Managing invasive hybrids with pond hydroperiod manipulation in an endangered salamander system

When invasive and endangered native taxa hybridize, the resulting admixture introduces novel conservation challenges. Across a large region of central California, a hybrid swarm consisting of admixed endangered California tiger salamanders (CTS) (Ambystoma californiense) and introduced barred tiger salamanders (BTS) (Ambystoma mavortium) has replaced native populations, threatening the genetic integrity of CTS and the vernal pool systems they inhabit. We employed a large-scale, genomically informed field experiment to test whether shortening breeding pond hydroperiod would favor native CTS genotypes. We constructed 14 large, seminatural ponds to evaluate the effect of hydroperiod duration on larval survival and mass at metamorphosis. We tracked changes in non-native allele frequencies with a 5237-gene exon capture array and employed a combination of custom Bayesian and generalized linear models to quantify the effect of pond duration on salamander fitness. Earlier work on this system showed hybrid superiority under many conditions and suggested that hybrids are favored in human-modified ponds with artificially long hydroperiods. Consistent with these earlier studies, we found overwhelming evidence for hybrid superiority. Very short hydroperiods substantially reduced the mass (1.1-1.5 fold) and survival probability (10-13 fold) of both native and hybrid larvae, confirming that hydroperiod likely exerts a strong selective pressure in the wild. We identified 86 genes, representing 1.8% of 4723 screened loci, that significantly responded to this hydroperiod-driven selection. In contrast to earlier work, under our more natural experimental conditions, native CTS survival and size at metamorphosis were always less than hybrids, suggesting that hydroperiod management alone will not shift selection to favor native larval genotypes. However, shortening pond hydroperiod may limit productivity of hybrid ponds, complementing other strategies to remove hybrids while maintaining vernal pool ecosystems. This study confirms and expands on previous work that highlights the importance of hydroperiod management to control invasive aquatic species.

Comparative assessment of a novel fan box trap for collecting Anopheles farauti and culicine mosquitoes alive in tropical north Queensland, Australia

During preliminary mosquito surveys at Cowley Beach Training Area in north Queensland, Australia, it was found that the utility of the standard encephalitis virus surveillance (EVS) trap for collecting the malaria vector Anopheles farauti (Laveran) adults was compromised by the harsh tropical conditions. With the aim of increasing the survival rate of mosquitoes, we designed a downdraft fan box trap (FBT) that incorporated a screened fan at the bottom of the trap, so mosquitoes did not have to pass through a fan. The FBT was tested against the EVS and Centers for Disease Control (CDC) light traps, where mosquitoes do pass through a fan, and a nonpowered passive box trap (PBT). We conducted 4 trials to compare the quantity and survival of An. farauti and culicine mosquitoes were collected in these traps. Although not significant, the FBT collected more An. farauti than the EVS trap and PBT and significantly less An. farauti than the CDC light trap. However, the FBT improved on the CDC light trap in terms of the survival of An. farauti adults collected, with a significantly higher percentage alive in the FBT (74.6%) than in the CDC light trap (27.5%). Thus, although the FBT did not collect as many anophelines as the CDC, it proved to be superior to current trap systems for collecting large numbers of live and relatively undamaged mosquitoes. Therefore, it is recommended that FBTs be used for collecting An. farauti adults in northern Australia, especially when high survival and sample quality are important.

Natural parasites in conjunction with behavioral and color traits explain male agonistic behaviors in a lizard

Male competition conforms to a cost-benefit model, because while aggression may increase reproductive prospects, it can also increase the risk of injury. We hypothesize that an additional cost in aggressive males would be an increase in parasite load associated with a high energy investment into sexual competition. Some of these infections, in turn, may downmodulate the level of host aggression via energetic trade-offs. We staged dyadic male contests in the lab to investigate the relationships of multiple parasites with the agonistic behavior of lizard hosts, Sceloporus occidentalis. We also included both color and behavioral traits from opponents in the analyses because (1) color patches of lizards may serve as intraspecific signals used by conspecifics to assess the quality of opponents, and (2) contests between male lizards fit classical models of escalated aggression, where lizards increase aggression displays in response to an opponent's behavior. The results conform to our hypothesis because male lizards displayed more pushups when they had more ticks. Moreover, some parasites may modulate the levels of aggression because lizards infected by hematic coccidians performed fewer pushups. Interestingly, lizards also displayed fewer pushups when both the chroma and size of the opponent's blue patch were greater. The results thus also supported the role of the blue patch of S. occidentalis as a sexual armament, because it contributed to the deterrence of aggression from opponent lizards. We revealed that natural parasitic infections in lizard hosts can contribute to their agonistic behavior. We encourage future studies to account for parasites in behavioral tests with lizards.

Seasonal assessment on the effects of time of night, temperature and humidity on the biting profile of Anopheles farauti in north Queensland, Australia using a population naive to malaria vector control pressures

BACKGROUND

Anopheles farauti is one of the major vectors of malaria in the Southwest Pacific region and is responsible for past outbreaks in Australia. With an adaptable biting profile conducive to behavioural resistance to indoor residual spraying (IRS) and insecticide-treated nets (ITNs), its all-night biting behaviour can switch to biting mostly in the early evening. With limited insight into the biting profile of An. farauti populations in areas that have not encountered IRS or ITNs, the aim of this study was to develop insights on the biting behaviour of a malaria control naive population of An. farauti.

METHODS

Biting profiles of An. farauti were conducted at Cowley Beach Training Area, in north Queensland, Australia. Initially, encephalitis virus surveillance (EVS) traps were used to document the 24-h biting profile of An. farauti and then human landing collections (HLC) were used to follow the 18.00-06.00 h biting profile. The human landing catches (HLC) were performed at both the end of the wet (April) and dry (October) seasons.

RESULTS

Data exploration using a Random Forest Model shows that time of night is the most important variable for predicting An. farauti biting activity. Temperature was found to be the next important predictor, followed by humidity, trip, collector, and season. The significant effect of time of night and peak in time of night biting, between 19.00 and 20.00 h was also observed in a generalized linear model. The main effect of temperature was significant and non-linear and appears to have a positive effect on biting activity. The effect of humidity is also significant but its relationship with biting activity is more complex. This population's biting profile is similar to populations found in other parts of its range prior to insecticide intervention. A tight timing for the onset of biting was identified with more variation with the end of biting, which is likely underpinned by an endogenous circadian clock rather than any light intensity.

CONCLUSION

This study sees the first record of a relationship between biting activity and the decreasing temperature during the night for the malaria vector, Anopheles farauti.

Gene flow between island populations of the malaria mosquito, Anopheles hinesorum, may have contributed to the spread of divergent host preference phenotypes

Anopheles hinesorum is a mosquito species with variable host preference. Throughout New Guinea and northern Australia, An. hinesorum feeds on humans (it is opportunistically anthropophagic) while in the south-west Pacific's Solomon Archipelago, the species is abundant but has rarely been found biting humans (it is exclusively zoophagic in most populations). There are at least two divergent zoophagic (nonhuman biting) mitochondrial lineages of An. hinesorum in the Solomon Archipelago representing two independent dispersals. Since zoophagy is a derived (nonancestral) trait in this species, this leads to the question: has zoophagy evolved independently in these two populations? Or conversely: has nuclear gene flow or connectivity resulted in the transfer of zoophagy? Although we cannot conclusively answer this, we find close nuclear relationships between Solomon Archipelago populations indicating that recent nuclear gene flow has occurred between zoophagic populations from the divergent mitochondrial lineages. Recent work on isolated islands of the Western Province (Solomon Archipelago) has also revealed an anomalous, anthropophagic island population of An. hinesorum. We find a common shared mitochondrial haplotype between this Solomon Island population and another anthropophagic population from New Guinea. This finding suggests that there has been recent migration from New Guinea into the only known anthropophagic population from the Solomon Islands. Although currently localized to a few islands in the Western Province of the Solomon Archipelago, if anthropophagy presents a selective advantage, we may see An. hinesorum emerge as a new malaria vector in a region that is now working on malaria elimination.

Continuity of Care in a Student-Run Free Clinic: Impact on Atherosclerotic Cardiovascular Disease Risk

BACKGROUND AND OBJECTIVES

Medical student-run free clinics (SRFC) provide underserved patients access to health care. Few studies have examined the effects of specific care models implemented by these clinics. We looked at the impact of a continuity of care delivery model on chronic care outcomes at an SRFC sponsored by Ohio State University College of Medicine.

