Differences of Facial Infection with Demodex spp. Between Indian Students and Native Students in Jiamusi University

Demodex is an ancient pathogen with is a contributor to chronic diseases such as acne rosacea or marginal blepharitis. Recently people found that many kind of diseases correlate with demodex infection, it begin to attract wide interest. At present, we want to evaluate the prevalence of facial infection with demodex spp, among international and local students in Jiamusi University of China. Using skin scraping method to obtain secretions, and then put the secretions to the drop of glycerol on a glass slide. The sample was covered with a cover glass and examined for parasites by light microscopy at 10× and 40× objective. Results showed that the infection rate in foreign students and local students were 15.2% (57/375) and 34.5% (203/588) respectively. There was a statistically significant difference between international students and local students in demodex infection rate (χ 2 = 43.38, P < 0.05). There was a dominance of Demodex folliculorum infection in male of international students and local students, which are 63.6% (28/44) and 69.6% (94/135); followed by Demodex brevis infection, which are 22.7% (10/44) and 22.2% (30/135); last one is mixed infection, which are 13.6% (6/44) and 8.1% (11/135). Interesting, the infection rate of mixed demodex from local female students was the highest in total students. In addition, demodex infected local students with facial symptoms (67.9%) were significantly higher than those showing healthy facial skin (21.5%) (χ 2 = 112.9, P < 0.05). Thus, one can conclude that the probability of Demodex infection is comparable for foreign students and local students unalike, which is related to examination methods, examination season, temperature, living environment, human race possibility.


Introduction
Demodex was first identified over 150 years ago, [1] just belongs to the class of arachnids (Arachnida), the scab mites subdivision (Acarida) and the hair follicle mites family (Demodiacidae). These mites prevail all over the world and are characterized by a parasitic existence, and commonly parasitised hair follicles, sebaceous glands and eyelid glands, which may evoke demodecosis in both human and animals, the course of which is chronic. [2][3] The 2 kinds of demodex mites that have been identified in human: Demodex folliculorum (D.f) and D. brevis (D.b), commonly appear in seborrheic areas of the facial skin (the forehead, chin, and around the eyes and mouth) that affect human skin. [4][5] In addition, they are also observed on the pileous skin of the head, on hairy chest or in the genital area. [6][7][8][9] D. f live in hair follicles or sebaceous glands., and occur in concentrations and the disease progresses as the patient's age increases. In turn, D. b is usually located in the meibomian glands, and is found to live individually and morbidity is not age dependent. [6] Patients generally have no symptoms, but it occasionally causes some skin diseases. [10][11] Demodex occurs all over the world in almost all human races, including various ethnic groups such as aborigines and Eskimos. About 80-90% of the human population is infected with demodex; however, D. folliculorum is more often found in females than in males. [7] Recently, there are reports in the literature that the infection rate of demodex mites is high and the incidence increases with age. [2] Meanwhile, it is postulated that demodex mites become pathogenic when they multiply and cause or exacerbate ocular symptoms and eyelid margin changes. [12] The infection rate of population was observed to be 84% at age of 60 and 100% in people older than 70. [13] It is worth mentioning, the infection rate of demodex mite was reported from 27.0% to 100% in foreign countries and from 0.8% to 81.0% in China. The difference of demodex infection between foreign countries and China, may be closely related to various factors such as examination methods, time and environment. Therefore, the aim of the present study was to evaluate and compare the infection status of facial demodex in different ethnic groups，a survey was conducted in 2015-2017 grade local college students and 2013-2015 grade Indian students (hereinafter referred to as foreign students) as well as local college students (hereinafter referred to as local students) of Jiamusi University.

Study Population
375 foreign students in Jiamusi University were detected, including 257 males and 116 females aged from 18 to 29. All foreign students come from India. They just communicated with local students since entering university. However, they don't live and study at the same place with local students. 588 local students took part in this study, including 285 males and 303 females aged from 18 to 24. Meanwhile, 91% of local students come from Heilongjiang province and 9% of local students come from other provinces of China (including Xinjiang and Tibet). Informed consent was obtained from all participants included in the study. The study was approved by the ethical committee of Jiamusi University.

Demodex Examination
The sampling and counting of demodex mites can be affected by personal and environmental conditions. Therefore, all measurements were made from the same region of the face (two side of nasolabial groove), in the same room of the parasitology laboratory to reduce any errors in the techniques and microscopic examinations.
In this study, skin scraping was used to identify the presence of demodex mites as a qualitative method. [14] Using scraper to obtain secretions, and then put the secretions to the drop of glycerol on a glass slide. The sample was covered with a cover glass and examined for parasites by light microscopy at 10× and 40× objective.

