HUMAN AND HARMFUL MICROBES

Objectives

The student will be able to:
Explain the term microbes and classify them.
Name some diseases caused by microbes.
Describe the mode of transmission, symptoms, control and prevention of some diseases caused by microbes.
Explain the terms immunization, vaccination and inoculation, and show how they are related.
Classify immunity.
State the importance of immunization.

Microorganism

A microorganism or microbe is a microscopic organism, which may be a single cell or multicellular organism. Microorganisms are found everywhere in nature; in the soil, water, air, hot springs, deep inside rocks, in and on other living organisms. They include bacteria, protozoa, fungi, algae and viruses. Microorganisms can be harmless, beneficial or pathogenic.

· A pathogen is a micro-organism that has the potential to cause disease.

· An infection is the invasion and multiplication of pathogens in an individual or population.

· Vector is an animal that transmits disease-causing organisms from one organism to another.

· Disease is when the infection causes damage to the individual’s vital functions or systems. An infection does not always result in disease.

Main groups of diseases

o Communicable or Infectious diseases: these are disease which cause by pathogens through agents or vectors that transmitted from one person to another.

o Non-communicable diseases: they are not caused by pathogens and cannot be transmitted from one individual to another. E.g., ageing diseases, deficiency diseases, mental illness, genetic and human induce diseases.

To cause an infection, microbes must enter the bodies. The site at which they enter is known as the portal of entry. Microbes can enter the body through the following sites:

v Respiratory tract (mouth and nose): droplet infection e.g., Influenza virus

v Gastrointestinal tract (mouth oral cavity): intake of contaminated food or water e.g., Vibrio cholerae

v Urogenital tract: contact with infected person e.g., Escherichia coli which causes cystitis

v Breaks in the skin surface (cut or wounds): by contact with a vector e.g., Clostridium tetani

Useful Microbes

Some ways by which microorganisms are beneficial to man and other organisms are

Ø Digestion: some bacteria digest cellulose in the large intestine of some herbivores.

Ø Food: microorganisms are used in brewing, winemaking, baking and other food-making processes. They are also used to control the fermentation process in the production of dairy products such as yogurt and cheese. Some microorganisms serve as source of food e.g., mushroom, and truffles.

Ø Energy: microbes are used in fermentation to produce ethanol, and in biogas reactors to produce methane.

Ø Production of chemicals, enzymes: microbes are used for commercial and industrial production of chemicals, enzymes, antibodies and other bioactive molecules.

Ø Nitrogen-fixation: they help increase soil fertility by fixing nitrogen into the soil. E.g., azortobacter in soil and rhizobium living in nodules of leguminous plants.

Ø Nutrient recycle: most microbes are decomposers and help to recycle nutrients.

Ø Synthesis: genetically engineered bacteria are used to produce insulin and growth hormones. Some microbes also synthesize Vitamin B₁₂ and Vitamin K in human gut.

Ø Sewage treatment: microbes are mixed with polluted water or sewage, where they decompose the organic material in pollutants and, in the process, detoxify them.

Harmful Microbes

These are microbes which adversely affect man and other living organisms. They are the cause of many infections or contagious disease some of which may be very fatal. Pathogenic microbes are commonly referred to as ‘germs. Pathogens gain entrance to the body through cut, wounds, inhalation, intake of contaminated food or water or through a bite of vector.

Diseases Caused by Microbes in Human

Measles

Measles is a highly infectious illness caused by a virus. The virus lives in the mucus of the nose and throat of people with this infection. It’s one of the six killer disease in children.

Mode of transmission

Ø Through droplet infection

Ø By putting infected fingers in mouth, nose or rubbing the eyes

Symptoms

o Fever

○ Dry cough

o Running nose

○ Sore throat

o fever and skin rashes

○ Muscle pain

o Inflamed eyes (conjunctivitis)

o Tiny white spots inside the mouth

Prevention: Vaccination

Poliomyelitis

Polio is a highly contagious infection caused by the polio virus. Polio is also called poliomyelitis. This is one the six killer diseases in children.

