Chronic blepharitis due to Demodex: A prospective study in Sfax (Tunisia).

INTRODUCTION: Chronic blepharitis is a common cause of eye irritation and dryness. They are often treated without regard to causal factors such as parasites which are rarely mentioned. AIM: To describe the role of Demodex in the pathogenesis of chronic blepharitis, to analyze the epidemiological, clinical, diagnostic and therapeutic particularities. METHODS: This is a prospective, case-control study conducted in the mycology parasitology department at the Habib Bourguiba university hospital in Sfax covering 100 cases with chronic blepharitis and 87 control cases. Clinical examination and eyelash removal were performed with direct examination for qualitative and quantitative analysis, before and after treatment. RESULTS: Demodex was significantly more found in patients than in controls (48% vs 13.8%). The quantitative analysis showed a significant difference between the two groups with 52.1% of Demodex (+++) for patients versus 8.3% for controls. Demodex blepharitis were treated with yellow oxid mercure ophthalmic ointment with a good outcome in 81,3%. CONCLUSION: Although it is admitted to be a saprophyte of the skin, a large number of arguments argues for the incrimination of Demodex in the etiopathogenesis of chronic blepharitis, hence the interest of eyelashes examination and a parasitic research in front of any chronic blepharitis resistant to usual treatments. In case of positive research, a specific treatment should be prescribed. Its effectiveness is another argument for the etiological diagnosis.

Characteristics of bacterial community in eyelashes of patients with Demodex blepharitis.

BACKGROUND: Demodex blepharitis (DB) is a common disease of the ocular surface. The characteristics of the bacterial community in eyelash roots after Demodex infestation are still unknown. Knowledge of the characteristics of the bacterial community of eyelash follicles in patients with DB can provide valuable insights for guiding the diagnosis and treatment of DB. METHODS: Twenty-five patients with DB (DB group) and 21 non-DB volunteers (control group) were enrolled in the study. Eyelashes from the upper eyelid of the right eye were sampled, and 16S ribosomal DNA (rDNA) sequencing was performed to determine the V3-V4 regions of the microbial 16S rDNA gene within 1 month of infestation. The sequencing data of the two groups were analyzed and compared. The effect of the bacterium Burkholderia on the survival of Demodex mites was evaluated using Demodex obtained from 12 patients with DB other that the patients in the DB group. RESULTS: A total of 31 phyla and 862 genera were identified in the DB and control groups. The five most abundant phyla in the two groups were Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes and Cyanobacteria. The abundance of Actinomycetes was significantly higher in the DB group than in the control group. At the genus level, the five most abundant genera in the two groups were Pseudomonas, Burkholderia-Caballeronia-Paraburkholderia, Rolstonia and Acinetobacter; Clostridium sensu stricto 1 was abundant in the control group and Corynebacterium_1 was abundant in the DB group. Compared with the control group, the abundance of Burkholderia-Caballeronia-Paraburkholderia was 2.36-fold lower in the DB group. Linear discriminant analysis Effect Size (LEfSe) analysis revealed Burkholderia-Caballeronia-Paraburkholderia, SC_I_84_unclassified, Nonmyxobacteria and Succinvibrio to be the major biomarkers in the control group and Catenibacterium and Lachnospiraceae NK4A136 group to be the major biomarkers in the DB group. To explore the performance of these optimal marker models, receiver operational characteristic curve analysis was performed, and the average area under the curve value of Burkholderia-Caballeronia-Paraburkholderia was 0.7448. Burkholderia cepacia isolated from normal human eyelashes was fermented, and the Demodex mites isolated from patient eyelashes were cultured together with its fermented supernatant. The results showed that the fermentation supernatant could significantly reduce the survival time of the Demodex mites, suggesting the potential therapeutic value of this bacterium against Demodex. CONCLUSIONS: The composition of the bacterial community in the eyelashes of DB patients differed from that in eyelashes of healthy volunteers, revealing a decrease in bacterial diversity in infested eyelashes. This decrease may be related to the occurrence and development of DB. The supernatant of Burkholderia cepacia culture medium was found to inhibit the growth of Demodex in eyelash hair follicles, providing a new insight with potential applications for the clinical treatment of Demodex infestation.

