| Abstract|| |
Background: Eye examination is a routine part of the periodic pediatric assessment. Prevention of visual impairment due to congenital cataract is now an international priority. Objectives: To screen infants with nontraumatic congenital cataract for rubella infection, then to determine the prevalence of congenital rubella syndrome (CRS), and to assess the associated problems. Design, Setting, Participants, and Intervention: A prospective hospital-based study conducted at two eye hospitals in Khartoum, Khartoum, Sudan, from March 15, 2011 to August 15, 2011. The studied group comprised infants, below 1 year of age, presenting with congenital cataract. A properly designed questionnaire was used for the collection of data. Blood samples of the infants were tested for the presence of specific immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies by the enzyme-linked immunosorbent assay (ELIZA) method. The data were statistically analyzed using SPSS software. Results: The number of studied infants with congenital cataract was 104, with the average age being 6.8 months. Male to female ratio in the positive cases was 1.3:1. Of the 104 children, 14 (13.5%) were positive for rubella infection. Of these 14 positive infants, 13 (93%) were below 6 months of age. This indicates that almost all the positive cases can be detected before the age of 6 months. Two (14.3%) mothers had a history of fever and skin rash during pregnancy. Of all the positive infants, 13 (93%) had bilateral congenital cataract. Conclusion and Relevance: Of the studied infants, 14 (13.5%) were positive for rubella infection, indicating a significant prevalence rate. Of the infants who were positive for rubella infection, 93% were below 6 months of age, indicating that the detection of this infection is highly possible early in life. So, taking the test as early as possible is recommended. Introduction of rubella vaccination in our national immunization program is recommended. Proper surveillance and reporting of all cases of CRS with urgent and long-term management programs are recommended. More studies on a larger scale are needed in our country.
Keywords: Children, congenital cataract, rubella, screening
|How to cite this article:|
Satti SA, Mohammed EE, Fahmi AM. Screening of infants with congenital cataract for rubella infection. Ann Trop Med Public Health 2016;9:19-22
|How to cite this URL:|
Satti SA, Mohammed EE, Fahmi AM. Screening of infants with congenital cataract for rubella infection. Ann Trop Med Public Health [serial online] 2016 [cited 2020 Sep 21];9:19-22. Available from: http://www.atmph.org/text.asp?2016/9/1/19/168721
| Introduction|| |
Eye examination is a routine part of periodic pediatric assessment.  Prevention of visual impairment due to congenital cataract is now an international priority and is an important component of the international program of the World Health Organization (WHO) for the elimination of avoidable blindness by 2020.  Intrauterine rubella infection still remains a major source of cataract, especially in developing countries.  Congenital rubella syndrome (CRS) is an important cause of cataract, deafness, heart disease, mental retardation, and a variety of other permanent sequelae in children.  Early eye manifestations in infants are fairly characteristic. Cataract is the only eye sign that has a sensitivity high enough to be useful as a screening tool for CRS. CRS can be confirmed if a rubella immunoglobulin M (IgM) blood test is performed within the first 12 months of life.  Maternal rubella antibody should decrease by four to eight folds by 3 months of age.  Usually, half of those children with CRS lose IgM by the age of 12 months. 
Despite the introduction of an effective rubella vaccine in 1969, cases of CRS still continue to occur. Almost 25% of children born with CRS develop congenital cataract. WHO estimated that 100,000 children in the world are born with CRS each year.  Supportive care and surveillance are the cornerstone of management of CRS.  Prevention is the most important aspect of management by providing rubella vaccine to children, especially to girls.
In our country, Sudan, rubella vaccine has not yet been introduced in our national Expanded Program of Immunization (EPI). Also, there is no surveillance for CRS or rubella infection; so, this study was done with the aim to screen infants with congenital cataract attending eye clinics for the presence of rubella infection by testing their sera for IgM antibodies. This is the first study conducted in our country to determine the prevalence of CRS in infants with congenital cataract.
| Objectives|| |
Congenital cataract has a high sensitivity in detecting CRS in developing countries; so our objective was to screen infants with nontraumatic congenital cataract for rubella infection, then to determine the prevalence of CRS, and to assess the associated problems.
We anticipate that the results of this study will be useful in convincing the health authorities of our country to initiate rubella immunization program.
| Materials and Methods|| |
This is a prospective hospital-based study conducted at two eye hospitals in Khartoum, Khartoum, Sudan from March 15, 2011 to August 15, 2011. The studied group comprised infants, below 1 year of age, presenting with congenital cataract. A properly designed questionnaire was used for the collection of data. After registering the basic data and full medical history, general physical and ophthalmological examinations were done. After explanation and obtainment of informed consent, blood samples of the infants were taken and tested for the presence of specific IgM and immunoglobulin G (IgG) antibodies by the enzyme-linked immunosorbent assay (ELIZA) method. The presence of specific IgM antibodies or antibodies at titer >1.0% were considered positive.
