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UNIT 11 DISEASES CAUSED BY FAECAL CONTAMINATION

By Kevin Spencer,2014-05-06 09:09
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UNIT 11 DISEASES CAUSED BY FAECAL CONTAMINATION

    DIRECTORATE OF LEARNING SYSTEMS

DISTANCE EDUCATION PROGRAMME

    COMMUNICABLE DISEASES COURSE

    Unit 11

    Unit 5: Diseases of Faecal-oral Contamination

    Allan and Nesta

    Ferguson Trust

Unit 5: Diseases of Faecal-oral Contamination

A distance learning course of the Directorate of Learning Systems (AMREF)

? 2007 African Medical Research Foundation (AMREF)

This course is distributed under the Creative Common Attribution-Share Alike 3.0 license.

    Any part of this unit including the illustrations may be copied, reproduced or adapted to meet

    the needs of local health workers, for teaching purposes, provided proper citation is accorded

    AMREF. If you alter, transform, or build upon this work, you may distribute the resulting work

    only under the same, similar or a compatible license. AMREF would be grateful to learn how

    you are using this course and welcomes constructive comments and suggestions. Please

    address any correspondence to:

The African Medical and Research Foundation (AMREF)

    Directorate of Learning Systems

    P O Box 27691 00506, Nairobi, Kenya

    Tel: +254 (20) 6993000

    Fax: +254 (20) 609518

    Email: amreftraining@amrefhq.org

    Website: www.amref.org

Writer: Dr Peter Ngwatu

    Chief Editor: Anna Mwangi

    Cover design: Bruce Kynes

    Technical Co-ordinator: Joan Mutero

The African Medical Research Foundation (AMREF wishes to acknowledge the contributions

    of the Commonwealth of Learning (COL) and the Allan and Nesta Ferguson Trust whose

    financial assistance made the development of this course possible.

Contents

    INTRODUCTION .................................................................................................................................. 1 SPECIFIC OBJECTIVES ......................................................................................................................... 1 SECTION 1: OVERVIEW OF FAECAL - ORAL DISEASES ......................................................... 2 NATURAL DEFENCES ........................................................................................................................... 4 Gastric Acid ...................................................................................................................................... 5 Natural Bowel Motility ..................................................................................................................... 5 Normal Intestinal Bacterial Flora .................................................................................................... 5 CLINICAL PRESENTATION OF FAECAL-ORAL DISEASE ...................................................................... 5 DIAGNOSIS............................................................................................................................................ 6 TREATMENT ......................................................................................................................................... 6 Oral Rehydration Salts ..................................................................................................................... 7 PREVENTION AND CONTROL ............................................................................................................... 8 CHECK-POINTS FOR SOURCES OF WATER BORNE DISEASES ........................................................... 11 Kiosks and Food Shops................................................................................................................... 11 Hotels.............................................................................................................................................. 12 Private Homes ................................................................................................................................ 12 Irrigation Furrows .......................................................................................................................... 12 Health Facilities ............................................................................................................................. 13 SECTION 2: FAECAL-ORAL DISEASES CAUSED BY BACTERIAL INFECTION ............... 13 ACUTE GASTROENTERITIS ................................................................................................................ 13 Epidemiology .................................................................................................................................. 14 Management ................................................................................................................................... 15 Prevention and Control .................................................................................................................. 15 BACILLARY DYSENTERY ................................................................................................................... 16 Epidemiology .................................................................................................................................. 17 Pathology ........................................................................................................................................ 17 Clinical Picture .............................................................................................................................. 17 Diagnosis ........................................................................................................................................ 18 Management ................................................................................................................................... 18 Prevention and Control .................................................................................................................. 19 CAMPYLOBACTER JEJUNI INFECTIONS............................................................................................. 20 Pathology ........................................................................................................................................ 20 Clinical Picture .............................................................................................................................. 21 Diagnosis ........................................................................................................................................ 21 Management ................................................................................................................................... 21 Prevention and Control .................................................................................................................. 22 CHOLERA ........................................................................................................................................... 23 Epidemiology .................................................................................................................................. 23 Clinical Picture .............................................................................................................................. 25 MANAGEMENT ..................................................................................................................................... 25 Prevention and Control .................................................................................................................. 26 ENTERIC FEVER ................................................................................................................................. 29 Epidemiology .................................................................................................................................. 29 Clinical Picture .............................................................................................................................. 30 Diagnosis ........................................................................................................................................ 30 Management ................................................................................................................................... 31 Prevention and Control .................................................................................................................. 31 SECTION 3: FAECAL-ORAL DISEASES CAUSED BY PROTOZOAL INFECTION .............. 31 GIARDIASIS ........................................................................................................................................ 32 Pathology ........................................................................................................................................ 32 Clinical Picture .............................................................................................................................. 32 Diagnosis ........................................................................................................................................ 33 Management ................................................................................................................................... 33 Prevention and Control .................................................................................................................. 33 AMOEBIASIS ....................................................................................................................................... 33

