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PubMed1999

Chronic symptoms in construction workers treated for musculoskeletal injuries.

BACKGROUND: Soft tissue musculoskeletal injuries make up a high proportion of all work-related injuries in construction. Data from Workers' Compensation claims indicate that strains and sprains are the leading compensable injury for construction workers. This study describes the consequences of soft tissue musculoskeletal injuries for construction workers, and assesses the persistence of symptoms after an injury and the impact of that injury on return to work. METHODS: Through an Emergency Department surveillance system [Hunting et al., 1994a], we recorded 176 construction worker visits, from 5/01/93 through 2/28/95, for strains, sprains, joint injury or pain, tendinitis, dislocations, hernias, or other musculoskeletal injuries excluding fractures. Telephone interviews were conducted several months after workers had visited the emergency room for a musculoskeletal injury. RESULTS: Seventy individuals were interviewed about the long-term impacts of 72 incidents that had resulted in work-related musculoskeletal injuries. For 46 (62%) of the 74 diagnoses, problems continued beyond two months. The likelihood of problems continuing more than two months varied considerably by body location of injury. Hispanic workers and older workers were more likely to have continuing symptoms. Eleven of the 45 construction workers with symptoms persisting longer than two months were not employed at the time of the interview. Only 11 of the 45 workers with ongoing symptoms told us that modifications had been made to their jobs to accommodate their symptoms. About one-quarter of these 45 subjects reported substantial effects on home or work life. CONCLUSIONS: Acute musculoskeletal injuries in construction workers frequently result in chronic symptoms, and those with chronic symptoms report substantial effects of the injury on their quality of life. Job accommodations were made in a minority of these injuries. These findings point to the need for heightened efforts for injury prevention in this industry.

Absenteeism↗
PubMed2000

Occupational disability related to back pain: application of a theoretical model of work disability using prospective cohorts of manual workers.

BACKGROUND: A new model of work disability was developed based on the assumption that four different groups of workers are present at the beginning of a prospective epidemiologic study: one group of workers without back pain, and three groups of workers with back pain and a gradient of work disability. The goal of this research was to verify if these groups comprise workers at different levels of risk of occurrence of complete work disability related to back injury. METHODS: Prospective cohorts of manual workers (n=578) were followed for 1 year to document the risk of occurrence of complete disability related to back injury. RESULTS: The results showed that the workers who presented with back pain without work disability at the beginning of the study were at less risk compared to all the other workers in the cohort. Moreover, an effect modification was found between the workers who initially presented with back pain without work disability and a past history of compensation for back injury, adding credence to the non-similarity of these workers to the others. CONCLUSIONS: Based on these results, further studies should focus on improving the knowledge of the characteristics of these workers leading to a better understanding of how to prevent occupational low-back pain.

Adult↗
PubMed1989

Lead exposure among lead-acid battery workers in Jamaica.

To assess lead exposure in the Jamaican lead-acid battery industry, we surveyed three battery manufacturers (including 46 production workers) and 10 battery repair shops (including 23 battery repair workers). Engineering controls and respiratory protection were judged to be inadequate at battery manufacturers and battery repair shops. At manufacturers, 38 of 42 air samples for lead exceeded a work-shift time-weighted average concentration of 0.050 mg/m3 (range 0.030-5.3 mg/m3), and nine samples exceeded 0.50 mg/m3. Only one of seven air samples at repair shops exceeded 0.050 mg/m3 (range 0.003-0.066 mg/m3). Repair shop workers, however, had higher blood lead levels than manufacturing workers (65% vs. 28% with blood lead levels above 60 micrograms/dl, respectively). Manufacturing workers had a higher prevalence of safe hygienic practices and a recent interval of minimal production had occurred at one of the battery manufacturers. Workers with blood lead levels above 60 micrograms/dl tended to have higher prevalences of most symptoms of lead toxicity than did workers with lower blood lead levels, but this finding was not consistent or statistically significant. The relationship between zinc protoporphyrin concentrations and increasing blood lead concentrations was consistent with that described among workers in developed countries. The high risk of lead toxicity among Jamaican battery workers is consistent with studies of battery workers in other developing countries.

Adult↗
PubMed1994

A survey of actinic keratoses among paraquat production workers and a nonexposed friend reference group.

