Diseases and Infections

Emerging Human Diseases: Transmission and

Prevention Emerging diseases are infections that have newly appeared in a population or have existed but are rapidly increasing in occurrence or geographic range. Examples of these diseases are SARS-COVID-19, Ebola, Buruli ulcer, Swine flu/H1N1 flu and Monkeypox. Emerging diseases are identified by the following characteristics:

a. They are either new or old diseases

b. The number of new cases recorded in the population (incidence) keeps increasing rapidly.

c. They spread to new geographic locations and populations.

d. They pose a huge threat to the public and can re-emerge after a period of decline.

Common Emerging Diseases

SARS (Severe Acute Respiratory Syndrome)

This is a serious respiratory illness that can lead to severe pneumonia and respiratory failure. It was first recorded in 2002 in Guangdong Province in China. Bats are believed to be natural reservoir hosts, suspected to be carrying the virus (bats are considered the vectors).

Figure 3.25: Electron micrograph of SARS-CoV Causative Organism: Coronavirus (SARS-CoV) Transmitted through;

a. respiratory droplets that are released when an infected person coughs or sneezes.

The virus in the droplets may be inhaled by other individuals nearby.

b. close person-to-person contact.

c. touching surfaces or objects contaminated with the virus and then touching the mouth, nose, or eyes.

Signs and symptoms include high fever, headaches, body pains, dry cough and shortness of breath.

Control and Preventive Measures

a. Wear a nose mask and personal protective equipment (PPE).

b. Practice good personal hygiene (such as handwashing).

c. Isolate infected persons.

d. Use vaccines.

e. Implement strong travel restrictions and screening protocols.

f. Quarantine suspected persons.

g. Educate the public.

Figure 3.26: Personal protective equipment (PPE) COVID-19 (Coronavirus Disease 2019) This is a respiratory disease that can have mild to severe forms. It was first identified in Wuhan, China, in December 2019. Bats are believed to be the natural reservoir and are considered to be vectors for the disease.

Causative Organism: SARS-CoV-2 (virus)

Transmitted through;

a. respiratory droplets that are released when an infected person coughs or sneezes.

The virus in the droplets may be inhaled by other individuals nearby.

b. touching surfaces or objects contaminated with the virus and then touching the mouth, nose, or eyes.

c. possible airborne transmission in enclosed spaces.

Signs and Symptoms include fevers, coughs, shortness of breath (difficulty in breathing), fatigue, headaches, sore throats and runny or stuffy nose.

Figure 3.27: Mild to severe symptoms of COVID-19 Control and Preventive Measures

a. Vaccination

b. Wear a mask in public places

c. Practise social distancing (at least six feet apart)

d. Frequent handwashing

e. Avoid touching face

f. Isolate suspected infected persons

g. Avoid going out as much as possible, especially when feeling sick

h. Quarantine suspected individuals

i. Educate the public about preventive measures

Figure 3.28: Preventive measures for COVID-19 Ebola Virus Disease This is a severe and deadly viral disease which causes widespread bleeding and organ failure among infected individuals. It was first recorded in 1976, in the now Democratic Republic of Congo (DR Congo). The virus is believed to have originated from fruit bats.

Causative organism: Ebola virus (family Filoviridae).

Figure 3.29: The Ebola virus Transmitted through;

a. direct contact with blood, body secretions, or other bodily fluids of infected persons

b. contact with contaminated objects, fomite (e.g., needles)

c. handling or consuming infected wild animals (e.g., fruit bats, monkeys) Signs and Symptoms include fever, vomiting, diarrhoea, abdominal pain, muscle and joint pain and bleeding.

Control and Preventive Measures

a. Wearing PPE such as masks, gloves and gowns.

b. Practice good personal hygiene such as handwashing.

c. Isolate infected persons.

d. Implement contact tracing strategies used to identify and monitor individuals who have been in close contact with someone diagnosed with the disease.

e. Use vaccines

f. Ensure safe burial of individuals who died from the disease.

g. Educate the public.

Buruli Ulcer

This is an infection caused by a slow-growing aerobic bacterium, which causes severe skin and bone tissue damage when left untreated. It occurs in tropical and sub-tropical regions of the world, especially in Africa, Australia and Southeast Asia. It is believed to be associated with stagnant waters.

