mcga-shs_capt_guide_chap5.pdf

CHAPTER 5

Causes of disease

This chapter deals with common-sense measures and some

necessary precautions which should be taken to preserve the

health of those aboard ship and to prevent the spread of

disease where it has occurred. Of the many causes of disease,

infection by living organisms is the commonest and an

understanding of their mode of spread is necessary if healthy

living and working conditions are to be maintained.

Microbes (germs) can be classified in broad terms as

viruses, bacteria, and fungi. They are widely disseminated

throughout nature and although most of them are not

harmful to mankind certain organisms may invade the body

and produce particular diseases. They gain entry to the body,

usually through the nose or mouth or the broken skin.

Infection can take place directly from person to person or it

may be conveyed indirectly in air, water or food or by a

parasite carrier (such as an insect).

The viruses of influenza, that of the common cold and

much more rarely Legionnaires disease are examples of air-

borne infection which is spread when the sufferer coughs or

sneezes.

Typhoid fever is an example of a water-borne bacterial

infection. The excreta of infected persons contaminate water

supplies. Hence the necessity for safeguarding the water

supply for washing as well as for drinking at all times.

Examples of two well-known bacterial diseases brought

about by personal contact are syphilis and gonorrhoea.

A number of diseases are conveyed by carriers. The plague

germ is conveyed by the bites of fleas living on the rat. Typhus

is conveyed in similar manner by lice. Malaria and yellow

fever organisms inhabit the salivary glands of the mosquito

and are injected into the blood when the mosquito bites.

Flies, because of their behaviour, are very prone to convey

disease germs from filth to food.

Ringworm is an example of a disease caused by a fungus

through contact.

Causes of disease

Potable water

Food

Catering staff: personal

hygiene

General cleanliness on

board ship

Insecticides

Disinfection

Isolation

Ventilation

Port health clearance

Preventing heat illness

Exposure

Lifting heavy weights

Exercise and boredom

Dressings, bandages,

slings and splints

First aid satchels and

boxes

Severe bleeding

Unconscious casualty

Burns and scalds

Suffocation (asphyxia)

Strangulation

Choking

Epileptic fits

Shock

Bleeding

Wounds

Fractures

Dislocations

Head injuries

Transportation

Potable water

This covers water used for drinking, cooking, the washing of

cooking and eating utensils, and water used for general

cleaning and bathing. Additional advice is given in Merchant

Shipping Notices M.1214 and M1401.

Fresh water should be free from causes of infection and be

bright, clear and virtually colourless. It should be aerated,

that is, it should bubble when shaken, otherwise it has an

insipid taste.

The Merchant Shipping Crew Accommodation Regulations

1997 and Merchant Shipping Crew Accomodation (Fishing

Vessels) Regulations 1975 require all fresh water produced

on board ship to be disinfected automatically. Electro-silver

ionisation systems are acceptable for this requirement.

Fresh water storage tanks

These water tanks are coated internally with an anti-

corrosive material which will not contaminate the water. It is

recommended that the tanks should be emptied annually, or

CHAPTER 1

Introduction

Priorities

General principles

of first aid

General assessment

of the situation

THE SHIP CAPTAIN’S MEDICAL GUIDE

more frequently if contamination is suspected, for inspection and maintenance after which

they should be thoroughly scrubbed and flushed out, and the whole water system disinfected

by chlorine (see below). Anyone entering any potable or washing water tanks should wear

clean clothing and footwear, and should not be suffering from skin infections, diarrhoea or any

communicable disease.

Disinfection of the fresh water tanks and distribution system by super-

chlorination

It is recommended that the storage tanks and the whole of the fresh water system should be

disinfected at intervals of not more than twelve months even if the quality of the water that has

been used to fill them is not suspect.

The chlorine compounds that may be used for disinfecting are chlorinated lime, high-test

hypo-chlorite or commercially prepared sodium hypo-chlorite solution.

NOTE. Before being diluted by the water in the potable water system these compounds:

n are dangerous to eyes and skin – see IMO Medical First Aid Guide;

n deteriorate on exposure to air – they should, therefore, be purchased in small containers

which should be sealed tightly after use;

n should be kept in a cool, dry and dark place, but where they can be easily seen and removed

when needed or there is a likelihood of fire;

n Calcium Hypochlorite – is liable to spontaneous combustion if not stored as above, or if in

contact with animal, vegetable, plastic or other inorganic material;

n Chlorinated Lime – is liable to facilitate fires.

See also the International Maritime Dangerous Goods Code.

Determine the volume of water necessary to fill the tanks and distribution system completely

and the amount of chlorine compound required. The latter can be calculated from the

manufacturer’s instructions or from the table or formula shown below.