Follow-up on two reports of an excess of keratoses among paraquat production workers was conducted to evaluate the contribution of occupational exposures to the prevalence of keratoses among workers in a paraquat production plant in Texas. A cross-sectional study design was used to compare the prevalence of keratoses among current workers to an age, race, and sex frequency-matched group of their friends who had never worked at the plant. The analysis is based on 112 workers and 232 friends. Exposure, outcome, and covariables used in the analyses were obtained from an interview questionnaire, dermatology exam, and company records. Overall, the prevalence proportion of the presence of any actinic keratoses among workers and friends was similar (0.30 and 0.28, respectively). Among high cumulative exposed workers, the prevalence of any actinic keratoses was 0.40 compared to 0.20 among low-exposed workers and 0.28 among friends. These results were further explored using a multiple logistic regression approach to adjust for known risk and possibly confounding variables. Statistically significant high risks of actinic keratoses were demonstrated for freckling before age 16 years, older age, suntanning behaviors, occupational exposure to polycyclic aromatic hydrocarbons (PAH), and Fitzpatrick skin type. There was no significant contribution of overall exposure status (worker vs. friend). Similar to the crude analysis, the odds of actinic keratoses of high-exposed workers compared to friends was 1.9 (confidence interval [CI] = 0.9-4.2) whereas the comparable odds ratio for low-exposed workers vs. friends was 0.6 (CI = 0.2-1.7). These data do not demonstrate an excess of actinic keratoses overall nor any consistent increase in the odds of keratoses with an increase in plant exposure level.

Adult↗
PubMed1995

Respiratory symptoms and lung function in wool textile workers.

Our study investigated a group of 216 wool textile workers (158 women and 58 men). Respiratory symptoms were assessed by questionnaire in wool textile workers and in 130 not exposed (control) workers. Ventilatory capacity was measured in wool workers by recording maximum expiratory flow-volume (MEFV) curves on Monday before and after the work shift. Forced vital capacity (FVC), 1-second forced expiratory volume (FEV1), and flow rates at 50% and the last 25% of the vital capacity (FEF50, FEF25) were measured on the MEFV curves. Analysis of the data demonstrated a significantly higher prevalence of all chronic respiratory symptoms in wool workers than in controls, being the highest in wool workers for nasal catarrh (M: 63.8%; F: 44.9%) and for sinusitis (M: 62.1%; F: 43.0%). A high prevalence of acute symptoms, associated with the work shift, was also noted in wool workers. Exposure to wool dust caused significant across-shift reductions of ventilatory capacity varying from 1.4% for FEV1 to 9.1% for FEF50. Textile workers exposed to wool for > 10 years in the workplace had similar across-shift reductions of ventilatory capacity tests as those with shorter exposures. In a large number of these wool workers, FEF50 and FEF25 were below 70% of predicted normal values. Smokers had acute and chronic lung function changes similar to those of nonsmokers, indicating that smoking did not account for all the respiratory effects seen in wool processing workers. Our data suggest that dust exposures in wool textile mills may be associated with the development of chronic respiratory symptoms and impaired lung function.

Adult↗
PubMed1991

Identification of vitellogenin in the ant, Camponotus festinatus: changes in hemolymph proteins and fat body development in workers.

Vitellogenin has been identified in the ant Camponotus festinatus, both in queens and workers. In the workers, it is already present before adult eclosion in low concentrations (less than 1 microgram/microliter hemolymph). Vitellogenin and vitellin are immunologically identical and are composed of a single type of apoprotein with an apparent Mr = 185,000. The molecular weight of the native molecules was estimated as approximately 460,000 by pore limiting gradient electrophoresis. Vitellogenin was detected as a major protein in the hemolymph of young workers, both under queenright and queenless conditions. Thus, in spite of their sterility in the presence of the queen, C. festinatus workers are able to synthetize vitellogenin which is identical both in size and immunologically to the queen vitellogenin. About 6-7 weeks after adult eclosion, however, vitellogenin was usually undetectable in the hemolymph of queenright workers, particularly the minor workers, while it constituted about 30% of total protein in queenless workers. Protein concentration in the hemolymph of queenless insects increased up to 20-fold as compared to 1-day-old insects. Queenless workers also developed large amounts of perivisceral fat body, while queenright workers, particularly the minor workers, showed a dramatic fat body regression about 6 weeks after emergence.

Animals↗
PubMed2005

Pain exacerbation as a major source of lost productive time in US workers with arthritis.