The causative organism is Mycobacterium ulcerans

Figure 3.30: (left) hand affected by Buruli ulcer, (right) electron micrograph of the causative organism The exact mode of transmission is not fully understood, but possibly through contaminated water, soil, or insect bites (in aquatic environments).

Signs and symptoms include painless nodules or lumps under the skin, swelling of the affected area, skin lesions or plaque and destruction of the skin and underlying tissues.

Control and Preventive Measures

a. Early detection and treatment with antibiotics.

b. Wearing protective clothing (e.g. long sleeves, pants, etc.)

c. Avoid contact with contaminated water.

d. Ensure personal hygiene and improve wound care.

e. Educate people.

Swine Flu (H1N1 Influenza)

It is a type of respiratory illness that can range from mild forms to severe forms. It was first recorded in Mexico and the United States in 2009. The virus is believed to have been carried by pigs.

Causative organism: H1N1 influenza virus (a subtype of Influenza A) Transmitted through;

a. respiratory droplets that are released when an infected person coughs or sneezes.

The virus in the droplets may be inhaled by other individuals nearby.

b. touching surfaces or objects contaminated with the virus, i.e, fomite, and then touching the mouth, nose, or eyes.

c. Human-to-human contact is common Signs and Symptoms include fever, cough, sore throat, runny or stuffy nose, headaches, fatigue, muscle or body aches and chills (feeling cold).

Control and Preventive Measures

a. Vaccination.

b. Practice good hygiene such as handwashing.

c. Use a mask in public places.

d. Use prescribed antiviral medications.

e. Stay home when sick.

Monkeypox This is a viral disease that causes symptoms like smallpox. It was first identified in monkeys in 1958, primarily in Central Africa and West Africa. The virus is believed to be carried by rodents (which are vectors for this virus).

Causative organism: Monkeypox virus (a member of the Orthopoxvirus genus) Transmission

a. Close contact with infected individuals or animals.

b. Contact with body fluids, lesions, or contaminated materials (e.g., bedding).

c. Respiratory droplets during prolonged face-to-face contact.

Signs and Symptoms include fever, headache, muscle pains, back pain, swollen lymph nodes and rashes or skin lesions which progress from flat red spots to pus-filled blisters.

Control and Prevention Measures

a. Vaccination.

b. Avoid contact with infected animals (rodents and primates).

c. Wear PPE when caring for infected persons.

d. Practice good hygiene.

e. Isolate infected persons.

f. Educate the public about the disease and its consequences.

Activity 3.8 Scenario: Outbreak of “Phluokona Virus” Objective Create a plan for responding to a new infectious disease outbreak to gain a deeper understanding of disease transmission and public health response strategies.

Instructions

1. Read the fictional scenario about an outbreak of a new infectious disease carefully.

Scenario In the coastal town of Telwater, a new infectious disease known as Phluokona Virus has emerged. The virus was first identified in the latter part of the rainy season and has rapidly spread among the local population. Initially, reports indicated that Phluokona Virus causes flu-like symptoms, but it can lead to severe respiratory complications in vulnerable individuals. Other symptoms are fever, cough, fatigue, body aches and severe respiratory distress (in advanced cases).

The Phluokona virus is primarily thought to be transmitted through respiratory droplets when an infected person coughs or sneezes and through direct contact with contaminated surfaces. It is highly common in older adults (65 and older), individuals with pre-existing health conditions (e.g., asthma, hypertension) and young children under 5 years of age. As of now, there have been 150 confirmed cases in Telwater, with 20 hospitalisations. The local health department has initiated ‘contact tracing’ but is struggling to keep up with the rapid rise in cases.

There are reports of community panic, with many residents avoiding public places.

The assemblymen in the area have called for an emergency town hall meeting to discuss the outbreak and potential response measures. Local schools have been closed for three weeks as a precaution, and the health department is considering implementing a temporary quarantine for affected areas.

2. Organise into teams of 4-5 learners or as an individual and choose a role (e.g.

epidemiologist, public health official, communicator).

Ta sk for a group/individual

3. Consider the following as the (e.g. communicator)

a. Determining factors: justify if it is an emerging disease.

b. Surveillance: How will you track the spread of the virus and monitor new cases?

c. Containment Strategies: What actions will you take to prevent further transmission?

d. Public Communication: How will you inform the community about the outbreak and encourage preventive behaviour?

e. Resource Allocation: What resources (e.g., medical supplies, healthcare personnel) will you need to manage the outbreak effectively?