Mode of transmission

o Droplets infection

o Through contaminated food and water

Symptoms

§ Slight fever

▪ Paralysis

§ Sore throat,

▪ Vomiting,

§ stiff neck and back, and deep muscle pain

Prevention/Control

¨ Vaccination

♦ Treated water supply

¨ Hygienic food preparation

Rabies

It is a disease human may get from being bitten by an infected animal (cat and dog) with the rabies virus. The rabies virus affects the central nervous system including the brain and spinal cord of humans and animals.

Symptoms and Signs

· Fevers

● muscle weakness

· Insomnia

● Anxiety

· Partial paralysis

● Excess salivation

· Pain, burning or itching at the bite site

Prevention

Ø Vaccinate pets

Ø Keep pets from roaming outside

Ø Report stray animals to animal control.

Influenza

Influenza (also known as the flu) is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death.

Mode of transmission

Ø Through coughing or sneezing from infected person

Ø Inserting infected fingers in the mouth, nose or rubbing the eyes

Symptoms

· Fever and chills

● Headache

· Fatigue,

· Cough, sore throat, runny or stuffy nose

· Diarrhea and vomiting (among children)

· Complications include: pneumonia, ear infections and dehydration.

Prevention and control

o flu vaccination

o Thorough and frequent hand-washing with soap or use alcohol-based sanitizers

o Cover the mouth and nose when sneeze or cough

Hepatitis B

Hepatitis is an infection of the liver. The group of viruses that infect the liver are called hepatitis viruses. Some types of hepatitis can cause very serious diseases and in extreme cases may lead to death.

Mode of transmission

¨ transmitted through sexually intercourse

¨ having unprotected oral sex

¨ through blood transfusion

¨ Contaminated food and water

Symptoms

· fever

● dark urine

● loss of appetite

· nausea, and vomiting

● abdominal pain

· unusually light-colored stool

· jaundice (yellowing of skin or eyes)

· Frequently there will be no symptoms, and it is only discovered in a blood test

Prevention

Ø Abstain from sexual intercourse.

Ø Hepatitis B vaccine

Ø blood should be screened before blood transfusions

Ø Avoid sharing items such as razors or toothbrushes

Ø Drinking water should be treated to destroy any virus

HIV/AIDS

Acquired immunodeficiency syndrome (AIDS) is a sexual transmitted disease. It is viral disease caused by HIV. HIV (human immunodeficiency virus) is a group of viruses known as retroviruses. The virus kills or damages cells of the immune system and progressively destroys the body's ability to fight infections and certain cancers.

Mode of transmission

Ø Using contaminated injection needles

Ø Through sexual intercourse with infected person

Ø Through transfusion of infected blood

Ø Through infected breast milk from mother to child or in the womb

Signs and Symptoms

¨ Prolong diarrhea

♦ Headache

¨ Fatigue or weakness

♦ Joint pain

¨ Persistent dry cough

♦ Swollen glands

¨ Frequent fevers

♦ Loss of appetite

¨ Sores around genitals and lips

¨ Pneumonia and other diseases due to the breakdown of the immune system

Prevention

v Abstain from sex

v Have sex with a single partner who is uninfected

v Avoid having unprotected sex

v Do not share needles or inject illicit drugs.

v Proper screening of blood used for transfusion

v Use disposable syringes and needles or sterilize hypodermic needles adequately

Cholera

Cholera is a bacterial disease usually spread through contaminated food and water. It is caused by Vibrio cholerae.

Mode of transmission

§ By taking in contaminated food and water

§ Through contact with faeces, urine and septum of an infected person

Symptoms

o Diarrhea

○ Nausea and vomiting

o Dehydration

o Severe dehydration can lead to irritability, sunken eyes, a dry mouth, dry and shriveled skin, low blood pressure, and irregular heartbeat (arrhythmia).

o Dehydration may lead to a rapid loss of minerals in the blood (electrolytes). This is called an electrolyte imbalance.

Prevention

· Wash hands with soap and water frequently, before handling food.

· Drink treated water

· Eat food that's completely cooked and hot

· Avoid street vendor food, if possible.

· Practicing good sanitary habitat

Tuberculosis (TB)

Tuberculosis is an air borne disease. The bacterium that causes TB is called Mycobacterium tuberculosis.

