To improve the community health it is very important that the human excreta is disposed of in a sanitary manner. If excreta are disposed of hygienically the public can be protected from majority of diseases and crores of rupees can be saved which are spent every year in controlling various diseases.
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Human excreta are a major source of infection as it contains pathogenic micro-organisms, viruses, protozoa, helminthes parasites and their eggs. The faces of a patient contain various disease producing agents which are transmitted to a new host through water, food, flies, and contaminated fingers and soil. It directly pollutes the water and food which when ingested by a healthy person leads to the production of diseases.
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The diseases which are associated with improper disposal of excreta include typhoid, paratyphoid, fever, diarrhea, dysentery, cholera, poliomyelitis, viral hepatitis, round worm and hook worm infestation etc.
In villages people go to fields for defecation and least care is paid towards the proper disposal of human excreta. That is why the incidence of above mentioned diseases are more in villages. The villagers do not have hygienic sense.
The children defecate in or near the houses and flies sit over the faeces. Again they sit on the food and even milk feeders of the kids and contaminate them with faecal matter attached to their wings and legs thus easily spread the disease.
The chain of spreading the diseases can be broken easily if faecal matter is promptly disposed of in an hygienic manner. In this way the excreta will not contaminate water, food and soil and community health will improve.
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For disposal of human excreta there are several methods in use. Some of which are applicable to rural and unsewered areas and others are applicable to sewered areas. For this purpose following methods are used:
(a) Rural and unsewered areas:
(i) Service type
(ii) Non-service type
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(b) Sewered areas:
Water carriage system and sewage treatment
(a) Service Type of Latrines:
In rural and unsewered area the disposal of human excreta is a great problem. The night soil (human excreta) is collected by manual labour from privies (structure for depositing excreta in private household) and latrines (similar structure for public use).
In privies or latrines the excreta is collected in buckets or pails which are removed by sweepers and transferred to night soil carts for transportation to distant places of final disposal.
This system is called service type or conservancy system and such latrines are called service type of latrines. This is an old system, though it is being discarded and replaced by water carriage system but still it is used in villages and small towns where water carriage system is not provided by the authorities due to high costs of laying down sewers and water carriage system.
Conservancy system is not a good system from health point of view and has the following drawbacks:
(i) Night soil is exposed to flies even in carts.
(ii) There is soil and water pollution.
(iii) Buckets and pails are never emptied satisfactorily. Some quantity of night soil always remains sticking to the buckets.
(iv) It gives highly objectionable smell especially when the latrines are cleaned.
(v) Buckets and pails often get corroded and require frequent replacement which is a costly affair.
(vi) A large number of manual labourers are required hence not economical from financial point of view.
(vii) Above all it is against the human dignity that human beings are employed for removing the excreta of other human beings. So the service type of latrines are discarded and discouraged and efforts are made to convert such latrines to sanitary latrines which do not require any service in its disposal.
Non-Service Type Latrines:
Non-service types of latrines include:
(a) Bore whole latrine
(b) Dug well latrine
(c) Water seal latrine
(d) R.C.A. latrine, (Research Cum Acton Project, Government of India).
(e) Shallow trench latrine
(f) Deep trench latrine.
(b) Water Carriage System:
Water carriage system is also known as sewerage system. In this system the human excreta is collected and removed along with waste water through underground pipes known as sewers to a distant place for final disposal. The sewage includes excreta, urine, waste water from Souses, commercial establishments, factories, stables, and rain water.
Water carriage system is a method of choice but it requires piped water system for flushing the latrines; there can be no sewerage system without a piped water supply. It requires lot of money to lay down the underground system of pipes and to maintain the system. This method has number of advantages that:
(i) It requires no manual labour for removal of human excreta.
(ii) The latrines always remain clean.
(iii) There is no nuisance of smell or flies.
(iv) Spreading of diseases by insects, rodents or animals are checked.
(v) There can be overall improvement of community health.
Medical Entomology:
There are a large number of arthropods present in the environment of man and they constitute the largest group among the invertebrates. Many of them are harmful, some are useful and others are of no significance. A few arthropods bite or infest man and transmit diseases.
A study of these arthropods (mainly insects) is known as medical entomology. The word arthropod is derived from two words author means jointed and pods means legs. So the main characteristic of all arthropods is that they have many joints in their legs.