Elmer W. Gray

Biological Transmission of Vesicular Stomatitis Virus (New Jersey Serotype) by Simulium vittatum (Diptera: Simuliidae) to Domestic Swine (Sus scrofa)

Abstract The role of hematophagous arthropods in vesicular stomatitis virus (New Jersey serotype; VSV-NJ) transmission during epizootics has remained unclear for decades in part because it has never been shown that clinical or subclinical disease in a livestock host results from the bite of an infected insect. In this study, we investigated the ability of VSV-NJ–infected black flies (Simulium vittatum Zetterstedt) to transmit the virus to domestic swine, Sus scrofa L. Experimental evidence presented here clearly demonstrates that VSV-NJ was transmitted from black flies to the swine. Transmission was confirmed by seroconversion or by the presence of clinical vesicular stomatitis followed by seroconversion. Our results represent the first report of clinical vesicular stomatitis in a livestock host after virus transmission by an insect.

OCHLEROTATUS JAPONICUS JAPONICUS (THEOBALD) IN GEORGIA AND NORTH CAROLINA

ABSTRACT Although the 1st published record of Ochlerotatus japonicus japonicus in Georgia (Rabun County) occurred in 2004, we report here a 2002 collection and identification in Fulton County, Georgia (metro Atlanta). The finding of Oc. j. japonicus in Fulton County represents the most southern record of this species in the United States to date. Also, subsequent collections in North Carolina and 4 additional counties in northeast Georgia are reported.

Experimental Transmission of Vesicular Stomatitis New Jersey Virus from Simulium vittatum to Cattle: Clinical Outcome is Influenced by Site of Insect Feeding

ABSTRACT Vesicular stomatitis New Jersey virus (VSNJV) is an insect-transmitted Rhabdovirus causing vesicular disease in domestic livestock including cattle, horses, and pigs. Natural transmission during epidemics remains poorly understood, particularly in cattle, one of the most affected species during outbreaks. This study reports the first successful transmission of VSNJV to cattle by insect bite resulting in clinical disease. When infected black flies (Simulium vittatum Zetterstedt) fed at sites where VS lesions are usually observed (mouth, nostrils, and foot coronary band), infection occurred, characterized by local viral replication, vesicular lesions, and high neutralizing antibody titers (>1: 256). Viral RNA was detected up to 9 d postinfection in tissues collected during necropsy from lesion sites and lymph nodes draining those sites. Interestingly, when flies were allowed to feed on flank or neck skin, viral replication was poor, lesions were not observed, and low levels of neutralizing antibodies (range, 1:8–1:32) developed. Viremia was never observed in any of the animals and infectious virus was not recovered from tissues on necropsies performed between 8 and 27 d postinfection. Demonstration that VSNJV transmission to cattle by infected black flies can result in clinical disease contributes to a better understanding of the epidemiology and potential prevention and control methods for this important disease.

Mechanical Transmission of Vesicular Stomatitis New Jersey Virus by Simulium vittatum (Diptera: Simuliidae) to Domestic Swine (Sus scrofa)

ABSTRACT Biting flies have been suggested as mechanical vectors of vesicular stomatitis New Jersey Virus (family Rhabdoviridae, genus Vesiculovirus, VSNJV) in livestock populations during epidemic outbreaks in the western United States. We conducted a proof-of-concept study to determine whether biting flies could mechanically transmit VSNJV to livestock by using a black fly, Simulium vittatum Zetterstedt (Diptera: Simuliidae), domestic swine, Sus scrofa L., model. Black flies mechanically transmitted VSNJV to a naïve host after interrupted feeding on a vesicular lesion on a previously infected host. Transmission resulted in clinical disease in the naïve host. This is the first demonstration of mechanical transmission of VSNJV to livestock by insects.

[Economic losses during an outbreak of Simulium (Wilhelmia) species (Diptera: Simuliidae) in the Cappadocia region of Turkey].

OBJECTIVE The aim of this study was to calculate the economic losses during an outbreak of Simulium (Wilhelmia) spp. in the Cappadocia Region of Turkey. METHODS The economic costs associated with a 2006-2007 outbreak of Simulium (Wilhelmia) spp. in the Cappadocia region of Turkey were calculated by summing losses to the livestock (dairy) industry and tourism (hotels), plus ongoing control expenditures. RESULTS More than 2.000.000 domestic and foreign tourists, 60.000 animals, and the local population were disturbed by the flies. Tourism was the most affected sector from the Simulium outbreak. CONCLUSION The calculated cost of the outbreak according to 2013 prices was 10.626.966 TL (US

Domestic cattle as a non-conventional amplifying host of vesicular stomatitis New Jersey virus.

5.45 million).

