Human health and Infectious diseases
Biology

Human health and Infectious diseases


Health is a state of complete physical, mental & social well-being. Health is affected by genetic disorders, Infections, change in life style (food, water, rest, exercise, habits etc).
Diseases may be Infectious or Non-infectious.
Pathogens: Disease (Infectious) causing organisms.  Parasites are pathogens as they harm the host by living in or on them.
COMMON INFECTIOUS DISEASES IN MAN

1. BACTERIAL DISEASES

a.    Typhoid: Pathogen is Salmonella typhi.
·   Mode of transmission: It enters the small intestine through food and water and migrates to other organs through blood.
·   Symptoms: Sustained high fever (39o-40o C), weakness, stomach pain, constipation, headache & loss of appetite. Intestinal perforation and death may occur.
Widal test is used for confirmation of the disease.
b.   Pneumonia: Pathogen is Streptococcus pneumonia & Haemophilus influenza.
·   Mode of transmission: Inhaling the droplets/aerosols released by an infected person. Sharing glasses and utensils with an infected person.
·   Symptoms: Infects lung alveoli. The alveoli get filled with fluid leading to respiratory problems. Fever, chills, cough, headache. Severe cases: Lips and finger nails turn gray to bluish colour.

2. VIRAL DISEASES
a.    Common cold: Pathogen isRhinoviruses.
·   Mode of transmission: Inhaling droplets resulting from cough or sneezes. Through contaminated objects.
·   Symptoms: Infects nose & respiratory passage. Nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness etc. Last for 3-7 days.

3. PROTOZOAN DISEASES
a.    Malaria: Pathogen isPlasmodium sp. (P. vivax, P. malariae, and P. falciparum).
·   Mode of transmission: Anopheles mosquito biting.
·   Symptoms: Haemozoin causes chill and high fever recurring every 3-4 days.

Life cycle of Plasmodium










b.   Amoebiasis (Amoebic dysentery): Pathogen isEntamoeba histolytica.
·   Mode of transmission: Houseflies (mechanical carriers) transmit parasites from faeces to food & water.
·   Symptoms: Constipation, abdominal pain and cramps, stools with excess mucous and blood clots.

4. HELMINTH DISEASES
a.    Ascariasis: Pathogen isAscaris (Intestinal parasite).
·   Mode of transmission: Soil, water, vegetables, fruits etc. contaminated with faeces containing eggs of parasites.
·   Symptoms: Internal bleeding, muscular pain, fever, anaemia and blockage of intestinal passage.
b.   Filariasis (Elephantiasis): Pathogen isFilarial worms or Wuchereria (W. bancrofti & W. malayi).
·   Mode of transmission: Bite of female Culexmosquito.
·   Symptoms: Filarial worms live in lymphatic vessels (usually of lower limbs). It causes chronic inflammation of the organs in which they live for many years. Limbs and genital organs may be deformed.

5. FUNGAL DISEASES
a.    Ring worms: Pathogens are Microsporum, Trichophyton & Epidermophyton. They are seen in groin, b/w toes etc.
·   Mode of transmission: From soil or by using towels, cloths, comb etc. Heat and moisture help fungi to grow.
·   Symptoms: Appearance of dry, scaly lesions on various body parts such as skin nails and scalp. Intense itching.

Other infectious diseases

Bacterial Diseases

Disease
Pathogen
Transmission
Dysentery
Shigella
Contact, Contaminated food and water
Plague
Pasteurella pestis
Rat fleas
Diphtheria
Corynebacterium diphtheriae
Contaminated food, Direct contact
Cholera
Vibrio cholerae
Food & water contam-inated with faeces
Tuberculosis
Mycobacterium tuberculosis
Droplets from patient / carrier
Tetanus
Clostridium tetani
Contamination of wound by bacteria
Whooping cough
Bordetella pertussis
Contact, Droplets
Leprosy
Mycobacterium leprae
Direct contact
Anthrax
Bacillus anthrasis
Contact with cattle
Weil?s disease
Leptospira
Contact with rodents, dogs etc.

Viral Diseases

Disease
Pathogen
Transmission
Rabies
Rabies virus
Rabid dogs etc
Dengue
Dengue virus
Aedes mosquito
Influenza
Influenza virus
Coughing & sneezing
Measles
Rubeola virus
Droplets
German measles
Rubella virus
Close contact
Mumps
Mumps virus
Air borne droplets
Chicken pox
Varicella zoster
Air borne droplets
Small pox
Variola virus
Direct contact
Polio
Polio virus
Faeces & Air
Chikungunya
Chikungunya (CHIK) Virus
Aedes mosquito
Avian flu
H5N1 virus
Contact with infected poultry. Air borne spread
H1N1(Swine flu)
H1N1 virus
Contact with pigs, cough & sneeze of infected person.

PREVENTION AND CONTROL OF DISEASES

1.   Personal hygiene

Keep the body clean. Use clean drinking water, food etc.

2.   Public hygiene
a.    Proper disposal of wastes and excreta.
b.    Periodic cleaning and disinfection of water reservoirs, pools, cesspools and tanks.
c.    Avoid contact with infected persons or their belongings (to control air-borne diseases).
d.    Standard practices of hygiene in public catering.
e.    Control and eliminate the vectors (e.g. mosquitoes) and their breeding places.
-    Avoid stagnation of water.
-    Regular cleaning of household coolers.
-    Use of mosquito nets.
-    Introduce larvivorous fishes like Gambusia in ponds.
-    Spraying insecticides in ditches, drainage and swamps.
-    Doors and windows should be provided with wire mesh to prevent entry of mosquitoes.
These precautions can avoid vector borne diseases like Malaria, Filariasis, Dengue & Chikun gunya.





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