4. Outline your plan

5. Create and share a written document or presentation slide summarising your plan.

Plant diseases: control and prevention Blight diseases Blight is the general term for plant diseases caused by fungal or bacterial pathogens. These pathogens cause cell death (necrosis) in large areas of plants. Blight causes rapid and complete chlorosis (yellowing), browning and death of plant tissues like leaves, branches, twigs, or floral organs, completely damaging the plant. Common plants that are affected are potatoes, tomatoes, capsicum/bell peppers and eggplants. Different types of blight can affect edible and ornamental plants.

A table of blight diseases, causative organisms, plants and their parts affected, and symptoms is provided below.

Table 3.2: Blight diseases, causative organisms, plants and their parts affected, and symptoms.

Diseases Causative

organism Plants and their parts affected Symptoms Early/target spot blight Fungus:

Alternaria solani Tomatoes:

leaves, stem, flowers, potatoes:

leaves, Distorted, dark brown to black spots on the leaves with a distinct concentric ring pattern.

Halo blight Bacteria:

Pseudomonas savastanoi pv.

Phaseolicola Beans: leaves, pods, Brown spots with a light-green or yellow ring around spots Late blight Fungus:

Phytophthora infestans Potato: leaves Tomato:

leaves Rapid leaf rot.

Fire blight Bacteria:

Erwinia amylovora Apples and pears: flowers, stems and leaves Dark orange-brown (apples) or black (pears) patches or whole areas giving it a burnt appearance.

Figure 3.31: Late Blight disease on tomato plant Figure 3.32: Early blight disease on a leaf

Figure 3.33: Halo blight on bean leaves Figure 3.34: Fire blight on an apple tree Mode of Transmission of Blight The disease is transmitted through the air over long distances by the dispersal of the spores that are produced by the pathogen in moist and humid environments. The spread of these spores can be aided by:

a. water splash.

b. high humidity.

c. conducive temperatures.

d. human activities such as using contaminated tools or equipment.

e. humans moving between fields without proper sanitation.

Control and prevention Pathogens can stay in infested soil, old plant materials or on other ‘host’ plants, like nearby weeds, for up to a year. This makes it difficult to treat once the plants are affected. Some actions can be taken to prevent and control the disease.

a. Cultural Practices: Maintaining optimal growing conditions, removing (burning) infected plant parts, and crop rotation can help manage blight. Plant disease-free seeds and only save seeds from disease-free plants. Water the soil, avoid crown and root injuries, and feed plants regularly to keep them growing well – healthy plants can better resist pests and diseases.

b. Chemical control: Depending on the specific blight, fungicides can be used to protect healthy tissues from infection.

c. Other measures: Soil solarisation involves tightly covering the area of soil with clear plastic and letting the sun heat the soil for a couple of weeks to reduce the amount of fungus in the soil. After solarisation, reintroduce beneficial fungi and bacteria into the soil before planting.

Wilt diseases Wilt diseases are a group of plant diseases characterised by the wilting of leaves and stems, often leading to plant death. Wilt diseases are mainly caused by pathogens that infect the vascular system of plants and disrupt the transportation of water and nutrients.

A table of wilt diseases, causative organism, plants and their parts affected, and symptoms is provided below.

Table 3.3: Wilt diseases, causative organism, plants and their parts affected, and symptoms Wilt disease Causative organism Plants and their parts affected Symptoms Fusarium Wilt Fungus: Fusarium oxysporum Tomatoes (stems, leaves) Cotton (stems, roots), etc.

Wilting of leaves, often starting with the lower leaves Yellowing of leaves (chlorosis) Stunted growth Brown discolouration in vascular tissues when cut open Verticillium Wilt Fungus:

Verticillium dahliae Eggplants (stems, leaves) Strawberries (roots, stems), etc.

Wilting of leaves and stems Yellowing and browning of leaves Stunted growth Discolouration in the vascular system Bacterial Wilt Bacterium:

Ralstonia solanacearum Tomatoes (stems, roots) Potatoes (stems, tubers), etc.

Sudden wilting and collapse of plants Yellowing of leaves Brown discolouration in vascular tissues Water-soaked lesions on stems

Figure 3.35: Fusarium wilt in okra stem Figure 3.36: Verticillium wilt in eggplant Mode of transmission Conditions such as drought or poor drainage can increase the effects of wilt diseases, making plants more prone to infection and affecting crop yields and plant health. The disease is transmitted through:

a. contaminated soil

b. plant debris or infected plant parts

c. water

d. human activity, such as using contaminated tools Control and prevention Soilborne spores can stay in the soil for years and infect plants through the roots. Managing wilt diseases successfully is key to protecting crops and ensuring agricultural productivity.

