Seasonal changes in the larval populations of Aedes aegypti in two biotopes in Dar es Salaam, Tanzania

The seasonal dynamics of larval populations of Aedes aegypti was studied in two different biotopes in Dar es Salaam, Tanzania. The first biotope was located on the Msasani peninsula on the coast 6 km north of Dar es Salaam, where A. aegypti breeds exclusively in coral rock holes. The population dynamics was studied during both the rainy and the dry season. Seasonal changes in the density of A. aegypti larvae depend primarily on variation in rainfall. The population of larvae dropped to zero only for a short time during the driest period while the adult population was maintained at a low level. The second biotope was in an automobile dump in a Dar es Salaam suburb, where A. aegypti breeds in artificial containers such as tires, automobile parts, tins, coconut shells, and snail shells. The greater part of the A. aegypti population of this biotope is maintained in the egg stage during the dry season. It serves as a focal point for breeding during the dry season: with the coming of the rains, the population expands into the surrounding residential areas. More than 70% of the larval population developed in tires, 20% in tins, 5% in coconut shells, and 1% in snail shells.     

Presence of Chlorinated Paraffins in Sediments from the North and Baltic Seas

Chloroparaffins (CPs) were determined in sediments collected from the North and Baltic Seas during monitoring campaigns in 2001–2003. Electron ionization tandem mass spectrometry (MS/MS) was used for a first screening. It allowed the simultaneous determination of short (SCCP) and medium chain chlorinated paraffins (MCCP). SCCP+MCCP concentrations between 5 and 499 ng/g dry weight were found. In general, Baltic Sea sediments were more highly contaminated by CPs than the North Sea was. However, concentrations related to the total organic carbon content were on the same order of magnitude due to the higher organic content in the Baltic Sea. Additional information about the congener and homologue pattern was obtained for selected samples from the Baltic Sea by high-resolution gas chromatography combined with negative ion chemical ionization and low-resolution mass spectrometry, Concentrations in the North Sea were in general too low for this approach. In the Baltic Sea, MCCP concentrations were 1.7–2.4 times higher than for SCCPs. Lower chlorinated C₁₃ and C₁₄ compounds were the main CP compounds. The CP congener and homologue patterns showed similarities with technical SCCP and MCCP mixtures when compared using principal component analysis.     

Discovery of a new gene pool and a high genetic diversity of the chestnut blight fungus Cryphonectria parasitica in Caucasian Georgia

In this study, we investigated the population genetic structure and possible origins of the plant pathogen Cryphonectria parasitica in Caucasian Georgia, a region within the centre of origin of the host species Castanea sativa. A total of 427 C. parasitica isolates from nine populations were genotyped at 10 microsatellite loci. A high genetic diversity was detected, but the overall Georgian population was dominated by three haplotypes which were present in most individual populations. Two of them have not been previously found in Europe. Bayesian clustering analysis and principal component analysis could not identify their source population, neither in Asia nor in North America. On the other hand, one haplotype is frequent in Central Europe and probably naturally invaded Caucasian Georgia from neighbouring Turkey. Seventy-three haplotypes were unique to specific populations, and 66 of them were represented by a single isolate. Allele patterns suggest that most of these haplotypes emerged locally through sexual recombination between haplotypes of the Georgian and the central European gene pool. Due to the high incidence of haplotypes not otherwise present in Europe, Caucasian Georgia represents an additional source of diversity for the European C. parasitica population.     

Composition of protozoan communities at two sites in the coastal zone of the southern Baltic Sea

Protozoan communities were studied in the coastal zone of the southern Baltic Sea. Stable environmental conditions and typical, bimodal seasonal changes in the protozoan biomass were observed at the sampling site in Sopot (2003–2004). At the sampling site in Ustka (2007–2008), strong benthic resuspension and irregular impacts of fresh water resulted in atypical seasonal changes in the protozoan biomass with a summer peak only. The mean annual biomass had similar values at both sites: 43.2 μg C dm^?3 in Sopot and 38.6 μg C dm^?3 in Ustka. The protozoan community in Sopot was dominated by ciliates (48% of the biomass), whereas in Ustka — by heterotrophic nanoflagellates (53%).     