The effect of phototherapy on Demodex density: a case-control study.

BACKGROUND: Human Demodex mites, Demodex folliculorum and Demodex brevis, are microorganisms that reside in the pilosebaceous units, usually without causing symptoms. Phototherapy has been linked to demodicosis in previous studies. We aimed to determine whether there was an increase in the frequency of demodicosis and Demodex density after 20 phototherapy sessions. METHODS: A case-control study was conducted with 32 participants who received narrowband ultraviolet B or ultraviolet A-1 therapy for various dermatological indications. Standardized skin surface biopsies were performed before and after phototherapy to assess Demodex density. The presence of Demodex-related skin conditions was assessed before phototherapy. A statistical analysis was performed to compare the Demodex densities and prevalence of demodicosis between the baseline and 20th session of phototherapy. RESULTS: No significant change was observed in Demodex density after 20 sessions of phototherapy. The average Demodex density before treatment was 2.75 ± 4.48 (/cm2 ), and after treatment, it was 2.85 ± 4.81 (/cm2 ), indicating no significant difference (P = 0.879). The percentage of patients with demodicosis in at least one region of the face was 28.1% (9/32) before treatment, and after treatment, it was 31.3% (10/32), with no significant difference (P = 1.00). CONCLUSIONS: Our findings contradict previous studies that suggested an increased Demodex density and demodicosis prevalence after phototherapy. The data from previous studies are open to debate due to their selected samples, designs, and interpretations regarding the phototherapy-immunosuppression-Demodex relationship. Larger-scale longitudinal studies conducted on a homogeneous sample are warranted to better understand the relationship between phototherapy and demodicosis.

Correlation between Demodex species in primary and recurrent chalazia.

OBJECTIVE: To determine the correlation between the infestation by species of Demodex spp. and the occurrence of primary and recurrent chalazia. METHODS: Prospective and observational study. Patients with primary or recurrent chalazia were included. Eyelash samples were taken to determine the microscopic presence of Demodex spp. The correlation between the recurrence of the chalazia and the infestation by Demodex spp. mites was determined using Spearman's rank correlation coefficient test. RESULTS: Sixty-eight adult patients diagnosed with chalazia were included. In 63.2% of the total cases, the presence of one or more parasites of the genus Demodex spp. was documented. In the quantitative parasitological study, it was found that 25% of all cases presented infestation by Demodex spp. defined by an index greater than or equal to 0.5 parasites per eyelash. The most frequently found species was Demodex folliculorum. Of the 14 patients with recurrent chalazia, 50% presented infestation by Demodex spp. and in 91.7% of the cases the infestation was by D. folliculorum. There is a positive, directly proportional correlation between these factors (rθ=+0.665, P<.05). In the group of patients with primary chalazion, only 18.5% presented infestation by Demodex spp., and in 81.6% of these cases it was caused by D. folliculorum. There is a non-statistically significant correlation between these two factors. CONCLUSION: There is a direct, high and statistically significant correlation between the recurrence of the chalazion and the infestation by Demodex spp., there is no statistically significant correlation between the primary chalazia and the presence of Demodex spp.

Comorbidity of Ocular and Facial Demodicosis.