METHODS

Using the SRFC electronic medical records, we abstracted health records of patients at risk for atherosclerotic cardiovascular disease (ASCVD). We formed three study groups matched on age and gender. Group 1 were the patients enrolled in a continuity of care program, Group 2 were patients who visit the SRFC at 3-month intervals, and Group 3 were sporadic visitors. Authors compared groups' ASCVD risk score change over 12 months using a Group x Time Analysis of Variance.

RESULTS

We identified 81 subjects that met the qualifications for this study and assigned them to one of the three study groups. A Group x Time interaction showed that mean ASCVD risk scores improved significantly for continuity of care patients and regular visitor controls, but not for sporadic controls (F=3.82; df=2/1.72; P=.035; es=1.28).

CONCLUSIONS

This SRFCs continuity of care delivery had no appreciable impact on lowering ASCVD Risk scores over and above frequent regular visits to the clinic. This finding suggests that SRFCs should focus on getting their chronic patient population to maintain a schedule of frequent check-ups, without investing in continuity of care. Longer-term studies are needed to detect a continuity of care delivery model effect.

Allele-specific expression and gene regulation help explain transgressive thermal tolerance in non-native hybrids of the endangered California tiger salamander (Ambystoma californiense)

Hybridization between native and non-native species is an ongoing global conservation threat. Hybrids that exhibit traits and tolerances that surpass parental values are of particular concern, given their potential to outperform native species. Effective management of hybrid populations requires an understanding of both physiological performance and the underlying mechanisms that drive transgressive hybrid traits. Here, we explore several aspects of the hybridization between the endangered California tiger salamander (Ambystoma californiense; CTS) and the introduced barred tiger salamander (Ambystoma mavortium; BTS). We assayed critical thermal maximum (CTMax) to compare the ability of CTS, BTS and F1 hybrids to tolerate acute thermal stress, and found that hybrids exhibit a wide range of CTMax values, with 33% (4/12) able to tolerate temperatures greater than either parent. We then quantified the genomic response, measured at the RNA transcript level, of each salamander, to explore the mechanisms underlying thermal tolerance strategies. We found that CTS and BTS have strikingly different values and tissue-specific patterns of overall gene expression, with hybrids expressing intermediate values. F1 hybrids display abundant and variable degrees of allele-specific expression (ASE), likely arising from extensive compensatory evolution in gene regulatory mechanisms between CTS and BTS. We found evidence that the proportion of genes with allelic imbalance in individual hybrids correlates with their CTMax, suggesting a link between ASE and expanded thermal tolerance that may contribute to the success of hybrid salamanders in California. Future climate change may further complicate management of CTS if hybrid salamanders are better equipped to deal with rising temperatures.

Population genetics of Anopheles koliensis through Papua New Guinea: New cryptic species and landscape topography effects on genetic connectivity

New Guinea is a topographically and biogeographically complex region that supports unique endemic fauna. Studies describing the population connectivity of species through this region are scarce. We present a population and landscape genetic study on the endemic malaria-transmitting mosquito, Anopheles koliensis (Owen). Using mitochondrial and nuclear sequence data, as well as microsatellites, we show the evidence of geographically discrete population structure within Papua New Guinea (PNG). We also confirm the existence of three rDNA ITS2 genotypes within this mosquito and assess reproductive isolation between individuals carrying different genotypes. Microsatellites reveal the clearest population structure and show four clear population units. Microsatellite markers also reveal probable reproductive isolation between sympatric populations in northern PNG with different ITS2 genotypes, suggesting that these populations may represent distinct cryptic species. Excluding individuals belonging to the newly identified putative cryptic species (ITS2 genotype 3), we modeled the genetic differences between A. koliensis populations through PNG as a function of terrain and find that dispersal is most likely along routes with low topographic relief. Overall, these results show that A. koliensis is made up of geographically and genetically discrete populations in Papua New Guinea with landscape topography being important in restricting dispersal.

Smallest Anopheles farauti occur during the peak transmission season in the Solomon Islands

BACKGROUND

Malaria transmission varies in intensity amongst Solomon Island villages where Anopheles farauti is the only vector. This variation in transmission intensity might be explained by density-dependent processes during An. farauti larval development, as density dependence can impact adult size with associated fitness costs and daily survivorship.

METHODS

Adult anophelines were sampled from six villages in Western and Central Provinces, Solomon Islands between March 2014 and February 2017. The size of females was estimated by measuring wing lengths, and then analysed for associations with biting densities and rainfall.

RESULTS

In the Solomon Islands, three anopheline species, An. farauti, Anopheles hinesorum and Anopheles lungae, differed in size. The primary malaria vector, An. farauti, varied significantly in size among villages. Greater rainfall was directly associated with higher densities of An. farauti biting rates, but inversely associated with body size with the smallest mean sized mosquitoes present during the peak transmission period. A measurable association between body size and survivorship was not found.

CONCLUSIONS

Density dependent effects are likely impacting the size of adult An. farauti emerging from a range of larval habitats. The data suggest that rainfall increases An. farauti numbers and that these more abundant mosquitoes are significantly smaller in size, but without any reduced survivorship being associated with smaller size. The higher malaria transmission rate in a high malaria focus village appears to be determined more by vector numbers than size or survivorship of the vectors.

Spatial-temporal heterogeneity in malaria receptivity is best estimated by vector biting rates in areas nearing elimination

BACKGROUND

Decisions on when vector control can be withdrawn after malaria is eliminated depend on the receptivity or potential of an area to support vector populations. To guide malaria control and elimination programmes, the potential of biting rates, sporozoite rates, entomological inoculation rates and parity rates to estimate malaria receptivity and transmission were compared within and among geographically localised villages of active transmission in the Western Province of the Solomon Islands.

RESULTS

Malaria transmission and transmission potential was heterogeneous in both time and space both among and within villages as defined by anopheline species composition and biting densities. Biting rates during the peak biting period (from 18:00 to 00:00 h) of the primary vector, Anopheles farauti, ranged from less than 0.3 bites per person per half night in low receptivity villages to 26 bites per person in highly receptive villages. Within villages, sites with high anopheline biting rates were significantly clustered. Sporozoite rates provided evidence for continued transmission of Plasmodium falciparum, P. vivax and P. ovale by An. farauti and for incriminating An. hinesorum, as a minor vector, but were unreliable as indicators of transmission intensity.

CONCLUSIONS

In the low transmission area studied, sporozoite, entomological inoculation and parity rates could not be measured with the precision required to provide guidance to malaria programmes. Receptivity and potential transmission risk may be most reliably estimated by the vector biting rate. These results support the meaningful design of operational research programmes to ensure that resources are focused on providing information that can be utilised by malaria control programmes to best understand both transmission, transmission risk and receptivity across different areas.

Multiple color patches and parasites in Sceloporus occidentalis: differential relationships by sex and infection

Parasites generally have a negative influence on the color expression of their hosts. Sexual selection theory predicts resistant high-quality individuals should show intense coloration, whereas susceptible low-quality individuals would show poor coloration. However, intensely colored males of different species of Old and New World lizards were more often infected by hemoparasites. These results suggest that high-quality males, with intense coloration, would suffer higher susceptibility to hemoparasites. This hypothesis remains poorly understood and contradicts general theories on sexual selection. We surveyed a population of Sceloporus occidentalis for parasites and found infections by the parasite genera Lankesterella and Acroeimeria. In this population, both males and females express ventral blue and yellow color patches. Lankesterella was almost exclusively infecting males. The body size of the males significantly predicted the coloration of both blue and yellow patches. Larger males showed darker (lower lightness) blue ventral patches and more saturated yellow patches that were also orange-skewed. Moreover, these males were more often infected by Lankesterella than smaller males. The intestinal parasite Acroeimeria infected both males and females. The infection by intestinal parasites of the genus Acroeimeria was the best predictor for the chroma in the blue patch of the males and for hue in the yellow patch of the females. Those males infected by Acroeimeria expressed blue patches with significantly lower chroma than the uninfected males. However, the hue of the yellow patch was not significantly different between infected and uninfected females. These results suggest a different effect of Lankesterella and Acroeimeria on the lizards. On the one hand, the intense coloration of male lizards infected by Lankesterella suggested high-quality male lizards may tolerate it. On the other hand, the low chroma of the blue coloration of the infected males suggested that this coloration could honestly express the infection by Acroeimeria.

