33. Bacterial and Viral Faeco-Oral Diseases Study Session 33 Bacterial and Viral Faeco-Oral Diseases 4



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33. Bacterial and Viral Faeco-Oral Diseases

Study Session 33  Bacterial and Viral Faeco-Oral Diseases 4

Introduction 4

Learning Outcomes for Study Session 33 4

33.1  Cholera 4

33.1.1  Infectious agents and occurrence of cholera 5

33.1.2  Cholera epidemics 5

Question 6

Answer 6


33.1.3  Symptoms and signs of cholera 6

Question 8

Answer 8

Question 8

Answer 8

33.2  Shigellosis (or bacillary dysentery) 8

33.2.1  Infectious agents and occurrence of shigellosis 9

33.2.2  Symptoms and signs of shigellosis 9

33.3  Rotavirus infection and other viral diarrhoeal diseases 9

33.4  Modes of transmission of diarrhoeal diseases 10

Question 10

Answer 10

33.5  Diagnosis, treatment and control of bacterial and viral diarrhoeal diseases 12

33.5.1  Diagnosis of diarrhoeal diseases 12

33.5.2  Treatment of bacterial and viral diarrhoeal diseases 13

33.6  Prevention and control of bacterial and viral diarrhoeal diseases 15

33.6.1  Controlling epidemics of diarrhoeal diseases 15

Question 15

Answer 15

Question 16

Answer 17

33.6.2  Epidemic control measures for cholera 17

33.6.3  Epidemic control measures for shigellosis 18

Question 18

Answer 18

33.6  Typhoid fever 19

Question 20

Answer 20

Summary of Study Session 33 22

Self-Assessment Questions (SAQs) for Study Session 33 23

SAQ 33.1 (tests Learning Outcomes 33.1, 31.2, 31.3 and 33.4) 23

Answer 23

SAQ 33.2 (tests Learning Outcomes 31.1, 33.4 and 33.5) 23

Answer 24

SAQ 33.3 (tests Learning Outcomes 33.2, 33.3 and 33.4) 24

Answer 24

SAQ 33.4 (tests Learning Outcomes 33.1, 33.2, 33.2, 33.4 and 33.5) 25

Answer 25


Study Session 33  Bacterial and Viral Faeco-Oral Diseases

Introduction


In the previous study session you learnt about the general features of faeco-oral diseases. With that introduction in mind, we will now discuss the common faeco-oral diseases caused by bacteria and viruses. In Study Session 34, you will learn about faeco-oral diseases caused by protozoa and intestinal worms. The conditions covered in this study session are divided into two groups: bacterial and viral faeco-oral diseases characterised by diarrhoea, and those characterised by high fever.

We begin with three diarrhoeal diseases: cholera, shigellosis and rotavirus infections. In each case, you will learn about their specific infectious agents, occurrence, modes of transmission, symptoms and signs. Then we remind you of the common features of the diagnosis and treatment, prevention and control of diarrhoeal diseases, which you already studied in general terms in Study Session 32. Finally, we describe the febrile illness, typhoid fever, which is also transmitted by the faeco-oral route. The focus of discussion in this study session will be on aspects that will be especially important to you in your daily work as a Health Extension Practitioner.


Learning Outcomes for Study Session 33


When you have studied this session, you should be able to:

33.1  Define and use correctly all of the key words printed in bold.


(SAQs 33.1, 33.2 and 33.4)

33.2  Describe the most common types of bacterial and viral faeco-oral diseases, their causative infectious agents and their occurrence in the population. (SAQs 33.1 and 33.3)

33.3  Describe the main modes of transmission of each of the bacterial and viral faeco-oral diseases, and the age groups that are most susceptible to them. (SAQs 33.3 and 33.4)

33.4  Explain how you would diagnose and treat cases of bacterial and viral faeco-oral diseases, and when and why you would refer them to a higher-level health facility. (SAQs 33.2 and 33.4)



33.5  Describe how you would apply prevention and control measures against bacterial and viral faeco-oral diseases, and what actions you would take to prevent epidemics of cholera or shigellosis. (SAQs 33.2 and 33.4)

33.1  Cholera


We begin by discussing cholera – its infectious agent, occurrence, symptoms and signs. Knowing about the nature of cholera will help you to diagnose, treat, prevent and control this disease, as described in Sections 33.5 and 33.6, together with measures against all the other bacterial and viral diarrhoeal diseases.

