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The effect of Plasmodium vivax infection on SOCS gene expression in Anopheles dirus (Diptera: Culicidae)

Kittiwattanawong K, Ponlawat A, Boonrotpong S, Nanakorn N, Kongchouy N, Moonmake S, et al.

Trop Biomed, 2020 Jun 01;37(2):397-408.
PMID: 33612809

The Anopheles dirus mosquito is a primary malaria vector that transmits many species of Plasmodium parasites in Thailand and is widely spread across its geographic area. In the current study, the levels of expression of the suppressor of cytokine signaling (SOCS) gene in An. dirus mosquitoes infected with P. vivax were examined. The level of the gene's expression determined by mRNA extraction in An. dirus females (n=2,400) was studied at different times (0, 12, 24, 36, and 48 h after feeding), with different types of blood feeding (non-feeding, parasite-negative blood feeding, parasite-positive blood feeding) and in different parts of the body of mosquito samples (thorax and abdomen). The datasets were analyzed based on their relative expression ratio by the 2-ΔΔCT method and were tested for significant differences with ANOVA. The results showed that the An. dirus SOCS gene was stimulated in the abdomen 12 h and 24 h after blood feeding about three times more highly than in unfed females, with the difference being significant. At 24 h after P. vivax-infected blood feeding, the SOCS gene in the abdomen was expressed more highly than 24 h after parasite-negative blood feeding and expression was almost 36 times higher than in the control group who were not fed blood. However, in the thorax at all times after feeding and non-feeding, there was no expression of the SOCS gene. Therefore, the SOCS gene in An. dirus was most highly expressed 24 h post-feeding with a P. vivax-infected bloodmeal, which indicates that the SOCS gene in the major malaria vector in Thailand plays an important role in its immune system and its response to P. vivax infection.

Matched MeSH terms: Anopheles/genetics*
Genetic diversity and molecular identification of mosquito species in the Anopheles maculatus group using the ITS2 region of rDNA

Walton C, Somboon P, O'Loughlin SM, Zhang S, Harbach RE, Linton YM, et al.

Infect Genet Evol, 2007 Jan;7(1):93-102.
PMID: 16782411

The species diversity and genetic structure of mosquitoes belonging to the Anopheles maculatus group in Southeast Asia were investigated using the internal transcribed spacer 2 (ITS2) of ribosomal DNA (rDNA). A molecular phylogeny indicates the presence of at least one hitherto unrecognised species. Mosquitoes of chromosomal form K from eastern Thailand have a unique ITS2 sequence that is 3.7% divergent from the next most closely related taxon (An. sawadwongporni) in the group. In the context of negligible intraspecific variation at ITS2, this suggests that chromosomal form K is most probably a distinct species. Although An. maculatus sensu stricto from northern Thailand and southern Thailand/peninsular Malaysia differ from each other in chromosomal banding pattern and vectorial capacity, no intraspecific variation was observed in the ITS2 sequences of this species over this entire geographic area despite an extensive survey. A PCR-based identification method was developed to distinguish five species of the group (An. maculatus, An. dravidicus, An. pseudowillmori, An. sawadwongporni and chromosomal form K) to assist field-based studies in northwestern Thailand. Sequences from 187 mosquitoes (mostly An. maculatus and An. sawadwongporni) revealed no intraspecific variation in specimens from Thailand, Cambodia, mainland China, Malaysia, Taiwan and Vietnam, suggesting that this identification method will be widely applicable in Southeast Asia. The lack of detectable genetic structure also suggests that populations of these species are either connected by gene flow and/or share a recent common history.

Matched MeSH terms: Anopheles/genetics*
Speciation and phylogeography of the Southeast Asian Anopheles sundaicus complex

Dusfour I, Michaux JR, Harbach RE, Manguin S

Infect Genet Evol, 2007 Jul;7(4):484-93.
PMID: 17350896

Anopheles sundaicus s.l. is a malaria vector in coastal areas of Southeast Asia. Previous studies showed at least four distinct species within the complex. The present study investigated the phylogeography and the status of A. sundaicus s.l. populations from Cambodia, Thailand, Malaysia and Indonesia with regard to A. sundaicus s.s. from Sarawak, Malaysian Borneo and A. epiroticus in Vietnam and Thailand. Three lineages recovered by analyses of Cyt-b and COI (mtDNA) confirmed the presence of A. sundaicus s.s. in Malaysian Borneo, the distribution of A. epiroticus from southern Vietnam to peninsular Malaysia, and recognised a distinct form in Indonesia that is named A. sundaicus E. The phylogenetic and demographic analyses suggest that the three species were separated during the Early Pleistocene (1.8-0.78 Myr) and experienced bottlenecks followed by a genetic expansion in more recent times. Based on the results and knowledge of the biogeography of the area, we hypothesise that the combination of cyclical island and refugium creation was the cause of lineage isolation and bottleneck events during the Pleistocene.

Matched MeSH terms: Anopheles/genetics*
Fulltext Temporal and spatial trends in insecticide resistance in Anopheles arabiensis in Sudan: outcomes from an evaluation of implications of insecticide resistance for malaria vector control

Ismail BA, Kafy HT, Sulieman JE, Subramaniam K, Thomas B, Mnzava A, et al.