Polychlorinated biphenyl concentrations in cod-liver oil: Evidence of a steady-state condition of these compounds in the Baltic area oils and levels noted in Atlantic oils

A steady-state condition of polychlorinated biphenyl (PCB) pollution is evident in cod-liver oil samples of fish collected from the Baltic area between 1971 and 1989. Spatial differences in the concentration of congeners and isomers of these chemicals between the Baltic Sea and other areas in the north and northeastern part of the Atlantic Ocean appeared to be rather small. A site relatively distant from the PCB sources of the European continent, an open ocean environment near Iceland, showed a fivefold lower concentration of many PCB congeners than the Baltic Sea. The open and deep waters of the North Sea and Norwegian Sea differed by a factor of 2 in the total concentrations of PCBs when compared with the southern Baltic proper. Continuous release of PCBs into the atmosphere over Europe, its drift from distant sources in North America, and further aerial transport and deposition due to dominating air masses movement from the west and southwest are postulated to be the main routes of PCBs pollution and a reason for the small differences in concentration between the marine areas assessed.     

A foreign invader or a reclusive native? DNA bar coding reveals a distinct European lineage of the zoonotic parasite Schistosoma turkestanicum (syn. Orientobilharzia turkestanicum ())

Natural foci of Schistosoma turkestanicum (syn. Orientobilharzia turkestanicum) has been identified in the Gemenc Forest regions of Hungary utilising red deer as the definitive host. In order to identify the origins of this parasite in Europe standard DNA bar coding techniques were employed to sequence fragments of the cytochrome oxidase 1 (cox1) and the nuclear ribosomal internal transcribed region (ITS) from 10 individual adult male worms. Phylogenetic reconstruction using maximum likelihood phylogenetic reconstruction and haplotype networks of the cox1 showed all the worms to be of a distinct unique Hungarian lineage although some ITS haplotypes were shared with worms from populations in China and Iran. Molecular clock analysis suggests an early divergence event around 270,000 years before present (YBP) between all S. turkestanicum populations giving rise to the Chinese, Iranian and Hungarian lineages. However, divergence of the sequences within the Hungarian population appears to have occurred approximately 63,000 YBP suggesting a long established population of S. turkestanicum in Europe. This suggests that the Hungarian population of S. turkestanicum has been native since the Ice Age and probably established itself during the last interglacial period as red deer moved into Europe from North Africa and the Middle East. This may also indicate that the parasite may have unknown populations established in several other countries in Eastern, Central and Southern Europe.     

Indoors illumination and seasonal changes in mood and behavior are associated with the health-related quality of life

Objective  

Seasonal changes in mood and behavior are common in a general population, being of relevance to public health. We wanted to analyze whether the HRQoL is associated with the seasonal changes in mood and behavior. Because the shortage of exposure to daylight or artificial bright light has been linked to the occurrence of the seasonal changes, we wanted to know whether illumination indoors contributes to the HRQoL.     

Microsatellite markers reveal two genetic groups in European populations of the carrot cyst nematode Heterodera carotae

The cyst nematode Heterodera carotae, which parasitizes carrot roots, has been recorded in many countries in Europe (Italy, The Netherlands, Switzerland, France, Denmark, …), in South Africa and in North America (Canada, USA). To date, there is a lack of knowledge about the genetic structure of the populations of this economically important nematode. The aim of this work was to study the structuration of the genetic diversity of the carrot cyst nematode at the European scale. We have developed a set of thirteen polymorphic microsatellite markers and used it to genotype seventeen European populations of H. carotae coming from France, Switzerland, Italy, Denmark and one non-European population from Canada. As previously showed for other cyst nematode species, the H. carotae populations were characterised by a strong heterozygote deficit. A Bayesian clustering analysis revealed two distinct genetic clusters, with one group located in the north of Europe and a second one located in the south of Europe. Moreover, our results highlighted rather limited gene flow at small spatial scale and some events of long distance migration. This first investigation of the genetic diversity of H. carotae populations would be useful to develop sustainable control strategies.     

