Morphology and protein profiles of salivary glands of filarial vector mosquito Mansonia uniformis; possible relation to blood feeding process.

Background: Vector control is a key strategy for eradication of filariasis, but it is limited, possibly due to rapid propagation from global warming. In Thailand, Mansonia mosquitoes are major vectors of filariasis caused by Brugia malayi filarial nematodes. However, little is yet known about vector biology and host-parasite relationship. Objectives: Demonstrate the preliminary data of salivary gland morphology and protein profile of human filarial mosquitoes M. uniformis. Methods: Morphology of M. uniformis salivary gland in both sexes was comparatively studied under a light microscope. Total protein quantization and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDSPAGE) was performed to compare protein profile between male and female. In addition, quantitative analysis prior to and after blood feeding was made at different times (0, 12, 24, 36, 48, 60, and 72 hours) Results: Total salivary gland protein of males and females was 0.32?0.03 and 1.38?0.02 ?g/pair gland, respectively. SDS-PAGE analysis of the female salivary gland protein prior to blood meal demonstrated twelve bands of major proteins at 21, 22, 24, 26, 37, 39, 44, 53, 55, 61, 72, and 100 kDa. Compared to female, male salivary gland was composed of seven major protein bands at 39, 44, 53, 55, 61, 83, and 100 kDa. Quantitative study after blood feeding revealed that protein of 37 kDa decreased gradually whereas proteins of 61 and 83 kDa started to increase dramatically at 24 hours. It was postulated that the 37 kDa band, found only in the female, might serve as a candidate molecule for facilitating blood feeding. Conclusion: Morphology and protein components of M. uniformis salivary glands might relate to blood feeding process and filarial disease transmission.

Repellent activity of essential oils against cockroaches (Dictyoptera: Blattidae, Blattellidae, and Blaberidae) in Thailand.

Seven commercial essential oils extracted from the plant species Boesenbergia rotunda (L.) Mansf., Citrus hystrix DC., Curcuma longa L., Litsea cubeba (Lour.) Pers., Piper nigrum L., Psidium guajava L. and Zingiber officinale Roscoe, and naphthalene as a control, were evaluated for repellent activity against the three cockroach species Periplaneta americana (L.), Blattella germanica (L.) and Neostylopyga rhombifolia (Stoll) under laboratory conditions. The essential oil derived from Citrus hystrix showed the best repellency over other candidate essential oils and naphthalene. The essential oil of Citrus hystrix exhibited complete repellency (100%) against P. americana and B. germanica, and also showed the highest repellency (among the essential oils tested) of about 87.5% against N. rhombifolia under laboratory conditions. In the field, Citrus hystrix essential oil formulated as a 20% active ingredient in ethanol and some additives provided satisfactory repellency of up to 86% reduction in cockroaches, mostly P. americana and N. rhombifolia with a residual effect lasting a week after treatment. Citrus hystrix essential oil has good potential for being used as a cockroach repellent. Further improvements in efficacy and residual activity may be realized with appropriate formulations.

Field evaluation of novaluron, a chitin synthesis inhibitor larvicide, against mosquito larvae in polluted water in urban areas of Bangkok, Thailand.

Novaluron, an insect growth regulator, a benzoylphenyl urea insecticide, was evaluated in the field against the larvae of polluted-water mosquitoes. The study was carried out in highly polluted sites infested with populations of mosquito larvae, mostly Culex quinquefasciatus Say, in low-income communities in urban areas of Bangkok, Thailand. An EC10 formulation was premixed in water and applied by pressurized spray tank to plots ranging from 180 to 1,000 m2 at the rate of 0.1 ml EC 10/m2 (equal to 10 mg a.i./m2) of the breeding sites. Assessments were made by sampling mosquito larvae and pupae to determine the trends of immature populations before treatment and weekly after treatment. Reduction of the populations in percents were then computed by comparing counts of immature mosquitoes (larvae and pupae) to the pretreatment counts at each particular site. It was found that the immature populations of mosquitoes in the treated areas were dramatically suppressed and remained at extremely low levels for 3-7 weeks after the treatment depending on the prevailing conditions of each experimental site. No negative impact on fishes or aquatic plants in the treated areas were detected during the study period and three months after the experiment was discontinued. Novaluron is an effective agent to control immature populations of polluted-water mosquitoes, especially Cx. quinquefasciatus in habitats in urban areas. This IGR larvicide may play an important role in vector control programs in terms of effectiveness, environmental friendliness and strategies for insecticide-resistance management in vector mosquitoes.

