mcga-shs_capt_guide_chap6.pdf

CHAPTER 6

Communicable diseases are those that are transmissible from

one person, or animal, to another. The disease may be spread

directly, via another species (vector) or via the environment.

Illness will arise when the infectious agent invades the host,

or sometimes as a result of toxins produced by bacteria in

food.

The spread of disease through a population is determined

by environmental and social conditions which favour the

infectious agent, and the relative immunity of the

population. An outbreak of infection could endanger the

operation and safety of the ship. An understanding of the

disease and the measures necessary for its containment and

management is therefore important.

Infectious agents

Modes of transmission

Definitions and terms

used

Symptoms and signs

General management

and treatment

Anthrax

Cellulitis

Chickenpox (Varicella)

Cholera

Dengue fever

Diphtheria

Enteric fever (typhoid

and para-typhoid fevers)

German measles

(Rubella)

Glandular fever

Hepatitis (viral)

Influenza

Malaria

Measles

Meningitis

Mumps

Plague

Poliomyelitis

Rabies

Scarlet fever

Tetanus

Tuberculosis

Typhus fever

Whooping cough

(Pertussis)

Yellow fever

Sexually transmitted

diseases including HIV

(AIDS)

NOTE. Other communicable

diseases such as Lassa Fever do

not fall within the competence

of this book. When in doubt

notify the Port Health Officer.

Infectious agents and examples of

diseases

The organisms that cause disease vary in size from viruses,

which are too small to be seen by a light microscope to

intestinal worms which may be over a metre long. The groups

of infectious agents are listed with examples of diseases they

cause.

Bacteria

Pneumonia, tuberculosis, enteric fever, gonorrhoea

Viruses

Measles, varicella, influenza, colds, rabies

Fungi

Ringworm, tinea pedis (athlete’s foot)

Protozoa

Malaria, giardia

Metazoa

Tapeworm, filariasis, onchcerciasis (river blindness),

hookworm

Prions

Kuru, Creutzfeld-Jacob disease, Bovine spongiform

encephalopathy (BSE)

Modes of transmission

Direct transmission

Direct contact with the infected person as in touching,

kissing or sexual intercourse

Droplet spread through coughing sneezing, talking or

explosive diarrhoea

Faecal-oral spread when infected faeces is transferred to

the mouth of a non infected person, usually by hand.

Indirect transmission

Indirect transmission of infectious organisms involves

vehicles and vectors which carry disease agents from the

source to the host.

THE SHIP CAPTAIN’S MEDICAL GUIDE

Vehicles are inanimate or non-living means of transmission of infectious organisms. They

include:

Water. If polluted, specifically by contaminated sewage. Water is the vehicle for such

enteric (intestinal) diseases as typhoid, cholera, and amoebic and bacillary dysentery.

Milk is the vehicle for diseases of cattle transmissible to man, including bovine tuberculosis,

brucellosis. Milk also serves as a growth medium for some agents of bacterial diseases such

as campylobacter, a common cause of diarrhoea.

Food is the vehicle for salmonella infections (which include enteric fever), amoebic

dysentery, and other diarrhoeal diseases, and poisoning. Any food can act as a vehicle for

infection especially if it is raw or inadequately cooked, or improperly refrigerated after

cooking, as well as having been in contact with an infected source. The source may be

another infected food, hands, water or air.

Air is the vehicle for the common cold, pneumonia, tuberculosis. influenza, whooping

cough. measles. and chickenpox. Discharges from the mouth. nose, throat, or lungs take the

form of droplets which remain suspended in the air, from which they may be inhaled.

Soil can be the vehicle for tetanus, anthrax, hookworm. and some wound infections.

Fomites. This term includes all inanimate objects, other than water, milk, food, air, and soil,

that might play a role in the transmission of disease. Fomites include bedding, clothing and

the surfaces of objects.

Vectors are animate or living vehicles which transmit infections in the following ways:

Mechanical transfer. The contaminated mouth-parts or feet of some insect vectors

mechanically transfer the infectious organisms to a bite-wound or to food. For example,

flies may transmit bacillary dysentery, typhoid, or other intestinal infections by walking

over the infected faeces and later leaving the disease-producing germs on food.

Intestinal harbourage. Certain insects harbour pathogenic (disease causing) organisms in

their intestinal tracts. The organisms are passed in the faeces or are regurgitated by the

vector, and the bite-wounds or food are contaminated. (e.g. plague, typhus.)