    Pathology ........................................................................................................................................ 34 Clinical Picture .............................................................................................................................. 35 Diagnosis ........................................................................................................................................ 36 Extra-Intestinal Manifestations of Amoebiasis ............................................................................... 36 Diagnosis ........................................................................................................................................ 37 Management ................................................................................................................................... 38 Epidemiology .................................................................................................................................. 34Prevention and Control .................................................................................................................. 39 SECTION 4: FAECAL-ORAL DISEASES CAUSED BY TOXINS ............................................... 40 FOOD POISONING ............................................................................................................................... 41 Epidemiology .................................................................................................................................. 41 Clinical Picture .............................................................................................................................. 41 Management ................................................................................................................................... 42 Prevention and Control .................................................................................................................. 42 SECTION 5: FAECAL-ORAL DISEASES CAUSED BY VIRAL INFECTION .......................... 43 Clinical Picture .............................................................................................................................. 45 Management ................................................................................................................................... 46 Prevention and Control .................................................................................................................. 46 VIRAL HEPATITIS .............................................................................................................................. 48 Hepatitis A ...................................................................................................................................... 48 Hepatitis E ...................................................................................................................................... 50 ROTAVIRUS ........................................................................................................................................ 50 Clinical Picture .............................................................................................................................. 50 Diagnosis ........................................................................................................................................ 51 Management ................................................................................................................................... 51 Prevention and Control .................................................................................................................. 51 TUTOR MARKED ASSIGNMENT ............................................................... 错误!未定义书签。56

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ABBREVIATIONS

ALT Alanine aminotransferase

    AST Aspartate aminotransferase EBV Epstein-Barr virus

    HIV Human immunodeficiency virus

    Ig Immunoglobulin

    IPV Inactivated polio vaccine OPV Live attenuated orally administered polio vaccine

    ORS Oral re-hydration salts

    DMO District Medical Officer WHO Would Health Organization

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INTRODUCTION

Welcome to the eleventh unit of this course on communicable diseases. In the last three

    units, you learnt about vector borne as well as emerging and re-emerging diseases. More

    specifically, we focussed on their distribution, clinical manifestations, management and

    how to prevent and control infections in the community. In this unit, we shall discuss

    faecal-oral diseases that are of viral, bacterial and protozoal origin. We shall also look at diseases caused by toxins but will leave out those that are caused by worms as these will

    be covered in Unit 12 on helminthes.

    For each of the diseases, we shall study the epidemiology, clinical manifestations,

    diagnosis, treatment and how to prevent each one of them. As we go through this unit,

    you will realize that the concepts you learnt in the first unit of this course need to be at the back of your mind at all times, as many of them are applicable in this unit as well. Before

    we begin, let us go through the objectives of this unit.

Specific Objectives

By the end of this unit you should be able to:

    ? List the diseases acquired through the faecal-oral route;

    ? Describe the epidemiology of the faecal-oral transmitted diseases;

    ? Differentiate the clinical presentation for the various faecal-oral diseases;

    ? Make a diagnosis for the different faecal-oral transmitted diseases;

    ? Manage a patient with dehydration;

    ? Manage the different faecal-oral transmitted diseases;

    ? Discuss prevention and control of the diseases spread by the faecal-oral route.

    Let us start off with a general overview of faecal-oral diseases.

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Section 1: Overview of Faecal-Oral Diseases

    As the name suggests, faecal-oral diseases are diseases that occur when the causative organisms which are excreted in the stools of infected persons (or less commonly animals) gain entry into the human host via the mouth. Therefore, the organisms have to pass through the environment from the faeces of an infected person to the digestive system of a susceptible person. This is known as the faecal-oral transmission route.

    Faecal-oral transmission of organisms causing disease occurs mostly through faecal contamination of food, water, and hands which is not at all apparent. Very small amounts of faeces can carry enough organisms to establish infection. Seemingly sparkling clear water may be dangerously polluted. Contaminated food may smell, look and taste normal and yet harbour infective organisms. Clean-looking hands may carry and transmit enough micro-organisms to spread disease. The diagram below summarizes the faecal-oral transmission route.

Figure1: The faecal- oral transmission route

    As shown in Figure 1, food plays a central role in transmitting diseases because it can be directly or indirectly contaminated via polluted water, dirty hands, contaminated soil, flies, animals and animal products. Water can be polluted directly by faeces or faecal material may be washed into it from the polluted soil along river banks. The hands are usually contaminated after defecation or by touching contaminated objects.

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The house fly is very likely to carry faecal material because of its habit of starting a meal

    on faeces and finishing it off on human food. The fly can transfer organisms from faeces

    to food by carrying them on its body, by vomiting on solid food in order to liquefy the food

    and by defecating on food. The faeces and vomitus of the fly may contain viable infective

    organisms from human faeces.

