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List of eight common infectious diseases seen in humans:- 1. Typhoid 2. Pneumonia 3. Common Cold 4. Malaria 5. Amoebiasis 6. Ascariasis 7. Elephantiasis 8. Ringworms.
Disease # 1. Typhoid:
Causative agent of typhoid is bacteria Salmonella typhi which enter the small intestine through the contaminated water and food and migrates to other organs of the body through blood.
Symptoms include high fever (39-40°C), weakness, stomach pain, constipation, headache and loss of appetite. In serious cases, intestinal perforation and death may also occur.
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Diagnostic Test Widal test.
A cook named Mary Mallon, called Typhoid Mary was the first typhoid carrier to be diagnosed, who continued to infect people for several years through the food she prepared.
Disease # 2. Pneumonia:
It is caused by bacteria Streptococcus pneumoniae and Haemophilus influenzae.
Pneumonia infects alveoli of the lungs and due to infection; the alveoli get filled with fluid therefore, leading to problems in breathing and respiration.
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Symptoms include fever, chills, cough and headache. In severe cases, lips and finger nails may turn greyish to bluish.
The infection is acquired by inhaling the droplets/aerosols released by an infected person, also by sharing glasses and utensils with an infected person.
Dysentery, plague, diphtheria, etc., are some of the other bacterial diseases in man.
Disease # 3. Common Cold:
Causative agents of common cold is rhinoviruses. It is the most common infection in the human. These viruses affect the nose and the respiratory passage but not the lungs.
Symptoms include nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness, etc. Symptoms usually lasts for 3-7 days.
Infection is transmitted through:
(a) The infected coughing or sneezing of an infected person.
(b) Through the contaminated objects such as pens, books, cups, doorknobs, computer, etc.
Disease # 4. Malaria:
Causative agent of malaria is a protozoan Plasmodium species and transmitting agent is Anopheles female mosquito, that transfers the sporozoites of Plasmodium. Different species of Plasmodium (P. vivax, P. malariae and P. falciparum) are responsible for different types of malaria. Malignant malaria caused by Plasmodium falciparum is the most serious and can even be fatal.
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Symptoms:
Influenza like illness, shaking chills, headache, muscle ache, nausea, vomiting and diarrhoea may occur. Malaria may also cause anaemia and jaundice (yellow colouring of the skin and eyes) because of the loss of red blood cells.
If remain untreated, malaria can quickly become life-threatening by disrupting the blood supply to vital organs and may even cause kidney failure, seizures, mental confusion, coma and even death. Malaria parasite requires two hosts, i.e., human and mosquito to complete its life cycle.
The life cycle of the Plasmodium is as follows:
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(a) Plasmodium enters the human body as sporozoites through the bite of infected female Anopheles mosquito.
(b) The sporozoites reach the liver through blood and multiply within the liver cells and then attack the Red Blood Cells (RBCs) resulting in their rupture.
(c) The rupture of RBCs and is associated with the release of a toxin called haemozoin, which is responsible for the high recurring fever and the chill/shivering.
(d) Gametocytes (sexual stages) develop in the RBCs of female Anopheles.
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(e) The parasite then enters the mosquito’s body along with the blood when it bites the infected person.
(f) Further development occurs in the stomach wall of the mosquito and gamete fuse to form a zygote.
(g) Thus, the zygote undergoes further development in the body of the mosquito to form sporozoites.
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(h) These sporozoites are then transported and stored in their salivary glands and are transferred into a human body during the bite of the mosquito.
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Note:
Life cycle is asexual in human and it is sexual in case of mosquito.
Malaria can be prevented by killing mosquitoes by spraying DDT, BHC, etc., and also by using mosquito repellents, mosquito nets, etc.
Disease # 5. Amoebiasis:
It is caused by an intestinal parasite. Entamoeba histolytica, which is found in large intestine of human. Transmitting agent is housefly. It transmits the parasite from faeces of infected person to the food.
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Symptoms Include constipation, abdominal pain and cramps, stools with excess mucous and blood clots. Water and food contaminated with faecal matter are the major source of infection.
Disease # 6. Ascariasis:
Causative agent of ascariasis is Helminthes (Ascaris lumbricoides) which is an intestinal parasite commonly known as roundworm.
Symptoms Includes internal bleeding, muscular pain, fever, anaemia and blockage of the intestinal passage.
Disease # 7. Elephantiasis (Filariasis):
Causative agents of elephantiasis are worms Wuchereria bancrofii and Wuchereria malayi and their transmitting agent is a female mosquito vector (Culex).
Symptoms:
Chronic inflammation occurs in which they live for many years mostly in the lymphatic vessels of the lower limbs. Genital organs are also deformed sometimes. Female Culex mosquito is the vector.
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Disease # 8. Ringworms:
Causative agent of ringworms are fungi like Microsporum, Trichophyton and Epidermophyton.
Symptoms include dry, scaly lesions on various parts of the body such as skin, nails and scale with intense itching.
Ringworms are generally acquired from soil or by direct contact with contaminated articles used by infected person.
Heat and moisture help in growth of the fungi in the folds of the skin. They generally spread via using towels, clothes or even the comb of infected individuals.
