Zina Juřicová

Serologic survey of birds for West Nile Flavivirus in southern Moravia (Czech Republic).

A serosurvey for West Nile virus (WNV) was carried out in 54 domestic birds (geese and ducks bred on fishponds) and 391 wild birds representing 28 migratory and resident species, using a plaque-reduction neutralization microtest with Vero cells and Egyptian topotype Eg-101 strain as test virus. The birds were sampled in the South-Moravian fishpond ecosystem between 2004 and 2006. Antibodies to WNV were not detected in domestic waterfowl, but 23 (5.9%) free-living birds of 10 species showed a positive response. These were the common coot (Fulica atra, 5 positive/18 examined), common kingfisher (Alcedo atthis, 1/1), reed warbler (Acrocephalus scirpaceus, 2/80), sedge warbler (A. schoenobaenus, 3/80), marsh warbler (A. palustris, 2/28), Savis warbler (Locustella luscinioides, 3/12), reed bunting (Emberiza schoeniclus, 1/28), blackcap (Sylvia atricapilla, 2/11), penduline tit (Remiz pendulinus, 1/14), blue tit (Parus caeruleus, 1/1), and starling (Sturnus vulgaris, 2/4). The antibody titers were comparatively low (1:20-1:40), and the only high titer (1:160) was found in an adult marsh warbler. When 14 of the sera reacting with WNV were titrated in parallel with Usutu Flavivirus, 12 were interpreted as having specific antibodies to WNV, one coot had a higher titer against Usutu virus, and another one could not be attributed to either of the two viruses. In conclusion, 13 (3.3%) of 391 wild birds had specific antibodies to WNV. The results indicate that WNV activity in southern Moravia was limited during 2004-2006.

Mosquito (Diptera: Culicidae) Surveillance for Arboviruses in an Area Endemic for West Nile (Lineage Rabensburg) and Ťahyňa Viruses in Central Europe

ABSTRACT Six viral isolates were obtained from 23,243 female mosquitoes (examined in 513 pools) belonging to 16 species and collected along the lower reaches of the Dyje River in South Moravia (Czech Republic, central Europe) during 2006–2008: five isolates of Orthobunyavirus Ťahyňa (TAHV, California group, family Bunyaviridae: three isolations from Aedes vexans (Meigen), one from Ae. sticticus (Meigen), one from Culex modestus Ficalbi); and one isolation of Flavivirus West Nile (WNV, Japanese encephalitis group, family Flaviviridae)-strain Rabensburg (proposed lineage 3 of WNV) from Ae. rossicus (Dolbeshkin et al). All viral isolates were recovered from mosquitoes collected in 2006 (15,882 mosquitoes examined). while no virus was isolated from mosquitoes trapped in 2007 and 2008, when 1,555 and 5,806 mosquitoes were examined, respectively. The population density of local mosquitoes was very low in 2007 and 2008 because of warm and dry summer including a considerably low water table, compared with environmental conditions favorable for mosquito development in 2006. The virus isolation procedure was based on intracerebral inoculation of newborn mice. In parallel, more than one-third of the samples (183 pools consisting of 8,470 individual mosquitoes) were also examined by inoculating Vero cell cultures in Leighton tubes. However, the latter method detected only three of the six virus isolates (including WNV-Rabensburg). Ae. rossicus is a new potential vector for WNV-Rabensburg. This species feeds mostly on mammals including man; this raises the question whether this virus lineage is not adapted to an alternative mosquito-mammal cycle in the South-Moravian natural focus.

Longitudinal surveillance of the tick Ixodes ricinusfor borreliae

Host‐seeking Ixodes ricinus (L.) (Acari: Ixodidae) were monitored for borreliae (Borrelia burgdorferi s.l.) using dark‐field microscopy in South Moravia (Czech Republic) each May from 1991 to 2001 (150 nymphs, 100 females and 100 males each year). This survey revealed a mean annual percentage of infected ticks of 16.8% (range, 11.7–24.2) in nymphs, 24.9% (range, 16.5–33.6) in females and 26.1% (range, 17.1–37.3) in males. Annual incidence of Lyme borreliosis in humans of the area in the same period (range, 8.7–41.7 per 100 000) correlated significantly with the frequency (number of ticks per flag per hour) of nymphs infected with >50 borreliae or all nymphal ticks, but not with the frequency of females, infected females or the infection rate (% of ticks infected) of either nymphal or female ticks. A prediction of the annual incidence of Lyme borreliosis, based on the frequency of heavily infected or all nymphal I. ricinus ticks, is feasible. The infection rate in I. ricinus correlated significantly with the North Atlantic Oscillation winter index of the last year (in nymphs) or of the year before last (in adults).

Effect of forest clearing on the abundance of Ixodes ricinus ticks and the prevalence of Borrelia burgdorferi s.l.