OBJECTIVE: To estimate the prevalence of arthritis and arthritis pain exacerbations in US workers including impact on functioning and lost productive work time (LPT). METHODS: The research was conducted as a nested case-control study of participants in the Caremark American Productivity Audit, a US national random-digit-dial survey of US workers. The sample included 329 workers ages 40-65 years meeting the First National Health and Nutrition Examination Survey criteria for arthritis, and 91 workers not meeting arthritis inclusion criteria. Participants completed a telephone interview to measure the prevalence of arthritis and pain exacerbations, LPT (in hours and dollars), functional disability using the Western Ontario and McMaster Universities Knee and Hip Osteoarthritis Index (WOMAC) and the Australian/Canadian Osteoarthritis Hand Index, and demographics. RESULTS: The prevalence of arthritis in US workers ages 40-65 years was 14.7% during the 2-week period. Pain exacerbation occurred among 38% of participants with arthritis. Workers with pain exacerbations were significantly more likely to have higher WOMAC scores (38.6 versus 29.6; P = 0.0041) and report arthritis-related LPT (24.4% versus 13.3%; P = 0.0118) than workers without exacerbations. Among those with LPT, average LPT did not differ (4.1 hours per week) between persons with and without exacerbations. The estimated annual LPT cost from arthritis in the US workforce was $7.11 billion, with 65.7% of this cost attributed to the 38% of workers with pain exacerbations. CONCLUSION: Workers with arthritis pain exacerbation account for a disproportionate share of the arthritis-related LPT cost. Stratifying workers for appropriate treatment management based on pain exacerbation status could significantly decrease arthritis-related LPT and offer employees and employers an effective return on health care use.

Absenteeism↗
PubMed1990

Biological monitoring of workers exposed to lead stearate.

This study was conducted to examine the usefulness of some of the commonly used biological parameters for monitoring of workers exposed to lead stearate. Forty-two lead stearate workers from a lead stabilizer factory and 26 workers exposed to inorganic lead compounds were involved in this study. Although the workers had similar blood lead values (PbB), subjects exposed to lead stearate were found to have a significantly higher concentration of lead in plasma (PbP), 1.0 +/- 0.57 micrograms dl-1) than workers exposed to inorganic lead compounds (0.42 +/- 0.3). The ratio of PbP to PbB was ca. 2.5 times higher for lead stearate workers (0.38) than the inorganic lead workers (0.15). These data suggest that the different chemical properties of lead stearate may result in different distributional patterns of the metal in different blood components. On the other hand, the activity of delta-aminolevulinic acid dehydratase (ALAD), an enzyme highly sensitive to lead, was not so much depressed among the lead stearate workers as that of workers handling inorganic lead. A poor correlation was also observed between PbB and ALAD activity of the stearate workers. These findings indicate that PbB and ALAD are not good biological indicators for evaluating the toxicological effect of lead stearate exposure.

Chemical Industry↗
PubMed1997

Worker reproduction and social hierarchies in Leptothorax ants

Kin selection theory predicts the existence of potential conflict between queen and workers and among workers concerning the production of males in insect societies with a single, once-mated queen. We investigated the occurrence of reproductive conflict and worker reproduction in both single- and multi-queen colonies of 10 species of the ant genus LeptothoraxIn contrast to previous observations in related species, workers only infrequently engaged in aggressive interactions and did not lay large numbers of eggs in colonies containing queens. Allozyme analyses of queens, workers and males suggest that the contribution of workers to the males produced in colonies with queens is indeed minimal, at least in L. unifasciatusWhen the queens died or were experimentally removed from the colonies, in most species dominance interactions among workers became significantly more frequent and one or several high-ranking workers started to lay eggs. Workers with an increased number of ovarioles per ovary apparently had a reproductive advantage over workers with normal ovaries.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour

Journal Article↗
PubMed2000

Division of labour and seasonality in the ant Leptothorax albipennis: worker corpulence and its influence on behaviour.

