Analysis of "dipstick" ELISA to detect SLEV

Vodkin, M. and N. Krasavin, R. Novak

Within the past year, a "dipstick" ELISA (Dip-S-Ticks) , Integrated Diagnostics, Inc., Baltimore, MD) has become available for the detection of St. Louis encephalitis virus (SLEV) from mosquitoes. Since this test has been specifically mentioned by personnel from several Illinois mosquito abatement districts, the Medical Entomology Lab assumed a responsibility for assessing its efficacy. Comparative laboratory studies with the Dip-S-Tick and the RT-PCR on two independent tissue culture preparations of SLEV, one with a known and the other with unknown amounts of virus were done. Field trials with this detection system are planned for the upcoming mosquito season.

Distribution of Ae. albopictus in Illinois

Novak, R. and R. Lampman

Large populations of Aedes albopictus, the Asian "tiger mosquito," were first discovered in the continental United States in used tires in Texas, 1985. In Illinois from 1986 to 1999, it has spread into 23 counties. It is well-established throughout southern Illinois, as well as in Peoria and Chicago. Ae. albopictus is an aggressive daytime biter and feeds on a number of hosts. It is an efficient vector of 25 viruses and dog heart-worm. It is found in artificial containers such as tires, flower pots, cemetery urns, buckets, tin cans, rain gutters, ornamental ponds, and bird baths and in natural containers such as treeholes. This is an ongoing study of the distribution and ecology of this species in Illinois.

Ecology of Aedes triseriatus and Ae. hendersoni

Reno, H.(UIUC), R. Novak, M. Vodkin

The mosquito vector of LaCrosse virus (LACV), Aedes triseriatus, and its non-vector sibling species, Aedes hendersoni, provide a model to study the vector/virus evolution. Field studies examine the urban and rural distribution and relationships as well as blood feeding habits. Lab studies are examining the salivary gland protein apyrase. Apyrase is responsible for interfering with platelet aggregation in the blood meal host. Salivary glands from Ae. triseriatus and Ae. hendersoni are removed, their morphology is described, and apyrase activity is characterized. These comparisons between sibling species will begin to address the evolutionary issues surrounding the virus-vector relationship.

Enzootic cycle of St. Louis encephalitis virus

Novak, R. and M. Vodkin, N. Krasavin

A significant body of information has accumulated concerning St. Louis encephalitis virus and its vector mosquitoes. However, most studies are biased geographically (outside Midwest), ecologically (only urban), and epidemiologically (just before, during, after an epidemic). This study involves the annual collection of mosquitoes throughout the season by a variety of methods in ecologically diverse settings in Illinois. Mosquito collections in central and southern areas were done by the Medical Entomology Lab and northern areas by the City of Chicago and by mosquito abatement districts. Mosquitoes from each habitat are identified to species and assayed for the presence of virus by RT-PCR.

Evaluation soy oil and Bti in rice plots

Novak, R. and R. Lampman, M. Miesch (University of Arkansas)

Small plot field trials were conducted in 1999 with the University of Arkansas to determine the effectiveness of the following formulations against Anopheles quadrimaculatus Say larvae in small rice plots: 1) methylated soybean oil (MSO), 2)MSO with technical grade Bacillus thuringienisis var. israelensis (Bti) powder,3) Golden Bear Oil (GB-1111), and 4) a water-based formulation of Bti. The study was designed to evaluate MSO as a mosquito larvicide under field conditions and to establish the duration of activity. The effectiveness of Bti formulations with methylated soybean oil and water were comparable for 48 hr. In contrast, MSO+surfactant-A and GB-1111 were ineffective at 24 hr., and MSO+surfactant-B was twice as active as GB-1111 at 48 hr.

Evaluations of soy oil and monoterpenes

Novak, R. and R. Lampman, D. Siegler (UIUC)

Surface-active petroleum-based larvicides have been used to control mosquito larvae for over a century. A variety of plant and synthetic water-insoluble extracts have also been evaluated as alternatives. This research compared the larvicidal activity of methylated soy oil (MSO) with two non-ionic surfactants. The influence of water temperature on the toxicity of surfactant-MSO mixture was also evaluated. The impact of the two different surfactants on the toxicity of three lipophilic monoterpenes was also tested. The laboratory bioassays suggest that MSO and some plant products mixed with surfactants are potential mosquito larvicides. All three monoterpenes were considered poor larvicides.

Field efficacy of anti-mosquito products

Novak, R.

The public's demand for convenient, safe and effective anti-mosquito products has led to the mass-marketing of many types of products advertised to keep the user mosquito-free. Many of these products do not have the scientific data to substantiate such claims. The efficacy of these products (e.g. smoke-coils, light-traps, sonic-devices, oils, plants) were tested by mosquito biting frequency compared to negative (untreated volunteers) and positive controls (volunteers + deet). Deet is a repellent, which provides protection against mosquitoes. The results indicate that none of the products were effective in repelling mosquitoes. This study was viewed on ABC News.