Mode of transmission

o Droplets infection

o Using infected person’s eating utensils

o Drinking milk from infected cattle

Symptoms

¨ Chest pain

♦ Weight loss

¨ Shortness of breath

♦ Loss of appetite

¨ Coughing that lasts for long time

¨ Green, yellow, or bloody sputum

Prevention

· Vaccination

· Isolation of infected person

· Treating infected persons

· Pasteurization of milk before drinking

· Frequent medical exams and chest x-rays for early detection

Tetanus

It is a bacterial disease caused by Clostridium tetani.

Mode of transmission

§ Contamination of wound with dirt containing the germs

§ through the bits of a dog or cat

§ using unsterilized blade, knife scissors to cut umbilical cord

Symptoms

o Muscle spasms

○ Locked jaw

o Aches in limbs

○ Painful breathing

Prevention

ü Immunization any time one gets a wound

ü Use sterilized blade, knives or scissors

ü Injection of drug to relax muscles

Diphtheria

It is disease cause by bacterium called Corygnebacterium diphtheriae.

Mode of transmission

Ø Through contaminated food, such as milk

Ø Droplet infection

Symptoms

o Damage of kidney

○ Sore throat

o Inflammation of heart

○ High fever

o Large tender glands in neck

Prevention: Vaccination with (anti-toxoid)

Whopping cough

Whopping cough (also known as pertussis) is a bacterial infection that infect the nose and throat. It caused by bacteria called bordetalla pertusis

Mode of transmission

o inhalation of infected air droplets

Symptoms

· Mild coughing

● Sneezing

· Runny nose

● Low fever

Prevention: Vaccination

Gonorrhea

Gonorrhea is one of the most common diseases passed from one person to another through sexual contact. Gonorrhea is caused by a bacterium called Neisseria gonorrhoeae.

Mode of transmission

§ Through vaginal, oral, or anal sexual relations with an infected person

Symptoms

· Pus or discharge from genital organ

· Lower abdominal or pelvic pain

· Burning when urinating

· Conjunctivitis (red, itchy eyes)

· itching around genital

· Burning in the throat (due to oral sex)

· Swollen glands in the throat (due to oral sex)

· Painful or swollen testicles

Prevention

o Use of condoms

o Avoid sexual contact with infected partners.

o Avoid indiscriminate sex

o Treat infected sexual partners before having sexual relations

o Health education

Syphilis

Syphilis is primarily a sexually transmitted infection (STI) caused by Treponema pallidum bacteria.

Mode of transmission

§ Through sexual intercourse with an infected person

§ From an infected mother to foetus

Symptoms

Ø Tiny sore at tip of penis

Ø Swelling of lymph nodes at groins

Ø Shrinking of testes

Ø Sterility in women

Ø Infected women bring forth blind and deformed babies

Prevention

ü Use of condoms

ü Avoid sexual contact with infected partners.

ü Avoid indiscriminate sex

ü Treat infected sexual partners before having sexual relations

ü Health education

Typhoid

Typhoid is an infection caused by the bacteria Salmonella typhi.

Mode of transmission

¨ Contaminated food and water

Symptoms

o Fever

○ Muscular pains

○ Diarrhea

o Constipation

○ Severe frontal headache

Prevention

¨ Vaccination

♦ Drinking clean water

¨ Eating uncontaminated food

¨ Proper disposal of sewage

Cerebro-spinal meningitis

It is also called spotted fever. It usually attacks children and adults in the dry season. It is caused by bacteria called Neisseria meningitis.

Mode of transmission: Droplet infection

Symptoms

· High fever

● Stiff neck

· Coma

● Convulsion

· Severe headache

Prevention

v Isolating infected person

v Avoid overcrowding

Dracunculiasis

Dracunculiasis, also known as Guinea worm disease, is an infection caused by the parasite Dracunculus medinensis.

Mode of transmission

ü Intake of contaminated water

Symptoms

¨ Blisters

♦ Itchy rash

¨ Painful tumor

♦ boils

Prevention/Control

§ Avoiding drinking, bathing or washing with contaminated water

§ Boiling contaminated water

§ Health education and community mobilization.

§ Prevent infected person from entering ponds and water used for drinking.

Schistosomiasis (Bilharzia)

Schistosomiasis is a disease caused by parasitic flatworms called Schistosoma.

