Group Title: Veterinary Science mimeograph series
Title: Parasites of animals infectious to man
Full Citation
Permanent Link:
 Material Information
Title: Parasites of animals infectious to man
Alternate Title: Veterinary Science mimeograph series - University of Florida ; 55-3
Physical Description: 12 leaves : ; 28 cm.
Language: English
Creator: Swanson, Leonard E., b. 1898
Dennis, Walter R.
Stone, William M.
University of Florida -- Agricultural Experiment Station
Donor: unknown ( endowment )
Publisher: University of Florida, Agricultural Experiment Stations
Place of Publication: Gainesville, Fla.
Publication Date: August, 1954
Copyright Date: 1954
Subject: Parasites -- Florida   ( lcsh )
Animals as carriers of disease -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by Leonard E. Swanson, Walter R. Dennis and William M. Stone, Jr.
General Note: Caption title.
General Note: "August, 1954."
 Record Information
Bibliographic ID: UF00094199
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 433106088

Full Text

Veterinary Science Mimeograph
Series No. 55-3



August, 1954

Leonard E. Swanson, Walter R. Dennis and William M. Stone, Jr.

I. General Introduction:

A. Parasitology is the science that deals with parasitism.

1. A parasite is an animal that lives upon or within another

living organism at whose expense it obtains nourishment and

protection without giving anything in return for this relation-


2. Parasitism is the relationship between the host and parasite.

3. Helminth is a defined term for worms.

4. Helminthology is the study of wormd.

B. All animals are parasitized with one form or another of these


C. Wild animals are especially heavily parasitized and quite often

serve as reservoirs of infection for domestic animals and man.

D. Domestic animals are a constant source of possible infection of

parasites to man.

II. Relationship of Parasites:

A. Symbiosis The living together of two dissimilar organisms

to the advantage or disadvantage of one or both.

1. Mutualism is a form of symbiosis in which both symbionts are

in more or less measure, benefited by the association.


Example: Protozoan fauna of the intestinal tract of termites

change wood materials to digestible forms.

2. Commensalisn is a form of symbiosis in which one symbiont is

benefited, but its co-symbiont is neither benefited nor harmed.

Example: Common colon amebia of man which feed on waste products.

3. Helotism is a form of symbiosis in which one organism enslaves

the other.

.^ Example: Dermatobia hominis, jSouth American skin maggot. The

adult female fly captures other insects, deposits her ova on

their bodies and they in turn serve as a means of transportation.

The maggot larvae are liberated from the eggs while the insect

carrier is obtaining its blood meal from man or beast.

h. Parasitism is a form of symbiosis whereby the parasite derives

its food and protection, usually at the expense of the host animal,

yet in light infections this association may be of no harm to either

organism. Biologically it is not the intention of parasites to

overparasitize the host to a point whereby impaired health or death

of the host will result in destruction of the parasite itself.

B, In summary, a symbiont receiving the benefit is the parasite and

the one receiving the damage is'the host.

C. Hosts

1. Fi-l1 or definite hosts harbor adults or sexually mature parasites.

2. Intermediate hosts harbor larval forms, where an intermediate

host is required to complete the life cycle.

III, Zooparasites are parasites which belong to the animal kingdom:

A. Ectoparasites are those that are parasitic to the surface of the

body' or have direct contact to the skin.


Examples Lice, fleas, ticks, mites, fly larvae, etc.

B. Endoparasites are parasites which enter the body of the host,

inhabiting the alimentary canal, liver, lungs, blood and other


Example: Ascarids, hooks, flukes, amebia, etc.

IV. The influence of parasites upon the host depends upon the number and

age of parasites present, location, the nature of their food, route

through the body of larval forms, environmental conditions, and age

of the host. The effects of parasites on the host also depend on the

balance of minerals, vitamins, proper food intake and general condition

of the host.

V. Parasites Injure the Host:

A. Through mechanical injury such as biting, migration and loss of blood.

Example: 1. Biting-lice.

2. Iigrating-ascarid or fluke larvae causing tissue destruction.

3. Bloodsucking-hookworm.

B. Through obstruction as in the case of a mass infection of ascarids

blocking the intestinal tract and/or bile ducts&

C. By injection of toxins suc as occur in extreme hookworm infections.

D. Tissue feeding of maggots.

E. Anaphylactic reaction extreme sensitivity to touch of ascarids.

VI. Internal p-.rasites of man and animal fall into the following phyla

and classes:

A. Phylum Platyhelminthes

1. Class Trematoda

Examples: Liver fluke


ab Fasciola hepatica and F. gigantica.

b. Clonorchis sinensis.

Blood fluke

a. Schistosoma japonicum.

Intestinal fluke

a. Fasciolopsis buski.