Larvicidal activity of acetylenic compounds

Lampman, R. and D. Siegler (UIUC), R. Novak

This investigation evaluated the insecticidal activity of several hundred native Illinoisan plants. One of the most toxic extracts to mosquito larvae was from Cryptotaenia canadensis, honewort, common in the eastern U.S. Fresh foliage, roots and fruits were extracted into chloroform and water. Both phases were bioassayed against 4th instar larvae at concentrations ranging from 5-50 ppm. Gas-liquid-chromatography followed by chromatography on silica gel aided in identifying two compounds, falcarinol and falcarindiol. The mosquito LC50's were 3.5 ppm for falcarinol and 6.5 ppm for falcarindiol. The mode of action of these acetylenic compounds is against the larvae currently being investigated.

Molecular differentiation of two sibling species

Reno, H.(UIUC), M. Vodkin, R. Novak

Aedes triseriatus, the vector of LaCrosse virus (LAC), causes encephalitis in children. Ae. hendersoni, a sibling species is not a vector. The adults are morphologically indistinguishable and are sympatric. This study provides a method to identify adults, a critical aspect for both research and surveillance. A PCR amplification method using either a mosquito leg or a thorax was used. The PCR products were then subjected to restriction digestion analysis or direct sequencing. This study provides a method for amplifying a region of mosquito DNA and then subjecting the amplified product to digestion with informative restriction enzymes allowing for reliably distinguishing the 2 species.

Predicting Culex populations in Illinois

Novak, R. and R. Lampman

Mosquito oviposition traps have been set out throughout the Champaign, Urbana, Savoy, and University of Illinois area to monitor the temporal and spatial distribution of Culex population for the last 5 years. Traps were checked daily and all mosquito egg rafts (1 raft per female) found were counted and identified to species. Two models were developed to test whether using oviposition trap data could be used to predict first appearance of Culex pipiens, the principal vector of St. Louis encephalitis virus (SLEV), and when it becomes more abundant than Culex restuans. These models are developed for mosquito abatement programs to predict when mosquito control is necessary to prevent SLEV outbreaks.

Protocol for the detection of West Nile virus

Vodkin, M. and R. Novak

A major outbreak of an imported African virus, first misidentified as St. Louis Encephalitis virus, in the northeastern U.S., initiated this investigation to develop a molecular assay and field sampling methods. This virus affects both humans and horses and kills many birds, especially American Crows. The dispersal habits of crows and other birds coupled with several implicated mosquito species provide the possibility for Illinois to be at risk. Protocols for handling this exotic agent as well as small fragments of recombinant DNA were written and approved by the UIUC Biohazard Committee. This investigation will require upgrading lab facilities to comply with USDA requirements.

Tire model for mosquito development

Novak, R. and M. Vodkin, L. Lampman

Waste tires, which have the capacity to hold water for extended periods of time, serve as potential sites where mosquitoes can complete their entire aquatic developmental cycle. Yet the critical factors and their interactions that determine whether all or only a subset of tires actually contribute to mosquito productivity have not been investigated in a rigorous manner. The model attempts to integrate, in theory and practice, the known physical and chemical parameters that will determine the ability of a tire to act as a mosquito habitat. The model is expected to have the power to forecast when, where, and under what conditions tires are at risk to dramatically cause an increase in population density.

Training in mosquito virus identification

Vodkin, M. and N. Krasavin, R. Novak

While the Medical Entomology lab has engaged in the development of molecular techniques for detecting arboviruses, it has been a policy to assist in the education, training, and technology transfer to individuals or agencies external to the INHS. In past years, the format has included workshops and/or individual sessions. This year, two international visitors attended the lab to receive training: Ms. Leigh Anne Bailey, Virology Dept., University of Natal, Republic of South Africa and Professor Parsutman Kanakaraj Madras Veterinary College, Chennai, India.

Traps for monitoring Culex mosquitoes

Lampman, R. and R. Novak

St. Louis encephalitis virus (SLEV) is the most common mosquito-borne human pathogen in the United States. Transmission of SLEV primarily involves a mosquito-bird-mosquito cycle with periodic amplification of the virus in peridomestic birds. Over one-third of the confirmed cases of SLE from 1964 to 1997 occurred in six states in the Mississippi-Ohio River drainage, with Illinois having the greatest number of cases. The goal of our study was to compare the temporal distribution of Culex species based on different sampling devices. A combination of species identification and SLEV detection of gravid females by molecular techniques provides for an efficient method for vector and virus surveillance.