The data were statistically analyzed using SPSS Version 18. Written approval was obtained from the administrative body of the hospitals and verbal consent was obtained from the parents.
| Results|| |
The number of studied infants with congenital cataract was 104, with the average age being 6.8 months. Of them, 52.8% were below 6 months of age. Male to female ratio was 1:1.1. Of the 104 infants, 14 (13.5%) were positive for rubella infection [Figure 1]. Male to female ratio in the positive cases was 1.3:1. Of these 14 positive infants, 13 (93%) were below 6 months of age [Figure 2]. This indicates that almost all the positive cases can be detected before the age of 6 months. Positivity for IgM antibodies was 28%, 20%, and 3.2% in infants below 3 months, between 3 months and 6 months, and above 6 months, respectively, [Table 1].
|Figure 1: Distribution of infants in the study as positive or negative for IgM|
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|Figure 2: Distribution of infants in the study who are positive for IgM according to age|
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|Table 1: Correlation between IgM positive infants for rubella virus and age of infants|
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None of the mothers of the studied infants received rubella vaccine and only two (14.3%) had a history of fever and skin rash during pregnancy. Thirteen (93%) positive infants had bilateral congenital cataract [Figure 3]. The head circumference and weight of 10 (71.4%) positive infants were below the third percentile for their age [Figure 4]. Six (42.8%) positive infants had congenital heart disease (CHD) in the form of ventricular septal defect (VSD) and patent ductus arteriosus (PDA). Three (28.6%) of them had hepatomegaly and one (7.1%) had hepatosplenomegaly.
|Figure 3: Presentation of IgM positive infants in the study as unilateral or bilateral congenital cataract|
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|Figure 4: Head circumference of infants with positive IgM to rubella virus|
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| Discussion|| |
Prevention of CRS has not received due attention in many developing countries. Rubella infection is still considered a significant health problem in countries where immunization programs are not successfully practiced. Not all infants with CRS have ocular manifestations; so, the sole use of these signs will underestimate the true incidence of CRS.  Cataract is the only eye sign that has a sensitivity high enough to be useful as a screening tool for CRS, detected by a study done by a group of researchers in 2007 about the prevalence of eye signs in CRS.  To the best of our knowledge, this is the first study conducted in our country about screening infants with congenital cataract for CRS. Surveys based only on clinical and serological diagnoses have been done in various parts of the world to estimate the prevalence of rubella-associated congenital cataract in children.  Serologic confirmation of CRS consists of demonstration of rubella-specific IgM antibody or infant IgG rubella antibody level that persists at a higher level and for a longer time than expected from passive transfer of maternal antibody. ,
The total number of infants studied was 104 with almost equal sex distribution and half of them below 6 months of age. Of the 104 infants, 14 (13.5%) were positive for rubella IgM and 13 (93%) of them were below 6 months of age. This means that detection of rubella infection is more likely during the first 6 months of life. Similar to our results, a study conducted by a group of researchers about the prevalence of eye signs in CRS stated that rubella-specific IgM was generally lost by 6 months of age.  A study done in South India in 1996 showed that 25% of cases of congenital cataract were hereditary and 15% were due to CRS, which is similar to our results.  In contrast, a study done in Saudi Arabia showed that only 2.2% of cases of congenital cataract were due to CRS; so, this lower incidence is due to the early introduction and availability of rubella vaccine in Saudi Arabia as part of childhood immunization program.  In the UK, a study done on 243 children with congenital cataract revealed prenatal rubella infection in only two cases (<1%).  This means that in developed countries, prevalence of CRS has been much reduced due to the already established effective immunization programs. CRS has been eradicated in the United States and in most European countries. 
Only 14.3% of the mothers of infants with positive IgM had a history of fever and skin rash during pregnancy, stressing the magnitude of subclinical infection in the etiology of CRS. None of the mothers received rubella vaccine, stressing its importance in preventing most cases of CRS. The weight of 71.4% of positive infants was below the third percentile for their age, indicating the effect of this congenital infection on growth leading to failure to thrive (FTT) as a late sequel. In this study, CRS mainly presented with bilateral cataract, stressing the generalized nature of this infection and its effects from early pregnancy. This is similar to the study done in India in 2002 by Vijayalakshmi et al. in which they reported bilateral congenital cataract as the clinical presentation in 88% of their cases.  This is explained by the fact that the virus enters the lens before the development of the capsule; so, the effect is always at the fetal nuclear level and frequently bilateral.
The head circumference of 71.4% of these infants with positive IgM for rubella infection was below the third percentile for their age, stressing the sequelae of small head size and microcephaly. Almost half of our positive infants had CHD. As a comparison, the study done in Oman by Rajiv et al. and in India by Vijayalakshmi et al. reported 38% and 50% incidence of CHD, respectively. , Gastrointestinal manifestation, in the form of hepatomegaly, was found only in 28% of our studied infants.
| Conclusion|| |
In conclusion, 13.5% of the studied infants were positive for rubella infection, indicating a significant prevalence rate. Of them, 93% were below 6 months of age, indicating that detection of this infection is highly possible early in life. So, taking the test as early as possible is recommended. We stress the significant role of subclinical infections that leads to CRS. Because none of the mothers in our study were vaccinated, introduction of rubella vaccination in our national immunization program is recommended. Proper surveillance and reporting of all the cases of CRS with urgent and long-term management programs are recommended. Finally, more studies on a larger scale are needed in our country to evaluate the different aspects of CRS.
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Satti Abdelrahim Satti
Associate Professor and Pediatric Consultant, University of Khartoum, Khartoum
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]