Double infection of heteroserotypes of dengue viruses in field populations of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) and serological features of dengue viruses found in patients in southern Thailand.

In order to understand more about the epidemiology of DHF, a study of the type of dengue viruses and vectors under natural conditions was carried out. Mosquito vectors in the field and the serum of DHF patients in southern Thailand were examined. The two mosquito species are abundant and DHF incidence remains high in this region. Dengue viruses were examined in field-caught mosquitoes by RT-PCR technique. The mosquitoes were caught in 4 provinces: Krabi, Phuket, Phang-Nga and Surat Thani during the late dry season until the early rainy season in 2005. Three dengue serotypes (DEN-2, DEN-3, DEN-4) were detected in Ae. aegypti males and females, and 2 (DEN-2, DEN-3) were detected in Ae. albopictus females. Double infection with 2 serotypes of dengue viruses (DEN-2 and DEN-3) were detected in Ae. aegypti males and females and Ae. albopictus females. DEN-2 and DEN-1 were the most prevalent serotypes found in the serum of the patients in this area, followed by DEN-4 and DEN-3. The prevalence of the predominant dengue serotype varied from province to province. Detection of viruses in adult male mosquitoes reveals the role of transovarial transmission of dengue viruses in field populations of DHF vectors and elucidates circulation of dengue viruses in vectors in the natural environment of endemic areas. The incidence of multiple serotypes of dengue virus in Ae. aegypti and Ae. albopictus in the same area points toward a high risk for an epidemic of DHF. These findings provide greater understanding of the relationship among mosquito vectors, virus transmission and DHF epidemiology in endemic areas.

Decrease of mosquito salivary gland proteins after a blood meal: an implication for pathogenesis of mosquito bite allergy.

Salivary gland protein profiles ofAedes aegypti (L.) and Culex quinquefasciatus (Say) pre- and post-blood feeding were analyzed. SDS-PAGE studies before blood feeding of Ae. aegypti demonstrated 8 major polypeptide bands of 20, 35, 37, 42, 45, 47, 70 kDa and a high molecular weight band >118 kDa, whereas those of Cx. quinquefasciatus demonstrated 9 major polypeptide bands of 20, 26, 36, 38, 45, 47, 49 kDa and 2 high molecular weight bands >118 kDa. After a blood feeding, salivary gland polypeptides of Ae. aegypti at 35, 37, 45, 47, 70 kDa and high molecular weight band >118 kDa were depleted, while the polypeptide bands of 20, 26, 36, 38 kDa were depleted in Cx. quinquefasciatus. The presented study suggests that these major polypeptides were introduced into vertebrate hosts when a mosquito took a blood meal. Further investigation in molecular, biochemical and immunological aspects of these salivary gland polypeptides may provide information for better understanding in the role of these proteins in mosquito bite allergy.

Resolution of eosinophilia after treatment of cutaneous gnathostomiasis.

The present study was to investigate the dynamics of eosinophil in peripheral blood of patients with cutaneous gnathostomiasis before and after worm removal. The total of 28 proven cases of cutaneous gnathostomiasis treated by albendazole were included in the present study. The absolute eosinophil count (AEC) was higher than 500/ul during infestation in almost all the patients, the positive rate was 89%, and significantly decreased to normal level after receiving albendazole and worm removal within 3 months in 96%. In conclusion, an increas of AEC is another important hallmarks of cutaneous gnathostomiasis and this parameter could be the earlier indicator for responsiveness to treatment.

Analysis of salivary gland proteins of the mosquito Armigeres subalbatus.