PURPOSE: To determine the association between ocular and facial demodicosis, and the effect of facial treatment on ocular demodicosis. DESIGN: Prospective clinical cohort study. METHODS: Ocular demodicosis outpatients from a tertiary medical center were enrolled from April to December 2020. The diagnosis was based on epilation of 4 eyelashes from each upper eyelid. High ocular Demodex load (ODL) was defined as ≥8 mites per eye. Facial infestation was assessed by direct microscopic examination, with facial Demodex overgrowth (FDO) defined as a density >5 mites/cm2. All patients were prescribed 3 months of ocular treatment, and FDO patients received dermatologic treatment. RESULTS: Eighty-nine patients were enrolled. Among those that completed the treatment course, 39 presented high ODL. Lower cylindrical sleeve counts were found in low ODL patients (low ODL vs high ODL: 8 vs 14, P = .009). FDO was less prevalent in this group (49% vs 77%, P = .012). The Ocular Surface Disease Index score decreased in patients without FDO (20.0 ± 17.1 to 14.0 ± 16.6, P = .027) after 3 months of topical tea tree oil treatment. Topical ivermectin treatment on the facial skin provided a higher ocular Demodex eradication rate in FDO patients (76% vs 16%, P < .001). CONCLUSION: Concurrence of ocular and facial demodicosis is common, especially in cases of severe ocular demodicosis. Although ocular treatment alone is effective for patients with ocular demodicosis only, cotreatment with topical ivermectin on the facial skin enhances ocular Demodex eradication in patients with comorbid facial Demodex overgrowth.

Treatment of sheep prior to movement: its contribution to an effective scab (psoroptic mange) management strategy.

BACKGROUND: Ovine psoroptic mange (sheep scab) is an important disease of sheep worldwide caused by the parasitic mite, Psoroptes ovis. It has a negative impact on animal welfare and leads to significant economic losses for the sheep industry. Effective and targeted management is required to limit its transmission. METHODS: A stochastic metapopulation model of sheep scab transmission is used to investigate the contribution of the treatment of sheep prior to movements to sales, gatherings (predominantly markets) and away grazing to the reduction of prevalence of farms with scab in Great Britain. RESULTS: Treatment prior to movement to gatherings resulted in an 86% reduction in the overall prevalence of farms with scab and was more effective at reducing the overall prevalence of farms with scab than treatment before other categories of movements. The relative risk of farms having scab infection was inversely related to the percentage of farms which treated, but this relationship was not linear, with the biggest declines in the prevalence of farms with scab being achieved by small percentages of farms treating; a 50% relative reduction in the farm prevalence was achieved with only 15% of farms treating prior to gathering movements. CONCLUSIONS: The results suggest that pre-movement treatment of sheep could make an important contribution to national scab control and, in practice, the approach could be more highly targeted if used in conjunction with known geographic and management risk factors for scab.

The varied influence of ocular Demodex infestation on dry eye disease and meibomian gland dysfunction across different age groups.

This study aimed to investigate the impact of ocular demodicosis on dry eye disease (DED) and meibomian gland dysfunction (MGD) across different age populations: young (20 to < 40), middle-aged (40 to < 60), and elderly (≥ 60), based on the retrospective medical chart review. In each age subgroup, Demodex infestation and its count were correlated with clinical parameters of DED and MGD. Among the total of 351 subjects, 52.7% had ocular demodicosis, with a mean of 2.31 ± 1.39 mites per four eyelashes (0.58 per lash) in a unilateral eye. In the age subgroup 1 (age < 40; N = 44), subjects with Demodex had significantly higher meibum quality grades. In subgroup 2 (40 ≤ age < 60; N = 122), subjects with Demodex had higher ocular surface disease index scores and higher MG expressibility grades. However, in subgroup 3 (age ≥ 60; N = 185), demographics and all parameters did not differ according to Demodex infestation. Moreover, the number of mites did not correlate with MGD severity in any of the subgroups. In conclusion, age may act as a significant confounding factor in the relationship between ocular Demodex infestation and clinical features of DED and MGD, despite older patients aged 60 years and above being at a higher risk of Demodex infestation and experiencing more severe MGD.

Prevalence of chigger mites and Orientia tsutsugamushi strains in northern regions of Gangwon-do, Korea.

