Human Disease Communicable Disease

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Introduction to human disease and ways of prevention of communicable disaese which can be tranfered from person to person it is bacterial disease characterized by continued classical fever .It is world wide I.E. cosmopolitan in distrubition and common disease of rural areas
Human Disease Communicable Disease

Communicable disease

these are the disease which can be transmitted from person to person :-


it is bacterial disease characterized by continued classical fever .It is world wide I.E. cosmopolitan in distrubition and common disease of rural areas . It caused by bacillus bacterium called salmonella typhi . It is commonly found in intestine of man .so typhoid fever is also called enteric fever.Ulceration of peyer patches with instestinal bleeding and ulceration can be seen as well. Gall bladder colonization produces a chronic carrie state . Choronic infection also may affect the joints , bone , meninges and other site.

Causative organism
they are Salmonella typhi:-

mode of transimition

1 direct or indirect contact with patient or carrier.
2 the product of vehicles spread and contaminate food and water.
3 the germs from infected foods and water gets entire enters into the alemintary cannal and causes lesion in patches in the small intestine .
4 Raw fruits and vegetables are also important factors.
5 Milk and milk product are also causative agents , beef , egs and poultry are soe factors.
Incubation period
it is virile, average is 2 weeks
Following clinical feature appers during typhoid fever
- headach , classic typhoid fever and pain.
- Lesion of intestine mucosa.
- haemorrhage and ulceration in intestine.
- tongue is coated centally and Rose coloured rash on chest and upper abdomen.


widal test come positive during 2nd week.
– antibittics like Ampicillin and chloramphencol.
1 proctection , purification and chlorination of public water.
2 consstruction of safe private supplies .
3 Sanitary disposal of human excreta .
4 fly control by screening and spraying products.
6 health eductation.
7 awareness.
8 immuniztion with vaccine .

Its is communicable chronic granulomatous disese . tuberculosis is world wide i. e. cosmopolitan in distribution. It usually involves lungs but may effect any organ or tissue into the body .Typically the centres of tubercular granulomas undergoes caseous necroisis . It is very serious chronic bactrerial disese and an important cause of death in most part of world . It is caused by Mycrobacterium tuberculosis. parasite mainly attacks the lungs so called pulmonary T.B.
Causative organism
tuberculosis is caused by mycobacterium tuberculosis . It attacks all age group but epidemics have been reported among mine works , factory , gaments and children in crowded classroom.
Mode of transmission
1 contact with patients with open lesion .
2 Air borne roué.
3 through throat while coughing and sneezing.
4 Bovine tuberculosis results from tuberculoous course .
5 bovine tuberculosis result from ingestion of unpasteurized of milk or dairy products of tuberculosis.

- causative organism bacillus tuberculoss was discovered by Robert Koch in 1882 , lungs are the favourite site of infection
incubation period.
it is 4 to 6 weeks the fist 6 to 12 month after infection is the most harzdous period .
clinical Feature
primary infection usually goes unnoticed clinncially lessons heal spontaneously , leaving no residual change except pulmonary or tacheobranchial lymph node calcification.But occasionally lead to pleurisy or to dissemination of bacilli with millary or other extra pulmonary involvement .Serious manifestation develop most often in infant . Other symptoms are constant coughing , chest pain , bloody sputum, low grade fever and sweating in the day and night , loss of body weight , fatigue , hoarseness of voice etc may apper.
It is by roentgenogram is confied by demonstration of tubercle bacilli in sputum.
By using DOTS.
Isoniazed , streptomycin continued for one or more years .


