In this study, artificial membrane feeding technique was used to orally feed Aedes aegypti with dengue and chikungunya viruses. Virus detection was carried out by reverse transcriptase polymerase chain reaction. The study did not detect dual infection of Ae. aegypti with dengue and chikungunya virus from the same pool or from individual mosquitoes. Oral receptivity of Ae. aegypti to chikungunya virus was higher than that of dengue virus.
A study was conducted to examine the persistency of transovarial dengue virus type 2 (DEN-2) in a Selangor strain of Aedes aegypti mosquitoes. Two hundred 4-5 day old female mosquitoes were fed with blood containing dengue virus. The infected mosquitoes were reared to the 7th generation; each generation was screened for the virus using immunological staining methods. The virus was detectable until the 5th generation but absent in the 6th and the 7th generations. Therefore, dengue virus type 2 can be transmitted transovarially in Aedes aegypti mosquitoes until the fifth generation under laboratory conditions.
White-rot fungi, namely Coriolus versicolor and Schizophyllum commune, were studied for the biodecolorization of textile dyeing effluent in shaker-flask experiments. The results showed that C. versicolor was able to achieve 68% color removal after 5 days of treatment while that of S. commune was 88% in 9 days. Both fungi achieved the above results in non-sterile condition with diammonium hydrogen phosphate as the nutrient supplement. On the other hand, the best COD removal of 80% was obtained with C. versicolor in 9 days in sterile effluent with yeast extract as nutrient supplement, while S. commune was able to remove 85% COD within 8 days in non-sterile textile effluent supplemented with diammonium hydrogen phosphate.
This study was conducted to determine the inhibitory effects of ribavirin and hydroxyurea on dengue virus replication in Aedes aegypti mosquitoes. Female Ae. aegypti mosquitoes were infected with dengue-2 virus and fed ribavirin at a dose of 0.3 mg/ml and/or hydroxyurea at a dose of 6 mg/ml via artificial membrane feeding technique. The virus in infected mosquitoes was isolated using C6/36 cell culture. Peroxidase-antiperoxidase (PAP) staining was used to detect dengue-infected C6/36 cells and to quantify the level of infection by determining the presence of infected cells. In mosquitoes treated with ribavirin alone, hydroxyurea alone or both drugs in combination had reductions in dengue infection rates of 87.72, 89.47 and 95.61%, respectively. The mortalities of female Ae. aegypti mosquitoes fed with these drugs were significantly higher than the control. Ribavirin also had an inhibitory effect on the fecundity of female Ae. aegypti mosquitoes.
All percutaneous tracheostomies performed in the general intensive care unit (ICU), Hospital Sultanah Aminah, Johor Bahru, Malaysia, from July 1999 to June 2002 were studied. The tracheostomies were performed as an elective bedside technique in the ICU. A total of 352 percutaneous tracheostomies were performed. Eighty-eight percent of the tracheostomies were completed within 15 minutes. The most common complication was bleeding which occurred in 52 patients (14.7%). The rest of the complications encountered were:- transient hypoxia twelve (3.4%), inability/ difficulty to insert tracheostomy tube eight (2.3%), false passage four (1.1%), transient hypotension two (0.6%), pneumothorax two (0.6%), peristomal infection two (0.6%), subcutaneous emphysema one (0.3%), cuff rupture one (0.3%), oesophageal cannulation one (0.3%), and granuloma formation one (0.3%). Conversion to conventional tracheostomies were performed on 7 patients (2%). There was one unfortunate death related to percutaneous tracheostomy. In conclusion, percutaneous dilational tracheostomy can be used safely to manage the airway of critically ill patients.
Wild caught female Culex quinquefasciatus (Say) from Kuala Lumpur were blood fed and reared in the insectarium. The late third stage of the F1 larvae which survived the high selection pressure of malathion and permethrin were reared and colonies were established from adults that emerged. Larvae from these colonies were then subjected in the subsequent 9 generations to higher selection pressure. The rate of resistance development were measured by LC50 value of larval bioassay, LT50 value of adult bioassay and the frequency of the elevated esterase levels. In another set of experiments using the same batch of Culex mosquitos, the larvae were not exposed to any insecticides and the decrease in resistance rate was monitored in each subsequent 9 generations by using similar methods. The heterozygous standard laboratory strain was selected for susceptibility using the single raft sib-selection method. The result showed that the field collected F1 generation was 96.0 and 6.3 fold more resistant to malathion and permethrin, respectively. After selection for about 9 generations the resistance ratio to malathion and permethrin was 6.2 and 767.3 fold more compared to the LC50 values of F1 generations, respectively. Esterase in F1 larvae was 6.0 fold more than the standard laboratory strain.
