Surveillance of infectious intestinal disease in Malta

Abstract

The magnitude, distribution and burden of infectious intestinal disease (IID) in Malta is not adequately understood. The aim of this thesis was to estimate the frequency of IID at community level, identify where and how cases are lost along the surveillance chain and to assess the factors that influence notification at general practitioner and laboratory level. A cross-sectional telephone, survey interviewed over three thousand persons from the general population in Malta over a 21 month period. This study estimated a period prevalence of 3.18% in the 28 days prior to the interview and a rate of 0.421 (95% cr 0.092-0.771) episodes of IID per person per year. IID had a seasonal distribution with bimodal distribution. Females in the 31 to 44 year age group and males aged up to one year of age were the most commonly affected. Most of the episodes were mild and self-limiting, with an average duration of illness of 6.79 days. However 6% of the cases required hospitalisation. The majority of the burden from lID rests on health care-seeking costs followed by lost productivity. The total estimated average cost per case is LM 46 which, if extrapolated to the total expected number of cases in the general population, would cost over seven million Maltese lira per year. The commonest aetiological agent causing IID at community level is the norovirus. Sentinel surveillance by 22 general practitioners covered over 55 thousand patient-doctor encounters during the study period of eight months. This study estimated a period prevalence of2.02% (95% cr 1.90-2.14) of persons consulting their GP for IID. A postal survey and a focus group study on general practitioners and hospital physicians respectively identified the Disease Surveillance Unit web site and medical school training as the main source of provision of information. Accessibility to notification forms is an important requirement. Enhancement of the surveillance system by making laboratory-confirmed cases notifiable by laboratories alone may work for certain diseases but is not recommended for foodborne illnesses where urgent action is required. Laboratories need to inform doctors of their stool-testing protocols for the range of enteric pathogens. It may be worthwhile assessing the feasibility of automated transfer of data from laboratories to the national surveillance system. Feedback from the DSU is welcomed by laboratories, general practitioners and hospital physicians with the web site being the preferred mode. Campylobacter was targeted for the assessment of risk factors. A case control study of almost 100 cases and two controls per case, identified rare/raw or undercooked poultry as an independent risk factor for campylobacteriosis (OR 12; 95% Cl 1.44-99.67; p=0.021), whilst eating at restaurants; pork cutlets; beefburgers; yoghurt and cream filled cakes were found to be 'protective factors'. For children aged less than ten years, who made up almost half of the cases, consuming chicken (OR 23.92; 95% Cl 1.33-431.03; p=0.031) was an independent risk factor, whilst eating at a restaurant, eating pasta with minced meat, beef steak, eating yoghurt or soft ice-cream were found to be 'protective factors' . This is the first epidemiological study providing information on the burden of acute gastroenteritis in Malta which has highlighted important issues in the surveillance of lID Recommendations have been put forward to improve the surveillance and hence the control of lID, in Malta.