Biomedical subjects
W H Thompson
Publications and source records attributed to W H Thompson.
La Crosse encephalitis: occurrence of disease and control in a suburban area.
Fifteen (6.4%) of 233 residents sampled in State Road Coulee (SRC) during 1972-73 had antibodies neutralizing La Crosse (LAC) virus, 9 (3.9%) trivittatus (TVT), 12 (5.2%) Jamestown Canyon (JC) and 2 (0.9%) Bunyamwera serogroup virus. Six of seven youths who had antibodies to LAC virus had been ill: three were serologically confirmed as cases of LAC encephalitis and three had possibly related illnesses. The other reported no illness. Possibly related illnesses were reported by 1 of 10 adults with antibody to LAC; also by 3 of 6 youths who had antibodies to TVT or JC viruses, and by 4 of 39 youths who did not have these antibodies. In prospective studies, 4 of 132 sampled again during 1977 had acquired antibodies, including 2 to LAC and 2 to JC virus. The LAC disease-infection rate was 50%. One of those with antibody to LAC virus was a girl with encephalitis who had a serologically confirmed infection a year after she had moved away from SRC. Her exposure to mosquitoes was not in SRC. The other was a boy who remained a resident but did not have encephalitis or other severe illness. The two who had acquired antibody to JC virus were boys who reported histories of undiagnosed febrile illnesses while attending summer camps in central Wisconsin. Control measures, including closure of treeholes, removing old tires and education, were applied. LAC infections in SRC were reduced from six during 1965 thru 1972, to only one during 1973 thru 1977. No cases have been found in SRC since 1977. Following expansion to a county-wide control program, LAC encephalitis in La Crosse County has been reduced from seven and eight cases during 1978 and 1979 to only one and two during 1980 and 1981. No cases have been found in La Crosse County so far during 1982.
Vascular spindle cell lipoma.
Spindle cell lipoma is a neoplasm of adipose tissue that primarily affects posterior necks and shoulders of men in their fifth to seventh decades. It consists of a mixture of adipose tissue and spindle-shaped cells that could be misinterpreted as sarcoma. A clinical and pathological study of two patients, both men, with vascular variants of spindle cell lipoma is presented. These tumors were unusual clinically, in that one caused pain on motion and the other was painful to palpation. On microscopic examination, their vascularity was augmented over previously described examples of spindle cell lipoma.
Indirect fluorescent-antibody technique for serological diagnosis of La Crosse (California) virus infections.
A clinically relevant indirect fluorescent-antibody technique (IFA) was developed for the serological diagnosis of La Crosse virus infections. The IFA (67%) was as sensitive as the hemagglutination inhibition (58%) and neutralization (58%) tests in the detection of antibodies in acute-phase specimens. Immunoglobulin M antibodies were detected by the IFA test in 48% (11 of 23) of these specimens. Diagnostically significant increases in IFA titer were detected in 86% (19 of 22) of the paired samples. Antibodies were detectable in some patients 7 years after infection; however, the IFA test was not as sensitive as the other two tests in the detection of previous infections.
Genotypic varieties of La Crosse virus isolated from different geographic regions of the continental United States and evidence for a naturally occurring intertypic recombinant La Crosse virus.
The tripartite ribonucleic acid (RNA) genomes of 23 alternate isolates of La Crosse virus have been analyzed by the procedure of oligonucleotide fingerprinting. By comparison with the fingerprints of the three viral RNA species (large, medium and small) of prototype La Crosse virus, the viruses have been categorized in terms of the degree of their RNA sequence relatedness. The A type La Crosse viruses, which have been recovered from Wisconsin, Minnesota, Indiana and Ohio, have viral RNA sequences that are closely related to those of prototype La Crosse virus. The B type La Crosse viruses, which have been recovered from Minnesota, Wisconsin and Illinois, have RNA sequences which, although related, are easily distinguished from those of type A viruses. A La Crosse virus isolate obtained from Rochester, Minnesota, appears to be an intertypic type A/B recombinant, it has a small size RNA segment like those of the B type La Crosse virus isolates, but medium- and large-sized RNA species like those of the A type La Crosse virus isolates. The C type La Crosse viruses have viral RNA sequences that neither closely resemble the A or B type La Crosse viruses. They have been recovered from eastern Ohio, New York State, Texas, Georgia and North Carolina.
Effect of deflector shields fitted in the milking machine teatcup liner on bovine udder disease.
Deflector shields were inserted in the teatcup to prevent 'impacts' against the teat end, and their effect on the rate of new udder infections was studied on 15 commercial dairy farms in Britain and 16 in Australia. Small metal shields were fitted between the liner barrel and short milk tube of 2 teatcups in each cluster in a milking installation so that all cows in a herd always had the same 2 quarters shielded. Half-udder comparisons were made using 1039 cows in the British herds and 1268 in the Australian herds. Herds were quarter-sampled for cytological and bacteriological examination when shields were fitted at the start of the experiment and again after 6 months. The shield effects were similar in the 2 experiments. The combined results from the 31 farms showed that 10.5% fewer quarters became infected when protected by shields (P less than 0.05). In the 1287 cows that had no infected quarters at the start of the trial, 15% fewer quarters became infected when protected by shields (P less than 0.01). The shield effect was mainly confined to hind quarters in which 23% fewer shielded quarters became infected (P less than 0.001). The small reduction of 2% in forequarters was not significant. In the 16 herds in which post-milking disinfection of teats was practised, shielded quarters had 23.5% fewer new infections than unshielded quarters (P less than 0.01). In 6 British herds milked in installations classed as non-standard, shielded quarters had almost 50% fewer new infections than the unshielded quarters (0.05 less than P less than 0.10). The results provide evidence of a milking machine effect, at varying levels of intensity, to increase new infection rates on all or most farms. Control of this machine effect could lead to substantial reduction in new infections in some herds and a modest reduction in most.
A comparison of La Crosse virus isolated obtained from different ecological niches and an analysis of the structural components of California encephalitis serogroup viruses and other bunyaviruses.
Analyses of the oligonucleotide fingerprints of the three genome ribonucleic acid (RNA) species of 11 isolates of La Crosse (LAC) virus, obtained from various ecological niches in the northern United States and compared to those of prototype LAC virus, showed that in each place from which these isolates were obtained LAC variants and varieties were present with related, but distinguishable, nucleotide sequences for their large, medium, or small RNA species. The RNA genomes of prototypes trivittatus (TVT), snowshoe hare (SSH), Tahyna (TAH), and Lumbo (a variety of TAH) viruses of the California encephalitis (CE) serogroup, and Guaroa of the Bunyamwera serogroup also consist of three RNA species, each with unique and distinguishable nucleotide sequences which bear little resemblance to those of the LAC virus isolates. The virions of CE group viruses (CE, Jamestown Canyon, Keystone, LAC, Melao, SSH, TVT, TAH viruses and South River, an unregistered virus) have three major viral polypeptides, designated G1, G2, and N.
Higher venereal infection and transmission rates with La Crosse virus in Aedes triseriatus engorged before mating.
Infection of colonized female Aedes triseriatus by La Crosse (LAC) virus occurred more frequently when females were inseminated by infected males after the females engorged blood (49% of 39) than when mating took place before engorgement (4% of 554). Salivary transmission of LAC virus to mice also was more frequent in females venerally infected after engorgement on a normal mouse (35% of 34) than in females mated before engorgement (2% of 49). LAC virus was transovarially transmitted by 40% of 10 females mated by infected males, and in 64% of 279 progeny reared from eggs of second or later ovarian cycles.
Tropisms of La Crosse virus in Aedes triseriatus (Diptera: Culicidae) following infective blood meals.
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Diagnosis of California La Crosse virus infection by counterimmunoelectrophoresis.
La Crosse virus cell culture-derived soluble antigen was used in a counterimmunoelectrophoresis procedure to assess the presence or absence of La Crosse antibodies in 79 paired acute- and convalescent-phase human sera. The counterimmunoelectrophoresis test appeared to measure the same antibody as the complement fixation test but was more sensitive and rapid.
Venereal transmission of La Crosse virus from male to female Aedes triseriatus.
Horizontal transmission of La Crosse (LAC) arbovirus in colonized Aedes triseriatus was first observed in mating cages. LAC antigen was visualized by fluorescent antibody technique in multiple organs of 5 (2.5% of 198 females dissected after contact in mating cages with males, with a transovarial infection rate of 31%. Venereal transmission of LAC virus was demonstrated by limited contact induced mating. Antigen was detected in bursal contents of 35 (53%) of 66 females dissected within 24 h after induced mating by males previously infected by intrathoracic inoculation. Antigen was observed in ovaries, heart, gut, salivary glands, or other organs in 13 (3.4%) of 379 females dissected 1 to 14 days post-mating. LAC virus was isolated from infected males, from contents of the bursa copulatrix of females following mating, and from dissection remnants of 6 of the 13 females in which disseminated antigen had been observed. Venereally infected females were shown to be capable of transmission of LAC virus by bite to mice and to eggs.
Venereal transmission of La Crosse (California encephalitis) arbovirus in Aedes triseriatus mosquitoes.
Veneral transmission of La Crosse virus by males of Aedes triseriatus was demonstrated. La Crosse virus was detected in the bursa of females after induced copulation, and disseminated infection was shown to occur occasionally. Since males of Aedes triseriatus have transovarial filial infection rates similar to those of females and can repeatedly mate, veneral transmission may be an important supplement to other natural endemic maintenance mechanisms.
