Transmission

When the agent is attempting to travel to a host, it is at its most vulnerable position; therefore, many methods of control have been developed to interrupt transmission.

Quarantine or isolation Keeping the agent at a sufficient distance and for a sufficient length of time away from the host until it dies or becomes inactive can be effective in preventing transmission. Quarantine or isol ation can be used for animals as well as humans. The former is more effective because animals can be forcibly restrained. Because it is difficult to quarantine humans, it is not widely practised as a method of control, except where the disease is very infectious or the patient can be restrained easily (e.g. in hospital, Lassa fever).

Contacts People who might have become infected because of their close proximity to a case are called contacts. They can be isolated, given prophylactic treatment or kept under surveillance.

Environmental health Methods of personal hygiene, water supplies and sanitation are particularly effective against all agents transmitted by the faecal-oral route whether by direct transmission or complex parasitic cycles involving intermediate hosts.

Animals Whether they act as reservoirs or intermediate host animals can be controlled by destruction or vaccination (e.g. against rabies). If animals are to be eaten, their carcasses can be inspected to make sure that they are free of parasitic stages. The excretions or tissues of an animal can be infectious; so protective clothing and gloves should be worn when handling animals.

© R. Webber 2005. Communicable Disease Epidemiology and Control, 2nd edition (Roger Webber)

Personal hygiene Water supplies Sanitation

Personal hygiene Water supplies Sanitation

Rabies Transmission Route

Larvicides Adulticides

Biological Biological

Larvicides Adulticides

Biological Biological

Fig. 3.1. Control principles.

Notification and surveillance

Physical protection

Vaccination

Prophylaxis

Physical protection

Vaccination

Prophylaxis

Education

Assistance

Education

Assistance

Communications

LO LO

Cooking Proper cooking renders plant and animal produce safe for consumption, although some toxins are heat-resistant. Food should be prepared hygienically before cooking and stored properly afterwards.

Vector control is one of the most highly developed methods of interrupting transmission because the parasite utilizes a vulnerable stage for development and transport. Attack on vectors can either be on their larval stage by using larvicides and methods of biological control, or while they are adults with adulticides.

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