PREVALENCE OF RUBELLA IGG ANTIBODIES AMONG PRODUCTIVE-AGE WOMEN IN AL-MAHWEET GOVERNORATE, YEMEN

Background: Rubella is an infectious viral disease that caused by the Rubella virus. The incidence of rubella infection in women during pregnancy leads to complications for fetus development and cause congenital rubella syndrome or fetal death. This study aimed to determine the prevalence rate of rubella among reproductive-age women in Al-Mahweet, Yemen. Methods: A cross sectional study was conducted among females attending healthcare centers and schools from July 2007 to June 2008. Blood samples were collected individually from 270 females aged 15-35 years and the rubella virus IgG antibody was quantitated by enzyme-linked immunosorbent assay (ELISA). The needed data were collected by using a pretested questionnaire and analyzed by statistical program. Results: Overall, 197(73%) had IgG-positive antibody to rubella and 73(27%) had IgG-negative antibody to rubella. The highest rate of anti-rubella IgG was among females aged 15-25 years and the lowest was among the females aged 31-35 years. Similarly, the higher rate was among females living in urban area compared to females from rural area. The statistically significant difference was found between most educational levels and positive results of anti-rubella IgG. With regard to marital status, the most frequent of rubella antibody was 72.3%, 73.1%, and 75.0%, respectively, recorded among single, married, and divorced females. The nonpregnant women had (73.7%) more incidence to rubella IgG antibody than pregnant (66.7%). 82.2% of IgGpositive women had no history of stillbirth and 65% had a history of stillbirth. Conclusions: Most of the enrolled females had immunity against rubella virus, but still a significant percentage were susceptible to rubella infection. Thus, it is essential to introduce of rubella vaccine to control and prevent the rubella virus circulating among the community.


INTRODUCTION
Rubella or German measles is a worldwide infection that caused by the Rubella virus. It is a member of Togaviridae family that is enveloped, icosahedral viruses, contain a positive-sense, single-stranded RNA genome 1 . Humans are considered the only reservoir for the Rubella virus transmitted by airborne droplets from infected individuals during sneeze or cough. Both children and adults are susceptible to rubella infection that has an incubation period of 2-3 weeks 2 . In children, the rubella is usually harmlessly characterized by only slightly lymphadenopathy and a mild flat rash with pink to red spots that persistent for three days. Whereas in adults it causes a severe infection that may lead to arthritis or encephalitis 3, 4 . The infected pregnant women by the Rubella virus during the first trimester of gestation can lead to spontaneous abortions, stillbirths, and congenital rubella syndrome (CRS). CRS causes defects in heart, blindness, deafness, and intellectual disability 5, 6 . Globally, approximately 100 thousand of children are annually born with CRS 7 . There are no specific drugs that exist to treatment rubella infection and prevent transmission to the fetus. So, it is important that girls obtain immunity to rubella

SUBJECTS AND METHODS Study Design and Population
This cross sectional study was conducted in the Maternal and Child center at Al-Gomhory hospital and two secondary schools namely Al-Khansa'a and Aisha, from July 2007 to June 2008, that located in Al-Mahweet governorate. Ethical approval for this study was obtained from the ethical committee of the Faculty ofMedicalSciencesofSana'aUniversity.Theaimsof this study are explained in brief to each participated female and gave consent.

Data Collection
A structured and pre-tested questionnaire was approved by the Faculty of Medical Sciences of Sana'a University. The questionnaire was structured to included socio-demographic information (age, marital status, residence, educational level, occupational status), pregnancy status, and history of clinical information. The participants interviewed face to face and questionnaire filled by the researcher.

Specimens Collection and Examination
Five mL of blood samples were collected from each participated woman by venous puncture and serum separated by centrifuge. The obtained sera stored at -20°C until the serological analysis was performed. The anti-Rubella virus IgG antibodies were quantified by enzyme-linked immunosorbent assay (ELISA) (Equipar SRL, Italy). The concentration of IgG antrubella in serum sample ≥20 IU/ml were considered positive.

