CHAPTER 7.pptx

CHAPTER 4. PROTOZOANS OF VETERINARY MPORTANCE
 Introduction
 Protozoa are unicellular organism that are eukaryotic (their genetic information is
stored in chromosomes contained in a nuclear envelope) in which various
activities taking place in the organelles of the cell.
 Unicellular primitive animals (the first animals)
 Microscopic, except very few species
 Most protozoa's are free-living organisms
 Of those that live in the body of animals, only a very small proportion are
associated with disease
 Protozoa of great pathogenic and economic importance are:-
 Malaria and amoeba in human
 Trypanosomes, babesia and coccidia in animals

Cont.
Structure of protozoa
Protozoa are eukaryotic: nucleus enclosed in a membrane
Contain two nuclei (micro and macronucleus).
micro nuclei important for reproduction
macronucleus regulates the cytoplasm functions
(metabolism, respiration, locomotion and other activities).
Move by means of flagella, cilia, pseudopods
Protozoans do not have a rigid cell wall.

Cont.
 Feeding (Nutrition)
 Many protozoa ingest nutrient materials in solution
(pinocytosis)
 In some, nutrients being absorbed through the body wall
• Reproduction and lifecycle:- Asexual, Sexual or A
combination of both
 Asexual Reproductions
 Binary fission (the commonest form),
 Schizogony (multiple fissions) or
 Budding in some protozoan parasites.

Cont.
 Binary fission -two daughter cells result from a ‘parent’ cell,
division being along the longitudinal or transverse axis.
 Schizogony - the nucleus divides several times before the
cytoplasm does.
–The dividing form is called schizont and the daughter forms
are called merozoites.
 Budding - is an asexual reproduction in which two or more
daughter forms are produced by the ‘parent’ cell

Cont.
 sexual reproductions
Conjugation: it is a form of sexual reproduction in
which two organisms pair and exchange nuclear
material followed by separation and nuclear
reorganization.
Syngamy: it is a form of sexual reproduction in
which two gametes fuse to form a zygote.

Cont.
 Host range
 All animals are susceptible. Some protozoan parasites have highly
specific host ranges (e.g. Eimeria).
 Others are less discriminate and will infect many hosts
• e.g. Giardia & Cryptosporidium.
 Site of Infection
 Most organs & tissues e.g. intestine, muscle, brain, liver & blood in which
some live free within the intestine or blood.
 while others are intracellular

4.1.Genus: Trypanosoma
 Trypanosomes and Trypanosomosis
 Main morphological features
 Trypanosomes are unicellular, flagellated organisms
 They are blood parasites (haemoparasites) which in the
vertebrate host occur in the blood and tissue fluid
 the movement by the thread-like filament called flagellum
 Within this genus they are known as haemoflagellates

Cont.
 Life cycle
 The life cycle has two phases
– in the insect vector
– in the mammalian host
• Transmission by insects may be
– cyclical: by tsetse flies, Glossina species
–mechanical: by other biting flies

Cont.
 Cyclical transmission
 A tsetse fly acquires a trypanosomal infection when feeding
on a parasitaemic mammalian host
 The trypanosomes undergo a cycle of development and
multiplication in the digestive tract of the fly
 Mechanical transmission
 A biting insect passes the blood forms from an infected
animal to another in the course of interrupted feeding

Cont.
 Reproduction
• Is by a process of division to produce two daughter cells, the
division into two daughter cells (binary fission)
 Transmission and distribution
 In Africa, the primary vector for T. congolense, T. vivax, and T.
brucei is the tsetse fly

Cont.
 The distribution of the tsetse-transmitted African trypanosomes is
governed by that of their tsetse vectors, which infest an area of sub-
Saharan Africa
 That extends from the southern edge of the Sahara desert (15° N to 20°
S.)
 Trypanosomosis is also mechanically transmitted by other biting flies
through the transfer of blood from one animal to another.
 The most important mechanical vectors are flies of the genus Tabanus and
Stomoxys
 In Africa, both T. vivax and T. evansi have spread beyond the "tsetse fly
belts" by mechanical vectors

Cont.
 Distribution in Ethiopia
 Tsetse flies in Ethiopia are confined to the southern and
western regions
 Tsetse infested areas lie in the lowlands and also in the
river valleys of
– Abay (Blue Nile)
– Baro (Akobo)
– Didessa
– Ghibe and Omo

Cont.
Cattle
The most important trypanosome species affecting
cattle in Ethiopia are T. congolense, T. vivax and they
cause (Nagana)
• T. brucei
Cattle infected by trypanosomes develop
–fever, anaemia, weight lose, and progressively become
weak , unproductive and abort or may become infertile

Control of Trypanosomosis
Control strategies in trypanosomsis except
dourine, can be based on:
– vector control
– parasite control
– use of trypanotolerant breeds of animals

Cont.
Vector control
a. Past methods
Those methods have been based on ecological
control
– vegetation clearing (destroying tsetse habitat)
– ground and aerial insecticide spraying
–selective game destruction (wild ruminants and
wild pigs)
These methods have been discouraged due to the
high costs involved in addition to being
environmentally un-friendly

Cont.
b. Baiting methods
They are more of environmentally acceptable
techniques
These include the use of insecticide impregnated
– traps or targets
– more recently, the use of 'pour-on' insecticides
(deltamethrin) applied to cattle

Cont.
 Parasite control
 Chemotherapy/Chemoprophylaxis
 Are presently the major methods of control of trypanosomosis in livestock
 Chemotherapy, by stopping the multiplication of the trypanosomes helps the
immune system to overcome the infection
• Vaccination
 So far all attempts at developing a vaccine against trypanosomosis have failed
 INTEGRATED CONTROL
 A combination of chemoprophylaxis against the disease and insecticidal
application on the cattle against the vector may greatly improve the
trypanosomosis situation

4.2. Class coccidia
 The class coccidia residing in GI epithelium, liver, kidneys,
blood cells, and other tissues of vertebrates
 They are typically intracellular with direct or indirect life
cycle.
 Those of veterinary importance fall into two distinct family
groups, the Eimeriidae and Sarcocystidae.

Some terminologies
 Oocyst: is a cyst that contains a zygote but may or may not contain
sporocyst (depending on the stage of development).
 Sporocyst: is a cyst within an oocyst which may or may not contain
sporozoite.
 Sporozoite: is the infective stage of coccidian parasite.
 Gamete: is sexual stage of protozoan parasite. It can be
microgamete or macrogamete.

Cont.
 Zygote: is a single cell stage which result from joining a male
and female sexual stages.
 Homozenous cycle: is part of life cycle where there is the
same host for the development of both sexual and asexual
stages (it is a direct life cycle).
 Heterozenous cycle: here asexual stage of development takes
place in one host and sexual stage in another and completely
different host (indirect life cycle)

Cont.
 Family Eimeriidae
 These are mainly intracellular parasites of the intestinal
epithelium.
 Schizogony and gametogony occur within the host and
sporulation, or maturation of the fertilized zygote, usually takes
place outside the host.
 three genera, Eimeria, Isospora and Cryptosporidium, are of
veterinary importance
 the term coccidiosis is usually reserved for infections caused by
Eimeria and Isospora species.

4.2.1. Genus Emeria
 Hosts: Poultry, cattle, sheep, goats, pigs and horses.
 Site: Epithelial cells of the intestine, kidney and liver.
 Distribution: Worldwide.
– The oocyst has four sporocysts each containing two sporozoites, 8 being the
total number of sporozoites.
 Important Species
 Eimeria tenella, E. necatrix, E. brunetti, E. maxima, E. mitis and E.
acervulina – chickens
 E. zuernii, E. bovis and E. alabamensis - in cattle
• E. crandallis, E. ovinoidalis, E. bak~rensis- sheep
• E arloingi and E. ninakohlyakimovue – goats

Cont.
 Identification
 This can be made at microscopic level either by examining the feces
for the presence of oocysts.
 or by examination of scrapings or histological sections of affected
tissues.
 The oocysts may be identified according to shape and size.
 The most common shapes are spherical, ovoid or ellipsoidal and the
size of the common species ranges from 15 to 50 µm.
 Oocycts have a retractile shell and some species possess a small
pore at one end called the micropyle, which is often covered by a

Cont.
 Tissue stages
 The mature schizonts may be identified histologically by their location,
size and the number of merozoites they contain.
 The merozoites arc arranged as a series of crescent-shaped organisms ( 5 .
~ 0 ; m ) rather akin to the appearance of a sliced onion.
 In contrast, in the mature microgamctocyte the microgametes are
arranged around the periphery of the cell and measure about 5.Opm in
length.
 The macrogamelocyte has a large central nucleus with small granules
arranged around the periphery of the cell.
 It is equivalent in size to the oocyst which will eventually develop from it.