The Effect of Seston on Mortality of Simulium vittatum (Diptera: Simuliidae) from Insecticidal Proteins Produced by Bacillus thuringiensis subsp. israelensis

The role of vertebrates as amplifying and maintenance hosts for vesicular stomatitis New Jersey virus (VSNJV) remains unclear. Livestock have been considered dead‐end hosts because detectable viraemia is absent in VSNJV‐infected animals. This study demonstrated two situations in which cattle can represent a source of VSNJV to Simulium vittatum Zetterstedt (Diptera: Simuliidae) by serving: (a) as a substrate for horizontal transmission among co‐feeding black flies, and (b) as a source of infection to uninfected black flies feeding on sites where VSNJV‐infected black flies have previously fed. Observed co‐feeding transmission rates ranged from 0% to 67%. Uninfected flies physically separated from infected flies by a distance of up to 11 cm were able to acquire virus during feeding although the rate of transmission decreased as the distance between infected and uninfected flies increased. Acquisition of VSNJV by uninfected flies feeding on initial inoculation sites at 24 h, 48 h and 72 h post‐infection, in both the presence and absence of vesicular lesions, was detected.

Host predilection and transmissibility of vesicular stomatitis New Jersey virus strains in domestic cattle ( Bos taurus ) and swine ( Sus scrofa )

ABSTRACT Water was collected from a site on the Susquehanna River in eastern Pennsylvania, where less-than-optimal black fly larval mortality had been occasionally observed after treatment with Bacillus thuringiensis subsp. israelensis de Barjac insecticidal crystalline proteins (Bti ICPs). A series of experiments was conducted with Simulium vittatum Zetterstedt larvae to determine the water related factors responsible for the impaired response to Bti ICPs (Vectobac 12S, strain AM 65–52). Seston in the water impaired the effectiveness of the ICPs, whereas the dissolved substances had no impact on larval mortality. Individual components of the seston then were exposed to the larvae followed by exposure to Bti ICPs. Exposure of larvae to selected minerals and nutritive organic material before ICP exposure resulted in no significant decrease in mortality. Exposure of larvae to silicon dioxide, cellulose, viable diatoms, and purified diatom frustules before Bti ICP exposure resulted in significant reductions in mortality. Exposure of larvae to purified diatom frustules from Cyclotella meneghiniana Kützing resulted in the most severe impairment of mortality after Bti ICP exposure. It is postulated that frustule-induced impairment of feeding behavior is responsible for the impairment of larval mortality.

The Lack of Effect of Low Temperature and High Turbidity on Operational Bacillus thuringiensis Subsp. Israelensis Activity Against Larval Black Flies (Diptera: Simuliidae)

BackgroundEpidemiologic data collected during epidemics in the western United States combined with limited experimental studies involving swine and cattle suggest that host predilection of epidemic vesicular stomatitis New Jersey virus (VSNJV) strains results in variations in clinical response, extent and duration of virus shedding and transmissibility following infection in different hosts. Laboratory challenge of livestock with heterologous VSNJV strains to investigate potential viral predilections for these hosts has not been thoroughly investigated. In separate trials, homologous VSNJV strains (NJ82COB and NJ82AZB), and heterologous strains (NJ06WYE and NJOSF [Ossabaw Island, sand fly]) were inoculated into cattle via infected black fly bite. NJ82AZB and NJ06WYE were similarly inoculated into swine.ResultsClinical scores among viruses infecting cattle were significantly different and indicated that infection with a homologous virus resulted in more severe clinical presentation and greater extent and duration of viral shedding. No differences in clinical severity or extent and duration of viral shedding were detected in swine.ConclusionsDifferences in clinical presentation and extent and duration of viral shedding may have direct impacts on viral spread during epidemics. Viral transmission via animal-to-animal contact and insect vectored transmission are likely to occur at higher rates when affected animals are presenting severe clinical signs and shedding high concentrations of virus. More virulent viral strains resulting in more severe disease in livestock hosts are expected to spread more rapidly and greater distances during epidemics than those causing mild or inapparent signs.

Chironomus calligraphus (Diptera: Chironomidae), a New Pest Species in Georgia

Abstract Black fly suppression programs are conducted across a wide range of environmental conditions, targeting a variety of pest species with diverse life histories. Operational applications of Vectobac® 12AS (Bacillus thuringiensis subsp. israelensis) were conducted during times characterized by water temperature and turbidity extremes. Applications were conducted in the Yellow River in central Wisconsin targeting Simulium annulus and S. johannseni when water temperatures were 1–2°C. Applications were conducted in the Green River in western North Carolina targeting the S. jenningsi group after a rain event, when portions of the treatment zone experienced turbidities of 276 nephelometric turbidity units. Excellent larvicidal activity was observed in both programs, with 97% mortality or greater being observed at distances over 5 km downstream of a treatment site. Mortality data for larval black flies in 2 operational suppression programs conducted in 2011 demonstrated a negligible effect of near-freezing water temperatures and exceptionally high turbidity on Bti activity.