Acute toxicity of oxytetracycline and florfenicol to the microalgae Tetraselmis chuii and to the crustacean Artemia parthenogenetica

Aquaculture systems are a potentially significant source of antibacterial agents to the aquatic environment. The antibacterials oxytetracycline (OTC) and florfenicol (FLO) have been widely used in aquaculture. These pharmaceuticals may cause deleterious effects on wild aquatic organisms accidentally exposed to them. Therefore, the objective of this study was to evaluate the acute toxicity of OTC and FLO to the microalgae Tetraselmis chuii and to the crustacean Artemia parthenogenetica, using culture growth inhibition and death, respectively, as effect criteria. OTC and FLO were found to inhibit the growth of T. chuii cultures, with 96 h IC(50) values of 11.18 and 6.06 mg/L, respectively. OTC 24 and 48 h LC(50) values for A. parthenogenetica were 871 and 806 mg/L, respectively. FLO did not cause mortality of A. parthenogenetica. These results indicate that OTC and FLO are considerably more toxic to T. chui than to A. parthenogenetica. They also indicate that the concentrations required to induce mortality to A. parthenogenetica only in exceptional conditions will occur in the environment.     

The thyroid endocrine disruptor perchlorate affects reproduction, growth, and survival of mosquitofish

The perchlorate anion--an oxidizer found in rockets, missiles, some ammunition, flares, airbags, and fireworks--occurs as a contaminant in ground and surface water in many parts of the United States. Its toxic effects include inhibition of thyroid hormone synthesis. To investigate its chronic toxicity, mosquitofish (Gambusia holbrooki) adults and fry were exposed to aqueous sodium perchlorate at 1, 10, and 100mg/L, and growth and reproductive performance (fecundity, eggs/embryos mass, and gonadosomatic index [GSI]) were determined. Five-day acute toxicity tests were also performed. Perchlorate had a stimulatory effect on fecundity, GSI, and egg/embryo mass, at least for some treatments. The LC50 of sodium perchlorate was 404 mg/L. Growth was enhanced at 1mg/L but inhibited at 10mg/L. These results suggest that, at environmentally relevant concentrations, perchlorate does not induce acutely toxic effects but may have mild stimulatory or hormetic effects on fitness parameters in this species.     

Mixture toxicity of the anti-inflammatory drugs diclofenac, ibuprofen, naproxen, and acetylsalicylic acid

The ecotoxicity of the nonsteroidal anti-inflammatory drugs (NSAIDs) diclofenac, ibuprofen, naproxen, and acetylsalicylic acid (ASA) has been evaluated using acute Daphnia and algal tests. Toxicities were relatively low, with half-maximal effective concentration (EC50) values obtained using Daphnia in the range from 68 to 166 mg L(-1) and from 72 to 626 mg L(-1) in the algal test. Acute effects of these substances seem to be quite improbable. The quantitative structure-activity relationships (QSAR) approach showed that all substances act by nonpolar narcosis; thus, the higher the n-octanol/water partitioning coefficient (log Kow) of the substances, the higher is their toxicity. Mixture toxicity of the compounds could be accurately predicted using the concept of concentration addition. Toxicity of the mixture was considerable, even at concentrations at which the single substances showed no or only very slight effects, with some deviations in the Daphnia test, which could be explained by incompatibility of the very steep dose-response curves and the probit analysis of the data. Because pharmaceuticals in the aquatic environment occur usually as mixtures, an accurate prediction of the mixture toxicity is indispensable for environmental risk assessment.     

Effects of temperature and oxygen concentration in sediment toxicity testing

Joint effects of temperature and oxygen concentrations for the results of sediment toxicity tests were studied at 10 and 20 °C with 40% and 80% dissolved oxygen (DO) saturation. Growth, feeding rate, and reproduction of Lumbriculus variegatus (Oligochaete) and growth, emergence, and survival of Chironomus riparius (Diptera) were tested in a polluted and in a reference sediment. Both the feeding of L. variegatus and the emergence of C. riparius were significantly retarded at low temperature. Additionally, differences in the sex ratio of the emerged adults of C. riparius were observed. The oxygen concentration alone did not have any significant effect on the endpoints, but significant combined effects of polluted sediment and low DO were observed on the biomass of L. variegatus. The standard sediment toxicity tests might offer only limited data for risk assessment of contaminated sediments at sites where the actual conditions largely differ from the laboratory conditions.     

Sensitivity of juvenile freshwater crayfish Cherax destructor (Decapoda: Parastacidae) to trace metals

Juvenile Cherax destructor was investigated as a potential test species for toxicity testing of trace metals in Australian freshwater systems. Adult male and female C. destructor were bred in the laboratory to obtain 4-week old juveniles, which were used in the toxicity tests. Animals were exposed to a range of concentrations of the trace metals ions copper (377-1275 microg/L), cadmium (377-1275 microg/L), nickel (300-1013 mg/L) and iron (36-168 mg/L) in static-renewal 96-h bioassays. The 96-h LC50 value for cadmium was 379, 494 microg/L for copper, 50 mg/L for iron and 327 mg/L for nickel demonstrating a decreasing toxicity of these metals to C. destructor. Comparison of LC50 values for metals for this species with those for other aquatic organisms reveals that C. destructor is less sensitive to trace metals than most other tested species.     

Acute toxicity of 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, and 2,6-dinitrotoluene in the adult bullfrog (Lithobates catesbeiana)

2,4,6-Trinitrotoluene (TNT) is one of the most prevalent high explosives in the environment. 2,4-Dinitrotoluene (2,4-DNT) and 2,6-dinitrotoluene (2,6-DNT) are the most common isoforms of dinitrotoluene. The goal of this study was to determine the acute toxic effects of TNT, 2,4-DNT, and 2,6-DNT in adult male bullfrogs. The LD(50) for TNT was 1,060 mg/kg BW while the LD(50 )for 2,4-DNT and 2,6-DNT was 1,098 mg/kg BW. All three compounds elicited similar symptoms of toxicity including changes of skin color, body weight, development of seizures, liver and kidney necrosis, and lung cyanosis. Relative organ weights did not show significant change.     

Use of the juvenile clam, Mercenaria mercenaria, as a sensitive indicator of aqueous and sediment toxicity

The hard clam is an economically important bivalve and is abundant along the East Coast of the US. The goal of this research was to evaluate the sensitivity of this test species as compared to that of other benthic and epibenthic organisms. Toxic effects of cadmium (inorganic metal), DDT (organochlorine pesticide), and fluoranthene (polycyclic aromatic hydrocarbon) exposure in sediments (10-day) and seawater (24-h) on juvenile (212-350-microm) hard clams Mercenaria mercenaria were determined. The aqueous 24-h LC(50) values were 0.42 mg/L cadmium (95% CL=0.35-0.45 mg/L), 0.61 mg/L DDT (95% CL=0.40-0.95 mg/L), and 0.65 mg/L fluoranthene (95% CL=0.44-1.23 mg/L). Results of sediment toxicity tests indicated that the 10-day LC(50) values were 1.66 mg/kg cadmium (95% CL=1.21-2.28 mg/kg), 5.8 mg/kg DDT (95% CL=4.8-8.3mg/kg), and 1.75 mg/kg fluoranthene (95% CL=1.38-2.09 mg/kg). Based on comparisons to toxicity data for other marine species, these findings suggest that the juvenile clam is one of the more sensitive species to a variety of contaminants and may be a valuable indicator for potential sediment toxicity.     

Contamination levels of lead, cadmium and mercury in imported and domestic lobsters and large crab species consumed in France: Differences between white and brown meat

Lead, cadmium and total mercury contents have been determined by atomic absorption spectrometry in white and brown meat of 108 batches of crustaceans (lobsters, spider crabs, common crabs, swimming crabs and king crabs) collected in France between April and December 2009. With mean levels of 0.041, 0.132 and 0.128 mg kg⁻¹ for Pb, Cd and Hg, respectively, concentrations in white meat were systematically below the European legislation maximum level of 0.50 mg kg⁻¹. Cd concentration in the brown meat of common crabs (mean concentration: 11.8 mg kg⁻¹ and maximum of 14.3 mg kg⁻¹) was well above the observed levels for white meat. The consumption of one whole common crab of 1 kg (about 120 g of white and brown meat) would not contribute significantly to the Pb and Hg provisional tolerable weekly intake (PTWI) for adults, but the ingested Cd would greatly exceed the TWI of 2.5 μg kg⁻¹ body weight, which may be a health issue for consumers of brown meat. Therefore, we recommend moderate brown meat consumption.     

Heavy metal toxicity in Exosphaeroma gigas (Crustacea, Isopoda) from the coastal zone of Beagle Channel

Acute toxicity of copper, cadmium, and zinc on isopod Exosphaeroma gigas was evaluated at 20 per thousand and 30 per thousand salinity. Six concentrations were assayed to estimate effective concentration of the toxicant that affects 50% of tested animal (EC50), while physiological responses and bioaccumulation were determined at 0.42 and 1.95 mg L(-1) of each metal. The following toxicity orders were obtained: Cd>or=Cu>Zn at 20 per thousand salinity and Cu>Zn>or=Cd at 30 per thousand salinity. Copper treatments showed a reduction in oxygen consumption at 30 per thousand salinity, while an opposite trend was observed at 20 per thousand salinity. Zinc caused dissimilar effects, while in cadmium significant reduction was only registered in 0.42(20 per thousand) mg L(-1). Ammonia excretion was generally higher in treatments than control at 20 per thousand salinity. At 30 per thousand salinity, excretion did not change in relation to control or diminished. In general terms, O:N atomic ratios indicated a preponderant protein metabolism. Bioaccumulation of assayed metals was higher at lowest salinity and increased with increasing toxic concentrations.     

Bioaccumulation and toxicity of sediment associated herbicides (ioxynil, pendimethalin, and bentazone) in Lumbriculus variegatus (Oligochaeta) and Chironomus riparius (Insecta)

The benthic macroinvertebrates Lumbriculus variegatus and Chironomus riparius were used in toxicity and bioaccumulation tests to determine the toxic concentrations and accumulation potential of sediment associated herbicides. The tested chemicals were ioxynil, bentazone, and pendimethalin. The bioaccumulation tests with L. variegatus were performed in four different sediments, each having different characteristics. Water-only LC₅₀ tests were performed with both L. variegatus and C. riparius. A sublethal effect of model compounds in sediments was assessed by a C. riparius larvae growth-inhibition test. Of the model compounds, ioxynil appeared to be the most toxic, with LC₅₀ values 1.79 and 2.79 mg L⁻¹ for L. variegatus and C. riparius, respectively. The LC₅₀ water concentrations for bentazone were 79.11 and 62.31 mg L⁻¹ for L. variegatus and C. riparius, respectively. Similarly, ioxynil revealed the highest bioaccumulation potential in bioaccumulation tests. The most important characters affecting chemical fate in the sediment seemed to be the organic matter content and the particle size fraction. The sediments with low organic material and coarse particle size consistently showed high bioaccumulation potential and vice versa. In C. riparius growth tests bentazone had a statistically significant effect on larval growth at sediment concentrations of 1160 and 4650 mg kg⁻¹ (P<0.05). It is noteworthy that standard deviations tend to be greater at high chemical concentrations, which addresses the fact that part of the individuals started to suffer. Ioxynil had an effect on the larval growth in other test sediment at the highest concentration (15.46 mg kg⁻¹ dw), in which head capsule length correlated with larval weight, decreasing toward higher exposure concentrations. The current results show the importance of sediment organic matter as a binding site of xenobiotics.     

The occurrence and sources of Campylobacter spp., Salmonella enterica and Escherichia coli O157:H7 in the Salmon River, British Columbia, Canada

In this study, we wished to assess the prevalence and determine the sources of three zoonotic bacterial pathogens (Salmonella, Campylobacter, and Escherichia coli O157:H7) in the Salmon River watershed in southwestern British Columbia. Surface water, sewage, and animal faecal samples were collected from the watershed. Selective bacterial culture and PCR techniques were used to isolate these three pathogens and indicator bacteria from these samples and characterize them. Campylobacter was the most prevalent pathogen in all samples, followed by Salmonella, and E. coli O157:H7. E. coli O157:H7 and Salmonella isolation rates from water, as well as faecal coliform densities correlated positively with precipitation, while Campylobacter isolation rates correlated negatively with precipitation. Analysis of DNA extracted from water samples for the presence of Bacteroides host-species markers, and comparisons of C. jejuni flaA-RFLP types and Salmonella serovars from faecal and water samples provided evidence that human sewage and specific domestic and wild animal species were sources of these pathogens; however, in most cases the source could not be determined or more than one source was possible. The frequent isolation of these zoonotic pathogens in the Salmon River highlights the risks to human health associated with intentional and unintentional consumption of untreated surface waters.     

Acute respiratory distress syndrome in Plasmodium vivax malaria: case report and review of the literature

Plasmodium vivax infection can cause acute respiratory distress syndrome (ARDS). This complication of P. vivax infection is being increasingly recognised and was life threatening in a traveller returning from Gujarat, India. Nineteen other published cases of P. vivax with respiratory symptoms are also reviewed and confirm that ARDS was the underlying complication in most cases. Plasmodium vivax-associated ARDS is a clinically recognisable condition whose underlying pathophysiology is likely to reflect processes that are independent of parasite sequestration in the pulmonary microvasculature.     

Characterization of fine particulate matter in Ohio: indoor, outdoor, and personal exposures

Ambient, indoor, and personal PM2.5 concentrations were assessed based on an exhaustive study of PM2.5 performed in Ohio from 1999 to 2000. Locations in Columbus, one in an urban corridor and the other in a suburban area were involved. A third rural location in Athens, Ohio, was also established. At all three locations, elementary schools were utilized to determine outdoor, indoor, and personal PM2.5 concentrations for fourth and fifth grade students using filter-based measurements. Three groups of 30 students each were used for personal sampling at each school. Continuous ambient PM2.5 mass concentrations were also measured with tapered element oscillating microbalances (TEOMs). At all three sites, personal and indoor PM2.5 concentrations exceeded outdoor levels. This trend is consistent on all week days and most evident in the spring as compared to fall and winter. The ambient PM2.5 concentrations were similar among the three sites, suggesting the existence of a common regional source influence. At all the three sites, larger variations were found in personal and indoor PM2.5 than ambient levels. The strongest correlations were found between indoor and personal concentrations, indicating that personal PM2.5 exposures were significantly affected by indoor PM2.5 than by ambient PM2.5. This was further confirmed by the indoor to outdoor (I/O) ratios of PM2.5 concentrations, which were greater when school was in session than non-school days when the students were absent.     

Legionella species and serogroups in Malaysian water cooling towers: identification by latex agglutination and PCR-DNA sequencing of isolates

In this study, we investigated the distribution of Legionella species in water cooling towers located in different parts of Malaysia to obtain information that may inform public health policies for the prevention of legionellosis. A total of 20 water samples were collected from 11 cooling towers located in three different states in east, west and south Malaysia. The samples were concentrated by filtration and treated with an acid buffer before plating on to BCYE agar. Legionella viable counts in these samples ranged from 100 to 2,000 CFU ml^-1; 28 isolates from the 24 samples were examined by latex agglutination as well as 16S rRNA and rpoB PCR-DNA sequencing. These isolates were identified as Legionella pneumophila serogroup 1 (35.7%), L. pneumophila serogroup 2–14 (39%), L. pneumophila non-groupable (10.7%), L. busanensis, L. gormanii, L. anisa and L. gresilensis. L. pneumophila was clearly the predominant species at all sampling sites. Repeat sampling from the same cooling tower and testing different colonies from the same water sample showed concurrent colonization by different serogroups and different species of Legionella in some of the cooling towers.     

Molecular pathology, taxonomy and epidemiology of Besnoitia species (Protozoa: Sarcocystidae)

Until recently, besnoitiosis has been a neglected disease of domestic animals. Now, a geographic expansion of the causing protozoan parasite Besnoitia besnoiti in livestock has been recognized and the disease in cattle is considered emerging in Europe. Bovine besnoitiosis leads to significant economic losses by a decline in milk production, sterility, transient or permanent infertility of bulls, skin lesions and increase of mortality in affected cattle population. Phylogenetically, the Besnoitia genus is closest related to the well studied and medically important protozoans, Toxoplasma gondii and Neospora caninum. In contrast, discriminative molecular markers to type and subtype large mammalian Besnoitia species (B. besnoiti, B. caprae, B. tarandi, B. bennetti) on a relevant level of species and strains are lacking. Similarly, these cyst-forming parasites may use two hosts to fulfill their life cycle, but this has not been proven for all large mammalian Besnoitia species yet. Most important though, the final hosts and transmission routes of these Besnoitia species remain mysterious. Here, we review aspects of parasite’s pathology, speciation, phylogeny, epidemiology and transmission with a special focus on recent molecular studies of all to date known Besnoitia species. Using an integrated approach, we have tried to highlight some promising directions for future research.     

Individual and combined effect of anthracene, cadmium, and chloridazone on growth and activity of SOD izoformes in three Scenedesmus species

Short-term (12-48 h) experiments were carried out to examine the effect of anthracene (three-ring aromatic hydrocarbon), cadmium (CdCl(2)), and chloridazone (triazine herbicide), individually and in combination, on growth and SOD activity of three green algae Scenedesmus: S. subspicatus, S. obliquus, and S. microspina, grown in a batch-culture system. The relative toxicity of chemicals to algae was anthracene > chloridazone > cadmium. The species revealed similar growth sensitivity to individual chemicals after 24 h of exposure but there were differences between them when exposed to their combinations. Two methods were used to determine the modes of interaction effects of the chemical combinations; both led to the same results, with two exceptions of all 36 variants examined. In general, mixtures of two and three chemicals behaved toward algal growth mainly in an antagonistic manner (20 cases), whereas additive and synergistic interaction occurred 13 and 3 times, respectively. Antagonism was the most frequently observed to growth of S. obliquus; antagonistic interaction and additive effect was noted in relation to S. subspicatus, while response of S. microspina depended markedly on applied combination. There is a relationship between SOD activity and growth response to stress. The markedly higher level of SOD isoforms activities was noticed in cells (especially S. microspina and S. obliquus) exposed to 12 h to combined chemicals, as compared to individually treated and control cells. SOD activities in cells of three Scenedesmus grown 24 h were similar in all experimental variants and after 48 h of exposure significantly decreased in almost all cases (especially in S. subspicatus). There were no differences observed between SOD profiles obtained for all variants examined. Chloroplasts seems to be the main target site of interaction effects of dissimilarly acting chemicals.     

The isolation of Leishmania tropica and L. aethiopica from Phlebotomus (Paraphlebotomus) species (Diptera: Psychodidae) in the Awash Valley, northeastern Ethiopia

In a survey of Leishmania infections in phlebotomine sandflies in a highly suspected focus of leishmaniasis in the Awash Valley (northeastern Ethiopia) between January 1994 and August 1997, a total of 3307 females of 11 Phlebotomus species (P. orientalis, P. fantalensis, P. saevus, P. sergenti, P. gemetchi, P. alexandri, P. bergeroti, P. duboscqi, P. arabicus, P. martini, and P. rodhaini) were dissected. Promastigotes were detected in 17 females of three species (11 P. saevus, 4 P. sergenti and 2 P. arabicus). Of these, only two P. saevus (one from Upper Awash and one from Middle Awash) and three P. sergenti (from Upper Awash) positives were successfully isolated in culture and were typed by isoenzyme analysis. Four isolates (two each from P. saevus and P. sergenti) were identified as new zymodemes (Z) of L. tropica and one isolate from P. sergenti was typed as a new zymodeme of L. aethiopica. This is the first finding of natural infections of P. saevus and P. arabicus and the first evidence for the former to be a vector of L. tropica. This is also the first time P. sergenti has been implicated in L. tropica transmission in Ethiopia; the isolation of L. aethiopica from a Paraphlebotomus species (P. sergenti) is also a new record. The possible presence of human cutaneous leishmaniasis (L. tropica and L. aethiopica), and wild reservoir host(s) of the parasites, especially rock hyrax (Procavia capensis) in the Upper and Middle Awash Valley remain to be determined.     

Short-Term Effects of Air Pollution on Mortality in the Cities of Rouen and Le Havre,France, 1990–1995

In this study, the authors examined the short-term effects of ambient air pollution on mortality across 2 French cities: Rouen and Le Havre. In Poisson regression models, which controlled for day-of-week effects, the authors used nonparametric smoothing to control for temporal trend, weather, and influenza epidemics. In Rouen, an interquartile range increase of 60.5–94.1 μg/m³ of ozone was associated with an increase of 4.1 % (95% confidence interval = 0.6, 7.8) of total mortality. Daily variations in sulfur dioxide (interquartile range increase = 17.6–36.4 μg/m³) were also associated with an 8.2% increase (95% confidence interval = 0.4, 16.6) in respiratory mortality. An increase of 6.1% (95% confidence interval = 1.5, 10.9) of cardiovascular mortality was also observed with an interquartile range increase of nitrogen dioxide (i.e., 25.3–42.2 μg/m³). With respect to Le Havre, an interquartile range increase in daily levels of sulfur dioxide (11.3–35.6 μg/m³) was associated with an increase of approximately 3% (95% confidence interval = 0.8, 5) of cardiovascular mortality. For particulate matter less than or equal to 13 urn in diameter (interquartile increase = 21.5, 45.4 μg/m³), an increase of 6.2% (95% confidence interval = 0.1,12.8) was observed. The estimates of pollutant effects and their standard deviations were slightly affected by the degree of smoothing temporal variations in this study. When low collinearity was present, the 2-pollutant models provided acceptable estimates of pollutant effects. They suggested that the ozone effect was independent of the Black Smoke effect, and that the effects of sulfur dioxide and nitrogen dioxide were unlikely to be confounded by ozone concentrations. However, high collinearity leads to large estimates of the pollutant coefficient variances and, therefore, leads to inaccurate estimates of pollutant effects. The analysis of the contributory effects of different pollutant mixtures requires further investigation in those instances in which high collinearity between pollutants is present.     

Correlation between Levels of Vitamins D3 and E in Type 2 Diabetes Mellitus: A Case-Control Study in Serdang,Selangor, Malaysia

An overview of vitamins D₃ and E suggests micronutrient deficiency contributes to type 2 diabetes mellitus (T2DM). A case-control study was conducted to determine the status of plasma vitamins D₃ and E isomers amongst diabetic Malaysians. Two groups were recruited for participation, one comprising fifty diabetic subjects (DM) and one comprising fifty non-diabetic (non-DM) subjects, in order to assess their plasma vitamin D₃, calcium and vitamin E status. Glycaemic status (haemoglobin A1c, HbA1c; fasting blood glucose, FBG; C-Peptide) and lipid profiles (total cholesterol, TC; triglycerides, TG; low-density lipoprotein-cholesterol, LDL-C; high-density lipoprotein-cholesterol, HDL-C) were assessed, followed by anthropometric measurements. The Mann–Whitney U-test, Kruskal–Wallis and Spearman’s correlation coefficient were used to elucidate the association between levels of plasma vitamins D₃ and E and T2DM. The vitamin D₃ deficiency group (<20 ng/mL) showed a significant correlation (p < 0.05) with glycaemic status (HbA1c and FBG) and lipid profiles (HDL-C, LDL and TC). Spearman’s correlation demonstrated that vitamin D₃ status is strongly correlated with HDL levels (p < 0.05). Similarly, plasma total vitamin E levels >4.9 μg/mL revealed significantly different FBG, HbA1c, C-Peptide, LDL, HDL and TC levels across both groups. Moreover, family history, smoking, waist circumference and HbA1c levels demonstrated a significant association (p < 0.05) with levels of vitamins D and E but not FBG and lipid profiles. This could be because the pre-diabetic status among the non-DM group influenced the outcomes of this study.     

Hospital infestation by the cluster fly, Pollenia rudis sensu stricto Fabricius 1794 (Diptera: Calliphoridae), and its possible role in transmission of bacterial pathogens in Germany

The potential of the cluster fly, Pollenia rudis sensu stricto, to transmit bacterial pathogens was investigated during a mass infestation that took place in a German hospital. Cluster flies were individually examined for mesophilic bacteria carried on the exoskeleton. Bacterial growth could only be detected by using the enrichment culture technique to increase sensitivity, but not by direct intoculation of fly samples to agar plates. All 50 cluster fly samples that were tested carried opportunistic aerobic mesophilic Bacillus spp., whereas 41 fly samples were positive for Erwinia spp., 16 samples for Erwinia amylovara, 24 samples for Stenotrophomonas maltophilia, and 4 samples for Flavobacterium odoratum. Staphylococcus lugdunensis and Pseudomonas aeruginosa were found in 5 samples. No bacteriologically sterile cluster fly samples were obtained. The whole bacterial pattern found on P. rudis s. s. is known for its potential to cause opportunistic and/or nosocomial infections in humans. The results obtained led to the assumption that mass infestations of cluster flies occurring in sensitive areas, especially in hospitals, may cause a low, but not neglectable health threat due to mechanical transmission of bacterial pathogens.