Modes of transmission of trachoma

The bacteria that cause trachoma are transmitted mainly by contact with the discharge (pus) coming from an infected person's eyes. Note that direct transmission from one person's eyes to the eyes of another person is unusual, but direct mother-to-newborn transmission can occur during birth if the mother has Chlamydia bacteria in her birth canal. These bacteria can live in the genitals of males and females, causing a sexually transmitted infection, which can get into the eyes of the baby as it is born. This is why tetracycline eye ointment (1%) is applied to the eyes of all babies as part of routine newborn care.

However, the most common routes by which Chlamydia bacteria get into the eyes and cause trachoma are through:

  • Flies landing on the face of an infected person and then carrying the infected discharge to another person's face (figure a, below).
  • An infected person touching his/her eyes and then touching another person on the face or directly on their eyes (figure b, below).
  • Clothing used to wipe infected eyes (figure c, below), and then contaminating the eyes of another person, for example if it is used as a towel.

Transmission of trachoma

Transmission of trachoma by (a) flies, (b) eye contact with contaminated hands, (c) eye contact with contaminated clothing. (Source: WHO, 1993, Primary Healthcare Level Management of Trachoma)

Based on your previous study, the infectious agents of which other diseases may be transmitted by house flies?

Show answer

The infectious agents causing diarrhoeal diseases, such as dysentery and acute watery diarrhoea, can be transmitted by flies.

Last modified: Thursday, 17 July 2014, 4:00 PM