyfluthrin and lambda-cyhalothrin. This present study indicated the widespread of pyrethroid resistance in Aedes aegypti in Klang Valley, indicating the needs of implementing alternative measures in vector control program. The data in this study can be utilised as an input for insecticide resistance management of Aedes aegypti in Malaysia.