The present study aimed to survey the prevalence of chigger mites and Orientia tsutsugamushi (O. tsutsugamushi) infection in the northern regions of Gangwon-do, Korea. From early February to early June 2015, a total of 17,050 chiggers were collected from striped field mice, Apodemus agrarius, in Cheorwon-gun, Hwacheon-gun, Yanggu-gun, and Goseong-gun, which are well-known endemic areas of scrub typhus in Korea. The chiggers were analyzed using molecular genomic methods, as previously described. Among the 7,964 identified chiggers, the predominant species was Leptotrombidium pallidum (76.9%), followed by L. zetum (16.4%), L. orientale (4.3%), L. palpale (0.3%), L. tectum (0.2%), and Neotrombicula tamiyai (1.8%). The chigger index (CI) was highest in Hwacheon (115.58), followed by Cheorwon (97.02), Yanggu (76.88), and Goseong (54.68). Out of the 79 O. tsutsugamushi-positive chigger pools, 67 (84.8%) were identified as the Boryong strain, 10 (12.7%) as the Youngworl strain, and only 2 were the Jecheon strain. Based on the high infestation of chiggers in striped field rodents and the high rate of O. tsutsugamushi infection in chigger mites, Hwacheon-gun and Cheorwon-gun are presumed to be high-risk areas for scrub typhus. Furthermore, L. pallidum, a major vector of scrub typhus, and the dominant O. tsutsugamushi serotype, the Boryong strain, were found in the northern regions of Gangwon-do, Korea.

Analyzing Gut Microbial Community in Varroa destructor-Infested Western Honeybee (Apis mellifera).

The western honeybee Apis mellifera L., a vital crop pollinator and producer of honey and royal jelly, faces numerous threats including diseases, chemicals, and mite infestations, causing widespread concern. While extensive research has explored the link between gut microbiota and their hosts. However, the impact of Varroa destructor infestation remains understudied. In this study, we employed massive parallel amplicon sequencing assays to examine the diversity and structure of gut microbial communities in adult bee groups, comparing healthy (NG) and Varroa-infested (VG) samples. Additionally, we analyzed Varroa-infested hives to assess the whole body of larvae. Our results indicated a notable prevalence of the genus Bombella in larvae and the genera Gillamella, unidentified Lactobacillaceae, and Snodgrassella in adult bees. However, no statistically significant difference was observed between NG and VG. Furthermore, our PICRUSt analysis demonstrated distinct KEGG classification patterns between larval and adult bee groups, with larvae displaying a higher abundance of genes involved in cofactor and vitamin production. Notably, despite the complex nature of the honeybee bacterial community, methanogens were found to be present in low abundance in the honeybee microbiota.

Is Demodex Blepharitis Connected With Cataract Surgery?

PURPOSE: To determine whether there is an increased incidence of Demodex of the eyelashes among patients after cataract extraction surgery. DESIGN: Prospective, noncomparative clinical study. METHODS: A cohort of patients who underwent cataract extraction surgery had several eyelashes removed preoperatively that were examined independently by the hospital laboratory for the presence of the Demodex mite. This was repeated 3 weeks after surgery. During several postoperative weeks, patients received the standard treatment of steroid drops alone for a period as individually required. RESULTS: A total of 62 patients were included in the study (31 men and 31 women), with a mean age of 71.04 years (range, 47-87). In the group positive for Demodex, the male-to-female ratio was 2:3 (P = .2772). Demodex colonization was observed in 22.58% of samples before cataract surgery and in 32.26% after cataract surgery and topical postoperative steroid therapy (P = .0143). CONCLUSIONS: There is a statistically significant increase in Demodex colonization of eyelashes after cataract surgery and postoperative topical steroid treatment. Although Demodex colonization does not necessarily cause blepharitis, our findings of increased colonization should raise the possibility of Demodex blepharitis being considered by ophthalmologists in patients with chronic postoperative eye discomfort after cataract surgery. This study was carried out at the Emek Medical Center.