Amount of chlorine compound required for a 50–ppm (50-mg/litre solution)

Amount of chlorine compound required

Capacity of system

Chlorinated

High-test

Sodium Hypochlorite

(including tanks

lime

calcium hypochlorite solution

and piping)

25%

70%

10%

for each:

litre

litres

1,000 litres

0.2

0.08

0.5

5,000 litres

0.4

2.5

10 tonnes

2.0

0.8

10.0

5.0

NOTE.

1. Before using the above chlorine compounds check that the percentages are as in table above

– if not adjust the quantity you use accordingly.

2. When chlorine compounds or solutions other than those mentioned in the table are used the

dosages should be:

for powders:

70 x dosage in 70% column

percentage of chlorine in compound

for liquids:

5 x dosage in 5% column

percentage of chlorine in liquid

Chapter 5 CAUSES AND PREVENTION OF DISEASE

Chlorinated lime

Place the required amount of chlorine compound in one or more clean, dry buckets (or drums).

Add a small amount of water to each bucket and mix the lime into a thick paste. Dilute the paste

by adding warm water gradually, and stirring constantly, until there are about six litres of

solution in each bucket. Allow the solution to stand for 30 minutes, so that the undissolved

particles may settle to the bottom. Decant the clear liquid (the chlorine solution) and, if

necessary, filter it through muslin or cheese-cloth prior to putting it into the tank

Chloride of lime may be sold as:

Chloride of Lime

(Stablochlor)

Chlorinated Lime Calx Chlorinata

British

Calx Chlorinata

U.S.A.

Chlorure de Chaux

Sel de Javelle

French

Chlorkalk

Calcaria Chlorata

German

Calx Chlorata

Danish, Norwegian and Swedish

Cloruro di Calce

Italian

Hipoclorito Calcico Clorurado

Spanish

Hipoclorito de Calcio

Mexican

Cal Chlorada

Portuguese

High-test calcium hypochlorite

Place the required amount of the compound in one or more clean, dry metal buckets (or drums).

Add fresh water and stir until the powder is dissolved (disregard any slight turbidity).

Sodium hypochlorite solution

No preparation is required.

Procedure

Introduce the chlorine solution into nearly empty fresh water tanks and immediately fill them to

overflowing with fresh water. The turbulence of the incoming water will ensure adequate mixing.

Open the taps and outlets of the fresh water distribution system nearest the storage tanks,

and allow the water to flow until you can smell chlorinated water. Then close those taps and

outlets, and, working outwards from the tanks, open and close successively the other taps and

outlets until they have all been flushed with chlorinated water. Care should be taken to ensure

that the pressure tank is filled with chlorinated water.

In flushing the system a certain amount of the chlorinated water will have been drawn from

the storage tanks. They should be refilled to overflowing, and chlorine solution should be

added to make up the concentration in the tanks to 50 ppm (50 mg/litre), ie if you have drained

off 380 litres of water you will need to add, for example, an additional 75 grams of chlorinated

lime 25% solution.

The chlorinated water should be allowed to remain in the storage tanks and the distribution

system preferably for twelve hours but not less than four hours. After the contact period the

tanks and distribution system should be drained and flushed with potable water until the water

no longer has an objectionable taste of chlorine.

Hoses

Hoses, where carried on board for the purposes of transferring water from shore mains supply

or water barges, should be used solely for this purpose. They should also be suitably marked

and, after use, should be drained and capped at both ends. The hoses should be stowed away

from the deck in a place free from contamination.

THE SHIP CAPTAIN’S MEDICAL GUIDE

Disinfection of hoses should be carried out as a routine measure every 6 months – or

whenever any contamination is suspected – with a chlorine solution of 100 ppm (100 mg/litre).

This should be allowed to stand in the completely filled hose for a period of at least one hour.

A 100 ppm strength solution can be obtained by doubling the quantities of chlorine shown

in the formula for the 50 ppm hyper-chlorine solution used for disinfecting ships’ water tanks

which is shown in the above table.

Taking water on board

Before taking on water check that the delivery cocks on the shore and the receiving point on

the ship are properly cleaned. Examine the hose to ensure that it is clean, in good working

order, and free from leaks (germs can get in through leaks in the hose). Ensure that the ends of

the hose do not drag across the deck.

If you are taking water for potable purposes from a source which is new to you or about

which you have doubts, you should ask the British Consul or your agents for advice as to

whether the water is likely to contain germs or harmful minerals such as lead. Remember that a

bright, clear, sparkling water may easily contain either deadly organisms such as cholera, or

harmful minerals such as lead. It is unlikely that fresh water taken on board will contain

sufficient (if any) chlorine to ensure complete safety.

