1.
Sahibzada Tasleem Rasool

2.
Symbiosis
------The relationship between two living things
(animals). Two living things live together and involve
protection or other advantages to one or both partner.
 Commensalism
 Mutualism
 Parasitism*

3.
Host and type of host
 Host : An organism that harbors the parasite usually
larger than the parasite.
 Intermediate host : The host harboring the larvae or
asexual stage of parasite.
 Final host : The host harboring adult or sexual stage of
parasite.
 Reservoir host : Animals harboring the same species of
parasites as man. Potential sources of human infection.

4.
 Life cycle : The whole process of parasite growing and
developing.
 The direct life-cycle : Only one host (no intermediate
host).
 The indirect life cycle : Life cycle with more than one
host (intermediate host and final host).

5.
Medical Parasitology is the study of the invertebrate
animals and the diseases they cause. Parasites are classified
as
• Protozoans…….Protozoa (Chapter 21)
• Metazoans………include Helminths (Worms) (chapter 22)
• Arthopds…… Lice, Mites etc.
A parasite: “a living organism that acquires some of
its basic nutritional requirements through its intimate
contact with another living organism”.

6.
Parasite and the type of parasites
 Parasite: It is an animal that is dependent
on another animal (host) for its
survival.
 Type of parasites
Protozoa --------------Endoparasite
Parasites Helminth
--------Ectoparasite
Arthropods

7.
A group of eukaryotic microorganisms traditionally
classified in the animal kingdom. Protozoa are almost
as widely distributed as bacteria. Free-living types
occur in soil, wet sand, and in fresh, brackish, and salt
waters. Protozoa of the soil and sand live in films of
moisture on the particles.

8.
Intestinal and urogenital Blood and Tissue
AMOEBAE FLAGELLATES
Entamoeba histolytica Giardia lamblia
Trichomonas vaginalis
PLASMODIUM
TOXOPLASMA GONDII
LEISHMANIA
TRYPANOSOMES

9.
Intestinal protozoa are transmitted by the fecal-oral route and tend
to exhibit similar life cycles consisting of
• Cyst stage
• Trophozoite stage.
• Cyst stage ….Cysts are characterized by a resistant wall and are
excreted with the feces. The cyst wall functions to protect the
organism from dehydration in the external environment as the
parasite undergoes a relatively dormant.
• Trophozoite stage….Trophozoites are the active, motile feeding
stage of a intestinal parasites.

10.
Transmitted by the faecal-oral route and cause
diarrhoea
may invade the colon
and cause bloody diarrhoea – amoebic dysentery.
Symptoms : Diarrhea, cramps, flatulence, nausea, and
anorexia. Numerous stools per day with blood and
mucous, but there is no visible blood. Also causes
ameobic liver abscess.

11.
Entamoeba histolytica
• Amebiasis: Amoebic dysentery…Inverted flask-shaped lesions in
large intestine with extension to peritoneum and liver, lungs,
brain, and heart. Blood and pus in stools.
• Liver abscesses.. Small necrotic foci, unite to
form an abscess in the liver. Liver is primarily involved because
trophozoites in blood are removed via the portal circulation
through this organ.
Diseases
Form / Transmission
Cysts / Fecal-oral transmission water, fresh fruits, and vegetables
Treatment
Metronidazole followed by iodoquinol

12.
• Supportive treatment: Rehydration, electrolyte
compensation and antispasmodics.
• Specific treatment:
i. Metronidazole (Flagyl): …for 5-10 days
ii. Tinidazole (Fasigyn): …..for 2-3 days
Both followed by iodoquinol (used also for
asymptomatic carriers or cyst passers).
Antibiotics:..Tetracyclines and erythromycin.