2. Class Cestoda

Example : tapeworms

a. Taenia saginata

b. Taenia solium

c. Echinococcus granulosus

d. Diphyllobothrium latum

B. Phylum Nemathelminthes

1. Class Nematoda

Example: roundworms

a. Necator americanus

b. Ancylostoma braziliense

c. Enterobius vermicularis

C. Phyly Protozoa

1. Class Infusoria

Example: a. Balantidium coli

2. Class Sarcodina

Example: a. Endamoeba coli

b. E. histolytica

3. Class Sporozoa

Examples a. Isospora hominis

b. Plasmodium falciparum

4. Class. jtigophora

Example: a. Trichomonas vaginalis

VII. Internal parasites of man listed according to their location in

the body are:

A. Bronchial tubes of the lungs

1. Lung fluke

a. Paragonimus westermanii

B. Liver

1. Liver flukes

a. Fasciola hepatica

b. F. gigantic

2. Tapeworms

a. Echinococcus granulosus

C. Small Intestine

1. Threadworms (microscopic in size)

a. Strongyloides stercoralis

2. Hookworms

a. Necator americanus

3. Rouhdworms

a. Ascaris lumbricoides

4. Tapeworms

a. Taenia saginata

b. Taenia solium

c. Dipylidium caninum (occasional)

d. Diphyllobothrium latum

D. Large Intestine

1. Protozoa

a. Balantidium coli

b. Endamoeba coli

c. Endamoeba histolytica

E. Skin

1. Filaria Wuchereria bancrofti (elephantiasis)

2. Larval migration

a. Ancylostoma braziliense

b. Ancylostoma caninum

F. IKuscle

1. Larval migration

a. Trichinella spiralis

VIII. Life Cycles:

A. All parasites of the class Nematoda are what is termed direct

infectors. No intermediate host is required, with the exception of

trichinella, which require an intermediate host, the pig, bear, dog, etc.

1. Direct infectors depend on optimum moisture, temperature and

vegetative conditions to complete their life cycle. The eggs are

passed out of the host animal in the feces and hatch, liberating

a minute larva. This larva, after three or more molts, is known

as the infective stage, which is ingested or enters the body by

skin penetration. Upon reaching the digestive tract the larva

finds its suitable location in the host where it reaches sexual

maturity, mates and begins laying eggs.

2. Filaria depend upon mosquitoes or other biting insects to com-

plete their life cycle. The female worms deposit their larvae in

the host bloodstream and/or tissues. The insect vector, feeding on


the infected animal ingest the microscopic larvae, which further

develop in the insect and at a subsequent feeding these larvae are

injected into another host animal.

B. Parasites belonging to the class Trematoda require an intermediate


1. Liver flukes, and others of the Trematoda class require a fresh

water snail to complete their life cycle*

a. Fasciola hepatica and Fasciola gigantic

1. The young flukes that hatch from the eggs burrow into the

soft tissue of a fresh water snail where they develop and

multiply. After a period of time they are liberated into

water as young free swimming flukes. These young flukes

swim around in water, attach themselves to vegetation and are

subsequently eaten by man. This stage in the life cycle is

known as the infective stage to man or beast.

b. Clonorchis sinensis

1. This fluke life cycle is identical with the exception that

it requires two intermediate hosts, a fresh water snail as the

primary intermediate host and a fresh water fish as the secon-

dary intermediate host. Man may become infected by eating

improperly prepared fish.

2. Blood flukes.

a. Schistosoma japonicum

1. Blood fluke life cycles are identical to the above except

that there is a skin penetration by the cercariae stage instead

of encystment on vegetation and no secondary intermediate host

is required.


3. Intestinal flukes

a. Fasciolopsis buski

i. The intestinal fluke life cycle is identical witl other

flukes except that the infective stage encyst on water

chestnuts and other plants eaten raw by tropical man and no

secondary intermediate host is required.

C. Parasites belonging to the class Cestoda requirean intermediate


1. Taenia saginata; Taenia Solium and Echinococcus granulosus.

a. The human tape worm (Taenia saginata) adults are found in

the human intestinal tract. The gravid segments are passed to

the exterior, ingested by cattle and the embryo penetrates the

intestinal wall, is picked up b the vascular system and carried

to the.muscles. They usually locate in the heart and cheek

muscles. In heavy infections they may be found in any muscle

of the body. If man eats raw or partially cooked meats, he

may become infected. In modern meat plants inspecting veter-

inarians examine each and,every animal for these cysts and are

able to reduce the incidence of human tapeworm infections.

b. The human tapeworm (Taenia solium) life cycle is identical

with the above except that swine are the intermediate hosts.

