Poliomyelitis in Oman. I. The last outbreak?

Since 1988, the Sultanate of Oman has experienced three outbreaks of paralytic poliomyelitis. The last outbreak occurred in December 1993 and involved two children aged 10 months and 4 1/2 years. The children had received five and four doses, respectively, of trivalent oral polio vaccine (OPV) and lived in the same village. Serum neutralizing antibody tests suggested that paralytic polio in these children was due to poor antibody response to OPV. Wild poliovirus type 1 was isolated from both patients, as well as from seven of ten close contacts of the older child, and one of eight contacts of the younger child. All contacts had received three to six doses of OPV. Genomic sequence studies indicated that the virus isolates belonged to a genotypic group prevalent in southern and western Asia, but differed markedly from virus isolated during the 1988/89 outbreak, suggesting another importation of poliovirus. In response to the outbreak, supplementary immunization with OPV was given to children <6 years of age, initially in the affected district, and subsequently to children in the whole country. This study demonstrates that immunization with three to six doses of OPV did not prevent infection with wild poliovirus. In those children with sub-optimal response to OPV, infection resulted in paralytic poliomyelitis. The outbreak remained localized in one village, indicating that the outbreak control measures were effective.

Poliomyelitis in Oman. II. Toward eradication.

In the past decade, the Sultanate of Oman has experienced three outbreaks of paralytic poliomyelitis--a widespread polio type 1 epidemic in 1988/1989, four cases of polio type 3 in three different regions in 1991, and a localized type 1 outbreak in 1993. The lessons learnt from each of these epidemics have guided us to modify and improve our polio eradication activities. Currently, these activities include administration of five primary and three booster doses of trivalent oral polio vaccine, yearly national immunization campaigns (NIDs) since 1995 with coverage of >90%, localized immunization campaigns, acute flaccid paralysis (AFP) surveillance which involves reporting of all cases by facsimile to the Department of Surveillance within 24 h of detecting a case and weekly zero reporting from 22 sentinel sites, and virological testing of stool specimens of all AFP cases and their close contacts at the national, World Health Organization accredited laboratory. The cumulative success of these activities has resulted in Oman being free from polio for the past 6 years. However, the possibility of importation of wild poliovirus, particularly from southern and western Asia still exists.

Steroids in full term infants with respiratory failure and pulmonary hypertension due to meconium aspiration syndrome.

Persistent pulmonary hypertension of the newborn (PPHN) due to meconium aspiration syndrome (MAS), has a high morbidity and mortality especially in centres with limited access to extra-corporeal membrane oxygenation or nitric oxide therapy. In such a setting, we conducted a pilot study to evaluate the effect of dexamethasone on severe respiratory failure with PPHN due to MAS with a view to exploring possible justification for randomised controlled trials in similar patients. We prospectively managed a consecutive case series of 14 infants over a 3-year period with the above mentioned diagnosis, who were ventilated and with an oxygenation index >25. Dexamethasone was commenced in a dose of 0.5 mg/kg per day and given for up to a maximum of 9 days in a reducing schedule. Differences between time points were analysed using analysis of variance for repeated measures. The mean age of commencing dexamethasone was 79.9 h. There was a rapid, significant improvement (P < 0.05) in the respiratory status in 13 of these infants after commencing dexamethasone, allowing weaning from the ventilator and eventual extubation at a mean age of 8.7 days. One infant died. Two infants had infective episodes. Conclusion. Dexamethasone, if started early in infants with respiratory failure and persistent pulmonary hypertension of the newborn due to meconium aspiration syndrome may be effective in improving gas exchange, and possibly avoiding extra-corporeal membrane oxygenation. A randomised controlled trial of using dexamethasone early in similar patients and setting is warranted.

Effects of antenatal steroids on the complications of prematurity in an era of surfactant replacement therapy in Oman.