An unusual outbreak of dermatitis due to rodent mite infestation in an acute-care hospital.

We report an outbreak of dermatitis associated with Ornithonysus bacoti and Liponyssoides sanguineus infestation in an acute ambulatory care setting. Healthcare workers developed dermatitis prior to the identification of the outbreak. A collaborative team effort resulted in complete eradication.

Demodex prevalence in mine, textile and food factory workers with dermatosis: a cross-sectional, multicenter study.

Demodex, a type of mite, lives in human hair follicles. They can multiply very quickly in some conditions and then start to irritate the skin by causing skin disorders. This study aims to investigate if working environment conditions affect the prevalence of Demodex. A cross-sectional, multicenter study was conducted with three different occupational groups: mine, textile and food factory workers (n = 102). Determined industry workers who applied to our outpatient dermatology clinics with the complaint of dermatosis in three different cities were included in the study. Demodex positivity was checked by dermoscopy. Differences between categorical variables examined with Chi-square analysis and T test was used to compare continuous variables between groups. 50% Demodex positivity was found in mine workers, 45.3% in food factory workers and 66.7% in textile manufacturing workers. A high rate of Demodex positivity was observed in all three occupational groups. Although the highest positivity rate was observed in textile manufacturing workers, no significant difference was found between the groups (p = 0.320). The overall prevalence of Demodex in female workers was statistically significantly higher than in male workers (p = 0.029). Exposure of workers to a wide variety of factors in work environments such as textile factories and the fact that women are more sensitive to external factors may have caused the prevalence of Demodex to be higher in these groups. So, a change in the work environment or the use of suitable protective equipment may benefit the treatment of diseases caused by Demodex. But, further studies are needed with larger and various industry groups to make more certain views.

High Prevalence of Demodex Infestation is Associated With Poor Blood Glucose Control in Type 2 Diabetes Mellitus: A Cross-Sectional Study in the Guangzhou Diabetic Eye Study.

PURPOSE: The aim of this study was to investigate the association between type 2 diabetes mellitus (T2DM) and ocular Demodex mite infection. METHOD: About 381 patients with T2DM from nearby communities were enrolled, and 163 age-matched and sex-matched nondiabetic patients from the cataract clinic were included as the control group. All subjects underwent personal history and demographic data collection, ocular examination, and lash sampling, followed by microscopic identification and counting of Demodex mites. Binocular fundus photography was performed for diabetic patients. Statistical correlation between ocular Demodex infestation and T2DM and blood glucose control status was performed. RESULTS: The Demodex mite infestation rate (62.5% vs. 44.8%, P < 0.001) and count [3 (0-12) vs. 2 (0-9.6), P = 0.01], especially of Demodex brevis (18.9% vs. 4.9%, P < 0.001) [0 (0-1) vs. 0 (0-0), P < 0.001], were significantly higher in the T2DM patient group than that in the control group. The ratio of Demodex brevis to Demodex folliculorum in the T2DM patient group was significantly higher than that in the control group (1:3 vs. 1:9, P < 0.001). Diabetic patients presented with more cylindrical dandruff (55.1% vs. 39.3%, P = 0.001). Ocular Demodex infestation was strongly associated with poor blood glucose control (HbA 1 c > 7%) (odds ratio = 1.82; 95% confidence interval, 1.12-2.94; P = 0.2) and female sex (odds ratio = 1.69, 95% confidence interval, 1.08-2.65, P = 0.02). No association was found between Demodex infestation and the severity of diabetic retinopathy. CONCLUSIONS: Patients with T2DM, especially those with poor blood glucose control, tend to have a higher prevalence of ocular Demodex infestation, suggesting that high blood glucose is a risk factor for demodicosis .

Infestation of Oriental House Rat (Rattus tanezumi) with Chigger Mites Varies along Environmental Gradients across Five Provincial Regions of Southwest China.