Larval habitats of the Anopheles farauti and Anopheles lungae complexes in the Solomon Islands

BACKGROUND

There is an urgent need for vector control tools to supplement long-lasting insecticidal nets (LLINs) and indoor residual spraying; particularly in the Solomon Islands where the primary vector, Anopheles farauti, is highly anthropophagic and feeds mainly outdoors and early in the evening. Currently, the only supplementary tool recommended by the World Health Organization is larval source management (LSM). The feasibility and potential effectiveness of LSM requires information on the distribution of anophelines, the productivity of larval habitats and the potential impacts of larval control on adult fitness.

METHODS

The distribution of anophelines in Central and Western Provinces in the Solomon Islands was mapped from cross-sectional larval habitat surveys. The composition and micro-distribution of larval instars within a large permanent river-mouth lagoon was examined with a longitudinal survey. Density-dependent regulation of An. farauti larvae was investigated by longitudinally following the development and survival of different densities of first instars in floating cages in a river-mouth lagoon.

RESULTS

Five anopheline species were molecularly identified from a range of fresh and brackish water habitats: An. farauti s.s., An. hinesorum, An. lungae, An. nataliae and An. solomonis. The most common habitats used by the primary malaria vector, An. farauti, were coastal lagoons and swamps. In the detailed study of lagoon micro-productivity, An. farauti was non-uniformly distributed with highest densities found at collections sites most proximal and distal to the mouth of the lagoon. The survival of An. farauti larvae was more than twofold lower when larvae were held at the highest experimental density (1 larva per 3.8 cm(2)) when compared with the lowest density (1 larva per 38 cm(2)).

CONCLUSIONS

The only documented major malaria vector collected in larval surveys in both Central and Western Provinces was An. farauti. Lagoons and swamps, the most common, largest and (potentially) most productive larval sites of this malaria vector, were "few, fixed and findable" and theoretically, therefore, amenable to successful LSM. However, the immense scale and complexity of these ecosystems in which An. farauti larvae are found raises questions regarding the ability to effectively control the larvae, as incomplete larviciding could trigger density dependent effects resulting in increased larval survivorship. While LSM has the potential to significantly contribute to malaria control of this early and outdoor biting vector, more information on the distribution of larvae within these extensive habitats is required to maximize the effectiveness of LSM.

Determinants of host feeding success by Anopheles farauti

BACKGROUND

The proportion of blood meals that mosquitoes take from a host species is a function of the interplay of extrinsic (abundance and location of potential hosts) and intrinsic (innate preference) factors. A mark-release-recapture experiment addressed whether host preference in a population of Anopheles farauti was uniform or if there were anthropophilic and zoophilic subpopulations. The corresponding fitness associated with selecting different hosts for blood meals was compared by measuring fecundity.

METHODS

The attractiveness of humans for blood meals by An. farauti in the Solomon Islands was compared to pigs using tent traps. Host fidelity was assessed by mark-release-recapture experiments in which different colour dusts were linked to the host to which the mosquito was first attracted. Outdoor resting An. farauti were captured on barrier screens and the human blood index (HBI) as well as the feeding index were calculated. The fecundity of individual An. farauti after feeding on either humans or pigs was assessed from blood-fed mosquitoes held in individual oviposition chambers.

RESULTS

Anopheles farauti were more attracted to humans than pigs at a ratio of 1.31:1.00. The mark-release-recapture experiment found evidence for An. farauti being a single population regarding host preference. The HBI of outdoor resting An. farauti was 0.93 and the feeding index was 1.29. Anopheles farauti that fed on a human host laid more eggs but had a longer oviposition time compared to An. farauti that had blood fed on a pig.

CONCLUSIONS

One of the strongest drivers for host species preference was the relative abundance of the different host species. Here, An. farauti have a slight preference for humans over pigs as blood meal sources. However, the limited availability of alternative hosts relative to humans in the Solomon Islands ensures a very high proportion of blood meals are obtained from humans, and thus, the transmission potential of malaria by An. farauti is high.

Frequent blood feeding enables insecticide-treated nets to reduce transmission by mosquitoes that bite predominately outdoors

BACKGROUND

The effectiveness of vector control on malaria transmission by long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) depends on the vectors entering houses to blood feed and rest when people are inside houses. In the Solomon Islands, significant reductions in malaria have been achieved in the past 20 years with insecticide-treated bed nets, IRS, improved diagnosis and treatment with artemisinin combination therapies; despite the preference of the primary vector, Anopheles farauti, to feed outdoors and early in the evening and thereby avoid potential exposure to insecticides. Rational development of tools to complement LLINs and IRS by attacking vectors outdoor requires detailed knowledge of the biology and behaviours of the target species.

METHODS

Malaria transmission in Central Province, Solomon Islands was estimated by measuring the components comprising the entomological inoculation rate (EIR) as well as the vectorial capacity of An. farauti. In addition, the daily and seasonal biting behaviour of An. farauti, was examined and the duration of the feeding cycle was estimated with a mark-release-recapture experiment.

RESULTS

Anopheles farauti was highly exophagic with 72% captured by human landing catches (HLC) outside of houses. Three-quarters (76%) of blood feeding on humans was estimated to occur before 21.00 h. When the hourly location of humans was considered, the proportion of exposure to mosquito bites on humans occurring indoors (πi) was only 0.130 ± 0.129. Peak densities of host seeking An. farauti occurred between October and January. The annual EIR was estimated to be 2.5 for 2012 and 33.2 for 2013. The length of the feeding cycle was 2.1 days.

CONCLUSIONS

The short duration of the feeding cycle by this species offers an explanation for the substantial control of malaria that has been achieved in the Solomon Islands by LLINs and IRS. Anopheles farauti is primarily exophagic and early biting, with 13% of mosquitoes entering houses to feed late at night during each feeding cycle. The two-day feeding cycle of An. farauti requires females to take 5-6 blood meals before the extrinsic incubation period (EIP) is completed; and this could translate into substantial population-level mortality by LLINs or IRS before females would be infectious to humans with Plasmodium falciparum and Plasmodium vivax. Although An. farauti is primarily exophagic, the indoor vector control tools recommended by the World Health Organization (LLINs and IRS) can still provide an important level of control. Nonetheless, elimination will likely require vector control tools that target other bionomic vulnerabilities to suppress transmission outdoors and that complement the control provided by LLINs and IRS.

Anopheles farauti is a homogeneous population that blood feeds early and outdoors in the Solomon Islands

BACKGROUND

In the 1970s, Anopheles farauti in the Solomon Island responded to indoor residual spraying with DDT by increasingly feeding more outdoors and earlier in the evening. Although long-lasting insecticidal nets (LLINs) are now the primary malaria vector control intervention in the Solomon Islands, only a small proportion of An. farauti still seek blood meals indoors and late at night where they are vulnerable to being killed by contract with the insecticides in LLINs. The effectiveness of LLINs and indoor residual spraying (IRS) in controlling malaria transmission where the vectors are exophagic and early biting will depend on whether the predominant outdoor or early biting phenotypes are associated with a subpopulation of the vectors present.

METHODS

Mark-release-recapture experiments were conducted in the Solomon Islands to determine if individual An. farauti repeat the same behaviours over successive feeding cycles. The two behavioural phenotypes examined were those on which the WHO recommended malaria vector control strategies, LLINs and IRS, depend: indoor and late night biting.

RESULTS

Evidence was found for An. farauti being a single population regarding time (early evening or late night) and location (indoor or outdoor) of blood feeding. Individual An. farauti did not consistently repeat behavioural phenotypes expressed for blood feeding (e.g., while most mosquitoes that fed early and outdoors, and would repeat those behaviours, some fed late at night or indoors in the next feeding cycle).

CONCLUSIONS

The finding that An. farauti is a homogeneous population is significant, because during the multiple feeding cycles required to complete the extrinsic incubation period, many individual female anophelines will enter houses late at night and be exposed to the insecticides used in LLINs or IRS. This explains, in part, the control that LLINs and IRS have exerted against a predominantly outdoor feeding vector, such as An. farauti. These findings may be relevant to many of the outdoor feeding vectors that dominate transmission in much of the malaria endemic world and justifies continued use of LLINs. However, the population-level tendency of mosquitoes to feed outdoors and early in the evening does require complementary interventions to accelerate malaria control towards elimination.