Mode of transmission

Infection occurs when the skin comes in contact with contaminated freshwater. Schistosoma eggs enter freshwater when infected people urinate or defecate in the water. The eggs hatch, and if certain types of snails are present in the water, the parasites develop and multiply inside the snails. The parasite leaves the snail and enters the water. Schistosoma parasites can penetrate the skin of persons who are wading, swimming, bathing, or washing in contaminated water. The parasite matures into adult worms, reside in the blood vessels of the body where the females produce eggs. Some of the eggs travel to the bladder or intestine and are passed into the urine or stool.

Symptoms

· Rash or itchy skin

● Blood in the urine

· Frequent urination

● painful urination

Prevention

v Avoid swimming or bathing in contaminated water

v Proper disposal of human excreta

v Kill intermediate hosts (water snail).

v Eliminating aquatic weeds which harbor the snail.

Ascariasis

Ascariasis is an intestinal infection caused by the parasitic Ascaris lumbricoides, a large roundworm.

Mode of transmission

Ø eggs in soil introduced into the mouth by dirty fingers

Ø contaminated water and food

Symptoms

o Loss of weight

○ Vomiting

o constipation

○ Nausea

Prevention

¨ washing hands thoroughly before eating

Onchocerciasis (River blindness)

Onchocerciasis is a parasitic disease caused by nematode, called Onchocerca volvulus. It is transmitted to humans by the bite of the female blackfly (Simulium sp.).

Symptoms

· Severe itching

● Blindness

· Bumps under the skin

· Enlargement of lymphatic glands

Prevention

§ Avoid being bitten by flies

§ Use of smoke bomb to scare vectors

§ Use of insect repellent and proper clothing

§ Spraying river surface with insecticide to kill larvae

§ Improving sanitation practices and water management to reduce the presence of the flies

Malaria

Malaria is a disease caused by a protozoan called Plasmodium sp. It’s a parasite which infects the red blood cell.

Mode of transmission

¨ Through the bite of infected female anopheles mosquito

Symptoms

· Loss appetite

● High fever

· Pain at joint

● Dizziness

· Vomiting

● Stomach cramps

· Headache

● Anaemia

· Weakness and shivering

· Sweating and fall temperature

Prevention

§ Sleeping in mosquito net, using mosquito coil or repellents

§ Mosquito proofing houses

§ Draining swamps or stagnant waters

§ Pouring oil on stagnant water

§ Introducing tilapia into ponds

Ringworm (Tinia)

It is a fungal disease

Mode of transmission

Ø Direct contact with infected person

Ø Using infected person’s towel, comb, hats

Symptoms

v Small red round patches on skin or head

v Itching within patches

v Loss of hair where patches occur

Prevention

· Personal hygiene

· Avoid contact with infected person

Diseases Caused Microbes in Plant

Disease	Causative Agent	Mode of Transmission	Symptoms	Control
Black pod disease of cocoa	Fungus -Phytophthora palmivora	Infective spore spread by splashing rain water and insects	Pod get black and rotten	-All infected pods should be burnt -Pods should be sprayed with fungicide
Swollen shoot of cocoa	Virus	Virus transmitted by nymph of mealy bugs from diseased plants to healthy plants	-Yellowing of leaves; -Swollen of stem and root	Destruction of infected trees
Maize rust	Fungus- Piccinia polysora	Airborne spores deposited on leaves	Brownish-red portions on leaves	-Use resistant varieties -Dressing with fungicides
Cassava Mosaic	Virus	Piercing and sucking insects	-Distortion of leaves -Stunted growth	By growing resistant varieties

Diseases Caused Microbes in Farm Animals

Disease	Causative agent	Mode of transmission	Symptoms	Control
Coccidiosis of Poultry	Protozoan	Contaminated food or water	-Drop in feed intake -Blood stained droppings -Rough feathers -Diarrhea	-Proper disposal of dead birds - Disinfection of troughs and cans
New Castle of Poultry	Virus	Direct contact with infected bird or through diseased eggs	-Sudden jerking of neck -Yellowish white diarrhea -Severe respiratory difficulties & paralysis	-Vaccination -Culling or killing and removing infected birds.
Foot and Mouth Disease of cattle	Virus	Direct contact with infected animals	-Fever -Small fluid filled swelling in the mouth and feet	- Vaccination - Proper quarantine of imported stocks
Rinderpest of cattle	Virus	-Contact with infected faeces -Nasal or oral secretion of diseased animals	-Fever -Lesions of lower lips -Nasal discharge -Severe diarrhea -Blood stained faeces	-Vaccination - Slaughtering affected animals

Immunity

ImmImmunityune system is the collection of cells, tissues and molecules that protects the body from numerous pathogenic microbes such as bacteria, viruses and fungi.