Statistical Analysis
The collected data were analyzed using graphpad prism 7 software. The infection rate was calculated for each population and the χ 2 test was used for comparison between groups. Inspection level α =0.05.

Infection Status
Among the 963 students examined, 260 students were infected by demodex, which the rate of positive infection was 27%. In international students the rate of demodex infection was 15.2% (57/375); 17.1% (44/257) for male and 11.2% (13/116) for female; However, in local students the rate of demodex infection was 34.5% (203/588); 47.4% (135/286) for male and 22.4% (68/303) for female. There was a statistically significant difference to the rate of demodex infection between international male students and local male students (χ 2 = 55.9, P < 0.05). In addition, there was no statistical difference to the prevalence of infection among international students (χ 2 =2.159， P＞0.05). However, there was a statistically significant difference to the prevalence of infection among local students (χ 2 =40.37, P < 0.05) ( Table  1).

Infectious Species
The

Discussion
Demodex are cosmopolitan mites occurring in many species of mammals, and was regard as the most common ectoparasite in humans. [15] Two morphologically distinct demodex species parasitize on humans: Demodex folliculorum (D.f; Simon, 1842) and Demodex brevis (D.b; Akbulatova, 1963). D.f and D.b are ectoparasites with a prevalence of 100% in patients aged 96 and older. [16][17] In people, Demodex spp. can be found mainly in the sebaceous glands of the skin (the forehead, chin, and around the eyes and mouth). They are also observed on the pileous skin of the head, on hairy chests or in the genital area. [18][19][20][21] Nevertheless, the infection rates of demodex in various regions is different, the infection rate in adults ranged infection from 27% to 100%. [22] In this study, 375 foreign students were surveyed, 57 of whom were infected by demodex mite, the rate of positive infection was 15.2%. 588 local students also were surveyed at the same time, 203 of whom were infected by demodex mite, the rate of positive infection was 34.5%. Interestingly, we found that the infection rate of demodex is very different between foreign students and local students. In addition, it is obviously lower than that data reported in relevant papers in foreign students. Therefore, we have comprehensively analyzed the key point of differences in epidemiological surveys. Based on the performed analyses, it was determined that examination methods, examination season, temperature, living environment, human race have impact on demodex infection.
In addition, all students come from medical schools and possessed certain medical knowledge, since they known how to prevent demodex infection compared with ordinary students. Demodex positivity is affected by many factors, including season，temperature, light, insect species, human health and hygiene habits, human race, endocrine metabolism, cosmetics and drinking etc; which were the key factors in spreading the epidemic. [23][24] In addition, different examination methods also affect demodex positivity. Nowadays, there were many new methods to check demodex infection. The confocal microscope (CLSM) imaging technology has high diagnostic efficiency for facial demodex and it has advantages including being in-body, non-invasive painless, real-time and dynamic. However, it can not be used as a clinically universal diagnostic method because of its high price. [25] To be mentioned, researcher clarified that the infection rate of D. folliculorum in females is higher than that in males. [7] Inconformity, in this survey, results found that the infection rate of D.f in total male from foreign students and local students is higher than that in total female from foreign students and local students. However, at present we don't know what is the main reason for the infection difference between literature report and in this survey.
This survey found that demodex positivity in local students, not foreign students, correlated with skin status. Demodex positivity in symptomic facial skin of local students is significantly higher than in asymptomatic individuals. However, there was no significant correlation between the infection rate of demodex and facial skin conditions in foreign students. To be mentioned, most of foreign students were dry skin without excessive secretion of sebumthus patients with rosacea, acne and seborrheic dermatitis were rare. Beacause demodex infection can induce appearance or aggravation of facial skin symptoms, patients with rosacea, acne and seborrheic dermatitis need detection and treatment early in order to reduce or avoid appearance or aggravation of facial skin symptoms.

5.Conclusion
Demodex positivity is affected by many factors. The race, living environment and facial skin conditions are the main reasons for the difference in demodex positivity between foreign students and local students. Although demodex infection is less harmful, there is no way to control the prevalence of demodex leading to damage of facial skin, including rosacea and acne-like skin rashes and so on. Demodex infection not only affecting the physical health, but also influencing mental health in young people. Therefore, detection, prevention and treatment during early stage of demodex infection is of the utmost importance.