We detected 2 natural, asymptomatic Plasmodium inui monoinfections in humans in Malaysia by using nested PCR on concentrated high-volume blood samples. We found a P. inui-positive Anopheles cracens mosquito in the same site as the human infections. Investigators should use ultrasensitive detection methods to identify simian malaria parasite transmission in humans.
Anopheles maculatus Theobald sensu lato is a species complex now consisting of eight sibling species; An. maculatus is still represented by two cytologically distinct forms; i.e., the widely distributed sensu strictu or B, and E from southern Thailand and adjacent areas in northern Malaysia. Cuticular lipid profiles in conjunction with principal component analysis was used to separate An. maculatus form E from sensu stricto form B in a preliminary survey of the An. maculatus complex at five locations spanning peninsular Malaysia. The relative rank orders, from the areas of the five gas chromatographic peaks used to determine lipid differences for specimens from peninsular Malaysia, matched well with those from cytogenetically identified colony specimens of An. maculatus forms B and E. The two-dimensional principal component pattern of specimens identified as form E was highly clumped, which indicated that very similar cuticular lipids were present within this putative malaria vector. Both forms coexisted in peninsular Malaysia, but form E may be dominant except in the south.
Recent studies on cytogenetics, behavioral, geographical and distinct morphological characters on adult, pupal and larval stages have revealed that "balabacensis" is a species complex. Anopheles dirus the mainland species, is distributed widely in Thailand and is renowned for its role as primary vector of human malarial parasites. Further, evidence from cytogenetic and taxonomic studies suggests that "An. dirus" is a species complex comprising at least four distinct species provisionally designated: dirus A, B, C and D. These cryptic species are distinguishable only partially morphologically, but can be separated on the basis of metaphase chromosomes using the Giemsa and Hoechst 33258 staining techniques. Apparently, these siblings show distinct patterns of geographic distribution in Thailand and Peninsular Malaysia. The recognition of dirus as a complex of species in Thailand and Peninsular Malaysia requires a re-evaluation of the role that the individual members of this complex have in the transmission of malaria parasites in this region. Cytological analysis of gene rearrangements in ovarian polytene chromosomes has shown that An. maculatus is a sibling-species complex consisting of at least four species in Thailand provisionally designated: maculatus A, B, C and G. These siblings are sympatric in some populations. Furthermore, species B is so highly polymorphic for chromosome rearrangements that four geographic forms can be recognized. It is not known whether these four forms are subspecies or yet further species within the species B complex. These sibling-species must be differentiated in order to understand any differential capabilities in their transmission of human malaria parasites. Anopheles nivipes was elevated from synonymy under An. philippinensis to full species status by Reid, a decision recently confirmed by cross mating experiments. The Thailand Malaria Division does not differentiate these two species and only identifies An. philippinensis, yet, An. nivipes is by far the most common of the two species in Thailand. Furthermore, preliminary surveys of the ovarian polytene chromosomes of several widely separated populations of An. nivipes in Thailand have revealed at least two distinct chromosomal types of nivipes based on fixed inversions on the X chromosomes.
Anopheles cracens has been incriminated as the vector of human knowlesi malaria in peninsular Malaysia. Besides, it is a good laboratory vector of Plasmodium falciparum and P. vivax. The distribution of An. cracens overlaps with that of An. maculatus, the human malaria vector in peninsular Malaysia that seems to be refractory to P. knowlesi infection in natural settings. Whole genome sequencing was performed on An. cracens and An. maculatus collected here. The draft genome of An. cracens was 395 Mb in size whereas the size of An. maculatus draft genome was 499 Mb. Comparison with the published Malaysian An. maculatus genome suggested the An. maculatus specimen used in this study as a different geographical race. Comparative analyses highlighted the similarities and differences between An. cracens and An. maculatus, providing new insights into their biological behavior and characteristics.