Immunity is the capability of the body to resist disease or harmful microorganism invasion. Immunity involves both specific and nonspecific components.

Humans have three types of immunity: innate, adaptive, and passive

Innate Immunity

Innate immunity, or nonspecific immunity, is the natural resistances with which a person is born. It provides resistances through physical, chemical and cellular approaches. Innate immunity includes the external barriers of the body, like the skin and mucous membranes (like those that line the nose, throat, and gastrointestinal tract), which are the first line of defense in preventing diseases from entering the body.

Adaptive Immunity

Adaptive immunity is second line of protection against pathogens that are able to overcome innate immune defenses. It is sub-divided into two major types depending on the cells involved.

o Humoral immune responses: humoral immune responses resist invaders that act outside of cells, such as bacteria and toxins. During humoral responses, proteins called antibodies which can stick to and destroy antigens, appear in the blood and other body fluids. Humoral immune responses can also prevent viruses from entering cells.

o Cell-mediated immune responses: cell-mediated responses resist invaders that reproduce within the body cells, such as viruses. During cell-mediated response, cells that can destroy other cells become active. Their destructive activity is limited to cells that are either infected with or producing a specific antigen.

Passive Immunity

Passive immunity is "borrowed" from another source and it lasts for a short time. For example, antibodies in a mother's breast milk provide a baby with temporary immunity to diseases the mother has been exposed to. This can help protect the baby against infection during the early years of childhood.

Immunization

Immunization or Vaccination or Inoculation is the method introducing vaccines (treated or modified pathogenic microorganisms) containing attenuated antigens into the bloodstream of healthy person. The treated microorganisms (either live or killed) do not cause the disease, but rather stimulate the production of antibodies or trigger the body’s immune system to build a defense mechanism against the disease. If person immunized against a particular disease and later comes into contact with the disease-causing agent, the immune system is immediately able to respond defensively.

There are two types of immunization: active and passive

Active Immunization

Active immunization is a form of acquired immunity in which the body is made to produce its own antibodies against pathogens by injecting a person with all or part of dead or weakened pathogens. It provides long-lasting immunity. The vaccines are usually considered risky for people who have a damaged immune system, such those infected with HIV or those receiving chemotherapy for cancer or organ transplantation. Without a healthy defenses system to fight infection, these people may develop the disease that the vaccine is trying to prevent. Some immunizing agents require repeated inoculations or booster shots at specific intervals.

Passive immunization

Passive immunization is where synthesized antibodies of the immune system are transferred to a person so that the body does not need to produce them. This method works very quickly, but it is short lasting, because the antibodies are naturally broken down.

v Passive immunization occurs naturally or physiologically, when antibodies are transferred from mother through the placenta to fetus during pregnancy, (or from the breast milk), to provide a baby with temporary immunity to diseases.

v Artificial passive immunization is normally acquired by injection of antiserum. Antibodies are formed in one individual (man or horse), extracted and injected into another individual.

