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BTEC Level 3 Unit 43 : Disease and Infection
Transcript of BTEC Level 3 Unit 43 : Disease and Infection
Diseases with environmental causes and links
protozoal - eg malaria, giardia;
arthropod infestation - eg scabies, lice, ticks;
metazoal (Schistosomes, trypanosomes) - eg Bilharzia;
pathogenic bacterial - eg staphylococci, gonorrhoea, meningitis;
systemic or deep mycoses - eg respiratory and disseminated types
subcutaneous mycoses - eg sporotrichosis, chromomycosis;
helminthic - eg tapeworms, hookworms;
viral - eg HIV, chicken pox;
nutritional deficiency diseases, eg rickets, anaemia;
diseases caused by pollution eg asbestosis/mesothelioma;
chronic dietary disease eg cardiovascular disease, obesity, diabetes;
cancers eg those linked to radiation poisoning, those caused by exposure to UV A and B radiation (such as melanoma);
diseases caused by chemical poisoning eg minamata;
Diseases with environmental causes and links
disease due to ageing and degenerative body function or where the causes are less clear, eg Alzheimer’s, osteoporosis
Know the different types of diseases and infections
Protozoa are microscopic, one-celled organisms that can be free-living or parasitic in nature. They are able to multiply in humans, which contributes to their survival and also permits serious infections to develop from just a single organism. Transmission of protozoa that live in a human's intestine to another human typically occurs through a fecal-oral route (for example, contaminated food or water or person-to-person contact). Protozoa that live in the blood or tissue of humans are transmitted to other humans by an arthropod vector (for example, through the bite of a mosquito or sand fly).
Centers for Disease Control
Fantastic series of video lectures on Biology
Malaria kills approximately 660,000 people each year, most of them young children in sub-Saharan Africa.
Malaria parasites infecting successively two types of hosts: humans and female mosquitoes.
In humans, the parasites grow and multiply in the liver cells and then in the red cells of the blood.
The blood stage parasites are those that cause the symptoms of malaria. When these parasites are picked up by a female mosquito during a blood meal, they start another, different cycle of growth and multiplication in the mosquito.
After 10-18 days, the parasites are found in the mosquito's salivary glands. When the mosquito takes a blood meal on another human, the parasites are injected with the mosquito's saliva and start another human infection when they parasitize the liver cells.
Thus the mosquito carries the disease from one human to another (acting as a "vector"). Differently from the human host, the mosquito vector does not suffer from the presence of the parasites.
Giardia is a microscopic parasite that causes the diarrheal illness known as giardiasis. Giardia (also known as Giardia intestinalis, Giardia lamblia, or Giardia duodenalis) is found on surfaces or in soil, food, or water that has been contaminated with feces (poop) from infected humans or animals.
Giardia is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it tolerant to chlorine disinfection. While the parasite can be spread in different ways, water (drinking water and recreational water) is the most common method of transmission.
An arthropod is an invertebrate animal having an exoskeleton (external skeleton), a segmented body, and jointed appendages.
As they are animals, they are multicellular and so much larger than protazoa.
Human scabies is caused by an infestation of the skin by the human itch mite. The microscopic scabies mite burrows into the upper layer of the skin where it lives and lays its eggs.
The most common symptoms of scabies are intense itching and a pimple-like skin rash.
The scabies mite usually is spread by direct, prolonged, skin-to-skin contact with a person who has scabies.
Scabies occurs worldwide and affects people of all races and social classes. Scabies can spread rapidly under crowded conditions where close body contact is frequent. Institutions such as nursing homes, extended-care facilities, and prisons are often sites of scabies outbreaks.
Most ticks go through four life stages: egg, six-legged larva, eight-legged nymph, and adult. After hatching from the eggs, ticks must eat blood at every stage to survive. Ticks that require this many hosts can take up to 3 years to complete their full life cycle, and most will die because they don't find a host for their next feeding.
Ticks suck the blood of their victims but are not dangerous in themselves.
Ticks do however act as a VECTOR for other diseases such a s lyme disease which they pass on to humans when they feed.
An infestation of ticks is very rare in humans as the problem is easily diagnosed. It is more common in animals though who are not capable of seeking treatment on their own.
Lice are parasitic insects that can be found on people's heads, and bodies, including the pubic area. Human lice survive by feeding on human blood. Lice found on each area of the body are different from each other. The three types of lice that live on humans are:
Pediculus humanus capitis (head louse)
Pediculus humanus corporis (body louse, clothes louse)
Pthirus pubis ("crab" louse, pubic louse)
Only the body louse is known to spread disease.
Lice infestations (pediculosis and pthiriasis) are spread most commonly by close person-to-person contact. Dogs, cats, and other pets do not play a role in the transmission of human lice. Lice move by crawling; they cannot hop or fly. Both over-the-counter and prescription medications are available for treatment of lice infestations.
Schistosomiasis, also known as bilharzia, is a disease caused by parasitic worms. More than 200 million people are infected worldwide. In terms of impact this disease is second only to malaria as the most devastating parasitic disease. Schistosomiasis is considered one of the Neglected Tropical Diseases (NTDs).
The parasites that cause schistosomiasis live in certain types of freshwater snails. The infectious form of the parasite, known as cercariae, emerge from the snail, hence contaminating water. You can become infected when your skin comes in contact with contaminated freshwater.
A bite by the tsetse fly is often painful and can develop into a red sore, also called a chancre. Fever, severe headaches, irritability, extreme fatigue, swollen lymph nodes, and aching muscles and joints are common symptoms of sleeping sickness. Some people develop a skin rash. Progressive confusion, personality changes, and other neurologic problems occur after infection has invaded the central nervous system. If left untreated, infection becomes worse and death will occur within months.
