[Results of active surveillance of acute flaccid paralysis in the Central African Republic and Chad from 1995 to 2000]. / Bilan de la surveillance active des paralysies flasques aigues en Republique Centrafricaine et au Tchad de 1995 a 2000.

The threefold purpose of this report is to describe the epidemiology of acute flaccid paralysis (AFP), to determine the impact of the National Immunization Days (NID), and evaluate the quality of active surveillance in the Central African Republic (CAR) and Chad. The data in this study was obtained from the Enterovirus Division of the Pastear Institute in Bangui (National WHO Inter-country Reference Laboratory for the CAR and Chad and Regional Poliovirus Reference Laboratory in Africa). An increase in the number of AFP cases was observed in the CAR between 1995 and 2000 and in Chad between 1997 and 2000, mainly as a result of enhancement of the surveillance system. The goals set by the WHO in terms of the proportion of AFP cases with 2 specimens collected within 14 days of onset of paralysis and the number of cases with 60-day follow-up have not been reached in either country. The presence of 2 strains of wild poliovirus (types 1 and 3) and several genotypes (West African 13 and West African 7 for type 1 and Central African and Nigeria-P3 for type 3) not only show that Central Africa is still a significant reservoir for poliovirus transmission but also raise serious doubts about the quality of the NID organized over the last 3 years. The priority of the next NID round must be to reach unimmunized children who have been missed by routine immunization coverage.

[Circulation of the poliovirus in endemic zones with children vaccinated by the oral polio vaccine]. / Circulation des poliovirus dans les zones d'endémie chez les enfants vaccinés par le vaccin polio oral.

Strategies aiming to eradicate the poliovirus and poliomyelitis seek primarily to eliminate wild strains associated with the disease, by means of world wide vaccination campaigns using the oral attenuated vaccine (OPV). OPV contains attenuated viral strains which retain their replicating capacity in the digestive tract and thus induce the development of an antiviral local intestinal immunity and limit the circulation of the virus. In such a context, poliomyelitis surveillance laboratories should study above all cases of acute flaccid paralysis (AFP), highlighting the circulation of wild strains, identifying regional reservoirs and guiding vaccination strategies. Alongside circulation, there appear to be important genetic and phenotypic shifts in vaccinating strains, since the OPV is capable of preserving a reservoir of pathogenic stains and thereby impairing vaccination efficacy and the eradication of the virus. Furthermore, non-polio enteroviruses should be considered as a source of emerging pathogenic strains. These questions are being studied by the Pasteur Institute with the objective of determining the effects of OPV campaigns on the circulation of the poliovirus. We have studied the poliovirus vaccine and the circulation of wild strains in urban and peripheral urban areas in African countries known to be endemic for poliomyelitis (Central African Republic, Madagascar, Côte d'Ivoire). The study population consisted of children who had already been vaccinated and new-borns in the course of vaccination. We also evaluated the diffusion of the vaccine strains in their immediate environment. Genetic interchanges were taken into account. For children who received the 3-4 OPV doses, asymptomatic virus excretion was insignificant (0.4-2.4%). The rate of virus excretion in the surrounding environment of children in the course of being vaccinated was relatively low (1.76-5.3%). Our study also detected variant and recombinant strains.

The molecular epidemiology of type 1 poliovirus in Central African Republic.

An increase in the incidence of acute flaccid paralysis cases associated with wild-type 1 poliovirus occurred in children in the city of Bangui, Central African Republic (CAR), in 1993 and 1994. Genetic relationships of 33 isolates were analysed by restriction fragment length polymorphism and by sequencing the VP1/2A junction region (150 nucleotides) of the viral genome. Two distinct genotypes, A and B, were co-circulating in 1993, while in 1994 only a third genotype, C, was observed. Comparison of the sequences found, with those of the sequences from isolates from neighbouring and other endemic countries revealed that genotype A isolates were related to strains from Egypt (90.7% identity), genotype B isolates to strains from Kenya (96.7% identity), Sudan and Egypt, and genotype C isolates to strains from various countries in western and southern Africa (89.0% identity). Genotypic diversity and genetic linkage with strains from neighbouring countries indicate intense poliovirus circulation and transmission that does not respect national borders. Therefore, eradication of poliomyelitis from CAR can only be achieved by a coordinated multinational strategy that stops poliovirus circulation in the whole of Africa.

A cohort study of enteric campylobacter infection in children from birth to two years in Bangui (Central African Republic).