SSCE/WASSCE/GCE PASS QUESTIONS AND ANSWERS

OBJECTIVE

1. Which of the components of blood is damaged in a patient suffering from AIDS?

A. Erythrocytes C. Plasma

B. Leucocytes D. Platelets

2. Which of the following disease can be caused by a bacterium?

A. Ringworm C. Malaria

B. Poliomyelitis D. Syphilis

3. In the tapeworm the suckers on the scolex are used for

A. sucking the blood of the host

B. holding fast to the host

C. reproduction

D. locomotion

4. Which of the following disease is rarely spread by a housefly?

A. Yellow fever C. Typhoid fever

B. Dysentry D. Poliomyelitis

5. Which set of disease is spread mainly by insect vectors?

A. Cholera, tenia and gonorrhea

B. Poliomyelitis, tuberculosis and syphilis

C. Cholera, malaria and tuberculosis

D. Malaria, cholera and river blindness

6. Malaria symptoms are caused by

A. toxins released into the blood as a result of the destruction of red blood cell

B. the multiplication of the malaria sporozites in the liver

C. the invasion of the red blood cells by the trophozoites

D. the development of merozoites into gametocytes

7. Which of the following is a measure for the control of bilharzia?

A. Cutting low brushes around homes

B. Application of molluscicides in water bodies

C. Screening windows and doors with mosquito nets

D. Application of herbicides in water bodies

8. Some of the diseases caused by bacteria are

A. tuberculosis, gonorrhoea and syphilis

B. tuberculosis, gonorrhoea and AIDS

C. Poliomyelitis, syphilis and gonorrhea

D. AIDS, cholera and tuberculosis

9. Which of the following groups of diseases are associated with water?

I Onchocerciasis II Schistosomiasis

III Dracunculiasis IV Elephantiasis

V Taeniasis

A. I, II and III C. II, III and IV

B. II, IV and V D. I, II and V

10. The construction of dams may lead to an increase in the prevalence of

A. typhoid fever, measles and yellow fever

B. tuberculosis, leprosy and trypanosomiasis

C. guinea worm, malaria and tuberculosis

D. malaria, bilharziasis and onchocerciasis

11. Vaccination is carried out in order to

A. check the production of poison

B. increase the activity of white blood cells

C. increase the number of red blood cells

D. stimulate the production of antibodies

12. The most common means of transmitting the Acquired Immune Deficiency Syndrome (AIDS) is

A. from mother to child

B. through blood transfusion

C. through sexual intercourse

D. through the sharing of needles

13. The blackfly is a vector of

A. malaria C. onchocerciasis

B. trypanosomiasis D. yellow fever

14. The causative agent of typhoid fever is

A. salmonella C. escherichia

B. entamoeba D. shigella

15. The causative agent of bird flu is a

A. protozoan C. bacterium

B. virus D. fungus

16. A boy who is found of swimming in a pond finds himself passing urine with traces of blood. He is likely to have contacted

A. schistosomiasis C. poliomyelitis

B. onchocerciasis D. salmonellosis

17. Which of the diseases listed below are associated with water?

I. Onchocerciasis III.Salmonellosis
II. Schistosomiasis IV. Meningitis

A. I and II only C. I, II and III

B. II, III and IV D. II and IV

18. I.Plasmodium II. Vibro Choleroe

III. Gonococcus sp IV. Poliomyelitis virus V. Syphilis bacteria

which of the following organism are transmitted by houseflies?

A. I and II only C. III and IV only

B. II and V only D. II and IV only

19. Which of the following are not causative organisms of plant diseases?

A. Fungi C. Bacteria

B. Viruses D. Cercariae

20. The vector of the malarial parasite is the

A. male Anopheles C. male Culex

B. female Culex D. female Anopheles

Answers

1. B	6. B	11. D	16. A
2. D	7. B	12. C	17. C
3. B	8. A	13. C	18. D
4. A	9. A	14. A	19. D
5. D	10. D	15. B	20. D

THEORY

1. (SSCE 1994, Q6) (a)(i) What are microbes?

(ii) Name any three useful microbes and in each case state its importance.

(b) Copy and complete the table

Disease

Causative agent

Vector

Symptoms(only one)

Control (only one)

(i) Schistosomiasis

(ii) Malaria

(iii) Onchocerciasis

(iv) Maize rust

Solution

(ii)

Microbes	Importance
i. Bacteria	· Production of cheese, yoghurt and butter · Nitrogen fixation
ii. Yeast	¨ Alcohol production ¨ Fermentation of cocoa bean
iii. Penicillium	o Production of antibiotics

(b)

Disease	Causative agent	Vector	Symptoms (only one)	Control (only one)
(i) Schistosomiasis	Schistosoma	Water snail	Blood in stool or urine	Proper disposal of human excreta
(ii) Malaria	Plasmodium	Anopheles mosquito	Loss of appetite or headache	Sleeping in mosquito net
(iii) Onchocerciasis	Onchocerca	Black fly	Blindness	Use of smoke bomb to scare vectors
(iv) Maize rust	Fungus	Air or wind	Brownish red portion on leaves	Dressing with fungicide

2. (SSCE, 1997 Q5) For each of the organisms, state five ways in which it is of economic importance.