We address the organization of workers in social insect societies. We distinguish between changes in behavioural role over the nurse to forager role sequence, which may depend on changes in physiology, and potentially more rapid changes of task within role. We investigated the association between role and nutrient status in the ant Leptothorax albipennis. Worker lipid stores were quantified using a new body size-controlled method, and were related to worker behaviour. Worker lipid stores were evenly distributed amongst colony members at the end of winter, splitting rapidly into two distinct modes (replete nurses and lean foragers) in spring. The proportion of lean foragers increased throughout spring and summer, until most colonies contained only workers of this type. Callow workers then eclosed with intermediate lipid stores. We developed a computer vision system that tracks all nest ants to extract detailed behaviour of individuals of known lipid stores. Lipid storage was negatively correlated with a worker's foraging propensity, and with measures of spatial occupation in the nest and of activity. Different colonies showed a similar quantitative correlation between lipid stores and behavioural role, suggesting that lipid stores were not only correlated with the relative organization of individuals within each nest, but may also have influenced their absolute role. We reviewed the literature and found evidence that nutrient status influences role predisposition in social insect workers. We conclude that the distribution of worker roles may be linked to the balance between foraging income and energetic consumption within the colony directly via worker nutrient status. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1997

Seroimmunological characteristics of Korean workers exposed to toluene diisocyanate.

Since type I allergy caused by specific IgE antibodies may play principal roles and IgG antibody-mediated reactions have been thought to be involved in some parts of the pathogenesis, this study was performed to investigate the role of IgE- or IgG-mediated hypersensitivity reactions in development of toluene diisocyanate (TDI) asthma in Korean workers. For 81 TDI spray painters, self-administrative questionnaires and direct interviews on respiratory symptoms, chest auscultation, and measurements of forced vital capacity (FVC) and forced expiratory volume in 1 sec (FEV1.0) were performed. The TDI concentration in their working environments was measured. Levels of serum IgE and IgG specific to TDI were estimated by radioallergosorbent test (RAST) and ELISA using p-tolyl isocyanate-human serum albumin (TMI-HSA) as the antigen. When sputum, cough, and dyspnea aggravated by work or wheezing existed, when FVC or FEV1.0 was less than 80% of the normal reference value, or when IgE RAST for TDI was positive, the peak expiratory flow rate (PEFR) was recorded four times per day for over 2 weeks. If decrease of PEFR was over 20% of baseline PEFR and changing pattern of PEFR was closely related to workshift in time, then a diagnosis of TDI asthma was made. Changing patterns of PEFR of 8 (9.9%) workers corresponded to the diagnostic criteria of TDI-related occupational asthma. Levels of the specific IgE were increased in 9 (11.1%) of the 81 subject workers and in 3 (37.5%) of the 8 PEFR-positive workers. Levels of the specific IgG were increased in 9 (11.1%) workers, and in only 1 (12.5%) of the asthmatics sensitive to TDI. Neither elevated TDI-specific IgE levels nor PEFR test positivities were associated with increased IgG levels. The mean titer of the PEFR-test-positive workers was slightly lower than that of the PEFR-negative workers and that of the IgE RAST-positive workers lower than that of the test-negative workers, but there was no statistical significance. These results suggest that IgG is not deeply involved in the pathogenesis of TDI-induced occupational asthma in Korean workers.

Adult↗
PubMed1997

Multiple myeloma and benzene exposure in a multinational cohort of more than 250,000 petroleum workers.

Case reports have suggested an association between benzene exposure and multiple myeloma. Because petroleum workers are exposed to benzene or benzene-containing liquids, studies of these workers provide an opportunity for investigating the relationship between benzene and multiple myeloma. A large number of cohort studies of petroleum workers have been conducted. However, few of them have reported results of multiple myeloma separately. One reason is that multiple myeloma is usually grouped with other lymphopoietic cancers in the analysis. Another reason is that multiple myeloma is relatively rare, and few individual studies are large enough to provide reliable risk estimates. To determine the risk of multiple myeloma in petroleum (refinery, distribution, production, and pipeline) workers, we have identified 22 cohort mortality studies of petroleum workers in the United States, the United Kingdom, Canada, and Australia. Authors of these studies were contacted, and data on the number of observed deaths and age-specific person-years of observation were requested. Data from individual studies were combined in a pooled analysis (meta-analysis). In addition to the pooled analyses, results for individual cohorts, most of which have never been reported before, are also presented. The combined multinational cohort consisted of more than 250,000 petroleum workers, and the observation period covered an interval of 55 years from 1937 to 1991. A total of 205 deaths from multiple myeloma were observed, compared to 220.93 expected, a total derived from respective national mortality rates. The corresponding standardized mortality ratio (SMR) was 0.93 and the 95% confidence interval (95% CI) was 0.81-1.07. Additional analyses were performed by type of facility and industrial process. Stratum-specific SMRs (95% CIs) were 0.92 (0.77-1.09) for refinery workers and 0.93 (0.69-1.23) for distribution workers. When individual cohorts were stratified by length of observation, no pattern was detected. The pooled analysis indicates that petroleum workers are not at an increased risk of multiple myeloma as a result of their exposure to benzene, benzene-containing liquids, or other petroleum products in their work environment. This conclusion is supported by cohort studies of workers in other industries who were exposed to benzene as well as by population-based case-control studies of multiple myeloma and occupational exposures.