    Take Note

    There are many diseases that are transmissible through faeces but not all of them

    are strictly faecal-oral in transmission. ?

    For instance, the polio virus may also be transmitted by droplet infection, especially during

    epidemics while anthrax which is caused by the bacterium Bacillus anthracis may also be transmitted by inhalation of spores and direct skin contact with infected hides. The eggs of

    intestinal worms are excreted in the faeces but the portal of entry for infections is not

    always the mouth. For example, Schistosoma mansoni is acquired through the skin.

    Food poisoning is not always due to faecal contamination but certainly belongs to the

    food-borne group of diseases. Many types of salmonella other than Salmonella typhi come from animals and can cause diarrhoea in humans, while Campylobacter from poultry can also be transmitted to humans. In these diseases infection is acquired by eating

    infected meat or eggs or from contaminated kitchen utensils and surfaces. Table 1 below

    shows the diseases acquired through the oral route.

    Table 1: Diseases acquired via oral route

    Viral Bacterial Protozoa Worms Toxins Polio Typhoid and Amoebiasis Ascariasis Botulism

    paratyphoid

    Hepatitis A, E Enterobiasis Giardiasis Staphylococcal

    Cholera food poisoning Viral diarrhoeas Trichuriasis such as rotavirus Bacillary dysentery Enterotoxigenic and adenovirus coli diarrhea Taeniasis

     Anthrax

    Hydatidosis

     Bacteria diarrhoeas

    such as Yersinia,

    Campylobacter, E. coli

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We shall discuss the diseases that are shown in Column 4 (worms) in the next Unit. Here

    we shall focus on the diseases that are shown in the other columns, that is, viral, bacterial,

    protozoa and toxins.

    The marked difference in the infectivity of these organisms is their susceptibility to lysis by

    gastric acid in the stomach.

    Take Note

    Gastric acid is capable of killing many organisms thus preventing infection in

    some cases. This natural defence mechanism is most effective against

    organisms such as Vibrio cholera and Salmonella typhi. ?

As a result, very large doses of vibrio cholera or salmonella typhi have to be ingested in

    order to cause disease. This makes accidental infection with typhoid or cholera by contact

    or contamination of food by flies very unlikely. Thus both diseases are almost exclusively

    water and food-borne.

    When only a very small number of organisms is required to cause infection, as in bacillary

    or amoebic dysentery, this is very easily done accidentally by the fingers or by

    contamination of food and eating utensils by flies. Indeed, usually there is an increase of

    dysentery cases during the season when flies are plentiful. Of course, infections through

    contaminated water occur as well. Contamination of fingers and eating utensils is most

    likely to occur when water for hand washing and cleaning is in short supply.

    Diarrhoeal diseases are often associated more with an inadequate supply of water than

    contamination of water and will usually disappear when the amount of water available is

    increased. It is the quantity rather than its quality which appears to be more important in

    relation to diarrhoeal disease transmission and control.

    Natural Defences

    Give 3 examples of natural defenses the body has against infection.

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Gastric Acid

    We already mentioned this first line of defence the gastric acid. Due to its acidic nature,

    the gastric acid prevents infections in some instances by killing ingested organisms

    through lysis. Natural Bowel Motility

    The natural bowel motility acts as a cleaning mechanism. Diarrhoea is usually

    accompanied by increased bowel movements and it can be regarded as a normal body

    response for flushing out harmful substances from the body. Thus it should not be

    surprising that suppression of bowel motility may be harmful in diarrhoeal diseases as you tend to hold the infective organism much longer in the digestive tract and this will lead to a delay in the recovery process.

    Normal Intestinal Bacterial Flora

    These bacteria form an important protective barrier against pathogenic bacteria. As long as they live and multiply in the bowel, pathogenic organisms have less chance of thriving. This is called bacterial competition. One way to predispose both animals and humans to

    bowel infection is to treat them with broad spectrum antibiotics which kill their normal intestinal flora.

    Clinical Presentation of Faecal-oral Disease

    Diarrhoea is the commonest manifestation for the majority of the faecal-oral diseases.

    Diarrhoea causes loss of body fluids, leading to dehydration. In mild dehydration the child presents with thirst and on physical examination will be alert or restless. However, with moderate to severe dehydration, the child may present with:

    ? Thirst, lethargy and irritability or even drowsiness;

    ? Rapid and weak pulse due to poor perfusion;

    ? Anterior fontanel sunken (it closes at about 18months of age). This reflects

    depletion in cerebrospinal fluid;

    ? Skin retracts slowly on being pinched due to decreased interstitial fluid;

    ? Sunken eyes, reflecting decreased vitreous humor;

    ? Mucus membranes are dry, reflecting reduced trans-cellular fluids;

    ? Urine flow is reduced;

    ? Poor capillary refill >2 seconds.

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