A 1 year review of 529 cases of acute appendicitis, treated at the University Hospital in 1990, was performed. Perforation rate was 23.7% and delay in diagnosis was found to be significant. Patients above 50 years of age were particularly at risk. Diagnostic error was 19.3% and it was a problem not only in young women but also in children. Temperature and rectal examinations were not found to be helpful in the diagnosis in contrast to leukocytosis. Waiting time for operation was long (median 7 hours), be it for a perforated or a nonperforated appendicitis.
Rapid enzyme microassays for the detection of resistance due to organophosphate and carbamate in individual field-collected strains of Culex quinquefasciatus adults were conducted. These tests allowed accurate differentiation by eye, on the basis of color changes of susceptible and resistant individuals. Two separate tests were conducted for the biochemical assays. In the insensitive acetylcholinesterase (AChE) test, acetylthiocholine iodide (ACTH) and 5,5-dithiobis-(2-nitrobenzoic acid) (DTNB) were used as substrate and coupling agent respectively. The resulting yellow chromophore indicated AChE activity. Test results showed that the color intensity decreased as increasing concentrations of propoxur were added, thereby confirming the susceptibility of the enzyme to inhibitor. Assay of non-specific esterase however, indicated elevated levels which were correlated with degree of malathion resistance. Electrophoretic data revealed the presence of 2 esterase bands in all strains. It was concluded that such a pattern was not contributory to malathion resistance in adults.
Factors affecting the mechanical transmission of rotavirus by the legs and wings of the housefly, Musca domestica L., were examined in a laboratory study. Rotavirus was picked up when houseflies walked on thin smears of clarified rotavirus suspensions. The addition of glycerol, which increased viscosity of the virus suspension, and particulate human feces slightly increased the proportion of flies contaminated with virus. However, the addition of glycerol greatly reduced the average number of virus particles picked up per fly, whereas feces greatly increased the number of particles. The proportion of flies with virus-contaminated legs, which transferred virus to > 1 contact surface, was increased by longer contact time with the surface and when the contact surface was agar instead of glass. Most virus particles were deposited on 1st contact with the surface. Most flies dislodged virus particles inoculated on the underside of their wings soon after the start of simulated flight. Our data indicated that the nature of the virus-suspending medium has a greater effect on the level of virus contamination than on the ability to become contaminated. The importance of walking as a mode of virus transport depends on the nature of the contact surface, the risk of the contaminated fly settling first on a surface likely to come into contact with humans, and fly numbers.
The insecticide resistance status of 4 strains of adult male Blattella germanica, viz M (Malacca), E (England), F (restaurant) and K (cafeteria) against malathion and bendiocarb compared with a reference susceptible strain (S) was determined by using a modified WHO bioassay method. The results indicated that all the 4 strains were resistant to the insecticides albeit in different degrees. Resistance ratios for malathion ranged from 1.85-41.07-fold, whereas that of bendiocarb ranged from 1.68-4.83-fold. The biochemical microplate enzyme assays technique employed indicated that the resistance in M and E strains were attributed to acetylcholinesterase insensitivity. Multiple resistance was not detected in any of the 4 strains. Parameters of the identified resistance mechanism correlated well with the observed level of resistance. Agar gel electrophoresis showed that variations in esterase isoenzymes did not confer organophosphate and carbamate resistance to the 4 strains.