Australia↗
PubMed1994

Respiratory symptoms and immunological status in poultry food processing workers.

A group of 57 female workers employed in the processing of poultry food and 51 nonexposed control workers were studied to determine the possible relation between respiratory and immunological findings in poultry food workers. The prevalences of all chronic respiratory symptoms were significantly higher in exposed than in control workers (P < 0.01) except for occupational asthma. The highest prevalence of chronic respiratory symptoms in exposed workers was found for chronic cough (49.1%), followed by dyspnea (43.9%), rhinitis (38.6%), chronic phlegm (31.6%), and chronic bronchitis (26.3%). Occupational asthma was found in 5.3% of exposed workers. Exposed workers with a positive skin prick test to poultry food extract demonstrated higher prevalences of all chronic respiratory symptoms than those with negative skin tests, although the difference was statistically significant only for rhinitis (P < 0.05). The most frequent skin reactions were found for poultry food extract (exposed: 66.7%; control: 25.5%; P < 0.05). An increased IgE serum level was found in 19 (33.3%) of the exposed and in four (7.8%) of the control workers (P < 0.01). Three exposed workers with occupational asthma demonstrated an increased serum IgE level. Our data confirm previous results indicating that occupational exposure to poultry food dust may be associated with the development of chronic respiratory symptoms and immunological changes in exposed workers.

Adult↗
PubMed1992

Four-year follow-up of effects of toluene diisocyanate exposure on the respiratory system in polyurethane foam manufacturing workers. II. Four-year changes in the effects on the respiratory system.

Fifty-seven polyurethane foam manufacturing workers (PF workers) and 24 reference workers were followed for 4 years to clarify the effects on pulmonary function of working in PF factories with exposure to toluene diisocyanate (TDI). No significant differences in the average annual losses (AALs) of pulmonary function for 4 years were observed among the 28PF workers whose TDI exposure levels were very low (mean = 0.1 ppb, group L), the remaining 29 PF workers with mean TDI exposure of 5.7 ppb (group H), and the reference workers. However, 15 PF workers in group H who had experienced peak exposure excursions to 30 ppb or above with a mean concentration of 8.2 ppb showed significantly larger AALs in percentage maximal mid-expiratory flow, forced expiratory volume in 1 s ratio to vital capacity (FVC), and forced expiratory flow at 25% of FVC than expected, and significantly larger AALs in some obstructive pulmonary function indices than those of the 14 remaining PF workers in group H whose peak exposure excursion levels were 3-14 ppb with a mean time-weighted average (TWA) of 1.7 ppb, group L, and the reference workers. These findings suggest that the peak exposure excursion level of TDI might be important in inducing obstructive pulmonary function changes in the PF workers rather than the TWA exposure levels, though further comparative studies of the AAL in those who are exposed to different peak exposure excursion levels but the same mean exposure levels are necessary. From the standpoint of prevention, the proposition that peak exposure excursion levels exceeding 20 ppb should be avoided is reasonable.

Adult↗
PubMed1994

Capacity for vasodilatation in the forearms of manual and office workers.

The aim of the present study was to investigate whether occupational physical work using the arms would have a local training effect on the capacity for vasodilatation in the forearm. The subjects were 13 installation workers, and 13 office workers, who were similar in age, height, and body mass. The installation workers were exposed to heavy manual tasks during most of their workshift, whereas the office workers did no heavy manual exercise. The index of forearm capacity for vasodilatation was the plethysmograph flow response after 10 min of arterial occlusion (240 mmHg, 32 kPa). Systolic and diastolic blood pressure, and skin red cell flux (laser-Doppler) were determined together with the blood flow. In both groups, the dominant arm had significantly higher circumference and volume compared to the nondominant arm, whereas handgrip strength was similar for both the arms. The manual workers had greater volumes in both arms in comparison to the office workers, but handgrip strength did not differ between groups. In both groups, the peak forearm vascular conductance was higher in the dominant arm compared to the nondominant arm. In both forearms, the manual workers exhibited significantly higher peak blood flow, and peak vascular conductance than the office workers. No significant difference in skin blood flow was seen between the groups or arms. In conclusion, the forearms of the manual workers had a greater capacity for vasodilatation compared to the office workers suggesting a local vascular training effect due to frequent exposure to heavy physical work using hands.