The aim of this study was to assess the effects of a complete course of antenatal steroids (dexamethasone 12 mg every 12 h x 2) on the complications of prematurity, in an era of surfactant replacement therapy in an Asian population. Between January 1995 and December 1998 we analysed all preterm births (-32 weeks) from women who had received antenatal care and delivered at our institution. Group A comprised those who did not receive, or received only an incomplete course of antenatal dexamethasone. Group B were those who received a complete course, i.e. delivered at least 24 h after commencing dexamethasone. There were 256 infants in Group A, and 168 in Group B. Mortality was significantly reduced (21.8 per cent in Group A vs. 10.7 per cent in Group B; p = 0.003), and the incidence of necrotising enterocolitis (NEC) was increased (2.7 per cent in Group A vs. 10.1 per cent in Group B;p = 0.001) in those whose mothers received dexamethasone. There was no difference in the incidence of respiratory distress syndrome (RDS), patent ductus arteriosus (PDA), chronic lung disease, major intraventricular hemorrhage (IVH) or PVL. There was, however, a trend towards an increased number of septic episodes in infants of Group B. It was concluded that antenatal steroids reduced mortality, but had no effect on the incidence of RDS, PDA, CLD, major IVH or PVL in an Asian population who were given surfactant for respiratory distress syndrome. There was a trend towards greater neonatal infections. These results need to be confirmed in similar population groups.

Incidence and spectrum of congenital heart disease in Oman.

We analysed the incidence and spectrum of congenital heart disease (CHD) in the Sultanate of Oman from 1994 to 1996. CHD was detected in 992 of 139,707 live births (incidence 7.1/1000 live births). The common CHDs were ventricular septal defect (24.9%), atrial septal defect (14.4%) and patent ductus arteriosus (10.3%). The frequency of atrioventricular septal defects (5.9%) was higher than reported from other countries. Age at diagnosis was under 1 month in 38% and 1-12 months in 40%. Cyanotic CHD was found in 21.7% of the whole group and 35% of neonates. Although this was a hospital-based study, we believe we included almost all the infants and children with CHD in the country. The incidence and pattern of CHD in Oman were similar to those reported from developed countries in Europe and America, except for a higher frequency of atrioventricular septal defects. The high prevalence of consanguinity in the country did not affect the overall incidence of CHD.

External hydrocephalus in primary hypomagnesaemia: a new finding.

This paper reports a new finding in two siblings with primary hypomagnesaemia as a result of renal magnesium wasting, namely, rapidly increasing head size. External hydrocephalus and brain shrinkage in primary hypomagnesaemia seen on computed tomography of the brain with reversibility after magnesium treatment has not been reported previously.

Comparative trial of artificial and natural surfactants in the treatment of respiratory distress syndrome of prematurity: experiences in a developing country.

We conducted a randomized clinical trial to compare the effects of a synthetic (Exosurf) and natural (Survanta) surfactant in infants with neonatal respiratory distress syndrome. Eighty-nine patients were randomly allocated to receive one of the two surfactants. Primary outcome variables were the acute and long-term effects of the surfactant preparations, i.e., ventilatory requirements at 24 h of age as judged by the oxygenation index (OI), and the combined incidence of chronic lung disease or death at 28 days. The OIs in the Exosurf and Survanta groups at 24 h were the same (10.1 and 7, respectively; P > 0.05). The magnitude and rapidity of response, however, were greater for Survanta than for Exosurf. When arterial/alveolar oxygen tension ratios (a/A) were compared, the Exosurf group had a significantly worse a/A ratio at 24 h than the Survanta group (0.21 Exosurf vs. 0.37 Survanta; P < 0.05). The long-term outcome as judged by the combined incidence of death or chronic lung disease was not different in the two groups (18.6% Exosurf vs. 15.2% Survanta; P > 0.05). When the complications of prematurity were compared, there were no statistically significant differences between the two groups. We conclude that both preparations are reasonable choices for the treatment of respiratory distress syndrome of prematurity.

PIP: This study compares the effects of synthetic (Exosurf) and natural (Survanta) surfactants on infants with neonatal respiratory distress syndrome in Oman. Subjects included 89 patients, randomly allocated to receive one of the two surfactants. Results suggest that 43 and 46 of the total infants enrolled in the study were randomized to the Exosurf and Survanta groups, respectively. The oxygenation index in the Exosurf and Survanta groups at 24 hours were the same (10.1 and 7, respectively; P 0.05). The magnitude and rapidity of response, however, were greater for Survanta than for Exosurf. Moreover, when arterial/alveolar oxygen tension ratios (a/A) were compared, the Exosurf group had a significantly worse a/A ratio at 24 hours than the Survanta group. There were no statistically significant differences between the two groups when the complications of prematurity were compared. In conclusion, both preparations offer reasonable choices in the treatment of the respiratory distress syndrome. However, this should be weighed against the minor theoretical risks of transmission of infectious agents in a natural preparation, and the easier storage and transport of the synthetic surfactant.