Sabin and wild polioviruses from apparently healthy primary school children in northeastern Nigeria.

Despite significant success of the Global Polio Eradication Initiative (GPEI) in Nigeria, Afghanistan, India, Pakistan, wild poliovirus still occurs due to persistently high proportions of under and unimmunized children. The study aimed at determining the type of poliovirus often excreted into the environment. Four hundred nine fecal samples collected from apparently healthy school children aged 5-16 years in Borno and Adamawa States, northeastern Nigeria, were tested for poliovirus by tissue culture technique. The isolates were characterized further by intratypic differentiation testing and genetic sequencing. Three wild poliovirus type, 11 Sabin type, combination of Sabin-types 1 + 2 and 2 + 3 poliovirus, and 22 non-polio enteroviruses were obtained. The continued excretion of wild-type poliovirus among children above 5 years old vaccinated with oral polio vaccine contributes to the persistent circulation of these viruses in the environment and may limit the population immunity. However, the excreted Sabin poliovirus is capable of immunizing the unvaccinated children and promotes herd immunity. Similarly, the excretion of combination of two polio serotypes indicates the child susceptibility to the missing serotype (s) and therefore indicates an immunity gap. The common unhygienic practices in the environment could aid the spread of these viruses through oral-fecal route. Asymptomatic transmission of wild poliovirus among older oral polio vaccine-vaccinated children poses a serious threat to polio eradication program in Nigeria and therefore, environmental and serological surveillance with larger sample size are important for monitoring poliovirus circulation in Nigeria.

A survey for neutralizing antibodies to the three types of poliovirus among children in Maiduguri, Nigeria.

The milestone in polio eradication program is to protect effectively children aged 0-5 years against the three serotypes of poliovirus. It became necessary to measure the level of neutralizing antibodies to the three poliovirus types in an endemic State in Nigeria. Neutralizing antibodies to the poliovirus types among children aged 0-5 years was estimated using micro neutralization assay. Of 129 children, 99 (76.8%), 95 (73.6%), and 95 (73.6%) had neutralizing antibodies with the geometric mean titer of 42.7, 31.3, and 33.2 for the poliovirus type 1, 2, and 3, respectively. Fifty-three percent of the children were protected against the three types of poliovirus. Combination of poliovirus types 1 and 2, 1 and 3, and 2 and 3 were neutralized by 62.8, 58.9, and 61.2% of the children studied, respectively. Only poliovirus type 1 induced antibody titres ≥1:1,024. The number of children with neutralizing antibodies after receiving three doses was significantly higher than those who received one or two doses of oral polio vaccine (P ≤ 0.05). However, those who received more than three doses of oral polio vaccine showed no significant difference in their antibody response. The existence of immunity gap poses a risk of re-emergence of the paralytic poliovirus. The existence of unimmunized and unprotected children along with high birth rate could impede the success of polio vaccination in Nigeria. Elimination of non-compliance to polio vaccine, promotion of health education and documented evidence of vaccination of each child with the parents may facilitate the success of polio eradication program in Nigeria.

Multiple novel astrovirus species in human stool.

Diarrhoea remains a significant cause of morbidity and mortality in developing countries where numerous cases remain without identified aetiology. Astroviruses are a recently identified cause of animal gastroenteritis which currently includes two species suspected of causing human diarrhoea. Using pan-astrovirus RT-PCR, we analysed human stool samples from different continents for astrovirus-related RNA sequences. We identified variants of the two known human astrovirus species plus, based on genetic distance criteria, three novel astrovirus species all distantly related to mink and ovine astroviruses, which we provisionally named HMOAstV species A-C. The complete genome of species A displayed all the conserved characteristics of mammalian astroviruses. Each of the now three groups of astroviruses found in human stool (HAstV, AstV-MLB and HMOAstV) were more closely related to animal astroviruses than to each other, indicating that human astroviruses may periodically emerge from zoonotic transmissions. Based on the pathogenic impact of their closest phylogenetic relatives in animals, further investigations of the role of HMOAstV, so far detected in Nigeria, Nepal and Pakistan, in human gastroenteritis are warranted.