Some measures can be taken to prevent and control the disease.

a. Cultural Practice

i. To reduce the pathogen load in the soil, practise crop rotation with non-host plants or plant varieties that are resistant to specific wilt diseases.

ii. Add organic matter to the soil to improve soil health and structure to promote beneficial microbial activity that can outcompete pathogens.

iii. Remove and destroy infected plant debris to prevent the spread of pathogens.

iv. Regularly clean tools and equipment to avoid contamination.

v. Avoid over-watering and ensure good drainage to reduce waterlogged conditions, which can enable fungal growth.

vi. Use drip irrigation to minimise leaf wetness.

b. Biological Control involves introducing beneficial bacteria and fungi that can suppress wilt pathogens. These microorganisms can help protect plants by outcompeting or directly inhibiting pathogens.

c. Chemical Control involves the use of fungicides and bactericides, treatments that carefully target specific pathogens.

d. Regularly monitor plants for early signs of wilt diseases to take early action to reduce the spread of the disease.

Activity 3.9 Plant Power: Awareness Campaign Extravaganza!

Objective: Design an awareness campaign for a plant disease (e.g., late blight, verticillium wilt) Materials: Art supplies, digital tools for creating posters, social media mock-ups, brochures Instructions

1. Research a selected plant disease, focusing on its impact and prevention strategies

2. Brainstorm for campaign ideas targeting a specific audience (e.g. farmers, gardeners)

3. Develop campaign materials (e.g. posters, brochures, social media posts)

4. Present your target audience and intended message.

5. Display the campaigns around the school or community to raise awareness.

Animal Disease: Control and Prevention

Brucellosis Brucellosis is a contagious disease in livestock caused by various bacteria of the genus Brucella. It is a zoonotic disease, which means it can be transmitted from animals to humans. In animals, it is characterised by abortions and reproductive failure. It can affect cattle, pigs, sheep, goats, camels, horses, and dogs. The specific causative organisms are B.

abortus (in cattle), B. melitensis (in sheep and goats) and B. suis (in pigs).

Mode of transmission

a. Brucellosis is mainly spread when the animal aborts or gives birth with high levels of the bacteria in the birth fluids.

b. The bacteria can also take over the udder and contaminate the milk.

c. The bacteria survive in cool, moist environments for several months and remain infectious to other animals that ingest them.

d. It infects animals and humans through cuts in the skin and mucous membranes.

Figure 3.37: Transmission of Brucellosis

Symptoms of infected animals

a. Show few signs until abortions, retention of placenta, stillbirth, birth of weak offspring or infertility occurs.

b. Skin lesions

c. Swelling of the testicles in males.

d. The bacteria are found in the joints, causing arthritis.

Symptoms in humans may include fever and chills, sweats, fatigue and discomfort, joint and muscle pain and headache.

Control and prevention

a. Vaccination is often used to reduce the occurrence of infection. Several vaccines are available that use modified live bacteria.

i. Vaccinate livestock (especially cattle, sheep, and goats) with appropriate vaccines (e.g. Brucella abortus strain 19 for cattle) to reduce the incidence of infection.

ii. Human vaccination is currently not available, but research is ongoing.

b. Hygiene and Sanitation

i. Implement strict hygiene practices on farms, including regular cleaning and disinfection of facilities and equipment.

ii. Use PPE like gloves, masks, and protective clothing when handling animals or animal products to prevent exposure.

c. Testing and Surveillance

i. Conduct routine testing of animals for early detection and treatment of Brucella infections.

ii. Isolate and treat infected animals to prevent the spread of the disease within herds.

iii. Implement controls on the movement of animals from infected areas to prevent transmission.

d. Public Awareness and Education

i. Educate farmers and livestock handlers about Brucellosis, its transmission, and prevention measures.

ii. Raise awareness in communities about the risks of consuming unpasteurised dairy (milk) products and the importance of reporting suspicious cases.

e. Food Safety Practices

i. Promote the pasteurisation of milk and dairy products to kill any potential bacteria.

ii. Practice safety protocols when handling and processing animal products, including thorough cooking of meat.

