Phylogenetic and virulence analysis of tick-borne encephalitis virus field isolates from Switzerland

Tick-borne encephalitis (TBE) is an endemic disease in Switzerland, with about 110-120 reported human cases each year. Endemic areas are found throughout the country. However, the viruses circulating in Switzerland have not been characterized so far. In this study, the complete envelope (E) protein sequences and phylogenetic classification of 72 TBE viruses found in Ixodes ricinus ticks sampled at 39 foci throughout Switzerland were analyzed. All isolates belonged to the European subtype and were highly related (mean pairwise sequence identity of 97.8% at the nucleotide and 99.6% at the amino acid level of the E protein). Sixty-four isolates were characterized in vitro with respect to their plaque phenotype. More than half (57.8%) of isolates produced a mixture of plaques of different sizes, reflecting a heterogeneous population of virus variants. Isolates consistently forming plaques of small size were associated with recently detected endemic foci with no or only sporadic reports of clinical cases. All of six virus isolates investigated in an in vivo mouse model were highly neurovirulent (100% mortality) but exhibited a relatively low level of neuroinvasiveness, with mouse survival rates ranging from 50% to 100%. Therefore, TBE viruses circulating in Switzerland belong to the European subtype and are closely related. In vitro and in vivo surrogates suggest a high proportion of isolates with a relatively low level of virulence, which is in agreement with a hypothesized high proportion of subclinical or mild TBE infections.

Equine botulism and acute pasture myodystrophy: new soil-borne emerging diseases in Switzerland?

In Switzerland, the incidence of equine botulism and acute pasture myodystrophy have remarkably increased in the last five years. Equine fodder-borne botulism in Europe is most likely caused by Clostridium botulinum types C and D that produce the toxins BoNT/C and BoNT/D. Horses showing signs suggestive of botulism (muscle weakness and tremors, reduced tongue tone, slow chewing, salivation and difficulties swallowing, drooping eyelids, mydriasis), especially patients that have fed on suspect fodder (mostly haylage), must be treated with anti-serum as soon as possible.They also need intensive care, which is often difficult to provide and always expensive in the face of a guarded to poor prognosis. Therefore, prevention (high standards of forage quality and vaccination) is all the more important. Pasture myodystrophy is an acute disease with signs of rhabdomyolysis and lethality rate over 90%. It affects grazing horses under frosty, windy and rainy conditions. Preliminary results indicate that Clostridium sordellii and Clostridium bifermentans producing lethal toxin may play a role in pasture myodystrophy. Our efforts concentrate on developing a new subunit vaccine for equine botulism and understanding the ethiology and pathogenesis of pasture myodystrophy with the goal of improving prevention against these highly fatal diseases that present a significant risk to our horse population.

Investigation of the Potential Effects of Epizootic Hemorrhagic Disease Virus on Iowa Cattle

Epizootic hemorrhagic disease virus (EHDV), an arthropod-borne orbivirus, causes significant mortality in white-tailed deer and can also cause disease in cattle. Objectives of this preliminary investigation were 1) to survey cattle at auction markets to determine the prevalence of anti-EHDV antibodies in Iowa cattle, 2) to determine EHDV seroprevalence in herds in which clinical EHD had been diagnosed, and 3) to determine whether EHDV is associated with stillbirths and/or congenital anomalies in calves. There was a 15% seroprevalence in auction market cattle; positive cattle were from southern, central, and western Iowa. Herds in which clinical EHD had been diagnosed had >60% seroprevalence. Viremia was detected in both clinically affected and unaffected cattle during an EHD outbreak. EHDV exposure was not consistently associated with congenital anomalies. Although additional surveillance is warranted, EHDV is unlikely to have a significant effect on the reproductive health of Iowa cattle.

The dynamic proteome of Lyme disease Borrelia.

The proteome of the spirochete bacterium Borrelia burgdorferi, the tick-borne agent of Lyme disease, has been characterized by two different approaches using mass spectrometry, providing a launching point for future studies on the dramatic changes in protein expression that occur during transmission of the bacterium between ticks and mammals.