Parasit Vectors, 2018 03 02;11(1):122.
PMID: 29499751 DOI: 10.1186/s13071-018-2732-9

BACKGROUND: Long-lasting insecticidal nets (LLINs) (with pyrethroids) and indoor residual spraying (IRS) are the cornerstones of the Sudanese malaria control program. Insecticide resistance to the principal insecticides in LLINs and IRS is a major concern. This study was designed to monitor insecticide resistance in Anopheles arabiensis from 140 clusters in four malaria-endemic areas of Sudan from 2011 to 2014. All clusters received LLINs, while half (n = 70), distributed across the four regions, had additional IRS campaigns.
METHODS: Anopheles gambiae (s.l.) mosquitoes were identified to species level using PCR techniques. Standard WHO insecticide susceptibility bioassays were carried out to detect resistance to deltamethrin (0.05%), DDT (4%) and bendiocarb (0.1%). TaqMan assays were performed on random samples of deltamethrin-resistant phenotyped and pyrethrum spray collected individuals to determine Vgsc-1014 knockdown resistance mutations.
RESULTS: Anopheles arabiensis accounted for 99.9% of any anopheline species collected across all sites. Bioassay screening indicated that mosquitoes remained susceptible to bendiocarb but were resistance to deltamethrin and DDT in all areas. There were significant increases in deltamethrin resistance over the four years, with overall mean percent mortality to deltamethrin declining from 81.0% (95% CI: 77.6-84.3%) in 2011 to 47.7% (95% CI: 43.5-51.8%) in 2014. The rate of increase in phenotypic deltamethrin-resistance was significantly slower in the LLIN + IRS arm than in the LLIN-only arm (Odds ratio 1.34; 95% CI: 1.02-1.77). The frequency of Vgsc-1014F mutation varied spatiotemporally with highest frequencies in Galabat (range 0.375-0.616) and New Halfa (range 0.241-0.447). Deltamethrin phenotypic-resistance correlated with Vgsc-1014F frequency.
CONCLUSION: Combining LLIN and IRS, with different classes of insecticide, may delay pyrethroid resistance development, but the speed at which resistance develops may be area-specific. Continued monitoring is vital to ensure optimal management and control.

Matched MeSH terms: Anopheles/genetics
Molecular identification of Anopheles (Cellia) sundaicus from the Andaman and Nicobar islands of India

Alam MT, Das MK, Ansari MA, Sharma YD

Acta Trop, 2006 Jan;97(1):10-8.
PMID: 16125659

Anopheles (Cellia) sundaicus (Rodenwaldt) is an important malaria vector in the Andaman and Nicobar islands of India where it breeds in freshwater as well as in brackish water. To establish the molecular identity of An. sundaicus on these islands we analyzed samples from four geographically isolated areas-Teressa, Nancowry, Car Nicobar and Katchal islands. PCR-amplification and nucleotide sequence analysis were performed for internal transcribed spacer 2 (ITS2) and domain-3 (D3) of 28S rRNA. The ITS2 region of An. sundaicus from all four islands was identical but different from An. sundaicus A of Vietnam and An. sundaicus s.s of Malaysia. Furthermore, freshwater and brackish water forms of An. sundaicus did not reveal any sequence variation. Similarly, the D3 sequences were identical among all An. sundaicus samples from the four islands. D3 sequences for a species of the Sundaicus Complex are reported here for the first time and thus could not be compared with other regional isolates of this species. In conclusion, probably only one member of the Sundaicus Complex exists on the Andaman and Nicobar islands, which breeds in freshwater as well as in brackish water and is different from the An. sundaicus A and Malaysian An. sundaicus s.s. The identification of a new sibling species of the Sundaicus Complex in these islands is significant from the viewpoint of vector control strategies.

Matched MeSH terms: Anopheles/genetics
Fulltext Microsatellite and mitochondrial markers reveal strong gene flow barriers for Anopheles farauti in the Solomon Archipelago: implications for malaria vector control

Ambrose L, Cooper RD, Russell TL, Burkot TR, Lobo NF, Collins FH, et al.

Int J Parasitol, 2014 Mar;44(3-4):225-33.
PMID: 24440418 DOI: 10.1016/j.ijpara.2013.12.001

Anopheles farauti is the primary malaria vector throughout the coastal regions of the Southwest Pacific. A shift in peak biting time from late to early in the night occurred following widespread indoor residue spraying of dichlorodiphenyltrichloro-ethane (DDT) and has persisted in some island populations despite the intervention ending decades ago. We used mitochondrial cytochrome oxidase I (COI) sequence data and 12 newly developed microsatellite markers to assess the population genetic structure of this malaria vector in the Solomon Archipelago. With geographically distinct differences in peak A. farauti night biting time observed in the Solomon Archipelago, we tested the hypothesis that strong barriers to gene flow exist in this region. Significant and often large fixation index (FST) values were found between different island populations for the mitochondrial and nuclear markers, suggesting highly restricted gene flow between islands. Some discordance in the location and strength of genetic breaks was observed between the mitochondrial and microsatellite markers. Since early night biting A. farauti individuals occur naturally in all populations, the strong gene flow barriers that we have identified in the Solomon Archipelago lend weight to the hypothesis that the shifts in peak biting time from late to early night have appeared independently in these disconnected island populations. For this reason, we suggest that insecticide impregnated bed nets and indoor residue spraying are unlikely to be effective as control tools against A. farauti occurring elsewhere, and if used, will probably result in peak biting time behavioural shifts similar to that observed in the Solomon Islands.

