Biomedical Engineering Reference
In-Depth Information
Infection by Chlamydia trachomatis is the second most common sexually
transmitted disease, with about 4 million new cases occurring annually in
North America [32]. The disease name for this infection is somewhat confus-
ingly called “Chlamydia,” perhaps the only disease that takes the name
of a genus, without modification. The proper disease name “chlamydiosis”
is reserved for infections by another species, Chlamydophila psittaci (see
below). This is an etymologic disaster, as Chlamydophila psittaci infection
is known by most clinicians as psittacosis, and would more accurately be
called chlamydophilosis, in any event. In men and women, Chlamydia can
produce urethritis and rectal inflammation. Chlamydia can also produce
prostatitis in men. In women, infections that ascend the genital tract can
yield endometritis, salpingitis, and pelvic inflammatory disease. Infants born
to infected mothers may develop inclusion conjunctivitis (named for the cyto-
plasmic inclusion bodies produced by chlamydial organisms), and chlamydial
pneumonia.
The high infection rate in the population is made possible, in part, by the
high prevalence of carriers: about one third of infected men and women have
no clinical symptoms. In addition, infection does not confer immunity, and
re-infections are common.
According to the World Health Organization, there are about 37 million
blind persons, worldwide. Trachoma, caused by Chlamydia trachomatis,isthe
number one infectious cause of blindness and accounts for about 4% of these
cases. The second most common infectious cause of blindness worldwide is
Onchocerca volvulus (Class Nematoda, Chapter 27), accounting for about 1%
of cases [28]. Trachoma is spread by direct or indirect contact with eye secre-
tions. Infection causes intense inflammation of the conjunctiva.
Readers should not confuse trachoma with inclusion conjunctivitis, as
each disease is caused by distinct variants of the same species (Chlamydia
trachomatis). Trachoma is contracted by exposure to eye secretions from
people with trachoma. Inclusion conjunctivitis is caused by ocular exposure
to secretions from the sexually transmitted infection.
Chlamydia trachomatis may also cause lymphogranuloma venereum, a
disease that usually presents as swollen lymph nodes in the groin. The lymph
nodes often have draining abscesses. The disease is rare, with only a few
hundred cases occurring in the United States each year. Lymphogranuloma
venereum must not be confused with granuloma inguinale, also known as
granuloma venereum, caused by the bacterium Klebsiella granulomatis
(Chapter 7).
Chlamydophila psittaci is the cause of psittacosis, a disease that takes
its name from birds of Class Psittaciformes (i.e., parrots) the organism's
animal reservoir. Chlamydophila infects the lungs of birds. The birds pass
the infection to humans through droplet secretions.
Chlamydophila pneumoniae is a significant cause of pneumonia in the
United States. The disease is often mild. In addition, Chlamydophila pneumoniae