(i) Bacteria (ii) Fungi

Solution

Bacteria

o It digests cellulose in the large intestine of some herbivore.

o Acts as decomposers and help to recycle nutrients

o It brings about denitrification

o It causes disease

o It causes fermentation e.g. cheese and yoghurt.

Fungi

o It causes disease

o Acts as decomposers and help to recycle nutrients

o It causes fermentation in breweries and baking industries

o It causes destruction to stored food

o It serves as source of food

o It is important in the production of antibiotics.

3. (SSCE 2000, Q4) (a) (i) Name the causative agent of malaria.

(ii) Explain how causative agent is spread.

(b) (i) How can the knowledge of the life cycle of the malaria vector be used to devise control measure?

(ii) What problems may arise in using such control measures?

Solution

(a) (i) Plasmodium

(ii) it is spread by the bite of a female anopheles mosquito, carrying the malaria parasite and introducing it into the blood.

(b) (i) the life style of mosquito starts from an egg through larval and pupal stage, the remaining stages are found in stagnant waters and such sites can be destroyed by burying empty cans and clearing vegetation near houses, and by draining breeding places. Where the water body is extensive, spraying of the water surface with a thin layer of oil will be useful. It will reduce the surface tension of the water which cannot support the larvae and the pupae. This will therefore cause their death through suffocation. Biological control methods such as introducing small predatory fish to feed on the developmental stages is recommended. Also employ the avoidance of mosquito bites by using netting, repellents and the destruction of adult mosquitoes using insecticides.

(ii) Problems

¨ Adverse effects of insecticides on other fauna predators

¨ Mosquitoes develop resistance to insecticides after a while

¨ Spraying the water with oil/insecticides may seriously affect other aquatic animals e.g., fish as well as their prey.

¨ Water quality is reduced

4. (SSCE 2005, Q6) (a) (i) What are microbes?

(ii) List five ways in which microbes are benefit to man.

(b) (i) Distinguish between infectious and non-infectious diseases.

(ii) Name three human diseases that are caused by the following microbes:

(α) Viruses (β) Bacteria (γ) Protozoa

Solution

(a) (i) Microbe is a microscopic organism, which may be a single cell or multicellular organism.

(ii) Ways in which microbes are beneficial to man

ü Production of antibiotics and drugs

ü Useful in sewage disposal

ü Useful in brewing industries for beer production

ü Useful in baking industries for bread making

ü Useful in food processing for making butter

ü Increase soil fertility by fixing atmospheric nitrogen

ü Decomposition of dead organic matter

(b) Refer to notes for solution

(ii) (α) Viral diseases: HIV/AIDS, yellow fever, influenza, mumps, small pox, chicken pox, poliomyelitis, hepatitis.

(β) Bacterial diseases: tuberculosis, cholera, typhoid, tetanus, leprosy

(γ) Protozoan diseases: malaria, amoebic dysentery, sleeping sickness.

5. (WASSCE 2011, Q3) (a) Copy and complete the table below.

Disease	Causative organism	Part of the body affected
Malaria
Whopping cough
Poliomyelitis

(b) Explain how the each of the causative organism named in (a) above is transmitted from one person to the other.

(i) poliomyelitis (ii) guinea worm infestation

Solution

Disease	Causative organism	Part of the body affected
Malaria	Plasmodium	Red blood cells/liver cells
Whopping cough	Bordetella pertussis	Respiratory tract/ lungs
Poliomyelitis	Polio virus	Limbs/spinal cord

(b) Transmission of causative agent:

Plasmodium: is transmitted when female anopheles mosquito bites a person with parasite in his or her blood and then bites a healthy person.

Bordetella pertussis: it transmitted when an infected person coughs, infected air droplets is inhaled by a healthy person.

Polio Virus: it is transmitted through intake of contaminated water and food. Discharge of the virus is from the mouth, nose or faeces of patient to a healthy person.

6. (WASSCE 2011, Q5) List five diseases of human associated with arthropods

Solution

¨ Dysentry ¨ Cholera

¨ Yaw ¨ malaria

¨ Typhoid fever ¨ leprosy

¨ River blindness ¨ Elephantiasis

¨ Yellow fever ¨ trypanosomiasis