Tuberculosis Tuberculosis (TB) is a contagious disease caused by bacteria of the genus Mycobacterium, primarily Mycobacterium bovis in cattle and Mycobacterium avium in birds. It can also affect other animal species, including humans (Mycobacterium tuberculosis). It is a zoonotic disease because it can be transmitted from animals to humans (zoonosis) and from humans to animals (reverse zoonosis).

Mode of transmission TB is primarily spread through;

a. inhalation of airborne droplets from infected animals and humans

b. direct contact with infected tissues of humans and animals

c. consumption of milk and meat from infected animals.

Figure 3.38: Transmission of Tuberculosis

Symptoms

a. Cattle and pigs exhibit chronic cough, weight loss, fever, lethargy, and swollen lymph nodes.

b. Humans exhibit the following.

i. Cough lasting more than three weeks, sometimes with blood or sputum.

ii. Discomfort or pain in the chest with difficulty in breathing, especially when coughing.

iii. Unusual tiredness or weakness

iv. Low-grade fever that may come and go

v. Excessive sweating during the night, often soaking through clothing or sheets.

vi. Decreased desire to eat, leading to weight loss.

Control and Prevention

a. Regular testing and culling of infected animals.

b. Pasteurisation of milk and proper meat inspection.

c. Vaccination (e.g., BCG vaccine) in some regions, though not widely used in cattle.

d. Regular screening helps promote early detections and treatment.

e. Treatment requires completing the full course of prescribed antibiotics.

f. Use nose masks when infected to prevent and control its spread.

g. Educate the public about TB transmission, symptoms, and the importance of seeking care.

h. Address the issue of stigmatisation associated with TB to encourage individuals to seek testing and treatment.

Activity 3.10 Mission Control: Crafting a Disease Defence Strategy!

Objective: Create a comprehensive management plan for a chosen disease (e.g.

bacterial wilt, brucellosis).

Materials: Sample management plan template Disease Management Plan Template Disease Overview Disease Name:

Pathogen: (Bacterium, virus, fungus, etc.)

Host(s): (Plants/animals affected) Description: Brief description of the disease.

Symptoms Transmission

Modes of Transmission: (E.g., airborne, waterborne, direct contact, etc.)

Environmental Factors: (Conditions that promote transmission) Impact Economic Impact: (Cost to agriculture, livestock, etc.)

Ecological Impact: (Effects on ecosystems) Public Health Impact: (where needed) Current Management Practices Prevention Strategies: (E.g., sanitation, quarantine, resistant varieties) Control Measures: (E.g., chemical treatments, biological control) Proposed Management Plan Short-term Goals: (Immediate actions to take) Long-term Goals: (Sustainable practices to implement) Action Steps: (List specific actions required to achieve goals) Roles and Responsibilities: (Who will carry out each action?)

Monitoring and Evaluation

Monitoring Methods: (How will progress be tracked?)

Evaluation Criteria: (How will success be measured?)

Conclusion Summary of Key Points:

Final Recommendations:

References: (List of sources used for research)

Note: Search for relevant internet resources on case studies of learner’s choice.

Instructions

• Select one disease and research current management practices.

• Using the provided template, outline your management plan.

• Share your plan with a peer for review and provide constructive feedback for the work you reviewed.

• Revise the plan based on feedback

• Present the plan to the class.

Activity 3.11 Assessing Organism Health and Its Impact

Objective: To understand the health of specific organisms, the diseases that affect them, and the impacts on agriculture, the economy, and the nation.

Materials

• Paper and pencils

• Access to research materials (books, internet)

• Worksheets for data collection

• Chart paper for presentations Steps

1. Pick an organism that plays a big role in farming here in Ghana. It could be a crop like cocoa or maize, or livestock like cattle or domestic fowl.

2. Research into

a. what a healthy version of your chosen organism looks like.

b. what diseases can affect it?

c. what are the signs that something is wrong?

3. Think about how the health of your organism impacts:

a. Agriculture: How does it affect how much food we can grow?

b. Economy: What happens to farmers’ income and food prices?

c. Nation: Why is this important for food security and exports?

4. Gather information from surveys or find existing data to see how common these diseases are and their effects. (ask your teacher for existing data or use online sources)

5. Create some charts or graphs to show your findings.

6. Prepare a short presentation to share what you learned with the class. Include your research, the impacts, and any solutions you think could help improve organism health.