Ascriasis is highly prevalent disease aucsed by the largest nematode Ascaris lumbricoides . When fresh from the intestine , it is light brown or pink in colour but it gradually change to white. It is most frequently seens in the stools of children the male A.lumbricoides measure about 15 to 25 cm in lengh , the female is longer and stouter measuring 25 to 40 cm in length .the eggs laying capacity of mature femal Ascaris has been found to be enormous, liberating about 200 000 eggs daily . the eggs liberated by fertilized female pass out of human host with the feaces and may remain alive for several day
1 by swallowing ripe eggs with raw vegetable cultivated on soil fertile by infection .
2 infection also occurs by drinking contaminated water .
3 among children playing in contaminated soil , there is also hand to mouth transfer of eggs by dirty figers .
4 Infection may also occur by inhalation of desiccated eggs in the dust reaching the pharynx and swallowed.
5 A rhabdition is developed from unsegmented ovum within the eggs –shell in 10 to 41 days in the soil.
Mot and route of migration :-
1 when ingested food ,drinks, or row vegetables , the embryonated eggs pass down to the duodenum where the digesion juices weaken the egg shell.
2 Splitting of the eggs shell ouccurs and the rhabdititifrom larvae are libted in the upper part of the small intestine .
3 the newly atched larvae burrow their way through the mucous membrane of the small intestine and are carried by the portal circulation.
4 breaking through the capillary wall they reach the lung alveoli . from the lung alveoli the larvae crawl up the bronchi and trachea , then are propelled into the larynx and pharynx and are once more swallowed .
5 the larvae pass down the oesophagus to the stomach and localize in the upper part of the instestine.
- the larvae on reaching habitat grow into outside while within the egg shell two in the lungs and one in the intestine .
- Symptoms of Ascris infection those produced by migrating larvae and those produced by adult worms.
1 symptoms due to the migrating larvae :-
- in heavy infection typical symptoms of pneumonia such as fever , cough and dyspnoea may appear.
- urticarcial rash and eosinophilias are seen in such case.
2 symaptoms due to adult worm :-
with the adult worms inhabiting the intestine, the patient complains of abdominal pains ,vomiting , headache, irritability , dizziness and night terrors. Sometime there is Ascaris causing appendicitis .Obstructive jaundices and acute harmrorrhagic pancreatitis has been seen as well
Prevention and treatment :-
- treatmeant of ascaris using drugs Albendazole , mebendazole.


Acquierd immune deficiency syndrome recognized 1st in USA with several reports in 1981 . it is cause by HIV , discovered by Montahiner et. al.

structure of HIV

- Virus has single stranderd RNA , with reverse transcription .It is surrounded by glycoprotein coat, double lipid membrane and two protein coats.It is diploid as it has two copies of RNA molecule .IT is a retrovirus ,which means that its genetic material is RNA which can make a DNA copy of itself with the help of reverse RNA and transcription of RNA .here it produce DNA copy itself by reverse transcription. The virus is belived to be mutant of a strain that infected the African green monkey .This is why no effective vaccne could be prepared for AIDS.

Incubation period

- the incubation period of AIDS ranges between 6 month to over 7 years – average is 20 months.
Three stages of AIDS infection :-
1 Asymptomatic carrier :-
- some of newly infected person develop fever, chill,ache,swollen lymph lands and the symptoms soon disappears.
2 ARC (Aids related complex):-
- it is mild form of AIDS and the symptoms are swollen lymph nodes, persistent cough ,recurrent fever , night sweats and nervous causes death .
- Aids can be prevented by using condoms ,avoiding sex with prostitute, intravenous drugs use etc.

HIV test – ELISA.The other test is western blot , Azidothymidine is the drugs that is used to treat the disease it prevent the reproduction of HIV in the T- cell


Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069

Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.

Jorden, S.L. principle of biology. 2nd edition . Kathmandu: Asmita book Publication, 2068.2069.

Things to remember
  1. It caused by bacillus bacterium called salmonella typhi . It is commonly found in intestine of man .so typhoid fever is also called enteric fever.
  2. widal test come positive during 2nd week 
  3.  proctection , purification and chlorination of public water
  4.  consstruction of safe private supplies 
  5.  Sanitary disposal of human excreta 
  6.  fly control by screening and spraying products 
  • It includes every relationship which established among the people.
  • There can be more than one community in a society. Community smaller than society.
  • It is a network of social relationships which cannot see or touched.
  • common interests and common objectives are not necessary for society.

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