13.
• It was probably the first symbiotic protozoan ever observed
world-wide distribution.
• It lives in the upper portion of the small intestine and results
in malabsorption. Move by the lashing of flagella.
• Mostly cause non-invasive diseases (unlike amoeba), only
mechanical irritation and inflammation.
• Acquired by drinking contaminated water, ingestion of
contaminated vegetables or fruits, or person-to-person
spread by the feco-oral routes.
• Cyst is resistant to chlorine

14.
• Foul-smelling, watery diarrhea, abdominal cramps.
• May lead to severe malabsorption syndrome:
a. Weight loss, fatigue.
b. Fatty stools (steatorrhoea) due to diminished intestinal
absorption of fatty acids giving the stools pale yellow frothy
appearance.
Clinical Syndromes
Cysts and trophozoites in stool.
Laboratory Diagnosis
• Drug of choice is quinacrine or metronidazole.
• Treatment of all infected persons at the same time e.g.
family members.
Treatment

15.
• No cyst, only as a trophozoite
• Found in urethras and vaginas of women and urethras and prostate
glands of men.
• Acidity of normal vagina (pH 4.0-4.5) usually discourages
infection but once established the parasite causes a shift towards
alkalinity (pH 5.0-6.0) which encourages further growth.
1. Sexual intercourse
2. Fomites
3. From mother to her infant through mother's infected birth
canal.

16.
1. Mostly asymptomatic, may cause seropurulent, watery vaginal
discharge, itching and painful urination.
2. Men serve as reservoir for infections in women. Men
occasionally experience urethritis, prostatitis.
Laboratory Diagnosis
Trophozoite in vaginal or urethral
discharge. (typical tumbling
movements)
Treatment, Prevention, and Control
1. Metronidazole (contraindicated in pregnancy and lactation)
2. Pessaries and acid douches in female treatment.
3. Both sexual partners should be treated.
Clinical Symptoms

17.
Blood and Tissue Protozoa
: the cause of malaria. There are 4 species
that infect man: P. falciparum, P. vivax, P. ovale and P.
malariae
: transmitted by the ingestion of
Infection can lead to ocular problems
and is also a
transmitted by sand flies, can lead to visceral,
cutaneous and mucocutaneous leishmaniasis
haemoflagellates which cause
– In Africa - sleeping sickness (transmitted by the Tsetse fly)
– In South America - Chagas disease (transmitted by the
Reduviid bug)

18.
• Sporozoan parasites reproduce sexually and asexually in alternate
generations by means of spores
Require two hosts:
• Mosquito: for sexual reproductive stages (sporogony
host).. production of sporozoites.
• Humans and other animals: for asexual reproductive stages
(schizogony host)…asexual reproduction by multiple fission
Infection initiated by female Anopheles mosquito’s bite, which
introduces sporozoites via its saliva into circulatory system
(??infective stage).
Blood and Tissue Protozoa

19.
• Flu-like symptoms with headache, muscle pains, photophobia,
anorexia, nausea, and vomiting. Anemia is seen in pateints.
• As the infection progresses, increased numbers of rupturing
erythrocytes liberate merozoites and toxic cellular debris ...leading
to bouts of chills and fever.
• Paroxysms happen every 72 hours in P. malariae and 24 hours in
other species.
Malaria can acquired by:
1. Transmission by mosquitoes
2. Blood transfusions from infected donor.
3. Among narcotic addicts who share needles and syringes.
4. Congenital acquisition, although rare, is also a possible mode
of transmission (congenital malaria).

20.
If untreated, chronic infections by P. vivax, P. ovale, P. malariae cause
:
• Brain, kidney, and liver damage as a result of the malarial
pigment, cellular debris.
• Capillary plugging of these organs by masses of adherent
erythrocytes.
- P. falciparum infections likely to be fatal, if untreated:
• brain: Capillary plugging leads to coma and death.
• Kidney: renal failure and death.
• liver: vomiting of bile, severe diarrhea, and dehydration.
Laboratory Diagnosis
Microscopic examination of thick and thin films of blood (taken
between paroxysms) to identify species.