Chigger mites are the exclusive vector of scrub typhus. Based on field investigations of 91 survey sites in 5 provincial regions of Southwest China, this paper reported variations of chigger infestation on the oriental house rat (Rattus tanezumi) along various environmental gradients. A total of 149 chigger species were identified from 2919 R. tanezumi in the 5 provincial regions, and Leptotrombidium deliense (a major vector of scrub typhus in China) was the first dominant chigger species, followed by Ascoschoengastia indica and Walchia ewingi. Rattus tanezumi had a stable overall prevalence (PM = 21.10%), mean abundance (MA = 7.01), and mean intensity (MI = 33.20) of chiggers with the same dominant mites in the whole Southwest China in comparison with a previous report in Yunnan Province, but chigger infestations on R. tanezumi varied along different environmental gradients. Rattus tanezumi in mountainous landscape had a higher infestation load of chiggers with higher species diversity than in flatland landscape. The infestation was higher at lower altitudes and latitudes. A high intensity of vegetation coverage was associated with high infestations. The results reflect the environmental heterogeneity of chiggers on the same host species. Warm climate and high relative humidity are beneficial to chigger infestation on R. tanezumi.

Mange: Epidemiology and ivermectin efficacy in goats and application of zero-inflated negative binomial regression in Uba Debre Tsehay, southern Ethiopia.

Mites are one of the most common and widely distributed ectoparasites of goats in Ethiopia, contributing to major burdens in livestock productivity in the country. Between February 2021 and July 2021, this study was conducted to estimate the prevalence of mange mites, assess the potential risk factors, identify the species infesting goats, and evaluate the efficacy of ivermectin in naturally infested goats in the Uba Debere Tsehay district of Gofa Zone, Southern Ethiopia. A cross-sectional study, longitudinal field efficacy, and questionnaire survey were conducted. A total of 384 goats suspected of having mange were scraped for mite prevalence and count. The mite count data were analyzed using zero-inflated negative binomial (ZINB) models with explanatory variables. The ZINB models indicated that a substantial proportion of the observed zero mite count reflected a failure to detect mites in suspected goats, meaning that the estimated true prevalence was much higher than the apparent prevalence as calculated using a simple proportion of nonzero mite counts. Overall prevalence of mange was 21.87% (84/384) in the study areas. Sarcoptes species (21.09%) and Demodex species (0.78%) were the mite genera identified in this study. Among goats with poor, medium, and good body conditions, mite prevalence was 36.3%, 12.3%, and 10.9%, respectively. Both the prevalence and intensity of infestation were significantly associated with body condition scores, but other risk factors were not. The questionnaire survey indicated that 85.94% of the participants preferred to use modern treatment options (ivermectin 1%, injection) and 76.56% (98/128) respondents replied that ivermectin treatment is effective. Wilcoxon rank-sum test analysis shows that there was significantly (P < 0.05) fewer mites counted on goats treated with ivermectin than on untreated goats at each count up to day 56 after treatment. No live mites were found on any treated animal on days 28 and 56. Mixed ANOVA indicated that there was a significant difference within treatment groups. This study showed that mites are one of the constraints to goat production in the study area and ivermectin was highly effective against Demodex and Sarcoptes mites in goats. Hence, there is a need to create awareness about the impact of mange on goat production, and appropriate ivermectin treatment against mites should be implemented.

Analysis of Demodex infection rate and risk factors in patients with meibomian gland dysfunction.