33.1.1  Infectious agents and occurrence of cholera


What comes to your mind when hear the word cholera? It is an acute diarrhoeal disease that affects the intestines and can kill vulnerable patients within a few hours if they are not treated quickly. The WHO estimates that there are 3 to 5 million cases of cholera every year around the world, and between 100,000 to 120,000 deaths. It can affect people in all age-groups. Cholera is caused by the bacteria named Vibrio cholerae (Figure 33.1), which occur naturally in the environment in shallow water around coasts, particularly where rivers flow into the sea. However, people infected by cholera bacteria can rapidly spread the organisms anywhere in a country, particularly where faeces leak into waste water collections.

Figure 33.1  Vibrio cholerae bacteria magnified thousands of times.


(Photo: Wikimedia Commons)

33.1.2  Cholera epidemics


Cholera can spread very easily from person to person, because even a few bacteria are enough to cause the disease if the person is already vulnerable, e.g. due to malnutrition or other infections. Although about 75% of people infected with the bacteria do not develop any symptoms, they can still pass on the infection in their faeces for up to two weeks, so epidemics can develop very quickly.

Question


Do you remember the definition of an epidemic? (Think back to Study Session 1 in Part 1 of this Module.)

Answer


An epidemic is defined as a sudden rise in the number of cases of a condition, which go on increasing for weeks or months before being brought under control; sometimes the numbers affected in an epidemic can continue rising for years (e.g. HIV/AIDS).

End of answer



There have been epidemics of cholera in Ethiopia; in 1970, several thousand deaths occurred in the eastern, central and southern regions of the country. Conditions leading to epidemics include the consumption of unsafe water, poor hygiene, poor sanitation and crowded living conditions. Cholera often follows after natural disasters involving flooding, and when large numbers of refugees live in camps (Figure 33.2). Consideration of these factors is important for the prevention and control of epidemics of cholera. In Section 35.2 of this study session, we mention the actions that should be taken to prevent a single case from leading to an epidemic. The details of epidemic investigations and management more generally are the subject of Study Session 42.

Figure 33.2  Cholera can spread quickly and cause epidemics in refugee camps, like this one in the Democratic Republic of the Congo.


(Photo: Ahu2, Wikimedia Commons)

33.1.3  Symptoms and signs of cholera


Knowledge of the typical symptoms and signs of cholera will help you to suspect cases and undertake further epidemic investigation measures. Cholera usually manifests after an incubation period of one to five days (i.e. the time between the bacteria entering the person’s body and the first symptoms appearing), but it can begin within a few hours after the infection. In about 80% of cases, the disease presents with relatively mild symptoms, but about 20% develop acute watery diarrhoea with severe sudden onset. The stools are painless and voluminous, with the appearance of water in which rice has been boiled (rice-water stools are a characteristic sign of cholera). The patient also experiences nausea, vomiting (Figure 33.3), fever and rapid progression to experiencing extreme weakness and shock. In such cases, death may occur within hours after the start of the illness.

Figure 33.3  Profuse vomiting and rice-water stools are characteristic symptoms of cholera.



Shock in cholera results from rapid dehydration and loss of essential salts in the voluminous diarrhoea and vomit. You learned about shock as a result of haemorrhage during and after childbirth in the Modules on Labour and Delivery Care and Postnatal Care. The signs are the same in shock due to severe dehydration caused by cholera.

Question


What are the typical signs of shock in an adult patient?

Answer


The typical signs of shock are systolic blood pressure dropping below
90 mmHg and/or diastolic blood pressure dropping below 60 mmHg, with a rapid pulse rate above 100 beats per minute. A person in shock will often appear confused and may lose consciousness. You must act quickly to save their life.

End of answer

If you see a person with the characteristic symptoms and signs of cholera, you must manage the patient immediately and begin effective control measures in the community (as described below in Sections 33.4 and 33.5). The risk of a cholera epidemic developing from a single case is high, so you must also undertake epidemic investigation and management procedures, which will be described for all epidemic conditions in Study Session 42.

Question


Suppose you were called to see an adult with acute watery diarrhoea and profuse vomiting of two days’ duration. What other evidence would suggest a diagnosis of cholera in this person?

Answer


In addition to the rapid onset and progression of the illness, the following symptoms and signs would support the diagnosis of cholera:

  • Painless diarrhoea and rice-water appearance of his stool

  • Fever

  • Extreme weakness

  • Shock (low blood pressure and rapid pulse rate)

  • Similar cases in the household or nearby.

End of answer




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