Cont.
 Life cycle
 The life cycle can be direct or indirect.
 Most have a direct life cycle.
 There are three major components.
– Sporogony: this takes place in the outside environment
(multiplication in the early stage).
– Merogony: asexual reproduction within the host.
– Gametogony: sexual stage within the host.

Cont.
 The hosts get infected by the ingestion of sporulated oocyst.
 The sporozoites penetrate GIT mucosa and undergo a series of
asexual multiplication (reproduction).
 Each cycle of asexual reproduction takes place within new viable
epithelial cells and these stages are called schizonts.
 Generally, the life cycle is divided into three phases:
• Sporulation (requires 2-4 days )
• Infection and schizogony (asexual reproduction)
• Gametogony and oocyst formation (sexual reproduction)

Life cycle of Eimeria species.

4.2.2. Genus Isospora
 The genus Isospora contains many species and like Eimeria
parasitizes a wide range of hosts.
 This has an oocyst with two sporocysts each containing four
sporozoites.
 The important species include
• I. suis - pig,
• I. canis and I. ohioensis - dog
• I. felis and I. rivolta - cat.

Cont.
 The life cycle of Isospora species differs from Eimcria in three respects.
 First the sporulated oocyst contains two sporocysts each with four
sporozoites.
 Secondly, extra-intestinal stages occurring in the spleen, liver and lymph
nodes of the pig may reinvade the intestinal mucosa and cause clinical
signs.
 Thirdly, rodents may become infected by the ingestion of oocysts from
the dog and cat, with asexual stages and act as reservoirs.

4.3. Order Proplasmidia
4.3.1. Genus: Babesia
 Synonyms: Piroplasmosis, Texas fever, redwater, tick fever
 Babesiosis is caused by intraerythrocytic protozoan parasites of the genus
Babesia that infects a wide variety of vertebrate hosts, including domestic
and wild animals, as well as man.
 The disease is transmitted by ticks
 The tick species mostly incriminated as vector are Boophilus spp.
 In Ethiopia B. decoloratus is a common vector
 Other tick vectors include Rhipicephalus spp, Haemaphysalis spp.
 Distribution: worldwide in distribution.

Cont.
 Morphology
 Pear- shaped but also round or elongated.
 Inside RBCs, they are present singly or as pairs arranged at
a characteristic angle with their narrow ends opposed.
 The two organisms inside the RBC form an acute angle. In
stained smear it has a blue cytoplasm and a red chromatin
granule at one pole.
 Generally two forms are recognized:
o Small babesia ===== which have a size of 1-2.5 μm.
o Large babesia ===== which are 2.5 – 5 μm.

Cont.
 Species of babesia
 Cattle
– B. bigemina, B. bovis, B.
divergens, B. major
 Dogs
– B. canis, B. gibsoni
 Horses
– B. cabali, B. equi
 Sheep and goats
– B. motasi ,B. ovis
 Pigs
– B. trautmanni
Babesia bigemina in the red blood
cell of a cow

Life cycle and transmission
A. Final hosts
 Asexual multiplication in RBC by binary fission so that the
resulting merozoites burst the cell (erythrocytes) – the released
merozoites invade new RBCs and the cycle continues.
B. Intermediate hosts
 Ticks including Boophilus, Haemaphysalis and Rhipicephalus
are IHs.
 There are two types of transmission: transovarian and
transstadial (stage to stage).

Cont.
• Trnasstadial tranmission
 When stage-to-stage transmission occurs, vermicules again
reach the salivary glands of the next stage of the tick when
feeding commences, and mature to become infective forms.
 some species of Babesia may be transmitted through the ovary
for two or more generations of female ticks; this is known as
vertical transmission.

Bovine Babesiosis
 is a febrile, tick-borne disease of cattle, caused by one or more
protozoan parasites of the genus Babesia
 generally characterized by extensive erythrocytic lysis leading
to anemia, icterus, hemoglobinuria, and death
 Two important species in cattle including B. bigemina and B.
bovis are widespread in tropical and subtropical areas are
transmitted primarily by Boophilus ticks

Cont.
 Pathogenesis
 The rapidly dividing parasites in the red cells produce rapid destruction
of the erythrocytes with accompanying hemoglobinaemia,
hemoglobinuria and fever.
 This may be so acute as to cause death within a few days, when the
packed red cell volume falls below 20%.
 RBC destruction result in the release of pharmacologically active
substance (kinin) which results in increased vascular permeability leading
to edema.
 At necropsy, the carcass is pale and jaundiced (yellow discoloration).

