- 14 =.

VIII. PROTOZOA AS CAUSES OF DISEASE

IX.

- Protozoa are classified as animal organisms. There is some uncer-
tainty as to whether some organisms included in this group should not be
considered as vegetable in nature,. The more important point for our pur-
poses is whether they produce disease ani what defensive hygiene methods
are necessary to combat their activities.

Protozoa are simple one-celled organisms. About 7,000 species have
been described. Each of them has a characteristic "life cycle.’ Diseases
caused by a few of the protozoa will be discussed.

Malaria--still an important public health problem.

{a) Cause--Three distinct parasites (plasmodium) .

(b} Source of Infection--Blood of infected individuals.

{c) Mode of Transmission——Anopheles mosquito--parasite undergoes life
cycle in body of mosquito and infection is transmitted to another
individual by vite of mosquito.

Carriers=—Common in infected regions.

Prevention--Screening active cases--quinin prophylaxis and
suppression of mosquitoes.

O Qs

‘Dysentery-~(Amebic)--Most frecuent in Tropics but many cases demon~
strated in United States.

(a) Cause--Endamoeba histolytica.

(b) Mode of Transmission--Intestinal discharges of infected individ-
ual. Transferred by drinking water, contact with fresh dis-
charges, flies, etc.

Trypanosomiasis or Sleeping Sickness--(Africon)--Next to Malaria, the
Trypanosoms are man's most deadly enemies among the protozoa.

(a) Cause--Trypanosoma (two species).
(b) Mode of Transmission--Tsetse fly--Life cycle of parasite in the
body of the fly.

Syphilis--one of the mjor plagues of the world,

(a) Cause~-Spirochaeta pallida or treponema pallidum. A very small
organism, but larger’ than the average bacteria. Discovered by
Schandin and Hoffman, 1905,

(b} Prevalence-~Estimated 8% of poptlatio (Rosenau).

{c) Organisms-~Blood, tissue juices, secretions, and sores of infected
persons,

(d} Modes of Transmission--(a) Directly, most commonly by sexual in-

tercourse, less frequently by kissing, (b) Indirectly, common
drinking cups, instruments, pipes, etc. (c) Congenitally, organ-
isms pass from mother to child.

(e) Prevention and Cure and Social Control.

METOZOA AS CAUSES OF ILL-HEALTH

Metozoa are the so-called’ higher animal parasites that often cause
disease by means of their eggs, enbryoes, and larvae. The more important
members of this group are: (a) Flukes, (b) Tapeworms, (c) Round worms, and
{d) Hook worms.