21.
Supportive therapy :
a. Bed rest, relief of fever and headache.
b. In the cold stage hot water bottles and extra blankets may
bevneeded. In the hot stage apply ice-bags.
c. Regulation of fluid balance.
d. Blood transfusion in severe hemolytic anaemia.
Chemotherapy:
- Ideal treatment should:
*destroy erythrocytic forms to cure the malarial attack.
*destroy exoerythrocytic forms to prevent relapses.

22.
- A combination of two drugs is needed:
• Chloroquine for clinical cure of primary malarial attack. acts
on erythrocytic forms.
• * Followed by primaquine acts on exoerythrocytic forms in
liver to prevent relapses.
Chemoprophylaxis:
• For persons visiting an endemic area or for people living an
area where malarial outbreak is reported.
• Chloroquine is given two weeks before entering the endemic
area, during the stay, and two weeks after leaving the endemic
area.
• Fansidar® (pyrimethamine and sulfadoxine) is given one tablet is
given once weekly for resitant strains.

23.
Diagnosis and Treatment of Malaria
The diagnosis of malaria is based on multiple symptoms but
eventually must be made from detection of the parasite via
laboratory tests. Diagnostic kits using a dye-labeled antibody
that binds to the parasite are also available and are especially
useful in the field and for rapid diagnoses.
The most effective new drugs are currently the most effective
agents against multi-resistant malaria strains. However, these
drugs are very expensive and are not yet widely available

24.
T. gondii is important because virtually all warm-blooded
animals, including man, can become infected with it.
Domestic, wild, and cats can transmit Toxoplasma
infection to humans.
Symptoms of toxoplasmosis include
• Anorexia
• Weight loss
• Lethargy
• Difficulty breathing (because of pneumonia)
• Fever.

25.
In mothers who first acquire Toxoplasma infection during their
pregnancy, about one-third to one-half of the infants are also
infected, and the disease is most severe, if the mother has
been infected during the first trimester of pregnancy.
Treatment
Pyrimethamine and sulfadiazine are the two drugs used to treat
toxoplasmosis. They act together to inhibit Toxoplasma
reproduction.
Another choice is the antibiotic clindamycin, which has fewer
side effects.

26.
Leishmania are parasites transmitted by the bite of the
small sand fly.
Leishmaniasis is an important disease and the parasite is
transmitted by blood-sucking sand flies with approximately
two million new cases every year and one tenth of the
world's population at risk of infection.

27.
The symptoms of leishmaniasis are skin sores which
erupt weeks to months after the person affected is bitten
by sand flies.

28.
Leishmania
Leishmania is found always as amastigotes in macrophages.
Amastigotes
Leishmania donovani causes Viceral Leishmaniasis also
called Kalazar
The disease spreads by Sandfly bite. Amastigotes in
macrophages in bone marrow, liver and spleen.
Other species of Leishmania can result in Cutaneous Leishmaniasis
Treatment .. Stibogluconate sodium
Leishmania braziliensis can cause Mucocutaneous Leishmaniasis which
may spread by Sandfly bite.

29.
In contrast to the protozoa, helminths (worms and
flukes) are multicellular. The word helminth comes
from Greek hélmins, a kind of worm.
Parasitic worms are categorized into three groups
• Tapeworms (Cestodes)
• Round worms (Nematodes)
• Flukes (Trematodes.)

