Understanding gastroenteritis in elderly Australians

Abstract

Elderly people are potentially at higher risk of gastroenteritis and foodborne diseases due to declining immunity, co-morbid illnesses and poorer food handling. In particular, residents of Long-Term Care Facilities (LTCF) have been highlighted as an 'at-risk' group, as outbreaks often occur in these facilities. The objectives of my research were to estimate the incidence of gastroenteritis and foodborne diseases in elderly Australians compared with other age groups, and elderly Australians living in LTCFs compared to elderly people in the community. I also examined the occurrence of outbreaks and causes of foodborne diseases in elderly people. To achieve these objectives I analyzed five different datasets: (1) a systematic review of gastroenteritis in LTCF residents, (2) 12-months longitudinal surveillance for gastroenteritis in residents of 16 LTCF in New South Wales, (3) two national surveys of gastroenteritis in the Australian community, (4)food- and waterborne infections in elderly people from Victorian public health surveillance, and (5) national surveillance of outbreaks of gastroenteritis and foodborne disease in Australian LTCF. I defined elderly people as 65 years or older. I analyzed datasets using meta-analysis, and negative binomial and logistic regression, depending on the nature of the data. In a meta-analysis of 15 international studies included in the systematic review, I estimated LTCF residents experience 0.15 episodes of gastroenteritis per person per year. Incidence was higher for studies conducted outside the United States at 0.27 episodes per person per year, which was similar to my findings of 0.23 episodes of diarrhea per person per year from longitudinal surveillance of 16 Australian LTCF. I estimated from national surveys that elderly people living in the community experienced 0.15 episodes of diarrhea per year, which was lower than any other age group. From Victorian surveillance data, the rate of Campylobacter infection in LTCF residents was 37!% lower than in community residents, after adjusting for age, gender and reporting period. However, Victorian LTCF residents were at higher risk of Salmonella infections, particularly in association with outbreaks. From longitudinal surveillance, 96% (245/254) of gastroenteritis episodes in LTCF residents were outbreak-associated. Analysis of 3,257 outbreaks of gastroenteritis that occurred in Australian LTCF over six years identified that 84,769 people were affected and facilities could expect one outbreak every three years. Outbreaks were predominantly transmitted from one infected person to another, with norovirus causing 35% (1,136/3,257) of outbreaks. Foodborne outbreaks were extremely rare and a food-vehicle was only identified in 27% (14/52) of outbreaks, where the main causes were meals that were pureed or contained eggs. In outbreaks of foodborne salmonellosis, 6.1% (15/244) of affected LTCF residents died. It was surprising to find that elderly people do not experience more gastroenteritis than younger people. Elderly people living in LTCF had a lower incidence of many foodborne infections than those living in the community, with the exception of salmonellosis. Gastroenteritis in LTCF residents was often associated with outbreaks, which were mainly spread from person-to-person. From these studies, health agencies should focus on identifying interventions to contain outbreaks of viral gastroenteritis in LTCF.