Matched MeSH terms: Anopheles/genetics*
Fulltext New vectors in northern Sarawak, Malaysian Borneo, for the zoonotic malaria parasite, Plasmodium knowlesi

Ang JXD, Kadir KA, Mohamad DSA, Matusop A, Divis PCS, Yaman K, et al.

Parasit Vectors, 2020 Sep 15;13(1):472.
PMID: 32933567 DOI: 10.1186/s13071-020-04345-2

BACKGROUND: Plasmodium knowlesi is a significant cause of human malaria in Sarawak, Malaysian Borneo. Only one study has been previously undertaken in Sarawak to identify vectors of P. knowlesi, where Anopheles latens was incriminated as the vector in Kapit, central Sarawak. A study was therefore undertaken to identify malaria vectors in a different location in Sarawak.
METHODS: Mosquitoes found landing on humans and resting on leaves over a 5-day period at two sites in the Lawas District of northern Sarawak were collected and identified. DNA samples extracted from salivary glands of Anopheles mosquitoes were subjected to nested PCR malaria-detection assays. The small subunit ribosomal RNA (SSU rRNA) gene of Plasmodium was sequenced, and the internal transcribed spacer 2 (ITS2) and mitochondrial cytochrome c oxidase subunit 1 (cox1) gene of the mosquitoes were sequenced from the Plasmodium-positive samples for phylogenetic analysis.
RESULTS: Totals of 65 anophelines and 127 culicines were collected. By PCR, 6 An. balabacensis and 5 An. donaldi were found to have single P. knowlesi infections while 3 other An. balabacensis had either single, double or triple infections with P. inui, P. fieldi, P. cynomolgi and P. knowlesi. Phylogenetic analysis of the Plasmodium SSU rRNA gene confirmed 3 An. donaldi and 3 An. balabacensis with single P. knowlesi infections, while 3 other An. balabacensis had two or more Plasmodium species of P. inui, P. knowlesi, P. cynomolgi and some species of Plasmodium that could not be conclusively identified. Phylogenies inferred from the ITS2 and/or cox1 sequences of An. balabacensis and An. donaldi indicate that they are genetically indistinguishable from An. balabacensis and An. donaldi, respectively, found in Sabah, Malaysian Borneo.
CONCLUSIONS: Previously An. latens was identified as the vector for P. knowlesi in Kapit, central Sarawak, Malaysian Borneo, and now An. balabacensis and An. donaldi have been incriminated as vectors for zoonotic malaria in Lawas, northern Sarawak.

Matched MeSH terms: Anopheles/genetics
Fulltext Genome-Wide Transcription and Functional Analyses Reveal Heterogeneous Molecular Mechanisms Driving Pyrethroids Resistance in the Major Malaria Vector Anopheles funestus Across Africa

Riveron JM, Ibrahim SS, Mulamba C, Djouaka R, Irving H, Wondji MJ, et al.

G3 (Bethesda), 2017 06 07;7(6):1819-1832.
PMID: 28428243 DOI: 10.1534/g3.117.040147

Pyrethroid resistance in malaria vector, An. funestus is increasingly reported across Africa, threatening the sustainability of pyrethroid-based control interventions, including long lasting insecticidal nets (LLINs). Managing this problem requires understanding of the molecular basis of the resistance from different regions of the continent, to establish whether it is being driven by a single or independent selective events. Here, using a genome-wide transcription profiling of pyrethroid resistant populations from southern (Malawi), East (Uganda), and West Africa (Benin), we investigated the molecular basis of resistance, revealing strong differences between the different African regions. The duplicated cytochrome P450 genes (CYP6P9a and CYP6P9b) which were highly overexpressed in southern Africa are not the most upregulated in other regions, where other genes are more overexpressed, including GSTe2 in West (Benin) and CYP9K1 in East (Uganda). The lack of directional selection on both CYP6P9a and CYP6P9b in Uganda in contrast to southern Africa further supports the limited role of these genes outside southern Africa. However, other genes such as the P450 CYP9J11 are commonly overexpressed in all countries across Africa. Here, CYP9J11 is functionally characterized and shown to confer resistance to pyrethroids and moderate cross-resistance to carbamates (bendiocarb). The consistent overexpression of GSTe2 in Benin is coupled with a role of allelic variation at this gene as GAL4-UAS transgenic expression in Drosophila flies showed that the resistant 119F allele is highly efficient in conferring both DDT and permethrin resistance than the L119. The heterogeneity in the molecular basis of resistance and cross-resistance to insecticides in An. funestus populations throughout sub-Saharan African should be taken into account in designing resistance management strategies.

Matched MeSH terms: Anopheles/genetics*