Dengue Vector Control in Malaysia- Challenges and Recent Advances

Dengue is a serious mosquito borne disease common in tropical and sub-tropical countries including Malaysia. There is at present a lack of specific treatment and an effective tetravalent vaccine against dengue. The control of dengue depends solely on the suppression of the two most important vectors namely, Aedes aegypti and Ae albopictus. Despite intensive and extensive control efforts by health agencies, the disease continues to spread. This paper updates various innovations on control of dengue vectors. Gene-based sterile insect technique using the RIDL technology for both Aedes aegypti & Ae albopictus control has now been actively researched and field trials are pursued to evaluate the effectiveness of the technology. The release of Wolbachia-infected Ae aegypti is another dengue control innovation. The infected mosquito cannot support development of dengue virus and has shorter life span. Other innovations include: auto-dissemination of insect control agents using ovitrap, autocidal adult and larva trap, outdoor residual spraying, insecticidal paint and biocontrol agent. In other innovation, outbreak prediction capability is enhanced by developing model based on environmental data and analysis utilising neural network.

Ochrobactrum anthropi catheter-related bloodstream infection: the first case report in malaysia

A 60-year old Malay man presented with an intermittent lowgrade fever for 3 days and worsening of right ankle ulcers. He was known to have ischaemic heart disease, diabetes mellitus type 2, hypertension and end stage renal failure and was on regular haemodialysis. The organisms isolated from the peripheral and central blood specimens were identified as Ochrobactrum anthropi, a rarely encountered gramnegative bacillus with a unique antibiotic susceptibility profile. His condition improved after removal of the catheters and administration of antibiotic therapy. This case report highlights the importance of being wary of such rare, opportunistic pathogens and good communication between the microbiologists and the clinicians.

Aedes larval population dynamics and risk for dengue epidemics in Malaysia

Early detection of a dengue outbreak is an important first step towards implementing effective dengue interventions resulting in reduced mortality and morbidity. A dengue mathematical model would be useful for the prediction of an outbreak and evaluation of control measures. However, such a model must be carefully parameterized and validated with epidemiological, ecological and entomological data. A field study was conducted to collect and analyse various parameters to model dengue transmission and outbreak. Dengueprone areas in Kuala Lumpur, Pahang, Kedah and Johor were chosen for this study. Ovitraps were placed outdoor and used to determine the effects of meteorological parameters on vector breeding. Vector population in each area was monitored weekly for 87 weeks. Weather stations, consisting of a temperature and relative humidity data logger and an automated rain gauge, were installed at key locations in each study site. Correlation and Autoregressive Distributed Lag (ADL) model were used to study the relationship among the variables. Previous week rainfall plays a significant role in increasing the mosquito population, followed by maximum humidity and temperature. The secondary data of rainfall, temperature and humidity provided by the meteorological department showed an insignificant relationship with the mosquito population compared to the primary data recorded by the researchers. A well fit model was obtained for each locality to be used as a predictive model to foretell possible outbreak.

[Acute effects of apple cider vinegar intake on some biochemical risk factors of atherosclerosis in rabbits fed with a high cholesterol diet]

Metabolic changes in postprandial stage, especially after consumption of high fat meal cause atherosclerosis and increase the risk of cardiovascular diseases. Apple cider vinegar is an acidic juice with useful medicinal effects. In this research; we investigated acute effects of apple cider vinegar intake on some of the biochemical atherosclerosis risk factors in high cholesterol fed rabbits. Thirty two male New Zealand rabbits were randomly divided into four groups: normal diet group, high cholesterol diet group [%1cholesterol],%1 cholesterol with 5ml apple cider vinegar group,%1 cholesterol with 10ml apple cider vinegar group. The C-Reactive Protein [CRP], low density lipoprotein [LDL-C], high density lipoprotein [HDL-C], total cholesterol [TC], malondialdehyde [MDA], oxidized-LDL [OxLDL], serum glutamic pyruvic transaminase [SGPT], serum glutamic oxaloacetate transaminase [SGOT], nitrite, nitrate, glucose, fibrinogen triacylglycerol [TG], apolipoprotein A [ApoA1], apolipoprotein B [ApoB100] were all measured before the experiment and three hours after feeding with these treatment diets. In high cholesterol diet fibrinogen, nitrite, glucose, OxLDL, MDA and CRP showed a significant increase compared to normal diet. Significant differences were observed between both groups of apple cider vinegar by fibrinogen in comparison with hypercholesterolemic diet. Using 10ml apple cider vinegar with cholesterolemic diet caused a significant reduction in Ox-LDL, MDA and glucose in comparison with hypercholesterolemic diet. Moreover, the consumption of 5ml apple cider vinegar with cholesterolemic diet caused a significant decrease in LDL-C and TC compared to hypercholesterolemic diet. No significant difference was found between apple cider vinegar taking groups and hypercholesterol diet in CRP, TG ApoA, HDL-C, ApoB, SGOT, SGPT, nitrite and nitrate. The results showed that acute consumption of apple cider vinegar [as an antioxidant] causes significant reduction on some risk factors of atherosclerosis