Cont.
 Clinical manifestations
 Incubation period is around 2 weeks, high fever, anemia,
jaundice, haemoglobinuria, emaciation, anorexia and
restlessness, profuse diarrhea followed by constipation,
labored breathing, abortion in pregnant animals, and death due
to anaemic anoxia.

Cont.
 Diagnosis
1. Common clinical manifestations are suggestive.
2. Confirmation is by examination of blood to demonstrate the
organisms. Negative result of blood smear examination does not
indicate negative diagnosis, several smears should be examined.
3. Serological examination: CFT, ELISA, IFA, IHA
 Detection of Ag is better than Ab to confirm or know the current
status. This is be cause Abs could also be from previous exposure.
4. PCR

Cont.
 Treatment
1. Diminazine aceturate (Berenil): 2-3.5 mg/kg, IM
2. Quinoronium Sulphate (Pirevan): 1 -2 mg/kg, SC
3. Imidocarb: 1.2- 2.4 mg/kg, SC. This has therapeutic and
prophylactic use.
4. Amicarbalid: 5-10 mg/kg, IM. This is used mainly for
therapeutic use.

Cont.
 Control
 Treatment of infected animal.
 Regular spraying or dipping with acaricides. Enzootic stability
should be maintained.
 Introduction of tick resistant cattle breed.
 attenuated and non-attenuated babesia strains (B. canis) cell
culture babesia vaccine (not much commercialized)

4.3.1. Genus:Theileria
 The most important species are T. parva and T. annulata, which
cause widespread death in cattle in tropical and subtropical areas.
 The parasites, are tick transmitted, undergo repeated schizogony in
the lymphocytes, ultimately releasing small merozoites which invade
the red cells.
 Theileriosis are a group of tick borne diseases caused by Theileria sp
 Both Theileria and Babesia are members of the suborder
Piroplasmorina. While Babesia is primarily parasites of RBC,
Theileria use, successively, WBC and RBC for completion of their
life cycle in mammalian hosts.

Cont.
 The infective sporozoite stage of the parasite is transmitted
in the saliva of infected ticks as they feed. Sporozoites
invade lymphocytes (monocytes in the case of T. annulata),
within a few days, develop to schizonts.
 In the most pathogenic species of Theileria, development of
schizonts causes the host WBC to divide; at each cell
division, the parasite also divides.
 There is no transovarial transmission as occurs in Babesia.

Cont.
 Transmission
 T. parva sporozoites are injected into the host by infected ticks,
Rhipicephalus appendiculatus, during feeding.
 Based on clinical and epidemiologic parameters, 3 subtypes of T.
parva are recognized, but these are probably not true subspecies.
• T parva parva , transmitted mainly between cattle
• T parva lawrencei, transmitted mainly from buffalo to cattle, are
both highly pathogenic and can cause high levels of mortality,
whereas
• T. parva bovis , transmitted between cattle, is less pathogenic.

Cont.
 Pathogenesis, Clinical Findings, and Diagnosis
 An occult phase of 5-10 days follows before infected lymphocytes can be
detected in Giemsa-stained smears of cells aspirated from the local
draining lymph node.
 Subsequently, the number of parasitized cells increases rapidly throughout
the lymphoid system, and from about day 14 onwards, cells undergoing
merogony are observed.
 This is associated with widespread lymphocytolysis, marked lymphoid
depletion, and leukopenia.
 Piroplasms in RBC infected by the resultant merozoites assume various
forms, but typically they are small and rodshaped or oval.
 Lymph node swelling becomes pronounced and generalized.

Cont.
 Clinical signs vary according to the level of challenge and range from in
apparent or mild to severe and fatal.
 Typically, fever occurs 7-10 days after parasites are introduced by feeding
ticks, continues throughout the course of infection, and may be >42°C.
 Lymphoblasts in Giemsa-stained lymph node biopsy smears contain
multinuclear schizonts.
 Anorexia develops and the animal rapidly loses condition;
 Lacrimation and nasal discharge may occur.
 Terminally, dyspnea is common
 Just before death, a sharp fall in body temperature is usual, and
pulmonary exudate pours from the nostrils.
 Death usually occurs 18-24 days after infection.

Cont.
 Treatment and Control
 Prospects for survival of cattle with clinical East Coast fever or
T. annulata infection were enhanced by the development of the
theilericidal compound parvaquone and, subsequently, its
derivative buparvaquone.
 Treatment with these compounds is highly effective when
applied in the early stages of clinical disease but is less
effective in the advanced stages in which there is extensive
destruction of lymphoid and hematopoietic tissues.

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