It is recommended therefore that the chlorination of water outlined in the following

paragraph be carried out in all vessels, including those equipped with distillation units and/or

ultra violet sterilizers.

Routine treatment of fresh water by chlorine

All fresh water taken from shore or water barge for drinking or washing should be chlorinated

on loading to ensure a residual free chlorine content of 0.2 ppm at all outlets throughout the

ship’s freshwater distribution system. As free chlorine in a ship’s water system is progressively

lost in passing through the system it will, in practice, be necessary to chlorinate the water held

in the storage tanks to a higher concentration than 0.2 ppm. Finding the best actual level of

initial concentration may be a matter of experiment as much will depend on the size of the tank

or the distribution system.

If chlorine test facilities are available, samples of treated water should be taken at tap and

shower outlets at [weekly/monthly] intervals, preferably using outlets that would otherwise

not be used (e.g. in unoccupied cabins) in order to reduce the presence of standing water in the

system. The result of these tests should be used to adjust the concentration of chlorine in the

system to obtain a minimum of 0.2 ppm at the outlets.

It should be remembered however that if drinking water supplies pass through charcoal

filters close to the outlets, there will be no free chlorine at these points.

It is recommended that, initially a concentration of 0.5 ppm in the storage tanks is aimed for

and this may be achieved by using an automatic chlorination unit in the ship’s deck filling line or

by the traditional manual method using the manufacturer’s instructions for the chlorine

compound in use or by calculating the quantities required by use of the following table or

formula:

Amount of chlorine compound required for a 0.5 ppm chlorine solution

Amount of chlorine compound required

Chlorinated

High-test

Sodium Hypochlorite

lime

calcium hypochlorite solution

25%

70%

10%

for each:

1,000 litres

0.8

10 tonnes

100

Chapter 5 CAUSES AND PREVENTION OF DISEASE

Water making plant

All water made from seawater by low pressure evaporators or reverse osmosis plant requires to

be treated by means of an automatic chlorination unit adjusted to give the required

concentration on delivery to the storage tanks, or by an elctro-silver ionisation system.

Ultra violet sterilizer units should only be used as a supplement to chlorination.

Maintenance of distribution system

The various elements of the freshwater system which might include sand filters, evaporators,

reverse osmosis plant, softeners etc., should be inspected, cleaned, flushed out, back washed,

recharged or items replaced where appropriate, in accordance with the maker’s instructions

and it is recommended that a Freshwater System Maintenance Log be kept itemising each

principle unit in the system.

Food

A balanced diet is essential for the maintenance of good health and should contain the correct

proportions of protein, carbohydrate, fats, vitamins and essential minerals such as iron. It

should be varied in accordance with the needs of the consumers and the climate in which they

are working. Protein is derived from such foods as meat, fish and beans; carbohydrates from

cereals and bread; and vitamins and essential minerals from all of these and from fruit and

vegetables.

It is also essential to avoid contamination in the food preparation area. Raw food, especially

meat, should be kept separate from cooked products. Separate utensils and cutting boards etc.

must be kept for each and stored separately. The food handler must wash between handling

different foods and especially after handling raw meat and poultry; cooked food should be

manipulated by tools and utensils and not by the hands; and work surfaces and equipment

must be cleaned thoroughly and disinfected efficiently. Cleaning equipment must also be

disinfected adequately.

Vegetables

Fresh vegetables, such as lettuce, radish, carrot, beetroot, celery and spinach should never be

eaten, cooked or raw, without first being thoroughly washed in clean running water.

In many countries such crops are fertilised with human excreta and are, therefore,

potentially dangerous as a source of transmission of intestinal disease such as typhoid,

dysentery and intestinal parasites.

Wherever practicable, boil vegetables before serving. Where the origin of any vegetable to

be eaten raw is not known, it should be soaked for two minutes in a solution of 3.5 g of

stabilised chloride of lime to 5 gallons of water followed by at least two thorough rinsings in

potable water.

Fruit

Fruit, such as oranges, bananas, grapefruit, that must be peeled before eating is generally safe.

Fruit, such as apples, tomatoes, grapes, dates, that is not generally peeled, is a frequent source

of diarrhoea. Before eating they should be treated in the way recommended for raw

vegetables.

Canned foods

Each tin should be carefully examined before being opened. Never accept or use tins which are

rusty, dented, damaged or blown.

Bacteria in food

Bacteria require moisture and warmth for growth. The most favourable temperature for

growth is normal body heat, although most will thrive at temperature between 15 o C and 45 o C.

Bacteria can multiply very fast in favourable conditions.

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: