Cases Of La Crosse Encephalitis Research Articles

Notes from the Field: Spatially Associated Coincident and Noncoincident Cases of La Crosse Encephalitis - North Carolina, 2002-2017.

Notes from the Field: Spatially Associated Coincident and Noncoincident Cases of La Crosse Encephalitis - North Carolina, 2002-2017.

Severe La Crosse meningoencephalitis in children: report of two cases

La Crosse virus is an arbovirus of the California Serogroup (Family Bunyaviridae), transmitted by the “tree-hole mosquito,” Aedes triseriatus . La Crosse encephalitis cases occur annually from July to October. The majority of cases are asymptomatic, only a minority (

Cemeteries are effective sites for monitoring la crosse virus (LACv) and these environments may play a role in LACv infection.

La Crosse encephalitis (LAC) is the leading arboviral disease among children, and was previously limited to the upper Midwest. In 2012 nine pediatric cases of LAC occurred in eastern Tennessee, including one fatal case. In an attempt to identify sites near an active LACv infection and describe the abundance and distribution of potential LACv vectors near a fatal LAC case in the Appalachian region, we initiated an end of season study using a combination of questing and oviposition mosquito traps placed at forty-nine sites consisting of cemeteries and houses within 16 radial kilometers of two pediatric infections. LACv was isolated from three Aedes triseriatus pools collected from cemeteries and spatial clustering analysis identified clusters of Ae. triseriatus and Ae. albopictus populations that overlapped in the same area as the 2012 LACv cases. Results indicate cemeteries are effective sites for monitoring LACv. The role of cemeteries and specific environmental features will be the focus of future investigations.

Clinical comparisons of La Crosse encephalitis and enteroviral central nervous system infections in a pediatric population: 2001 surveillance in East Tennessee

Background La Crosse encephalitis (LAC) is a mosquito-borne illness that primarily affects children. In 1997, an initial cluster of cases was identified by the regional pediatric referral center in East Tennessee. Since that time, public health officials, pediatric infectious disease physicians, infection control nurses, laboratory personnel, entomologists, and Centers for Disease Control and Prevention consultants have collaborated to provide ongoing surveillance activities. Studies comparing LAC cases with non-LAC (no etiologic diagnosis) central nervous system infections have yielded no statistical significance in signs and symptoms or laboratory values. Objective To determine any differences in signs, symptoms, and/or diagnostic laboratory values between LAC cases and enteroviral central nervous system (EV-CNS) infections. Methods In 2001, descriptive public health surveillance for LAC was performed concurrent with an outbreak investigation of EV-CNS infections at a pediatric referral center in East Tennessee. All patients being evaluated for suspected meningitis and/or encephalitis were interviewed for signs and symptoms of illness. Patients with positive test results for LAC and negative results for EV or positive results for EV and negative results for LAC were included in the study. Results Compared with patients with EV-CNS infection, patients with LAC were significantly more likely to have aphasia ( P = .001), loss of consciousness ( P = .0003), seizure ( P = .0003), and admission to the pediatric intensive care unit ( P = .02). Presence of fever, headache, vomiting, stiff neck (subjective), photophobia, behavioral changes, confusion, need for mechanical ventilation, age, and sex showed no statistical significance ( P > .05). Statistical differences were not demonstrated in cerebrospinal fluid laboratory values ( P > .05). Conclusion Patients with LAC demonstrated more severe symptoms on presentation to the hospital than did patients with EV-CNS infection. A possible advantage of identifying specific viral etiologic factors of pediatric CNS disease by clinical characteristics may be the ability to take advantage of emerging antiviral therapies.

Habitat preferences and phenology of Ochlerotatus triseriatus and Aedes albopictus (Diptera: Culicidae) in southwestern Virginia.

Recently, the number of reported human cases of La Crosse encephalitis, an illness caused by mosquito-borne La Crosse virus (LAC), has increased in southwestern Virginia, resulting in a need for better understanding of the virus cycle and the biology of its vectors in the region. This study examined the spatial and temporal distributions of the primary vector of LAC, Ochlerotatus triseriatus (Say), and a potential secondary vector, Aedes albopictus (Skuse). Ovitrapping surveys were conducted in 1998 and 1999 to determine distributions and oviposition habitat preferences of the two species in southwestern Virginia. Mosquitoes also were collected for virus assay from a tire dump and a human La Crosse encephalitis case site between 1998 and 2000. Oc. triseriatus and Ae. albopictus were collected from all ovitrap sites surveyed, and numbers of Oc. triseriatus eggs generally were higher than those of Ae. albopictus. Numbers of Oc. triseriatus remained high during most of the summer, while Ae. albopictus numbers increased gradually, reaching a peak in late August and declining thereafter. In Wise County, relative Ae. albopictus abundance was highest in sites with traps placed in open residential areas. Lowest numbers of both species were found in densely forested areas. Ovitrapping during consecutive years revealed that Ae. albopictus was well established and overwintering in the area. An oviposition comparison between the yard and adjacent forest at a human La Crosse encephalitis case site in 1999 showed that Ae. albopictus preferentially oviposited in the yard surrounding the home, but Oc. triseriatus showed no preference. LAC isolations from larval and adult collections of Oc. triseriatus females from the same case site indicated the occurrence of transovarial transmission.

Serological survey and active surveillance for La Crosse virus infections among children in Tennessee.

In 1998 and 1999, we performed a serosurvey and active surveillance for La Crosse encephalitis at a children's hospital in eastern Tennessee. Fifteen cases of La Crosse encephalitis were confirmed. Only 5 (0.5%) of 1000 serum samples being tested at the state laboratory for other diseases had evidence of antibodies to La Crosse virus. These findings suggest that La Crosse virus is newly endemic to eastern Tennessee.

La Crosse encephalitis virus habitat associations in Nicholas County, West Virginia.

Aedes triseriatus (Say) population density patterns and La Crosse encephalitis virus infection rates were evaluated in relation to a variety of habitat parameters over a 14-wk period. Ovitraps and landing collections were used in a La Crosse virus-enzootic area in Nicholas County, WV. Study sites were divided into categories by habitat type and by proximity to the residences of known La Crosse encephalitis cases. Results demonstrated that Ae. triseriatus population densities were higher in sugar maple/red maple habitats than in hemlock/mixed hardwood habitats or in a site characterized by a large number of small red maple trees. Sites containing artificial containers had higher population densities than those without. La Crosse virus minimum infection rates in mosquitoes collected as eggs ranged from 0.4/1,000 to 7.5/1,000 in the 12 study sites, but did not differ significantly among sites regardless of habitat type or proximity to human case residences. La Crosse virus infection rates in landing Ae. triseriatus mosquitoes ranged from 0.0/1,000 to 27.0/1,000. La Crosse virus was also isolated from host-seeking Ae. canadensis (Theobald) in two study sites, at rates similar to those found in the Ae. triseriatus populations. The Ae. triseriatus oviposition patterns and La Crosse virus infection rates suggest that this mosquito species disperses readily in the large woodlands of central West Virginia. The La Crosse enzootic habitats in Nicholas County, WV, are contrasted with those studied in other geographic regions where La Crosse virus is found.

Newly recognized focus of La Crosse encephalitis in Tennessee.

La Crosse virus is a mosquito-borne arbovirus that causes encephalitis in children. Only nine cases were reported in Tennessee during the 33-year period from 1964-1996. We investigated a cluster of La Crosse encephalitis cases in eastern Tennessee in 1997. Medical records of all suspected cases of La Crosse virus infection at a pediatric referral hospital were reviewed, and surveillance was enhanced in the region. Previous unreported cases were identified by surveying 20 hospitals in the surrounding 16 counties. Mosquito eggs were collected from five sites. Ten cases of La Crosse encephalitis were serologically confirmed. None of the patients had been discharged from hospitals in the region with diagnosed La Crosse encephalitis in the preceding 5 years. Aedes triseriatus and Aedes albopictus were collected at the case sites; none of the mosquitos had detectable La Crosse virus. This cluster may represent an extension of a recently identified endemic focus of La Crosse virus infection in West Virginia.

La Crosse and other forms of California encephalitis.

The California serogroup viruses are mosquito viruses that cause human infections on five continents. They are maintained and amplified in nature by a wide variety of mosquito vectors and mammalian hosts; they thrive in a remarkably wide variety of microclimates (eg, tropical, coastal temperate marshland, lowland river valleys, alpine valleys and highlands, high boreal deserts, and arctic steppes). In 1993, California serogroup viruses caused 71% of all cases of arboviral illness in the United States, principally La Crosse encephalitis. The 30 to 180 annual cases of La Crosse encephalitis represent 8% to 30% of all cases of encephalitis, rendering this illness the most common and important endemic mosquito-borne illness in the USA. Subclinical or mild infections are much more common. Methods and results acquired from intense study of California serogroup viruses have been applied, with benefit, to the study of the ecology and pathogenesis of many more serious human arboviral illnesses. The evolutionary potential of viruses, with particular reference to the development of more virulent strains, has been studied more closely in the California serogroup viruses than in almost any other agent of human disease.

Spatial analysis of the distribution of LaCrosse encephalitis in Illinois, using a geographic information system and local and global spatial statistics.

The spatial and temporal distribution of LaCrosse encephalitis cases in Illinois was analyzed using a geographic information system (GIS) and spatial statistics. Case data were obtained from the Illinois Department of Public Health and mapped on the county, town, and address level. Human cases were concentrated in and around the city of Peoria in central Illinois. Local spatial statistics were used to identify hot spots where cases appear to be concentrated in the Peoria region. Several small towns surrounding the city of Peoria appeared as foci where cases were most common. Second-order spatial analysis of the case distribution was conducted on the address level. Cases were clustered within a range of 3.0 km in the city of Peoria. Since most cases appear to be associated with residential (peridomestic) exposure, and since several cases have been reported from neighboring addresses, transmission may be concentrated around specific sites (hardwood ravines, tire piles). The GIS and spatial analysis may be useful in identifying and targeting for intervention potential sites of enzootic transmission.

Surveillance of arbovirus activity in Iowa, USA, 1978-1980.

Considerable information pertaining to the epidemiology of mosquito-borne viruses in Iowa, USA, has been acquired during a continuing arbovirus surveillance program. Virus isolation results indicate that Culex tarsalis is the primary vector of St. Louis encephalitis (SLE) and western equine encephalomyelitis (WEE) viruses in Iowa, but that Culex spp. ( Cx. pipiens, Cx. restuans, or Cx. salinarius ) may contribute to the amplification of SLE virus. Also, Aedes trivittatus may be important in the natural maintenance of WEE virus in Iowa. From 1978 through 1980, a total of 243 isolations of viruses such as Flanders and trivittatus were made from various species of mosquitoes in Iowa. Many of the wild-bird bloods tested had hemagglutination-inhibition (HI) antibodies (titer ≥ 20) to WEE virus, and a few had antibodies to SLE in Council Bluffs, where a human case occurred in 1980. Eighteen human cases of La Crosse encephalitis occurred in Iowa in 1978, and a 3-year-old girl who lived near the Iowa state line died from the effects of this virus. La Crosse virus was isolated from a pool of Aedes triseriatus collected in Dubuque, where a human case occurred in 1979 and a 2nd case occurred in 1980.

Occurrence of La Crosse (California Serogroup) Encephalitis Viral Infections in Illinois *

La Crosse (LAC) virus (California encephalitis serogroup) was identified as the etiologic agent of disease in 61 cases of California encephalitis (CE) that occurred in Illinois between 1976 and 1980. This group represented 54% of all 114 laboratory-diagnosed cases of CE between 1966 and 1980. Key epidemiologic observations included: 88% of the 61 cases had onset in July, August, or September; the 5- to 9-year-old age group represented 48% of the cases; the male:female sex ratio was 2:1; 97% of the cases occurred in the northern half of the state; and 61% of the cases occurred in Peoria County. Four instances of probable common source of exposure were reported. Average length of hospitalization was 8.3 days (range 3-31 days). Hospitalization costs were estimated at $3,967-$5,750 per case. An "average" year in Illinois yields 12 cases of LAC encephalitis with direct hospitalization costs of $47,604-$69,000.