Pathogenic bacteria is bacteria which are capable of causing disease.
Humans are usually generally most interested in the species of pathogenic bacteria. Pathogenic bacteria can be spread through human population in a range of ways. Air, water, and soil are common vectors and people may also pass directley to each other through physcial contact.
Treatment of pathogentic bacteria involves the use of antibiotics , drugs which have being specifically designed too kill of bacteria. Although sometimes the body may be antibiotic resistance
Helminthic - eg tapeworms, hookworms;
Viruses are capsules with genetic material inside. They are very tiny, much smaller than bacteria. Viruses cause familiar infectious diseases such as the common cold, flu and warts. They also cause severe illnesses such as HIV/AIDS, smallpox and haemorrhagic fevers.
Metazoal is a disease caused by metazoan parasites, such as nematodes, cestodes, trematodes, or arthropods.
Schistosomiasis is a type of infection caused by parasites that live in fresh water, such as rivers or lakes, in subtropical and tropical regions worldwide. It is also known as bilharzia.
Sleeping sickness, also called "human African trypanosomiasis", is a widespread tropical disease that can be fatal if not treated. It is spread by the bite of an infected tsetse fly (Glossina Genus), a species native to the African continent.
Sleeping sickness is caused by two germs (protozoa),
Tsetse flies carry the infection. When an infected fly bites you, the infection spreads through your blood.
Risk factors include living in parts of Africa where the disease is found and being bitten by tsetse flies. The disease does not occur in the United States. But travelers who have visited or lived in Africa can have the infection.
The word ‘helminth’ is a general term meaning ‘worm’.Helminths are parasitic worms that cause a wide variety of infectious diseases, some of which involve the musculoskeletal system.
Helminths may be classified into nematodes or roundworms, trematodes or flatworms, and cestodes or tapeworms.
what cause aperson to get Schistosomiasis?
The parasites that cause schistosomiasis are called schistosomes. At the stage of infection, they are just barely visible to the naked eye and known as a cercaria.
They are capable of burrowing into human skin, where they develop into later stages and move closer to the abdomen to lay eggs. The disease is caused by the immune system reacting to these eggs.
Some symptoms include:
blood in the urine
abdominal pain or cramps
paralysis of the legs
ascarid ‘roundworms’ have large bodies with 3 prominent anterior lips. Their life- cycles involve a stageof pulmonary migration where larvae released from ingested eggs invade the tissues and migrate through the lungs before returning to the gut to mature as adults. Ascaris infections in humans cause gastroenteritis, protein depletion and malnutrition and heavy infections can cause gut obstruction.
Strongyle ‘hookworms’ have dorsally curved mouths armed with ventral cutting plates or teeth which they embed in host tissues to feed on blood. They have complex life-cycles where larvae develop in the external environment (as ‘geo-helminths’) before infecting hosts by penetrating the skin. Once inside, they undergo pulmonary migration before settling in the gut to feed.
These are chronic, localized infections of the skin and
subcutaneous tissue following the traumatic implantation
of the aetiologic agent.The causative fungi are all soil
saprophytes of regional epidemiology whose ability to
adapt to the tissue environment and elicit disease is
These mycoses are heterogeneous, but all are caused by
penetrating trauma of the skin.
Grown on soil or on decaying vegetation.
Gonorrhea is a sexually transmitted disease that can infect both men and women, it can cause infections in the rectum, throat and genitals. It is a very common infection between the ages of 15 - 24 year olds.
Gonorrhea is spread by anal, vaginal or oral sex with somebody who already has gonorrhea. A pregnant women with gonorrhea can give the infection to her baby during child birth. The way of preventing gonorrhea is by using a condom, whilst having sexul intercourse.
Some men with gonorrhea may have no symptoms at all. However men who do have symptoms may have :
A burning sensation when urinating
A white, yellow or green discharge from the penis;
Painful or swollen testicles (least common)
Most women don't have any symptoms. Even if a women does suffer with any symptoms they're very mild and can be mistaken for bladder or vaginal infection. However women who suffer with gonorrhea are at risk of developing serious complications from the infection. Symptoms in women may include :
Painful or burning sensation when urinating;
Increased vagial discharge
Vaginal bleeding between periods
Gonorrhea can be cured with the right treatment. Although if gonorrhea is untreated it can cause fertility problems.
Nutritional deficiency diseases
It occurs when your body doesn't have enough vitmains needed to produce adequate number of halthy blood cells. If your diet is lacking certain virmains, then vitamin defiencey anemia can develop. or vitmain deficiency anemia can develop because your body cant properly absorb the nutrients from the foods you eat.
A lack of healthy blood cells that is caused by lower than normal amounts of certain vitamins. Vitamins linked to vitmain defiency anemia include: folate, vitamin B-12 and vitamin C.
Cutaneous and subcutaneous tissues and
adjacent lymphatics that suppurate, ulcerate and drain.
Highly contagious on contaminated dressings to patients with wounds.
• Chromoblastomycosis (subcutaneous and cutaneous tissues of the hands and feet). D
• occurs rarely in animals (such as, horses, cats, dogs, and frogs)
• soil-inhabiting fungi
• susceptibility enhanced by going barefoot or wearing sandals
• found almost exclusively in laborers
• enters hand or feet after trauma
• found primarily in the tropics or subtropics
• dull red or violet color on skin may resemble a ringworm lesion
• develops into a verrucous lesion
• pruritus (itchiness) and papules may develop
• fungus gets under the skin (produces bumps)
• bumps may block lymphatic system and cause elephantiasis
• sometimes bacterial infection may enter and cause a secondary infection
• rarely this fungus spreads to other areas of the subcutaneous tissue.
• potentially may spread to brain (life-threatening in that case)