Anopheles punctulatus group: evolution, distribution, and control

The major malaria vectors of the Southwest Pacific belong to a group of closely related mosquitoes known as the Anopheles punctulatus group. The group comprises 13 co-occurring species that either are isomorphic or carry overlapping morphological features, and today several species remain informally named. The advent of species-diagnostic molecular tools in the 1990s permitted a new raft of studies into the newly differentiated mosquitoes of this group, and these have revealed five species as the region's primary malaria vectors: An. farauti, An. hinesorum, An. farauti 4, An. koliensis, and An. punctulatus. Species' distributions are now well established across Papua New Guinea, northern Australia, and the Solomon Archipelago, but little has been documented thus far in eastern Indonesia. As each species reveals significant differences in distribution and biology, the relative paucity of knowledge of their biology or ecology in relation to malaria transmission is brought into clearer focus. Only three of the species have undergone some form of spatial or population genetics analyses, and this has revealed striking differences in their genetic signatures throughout the region. This review compiles and dissects the key findings for this important mosquito group and points to where future research should focus to maximize the output of field studies in developing relevant knowledge on these malaria vectors.

Microsatellite and mitochondrial markers reveal strong gene flow barriers for Anopheles farauti in the Solomon Archipelago: implications for malaria vector control

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.

The bionomics of the malaria vector Anopheles farauti in Northern Guadalcanal, Solomon Islands: issues for successful vector control

BACKGROUND

The north coast of Guadalcanal has some of the most intense malaria transmission in the Solomon Islands. And, there is a push for intensified vector control in Guadalcanal, to improve the livelihood of residents and to minimize the number of cases, which are regularly exported to the rest of the country. Therefore, the bionomics of the target vector, Anopheles farauti, was profiled in 2007-08; which was after 20 years of limited surveillance during which time treated bed nets (ITNs) were distributed in the area.

METHODS

In three villages on northern Guadalcanal, blood-seeking female mosquitoes were caught using hourly human landing catches by four collectors, two working indoors and two outdoors, from 18.00-06.00 for at least two nights per month from July 2007 to June 2008. The mosquitoes were counted, identified using morphological and molecular markers and dissected to determine parity.

RESULTS

Seasonality in vector densities was similar in the three villages, with a peak at the end of the drier months (October to December) and a trough at the end of the wetter months (March to May). There was some variability in endophagy (indoor biting) and nocturnal biting (activity during sleeping hours) both spatially and temporally across the longitudinal dataset. The general biting pattern was consistent throughout all sample collections, with the majority of biting occurring outdoors (64%) and outside of sleeping hours (65%). Peak biting was 19.00-20.00. The proportion parous across each village ranged between 0.54-0.58. Parity showed little seasonal trend despite fluctuations in vector densities over the year.

CONCLUSION

The early, outdoor biting behaviour of An. farauti documented 20 years previously on north Guadalcanal was still exhibited. It is possible that bed net use may have maintained this biting profile though this could not be determined unequivocally. The longevity of these populations has not changed despite long-term ITN use. This early, outdoor biting behaviour led to the failure of the eradication programme and is likely responsible for the continued transmission in Guadalcanal following the introduction of ITNs. Other vector control strategies which do not rely on the vector entering houses are needed if elimination or intensified control is to be achieved.

Long-term insecticidal activity and physical integrity of Olyset nets in Tafea Province, Vanuatu

The long-term efficacy of long-lasting insecticidal nets (LLINs) depends on both the physical condition of the net and the residual activity of the insecticide. This study focused on monitoring these parameters in Olyset nets (Sumitomo Chemical Co., Osaka, Japan) (n = 101) that had been used for 1-3 yr in Tafea Province, Vanuatu. Net usage and frequency of washing was ascertained by questionnaire; the nets were assessed with regards to cleanliness and damage owing to holes. Insecticide efficacy was determined with cone bioassays using Anophelesfarauti Laveran. Net usage was high and 86.1% (87 of 101) of villages stated that they used the net every night. Washing of nets was low (11.9%, 12 of 101), and most nets (79.2%, 80 of 101) were considered dirty. Most nets were damaged (73.4% had holes), and 22.8% (23 of 101) had large holes (>200 cm2). The 24-h mortality of An. farauti exposed to nets aged 1-2 yr was 79.4%, while the mortality for nets 3 yr of age was significantly lower at 73.7%. There was no difference in the insecticidal activity of clean compared with dirty nets (mean 24-h mortality: Clean = 76.7%, Dirty = 77.1%). Although the majority of nets had holes, the physical condition of 8.9-22.8% of nets was altered so severely to potentially affect efficacy. Although the 3-yr-old nets would still be providing significant levels of insecticidal and personal protection, consideration should be given to replacing nets >3 yr old.

Multilocus population genetic analysis of the Southwest Pacific malaria vector Anopheles punctulatus

The population structure and history of the cryptic malaria vector species, Anopheles punctulatus (Doenitz), was investigated throughout Papua New Guinea and the Solomon Islands with the aim of detailing genetic subdivisions and the potential for movement through this biogeographically complex region. We obtained larval collections from over 80 sites and utilised a diverse array of molecular markers that evolve through different processes. Individuals were initially identified to species and genotyped using the ribosomal DNA second internal transcribed spacer. DNA sequencing of a single copy nuclear ribosomal protein S9 and the mitochondrial cytochrome oxidase I loci were then investigated and 12 nuclear microsatellite markers were developed and analysed. Our data revealed three genetically distinct populations--one in Papua New Guinea, the second on Buka Island (Bougainville Province, Papua New Guinea), and the third on Guadalcanal Island (Solomon Islands). Genetic differentiation within Papua New Guinea was much lower than that found in studies of other closely related species in the region. The data does suggest that A. punctulatus has undergone a population bottleneck followed by a recent population and range expansion in Papua New Guinea. Humans and regional economic growth may be facilitating this population expansion, as A. punctulatus is able to rapidly occupy human modified landscapes and traverse unsealed roads. We therefore anticipate extensive movement of this species through New Guinea--particularly into the highlands, with a potential increase in malaria frequency in a warming climate--as well as relatively unrestricted gene flow of advantageous alleles that may confound vector control efforts.

Evidence of maternal effects on temperature preference in side-blotched lizards: implications for evolutionary response to climate change

Natural populations respond to selection pressures like increasing local temperatures in many ways, including plasticity and adaptation. To predict the response of ectotherms like lizards to local temperature increase, it is essential to estimate phenotypic variation in and determine the heritability of temperature-related traits like average field body temperature (T_b) and preferred temperature (T_p). We measured T_p of Uta stansburiana in a laboratory thermal gradient and assessed the contribution of sex, reproductive status and throat color genotype to phenotypic variation in T_b of adult lizards. Females had higher T_p than males. However, they temporarily preferred lower temperature when gravid than when nongravid. Using a nested half-sib design for genetic crosses in the laboratory, we estimated relative contributions of additive genetic variation and maternal effects to T_p of hatchlings. Our results show that maternal effects, but not additive genetic variation, influence T_p of hatchlings in U. stansburiana. Maternal T_p and the presence or absence of blue throat color alleles significantly influenced T_p of hatchlings. We discuss ecological and evolutionary consequences of these maternal effects in the context of rapid climate change and natural selection that we measure on progeny survival to maturity as a function of maternal T_p.

Successful malaria elimination strategies require interventions that target changing vector behaviours

BACKGROUND

The ultimate long-term goal of malaria eradication was recently placed back onto the global health agenda. When planning for this goal, it is important to remember why the original Global Malaria Eradication Programme (GMEP), conducted with DDT-based indoor residual spraying (IRS), did not achieve its goals. One of the technical reasons for the failure to eliminate malaria was over reliance on a single intervention and subsequently the mosquito vectors developed behavioural resistance so that they did not come into physical contact with the insecticide. HYPOTHESIS AND HOW TO TEST IT: Currently, there remains a monolithic reliance on indoor vector control. It is hypothesized that an outcome of long-term, widespread control is that vector populations will change over time, either in the form of physiological resistance, changes in the relative species composition or behavioural resistance. The potential for, and consequences of, behavioural resistance was explored by reviewing the literature regarding vector behaviour in the southwest Pacific.

DISCUSSION

Here, two of the primary vectors that were highly endophagic, Anopheles punctulatus and Anopheles koliensis, virtually disappeared from large areas where DDT was sprayed. However, high levels of transmission have been maintained by Anopheles farauti, which altered its behaviour to blood-feed early in the evening and outdoors and, thereby, avoiding exposure to the insecticides used in IRS. This example indicates that the efficacy of programmes relying on indoor vector control (IRS and long-lasting, insecticide-treated nets [LLINs]) will be significantly reduced if the vectors change their behaviour to avoid entering houses.

