Communicable diseases are those that can be transmitted from one person (or animal) to another. There may be direct or indirect transmission to a well person from an infected person or animal – at times through an intermediate animal host, a vector (a mosquito), or the inanimate environment. Illnesses result when an infectious agent invades and multiplies in the host.
The occurrence and spread of disease are determined by interplay of factors specific to the causative agent, the environment, and the individuals or groups in whom the disease occurs. A causative agent (if many were to fall ill at the same time) could endanger the operation and the safety of the ship. Thus, it is important to know how various diseases are spread, and what measures should be taken to ensure their prevention and control.
Infectious agents
Organisms that produce disease in man range in size from the submicroscopic viruses to the tapeworm, which may attain a length of several meters.
Various groups of infectious agents are listed below, together with some of the diseases they cause.
| Bacteria | Sore throat, pneumonia, tuberculosis, syphilis, bacillary dysentery, cholera |
| Viruses | Common cold, influenza, yellow fever, poliomyelitis, rabies, measles, and viral pneumonia |
| Rickettsiae | Typhus fever |
| Protozoa | Malaria, amoebic dysentery |
| Metazoa | Filariasis, trichinosis, hookworm and tapeworm infections |
| Fungi | Ringworm and tinea pedis (athlete’s foot) |
Infectious agents are usually specific in their disease-producing capabilities. Several different organisms can produce diseases that resemble each other clinically (in symptoms and course) and pathogenically (in the anatomical changes they cause).
Essential basic rules for the management of communicable diseases
· 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 utensils, in order to try to establish the diagnosis.
· Put the patient to bed,and appoint someone to look after and nurse him and organize the control of his eating and drinking utensils and their sterilization after use.
· Givefluidsin the first instance.
· If the patient’s temperature exceeds 39.5ºC make arrangements fortepid sponging.
· Arrange the use of bedpan and urine bottle if the patient shows any sign of prostration or if his temperature is high.
· If the patient is seriously ill and if there is any doubt as to diagnosis, seek RADIO MEDICAL ADVICE, failing which you should consider making for port.
· 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 authorities to make arrangements for the isolation of the case and any contacts on arrival.
2. Answer the following questions
1. What is a communicable disease?
2. What factors determine the occurrence and spread of communicable diseases?
3. What groups of infectious agents do you know?
4. What are the essential basic rules for the management of communicable diseases?
3. Give summaries of the following texts
Malaria
It is an acute protozoa disease caused by malaria plasmodia. It is characterized with periodical attacks of fever, augmentation of liver and spleen, anemia and relapses. The source of infection is a sick person and parasite carrier. It is transferred via malaria mosquitoes of Anopheles genus. The parasite can be transferred via blood transfusions. Malaria is frequently occurred in the tropical and subtropical countries. At the beginning a sick person complains for weakness, headache, sometimes chill and fever. In a few days malaria acquires typical signs. At the fist half of a day the temperature increases sharply, the skin is pale and blue, dry and hot to touch. Tachycardia and hypotension are developed. In 2-3 hours the temperature raises up to 40-41ºC, the sick is anxious. Vomiting, loss of consciousness and hallucinations are possible. Then in 2-4 hours temperature reduces critically, abundant hydrosis is observed. Then the state is improved. Attacks repeat in 2-3 days. The total amount of attacks is 8-10. Malaria may provoke complications: anemia, coma, acute kidney failure, mental disorders, etc.
Special treatment is prescribed. All the persons with high temperature should undergo the blood examination for malaria. All the persons supposed to work in malaria-suspicious areas should take anti-malaria medicines 2-3 days prior to the visit, during the visit and afterwards for 4 weeks.
Yellow Fever
Prevention. – This disease is caused by the bite of the mosquito Stegomyia fasciata that has fed on infected persons. All the crewmembers should be vaccinated prior the voyage. All fresh water receptacles on the ship should be protected.
Symptoms. – The incubations period is usually three or four days, as a rule; the onset is sudden and in the early morning hours. Chilly feelings are common, followed by high fever. The eyes become red and the skin feels hot, dry and yellow. Nausea and vomiting are common. The bowels are usually constipated. The face is flushed and the throat is sore. The first stage of fever lasts two or three days, then is followed by a calm when the fever goes down. This stage lasts two or three days and in mild cases recovery begins but in fatal cases the fever rises and remains constant or goes higher than in the first stage.
In the third stage vomiting increases and the vomit may contain large amounts of blood. This altered blood gives it a dark colour and is commonly called black vomit. It is not a fatal symptom, but occurs only in severe cases.
Treatment. – The patient should be isolated in a well-screened room. The bowels should be opened by a purge. Plenty of alkaline water should be given and the diet should consist only of thin fluids. Cold baths or ice packs may be used to reduce the fever.