It is also possible for man to serve as both the final and

the intermediate host.

c. The dog tapeworm (Echinococcus granulosus) adult lives in

the intestines of dogs and wild carnivera. The tapeworm

segments are passed from the host with fecal materials which

may contaminate human food and/or water supplies. The in-

fective embryo penetrates the intestinal wall, is picked up by

the vascular system and carried to various parts of the body,

especially the liver where it develops into an infective hydatid

cyst. Sheep, goats and wild ruminating animals also may eat

the contaminated food and become infected as is man. Wild or

domestic canine animals may eat these parasitized intermediate

hosts and become infected with the adult tapeworms.

D. Protozoa

1. These parasites may be direct or indirect infectors depending

upon the parasite in question. In the direct infector group man

becomes infected by consuming contaminated food, water and direct

contact with the organism. House flies, birds, rats, man, etc.

may serve as mechanical means of transporting these infections.

The indirect group depend upon insect vectors to complete their


a. Those belonging to the malaria group require a mosquito to

complete their life cycle, whereas coccidia which belong to the

same class are direct infectors.

b. Those belonging to the trichomonas, ameba and balantidium

groups are direct infectors.

IX. Damage d6ne to the host:

A. Parasites, depending upon their location in the host and type of

food required for their existence, injure the animal by feeding on

blood, bacteria, tissue, bile, epithelium, lymph, or by mechanical

blocking of the essential physiological functions of the respective

organs or tissues of the body.


.X. Diagnosis:

Internal parasite infection, whether it be in man or other animal,

cannot be seen in its protected home. The infection may be likened to

a closed book; you do not know of its presence or absence unless accurate

methods of diagnosis are utilized.

Infection may be suggested if man exhibits symptoms of anemia, enlarged

abdomen, irritability and general unthriftyness. The most accurate diag-

nosis universally used for determination of parasitism in man is the

microscopic examination of specimens of feces and/or blood for parasite

ova and/or larval forms of parasites.

XI. Prevention:

In general parasites must live congenially with their host in order

to produce their kind; however, if by accident, overcrowding, improper

diet, unsanitary premises, man may become excessively parasitized.

The most critical point to be emphasized in the control of parasitism

in humans is farm, home and personal sanitation. If modern toilet

facilities are not available, outside toilets should be constructed

so as to exclude fly contamination or possible animal invasion. Locate

the toilet where possible contamination of food or water supply for man

or animal cannot occur and this includes protection from heavy storm

damage. It is realized that average individuals will not normally use

barns, fields and woods for human evacuation but it does occur and should

be discouraged. Fresh vegetables and fruit eaten raw-should be thoroughly

washed, especially those from farmers who may be prone to use night soil

as a fertilizer.

The practice of allowing children to work and play barefoot in tropic

/ \V


Sand subtropic areas should be discouraged as this invites heavy

hookworm infections. On beaches and public gathering places where

dogs roam, there is always the possibility of picking up creeping

eruption or hookworm infection and this can only be guarded against,

according to our present knowledge, by wearing protective clothing.

Avoid as much as possible these contaminated areas. Dogs that are kept

as pets around homes should be watched closely and treated by a

Veterinarian for the removal of hookworm infection. Also, on your own

premises, it is good common sense to pick up all bowel passages from

dogs and bury or burn same daily. The above not only lessens the

possibility of creeping eruption, but prevents dogs and man from

hookworm infection.

The above statements apply equally well to infections with Strongyloides

stercoralis. Trichinella or tapeworms of humans are only contracted by

consumption of raw or partially cooked meats, especially meats from

uninspected sources. Pork products even from inspected establishments

should not be eaten unless cooked thoroughly. The meat should have a

greyish appearance and not pink or red when cooked. Beef from inspected

establishments may be eaten raw or partially cooked with relative safety

as the cysts can be located at time of slaughter. If found, proper steps

to eliminate the parasite in the carcass are taken before it is offered

for human consumption. Fish products should only be eaten after proper

preparation and thorough cooking.

As this outline is prepared for public health sanitarians, it is felt

that they can render the greatest service to communities by advising

their people on methods of prevention, and in assisting Physicians and


.Veterinarians in the curtailment and elimination of parasites. Swimming

pools, ponds, lakes or streams should not be used for bathing or drink-

ing purposes until proper sanitary measures and examinations are taken

to reduce possible human infections.


1. Belding, David L. 1942. Textbook of Clinical Parasitology.
Appleton-Century-Crofts, Inc. New York, N.Y. 888 pp.

2. Morgan, Banner B. and P.A. Hawkins. 1951. Veterinary Helminthology.
Burgess Publishing Company. liinneapolis, Minnesota. h00 pp.

3. Underhill, 1924. Parasites and Parasitosis of the Domestic
Animals. The Iacmillan Company, New York, N.Y. 379 pp.


University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs