Discussion
In the present research, the incidence rate of CL was 1.7 cases per 10,000 people in both 2013 and 2014 years. One of the causes of the injury is traveling to areas where the disease is native. If people and especially non-indigenous people are exposed to carriers for any reason, the incidence
of the disease will increase. Migration and demographic changes cause a change in the disease trend and in fact, population displacement is a very prominent factor in causing CL epidemic
19.
According to the results of the current research, the scattered age distribution of patients showed that the incidence of CL in the 0-4 age group was higher in years 2013 and 2014, which could be due to various reasons, including higher outdoor exposure seen in this age group because of the child's play and safety and the lower safety of this age group
20. Also, the high incidence of CL in the age group of 15-24 years can be due to a variety of reasons such as illiteracy, and working in fields and gardens at night (during which sand flies are active) without protective cover. Since people in this age group are mostly farmers and workers in the studied area and have low income levels, they are more likely to be exposed to sand flies
17, 19. The least incidence of CL was seen in the age group of over 45 years in the years 2013 and 2014. The reduction in the incidence of the disease in the age group of over 45 years in years 2013 and 2014 could be due to many reasons, including less exposure with outdoors, lower workload and finding permanent safety because of the development of the disease at an earlier age
13. In addition, the disease incidence in the age group of 35-44 years in years 2013 and 2014 was 6 (14%) and zero, respectively. Increased expertise and awareness level about preventive measures may be the reason for the minimum incidence of the disease in this age group. There is a reduction in the number of patients at older age in most researches, which poses more seriously the need to design preventive measures against CL. According to the results of studies conducted by Talary in Kashan
21, Hanafi-Bojd in Hormozgan
22, Yaghoubi in Yazd
23, Soleimani in Hormozgan
24, Gorel in Sanliurfa
25, and Babaei in southern part of Lorestan
26, the highest incidence of CL has been observed in the age group under the age of 10 years and is consistent with the results of the present study. Also, in a study on CL epidemiology in Damghan, Mohammadi Azni et al. showed that the mean age of the patients was 33.5 years and their age ranged from 1 to 94 years. The highest and lowest prevalence rates were observed in the age groups of 20-29 and more than 70 years, respectively. There was also a significant relationship between the incidence of the disease in different age groups (p < 0.0001)
27. In a study on the prevalence of CL infection in the city of Mohammad Abad, Jiroft city in Kerman province, Porsmaeilian et al. reported the highest and lowest infection rate in the age groups of 11-20 (10.5%) and 21-30 years (3%). The most common age group was 15-24 years and 7.85% of patients were in the age group of 15-45 years
8. In a study on the epidemiology of CL in 210 patients in Hamedan province during the years 2002-2007, Zahirnia et al. showed that 44.3% of patients were in the age group of 15-24 years
19; however the results of some other studies such as those conducted by Sdqyany in Tehran
28 and Sadeghi Nejad in Khuzestan
29, are not consistent with the results of the present research. In general, by measuring the results of numerous studies, it can be concluded that CL incidence rate in different age groups is dependent on different foci, and the age distribution is related to the native nature of the disease.
Scattered gender distribution of patients shows that the incidence of CL in men and women in years 2013 and 2014 was 25 (58.1%) and 24 (55.8%), 18 (41.9%) and 19 (44.2%), respectively. There was no significant change between men or women in terms of the incidence rate of the disease in years 2013 and 2014; however, the disease incidence rate was generally higher in men than in women, which may as a result of higher exposure to the outdoor environment for occupational purposes, sleeping outdoor and in uncovered areas, less body-coverage in men than in women and more frequent commuting in abandoned and desert areas, which have increased the likelihood of contact with sand flies and bites in men as compared to women
19. In a study on CL epidemiology in Damghan, Mohammadi Azni et al. showed that out of 465 patients with CL, male and female subjects accounted for 263 (56.5%) and 202 (43.5%) of participants, indicating that the disease was more prevalent in men than in women
27. Likewise, in a study on CL epidemiology in Khorasan Razavi province, Khajeh Deloyi et al. demonstrated that out of 3,558 patients with CL, 52% were male
30. In a research on the epidemiologic factors of skin leishmaniasis in 727 patients referred to health centers in Kermanshah province, Hamzavi et al. showed that the prevalence of the disease in men was 12.2 times that of women
31; however, the results of some researchers are not consistent with the results of the present study; for example, Poursmaeilian et al. investigated the prevalence of CL infection in the city of Mohammad Abad, Jiroft city in Kerman province. They performed a physical examination on a total of 3516 people, including 1743 female (49.6%) and 1773 (50.4%) male subjects; the results showed that the prevalence of CL infection was 5.3% (6.2% and 4.5% for female and male genders, respectively), and a significant difference was observed between the two genders (p < 0.05)
8. Also, Talary in Kashan
21, Ebadi in Isfahan
32, Karimi Zarch in Sarakhs
33 and Drodgar in Kashan
7showed in their researches that the infection distribution was higher among females. The higher prevalence of the disease among female participants in these studies was attributed to the economic activities of women and carpet weaving in dimly lit rooms and basements; since sand flies are also dynamic during days in these places and continue to feed from human blood
23. The inconsistency between the results of these studies and those of the present study may be due to the fact that most of the men are engaged in agricultural activities outside the house during the night hours and do not have adequate clothing due to the warm weather owing to the warm and dry desert climate of Dashtestan, which lead to more prevalence of the disease among men than women; however, weather conditions are much better in provinces such as Isfahan, Kashan, Kerman and Khorasan Razavi as compared to Dushtestan, and men have better clothing. There is also a higher incidence of the disease in women than in men in some provinces, which can be attributed to cultural differences in different provinces.
According to the results, the maximum frequency of ulcer site in CL in 2013 and 2014 was seen in the face with frequencies of 15 (34.9%) and 20 (46.5%), respectively, which may be due to lack of insufficient skin coverage in this part of the body in men and women. The least frequent ulcer site in CL was observed in the trunk with frequency of 1 (2.3%) in year 2013, which can be due to sufficient skin coverage in this part of the body in men and women. The least frequent ulcer site in cutaneous leishmaniasis was observed in the hands and face simultaneously (0%) in year 2014. Also, in year 2014, the frequency of ulcers site in the hands and face was low at the same time, indicating that the ulcer site was mainly seen in one member during the onset of this disease. Reduced ulcer sites in the hands and face in 2014 may be due to increased awareness of people about the disease and the recognition of ways to prevent the disease, which has made people to cover open areas of their body such as the face and hands. The most affected organ was the face in researches conducted by Ebadi in Isfahan
32 and Karimi Zarch in Sarakhs
33 which is consistent with the results of the present study. Considering the short mouthparts or proboscis of mosquitoes that allow the blood to be absorbed from the covered parts of the host's body, it is thus likely that the upper and lower extremities will be bitten by sand flies
34, 35. Furthermore, sand flies use odor and chemical attractions such as carbon dioxide to select and choose the proper host and the intended site, which directs the insect to find the proper host and the intended site and these absorbent materials are more abundant in the hands and legs than in the other parts of the body
36, 37. In a study on the prevalence of CL in the city of Mohammad Abad, Jiroft city in Kerman province, Porsmailian et al., showed that most of the skin ulcers were seen in the face (47%), then in the hands (34%), legs (5%) and several other sites (14%) (4); however, the results of researches conducted by Talary in Kashan
21, Hamzavi in Kermanshah
31, Zahirnia in Hamedan
19 and Kasiri in Khorramshahr
34, are not consistent with the results of the present study and the most affected organs included the hands and face. In a study on the incidence of CL in Chabahar province, Moghateli et al. showed that most of the skin ulcers were seen in the hands and legs (94%), then face (35%) and other parts (14%) in 2008 and there was a decreasing trend in the percentage of ulcers by 2010
38. In a study on CL epidemiology in Damghan, Mohammadi Azni et al. showed that out of 465 infected individuals, hands, face and leg ulcers accounted for 49, 35 and 8.6% of cases, respectively and the hands and legs accounted for 7.4% of ulcers site
27. The reason for the inconsistency between the results of these researches with the present study may be due to the fact that the bite location and subsequent the ulcer site was also different depending on the type of clothing used by individuals in various climatic zones. Therefore, depending on the rituals and dressing styles of the inhabitants of different areas and the bloodthirsty habits of sand flies, the organs with the highest CL ulcers are different in different parts of the world and even in one country. In addition, the results showed that the maximum frequency of CL-induced ulcers (N = 1) in 2013 and 2014 were observed with frequency of (67.4%) and 18 (41.9%), respectively. Also, the maximum frequency of ulcers (N = 2) was observed with frequency of 4 (9.3%) and 10 (23.3%) in the same years, respectively, which is consistent with the results of studies conducted by Ebadi
32, Babaei
26, and Hamzavi
31; however, Zahirnia in Hamedan
19, Rafati in Damghan
36 and Hamzavi in Bushehr
10 indicated in their research that more than 60% of the patients had more than one ulcer in their body. The number of CL-induced ulcer is multiple, with the least frequency of (more than 3). The cause of multiple ulcers can vary, which includes the method of blood-sucking of sand flies (because these insects carry out various bites for each stage of blood sucking), the manner in which people are covered and high abundance of the infected sand flies in a region
19. Also, the number of ulcers may be due to getting infected bites at various times, or by spontaneous inoculation by scratching.