CONCLUSIONS

Behavioural resistance is less frequently seen compared with physiological resistance (where the mosquito contacts the insecticide but is not killed), but is potentially more challenging to control programmes because the intervention effectiveness cannot be restored by rotating the insecticide to one with a different mode of action. The scientific community needs to urgently develop systematic methods for monitoring behavioural resistance and then to work in collaboration with vector control programmes to implement monitoring in sentinel sites. In situations where behavioural resistance is detected, there will be a need to target other bionomic vulnerabilities that may exist in the larval stages, during mating, sugar feeding or another aspect of the life cycle of the vector to continue the drive towards elimination.

Barrier screens: a method to sample blood-fed and host-seeking exophilic mosquitoes

Background

Determining the proportion of blood meals on humans by outdoor-feeding and resting mosquitoes is challenging. This is largely due to the difficulty of finding an adequate and unbiased sample of resting, engorged mosquitoes to enable the identification of host blood meal sources. This is particularly difficult in the south-west Pacific countries of Indonesia, the Solomon Islands and Papua New Guinea where thick vegetation constitutes the primary resting sites for the exophilic mosquitoes that are the primary malaria and filariasis vectors.

Methods

Barrier screens of shade-cloth netting attached to bamboo poles were constructed between villages and likely areas where mosquitoes might seek blood meals or rest. Flying mosquitoes, obstructed by the barrier screens, would temporarily stop and could then be captured by aspiration at hourly intervals throughout the night.

Results

In the three countries where this method was evaluated, blood-fed females of Anopheles farauti, Anopheles bancroftii, Anopheles longirostris, Anopheles sundaicus, Anopheles vagus, Anopheles kochi, Anopheles annularis, Anopheles tessellatus, Culex vishnui, Culex quinquefasciatus and Mansonia spp were collected while resting on the barrier screens. In addition, female Anopheles punctulatus and Armigeres spp as well as male An. farauti, Cx. vishnui, Cx. quinquefasciatus and Aedes species were similarly captured.

Conclusions

Building barrier screens as temporary resting sites in areas where mosquitoes were likely to fly was an extremely time-effective method for collecting an unbiased representative sample of engorged mosquitoes for determining the human blood index.

Population structure, mitochondrial polyphyly and the repeated loss of human biting ability in anopheline mosquitoes from the southwest Pacific

Australia and New Guinea contain high levels of endemism and biodiversity, yet there have been few evaluations of population-level genetic diversity in fauna occurring throughout the Australo-Papuan region. Using extensive geographical sampling, we examined and compared the phylogenetic relationships, phylogeography and population structure of Anopheles farauti, An. hinesorum and An. irenicus throughout their ranges in the southwest Pacific using mitochondrial (mtDNA COI) and nuclear (ribosomal protein S9 and ribosomal DNA ITS2) loci. Phylogenetic analyses suggest that the ability to utilize humans as hosts has been lost repeatedly, coincident with independent colonizations of the Solomon Islands. As some of the species under investigation transmit malaria in the region, this is a medically important finding. Maximum likelihood and Bayesian phylogenetic analyses of nuclear loci also showed that the three species are monophyletic. However, putative introgression of An. hinesorum mtDNA onto a nuclear background of An. farauti was evident in populations from Queensland, Torres Strait and southern New Guinea. Haplotype networks and pairwise F(ST) values show that there is significant genetic structure within New Guinea and Australia in both An. farauti and An. hinesorum, consistent with a long-term history of low gene flow among populations.

Changes in vector species composition and current vector biology and behaviour will favour malaria elimination in Santa Isabel Province, Solomon Islands

BACKGROUND

In 2009, Santa Isabel Province in the Solomon Islands embarked on a malaria elimination programme. However, very little is known in the Province about the anopheline fauna, which species are vectors, their bionomics and how they may respond to intensified intervention measures. The purpose of this study was to provide baseline data on the malaria vectors and to ascertain the possibility of successfully eliminating malaria using the existing conventional vector control measures, such as indoor residual spraying (IRS) and long-lasting insecticidal nets (LLIN).

METHODS

Entomological surveys were undertaken during October 2009. To determine species composition and distribution larval surveys were conducted across on the whole island. For malaria transmission studies, adult anophelines were sampled using human landing catches from two villages - one coastal and one inland.

RESULTS

Five Anopheles species were found on Santa Isabel: Anopheles farauti, Anopheles hinesorum, Anopheles lungae, Anopheles solomonis, and Anopheles nataliae. Anopheles hinesorum was the most widespread species. Anopheles farauti was abundant, but found only on the coast. Anopheles punctulatus and Anopheles koliensis were not found. Anopheles farauti was the only species found biting in the coastal village, it was incriminated as a vector in this study; it fed early in the night but equally so indoors and outdoors, and had a low survival rate. Anopheles solomonis was the main species biting humans in the inland village, it was extremely exophagic, with low survival rates, and readily fed on pigs.

CONCLUSION

The disappearance of the two major vectors, An. punctulatus and An. koliensis, from Santa Isabel and the predominance of An. hinesorum, a non-vector species may facilitate malaria elimination measures. Anopheles farauti was identified as the main coastal vector with An. solomonis as a possible inland vector. The behaviour of An. solomonis is novel as it has not been previously found biting humans in any numbers. Both species appear to be short-lived, a characteristic that will limit their transmission potential. The early night feeding behaviour and a degree of outdoor biting seen in An. farauti and particularly in An. solomonis will require that their response to IRS and LLIN be closely monitored. In coastal villages, where large, favourable breeding sites allow for high numbers of An. farauti may require the addition of larval control to achieve elimination.

Bionomics of the malaria vector Anopheles farauti in Temotu Province, Solomon Islands: issues for malaria elimination

BACKGROUND

In the Solomon Islands, the Malaria Eradication Programmes of the 1970s virtually eliminated the malaria vectors: Anopheles punctulatus and Anopheles koliensis, both late night biting, endophagic species. However, the vector, Anopheles farauti, changed its behaviour to bite early in the evening outdoors. Thus, An. farauti mosquitoes were able to avoid insecticide exposure and still maintain transmission. Thirty years on and the Solomon Islands are planning for intensified malaria control and localized elimination; but little is currently known about the behaviour of the vectors and how they will respond to intensified control.

METHODS

In the elimination area, Temotu Province, standard entomological collection methods were conducted in typical coastal villages to determine the vector, its ecology, biting density, behaviour, longevity, and vector efficacy. These vector surveys were conducted pre-intervention and post-intervention following indoor residual spraying and distribution of long-lasting insecticidal nets.

RESULTS

Anopheles farauti was the only anopheline in Temotu Province. In 2008 (pre-intervention), this species occurred in moderate to high densities (19.5-78.5 bites/person/night) and expressed a tendency to bite outdoors, early in the night (peak biting time 6-8 pm). Surveys post intervention showed that there was little, if any, reduction in biting densities and no reduction in the longevity of the vector population. After adjusting for human behaviour, indoor biting was reduced from 57% pre-intervention to 40% post-intervention.

CONCLUSION

In an effort to learn from historical mistakes and develop successful elimination programmes, there is a need for implementing complimentary vector control tools that can target exophagic and early biting vectors. Intensified indoor residual spraying and long-lasting insecticide net use has further promoted the early, outdoor feeding behaviour of An. farauti in the Solomon Islands. Consequently, the effectiveness of IRS and the personal protection provided by bed nets is compromised. To achieve elimination, any residual transmission should be targeted using integrated vector control incorporating complementary tools such as larviciding and/or zooprophylaxis.

Incomplete concerted evolution and reproductive isolation at the rDNA locus uncovers nine cryptic species within Anopheles longirostris from Papua New Guinea

Background

Nuclear ribosomal DNA (rDNA) genes and transcribed spacers are highly utilized as taxonomic markers in metazoans despite the lack of a cohesive understanding of their evolution. Here we follow the evolution of the rDNA second internal transcribed spacer (ITS2) and the mitochondrial DNA cytochrome oxidase I subunit in the malaria mosquito Anopheles longirostris from Papua New Guinea (PNG). This morphospecies inhabits a variety of ecological environments indicating that it may comprise a complex of morphologically indistinguishable species. Using collections from over 70 sites in PNG, the mtDNA was assessed via direct DNA sequencing while the ITS2 was assessed at three levels - crude sequence variation through restriction digest, intragenomic copy variant organisation (homogenisation) through heteroduplex analysis and DNA sequencing via cloning.