Antigenic variation in Lyme disease spirochetes by segmental recombination of VMP-like sequence cassettes

Lyme disease is a multisystemic disorder caused by tick-borne infection of humans or other mammalian hosts with Borrelia burgdorferi. If untreated, the spirochetes can persist in the mammalian host for months or years. The mechanisms by which Lyme disease spirochetes evade the immune response have not been determined. In this study, we have identified and characterized an elaborate genetic system in the Lyme disease spirochete B. burgdorferi that promotes extensive antigenic variation of a 34-kDa surface-exposed lipoprotein, VlsE. A 28-kilobase linear plasmid of B. burgdorferi B31 (lp28-1) was found to contain a vmp-like sequence (vls) locus that closely resembles the variable major protein (vmp) system for antigenic variation of relapsing fever organisms. The presence of lp28-1 correlates with the high-infectivity phenotype in B. burgdorferi strains tested. Segments of the 15 non-expressed (silent) vls cassette sequences located upstream of vlsE are able to recombine into the centra vlsE cassette region during infection of C3H/HeN mice, resulting in antigenic variation of the expressed lipoprotein. When compared to parental VlsE, VlsE variants progressively accumulate sequence changes during the period of 4, 7, 14, 21, and 28 days post infection in C3H/HeN mice. However, no recombination was detected during the period of 28-day in vitro culture, suggesting in vivo induction of VlsE antigenic variation. Adaptive immune responses do not appear to play a significant role in this induction, since similar recombination events were also observed in immunodeficient SCID mice. The $5\sp\prime$ and $3\sp\prime$ noncassette regions of vlsE are apparently not subject to recombination and sequence variation. The structure and sequence of the silent vls cassette locus is preserved during the process of the VlsE antigenic variation, consistent with a nonreciprocal recombination mechanism. This combinatorial form of antigenic variation could potentially yield millions of VlsE variants in the mammalian host, and thereby contribute to immune evasion, long-term survival, and pathogenesis of B. burgdorferi. ^

A tick-borne encephalitis model in infant rats infected with langat virus

Tick-borne encephalitis virus (TBEV) is the causative agent of human TBE, a severe infection that can cause long-lasting neurologic sequelae. Langat virus (LGTV), which is closely related to TBEV, has a low virulence for human hosts and has been used as a live vaccine against TBEV. Tick-borne encephalitis by natural infection of LGTV in humans has not been described, but one of 18,500 LGTV vaccinees developed encephalitis. The pathogenetic mechanisms of TBEV are poorly understood and, currently, no effective therapy is available. We developed an infant rat model of TBE using LGTV as infective agent. Infant Wistar rats were inoculated intracisternally with 10 focus-forming units of LGTV and assessed for clinical disease and neuropathologic findings at Days 2, 4, 7, and 9 after infection. Infection with LGTV led to gait disturbance, hypokinesia, and reduced weight gain or weight loss. Cerebrospinal fluid concentrations of RANTES, interferon-γ, interferon-β, interleukin-6, and monocyte chemotactic protein-1 were increased in infected animals. The brains of animals with LGTV encephalitis exhibited characteristic perivascular inflammatory cuffs and glial nodules; immunohistochemistry documented the presence of LGTV in the thalamus, hippocampus, midbrain, frontal pole, and cerebellum. Thus, LGTV meningoencephalitis in infant rats mimics important clinical and histopathologic features of human TBE. This new model provides a tool to investigate disease mechanisms and to evaluate new therapeutic strategies against encephalitogenic flaviviruses.

Prevalence estimation of tick-borne encephalitis virus (TBEV) antibodies in dogs from Finland using novel dog anti-TBEV IgG MAb-capture and IgG immunofluorescence assay based on recombinant TBEV subviral particles

Tick-borne encephalitis (TBE) is one of the most dangerous human neurological infections occurring in Europe and Northern parts of Asia with thousands of cases and millions vaccinated against it. The risk of TBE might be assessed through analyses of the samples taken from wildlife or from animals which are in close contact with humans. Dogs have been shown to be a good sentinel species for these studies. Serological assays for diagnosis of TBE in dogs are mainly based on purified and inactivated TBEV antigens. Here we describe novel dog anti-TBEV IgG monoclonal antibody (MAb)-capture assay which is based on TBEV prME subviral particles expressed in mammalian cells from Semliki Forest virus (SFV) replicon as well as IgG immunofluorescence assay (IFA) which is based on Vero E6 cells transfected with the same SFV replicon. We further demonstrate their use in a small-scale TBEV seroprevalence study of dogs representing different regions of Finland. Altogether, 148 dog serum samples were tested by novel assays and results were compared to those obtained with a commercial IgG enzyme immunoassay (EIA), hemagglutination inhibition test and IgG IFA with TBEV infected cells. Compared to reference tests, the sensitivities of the developed assays were 90-100% and the specificities of the two assays were 100%. Analysis of the dog serum samples showed a seroprevalence of 40% on Åland Islands and 6% on Southwestern archipelago of Finland. In conclusion, a specific and sensitive EIA and IFA for the detection of IgG antibodies in canine sera were developed. Based on these assays the seroprevalence of IgG antibodies in dogs from different regions of Finland was assessed and was shown to parallel the known human disease burden as the Southwestern archipelago and Åland Islands in particular had considerable dog TBEV antibody prevalence and represent areas with high risk of TBE for humans.

