Epidemiology of Mycoses

1
Epidemiology of Mycoses
12
Glenn S. Bulmer, Ph.D. Prof. (hon.) Peking
Medical University, Beijing
2
How can you control a disease if you dont know
the source? e.g., SARS
3

• Factors to consider
• - Where do pathogenic fungi live in nature?
• How do they disseminate?
• What is the human portal of entry?
• Why is a human susceptible?

4
Epidemiologically we have three groups of fungi
1.) Dermatophytoses man, animal, soil. 2.)
Exogenously acquired soil, air. 3.) Endogenous
in origin normal flora.
Lets look at the above three groups separately
5
Three groups (cont) 1.) Dermatophytoses
6
Dermatophytoses (cont)
Fungi which caused ringworms, athletes foot,
jock itch and all the tineas body location,
e.g. tinea pedis. These diseases are classified
by the mode transmission a.) Anthropophilic
implies organisms that are spread from man
to man, e.g. Epidermophyton floccosum,
Microsporum audouinii, M. ferrugineum and
several Trichophyton spp.
7
Dermatophytoses (cont)
b.) Geophilic are organisms that live in soil
and maybe transmitted to man by soil contact,
e.g. Microsporum gypseum (often causing tinea
barbae). c.) Zoophilic are organisms which are
transmitted to man from animals other than man
(dogs, cats, cattle, etc.). Some zoophilic
dermatophytes are Microsporum canis, Trichophyton
verrucosum and two varieties of T.
mentagrophytes.
8
Dermatophytoses (cont)

• Mode and vehicle of transmission
• Transmitted by contact with soil, infected
  humans and infected animals.
• Transmission is with hyphae and/or spores in
  soil or infected skin, nails or hair.
• In some cases fomite transmission is with
  infected clothing.

9
2.) Exogenously acquired soil, air.
This includes all other mycoses (one major
exception). Disease is acquired from one of two
sources A.) Soil where fungi live forming
hyphae and spores, they enter the host via
punctured wounds and trauma. Spore size is not
important. The following are some examples of
diseases that are acquired by this mechanism.
10
Chromomycosis
Etiologic agent showing dematiaceous hyphae and
spores
10-year old case
11
Mycetomas
15-year old case of mycetoma
One of many etiologic agents (ca 25). Note
hyphae and spores which live in nature. Fusarium
sp.
12
Sporotrichosis
Characteristic lymphadenopathy. Patient on right
has secondary
bacterial infection.

13
Sporotrichosis (cont)
Note hyphae and spores which live in nature on
plant material and are the infectious particles.
This is the pathogenic phase which is not
infectious. It can be grown in the laboratory at
35? C, i.e. the fungus is dimorphic.
14
Mycotic Keratitis (cont) - Numerous fungi
cause keratitis worldwide but mostly in tropical
or heavily agricultural areas. Spores and hyphae
are implanted onto eye following trauma.
Penicillium, one of numerous soil fungi causing
this disease.
Patient
15
B.) Air and lungs. These are fungi which grow
in nature but produce airborne infectious
particles which have the correct size limitations
to enter the human lung.
Note that airborne particles greater than 6
microns cannot enter the human lung.
16
Air and lungs (cont)

• a.) Aspergillosis and Phycomycosis
• Chronic or rapidly fatal see hyaline,
  filamentous fungi
• Organisms in environment, cannot eliminate.
• Predisposed patients, worldwide
• Diagnosed by histopathology or repeated culture.
• No good serology tests.
• Therapy very difficult.

17
Aspergillosis and Phycomycosis (cont)
Lung infarct (left), aspergilloma (right).
Diseases initiated by spores entering the lungs.
18
Aspergillosis and Phycomycosis (cont)
(top left) Young Rhizopus showing coenocytic
hyphae and spore sacs (infectious particles).
(top right) mature Rhizopus releasing spores
capable of lung entry. (lower right) Aspergillus
with infectious spores (3-6 microns).
19
Air and lungs (cont)

• b.) Histoplasmosis
• Granulomatous disease of lungs and RES which
  mimics TB.
• Spread from bird droppings, especially
  blackbirds, chickens and bats.
• Major endemic area in the world is eastern USA,
  although 10 people in China are skin test
  positive (very high in Sichuan).