Results

Genetic evaluation of over 300 individuals revealed that A. longirostris comprises eight ITS2 PCR-RFLP genotypes and nine ITS2 heteroduplex genotypes showing distinct copy variant organization profiles after PCR amplification. Seven of these nine genotypes were found to be sympatric with other genotypes. Phylogenetic analysis of cloned ITS2 PCR products and mtDNA COI confirmed all nine clades with evidence of reproductive isolation at the rDNA locus. Compensatory base changes in the ITS2 secondary structure or in pseudoknots were absent when closely related species were assessed. Individuals from each ITS2 genotype showed the same copy variant heteroduplex profile suggesting that the rDNA array is fixed within each genotype.

Conclusion

The centromere-proximal position of the rDNA array in Anopheles mosquitoes has probably reduced interchromosomal recombination leaving intrachromosomal events responsible for the observed pattern of concerted evolution we see in these mosquitoes. The stability of these intragenomic ITS2 copy variants within individuals and interbreeding populations suggests that rDNA is moving as a single evolutionary unit through natural populations to fixation and has provided a complementary diagnostic tool to the restriction digest for studying genetic discontinuities and species boundaries. In this, the utility of the ITS2 as a universal taxonomic marker is probably contingent on several factors pertaining to spacer dimensions and the genomic location of the rDNA array with respect to recombination and proximity to regions potentially under selection.

Vectors and malaria transmission in deforested, rural communities in north-central Vietnam

BACKGROUND

Malaria is still prevalent in rural communities of central Vietnam even though, due to deforestation, the primary vector Anopheles dirus is uncommon. In these situations little is known about the secondary vectors which are responsible for maintaining transmission. Basic information on the identification of the species in these rural communities is required so that transmission parameters, such as ecology, behaviour and vectorial status can be assigned to the appropriate species.

METHODS

In two rural villages--Khe Ngang and Hang Chuon--in Truong Xuan Commune, Quang Binh Province, north central Vietnam, a series of longitudinal entomological surveys were conducted during the wet and dry seasons from 2003-2007. In these surveys anopheline mosquitoes were collected in human landing catches, paired human and animal bait collections, and from larval surveys. Specimens belonging to species complexes were identified by PCR and sequence analysis, incrimination of vectors was by detection of circumsporozoite protein using an enzyme-linked immunosorbent assay.

RESULTS

Over 80% of the anopheline fauna was made up of Anopheles sinensis, Anopheles aconitus, Anopheles harrisoni, Anopheles maculatus, Anopheles sawadwongporni, and Anopheles philippinensis. PCR and sequence analysis resolved identification issues in the Funestus Group, Maculatus Group, Hyrcanus Group and Dirus Complex. Most species were zoophilic and while all species could be collected biting humans significantly higher densities were attracted to cattle and buffalo. Anopheles dirus was the most anthropophilic species but was uncommon making up only 1.24% of all anophelines collected. Anopheles sinensis, An. aconitus, An. harrisoni, An. maculatus, An. sawadwongporni, Anopheles peditaeniatus and An. philippinensis were all found positive for circumsporozoite protein. Heterogeneity in oviposition site preference between species enabled vector densities to be high in both the wet and dry seasons allowing for year round transmission.

CONCLUSIONS

In rural communities in north central Vietnam, malaria transmission was maintained by a number of anopheline species which though collected feeding on humans were predominantly zoophilic, this behaviour allows for low level but persistent malaria transmission. The important animal baits--cattle and buffalo--were kept in the village and barrier spraying around these animals may be more effective at reducing vector densities and longevity than the currently used indoor residual spraying.

Field evaluation of deet against Anopheles farauti at Ndendo (Santa Cruz) Island, Solomon Islands

Field efficacy studies comparing two formulations of deet (N,N-diethyl-3-methylbenzamide) against mosquitoes were conducted on Ndendo Island, Solomon Islands. The repellent study was conducted at Pala village in November 2008, and the only mosquito species collected was Anopheles farauti Laveran. A formulation containing 35% deet in a gel provided >95% protection for 2 h, whereas a formulation containing 40% deet in ethanol in a spray applicator provided >95% for only 1 h. This field study demonstrated again that repellents containing deet provide a relatively short period of complete protection against Anopheles spp.

Malaria vectors of Timor-Leste

BACKGROUND

The island of Timor lies at the south-eastern edge of Indonesia on the boundary of the Oriental and Australian faunal regions. The country of Timor-Leste, which occupies the eastern part of the island, is malarious, but anopheline faunal surveys and malaria vector incrimination date back to the 1960 s. Over the last decade the malaria vectors of south-east Asia and the south-west Pacific have been intensely studied using molecular techniques that can confirm identification within complexes of isomorphic species. The aim of this study is to accurately identify the Anopheles fauna of Timor-Leste using these techniques.

METHODS

The survey was carried out over the period February to June 2001. Standard entomological techniques--human landing collections, larval collections and CO2 baited light traps--were used to collect anophelines from the main geographical regions: coastal plains, inland plains, and highlands. Specimens were processed for identification by morphology and genotyped for the ribosomal DNA ITS2 by restriction analysis and/or DNA sequencing. Phylogenetic relationship of Anopheles sundaicus and Anopheles subpictus individuals was also assessed using DNA sequences from the ITS2 and mitochondrial cytochrome-b. All specimens, other than those from larval surveys, were processed to detect the presence of the Plasmodium parasite circumsporozoite protein by ELISA for vector incrimination.

RESULTS

Of 2,030 specimens collected, seven species were identified by morphology: Anopheles barbirostris, Anopheles aconitus, Anopheles annularis, Anopheles maculatus, Anopheles peditaeniatus, An. sundaicus and Anopheles vagus. These were confirmed by molecular analysis with the addition of Anopheles flavirostris and an unidentified species designated here as An. vagus genotype B. This latter species was morphologically similar to An. vagus and An. subpictus and is likely to be the An. subpictus described by other workers for Timor. However, genetically this species showed strong affinities to the An. sundaicus complex. Anopheles vagus was the most common species but was rarely collected coming to bite humans; An. barbirostris and An. vagus genotype B were the two most common species collected in human landing catches and both were found positive for CS protein.

CONCLUSIONS

The anopheline fauna of Timor-Leste is of Oriental origin with no evidence of elements from the Australian Region. The existence of species complexes will make the use of morphological markers problematic in the country. Using molecular analysis a number of issues regarding the anopheline fauna of Timor-Leste were resolved and nine putative species of Anopheles were identified; two species: An. barbirostris and An. vagus genotype B, were incriminated as malaria vectors.

Malaria vectors of Papua New Guinea

Understanding malaria transmission in Papua New Guinea (PNG) requires exact knowledge of which Anopheles species are transmitting malaria and is complicated by the cryptic species status of many of these mosquitoes. To identify the malaria vectors in PNG we studied Anopheles specimens from 232 collection localities around human habitation throughout PNG (using CO(2) baited light traps and human bait collections). A total of 22,970mosquitoes were individually assessed using a Plasmodium sporozoite enzyme-linked immunosorbent assay to identify Plasmodiumfalciparum, Plasmodiumvivax and Plasmodiummalariae circumsporozoite proteins. All mosquitoes were identified to species by morphology and/or PCR. Based on distribution, abundance and their ability to develop sporozoites, we identified five species as major vectors of malaria in PNG. These included: Anophelesfarauti, Anopheleshinesorum (incriminated here, to our knowledge, for the first time), Anophelesfarauti 4, Anopheleskoliensis and Anophelespunctulatus. Anopheleslongirostris and Anophelesbancroftii were also incriminated in this study. Surprisingly, An. longirostris showed a high incidence of infections in some areas. A newly identified taxon within the Punctulatus Group, tentatively called An. farauti 8, was also found positive for circumsporozoite protein. These latter three species, together with Anopheleskarwari and Anophelessubpictus, incriminated in other studies, appear to be only minor vectors, while Anophelesfarauti 6 appears to be the major vector in the highland river valleys (>1500m above sea level). The nine remaining Anopheles species found in PNG have been little studied and their bionomics are unknown; most appear to be uncommon with limited distribution and their possible role in malaria transmission has yet to be determined.