Delineation of La Crosse virus in developmental stages of transovarially infected Aedes triseriatus.
The tropisms and development of La Crosse (LAC) virus in stages of transovarially infected Aedes triseriatus were studied with fluorescent antibody (FA) stained dissected organs and titrations of individual arthropods in suckling mice. Viral antigen was detected by FA in 95 of 387 dissected larvae, pupae, and adults. In larvae highest levels of fluorescence were detected in the alimentary tract, followed by ganglia, malpighian tubule, muscle, and other tissues. No specific organs or germ layer-derived tissues appeared to be the sole source of viral replication. Most tissues and organs of A. triseriatus are capable of maintaining LAC virus. Antigen was detected in the identifiable organs immediately upon emergence from the egg. In pupae and adults antigen was detected at high levels in foregut, gonadal and associated tissues, and in salivary glands, which would indicate females could be infective upon emergence. Virus was isolated from all arthropod stages, in 32 of 130 individuals inoculated into suckling mice. Titrations ranged from less than 1.0 log10 SMICLD50 per 0.02 ml for eggs and 1st instar larvae to 3.0 log10 SMICLD50 for 4th instar larvae. Adults and pupae averaged between 2.0 and 3.0 log10 SMICLD50. Increases in titer during maturation were mainly related to increases in size of the organism rather than in titer per unit volume.
Transovarial transmission of LaCrosse virus in Aedes triseriatus.
As part of a continuing investigation on the ecology of LaCrosse virus in Wisconsin, field and laboratory studies were conducted to explore the possibility that the virus is transmitted transovarially in A. triseriatus mosquitoes. In laboratory experiments, A. triseriatus mosquitoes were infected by ingesting LaCrosse virus in defibrinated blood. LaCrosse virus was recovered from F1 eggs, larvae, and adults that originated from the infected parent mosquitoes. In a subsequent field study aimed at determining if transovarial transmission accounted for the survival of LaCrosse virus during the winter season, larvae that originated from overwintering A. triseriatus eggs were collected from a LaCrosse virus enzootic area in southwestern Wisconsin. LaCrosse virus was isolated from these larvae and from adult A. triseriatus that were reared from field-collected larvae. These findings strongly imply that A. triseriatus is the reservoir of LaCrosse virus and that transovarial transmission is the mechanism responsible for the maintenance of the virus during the winter season in the north central region of the United States.
Emergence of La Crosse virus from endemic foci. Fluorescent antibody studies of overwintered Aedes triseriatus.
The frequency and distribution of La Crosse (LAC) virus overwintering in Aedes triseriatus diapause eggs were studied during 1974 by following 64 tree-hole oviposition sites in four enzootic hardwood forest areas. A direct fluorescent antibody technique, adapted for detection of LAC virus in individual mosquitoes, proved to be a rapid, reliable and economical tool for ascertaining true field infection rates. Virus was found in larvae from each of the four study areas before the seasonal emergence of adults and detected in 10 (0.6%) of 1,698 individually processed adults reared from collected larvae. In one of these study areas, all 12 located tree-holes were enclosed with screen before the seasonal emergence of adults, to ensure that all collected from these sites originated from overwintered eggs. Of 1,280 Aedes triseriatus processed from this area throughout the season, 16 (1.2%) contained virus. Isolates were found in overwintered Aedes triseriatus throughout the summer months, demonstrating the role of these tree-hole sites as foci for both overwintering and continuing summer season source of LAC virus in these forested areas.
Isolation of La Crosse virus from field collected Aedes triseriatus larvae.
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Overwintering of La Crosse virus in Aedes triseriatus.
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Observations on a natural cycle of La Crosse virus (California group) in Southwestern Wisconsin.
Ecological studies were conducted to document the role of the eastern chipmunk (Tramias striatus) as a vertebrate host for La Crosse (LAC) virus in nature during late summer when Aedes triseriatus mosquitoes are most abundant. Movement, home range and density of chipmunk populations were determined by trap mark and recapture techniques on grid study areas. The temporal distribution of A. triseriatus was estimated by use of oviposition traps. Passive antibodies were found in spring-born juveniles captured prior to mid-July and in summer-born juveniles in September. Active antibodies neutralizing LAC virus were first detected in susceptible chipmunks in mid-July and 68 free-living and 4 sentinel animals developed antibodies during the study. Virus transmission continued at a high rate through August but was not detected in September. Chipmunk habitat was ranked for quality and populations of chipmunks. A. triseriatus were more abundant in study areas with most suitable chipmunk habitat. Populations of A. triseriatus were temporally associated with the elaboration of antibodies in chipmunks. In one study area, antibody prevalence rates in adult and spring-born juveniles reached 100% by September. Findings implicate A. triseriatus as the vector and establish chipmunks as important amplifying hosts in discontinuous foci of virus transmission.