30.
Although Parasitic worms can cause severe clinical disease,
they usually persist as chronic infections and have insidious
effects on growth and development that rarely cause
attendance at health centres.
Parasitic infections affect more than two billion people with
lifelong infections, most of which are in underdeveloped and
developing countries….especially those where human
faeces is used as fertilizer.
Helminthic Infections

31.
Cestodes – pig and cattle "tapeworms"
Adult tapeworms are elongated and their body is segmented
and they are flat.
Theses inhabit the intestinal lumen. Larval forms, which are
cystic or solid, inhabit extra-intestinal tissues.
Taenia Solium
Taenia Saginata

32.
Taenia Saginata – Beef Tapeworm.
• Infects cattle and humans, and can only reproduce while in
the human gut.
• Humans acquire the infective larvae from eating
undercooked meat.
• T. Saginata is normally 3 m to 5 m in length, but can become
very large, over 20 m long in some situations.
• The life cycle is completed in humans as the definitive host
and cattle as the intermediate host.
Diagnosis
The basic diagnosis is done from a stool sample. Faeces are
examined to find parasite eggs.
Treatment
Praziquantel opens membrane calcium channels causing
paralysis of the worm, aiding the body in expelling the
parasite through peristalsis.

33.
Round worms (Nematodes)
• Nematodes are simple roundworms. In size they range
from 0.3 mm to over 8 meters.
• Roundworms are bisexual, cylindrical, colorless and
unsegmented worms.
• Many of the parasitic species cause important diseases
of plants, animals, and humans.
• They inhabit intestinal and extraintestinal sites.
• Roundworm infections are more common in warm,
tropical climates than in cooler, temperate areas of the
world.

34.
Nematodes commonly parasitic on humans include
• Ascarids (Ascaris), ……Ascaris lumbricoides
• Filarids,
• Hookworms,
• Pinworms (Enterobius)
• Whipworms (Trichuris trichiura).

35.
Ascaris lumbricoides Giant roundworm of
human
• Most common helminth worldwide
• The disease ascariasis spreads through
Ingestion of egg ~ larva which migrate thru lungs
(cough) and mature in small intestine.
• They can grow in number and size and may
obstruct intestine or bile duct.

36.
Ascaris lumbricoides
Most diagnoses are made by identifying the appearance of
the worm or eggs in feces. Due to the large quantity of eggs
laid physicians can diagnose using only one or two fecal
smears.
The treatment of choice is Mebendazole
Ascariasis
I. Cough
II. Shortness of breath
III.Abdominal pain
IV.Nausea and diarrhea
V. Blood in the stool
VI.Weight loss
VII.Fatigue
VIII.Presence of worm in vomit or stool

37.
Filarids Wuchereria bancrofti
Brugia malayi
Wuchereria bancrofti and Brugia malayi are filarial
nematode worms which spread by a mosquito vector.
W. bancrofti is responsible for 90% of lymphatic filariasis.
Lymphatic filariasis or Elephantiasis is an infection of
the lymphatic system caused by these filarial worms.
Elephantiasis, is a condition characterized by swelling
of the lower limbs. It is not fatal but 40 million disfigured
or incapacitated.

38.
TREATMENT
Single doses of diethylcarbamazine (DEC) administered
concurrently with albendazole. is 99% effective in removing
microfilariae from the blood for a full year after treatment.
Elephantiasis

39.
Hookworms Ancylostoma duodenale
Necator americanus
More than 1200m infections each year of which 100m
are symptomatic. Adult worms live in the intestine
and excrete eggs in the faeces.
On contact with the
human host, the larvae
penetrate the skin and
are carried through the
blood vessels to the
heart and then to the
lungs. They penetrate
into the pulmonary
alveoli, ascend the
bronchial tree to the
pharynx, and are
swallowed.

40.
• Often itchy papules are found at the site where the larva
penetrated the skin
• There may be cough and wheezing as the larva migrates
through the lungs
• Hookworm anaemia
– Tiredness, aches and pains, Pallor, Breathlessness,
Oedema
• Measure serum Hb and exclude other causes of anaemia.
• Microscopic examination of faecal smears to demonstrate
significant numbers of hook worm eggs.
• Mebendazole (cheap) – 100mg, twice daily for 3 days

41.
(whipworm) The name whipworm refers to the
shape of the worm.
• A soil transmitted helminth, prevalent in warm and humid
conditions. It causes trichuriasis when it infects a human
large intestine.
• Can cause diarrhoea, rectal prolapse and anaemia in
heavily-infected people
Diagnosis
Trichuriasis can be diagnosed when T. trichiura eggs
are detected in stool examination
TREATMENT
Mebendazole is 90% effective in the first dose

42.
Flukes (Trematodes)
Trematodes
 Are commonly called flukes.
 Are leaf-shaped worms, which are generally flat and fleshy.
 Are hermaphroditic except for Schistosoma, which has
separate male and female. .
 Have complicated life cycles occurring in two or more hosts.
 The most important species pathogenic to humans are
Schistosoma hematobium and Schistosoma mansoni.
 The first intermediate hosts are snails.

43.
According to WHOTechnical Report Series No. 830. Geneva: World Health
Organization; 1993
Schistosoma

44.
Schistosomes remain in the definitive host for an average of
two to five years, but in some cases for as long as 20–40
years.
Schistosoma

45.
The main forms of schistosomosis are differentiated
according to the localization of the lesions:
Urinary schistosomosis (urinary bilharziosis). Causative
agent: S. hematobium.
Intestinal schistosomosis (intestinal bilharziosis). Causative
agent: mainly S. mansoni
Diagnosis. The eggs can be detected in stool specimens or in
urine sediment
Therapy. The drug of choice for treatment of schistosomosis is
praziquantel, which is highly effective against all Schistosoma
species and is well tolerated.
Oxamniquine is effective against S. mansoni.
Schistosoma

46.
Parasitic arthropods are ectoparasites that have a
temporary or permanent association with their hosts.
Their considerable medical significance is due to their
capability to cause nuisance.
Some species or stages of arthropods are capable of
penetrating to deeper skin layers or into body openings or
wounds.

47.
Infestation with Sarcoptes scabiei causes human scabies, a
condition characterized by pronounced pruritus, epidermal mite
burrows, nodules, and pustules.
Transmission is by close contact (sexual partners, family members,
school children, healthcare staff) from person to person, whereby
female mites translocate to the skin of a new host.
Pruritus is particularly bothersome in the evening when body heat
is retained under the bedcovers. Itching mainly occurs in the
interdigital spaces and on the sides of the fingers, on the wrists and
ankles and in the genital region.
Scabies

48.
Diagnosis. Case history and clinical manifestations provide
important diagnostic hints that require etiological confirmation
by identification of the parasites
Therapy requires topical application of
c-hexachlorocyclohexane (lindane), permethrin or crotamiton
in strict accordance with manufacturer’s instructions. A recent
development is per-oral therapy with ivermectin. Underclothing
and bed linens must be washed at a minimum temperature of
50° C.
Control.
Scabies

49.
Fungi

50.
Fungi
Mycology
• Fungi are eukaryotic microorganisms (domain eucarya) that
occur ubiquitously in nature.
• Only about 200 of the thousands of species have been
identified as human pathogens, and among these known
pathogenic species fewer than a dozen are responsible for
more than 90% of all human fungal infections.
• The basic form of a unicellular fungus is the yeast cell.
• The cell walls of fungi consist of nearly 90% carbohydrate
(chitin, glucans, mannans) and fungal membranes are rich in
sterol types not found in other biological membranes (e.g.,
ergosterol).

51.
Basic Morphological
Elements of Fungi

52.
General Aspects of Fungal Disease
Besides fungal allergies fungal infections are by far the most
frequent fungal diseases.
Mycoses are classified clinically as follows:
• Primary mycoses histoplasmosis, blastomycoses).
• Opportunistic mycoses (surface and deep yeast
mycoses, aspergillosis, pneumocystosis).
• Subcutaneous mycoses
• Cutaneous mycoses (dermatomycoses).