Biological transmission. This term refers to multiplication of the infectious agent during its

stay in the body of the vector. The vector takes in the organism along with a blood meal but

is not able to transmit infection until after a definite period, during which the pathogen

changes. The parasite that causes malaria is an example of an organism that completes the

sexual stages of its life cycle within its vector, the mosquito. The virus of yellow fever also

multiplies in the bodies of mosquitoes.

Terms used in connection with communicable diseases

A carrier is a person who has the infection, either without becoming ill himself or following

recovery from it.

A contact is a person who may have been in contact with an infected person.

The incubation period is the interval of time that elapses between a person being infected with

any communicable disease and the appearance of the features of that disease. This period is

very variable and depends upon the infectious agent and the inoculum (the amount of the

infectious agent).

The isolation period signifies the time during which a patient suffering from an infectious

disease should be isolated from others.

The period of communicability is the time during which a patient who may be incubating an

infectious disease following contact can communicate the disease to others.

The quarantine period means the time during which port authorities may require a ship to be

isolated from contact with the shore. Quarantine of this kind is seldom carried out except when

serious epidemic diseases, such as, for instance. plague. cholera, or yellow fever are present or

have recently occurred on board.

Chapter 6 COMMUNICABLE DISEASES

Symptoms and signs

In reality it is often very difficult to make an accurate diagnosis of an infectious disease without

laboratory investigations. It may be possible if there are very specific features such as a rash

(varicella) or cluster of suggestive features (regular fever, enlarged spleen and history of

mosquito bites in an endemic area). Because of the difficulty in making an accurate diagnosis on

board ship you may have to give a variety of treatments each directed at different infectious

agents.

Onset

Almost all communicable diseases begin with the patient feeling unwell and perhaps a rise in

temperature. This period may be very short, lasting only a few hours (meningococcal sepsis), or

more prolonged (hepatitis). In some diseases the onset is mild and there is not much general

disturbance of health, whereas in others it is severe and prostrating. During the onset it is rarely

possible to make a diagnosis.

The rash

The diagnosis of some communicable diseases is made easier by the presence of a characteristic

rash. In certain diseases (e.g. scarlet fever) the rash is spread evenly over the body, in others it is

limited to definite areas. When examining an individual suspected to be suffering from a

communicable disease, it is of great importance to strip him completely in order to get a full

picture of any rash and its distribution.

General rules for the management of communicable diseases

Isolation

The principles of isolation are described in Chapter 3 and Chapter 5. If you have a suspicion that

the disease with which you are dealing is infectious it is advisable to invoke isolation

precautions as soon as possible.

Treatment

An essential element in treatment is maintaining the patient’s well being. This is achieved

through good general nursing and it is important to ensure that the patient does not become

dehydrated.

Advice on specific medical treatment for infectious diseases which are likely to respond to

specific drugs is given under the sections on treatment for the individual diseases. You may also

be advised to administer drugs to prevent secondary infection occurring.

See Chapter on General Nursing and on how to reduce a high fever.

Diet

Diet will very much depend on the type of disease and severity of fever. Serious fever is

invariably accompanied by loss of appetite and this will automatically tend to restrict diet to

beverages such as water flavoured with lemon juice and a little sugar or weak tea with a little

milk and perhaps sugar.

Essential basic rules

Isolate. If anyone suffers from a temperature without obvious cause it is best to isolate him

until a diagnosis has been made.

Strip the patient and make a thorough examination looking for any signs of a rash in order

to try to establish the diagnosis.

Put him to bed, and appoint someone to look after and nurse the patient.

Give non-alcoholic fluids in the first instance.

If his temperature exceeds 39.4C make arrangements for tepid sponging.

THE SHIP CAPTAIN’S MEDICAL GUIDE

n Arrange for the use of a bed pan and urine bottle if the patient shows any sign of

prostration or if his temperature is high.

n If the patient is seriously ill and if in any doubt as to the diagnosis seek RADIO MEDICAL

ADVICE , failing which you should consider the need for making for port.

n Treat symptoms as they arise.

Do not attempt to get the patient up during convalescence if he is feeble, but keep him in

bed until the next port is reached.

When approaching port, send a radio message giving details of the case to enable the Port

Health Authority to make arrangements for the isolation of the case and any contacts on arrival

and Disinfection.

