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Aquatic insect predators and mosquito control.

Tropical Biomedicine.2009;26(3):223-261.

Mosquitoes are serious biting pests and obligate vectors of many vertebrate pathogens. Their immature larval and pupal life stages are a common feature in most tropical and many temperate water bodies and often form a significant proportion of the biomass. Control strategies rely primarily on the use of larvicides and environmental modification to reduce recruitment and adulticides during periods of disease transmission. Larvicides are usually chemical but can involve biological toxins, agents or organisms. The use of insect predators in mosquito control has been exploited in a limited fashion and there is much room for further investigation and implementation. Insects that are recognized as having predatorial capacity with regard to mosquito prey have been identified in the Orders Odonata, Coleoptera, Diptera (primarily aquatic predators), and Hemiptera (primarily surface predators). Although their cpacity is affected by certain biological and physical factors, they could play a major role in mosquito control. Furthermore, better understanding for the mosquitoes-predators relationship(s) could probably lead to satisfactory reduction of mosquito-borne diseases by utilizing either these predators in control programs, for instance biological and/or integrated control, or their kairomones as mosquitoes'ovipoisting repellents. This review covers the predation of different insect species on mosquito larvae, predatorprey- habitat relationships, co-habitation developmental issues, survival and abundance, oviposition avoidance, predatorial capacity and integrated vector control.

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Prevalence of Cryptosporidium infection in camels (Camelus dromedarius) in a slaughterhouse in Iran.

Razawi SM ; Oryan A ; Bahrami S ; Mohammadalipour A ; Gowhari M

Tropical Biomedicine.2009;26(3):267-273.

Cryptosporidiosis is a zoonotic protozoan disease of worldwide distribution, affecting a wide range of vertebrate hosts. Most data on the biology, distribution pattern, pathology and prevalence of cryptosporidial infection in farm animals is restricted to cattle, sheep and goats. Limited data is available in other domestic herbivores including camel. Numerous camels (Camelus dromedarius) are raised in the semi-arid regions of Iran. Although camel is acknowledged as a potential source of contamination, little is known with regards to the prevalence of Cryptosporidium in this population except a case report on the occurrence of this infection in a bactrian camel (Camelus bactrianus) in China. This investigation was undertaken to determine the prevalence of Cryptosporidium infection in camels (C. dromedarius) from Najaf-Abad slaughterhouse, Isfahan Province, central part of Iran. Out of 103 faecal samples from 63 adult males and 40 adult females, 2-14 years old, 39 (37.9%) were found positive for oocysts. No significant differences were observed between males and females, and among different age groups. There was also no significant difference among infection intensity in different age groups. This is the first report of Cryptosporidium infection in camels from this country.

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Characterization of vancomycin-resistant Enterococcus isolates from broilers in Selangor, Malaysia.

Getachew YM ; Hassan L ; Zakaria Z ; Saleha AA ; Kamaruddin MI ; Che Zalina MZ

Tropical Biomedicine.2009;26(3):280-288.

Vancomycin-resistant Enterococcus (VRE) is an emerging nosocomial pathogen in humans. The use of antibiotics in human therapy and in the production of food animals has been incriminated in the emergence of this organism. The present study describes the distribution of VRE species, the vancomycin-resistant genes detected, the vancomycin resistance pattern observed, and the genetic diversity of the isolates found in live broiler chickens in Malaysia. Overall 140 VRE were isolated with species comprising Enterococcus faecalis (48%), Enterococcus faecium (25.7%), Enterococcus gallinarum (12.1%), Enterococcus casseliflavus (1.4%) and other Enterococcus species (12.8%). Vancomycin resistance gene vanA and intrinsic genes vanC1 and vanC2/3 were detected in the study population. VanA was detected in 15 (63.9%) of E. faecium, 23 (22.4%) of E. faecalis and in 3 (17.6%) E. gallinarum isolates. E-test was conducted on randomly selected 41 of the isolates and the minimum inhibition concentration (MIC) of vancomycin for five (11.9%) of tested isolates is more than 256mug/ml. Genotypic analysis using random amplified polymorphic DNA (RAPD) showed genetic diversity within the Enterococcus species.

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No evidence for successful interspecific cross-mating of transgenic Aedes aegypti (L.) and wild type Aedes albopictus Skuse.

Lee HL ; Aramu M ; Nazni WA ; Selvi S ; Seshadri V

Tropical Biomedicine.2009;26(3):312-319.

The natural and artificial mating of laboratory bred Aedes albopictus and transgenic Aedes aegypti RIDL-513A-Malaysian strain was conducted. The experiment consisted of crossmating of homologous Ae. aegypti RIDL female symbol X Ae. aegypti RIDL male symbol and reciprocal Ae. aegypti RIDL female symbol X Ae. albopictus WT male symbol. The other set comprised homologous Ae. albopictus WT female symbol X Ae. albopictus WT male symbol and reciprocal Ae. albopictus WT female symbol X Ae. aegypti RIDL male symbol. This study demonstrated that reproductive barriers exist between these two species. Cross insemination occurred between A. albopictus male and Ae. aegypti female and their reciprocals. There was 26.67% and 33.33% insemination rate in Ae. aegypti RIDL female cross-mating with A. albopictus WT male and Ae. albopictus female cross-mating with Ae. aegypti RIDL male, respectively. There was 0% hatchability in both directions of the reciprocals. There was also no embryonation of these eggs which were bleached. Although none of the female Ae. albopictus WT was inseminated in the cross-mating with Ae. albopictus WT female symbol X Ae. aegypti RIDL male symbol, a total of 573 eggs were obtained. The homologous mating was very productive resulting in both high insemination rate and hatchability rates. Generally there was a significantly higher insemination rate with artificial mating insemination of homologous than with artificial mating of reciprocal crosses. Interspecific mating between Ae. aegypti RIDL and Ae. albopictus wild type was not productive and no hybrid was obtained, indicating absence of horizontal transfer of introduced RIDL gene in Ae. aegypti to Ae. albopictus.

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Non-O1, non-O139 Vibrio cholerae bacteraemia in splenectomised thalassaemic patient from Malaysia.

Deris ZZ ; Leow VM ; Wan Hassan MN ; Nik Lah AZ ; Lee SY ; Siti Hawa H ; Siti Asma H ; Ravichandran M

Tropical Biomedicine.2009;26(3):320-325.

Vibrio cholerae infection is mainly caused acute diarrhoea disease. Bacteraemia due to non-O1 V. cholerae is rare and mainly reported in liver cirrhotic patients. We report one case of non-O1 V. cholerae bacteraemia in splenectomised thalassaemic patient who presented with septic shock secondary to abdominal sepsis. She had undergone emergency laporatomy and was managed in the intensive care unit for nine days. She was treated with meropenem and doxycyline and discharged well after fourteen days of admission. The V. cholerae was identified by API 20NE, serotype and polymerase chain reaction showed as non-O1, non-O139 strain. Besides known cholera-like toxin and El Tor hemolysin, with increasing reported cases of V. cholerae bacteraemia, there is possibility of other virulence factors that allow this organism to invade the bloodstream.

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Binding affinity and larvicidal activity of a novel vegetative insecticidal protein Vip3V.

Doss VA

Tropical Biomedicine.2009;26(3):334-340.

Bacillus thuringiensis (Bt) is a well-known entomo-pathogen. Strains of Bt. that are toxic to a variety of insects belonging to various orders such as Lepidoptera, Diptera and Coleoptra have been identified, their larvicidal proteins isolated, characterized and used extensively in agriculture for protecting the economically important crops against these pests. Recently a novel group of vegetative insecticidal genes, vip3S and vip3V coding for 789-amino acid (88.5 kDa) protein in Bacillus thuringiensis was cloned and expressed in Escherichia coli and found to be highly sensitive to most of the agricultural pests and even towards the resistant insects. The binding affinity of these toxins to the receptors of these insect pests and relation between the affinity and larvicidal activity were carried out. Labeling of the toxin proteins with radioactive 125I and preparation of the Brush border membrane vesicles of the receptors were carried out. Analysis of saturation kinetics (Kd) and binding constants (Bmax) by competition assays revealed direct correlation between the binding affinity of the toxin to the receptor and insect mortality.

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Laboratory bioefficacy of nine commercial formulations of temephos against larvae of Aedes aegypti (L.), Aedes albopictus Skuse and Culex quinquefasciatus Say.

Chen CD ; Lee HL ; Chan CK ; Ang CL ; Azahari AH ; Lau KW ; Sofian Azirun M

Tropical Biomedicine.2009;26(3):360-365.