Based on data collected by the population-based Singapore Cancer Registry over the period 1968 to 1982, baseline epidemiological characteristics and incidence trends of primary liver cancer were described. This will facilitate the interpretation of future trends, especially in the light of new interventions such as hepatitis B immunisation. The primary liver cancer incidence is four times higher in males than in females, with the incidence peaked in the seventh decade. The incidence rate was higher in the Chinese than in Malays and Indians and marginally higher among foreign born than Singapore born Chinese. A general declining trend in liver cancer incidence was especially notable in the local born Chinese. Misclassification of metastatic carcinomas in the earlier years of cancer registration may have contributed to the initial higher incidence. Definitive decrease in incidence as a result of hepatitis immunisation will only be seen in another two to three decades.
A pilot study was undertaken to determine the effectiveness of space application of insecticides for the control of malaria in Ranau, a district in Sabah. A village each was treated monthly: with chemical adulticide--alpha cypermethrin (Fendona SC(R)/10SC(R)) at 2 g a.i./10,000 m2 in Pahu; with biological larvicides--Bacillus thuringiensis israelensis (Vectobac 12AS(R)) at 500 ml/10,000 m2 or B. sphaericus (Vectolex WG(R)) at 500 g/10,000 m2 in Pinawantai; and with a mixture of chemical adulticide and biological larvicide in Togop Laut. All sprayings were conducted using a portable mist blower. During the study period all villages, including Tarawas the untreated village, received the conventional malaria control measures. Entomological and epidemiological surveillance was used to measure the effectiveness of the space application. The entomological surveillance indicated that the An. balabacensis population was significantly reduced by alpha cypermethrin in Pahu and Togop Laut and B. sphaericus in Pinawantai; but was not reduced by B.t.i. in Pinawantai. There was a significant reduction in the number of malaria cases and in the slide positivity rate in the treated villages during the study period. The pilot study does indicate that space application of larvicides/adulticides or a mixture of both is able to reduce the malaria vector population and the malaria transmission. A larger scale study needs to be undertaken in a malarious village/province to determine whether space application of insecticides together with other malaria control measures will be able to eradicate malaria.
A novel Clostridium bifermentans strain toxic to mosquito larvae on ingestion was isolated from a soil sample collected from secondary forest floor. This strain was designated as serovar paraiba (C. b. paraiba) according to its specific H antigen. Clostridium bifermentans paraiba is most toxic to Anopheles maculatus Theobald larvae (LC50 = 0.038 mg/liter), whereas toxicity to Aedes aegypti (Linn.) (LC50 = 0.74 mg/liter) and Culex quinquefasciatus Say (LC50 = 0.11 mg/liter) larvae was 20 and 3 times lower, respectively. The toxicity to An. maculatus larvae is as high as that of Bacillus thuringiensis serovar israelensis. C. b. paraiba was also found to exhibit significant per os insecticidal activity toward adult Musca domestica (Linn.).
A novel Bacillus thuringiensis strain highly toxic to mosquitoes was isolated from soil samples in Malaysia. This strain was shown to display a new subfraction of the H-28 flagellar antigen determining a new serovar H28a28c, which was designated serovar jegathesan. Bioassays indicated that Culex quinquefasciatus larvae are the most susceptible to this new isolate, whereas toxicity to Anopheles maculatus and Aedes aegypti larvae was 10 times lower. The potency of this new serotype is also comparable to most of the Malaysian B. thuringiensis H-14 isolates.
Bioassay test against malathion had been carried out with larval and adult stages of Aedes aegypti. The mosquitoes were under selection pressure against malathion for forty-five consecutive generations. The rate of resistance development was measured by LC(50) and LT(50) values. The larvae and adult females, after subjection to malathion selection for 45 generations, developed high resistance level to malathion, with resistance ratio of 52.7 and 3.24 folds, respectively over control mosquitoes. Cross-resistance towards the same and different groups of insecticides was determined using the F44 and F45 malathion-selected adult females. Insecticides tested were DDT (4.0%), permethrin (0.75%), propoxur (0.1%), fenitrothion (1%), λ-cyhalothrin (0.05%) and cyfluthrin (0.15%). Results indicated that the mosquitoes were highly resistant to DDT and fenitrothion, moderately resistant to propoxur, tolerant to permethrin and λ-cyhalothrin, and very low resistant to cyfluthrin.
