Two commercial repellants were evaluated in the laboratory against Leptotrombidium fletcheri chiggers. The active ingredient in one was DEET and in the other was citrus oil. Excito-toxicity effect was studied and it was determined by the time ("escape time") chiggers took to move off filter papers treated with the repellants. All chiggers exposed on filter papers treated with DEET died and did not move off the treated papers. None of the chiggers that were placed on papers treated with citrus oil were killed. Escape times on papers treated with a 2-sec spray of citrus oil were longer than those for the 4- and 8-sec sprays. The weights of citrus oil deposited increased with increasing spray times. Electron microscopy showed that the repellants had no effect on the texture of the filter papers. It was concluded that the spray containing DEET was more effective; however, both repellants should be further evaluated under field conditions for protection against chigger bites.
Five pesticides were evaluated against laboratory colonies of Leptotrombidium fletcheri (Womersly and Heaslip) by the Pasteur pipet technique. The pesticides were dieldrin (LC50 = 3.6 ppm, LC99 = 18.2 ppm), bromopropylate (LC50 = 9.2 ppm, LC99 = 239.6 ppm), dicofol (LC50 = 27.8 ppm, LC99 = 118.1 ppm), fenthion (LC50 = 15.4 ppm, LC99 = 29.7 ppm), and malathion (LC50 = 84.7 ppm, LC99 = 313.9 ppm). Dieldrin was the most toxic. Dicofol was recommended for further evaluation in field trials.
From 2005 to 2009, the Institute for Medical Research (IMR), Kuala Lumpur, Malaysia received 488 serum and blood samples from hospitalized patients on the East Coast of Peninsular Malaysia, suspected of having dengue infection. In this study we determined the prevailing dengue serotypes using a real time polymerase chain reaction assay (RT-PCR). All 4 dengue virus serotypes were found circulating during the study period; however the predominant serotype varied. In 2005 and 2006, the predominant serotypes circulating were DENV-1 and DENV-3, in 2007, DENV-1 and DENV-2 were predominant, and in 2008 and 2009, DENV-3 was the predominant serotype.
The Institute for Medical Research, Malaysia, was designated the National Reference Laboratory for Poliomyelitis Eradication (NRLPE) in 1992. Since then, our Polio Laboratory has collaborated actively with the Disease Control Division, Ministry of Health (MOH), Malaysia and WHO towards achieving polio eradication. Since 1992, the NRLPE has investigated 1,063 stool specimens from 641 acute flaccidparalysis (AFP) cases. One hundred and one enteroviruses were isolated from these specimens. Positive cell cultures were confirmed by microneutralization assay using standard WHO antisera. All enterovirus isolates were sent to the Victorian Infectious Disease Reference Laboratory in Melbourne, Australia, for further identification and poliovirus intratypic differentiation. Thirty-one out of these 101 virus isolates (30%) were polioviruses (PV) and the remaining 70 (70%) were non-polio enteroviruses (NPEV) which included coxsackie B viruses, echoviruses and enterovirus 71. Three of the poliovirus isolates were wild-type polioviruses isolated in 1992 which were the last wild-type polioviruses isolated in Malaysia. The rest were vaccine-related Sabin-like strains. Monthly reports of the virological investigation of AFP cases are sent to WHO and to the MOH, AFP control committee. The NRLPE continues to play an integral role in AFP surveillance and is committed to the WHO's goal of global polio eradication by the year 2005.
The performance of a commercial immunochromatography test for rapid detection of dengue NS1 antigen present in serum or plasma of patients was evaluated against a commercial dengue NS1 antigen-capture ELISA. The rapid immunochromatography test gave an overall sensitivity of 90.4% with a specificity of 99.5%. The sensitivity was highest for serum samples from which virus was isolated (96.3%) and lowest for those from which virus was not isolated and RT-PCR was negative (76.4%). The sensitivity was significantly higher for serum samples from patients with acute primary dengue (92.3%) than those from patients with acute secondary dengue (79.1%). The positive predictive value and negative predictive value of this commercial immunochromatography test were 99.6% and 87.9% respectively.