The bioefficacy of nine commercial formulations of temephos against Aedes aegypti, Aedes albopictus and Culex quinquefasciatus larvae were evaluated in the laboratory. WHO larval bioassay with operational dosage of temephos at 1 mg/L was performed. The larval mortality was recorded every 5 minutes until complete mortality was achieved. All formulations of temephos exhibited various toxicity level against Ae. aegypti, Ae. albopictus and Cx. quinquefasciatus. Generally, larvae of Cx. quinquefasciatus was susceptible to all formulations of temephos, followed by Ae. aegypti and Ae. albopictus.

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Predation on pupa of Chrysomya rufifacies (Marquart) (Diptera: Calliphoridae) by parasitoid, Exoristobia philippinensis Ashmead (Hymenoptera: Encyrtidae) and Ophyra spinigera larva (Diptera: Muscidae).

Heo CC ; Nazni WA ; Lee HL ; Jeffery J ; Baharudin O ; Chen CD ; Lau KW ; Sofian Azirun M

Tropical Biomedicine.2009;26(3):369-372.

A forensic entomological study was conducted using monkey carcasses (Macaca fascicularis Raffles) that were placed in either an outdoor or indoor environment at a coastal area in Tanjung Sepat, Selangor, Malaysia during May until August 2008. We collected pupae of Chrysomya rufifacies (Marquart) from the carcasses and kept them individually. The emergence of 13 parasitic microhymenopteran, from one of the pupae occurring within a week were identified as Exoristobia philippinensis Ashmead (Hymenoptera: Encyrtidae). Another observation was made whereby a pupa of C. rufifacies was predated by a muscid larva, Ophyra spinigera (Stein). The larva squeezed into the pupa and consumed the contents. This paper report C. rufifacies as a new host record for E. philippinensis in Malaysia and highlighted the predatory behavior of O. spinigera larva in natural environment.

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Breeding patterns of the JE vector Culex gelidus and its insect predators in rice cultivation areas of northern peninsular Malaysia.

Abu Hassan, A ; Hamady, D ; Tomomitsu, S ; Michael, B ; Jameel S L, A S

Tropical Biomedicine.2010;27(3):404-16.

Japanese encephalitis (JE) virus activity is an important cause of viral encephalitis in Southeast Asia. In Malaysia, JEV activity has been first detected in Culex gelidus in 1976. Since then, no study has fully addressed the seasonal dynamics of this mosquito. As irrigated rice production expands, the incidence of JEV vectors, particularly Cx. gelidus is expected to increase. We surveyed Penang Island to determine the breeding patterns of Cx. gelidus and their potential insect predators, in relation to habitat/niche and rice growing period. Six rice fields proper (RFP) and related drainage canals (DC) were visited through three cultivation cycles (CCs) over 17 months. Weekly visits were performed to each of the 36 sites and mosquito larvae and aquatic insects were sampled from RFP and DCs using dippers. Culex gelidus was abundant in RFP and almost absent in DCs. Its densities usually were high during the first and 3rd CC and when the RFs were in Fp, Pp and Gp. In DCs, the mosquito was abundant during Mp, e.g., 2nd CC. Predators, especially those belonging to the families Corixidae, Coenagrionidae and Dytiscidae, were more present in RFP. Predator numbers usually were high during the first CC; in some cases predator abundance peaked during other CCs, e.g., corixids and dysticids. In RFP, neither corixids nor coenagrionids showed any positive correlation with densities of Cx. gelidus. However, dytiscids' population peaked when the mosquito densities were on the rise. These observations suggest that Cx. gelidus is active during the period of rice cultivation. Operational vector control through bio-control or with insecticides near the end of the rice cultivation season in RFP may prove beneficial in reducing the density of Cx. gelidus, but also the amount of bio-agent or insecticide applied on riceland.

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Prevalence of scabies and head lice among children in a welfare home in Pulau Pinang, Malaysia.

Muhammad Zayyid, M ; Saidatul Saadah, R ; Adil, A R ; Rohela, M ; Jamaiah, I

Tropical Biomedicine.2010;27(3):442-6.

This is a survey of 120 children for scabies and head lice infestations in a welfare home in Pulau Pinang. Children from this welfare home (Rumah Kanak-Kanak Taman Bakti, Kepala Batas, Pulau Pinang) were randomly selected. Majority of them were Malays (72.5%) and the rest were Indians. The infestation rates were highest in the 10-12 years age group with 46% and 70% for scabies and head lice respectively. Head lice was more commonly seen in girls (65%) than boys (29%). Scabies was more commonly seen in boys (50%) than girls (16%). Overall prevalence rate for scabies was 31% and for head lice infestation was 49%.

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