Immunisation and travel advice

It is important that up to date advice on immunisation and the prevalent diseases should be

obtained before arrival in a foreign port. This is most easily available from the following

publications:

Health Information for Overseas Travel , produced by the UK Department of Health, and

International Travel and Health , WHO, Geneva

Anthrax

French: Charbon

German: Milzbrand

Italian: Carbonchio

Spanish: Carbon

Incubation Period: 2 to 7 days, usually 2

Period of communicability: No evidence of transmission from person to person

Isolation Period: No evidence of transmission from person to person

Quarantine Period: None.

Anthrax is an uncommon but serious communicable disease which may occur in man and

animals. It occurs in man either as an infection of the skin (malignant pustule), or as an attack on

the lungs or intestines, or as a widely spread infection throughout the body by means of the

blood circulation.

Anthrax is, in man, usually contracted by handling infected animals, skins, hides, or furs. It

can also be conveyed by the consumption of infected or insufficiently cooked meat, or by the

inhalation of dust containing the organism.

Symptoms and signs

In most cases anthrax is accompanied by severe symptoms such as fever and prostration. When

it appears as a skin infection, it begins as a red itching pimple which soon changes into a blister

and within the next 36 hours progresses into a large boil with a sloughing centre surrounded by

a ring of pimples. Alternatively it may take the form of a painless widespread swelling of the

skin which shortly breaks down to form pus in the area.

The gastro-intestinal form of anthrax resembles food poisoning with diarrhoea and bloody

faeces. The lung form develops into a rapidly fatal pneumonia.

Treatment

Should a case of anthrax occur at sea, which is unlikely unless as a result of handling animals,

hides, skins, etc., all dressings or other material that come into contact with the discharge must

be burnt or disposed of by disinfection.

Instruments must be used to handle dressings as far as possible, and the instruments must

subsequently be sterilised by vigorous boiling for not less than 30 minutes, since the spores of

the anthrax germ are difficult to kill.

Treatment is not easy on board and the patient should be put ashore as soon as possible. In

the meantime treatment is with Penicillin

No attempt at surgical treatment (incision or lancing of the sore) should be made as it does

no good. Cover the sore with a dressing.

Seek advice from a Port Health Authority about the treatment of cargo.

Chapter 6 COMMUNICABLE DISEASES

Cellulitis (Erysipelas)

French: Erysipèle

Italian: Erisipela

Spanish: Erisipela

Incubation Period: 1 to 7 days

Period of communicability: None

Isolation Period: None

Quarantine Period: None

This disease is an acute inflammatory condition of the skin caused by a germ entering the body

through a scratch or abrasion. Cellulitis occurs anywhere, but most commonly on the legs, arms

and face.

The onset is sudden with shivering, and a general feeling of malaise. The temperature rises

rapidly and may reach about 40 o C. The affected area becomes acutely inflamed and red on the

first or second day of the infection and the inflammation spreads rapidly outwards with a

well-marked, raised, and advancing edge. As the disease advances the portions of the skin first

attacked become less inflamed and exhibit a yellowish appearance. Blisters may appear on the

inflamed area which can be very painful.

General treatment

The patient must be kept in bed during the acute stage.

Specific treatment

Give the patient benzyl penicillin 600 mg followed by oral antibiotic treatment. Paracetamol

can be given to ease the pain.

Chickenpox (Varicella)

French: Varicelle

Spanish: Varicela

Incubation Period: 14 to 21 days, usually 14

Period of communicability: Up to 5 days before the onset of the rash and 5 days after the first

crop of vesicles

Isolation Period: Until the vesicles become dry

Quarantine Period: None

This highly infectious disease starts with fever and feeling unwell. Within a day or two the rash

appears on the trunk but soon spreads to the face and elsewhere, even sometimes to the throat

and palate.

The rash starts as red pimples which quickly change into small blisters (vesicles) filled with

clear fluid which may become slightly coloured and sticky during the second day. Within a day

or two the blisters burst or shrivel up and become covered with a brownish scab. Successive

crops of spots appear for up to five days. Although usually a mild disease, sometimes the rash is

more severe and very rarely pneumonia may occur.

Treatment

A member of the crew who has had chickenpox, and therefore has immunity, could make a

suitable nurse. If all of the crew have had chickenpox in the past then there is no need to isolate

the patient. The patient need not be confined to bed unless he is unwell. He should be told not

to scratch, especially not to scratch his face otherwise pock marks may remain for life. Calamine

lotion, if available, dabbed onto the spots may ease the itching.

German: Erysipel

German: Windpocken Italian: Varicella

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