The Level of Vitamin A and Selenium of Cystic Echinococcosis in Aba and Garze Tibetan Autonomous Prefecture , Sichuan, China

Background Cystic echinococcus (CE), socioeconomic Methods Eighty-nine echinococcosis patients and 274 controls from the Aba and Garze Tibetan Autonomous Prefecture of Sichuan province in China were recruited. The serum levels of Selenium (Se) and vitamin A (VA) of the cases and controls were detected and stratied by age and gender. Results The results showed that the male to female ratio of the patients was 1:1.97. The echinococcosis patients were mainly adults. It was conrmed that the serum levels of VA and age were correlated. Compared with the healthy controls, the serum levels of Se and VA of the cases signicantly declined in both children and adults.


Results
The results showed that the male to female ratio of the patients was 1:1.97. The echinococcosis patients were mainly adults. It was con rmed that the serum levels of VA and age were correlated. Compared with the healthy controls, the serum levels of Se and VA of the cases signi cantly declined in both children and adults.

Conclusions
It was con rmed that the serum levels of Se and VA were interrelated with the prevalence of echinococcosis.

Background
Cystic echinococciasis (CE), a hydatid disease, is a neglected yet serious threat to public health [1]. The parasitic disease is caused by the ingestion of tapeworm eggs from the species E. granulosus s.s. (G1) and E. canadensis (G6/7, G8, and G10) [2,3]. These species of the echinococcus are highly endemic to China and especially prevalent in the western provinces including Sichuan [4][5][6]. On an individual level the disease presents a poor prognosis, with high morbidity and mortality rates and causes serious socioeconomic costs [7] often to already vulnerable populations. Infection is highly variable in endemic regions and dependent upon human behavioral risk factors [8].
CE is most commonly associated with the liver [3], an important metabolic organ. The liver stores and metabolizes trace elements including Vitamin A (VA) and Selenium (Se). VA is needed for normal growth and development and maintenance of regular reproductive ability. Variations in the levels of trace elements can in uence immune function as well as the infection status of parasite [9]. Researchers have begun to study the relationship between trace elements and echinococciasis. Yet the serum levels of vitamin A and selenium in Sichuan are limited. In this study, we analyzed the serum levels of Se and VA in echinococciasis patients and healthy controls in Aba and Garze Tibetan Autonomous Prefecture of Prevention of Garze Tibetan Autonomous Prefecture, all the patients were con rmed through B-ultrasonic examination. The control group were the 274 healthy local residents. The case to control ratio was 1:3.08.

Data Collection
Blood samples (1 mL) were collected from the cases and controls with coagulant and centrifuged at 3000rmp for 10 min. The serum was collected and stored at -20 °C. Before detection, the standard curve was established. 20µL serum was mixed with 50 mL methyl alcohol (contain 0.5 µg/mL internal standard of Vitamin A acetate 3-4% CIS). After degeneration, precipitation, and mixture with trichloromethane, retinol was extracted completely. Finally, 180µL retinol was isolated and dried by nitrogen and dissolved with 100µL methyl alcohol (contain 5% dichloromethane). The liquid was used to detect VA by HPLC-MS/MS. Gradient ascent of national standard Se (GSB04-1751-2004) were mixed with 100µL serum for the Se test. After 15 minutes standing, the sample was diluted by Nitric acid solution and detected using ICP-MS.

Data Analysis
Location, sex, and age of the cases were analyzed with descriptive statistical methods. Spearman correlation analysis was performed to measure the statistical dependence between combinations of the variables using SPSS. The criterion for signi cance was P < 0.01.

Results
Eighty-nine CE patients and 274 healthy controls from the Aba and Garze Tibetan Autonomous Prefecture of Sichuan (Table 1). The average age of cases was 39.3 (22.2) while the average age of the controls was 16.6 (11.5). Of the 89 echinococciasis cases, 30 were males (33.7%) and 59 were females (66.3%). The male to female ratio of the cases was 1:1.97. Of the 274 controls 137 were males (50.0%) and 137were female (50.0%). The male to female ratio of the cases was 1:1. The echinococciasis patients were divided into 2 age groups children and adults. Of the cases 29 were children (32.6%) and 60 were adults (67.4%). The ratio of adults to children was 1:2.1. Of the controls 205 were children (74.8%) and 69 were adults (25.2%). The ratio of adults to children was 1:3.0. When Se de ciency level was strati ed by gender and age group, females and children had a higher number of Se de ciency cases as compared to males and adults without a signi cant difference (Fig. 1). Similarly, when VA de ciency level was strati ed by gender and age, females and children had a higher number of VA de ciency cases as compared to males and adults with a signi cant difference among the age strati ed comparison (Fig. 2).
The correlation between the variables of VA de ciency, age and gender demonstrates a signi cant effect only for VA de ciency and age ( Table 2).  (Fig. 3). When Se de ciency level was strati ed by age among cases/controls, both children and adult cases had signi cantly higher Se de ciency as compared to controls (Fig. 4).

Discussion
There is an important relationship between trace elements and parasite infection. Many parasites can reduce the levels of trace elements of host, such as Se [10]. The body needs more trace elements while combating a parasite infection. Echinococcus cysts also absorb trace elements from the host to support their growth and development. Therefore, the serum level of Se and VA of an echinococciasis patient will be lower than in echinococcus cyst uid [11,12].. This interdependency may support a possible cure for parasitic disease.
In this study, the data of 89 echinococciasis patients in Aba and Garze Tibetan Autonomous Prefecture of Sichuan province were analyzed. The male to female ratio of the cases was 1:1.97 and gender is a known risk factor for infection [3,8]. This known risk factor is often explained by cultural economic production habits, as women are often engaged in animal raising and the upkeep of the home increasing their exposure of the echinococcus cyst via infected dogs and livestock [3,8].
The echinococciasis patients were mainly adults (58%) where the controls skewed towards a lower age range. Age is a known risk factor for echinococcus infection [3,8]..Adults have more opportunity to be infected with echinococcus cyst while in productive activities. Due to the lack of early diagnosis of echinococciasis, young cases infected with echinococcus cyst are rarer. Most studies lack data on infections in children [13] while ours was able to account for their inclusion.
In this study, the serum levels of Se and VA of the echinococciasis patients were signi cantly downregulated compared with the healthy people, which was consistent with the result of a previous study13]. Animal studies also show similar results in the decline of VA in hydatid infected specimens [14]. Su cient damage to the liver, due to the number and type of parasites, can cause acute and chronic hepatic insu ciency in uencing the digestion, absorption, or metabolism of trace elements. Furthermore, progressive liver disease results in noted depletion of hepatic retinoid and VA content in humans [15].