Statistical Analysis
The obtained results were analyzed by SPSS version 18 (SPSS Inc., USA). The relative risk (RR ˃1), 95% confidenceinterval(CI),Chi-squaretest(χ 2 ), and value of probability P<0.05 (significant) were used to examine the significance of the relations between the prevalence of rubella IgG antibody and potential risk factors.

Figure 1: The distribution of rubella IgG antibody result RESULTS
A total of 270 females aged 15-35 years (mean age 21.9 years) attending healthcare and schools were enrolled in the study. The present findings revealed that the overall prevalence rate of rubella IgG antibody was 197(73%) positive recorded among females. Whereas 73(27%) of participants were negative for rubella IgG antibody ( Figure 1). The current results according to age found that the highest prevalence of rubella IgG antibody frequency was reported among age-group 15-25 years and the lowest frequency rate was found among the age group 31-35 years. Also, there were no statistically significant differences between rubella IgG antibody prevalence and age group listed in Table (1). The females coming from the urban area had the highest rate (75.2%) of the rubella IgG antibody when compared to females coming from the rural area and there were no statistically significant. The result regarding occupation showed that the higher rate of rubella IgG antibody was recorded among employee females (74.5%) followed by a student (72.5%), and house-wife (71.6%), and there also were no statistically significant ( Table 1). The current work according to the educational level, it was found that the most frequent of rubella IgG antibody was recorded among the secondary level (92%) followed by the illiterate (90.9%), university (66.2%), elementary (50%), and primary level with 38.1%. The results of elementary, secondary, primary and finally illiterate in terms of rubella IgG positivity were highly statistically significant withvaluesofχ 2 =30.65, P=0.000001;χ 2 = 29.18, P=0.000001;χ 2 = 7.04, P=0.007andfinallyχ 2 = 6.14, P=0.01 respectively, ( Table 1). The result based on marital status showed that the nearly similar positive results were noticed among single, married, and divorced females with percentages of 72.3%, 73.1%, and 75.0%, respectively. In contrast, the two of the participated widow females showed completely positive for the anti-rubella IgG antibody (Table 1).
In the result according to the pregnancy, the higher prevalence of rubella IgG antibody was (73.7%) reported among non-pregnant women, while the lower was (66.7%) noticed among pregnant women and there was no statistically significant difference as summarized in Table 2.  However, out of 130 married females, the rubella IgG antibody was more prevalent among women who had no history of stillbirth with 82.2% whereas 65% of women who had a history of stillbirth showed positive for rubella IgG antibody and there is no statistically significant difference ( Table 2). Out of the 197 positive studied females, 25 (73.5%) of females had a family history for rubella and the rest 172(72.9%) of positive females had no family history for rubella and there were also no statistically significant (Table 2).

