Diseases Topic 1

Question 1

Cholera

Answer 1

Cholera is a diarrhoeal disease caused by a specific type of bacteria, that occur naturally in environmental sources of water, such as rivers, lakes and estuaries.

Cholera was endemic (always present) in 19th-century England, as it is in many parts of the world today.

People infected with cholera bacteria produce large amounts of watery, foul-smelling, pale diarrhoea, which results in rapid dehydration and loss of essential salts from the body. Unless the fluids and salts are rapidly replaced, death follows in about one-third of cases within a few days.

Question 2

Tuberculosis

Answer 2

Tuberculosis is an infectious disease usually caused by a bacteria, it generally affects the lungs, but can also affect other parts of the body.

The classic symptoms of active TB are a chronic cough with blood-containing sputum, fever, night sweats, and weight loss.

Question 3

Diabetes

Answer 3

More properly known as diabetes mellitus, a chronic disease that occurs when the pancreas does not produce enough insulin, or becomes insensitive to insulin. A common effect of uncontrolled diabetes is raised blood glucose (hyperglycaemia) which can gradually damage nerves and blood vessels.

Question 4

Measles

Answer 4

Measles is a highly contagious infection caused by the measles virus.

Initial signs and symptoms typically include fever, often greater than 40 °C (104.0 °F), cough, runny nose, and inflamed eyes.

2-3 days after the start of symptoms, small white spots may form inside the mouth, known as Koplik’s spots.
3-5 days after the start of symptoms a red, flat rash which usually starts on the face and then spreads to the rest of the body would appear. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days.

Question 5

Chickenpox

Answer 5

Chickenpox is a viral infection that causes an itchy rash of spots allover the body and flu-like symptoms.

Chickenpox often starts without the classic rash, with a fever, headache, sore throat, or stomachache. These symptoms may last for a few days, with the fever in the 101°-102°F (38.3°-38.8°C) range.
The red, itchy skin rash usually starts on the abdomen or back and face, then spreads to almost everywhere else on the body(including the scalp, mouth, arms, legs, and genitals).
The rash begins as many small red bumps that look like pimples or insect bites. They appear in waves over 2 to 4 days, then develop into thin-walled blisters filled with fluid. The blister walls break,leaving open sores, which finally crust over to become dry, brown scabs.
All three stages of the chickenpox rash (red bumps, blisters, and scabs) appear on the body at the same time.

Question 6

Smallpox

Answer 6

Smallpox is caused by a virus, it begins with a high fever, fatigue, muscle pain and headaches, followed by the eruption of characteristic sores all over the body, which become filled with pus – a thick, yellowish fluid containing infected and dead cells.

Question 7

Head Louse

Answer 7

causes irritation; site: head hair

Question 8

Tapeworm cysts

Answer 8

cause epileptic seizures; site: brain

Question 9

Toxocara

Answer 9

Adult can cause blindness and liver damage; sites: eyes, brain, muscle and liver

Question 10

Plasmodium

Answer 10

Causes malaria; sites: red blood cells, liver and brain

Question 11

Filarial Worm

Answer 11

can cause fever, elephantiasis and river blindness; sites: lymphatic system and eyes

Question 12

Liver Fluke

Answer 12

cause chronic liver disease; sites: liver and gall bladder

Question 13

Trypanosoma

Answer 13

cause sleeping sickness; site: blood

Question 14

Schistosoma

Answer 14

cause bilharzia; sites: intestine, liver and bladder

Question 15

Hookworm

Answer 15

can cause anaemia and protein deficiency; site: small intestine

Question 16

Body Louse

Answer 16

can transmit typhus and trench fever; site: in clothing and on skin

Question 17

Scabies

Answer 17

cause severe irritation; site: on top of skin, males dig burrows under skin

Question 18

Ticks

Answer 18

cause irritation, can transmit typhus and various fevers; site: on skin, feed by sucking blood

Question 19

Trichomonas

Answer 19

cause irritation and discharge; site: reproductive tract

Question 20

Tapeworm

Answer 20

can cause anaemia and malnutrition; site: intestines

Question 21

Entamoeba Histolytica

Answer 21

cause amoebic dysentery; sites: liver and large intestine

Question 22

Pathogenic soil-transmitted roundworms

Answer 22

Parasitic worms with rounded bodies that infect people via faecal–oral transmission when worm eggs from human or animal faeces contaminate soil.