Parasites and bacteria are reported in the faeces of birds in the current study. Fresh faecal samples of the large-billed crow (Corvus spp.) were collected from the study site at Bangsar, an urban setting in Kuala Lumpur, Malaysia. These samples were transported to laboratory and analysed for parasites and bacteria. Pre-prepared XLD agar plates were used for culturing the bacteria in the laboratory. Using the API 20ETM Test Strips, 9 different species of bacteria were identified belonging to the family Enterobacteriacea. They were Citrobacter freundii, Enterobacter cloacae, Proteus mirabilis, Klebsiella pneumoniae, Kluyvera ascorbata, Salmonella arizonae, Salmonella typhi, Shigella flexneri and Shigella sonnei. The protozoan parasites detected include Cryptosporidium spp., Cyclospora spp., Blastocystis spp., and Capillaria hepatica and Ascaris lumbricoidus ova. Environmental air samples collected on agar plates using an air sampler in the area only produced fungal colonies. Some of these pathogens found in the crows are of zoonotic importance, especially Cryptosporidium, Blastocystis, Cyclopsora, Salmonella, Shigella and Kluyvera. The finding of Kluyvera spp. in crows in our current study highlights its zoonotic potential in an urban setting.
The importance of house fly (Musca domestica L) wings in mechanical transmission of bacteria was studied. A droplet of phosphate-buffered saline containing Vibrio cholerae was rolled along one wing of each house fly. None adhered to the wings but small proportions of the bacterium were isolated from about half the wings. Vibrio cholerae was spread onto the ventral wing surfaces of each unconscious house fly which then was placed inside a bottle. When it regained consciousness, the types of activity it performed over five minutes were noted before the house fly was killed and the bacteria on its wings numerated. Control were house flies killed before inoculation. The proportion of house flies with bacteria on their wings and the mean number of bacteria remaining were significantly less on live house flies than killed controls. Among the live house flies, bacteria were detected on fewer house flies which flew (25%) than those which did not fly (81%). In addition, the mean number of bacteria on the former was significantly less than the latter (5 against 780 colonies). However, both these parameters were not significantly different between the group which performed and the group which did not perform wing grooming; takeoff and alighting over short distances, and somersaulting. Wings of unconscious house flies tethered by their thoraxes were inoculated with V. cholerae. After regaining consciousness, the house flies were allowed to move their wings in flight motions for up to 30 seconds. Small proportions of bacteria remained on all the house flies. House flies were placed in a chamber containing a liquid bait spiked with V. cholerae. After two hours, 10 were removed sequentially and cultured for V. cholerae. The bacterium was isolated from four house flies: two from the legs, and two others from their bodies minus legs and wings. In conclusion, house fly wings do not play an important role in mechanical transmission of bacteria suspended in a non-adhering liquid medium because of the low transfer rate of the bacteria to the wings and poor retention of bacteria on the wings during normal house fly activities.
There were a spate of recent complaints of insect bites and the entomological specimens received from various sources were identified to be those of cat flea (Ctenocephalides felis) and rat flea (Xenopsylla cheopis), the tropical bed-bug (Cimex hemipterus) and the dog louse (Heterodoxus spiniger). Only the fleas and the bed-bug are known to attack humans.
A study was carried out to investigate correlation between presence of specific microalgal species and Leptoconops biting midge larvae in its breeding habitats. Sand samples containing microalgae were collected from the beach where the midges were most commonly biting and from sand beaches which are potential as breeding habitats of Leptoconops. The survey covered sand beaches from 12 seperate islands. At all sites, the Bacillariophyta constituted the largest representatives of the microalgae community with the majority from the Naviculaceae family. A total of 24 microalgal species were identified from the sand samples collected from the study sites. Sand samples from Kentot Kecil Island had the highest number of algal species (11.0) and the highest algae species diversity ( Shanon-Weiner Diversity Index, H' = 0.884). Besar Island (Johor) had the lowest number of algal species (2.0) whereas Tengol A Island had the lowest algae species diversity (H'=0.234). Highest similarity index was recorded between sand samples collected from Tengol A Island and Tengol B Island (75.0%) followed by Besar Island (Melaka) and Tengol B Island (62.0 %). The variation between other islands were relatively high. Virtually many kinds of algae were found where Leptoconops were breeding but Fragilaria intermedia, Mastigloia minuta and Navicula advena were particularly common.