Adult↗
PubMed1993

Measurements of year-long exposure to tree nursery workers using multiple pesticides.

A year-long nurseryworker pesticide exposure study was designed to measure and evaluate the exposure occurring to workers who had the potential for simultaneous exposure to multiple pesticides. This four-State study was conducted in five nurseries (four USDA Forest Service and one State) involved in conifer seedling production. Primary comparisons were made among nursery workers in the Pacific northwest and south central United States. Worker exposure was assessed by using patches attached to clothing, handrinse samples and urine excreted from potentially exposed workers. In addition, dislodgeable residue in rinsate from a water wash of pesticide-treated seedlings was also evaluated. Four different groups of field workers, designated as applicators, weeders, scouts and packers, were included. The pesticide absorbed dose, assessed by urine analysis of pesticide metabolites and the deposition of pesticide on patches attached to the clothing of field workers, was monitored as they performed their duties under normal conditions (e.g., typical clothing, pesticide application). Monitoring was performed for the 14 different pesticides which were used in these nurseries. Seven pesticides were studied in more detail using biological monitoring. For these compounds, metabolites known to be excreted in the urine of exposed humans or other mammals were used to estimate the dose of pesticide absorbed by the exposed workers. The highest percentage of positive samples came from dislodgeable residue samples (8.3%) followed by patch samples (3.2%), handrinse (2.9%), and urine samples (1.3%). To summarize the conclusions from the urinary excretion data, 12 of the 73 nursery workers in the study received a low absorbed dose of pesticide. Biological monitoring revealed that three pesticides (benomyl, bifenox and carbaryl) were found in the urine of some of the workers. Of the 3,134 urine samples analyzed there were 42 positive; 11 urine samples were positive for benomyl, while bifenox was responsible for 13 positives and carbaryl accounted for the remaining 18. The 12-week continuous monitoring of urine showed that metabolites of these materials were rapidly excreted; thus, no build-up in the body is anticipated. Margins of Safety (MOS) calculations were made to provide an assessment of the significance of the exposure. Based on the low frequency of positive urine samples in the study, the low levels of metabolites when they were found, their apparent rapid excretion rate and the No Observed Effect Level (NOEL) data, furnished from other sources, nursery worker exposure to pesticides in these conifer nurseries is below health threatening levels.

Adult↗
PubMed2003

Size-correlated division of labour and spatial distribution of workers in the driver ant, Dorylus molestus.

Driver ants ( Dorylus spp.) show a high degree of worker polymorphism. Previous reports suggest that large Dorylus workers are specialised for defensive tasks. In this study, we first quantitatively tested whether there is a size-correlated division of defensive labour among workers. Second, we determined whether the spatial distribution of workers outside the nest can be predicted based on such size-specific differences in task allocation. We show that the division of defensive behaviour among different-sized workers is not strict. However, there is a significant correlation between worker size and the tendency to carry out defensive tasks. First, workers of larger size were more likely than smaller workers to participate in colony defence. Second, larger workers were more frequent near the nest containing the reproducing individuals and the brood. Finally, large workers were more common in open sections of the trail than in covered sections, which are likely to be less exposed to predators.

Animals↗
PubMed2003

Lethal fighting between honeybee queens and parasitic workers (Apis mellifera).

Pheromonal signals associated with queen and worker policing prevent worker reproduction and have been identified as important factors for establishing harmony in the honeybee (Apis mellifera) colony. However, "anarchic workers", which can evade both mechanisms, have been detected at low frequency in several honeybee populations. Worker bees of the Cape honeybee, Apis mellifera capensis, also show this anarchistic trait but to an extreme degree. They can develop into so called "pseudoqueens", which release a pheromonal bouquet very similar to that of queens. They prime and release very similar reactions in sterile workers to those of true queens (e.g. suppress ovary activation; release retinue behavior). Here we show in an experimental bioassay that lethal fights between these parasitic workers and the queen (similar to queen-queen fights) occur, resulting in the death of either queen or worker. Although it is usually the queen that attacks the parasitic workers and kills many of them, in a few cases the workers succeeded in killing the queen. If this also occurs in a parasitized colony where the queen encounters many parasitic workers, she may eventually be killed in one of the repeated fights she engages in.

Aggression↗