Question 23

Tapeworms

Answer 23

Tapeworms are easily distinguished from roundworms because they have long flattened bodies (resembling a tape, hence their name). They are the largest of the worms that infect people; some species can grow up to 10 metres in length.

Although deaths due to tapeworms are rare, they cause pain in the abdomen and reduce the nutrients available to their human host. However, the main health risk is from epilepsy, i.e. brain seizures or fits

Question 24

The life cycle of the pork tapeworm, Taenia solium

Answer 24

Tapeworm eggs in pig faeces contaminate land around human settlements where pigs graze. Soil is also contaminated with eggs from human faeces if people are forced to defaecate in the open because there is no sanitation.

People are infected when they swallow the eggs in soil on unwashed vegetables or when eating with unwashed hands.

The eggs hatch into larvae [lar-vee] in the human gut.

Worm larvae may develop into adult tapeworms in the human gut, but some burrow into the person’s muscles, eyes and brain, where they ‘encyst’, i.e. become encased in a tough outer covering. Cysts in the brain can trigger epileptic seizures.

Around 30% of people with epilepsy in Latin America, Sub-Saharan Africa and South-East Asia have pork tapeworm cysts in their brain

Question 25

Filarial worms

Answer 25

Adult filarial worms are thread-like parasites measuring 40–100 millimetres in length.

The diseases they cause are all vector-borne.

The disease once known as elephantiasis because of the appearance of infected limbs is properly called lymphatic filariasis.

Question 26

Lymphatic filariasis

Answer 26

Most cases are due to one species, Wuchereria bancrofti, transmitted to humans by mosquitoes.

The filarial worm larvae block the fine lymphatic tubules that collect tissue fluid from all over the body and return it to the blood stream. The blockages cause painful inflammation and swelling, as fluid collects in the lower limbs and genitals.

More than 120 million people are infected with filarial worms in 73 countries, including Bangladesh, India, Indonesia, Ethiopia, Nigeria and the Philippines, and 40 million people are severely disabled by them.

Question 27

River Blindness

Answer 27

The microscopic larvae of another species of filarial worm (Onchocerca volvulus) are transmitted by blackflies that bite humans.

The larvae cause skin lesions that itch relentlessly, but the larvae also invade the eyes and cause ‘river blindness’, so-called because blackflies breed in fast-flowing rivers, so this disabling condition only occurs in riverside communities.

Question 28

Schistosoma flukes

Answer 28

Schistosoma flukes must complete part of their life cycle in freshwater snails, which shed microscopic larvae into the water.

When people enter infected water to fish or wash themselves or their clothes, the larvae penetrate the person’s skin along the track of hairs, usually on the legs.

The larvae mature into adult flukes (10–16 millimetres long) in the person’s body. Adult male and female flukes mate and produce eggs with sharp spines that damage blood vessels, mainly in the liver, gut and bladder.

Fluke eggs excreted in the faeces and urine of infected people are flushed into water sources in the environment, where they hatch into larvae, which reinfect aquatic snails and the cycle begins all over again.

Question 29

Pathogenic protists

Answer 29

The pathogenic protists that infect humans are all single-celled organisms, formerly called ‘protozoa’. They are responsible for a range of diseases, including:

dysentery (bloody diarrhoea) caused by waterborne protists similar to the amoebae [amm-ee-bee] commonly found in freshwater ponds.

sleeping sickness, caused by protists transmitted via the bite of tsetse flies.

leishmaniasis [leesh-man-eye-ah-sis] transmitted by biting sandflies; Leishmania protists cause painful lesions in the skin, affecting around one million people, or potentially fatal enlargement of the liver and spleen with up to 400 000 cases annually..

Question 30

Fungal infections

Answer 30

the most common fungal infections in humans are ringworm, athlete’s foot and thrush.

Question 31

Candida albicans

Answer 31

Candida albicans, which causes thrush, exists in two forms – as single-celled yeasts (measuring 3–5 micrometres) and as multicellular filaments which can be several millimetres in length.

Thrush is characterised by inflammation, especially in the mouth, and also in the vagina where the infection causes intense itching.