PURPOSE: In the present study, we aimed to investigate the positive rate of Demodex infection in patients with meibomian gland dysfunction (MGD) and to analyze its risk factors. METHODS: A total of 178 MGD patients admitted to the Jinan Second People's Hospital from April 2020 to February 2021 were enrolled in the present study. All patients were examined for Demodex infection, and their medical history was collected. The positive rate of Demodex infection was calculated after the examination. The medical history, including age, eating habits, pet ownership, and so on, was collected. First, a univariate analysis was conducted to identify the factors associated with positive Demodex infection, and then, a multivariate comprehensive analysis was carried out to identify the main risk factors for positive Demodex infection. RESULTS: In the present study, the positive rate of Demodex infection in 178 MGD patients was 73.60%. The risk factors of Demodex infection in MGD patients were gender, pet ownership, toiletry sharing, and diabetes (all P ≤ 0.15). Age was one of the risk factors for infection [B = 0.105, OR 1.111 (95%CI 1.069-1.155), P = 0.000], and toiletry sharing was more likely to cause positive Demodex mite infection [B = 0.891, OR 2.439 (95%CI 1.066-5.577), P = 0.035]. The Demodex infection was not statistically associated with gender (P = 0.234), pet ownership (P = 1.141), and diabetes (P = 0.295). CONCLUSIONS: The positive rate of Demodex infection was higher in MGD patients. The main risk factors affecting the positive rate of Demodex infection included age and toiletry sharing.

Prevalence of Demodex folliculorum and Demodex brevis in patients with blepharitis and chalazion.

PURPOSE: Demodex folliculorum and Demodex brevis are common ectoparasites on skin that also can lead to blepharitis and chalazion. The aim of our study is to determine the prevalence of Demodex spp. in eyelashes of patients diagnosed with chronic blepharitis and chalazion. METHODS: This study included 330 patients diagnosed with chronic blepharitis, 70 patients diagnosed with chalazion and 130 volunteers without any ocular problems. Patient eyelashes were examined under a light microscope at magnifications of × 40, × 100 and × 400. Demodex spp. were determined. RESULTS: Parasite prevalence was significantly higher in blepharitis (75.5%) and chalazion groups (70%) compared to the control group (16.2%) (p < 0.001). The prevalence of D. folliculorum in the blepharitis group and D. brevis in the chalazion group was found to be significantly higher compared to other groups (p < 0.05). The average number of mites per eyelash was found to be significantly higher in patients with Demodex positive blepharitis (p = 0.001) and in chalazion patients (p = 0.047) than in the control group. It has been determined that mite positivity increases with age in blepharitis and control groups (p < 0.05). In the group with blepharitis, it was found that mite positivity was significant in the presence of symptoms (p = 0.0001) and Demodex positivity decreased as the education level of individuals increased (p = 0.039). CONCLUSION: The results of the study show that Demodex spp infestations should be considered in chronic blepharitis and chalazion.

Attractant Activity of Host-Related Chemical Blends on the Poultry Red Mite at Different Spatial Scales.

Many blood-feeding arthropods use volatile organic compounds (VOCs) to detect their vertebrate hosts. The role of chemical interactions in mediating the behavior of hematophagous insects and ticks has been investigated before but remains poorly understood in hematophagous mesostigmatic mites. The poultry red mite Dermanyssus gallinae is an obligatory blood-sucking mesostigmatic mite that feeds on birds and causes damage in poultry farms. We characterized the attractive response of D. gallinae to candidate VOCs previously reported from the odor emitted by living hens. We performed in-vitro choice-test bioassays as well as semi-field and field trials using baited and unbaited traps, in the presence and absence of hens. Among different tested combinations of VOCs, a blend of 5 VOCs (mix1.0) was significantly attractive to our reference population of D. gallinae in vitro, whereas the same individual compounds tested alone were not attractive. Ammonia was attractive on its own and increased the mix1.0 attractiveness. The attractiveness of mix1.0 was confirmed at 'natural' spatial scales in the absence of hens both at the lab and on the farm that provided the reference population. The presence of hens inhibited the mix1.0 attractiveness. The attractive power of mix1.0 was not found in other farms. This research is an important step to advance our understanding of host-parasite interactions in hematophagous mesostigmatic mites and paves the way for developing alternative control tools against D. gallinae by interfering with chemical interactions. Moreover, it underlines the importance of assessing kairomonal activity on different pest populations when developing attract-and-kill systems.