Association of Iron Deficiency with or without Anaemia and Cognitive Functions among Primary School Children in Malaysia

Iron deficiency and anaemia affect millions of children worldwide. This study aimed to investigate the effect of iron deficiency with or without anaemia on cognitive functions, specifically with short-term memory, attention and visualmotor coordination in children. A total of 173 primary school children was enrolled. Cognitive functions were assessed using the Wechsler Intelligence Scale for Children. Three sub-tests were selected to assess processing speed (coding test), immediate auditory memory (digit span test) and visual processing and problem solving ability (maze test). The results showed significant correlation between age and coding test (r =0.38, p<0.001), digit span test (r =0.16,p = 0.028), and maze test scores (r =0.28, p<0.001), and the total sub-test scores (r=0.43, p <.001). After age adjustment of the cognitive function tests, iron deficient children without anaemia scored significantly lower than the healthy children (p<0.001) on coding test, while iron deficient children with anaemia and iron deficient children without anaemia scored significantly lower (p<0.001) than the healthy counterparts on maze test. No significant differences were observed on digit-span score among the groups. This study confirms the negative effect of both iron deficiency and iron deficiency anaemia on processing speed and visualmotor coordination in children.

Persistency of transovarial dengue virus in Aedes aegypti (Linn.).

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.

Health status of Orang Asli (aborigine) community in Pos Piah, Sungai Siput, Perak, Malaysia.

A study of health status of Orang Asli population (based on physical examination findings) was conducted in 4 villages in Pos Piah, Sungai Siput Perak, Malaysia. In all 356 individuals between 4 months-72 years old (178 males and 178 females) participated in this study. Poor general health status, physical and mental handicaps were seen in 7.8%, 0.3% and 0.3% of the population, respectively. About one-fifth of the population had dental caries. Splenomegaly, hepatomegaly and hepatosplenomegaly were among the commonest abnormalities with the occurrence rates of 19.8%, 13.7% and 6.7%, respectively, being detected in the population. About one-fifth of the population showed signs suggestive of protein-energy deficiency; whilst less than 5% showed signs indicative of riboflavin, iodine and iron deficiencies. Vitamin A deficiency was the commonest nutritional deficiency identified in this community with almost 38.4% of them showing signs of the deficiency. The commonest skin infection was scabies.

Microdroplet application of mosquitocidal Bacillus thuringiensis using ultra-low-volume generator for the control of mosquitos.

In an effort to develop a more effective technique in dispersing a microbial control agent, Bacillus thuringiensis (Bt), a truck-mounted ultra low volume (ULV) generator (Scorpion) was used to disperse B. thuringiensis israelensis (Bti) and Bti with malathion. Complete larval and adult mortalities for all tested mosquito species within the first 70-80 feet from the ULV generator were achieved. Beyond that distance less than 50% mortality was achieved as insufficient sprayed particles reached the area. A minimum of 10(3) Bti colony forming units per ml is required to cause 100% larval mortality. The sprayed Bti larvicidal toxins were persistent in the test water 7 days post ULV. The effectiveness of B. thuringiensis jegathesan (Btj), a new mosquitocidal Bt serotype was also evaluated. Similar mortality results as Bti were achieved except that the Btj toxins underwent degradation in the test water, since less than 50% less in larval mortality was observed in 7 days post ULV samples. This ULV method has the potential to disperse Bt and malathion effectively for a simultaneous control of mosquito adults and larvae.