Australia's dengue risk driven by human adaptation to climate change

Background

The reduced rainfall in southeast Australia has placed this region's urban and rural communities on escalating water restrictions, with anthropogenic climate change forecasts suggesting that this drying trend will continue. To mitigate the stress this may place on domestic water supply, governments have encouraged the installation of large domestic water tanks in towns and cities throughout this region. These prospective stable mosquito larval sites create the possibility of the reintroduction of Ae. aegypti from Queensland, where it remains endemic, back into New South Wales and other populated centres in Australia, along with the associated emerging and re-emerging dengue risk if the virus was to be introduced.

Methodology/Principal Findings

Having collated the known distribution of Ae. aegypti in Australia, we built distributional models using a genetic algorithm to project Ae. aegypti's distribution under today's climate and under climate change scenarios for 2030 and 2050 and compared the outputs to published theoretical temperature limits. Incongruence identified between the models and theoretical temperature limits highlighted the difficulty of using point occurrence data to study a species whose distribution is mediated more by human activity than by climate. Synthesis of this data with dengue transmission climate limits in Australia derived from historical dengue epidemics suggested that a proliferation of domestic water storage tanks in Australia could result in another range expansion of Ae. aegypti which would present a risk of dengue transmission in most major cities during their warm summer months.

Conclusions/Significance

In the debate of the role climate change will play in the future range of dengue in Australia, we conclude that the increased risk of an Ae. aegypti range expansion in Australia would be due not directly to climate change but rather to human adaptation to the current and forecasted regional drying through the installation of large domestic water storing containers. The expansion of this efficient dengue vector presents both an emerging and re-emerging disease risk to Australia. Therefore, if the installation and maintenance of domestic water storage tanks is not tightly controlled, Ae. aegypti could expand its range again and cohabit with the majority of Australia's population, presenting a high potential dengue transmission risk during our warm summers.

Current and projected rainfall reduction in southeast Australia has seen the installation of large numbers of government-subsidised and ad hoc domestic water storage containers that could create the possibility of the mosquito Ae. aegypti expanding out of Queensland into southern Australian's urban regions. By assessing the past and current distribution of Ae. aegypti in Australia, we construct distributional models for this dengue vector for our current climate and projected climates for 2030 and 2050. The resulting mosquito distribution maps are compared to published theoretical temperature limits for Ae. aegypti and some differences are identified. Nonetheless, synthesising our mosquito distribution maps with dengue transmission climate limits derived from historical dengue epidemics in Australia suggests that the current proliferation of domestic water storage tanks could easily result in another range expansion of Ae. aegypti along with the associated dengue risk were the virus to be introduced.

Rapid identification of Aedes albopictus, Aedes scutellaris, and Aedes aegypti life stages using real-time polymerase chain reaction assays

In 2005, a widespread infestation of Aedes albopictus was discovered in the Torres Strait, the region between northern Australia and New Guinea. To contain this species, an eradication program was implemented in 2006. However, the progress of this program is impeded by the difficulty of morphologically separating Ae. albopictus larvae from the endemic species Aedes scutellaris. In this study, three real-time TaqMan polymerase chain reaction assays that target the ribosomal internal transcribed spacer 1 region were developed to rapidly identify Aedes aegypti, Ae. albopictus, and Ae. scutellaris from northern Australia. Individual eggs, larvae, pupae, and adults, as well as the species composition of mixed pools were accurately identified. The assay method was validated using 703 field-collected specimens from the Torres Strait.

Evaluation of the inhibition of egg laying, larvicidal effects, and bloodfeeding success of Aedes aegypti exposed to permethrin- and bifenthrin-treated military tent fabric

Laboratory studies were conducted to evaluate the effects of treating military canvas tent fabric with bifenthrin and permethrin on the survival of the eggs and larvae of Aedes aegypti. Gravid female Ae. aegypti were able to oviposit on tent canvas treated with either bifenthrin or permethrin. However, none of the eggs laid on treated canvas hatched, and no larvae added to water in treated trays survived. Low residual concentrations of bifenthrin and permethrin on treated canvas prevented the development of eggs and larvae of Ae. aegypti. Inhibition of bloodfeeding was shown when Ae. aegypti adults were exposed to lower concentrations (10-50% of operational concentrations) of bifenthrin- and permethrin-treated canvas tent fabric. These experiments have shown that military tent canvas treated with either bifenthrin or permethrin can reduce the development of Ae. aegypti eggs and larvae and reduce bloodfeeding success of adults.

Evaluation of Bistar 80SC (bifenthrin) as a tent treatment for protection against mosquitoes in Northern Territory, Australia

A field trial to assess the efficacy of Bistar 80 SC as a barrier treatment of Australian military tents was conducted over 10 d at Mount Bundey Military Training Area, Northern Territory, Australia, in March 2003. Four pairs of standard eight-person tents were erected, with a single tent in each pair treated with 0.1% Bistar 80 SC as a course spray, and the remainder left as untreated control tents. Carbon dioxide-baited traps were operated in each tent nightly, and biting collections conducted over 8 nights. There was a mean increase in protection of 81% for mosquitoes entering treated tents and 90.4% increase in protection against biting of predominantly Culex annulirostris Skuse. In addition, bifenthrin applied to the military tents enhances the protection of occupants against bites from this important arbovirus vector.

Forest malaria in central Vietnam

Studies were conducted in a village in central Vietnam to explain the existence of a forest malaria cycle of transmission external to the village. The findings suggested no malaria transmission in the village because of the absence of a suitable vector, but suggested evidence for transmission in villagers when attending garden plots in the forested hills surrounding the village. A sizeable population residing near these garden plots, the presence of Anopheles dirus (a highly efficient vector), and a degree of malaria immunity within the inhabitants created suitable conditions to sustain malaria transmission outside the village.

Identification of Anopheles minimus complex and related species in Vietnam

Anopheles minimus A and C and several closely related species of mosquitoes have been identified in Vietnam, where some have been implicated in malaria transmission. Morphological variation within and between Anopheles minimus A and C makes identification using alpha taxonomy difficult and several molecular techniques have been developed to separate them. However the difficulties of applying these techniques and the benefits of morphological identification in the field have seen morphological characteristics, such as the humeral pale spot on the costa, being used to separate these two species. In this study, the morphological and molecular examinations of 2,206 specimens collected in Vietnam indicate that pale scaling on the proboscis reliably separates An. aconitus from An. minimus s.l., but hind tarsal banding cannot separate An. jeyporiensis from An. minimus s.l., and the presence or absence of the humeral pale spot is not a reliable characteristic for differentiating An. minimus A from C due to variation of this characteristic in An. minimus C.

A polymerase chain reaction-based diagnostic to identify larvae and eggs of container mosquito species from the Australian region

Dengue outbreaks occur regularly in parts of northern Queensland, Australia, and there is concern that these outbreaks may spread with the introduction and range expansion of the two main vectors Aedes aegypti (L.) and Aedes albopictus (Skuse). Problems encountered in separating larvae of endemic and exotic container mosquito species resulted in the development of a polymerase chain reaction diagnostic procedure that uses a restriction enzyme to cut the internal transcribed spacer region 1 of the ribosomal DNA to separate Ae. aegypti and Ae. albopictus from a number of common local container mosquito species which can be used at any stage of the life cycle, including eggs up to 8 wk of age. Identification was possible using desiccated or alcohol-preserved specimens with a response time of < 24 h after receipt of the specimens.

A molecular phylogeny of Anopheles annulipes (Diptera: Culicidae) sensu lato: the most species-rich anopheline complex

The Australasian Annulipes Complex is the most species-rich among Anopheles mosquitoes, with at least 15 sibling species suspected. Members of this complex are the most likely vectors of malaria in the past in southern Australia and are involved in the spread of myxomatosis among rabbits. In this, the first comprehensive molecular study of the Annulipes Complex, 23 ITS2 rDNA variants were detected from collections throughout Australia and Papua New Guinea, including diagnostic variants for the previously identified An. annulipes species A-G. Specimens of each ITS2 variant were sequenced for portions of the mitochondrial COI, COII and nuclear EF-1alpha genes. Partitioned Bayesian and Maximum Parsimony analyses confirmed the monophyly of the Annulipes Complex and revealed at least 17 clades that we designate species A-Q. These species belong to two major clades, one in the north and one mainly in the south, suggesting that climate was a driver of species radiation. We found that 65% (11) of the 17 sibling species recorded here had unique COI sequences, suggesting that DNA barcoding will be useful for diagnosing species within the Annulipes Complex. A comparison of the taxa revealed morphological characters that may be diagnostic for some species. Our results substantially increase the size of the subgenus Cellia in Australasia, and will assist species-level studies of the Annulipes Complex.