DISCUSSION
Rubella has a worldwide distribution with the infection being endemic in all countries that had not a highly successful infant immunization policy or no immunization policy at all. An outbreak of rubella usually occurs in winter, spring, and early summer and spreads very easily through airborne droplets within the community 16 . The current study revealed that 73% of studied females were showed positive for rubella IgG antibody while 27% of females were negative. These findings are lower than the rates recorded from several studies among women where the prevalence rates of rubellaIgGantibodywasreportedas91.64%inSana'a city 14  Jeddah, Saudi Arabia 9 , 26-30 years in Egypt 22 , 26-35 years in Mosul City, Iraq 23 . The vibration on the increase in different age groups doesn't seem to represent a risk factor. The seroprevalence rate for the rubella antibody in this study showed an increased rate among women coming from the urban area, but no statistical differences were reported between the resident group and the prevalence of anti-rubella IgG. Similarly, a higher rate of IgG anti-rubella prevalent was recorded among females residing in the urban area in Mosul city, Iraq 23 . Also, it was found that the high rate was recorded among assayed women for rubella IgG antibody living in urban area in Ethiopia 24 . Conversely, a study by Sallam et al.,8 observed that the participants from the rural area had a higher prevalence rate of rubella IgG antibody than the urban area. Also, Gadallah et al., 22 noticed that the participants belong to a rural area having a high rate than participated women coming from an urban area. Olajide et al., 19 found that the prevalence rate of rubella IgG was 93.8% and 90.3% in urban and rural areas, respectively. The differences in the prevalence rate of anti-rubella IgG in the present study might be attributed to the variance density of the population. In the urban area, the high density of the population might increase the transmission rate and females who do not have protective levels of rubella resistance might get the infections. In the current result according to the occupation, it was observed that the high rate of rubella IgG antibody prevalence was recorded among employed females followed by the student, and housewife, and there were no statistically significant differences. In a similar investigation by Olajide et al., 19 reported that the prevalence rate of rubella IgG was 93.2%,93.4%, and 92.5%, respectively, among students, workers, and housewives. Also, Wondimeneh et al., 24 revealed that most frequent rubella IgG antibody was recorded among student (88.9%), farmer (88.6%), merchant (88.1%), civil servant (77.8%), housewife (77.3%), and daily laborer (74%). In this work, the seroprevalence of anti-rubella IgG antibody in association with the educational level showed that the highest positive results were most frequently reported at the secondary level, followed by the illiterate, university, elementary, and finally the primary level. Also, the statistical analysis results showed the highly significant (P<0.05) differences between anti-rubella IgG prevalence and most of the educational level except individuals having a university degree. These findings are in agreement with Wang et al.,24,25 in Taiwan illustrated the university grade and primary to secondary school individuals show nearly similar antirubella prevalence and no significant differences. The variation in previous results to this result may be referred to as many factors that play a minor role in rubella virus infection. These factors including frequency of exposure, diagnosis methods, the social variations such as the behavior of the population, environmental hygiene, and cultural variances related to feeding habits, levels of the educational, and primary healthcare program. In the present result, the single, married, and divorced females showed nearly similar results for anti-rubella IgG that ranged between 72.3% to 75%. The two of the participants who were widows showed comparatively positive for the anti-rubella IgG antibody. This finding is in agreement with Gadallah et al., 22 who observed that the prevalence rate of antirubella IgG was 84.6% and 80.3%, respectively, among married and single women. In contrast, Wondimeneh et al., 24 noticed that the highest rate was among married and lowest among single and divorced women. Also, it was found the rubella IgG antibody among unmarried women were more than in married women 23 . In fact, all women are exposed to rubella infection and the high potential risks present during pregnancy period. In the current work, out of the 130 married females, it was reported that the highest prevalence of anti-rubella IgG were (73.7%) among non-pregnant women and the lowest was 66.7% among pregnant women. In a similar study conducted in Poland, it was found that up to 90% of healthy pregnant females were positive for rubella antibody 17 . In Nigeria, Olajide et al., 19 observed that anti-rubella IgG prevalence was 93.75% among pregnant women and 90% among non-pregnant women. Also, in a study conducted in Iran among pregnant women that 15% of them were positive for rubella antibody 26 . The current result according to the history of stillbirth, it was found that 82.2% of IgGpositive study participants with no a had history of stillbirth were positive, whereas 65% of IgG-positive women had a history of stillbirth. In a similar study, Olajide et al., 19 showed that 92.5% of females with no history of stillbirth were IgG-positive for rubella and 100% of IgG-positive females had a history of one to four stillbirth. Also, Wondimeneh et al., 24 reported that 79.2% of IgG-positive without a history of stillbirth, and 82.4% of IgG-positive females had a history of one to three stillbirth. However, the result in this study revealed that 73.5% of females IgG-positive had a family history for rubella infection and 72.9% of IgGpositive females had no family history for rubella infection. It is noticed from this result that, there were no statistically significant differences between the families with history for rubella and the families without rubella, indicating that previous history for rubella does not influence the prevalence of infection.

CONCLUSION
The high prevalence of rubella IgG antibody among enrolled females indicates that they had immunity against rubella virus. But, there are about a quarter of assayed females remain susceptible to rubella virus infection and cause the complications antenatal during