Kebaabetswe LP

INTRODUCTION

In developing countries, gastroenteritis is a common cause of death in children below five years. Viral pathogens constitute about half of the agents causing food borne diseases. Among these (as shown in figure 1, rotaviruses have been reported to be the single most etiological agents of severe diarrhea both in the developed and developing countries [1]. Poor nutrition and sanitary conditions predispose children in the developing countries to many other enteric agents such as toxigenic Escherichia coli and other bacteria. Malnutrition increases the severity of rotavirus infection [1]. It is estimated that as many as 500 000-870 000 deaths occur annually because of severe dehydrating diarrhea caused by human rotavirus in developing countries, with 150 000-200 000 deaths occurring in Africa [2].

Figure 1:

The role of etiological agents in severe diarrhoeal illness requiring hospitalisation of infants and young children in developed and developing countries [3].  

Transmission of Rotavirus

Rotavirus is transmitted via the faecal-oral route [4]. Infection is caused by ingestion of viral particles. Contamination of water or food is the main vehicle of transmission. Rotaviruses are extremely contagious and few particles are needed to transmit infection. The virus is easily transmissible because it can remain active on human hands for hours, on hard dry surfaces for 10 days and wet areas for weeks [5]. The ability of the virus to survive on various surfaces under different conditions may contribute to the rapid spread of these agents.

 Hand contact with ready-to-eat foods is an important route through which the virus may enter the food [6]. Food handlers may transmit the pathogen to foods from contaminated surfaces or another food, via contaminated hands.

Clinical Features of Rotavirus

 Rotavirus infection produces a spectrum of responses that vary from sub clinical infection to mild diarrhoea to a severe and occasionally fatal dehydrating illness in infants and young children [1]. The clinical features of rotaviruses are not distinguishable from other enteric infections and these may result in many cases of rotavirus going unnoticed. After an incubation period of 2-4 days, vomiting generally precedes diarrhoea, which lasts 5-7 days, accompanied by fever, abdominal pains and dehydration [7]. Death from rotavirus gastroenteritis may occur from dehydration and electrolyte imbalance.

 The Prevalence of Rotavirus

 Rotavirus epidemiology in sub-Saharan Africa appears to differ from that in the developed world in several ways, including earlier age of first and severe infection [8]. Studies conducted in developing countries, found that rotaviruses accounted for some 6% of all diarrhoeal episodes, a median of 28% of outpatient and 34% of hospitalisations for diarrhoea in young children [8, 9]. Several African countries have also reported the incidence of rotavirus, for example, Zambia (24%), Zimbabwe (32%), South Africa (16%) and Tunisia 17% [8, 10]. In a prospective study conducted in north Botswana, rotavirus was reported in 13% of children below 5 years [11]. The study further reported rotavirus infection to occur at an early age and virus shedding was predominantly observed in infants under 12 months of age; overall, over 80% of rotavirus occurred in children by the age of 24 months. This is also in line with the observation that 65-80% of children have antibodies to rotavirus by 12 months and 95% have been infected by 24 months [7]. The high incidence rates have been attributed to administration of contaminated weaning foods during the second year of life [12]. The incidence of clinical illness peaks at these ages where children are also at risk from severe disease associated with dehydration requiring hospitalisation [13]. Breastfed babies may be less likely to become infected because milk contains antibodies that fight the illness [14]. Children who have been infected once can be re-infected but recurrent infections are less severe than the first infections.

The virus is prevalent in day-care centres and causes nocosomal infections especially in paediatric hospitals where infection is characteristically asymptomatic in neonates [15]. Infections in adults are usually sub clinical but cause illness in parents of children with rotavirus diarrhoea.

At present there is no effective vaccine for rotavirus. Several varieties have been developed and none have been used in Africa. Diversity patterns in circulating antigenic types among different countries within the continent make it difficult to develop a common vaccine. The means of control of rotavirus diarrhoea at present include replacement of fluids and electrolyte lost through vomiting and diarrhoea. This is done by oral rehydration or intravenous therapy. Rice-based rehydration solutions have been shown to be effective in decreasing total output and increasing absorption and retention of fluids and electrolytes [1]. Apart from these, good hygiene and public health interventions could substantially reduce the impact of rotaviruses especially in developing countries. These could help decrease child mortality and improve child growth in many countries in Africa.

 ACKNOWLEGDEMENTS

I wish to extend my sincere gratitude to Prof. J. Allotey and my MSc research supervisors, Dr T.K Sebunya and Dr M.I Matsheka.

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