Quantitative studies of total salivary gland protein of Armigeres subalbatus mosquito revealed that the total salivary gland protein increased dramatically during the five days after emergence as adults. The amount of salivary gland protein of female and male mosquitos at day five after adult emergence were on the average 11.55 and 1.32 microg/pair gland respectively. SDS-PAGE studies showed that salivary gland protein profiles of Armigeres subalbatus demonstrated 9 major polypeptide bands of 68, 65, 60, 55, 40, 30, 28, 21, and 15 kDa. The 21 and 65 kDa bands were found only in the distal lateral region of the mosquito salivary gland and were depleted after the female mosquito took a blood meal.

Prevalence of dengue virus in Aedes mosquitoes during dry season by semi-nested reverse transcriptase-polymerase chain reaction (semi-nested RT-PCR).

Dengue hemorrhagic fever remains a major health concern in Thailand. Much effort has focused on the prevention and control of the disease. Detection of dengue virus infection rate in mosquitoes would evaluate dengue control programs and predict the epidemics of dengue hemorrhagic fever. To determine dengue virus infection rate in mosquitoes by Semi-nested RT-PCR. A total of 400 mosquitoes were collected from Rom Kao Community representing a crowded community and another 9 non-crowded communities in Bangkok. Mosquitoes were then divided into 40 pools, each contained 10 mosquitoes. A total of 391 Aedes aegypti and 9 Aedes albopictus were screened for dengue virus. The mosquito infection rate in the Rom Klao community was 5% of the mosquito pool equal to that found in non-crowded communities. Both groups were found to have dengue virus serotype 3. The present study suggests a circulation of dengue virus serotype 3 in both crowded and non-crowed communities, the infection rates of which are indifferent during the dry season.

Efficacy of albendazole against early and late stage of Trichinella spiralis infection in mice.

Efficacy of albendazole against early and late stage of Trichinella spiralis infection in mice was determined. To determine the efficacy of albendazole against the early stage (enteral phase) of trichinosis, mice experimentally infected with T. spiralis were treated with albendazole 20 mg/kg at 7 days post infection for 15 days. Larvae were recovered from the infected mice 7 days after the treatment. The reduction rate of the larvae was 100 per cent. Efficacy of albendazole against the late stage (parenteral phase) of infection was determined at 30 days post infection. Mice were treated with albendazole at 20 mg/kg for 30 days. Larvae were recovered from the infected mice 7 days after the treatment. The reduction rate of the larvae was 71 per cent compared to the control group. In conclusion, albendazole was more effective in the early stage of infection than the late stage, the reduction was 100 per cent and 71 per cent with respect to the control group respectively.

Prevalence of parasitic infections among Thai patients at the King Chulalongkorn Memorial Hospital, Bangkok, Thailand.

Parasitic diseases are still considered to be a major public health problem. Most patients with parasitic infections are asymptomatic and therefore remain undetected. Asymptomatic parasitic infections are usually discovered by routine parasite examination. To determine the result of parasite examination at the Parasitology Unit, Out Patient Department, King Chulalongkorn Memorial Hospital, Bangkok, Thailand, the authors collected the data of individuals examined for parasite infections from June to December 1997. A total of 6,231 Thais provided the data for analysis. Evidence of parasitic infections was found in 557 (8.94%) cases. The disease was most prevalent in males (57.3%), and in the age group >15-30 years old (11.13%). The population from the Northeast of Thailand was found to harbor parasites with the highest prevalence rate (17.03%), while it was 11.90 per cent in the northern group. The parasitic prevalence rates in the West, East, South and Central regions were 10.60 per cent, 8.90 per cent, 7.74 per cent, and 4.92 per cent, respectively. The parasite most commonly identified was Strongyloides stercoralis (33.39%), while giardiasis was the most common protozoan infection (14.36%). The highest infection rates of S. stercoralis, hookworms, Opisthorchis viverrini, and Gnathostoma spinigerum were found in northeasterners. People from the North of Thailand were infected mostly with G. lamblia. People of working-age from northeastern as well as northern regions harbored pathogenic parasites with high prevalence rates. To prevent parasitic infections, health education for these high risk groups should be provided.