Abstract.  Questing Ixodes ricinus L. (Acari: Ixodidae) ticks were collected on a forest trail that had been completely cleared of shrubs and ground vegetation in winter 2002 and on a nearby control uncleared forest transect in South Moravia (Czech Republic). Samples were collected each May in 2003, 2004 and 2005. Nymphal ticks were 3.4 times, 1.9 times and 1.2 times less frequent on cleared forest than on uncleared forest trails in the three respective years, whereas adult tick abundance was 27.2 times, 4.0 times and 2.2 times lower, respectively. The ticks were examined for borreliae by dark‐field microscopy: prevalence of nymphal ticks infected with Borrelia burgdorferi sensu lato (12.6% to 20.0%) did not differ significantly between the cleared and uncleared trail during the 3 years. In conclusion, the habitat modification appeared to result in a decreased abundance of I. ricinus as well as a reduced frequency of infected ticks (and thus indirectly a lower potential risk of Lyme borreliosis), which lasted, however, for only 2 years. Eight cultures of borreliae isolated from the ticks were all identified as the ‘ornithophilic’ genomic species Borrelia garinii, possibly indicating a greater role of forest birds than that of forest rodents as the hosts of immature I. ricinus in the tick (and borrelial) colonization of the cleared part of the forest.

Serological survey of domestic animals for tick-borne encephalitis and Bhanja viruses in northeastern Hungary

Blood sera collected from 400 domestic animals (260 cattle, 100 Merino sheep, and 40 Hutzul horses) in northeastern Hungary in 2005 were examined for antibodies against two tick-borne viruses, tick-borne encephalitis flavivirus (TBEV) and Bhanja bunyavirus (BHAV). Using ELISA as screening test and plaque-reduction neutralization as confirmatory test, seropositivity to TBEV was found to be 26.5% in cattle, 7.0% in sheep, and 0.0% in horses. Among cattle, the animals up to 3 years old had significantly lower seroprevalence rate than those in older age groups. Natural foci of tick-borne encephalitis are obviously present in northeastern Hungary. On the other hand, no antibodies neutralizing BHAV were detected in the domestic animals.

Mosquitoborne Viruses, Czech Republic, 2002

Specimens from residents (n = 497) of an area affected by the 2002 flood were examined serologically for mosquitoborne viruses. Antibodies were detected against Tahyna (16%), Sindbis (1%), and Batai (0.2%) viruses, but not West Nile virus. An examination of paired serum samples showed 1 Tahyna bunyavirus (California group) infection.

Mosquito (Diptera: Culicidae) fauna in an area endemic for West Nile virus.

ABSTRACT: Mosquito collections with CDC light traps using dry ice and pigeon-baited traps were carried out in south Moravia (Czech Republic) from April to October in 2007 and 2008 at two study sites. In 2007, 11 two-day captures were carried out in two-week intervals, and 1,490 female mosquitoes of nine species were caught. In 2008, 15 two-day trappings of mosquitoes were carried out: 6,778 females of 22 species of mosquitoes were trapped. The results showed marked differences in abundance and species composition of mosquitoes between both study sites and between the trapping methods. In the floodplain forest ecosystem of the Soutok study area, Aedes vexans predominated. The species composition in the Nesyt study site was more varied and the most common species was Culex pipiens. At the latter study site, Anopheles hyrcanus (var. pseudopictus) and Uranotaenia unguiculata, mosquito species with largely southern Eurasian distribution, were repeatedly demonstrated. The largest capture of mosquitoes was in traps with CO2 placed at a height 1 m above the ground. The capture of mosquitoes in the pigeon-baited traps as well as in the traps with CO2 placed in the canopy of trees was markedly lower in both study sites, with the predominant species being Culex pipiens.

Presence of the mosquito Anopheles hyrcanus in South Moravia,Czech Republic

During a survey of mosquitoes in the South Moravian lowland area, the mosquito Anopheles hyrcanus (Pallas) (Diptera: Culicidae) was found breeding in an ancient fishpond (Nesyt). It is not clear whether this southern Palaearctic species, a known vector of malaria in Asia which has not been recorded in the Czech Republic until this year, has gone undetected in the past or whether it has recently moved into the region as a result of climate change.

Toxoplasma gondii antibodies in house sparrows (Passer domesticus) and tree sparrows (P. montanus)

Synanthropic sparrows in Poland and the Czech Republic were tested for Toxoplasma gondii antibodies by an indirect fluorescent antibody test (titre>/=10). T. gondii antibodies were demonstrated in 12.3% of 227 house sparrows (Passer domesticus) and 4.9% of 41 tree sparrows (Passer montanus).

A simple method of transmission risk assessment in enzootic foci of Lyme borreliosis

The proposed method consists in examining individual host-seeking vector ticks of the Ixodes ricinus complex by microscopy for borreliae and evaluating the proportion of ticks with more than 100 borreliae. The investigations were carried out in a deciduous oak forest habitat in South Moravia, Czech Republic, over four years (1991–1994). In May (i.e., at the peak of seasonal activity of I. ricinus), about 150 nymphal and 200 adult ticks were examined each year. It was found that annual incidence of human Lyme borreliosis in the region correlated better with the proportion of heavily infected ticks than with the overall infection rate of the ticks.