53.
Most Important Mycoses in Humans
Remarks
Etiology
Disease
Pulmonary mycosis. Inhalation
of spores. Dissemination into
RES. America, Asia, Africa
Histoplasma
capsulatum
Histoplasmosis
Endogenous infection. Primary
infection of mucosa and skin
with secondary dissemination
Candida albicans,
other Candida sp.
Candidiasis
Aspergilloses of the respiratory
tract, endophthalmitis;
aspergillosis
of CNS; septic aspergillosis
Aspergillus
fumigatus (90 %);
Aspergillosis
Infections of various organs in
immunosuppressed patients.
Sepsis also possible.
Torulopsis glabrata;
Trichosporon eigelii
Yeast mycoses
(except candidiasis)

54.
Clinical Groupings for Fungal Infectios
 Besides fungal allergies, fungal infections can
lead to several diseases.
 A. Skin Mycology:
1- Superficial Mycoses: infections of skin or hair. No
living tissue is invaded and there is no cellular
response from the host, e.g. tinea nigra disease in the
hand palm.
2- Cutaneous Mycoses: superficial fungal infections of
skin, hair or nails. No living tissue is invaded, however
a variety of pathological changes occur in host because
of the presence of the infectious agent and its
metabolic products, e.g. Dermatophytosis (tinea) of
scalp, skin and nails.
3- Subcutaneous Mycoses: e.g. Zygomycosis

55.
Tinea nigra
Tinea pedis (athlete's foot)
Tinea capitis with
extensive hair loss

56.
is a chronic inflammatory disease
that is typically restricted to the
nasal submucosa and
characterized by restricted
subcutaneous masses. Symptoms
include nasal obstruction,
drainage and sinus pain
(predominant in males).
Zygomycosis caused by Conidiobolus sp.

57.
B- Dimorphic Systemic Mycoses
 Dimorphic fungal pathogens which can overcome the physiological and
cellular defenses of the normal human host by changing their
morphological form.
 Primary site of infection is usually pulmonary, following the inhalation
of conidia (asexual spores).
C. Opportunistic Systemic Mycoses
- Candidiasis is an infection caused by a species of the yeast Candida
albicans.
- Candidiasis can affect the skin, nails, and mucous membranes throughout
the body including the mouth (thrush), esophagus, vagina (yeast
infection), intestines, and lungs

58.
Thrush mouth in immuno-
suppressed patient
Cutaneous candidiasis,
Interdigital candidiasis
Moisture, heat, friction of the skin are the principle predisposing
factors in the normal patient, however obesity, diabetes mellitus,
warm water immersion and the use of broad-spectrum antibiotics
are additional factors.

59.
Differences between Fungi and Bacteria
Bacteria
Fungi
Propertie
s
Prokaryotic; no membrane;
nucleoid; only one
“chromosome
Eukaryotic; nuclear
membrane; more than one
chromosome; mitosis
Nucleus
No mitochondria;
no endoplasmic reticulum;
70S ribosomes,
Mitochondria; endoplasmic
reticulum; 80S ribosomes
Cytoplasm
No sterols
Sterols (ergosterol)
Cytoplasmic
membrane
Murein, teichoic acids
(Gram-positive), proteins
Glucans, mannans, chitin,
chitosan
Cell wall
Heterotrophic; obligate
aerobes and anaerobes,
facultative anaerobes
Heterotrophic;
mostly aerobes;
no photosynthesis
Metabolism

60.
Therapy
A limited number of anti-infective agents are available for
specific treatment of fungal infections:
Polyenes. These agents bind to membrane sterols and destroy the
membrane Structure…… Amphotericin B, Nystatin, natamycin.
Azoles. These agents disrupt ergosterol biosynthesis. Their effect is
mainly fungistatic…… Ketoconazole… Good activity against Candida and Aspergillus.
Antimetabolites. 5-Fluorocytosine… (base analog) Interferes with DNA
synthesis
Griseofulvin. This is an older antibiotic used in treatment of
dermatomycoses. By oral application, therapy must often be continued
for months.