The Indian Journal of Tuberculosis - LRS Institute of Tuberculosis ...

Leading Article Ind. J. Tub., 2992, 39, 3
HIV AND TUBERCULOSIS
An unusual pattern of opportunistic diseases
in predominantly young homosexual men was
notified to the Centers for Disease Control
(CDC) in Atlanta, U.SA. by physicians in New
York city, Los Angeles and San Francisco in late
1980 and early 1981. These notifications were the
first cases of Acquired Immunodeficiency
Syndrome (AIDS) representing the severe end of
the clinical spectrum that follows infection with a
retro virus, the human immunodeficiency virus
(HIV), formerly called the human T Lymphotrophic
virus type III/Lymphadenopathy associated
virus (HTLV-III/LAV), by scientists at the
Pasteur Institute 1 and the National Institute of
Health 2 .
The biological characteristic of AIDS is a
major deficiency in cellular immunity that occurs
with destruction of a substantial amount of T 4 or
T helper lymphocytes. The deficient cellular
immunity leads to frequent occurrence of
infections which is normally controlled by cellular
immunity. Tuberculosis is a classic example of a
disease, resistance to which is mediated by
cellular immunity. As such, tuberculosis is
prominent among the diseases that affect patients
with AIDS.
Etiological Aspects
The HIV infection, transmitted essentially
through blood or sexual intercourse is generally
asymptomatic. The clinical profile caused by HIV
infection results from the virus infecting the CD 4
(T 4 ) lymphocytes which may be destroyed or have
their normal function impaired.
Nearly all the cases of tuberculosis occur as a
result of infection acquired via the lungs through
the inhalation of infectious aerosol droplets
containing viable M. tuberculosis. Following
primary infection with Koch's bacilli, the strain
can survive in the host (even a non-HIV-infected
host) for years and decades without causing any
pathological manifestation. This is due to the
balance that is reached between the
aggressiveness of the pathogen and host's defence
mechanisms, drawn mainly from cellular
immunity 3 . Murray and Mills 4 have noted that
lungs may be more predisposed to opportunistic
complications because their immunological
capabilities may be more suppressed than those
of other organs. It is not clear whether the
vulnerability of lungs to infections is merely the
regional manifestation of the systemic
abnormality or additional HIV induced factors
affect the lungs' own complex local defense
mechanisms.
Epidemiological Aspects
(a)
North America
In the United States, the trend of tuberculosis
is known since 1953 when national reporting was
started. There has been an average decline of
about 5% per year in the tuberculosis case rate
upto the year 1984. In 1985, the rate of decline
lessened to 0.2% and in 1986, for the first time in
33 years, there was an increase of 2.6% in the
number of reported cases 5 . Pitchenick et al 6 have
reported that tuberculosis occurred in 61.4% of
Haitians with AIDS (27/44) compared with 2.7%
of non-Haitians (1/37) with the syndrome. Louis
et al 7 reported that 24 of 280 (8.6%) patients with
AIDS had tuberculosis while Chaisson et al 8
found in a San Francisco population based study
that of the 287 cases of tuberculosis in non Asian
males, 15 to 60 years of age, 35 (12%) had AIDS,
including 23 America born whites.
(b)
African Countries
In sub-Sahara Africa, there is a high
prevalence of HIV infection in many countries
that also have an extremely high prevalence of
tuberculosis. In urban centres of this region, 5%
to 20% of the sexually active population are
infected with HIV 9 Although data from Tanzania
and Burundi show an increase in the number of
tuberculosis cases after 1983, yet the increase
could either be due to HIV infection or to an
improved utilisation of health services 10.