Genetic diversity of Leishmania donovani/infantum complex in China through microsatellite analysis

The Leishmania strains from different epidemic areas in China were assessed for their genetic relationship. Twenty-nine strains of Leishmania infantum isolated from 1950 to 2001 were subjected to multilocus microsatellite typing (MLMT) using 14 highly polymorphic microsatellite markers. Twenty-two MLMT profiles were recognized among the 29 L. infantum strains, which differed from one another in 13 loci. Bayesian model-based and distance-based analysis of the data inferred two main populations in China. Sixteen strains belonged to one population, which also comprised previously characterized strains of L. infantum non-MON1 and Leishmania donovani. The parasites within this population are assignable to a distinct cluster that is clearly separable from the populations of L. donovani elsewhere, i.e. India, Sri Lanka and East Africa, and L. infantum non-MON1 from Europe. The remaining 13 Chinese strains grouped together with strains of L. infantum MON1 into another population, but formed a separate cluster which genetically differs from the populations of L. infantum MON1 from Europe, the Middle East, Central Asia and North Africa. The existence of distinct groups of L. infantum MON1 and non-MON1/L. donovani suggests that the extant parasites in China may have been restricted there, but not recently introduced from elsewhere.     

Modeling of egg production by Temora longicornis from the southern Baltic Sea including salinity

The paper presents modeling of egg production (Egg — no. of eggs female^?1 d^?1) by Temora longicornis in the changing environmental conditions of the southern Baltic Sea (Gdańsk Deep). It is hypothesized that the food-saturated rate of egg matter production is equivalent to the specific growth rate of copepods. Based on the findings from the south-western Baltic Sea, Egg of T. longicornis is evaluated as a function of food concentration, temperature and salinity over a wide range of these parameters. Subsequently, the rate of reproduction during the seasons in the Gulf of Gdańsk is determined. According to our calculations, values of Egg reach ca 11 eggs per day in April and decline strongly in June-July, while the second smaller peak in reproduction occurs in September, ca 8 eggs per day. Our results suggest that egg production rates of T. longicornis depend not only on food concentration and temperature, but also on salinity, which is a masking factor in the Baltic Sea.     

Seasonal breeding drives the incidence of a chronic bacterial infection in a free-living herbivore population

Understanding seasonal changes in age-related incidence of infections can be revealing for disentangling how host heterogeneities affect transmission and how to control the spread of infections between social groups. Seasonal forcing has been well documented in human childhood diseases but the mechanisms responsible for age-related transmission in free-living and socially structured animal populations are still poorly known. Here we studied the seasonal dynamics of Bordetella bronchiseptica in a free-living rabbit population over 5 years and discuss the possible mechanisms of infection. This bacterium has been isolated in livestock and wildlife where it causes respiratory infections that rapidly spread between individuals and persist as subclinical infections. Sera were collected from rabbits sampled monthly and examined using an ELISA. Findings revealed that B. bronchiseptica circulates in the rabbit population with annual prevalence ranging between 88% and 97%. Both seroprevalence and antibody optical density index exhibited 1-year cycles, indicating that disease outbreaks were seasonal and suggesting that long-lasting antibody protection was transient. Intra-annual dynamics showed a strong seasonal signature associated with the recruitment of naive offspring during the breeding period. Infection appeared to be mainly driven by mother-to-litter contacts rather than by interactions with other members of the community. By age 2 months, 65% of the kittens were seropositive.     

Contaminant-related suppression of delayed-type hypersensitivity and antibody responses in harbor seals fed herring from the Baltic Sea.

Recent mass mortalities among several marine mammal populations have led to speculation about increased susceptibility to viral infections as a result of contaminant-induced immunosuppression. In a 2.5-year study, we fed herring from either the relatively uncontaminated Atlantic Ocean or the contaminated Baltic Sea to two groups of captive harbor seals and monitored immune function in the seals. Seals fed the contaminated fish were less able to mount a specific immunological response to ovalbumin, as measured by in vivo delayed-type hypersensitivity (DTH) reactions and antibody responses. The skin reaction to this protein antigen was characterized by the appearance of mononuclear cells which peaked at 24 hr after intradermal administration, characteristic of DTH reactions in other animals studied. These DTH responses correlated well with in vitro tests of T-lymphocyte function, implicating this cell type in the reaction. Aryl-hydrocarbon (Ah) receptor-dependent toxic equivalent (TEQ) profiles in blubber biopsies taken from the seals implicated polychlorinated biphenyls rather than dioxins or furans in the observed immunosuppression. Marine mammal populations currently inhabiting polluted coastal environments in Europe and North America may therefore have an increased susceptibility to infections, and pollution may have played a role in recent virus-induced mass mortalities.     

Chaetoceros resting spores as indicators of Holocene paleoenvironmental changes in the Gulf of Gdańsk, southern Baltic Sea

The aim of this study was to analyze resting spores of Chaetoceros spp. preserved in Middle and Late Holocene sediments of the three parts of the Gulf of Gdańsk, southern Baltic Sea. The material studied consists of ten cores retrieved from Ku?nica Deep (Puck Lagoon), as well as the shallower and deeper parts of the Outer Puck Bay region. Our results indicate that the abundance of Chaetoceros resting spores in diatom taphocoenoses corresponded to regional and local paleoecological changes registered in Mastogloia, Littorina and Post-Littorina sediments, and that they also reflect human impact in the last hundred years.     

The biology of Biomphalaria choanomphala and B. sudanica in relation to their role in the transmission of Schistosoma mansoni in Lake Victoria at Mwanza, Tanzania

A study of the intermediate snail hosts of Schistosoma mansoni in Lake Victoria at Mwanza, Tanzania, was begun in October 1969, the main aims being to investigate the distribution and seasonal variations in population densities of Biomphalaria choanomphala and B. sudanica in relation to the nature of the lake bottom and the biological features of the lake shore, the factors influencing variations in the intensity of S. mansoni transmission along the Mwanza shoreline, and the age structure of populations of B. choanomphala. Field surveys were made at 70 sites near Mwanza and in nearby bays, B. choanomphala being collected from the lake bottom by means of a wire-mesh dredge. Variations in the distribution and population density of B. choanomphala were correlated with the nature of the bottom and its depth profiles at depths of 0.5-6.0 m. Approximately 1-20 snails/m² were found on mixed sand and mud but only about 1 snail/m² on the predominantly muddy bottom farther out from the shore. Seasonal variations in the age structure and fluctuations in the population densities of B. choanomphala of as much as 10-13-fold were observed. A large and a small form of B. choanomphala, possibly ecophenotypes, were found. S. mansoni infection rates in B. choanomphala ranged from 0.2% to 3.3%, suggesting a tendency to higher infection rates in mature snails.     

Nematodes found in the European anchovy (Engraulis encrasicolus), a rare visitor to the Baltic Sea

The European anchovy, Engraulis encrasicolus (Linnaeus, 1758), enters the Baltic Sea only occasionally. Little is known about the parasites that inhabit this fish in the northern part of its natural range (north-eastern Atlantic). This study is based on 32 anchovies sampled in autumn 2006 from a substantial bycatch accompanying sprat in the Gulf of Gda??sk (southern Baltic Sea). The fish were examined using standard parasitological procedures, and yielded 10 L3 larvae of the nematode Hysterothylacium aduncum (Rudolphi, 1802). The prevalence and the intensity (mean and range) were 21.9%, 1.4, and 1?C4, respectively.     

No evidence for congenital malformations or prenatal death in infants born to women with a high dietary intake of fish contaminated with persistent organochlorines

Objectives: The aim of the present study was to assess whether a high dietary intake of fatty fish from the Baltic Sea, contaminated with persistent organochlorine compounds, might increase the risk for congenital malformations and perinatal death. Methods: A cohort of fishermen's wives from the Swedish east coast (at the Baltic Sea) were linked to the Swedish Medical Birth Register (MBR), resulting in the identification of 1501 infants born in the period 1973–1991. A further linkage with the Swedish Registry of Congenital Malformations was performed. Similar linkages were made for a comparison group of fishermen's wives from the Swedish west coast, who gave birth to 3553 infants during the study period. The reproductive end points studied included congenital malformations, stillbirths, and early neonatal deaths. The expected numbers of these end points were calculated from the MBR data for the regional populations. Results: In the east coast cohort, 3.3% of the infants had some malformation diagnosis as compared with 5.0% of the west coast cohort. As compared with the general population, somewhat fewer malformations than expected were diagnosed in the east coast cohort (risk ratio 0.78, 95% CI 0.58–1.04). No specific malformation was overrepresented in the east coast cohort. The risk ratios for stillbirths and early neonatal deaths did not significantly differ from unity in any of the cohorts. Conclusions: The present results exclude in an unequivocal way an association between exposure to persistent organochlorines from fatty Baltic Sea fish and an increased risk for all congenital malformations and perinatal death. The limited power of the study design, however, does not allow the exclusion of slight risk excesses for some specific types of malformation. Received: 28 May 1998 / Accepted: 22 October 1998     

Tick-borne diseases under the radar in the North Sea Region

The impact of tick-borne diseases caused by pathogens such as Anaplasma phagocytophilum, Neoehrlichia mikurensis, Borrelia miyamotoi, Rickettsia helvetica and Babesia species on public health is largely unknown.Data on the prevalence of these pathogens in Ixodes ricinus ticks from seven countries within the North Sea Region in Europe as well as the types and availability of diagnostic tests and the main clinical features of their corresponding diseases is reported and discussed. Raised awareness is needed to discover cases of these under-recognized types of tick-borne disease, which should provide valuable insights into these diseases and their clinical significance.     

Seasonality and the requirements for perpetuation and eradication of viruses in populations.

Perpetuation of a virus in a population is distinct from the ability to persist in a cell culture or individual host. Parameters which determine perpetuation include: 1) the size of the population; 2) the turnover of the population; 3) the proportion of immunes in the population; 4) the transmissibility of the infection; and 5) the generation time between sequential infections. These parameters may be grouped into two composite factors which most directly affect transmission dynamics and perpetuation: (a) population turnover per generation period, and (b) transmissibility or the fraction of susceptibles infected per existing infection. Perpetuation in small populations usually requires either the ability to persist in individuals or rapid population turnover. Conversely, human viruses which initiate only acute infections require larger populations to persist. Seasonal variation in transmissibility can greatly increase the minimum population size in which persistence is possible, and we argue that the population size of 500,000 for measles persistence (described by Bartlett) is primarily a consequence of seasonal variation. Computer modelling can be used to examine the effect of changes in parameters which determine the seasonal cycle of virus perpetuation and fadeout. Finally, human infections are reviewed to indicate those which have been eradicated (smallpox), are on the threshold of eradication (poliomyelitis), are possibly eradicable (measles), or could be candidates for future efforts (hepatitis A and hepatitis B). In developing a strategy for eradication two points are of great potential utility: first, the seasonal trough should be exploited as a time for effective intervention; and, second, containment efforts should be directed at epidemiologically important population groupings such as schools.     

Occupational Exposure to N,N-Dimethylformamide in the Summer and Winter

We evaluated total body burden of N,N-dimethylformamide (DMF) taken through the lung and skin by personal exposure of workers to DMF and urinalysis of N-methylformamide (NMF) and N-acetyl-S(N-methylcarbamoyl)-cysteine (AMCC). A total of 270 workers were engaged in four different jobs in a workplace distant from main production lines emanating high levels of DMF. They were not required to wear any personal protective equipment including respirators or gloves. We found that log-transformed urinary levels of NMF and AMCC increased with an increase in log-transformed concentrations of exposure to DMF. Urinary levels of NMF and AMCC were significantly higher in the summer than the winter, although there was no significant seasonal difference in the concentrations of exposure to DMF. Our findings suggested that the increased urinary levels of NMF and AMCC in the summer resulted in increased skin absorption of DMF due to an increased amount of DMF absorbed by the moisturized skin under humid and hot conditions. Seasonal changes in the relative internal exposure index confirmed the present finding of enhanced summertime skin absorption of DMF. AMCC is thought to be a useful biomarker for assessments of cumulative exposure to DMF over a workweek and for evaluations of workers’ health effects.