Among Oriental anopheline mosquitoes (Diptera: Culicidae), several major vectors of forest malaria belong to the group of Anopheles (Cellia) leucosphyrus Dönitz. We have morphologically examined representative material (> 8000 specimens from seven countries) for taxonomic revision of the Leucosphyrus Group. Six new species are here described from adult, pupal and larval stages (with illustrations of immature stages) and formally named as follows: An. latens n. sp. (= An. leucosphyrus species A of Baimai et al., 1988b), An. cracens n. sp., An. scanloni n. sp., An. baimaii n. sp. (formerly An. dirus species B, C, D, respectively), An. mirans n. sp. and An. recens n. sp. Additionally, An. elegans (James) is redescribed and placed in the complex of An. dirus Peyton & Harrison (comprising An. baimaii, An. cracens, An. dirus, An. elegans, An. nemophilous Peyton and Ramalingam, An. scanloni and An. takasagoensis Morishita) of the Leucosphyrus Subgroup, together with An. baisasi Colless and the An. leucosphyrus complex (comprising An. balabacensis Baisas, An. introlatus Baisas, An. latens and An. leucosphyrus). Hence, the former Elegans Subgroup is renamed the Hackeri Subgroup (comprising An. hackeri Edwards, An. pujutensis Colless, An. recens and An. sulawesi Waktoedi). Distribution data and bionomics of the newly defined species are given, based on new material and published records, with discussion of morphological characters for species distinction and implications for ecology and vector roles of such species. Now these and other members of the Leucosphyrus Group are identifiable, it should be possible to clarify the medical importance and distribution of each species. Those already regarded as vectors of human malaria are: An. baimaii[Bangladesh, China (Yunnan), India (Andamans, Assam, Meghalaya, West Bengal), Myanmar, Thailand]; An. latens[Borneo (where it also transmits Bancroftian filariasis), peninsular Malaysia, Thailand]; probably An. cracens (Sumatra, peninsular Malaysia, Thailand); presumably An. scanloni (Thailand); perhaps An. elegans (the Western Ghat form of An. dirus, restricted to peninsular India); but apparently not An. recens (Sumatra) nor An. mirans[Sri Lanka and south-west India (Karnataka, Kerala, Tamil Nadu)], which is a natural vector of simian malarias. Together with typical An. balabacensis, An. dirus and An. leucosphyrus, therefore, the Leucosphyrus Group includes about seven important vectors of forest malaria, plus at least a dozen species of no known medical importance, with differential specific distributions collectively spanning > 5000 km from India to the Philippines.
Perkembangan penggunaan insektisid sebatian organostanum(IV) terhadap Aedes aegypti telah diterokai dan diuji keberkesanannya bagi mengatasi masalah kerintangan insektisid sedia ada. Kajian ini dijalankan bertujuan menguji kesan insektisidal iaitu larvisidal dan adultisidal dua siri baru sebatian difenilstanum(IV) dan trifenilstanum(IV) alkilfenilditiokarbamat ke atas Ae. aegypti di makmal. Keempat-empat sebatian iaitu difenilstanum(IV) etilfenilditiokarbamat (DFEF), trifenilstanum(IV) etilfenilditiokarbamat (TFEF), difenilstanum(IV) butilfenilditiokarbamat (DFBF) dan trifenilstanum(IV) butilfenilditiokarbamat (TFBF) telah dijalankan ujian bioasai larvisidal ke atas larva instar ketiga Aedes aegypti. Kajian lanjutan diteruskan bagi sebatian yang telah menunjukkan aktiviti larvisidal terbaik untuk menguji kesan adultisidnya ke atas nyamuk betina Aedes aegypti. Hasil ujian bioasai larvisidal, didapati sebatian TFEF menunjukkan kesan larvisidal terbaik dengan nilai LC50 dan LC90 pada 0.082 ppm dan 0.184 ppm masing-masing. Sementara itu, sebatian TFBF juga menunjukkan kesan larvisidal yang baik dengan nilai LC50 dan LC90 masing-masing pada 0.108 ppm dan 0.273 ppm manakala kedua-dua sebatian DFEF dan DFBF didapati tidak menunjukkan kesan larvisidal yang baik. Ujian adultisidal pula, sebatian TFEF didapati tidak menunjukkan kesan adultisidal yang baik dengan nilai LC50 dan LC90 masing-masing yang agak tinggi iaitu 31,556.03 ppm dan 98,427.05 ppm. Walaupun sebatian TFEF didapati tidak menunjukkan kesan adultisid yang baik, ianya sangat berpotensi untuk dibangunkan sebagai larvisid. Namun begitu, kajian lanjutan perlu dilakukan untuk menjelaskan dan memastikan sebatian ini selamat digunakan sebagai larvisid.
SIR,-I was glad to read a letter from Dr. Copeland (Dec. 6), a pioneer in bringing medical treatment to the Muruts of North Borneo.1 I feel that something should be said about the present malaria situation there. McArthur's control measures for the vector " Anopheles leucosphyrus " (now A. balabacensis), were in fact resumed by him under the new post-war Government. Clearing the undergrowth around seepages was tried during 1949-52, and showed some reduction in vector breeding and spleen-rates.2 However, more recent surveys have shown that McArthur's experimental villages no longer show any malariometric advantage over comparison villages, despite his hopes for the relative permanence of his methods. It was decided by the GovemmentjW.H.O.jUNlcEF Malaria Project to use house spraying with residual insecticide, which had proved highly effective in Sarawak against the virtually identical A. leucosphyrus. For Dr. Copeland's information, these mosquitoes do rest on walls during the night for periods sufficiently long to make them susceptible to effective attack by residual insecticides. It has been shown during the past three years that residual insecticides produce a very great decrease in the density of the vector. On Labuan Island house-spraying alone has been successful in interrupting transmission, and when combined with antimalarial drugs it has been shown capable of controlling transmission even in the most difficult parts of the interior. The complete eradication of malaria from British North Borneo now appears to be an attainable goal.