Health education intervention to reduce risk of infectious disease transmission among community health workers and their clients

Indigent and congregate-living populations have high susceptibilities for disease and pose a higher risk for disease transmission to family, friends and to persons providing services to these populations. The adoption of basic infection control, personal hygiene, safe food handling and simple engineering practices will reduce the risk of infectious disease transmission to, from and among indigent and congregate-living populations. ^ The provision of social services, health promotion activities and other support services to indigent and congregate-living populations is an important aspect of many public health-related governmental, community-based and other medical care provider agencies. ^ In the interest of protecting the health of indigent and congregate-living populations, of personnel from organizations providing services to these populations and of the general community, an educational intervention is warranted to prevent the spread of blood-borne, air-borne, food-borne and close contact-borne infectious diseases. ^ An educational presentation was provided to staff from a community-based organization specializing in providing housing, health education, foodstuffs and meals and support services to disabled, low-income, homeless and HIV-infected individuals. The educational presentation delivered general best practices and standard guidelines. A pre and post test were administered to determine and measure knowledge pertinent to controlling the spread of infectious diseases between and among homeless shelter-living clients and between clients and the organization's staff. ^ Comparing pre-test and post-test results revealed areas of knowledge currently held by staff and other areas that staff would benefit from additional educational seminars and training. ^

Epidemiology and control of vector-borne diseases /

Bibliography: p. 37-38.

Mosquito investigations, Milk River irrigation project, Montana, with particular reference to causes of mosquito production in a long-established irrigated area characterized by flat topography and heavy soils.

Mode of access: Internet.

Mosquito problems in irrigated areas and their prevention.

Mode of access: Internet.

Proceedings of the Conference on the Relation of Birds to Arthropod-borne Viruses : Atlanta, Ga., Feb. 16 & 17, 1962.

Mimeographed.

The 2014 chikungunya virus outbreak in the U.S. Virgin Islands: epidemiology, long-term health outcomes, and economic burden

Thesis (Ph.D.)--University of Washington, 2016-06

Population structure of the peridomestic mosquito Ochlerotatus notoscriptus in Australia

Ochlerotatus notoscriptus (Skuse) (Diptera: Culicidae) is the predominant peridomestic mosquito in Australia where it is the primary vector of dog heartworm, Dirofilaria immitis (Leidy), and a potentially important vector of arboviruses (Barmah Forest, Ross River) with geographical variation of vector competence. Although widespread, Oc. notoscriptus has low dispersal ability, so it may have isolated subpopulations. The identification of gene flow barriers may assist in understanding arbovirus epidemiology and disease risk, and for developing control strategies for this species. We investigated the population structure of Oc. notoscriptus from 17 sites around Australia, using up to 31 putative allozyme loci, 11 of which were polymorphic. We investigated the effect of larval environment and adult morphology on genetic variation. At least five subpopulations were found, four in New South Wales (NSW) and one unique to Darwin. Perth samples appear to be a product of recent colonization from the Australian east coast. For NSW sites, a Mantel test revealed an isolation by distance effect and spatial autocorrelation analysis revealed an area of effective gene flow of 67 km, which is high given the limited dispersal ability of this species. No consistent difference was observed between 'urban' and 'sylvan' habitats, which suggests frequent movement between these sites. However, a finer-scaled habitat study at Darwin revealed small but significant allele frequency differences, including for Gpi. No fixed allozyme differences were detected for sex, size, integument colour or the colour of species-diagnostic pale scales on the scutum. The domestic habit of Oc. notoscriptus and assisted dispersal have helped to homogenize this species geographically but population structure is still detectable on several levels associated with geographical variation of vector competence.