Environmental factors associated with distribution and range limits of malaria vector Anopheles farauti in Australia

Ecological factors associated with the narrow coastal distribution of Anopheles farauti Laveran s.s. were investigated using decision tree software and a recently developed software tool that permits analysis of environmental gradients across distributional boundaries. Significant variables identified by these procedures were then used to develop ecological niche models that permitted detailed--and improved--predictions of the species' overall distribution. These methods identified seven climatic factors (four of temperature factors and three atmospheric moisture factors) from among 40 environmental variables related to the range of this species. In addition, the gradient-analysis tool identified elevation as being particularly important. The distributional hypothesis predicted using ecological niche modeling of these factors included all of the record sites from which An. farauti s.s. was collected in northern Australia and successfully reconstructed its narrow limitation to coastal areas. Omission of elevation from analyses resulted in unrealistic predictions of potential distributional areas > 100 km inland, where the species has not been found.

The anopheline fauna of Papua New Guinea

Surveys for anopheline mosquitoes were conducted throughout the mainland of Papua New Guinea from 1992 to 1998 with the aim of mapping the distribution of the anopheline fauna. Larval collections, adult trap, and human landing collections indicated the presence of seven species (other than those belonging to the Anopheles punctulatus group); these were An. bancroftii, An. annulipes, An, karwari, An. longirostris, An. meraukensis, An. novaguinensis, and An. subpictus. The distribution and ecology of these species is discussed.

Does 1-octen-3-ol enhance trap collections of Japanese encephalitis virus mosquito vectors in northern Australia?

The responses of Japanese encephalitis virus (JEV) mosquito vectors to 1-octen-3-ol (octenol) and CO2 were evaluated using Centers for Disease Control (CDC) light traps at 3 sites in northern Australia. There was no significant difference between the number of Culex sitiens subgroup mosquitoes or Cx. gelidus collected in CDC light traps baited with either CO2 alone or CO2 + octenol on Badu Island. At both mainland locations, using octenol in combination with CO2 significantly increased collections of Cx. sitiens subgroup mosquitoes. Collections of nontarget species, such as Ochlerotatus spp., Anopheles spp., and Verrallina spp. were also significantly increased with the addition of octenol. At all 3 locations, reducing collections of nontarget mosquitoes by not using octenol increased the proportion of Culex spp. collected, thus potentially reducing the time and resources required to sort and process collections for JEV detection. Our results also indicate that trials into the efficacy of using octenol as an attractant should be carried out in each area prior to the implementation of a mosquito-based arbovirus surveillance system.

Field evaluation of commercial repellent formulations against mosquitoes (Diptera: Culicidae) in Northern Territory, Australia

Field trials comparing commercially available repellent formulations containing picaridin (1-piperidinecarboxylate acid, 2-(2-hydroxyethyl)-1-methylpropylester) and deet (N,N-diethyl-3-methylbenzamide) against mosquitoes in Northern Territory, Australia, were conducted. Three repellents were compared: Autan Repel containing 9.3% picaridin, RID containing 10% deet, and Bushman Ultra containing 80% deet in a gel. The predominant mosquito species collected were Culex annulirostris Skuse (63.2%), Ochlerotatus normanensis (Taylor) (19.6%), and Anopheles meraukensis Venhuis (8.6%). Autan Repel provided >95% protection against all mosquitoes for 2 h, RID for 7 h, and Bushman for >8 h. Against Cx. annulirostris, Autan Repel provided >95% protection for 5 h, RID for 7 h, and Bushman for >8 h. The study showed that both deet formulations provided significantly better protection against mosquitoes than picaridin (Autan Repel). All 3 repellents provided good protection against Cx. annulirostris, an important vector of arboviruses in Australia.

Genetic diversity of the dengue vector Aedes aegypti in Australia and implications for future surveillance and mainland incursion monitoring

In February 2004, the discovery of an incursion of the dengue vector Aedes aegypti into the town of Tennant Creek in the Northern Territory caused concern for the Northern Territory health authorities who proceeded to implement a Commonwealth-funded eradication program. To determine the origin of the incursion, we performed a genetic analysis on Ae. aegypti from several Queensland and overseas localities. A comparison of DNA sequences from the mitochondrial cytochrome oxidase 1 gene indicated that the incursion was probably from Cairns or Camooweal. This genetic marker was also useful in identifying a separate Townsville haplotype population and another population on Thursday Island in the Torres Strait that was genetically divergent to the mainland populations. The possible use of this marker as a surveillance tool for identifying the origins of local and overseas incursions is discussed.

The effectiveness of light, 1-octen-3-ol, and carbon dioxide as attractants for anopheline mosquitoes in Madang Province, Papua New Guinea

The effectiveness of light, 1-octen-3-ol (octenol), carbon dioxide (CO2) and a combination of CO2 and octenol were compared as mosquito attractants using encephalitis vector surveillance traps in 2 villages in Madang Province, Papua New Guinea (PNG). Five species were collected, Anopheles koliensis, Anopheles farauti 2, Anopheles farauti 4, Anopheles longirostris, and Anopheles bancroftii. Light alone was not attractive to any of these species, and the attractiveness of octenol alone, though greater than light, was less than that of CO2 or the CO2 + octenol combination. With An. longirostris, the addition of octenol to CO2 resulted in a statistically significant increase in trap numbers; however, for the other species, any increase was not significant, and with An. koliensis and An. bancroftii, trap numbers were actually reduced when the CO2 + octenol bait was used. In PNG, the use of octenol alone would be effective in attracting more anophelines than if light alone was used; however, octenol by itself was not as effective as CO2.

Field evaluation of repellent formulations containing deet and picaridin against mosquitoes in Northern Territory, Australia

Field efficacy of repellent formulations containing picaridin (1-methyl-propyl 2-(2-hydroxyethyl)-1-piperidinecarboxylate) or deet (N,N,-diethyl-3-methylbenzamide) against mosquitoes in Northern Territory, Australia, was evaluated. The following repellent treatments were evaluated: 19.2% picaridin (Autan Repel Army 20), a solution of 20% deet in ethanol, and 35% deet in a gel (Australian Defense Force [ADF]). The predominant mosquito species were Culex annulirostris Skuse (57.8%), Anopheles merankensis Venhuis (15.4%), and Anopheles bancroftii Giles (13.2%). The protection provided by repellents against Anopheles spp. was relatively poor, with 19.2% picaridin and ADF deet providing >95% protection for only 1 h, whereas 20% deet provided <95% protection at 1 h after repellent application. In contrast, the repellents provided good protection against Cx. annulirostris, with 19.2% picaridin providing >95% protection for 5 h and both deet formulations providing >95% protection for 7 h when collections ceased. This study provides additional field data showing tolerance of Anopheles spp. for repellents. The response of field populations of Cx. annulirostris, an important vector of arboviruses in Australia, to repellents containing deet and picaridin is reported for the first time.

An outbreak of Plasmodium vivax malaria in Far North Queensland, 2002

OBJECTIVE

To describe an outbreak of Plasmodium vivax malaria in Far North Queensland in 2002.

DESIGN

Epidemiological and entomological investigations; molecular analyses of the infecting parasites.

MAIN OUTCOME MEASURES

Case characteristics, adult and larval mosquito counts at the outbreak location, haplotyping of parasites in blood samples from different cases determined through sequencing of AMA1 and MSP1 genes.

RESULTS

A man with imported P. vivax malaria stayed at a camping ground 95 km north of Cairns in late September 2002. This led to an outbreak of P. vivax malaria in 10 adults who stayed at the camping ground in October. Large numbers of Anopheles farauti sensu lato larvae were present in stagnant pools in a creek at the camping ground, and many adult mosquitoes were collected nearby. Not only had most of the infected patients been exposed to mosquitoes at night, they were also less likely than other campers to have used insect repellents appropriately (odds ratio, 0.01; P < 0.001). Two different haplotypes of P. vivax, only one of which was detected in the imported case, were involved in the outbreak.

CONCLUSIONS

Although local transmission of malaria is rare in Far North Queensland, the risk is probably higher in the dry season (September to December). Campers need to be aware of the increased risk of mosquito-borne diseases. Sexual recombination of multiple gametocytes in mosquitoes infected by the imported case may have resulted in the two haplotypes of P. vivax involved in the outbreak.