20
Histoplasmosis (cont)
Infectious form of Histoplasma capsulatum
showing large and small spores. Only the small
ones can enter the lungs. In nature or lab at 24?
C.
Yeast (pathogenic) form as in vivo or cultured at
35? C. Not infectious. This is a dimorphic
fungus.
21
United States of America
22
Air and lungs (cont)

• c.) Coccidioidomycosis
• Major endemic area in the world is the desert
  country in SW USA and Mexico. Characterized by
  little rainfall and intense heat. Some evidence
  that the organism Coccidioides immitis favors
  salty soils.
• Most susceptible are Asians, American Indians,
  Mexicans and American Blacks, i.e. dark-skinned
  people.
• I have seen two cases in the Philippines. Both
  patients have lived in the USA (State of
  California).

23
United States of America
24
China
25
Coccidioidomycosis (cont)
The organism Coccidioides immitis is found in
desert soils as shown here. This looks similar
to areas in Southern Xinjiang province. The
spores are lt 7 microns, become airborne, enter
the lungs and initiate disease.
26
Coccidioidomycosis (cont)
Highly infectious spores growing in soil or in
the laboratory. Most infectious of all fungi.
Inhale one spore and you become skin test
positive.
27
Air and lungs (cont)

• d.) Cryptococcosis
• - Fatal disease of brain (CSF), causing
  meningitis
• Encapsulated yeast seen in India ink and
  tissue.
• In pigeon droppings and near Eucalyptus trees
• 5 cases/million normal population but gt20 AIDS
• 2 cause of death of AIDS in Thailand

28
Cryptococcosis (cont)
PAS stain showing encapsulated yeast in tissue
Pulmonary cryptococcosis
29
C. neoformans incubated in soil
Size of organism ( microns)
30
15
5
5
1
3
Time in soil (months)
This shows that C. neoformans decreases in size
and loses most of the capsule during soil
incubation.
30
C. neoformans (cont)
Note that many airborne particles are less than 5
microns in diameter and therefore can enter the
human lung.
31
Air and lungs (cont)

• e.) Sporotrichosis
• Previously shown was the lymphadenopathy form
  of sporotrichosis which was acquired from spores
  entering the body via a puncture wound.
• However in rare instances a pulmonary exists.
• The pulmonary form is caused by spores entering
  the lungs from peat moss or other dusty forms of
  organic matter.

32
Sporotrichosis (cont)
Note hyphae and spores which live in nature on
plant material and are the infectious particles.
33
Air and lungs (cont)
f.) Penicilliosis - New and frequently fatal
mycoses found only in S.E. Asia and southern
China (Guangdong to Yunnan provinces). 3 cause
of death in AIDS patient in Thailand
34
Penicilliosis (cont)
The mysteries of this disease 1.) How
widespread is the endemic area, e.g. two new
cases were just found (2004) in Beijing (may have
come from Guangdong province)? 2.) What is the
portal of entry? Currently lungs are the
suspected portal of entry. 3.) Where does the
organism (Penicillium marneffei) live in
nature? 4.) How can the disease be controlled?
35
Penicilliosis (cont)
Infectious spores, lt5 ??
Intracellular yeast
36
3.) Endogenously acquired
Candidiasis is the only major systemic mycosis
that is endogenous in origin. That means that
the numerous yeast species are part of mans
normal flora. This means that the key to
infection is predisposing factors, e.g. 90 of
AIDS patients have candidiasis. The only
exception to being endogenous in origin is STD
candidiasis and nosocomial acquired candidiasis,
usually from hospital workers. Today, candidiasis
is the most important systemic mycoses in the
world.
37
Candidiasis (cont)
Dissemination or disease spread is with yeast
cells and/or hyphae. The hyphae looks distorted,
thus it is sometimes called pseudohyphae. The
disease is worldwide and fatal in susceptible
hosts.
Yeast cells and pseudohyphae seen in patients.
38
Conclusions
1.) Most systemic mycoses are acquired from
fungi which live in soil on decaying vegetation.
2.) Fungi produce hyphae and spores which enter
humans via a punctured wound or, if less than 6
microns, can enter the lungs. 3.)
Dermatophytoses (ringworms) can be transmitted to
man from soil, animals and other men. 4.)
Candidiasis is the only major mycosis that is
endogenous in origin. 5.) Most systemic mycoses
are seen in patients that have depressed
immunity. This may be genetic or acquired.
39
Thank You!