The best temperatures include 23-28 ºC and the best moisture content is 70-100%
19. According to the results of the present study, in years 2013 and 2014, the maximum CL incidence was seen in September and January with frequency of 7 (16.3%) and 9 (20.9%), respectively. Considering air temperature and humidity in other studies, the peak of the disease incidence has been reported in other months. In a study on CL epidemiology in Damghan during the years 2006-2015, Mohammadi Azni et al. showed that the highest incidence was in the months of October, November and December, and attributed it to the fact that there are significant changes in the incidence of rural CL in different months of the year, and the highest incidence rate is observed in the foci of the country in October, November and December
27.
According to the results of this study, the maximum incidence of CL disease was observed in autumn of 2013 with the frequency of 15 (32.8%). This conclusion is consistent with the studies conducted by Hanafi-Bojd in Hormozgan
22, Nejati in Andimeshk
12 and Nilforoushzadeh in Isfahan
39. Furthermore, the highest incidence of CL in the winter of 2014 was 20 (46.5%), which is consistent with the researches carried out by Talary in Kashan
21 and Hamzavi in Kermanshah
31. Considering that the Latency period of CL is between two weeks to two month, it is predicted that the ulcers will be more frequent in the winter and autumn. According to the results of the current research, the incidence of CL in 2013 in urban areas with a frequency of 22 (51.2%) was higher in rural areas with a frequency of 21 (48.8%), which is consistent with the conclusion made by Nejati in Andimeshk
12. Considering that the health status in urban areas is better than rural areas, the elevated CL incidence in urban areas in Dashtestan province in year 2013 may be attributed to the droughts of previous years and the migration of large numbers of villagers to Dashtestan city, construction of affordable buildings around the city and close to low-income mountainous areas, population growth, increased frequency of carriers and unhealthy waste disposal. The results obtained in year 2014 were contrary to that of 2013; the incidence of CL in urban and rural areas was 17 (39.5%) and 26 (60.5%), respectively. The reduced incidence of CL disease in urban areas in year 2014 could be due to increased public awareness by health centers and the prevention of this disease.
In this research, CL disease incidence rate was determined in Dashtestan district. However, further studies are required in order to identify the animal reservoirs of this disease in this district and determine the optimal methods to combat female sandflies.
Conclusion
Based on the results of the current research, the incidence of CL disease in Dashtestan was equal to 1.7 per 10,000 in both 2013 and 2014. Overall, the highest incidence rate in children, adolescents and young adults has been observed in years 2013 and 2014. The incidence of the disease was higher in urban areas than in rural areas and in men than in women. The highest incidence of the disease was also observed in the winter and autumn and in September and January. It can be concluded according to the results of this research that CL is highly endemic in Dashtestan province and is considered as a health challenge in this city; therefore, it is necessary to consider planning for disease prevention and perform further research to reduce the incidence of the disease.
Acknowledgments
The authors of this study would like to appreciate staffs of the healthcare network and the Department for the prevention and combating of diseases in Dashtestan Province who contributed to the data record and helped us to carry out this research.
Funding
The work was unfunded
.
Conflict of interest
The authors declare that there is no conflict of interest.
This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work for commercial use.
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