A cohort of 111 children from Bangui, Central African Republic, was followed for enteric campylobacter infection from birth until the age of 2 years. Stools were examined at each episode of diarrhoea, and bi-weekly up to the age of 6 months irrespective of the presence of diarrhoea. 349 episodes of diarrhoeal illness were recorded (1.6 per child-year). Campylobacters were isolated from 41 (11.7%) of the 349 episodes, but in half of them another enteric pathogen was also isolated. Campylobacters were statistically associated with diarrhoea only before the age of 6 months. Bi-weekly sampling up to this age detected 75 infections (1.3 per child-year), yet only 12 (16%) were associated with diarrhoea. Campylobacter coli was isolated slightly more often (51%) than C jejuni (49%); biotyping and serogrouping showed that no strain was especially associated with disease. Fewer children who had campylobacter infection before the age of 6 months suffered campylobacter diarrhoea between 6 and 24 months of age than those who did not, but the difference did not reach statistical significance. A significantly higher rate of isolation was found in the homes of infected children (human and animal contacts) than of non-infected children. Campylobacter infections were statistically associated with the presence of live poultry and the lack of piped water in homes.

Biotype and Lior serogroup distribution of enteric Campylobacter isolated from children in Bangui (Central African Republic), and comparison with Penner serotypes.

The new extended biotyping scheme of Lior as well as the slide agglutination technique were applied to 209 strains of enteric Campylobacter isolated from children in Bangui (Central African Republic). Three biotypes of C. jejuni and 2 biotypes of C. coli were identified among the strains; 31.1% were C. jejuni I, 11% C. jejuni II, 2.4% C. jejuni III, 44% C. coli I and 11.5% C. coli II. We were able to serotype 71.3% of the strains with 20 immune sera prepared against strains of Campylobacter isolated previously; 63% of the strains were distributed among the ten most common serogroups. No significant difference was observed in the distribution of biotypes or serogroups between strains from healthy and diarrhoeic children. Comparison of Lior serogroups with Penner serotypes showed that different Penner serotypes may correspond to a Lior serogroup and vice versa.

Prospective longitudinal study of rotavirus infections in children from birth to two years of age in Central Africa.

A cohort of 111 children born in Bangui (Central African Republic) was followed from birth to two years of age for rotavirus infections by biweekly stool investigations until six months of age, as well as at each diarrhoeic episode. Thirty-eight children (34.2%) exhibited at least one rotavirus infection by the age of 6 months. Thirty children (27%) presented with rotavirus-associated diarrhoea before 2 years of age. Until the children reached the age of 12 months, rotavirus was identified significantly more frequently in diarrhoeic stools than in non-diarrhoeic stools (p less than 0.001). A low diversity of characterized rotavirus strains was found; only two electrophoretypes were identified, and 91% of the strains belonged to subgroup II, serotype 1, with no special strain identified in newborns. A total of 38 children had a rotavirus infection before the age of six months, while 73 did not: only 2.6% of the first group had diarrhoea associated with rotavirus between 6 and 24 months, versus 20.5% in the second group (p less than 0.05). In two-thirds of the cases of infection, the presence of rotavirus in stools was detected only once; repetitive isolations were more frequent in diarrhoeic than in asymptomatic infections. The isolation rate of rotavirus in the general populations was found to be very low (0.2%).

Prospective study of enteric Campylobacter infections in children from birth to 6 months in the Central African Republic.

A survey of enteric Campylobacter infections was performed in Bangui, Central African Republic, with a cohort of 127 children from birth to 6 months of age by biweekly culture of stools; 82 infections were observed, and 41.7% of the children presented at least 1 infection before 6 months of age. Only 15.9% of the infected children had a diarrheic syndrome; moreover, 61.5% of these diarrheic children had another enteropathogen associated with Campylobacter species. In about half the cases, Campylobacter spp. were excreted for more than 4 days. More than half of the children had at least one diarrheic episode, for which an enteropathogen was identified in one third of the cases, before 6 months of age.

PIP: Prospective surveillance of enteric Campylobacter infection from birth to 6 months of age was carried out in a cohort of infants delivered in a maternity ward in the Central African Republic city of Bangui. The purpose of the study was to define the factors explaining the existence of a large number of healthy carriers of enteric Campylobacter species in this region. 82 infections were observed in the cohort of 127 infants; 42% of the children presented with at least 1 infection before 6 months of age. Only 16% of the infected children had a diarrheic syndrome; moreover, 62% of these diarrheic children had another enteropathogen associated with Campylobacter infection. The median duration of prolonged elimination of the Campylobacter germ was 7-8 days in both asymptomatic and diarrheic infants. Isolation rates of Campylobacter were highest among children who were exclusively breastfed. 4 infants were infected with Campylobacter by the 3rd day of life and 11 were infected by 1 month of age. The number of observed infections was significantly higher in the 3-6 month age group than between 4-6 months of age. The early age and frequency of contact of children with Campylobacter species may explain the large number of healthy carriers observed among children 6-24 months of age in a previous etiologic investigation.