PPT prepared by :Dr.Prince.C.P Associate Professor & HOD , Department of Microbiology, Mother Theresa Post Graduate & Research Institute of Health Sciences (Government of Puducherry Institution) Medical Parasitology is the subject which deals with the parasites that infect human being, the diseases caused by them, clinical feature and the response generated by human being against them. It's also concerned with the various methods of their diagnosis, treatment and finally their prevention & control. An ova or cyst or egg is detected by microscopic evaluation of a stool sample that is used to look for parasites that may infect the lower digestive tract, causing symptoms such as diarrhoea. The parasites and their eggs (ova) are shed from the lower digestive tract into the stool Stool examination (Microscopic) is performed for the diagnosis of following parasitic infections 1. Protozoa • Entamoeba histolytica • Giardia lamblia • intestinal coccidian parasites (i) Cryptosporidium parvum (ii) Cyclospora (iii) Isospora • Balantidium coli 2. Helminthes • nematodes: (i) Ascaris lumbricoides (ii) Trichuris trichuria (Iii) hookworm • Ancylostoma duodenale • Nectar americans (iv) Strongyloides stercoralis Cestodes: (i) Taenia spp • T. Saginata • T.Solium (ii) Hymenolepsis nana (iii) Enterobius vermicularis

1. PARASITES
DR.PRINCE.C.P
ASSOCIATE PROFESSOR & HOD , DEPARTMENT OF MICROBIOLOGY,
MOTHER THERESA POST GRADUATE & RESEARCH INSTITUTE OF HEALTH SCIENCES
(GOVERNMENT OF PUDUCHERRY INSTITUTION)

2. Parasitology
Medical Parasitology is the subject which deals with the
parasites that infect
human being, the diseases caused by them, clinical feature
and the response generated by human being against them. It's
also concerned with the various methods of their diagnosis,
treatment and finally their prevention & control.

6. Entamoeba histolytica
• E.histolytica, the causative agent of amebiasis
• protozoan parasite that accounts for an estimated 100,000 annual deaths
globally.
• Infection ranges from mostly asymptomatic colonization of the large
bowel to invasive and potentially fatal intestinal and extra-intestinal
disease, with a special predilection for liver abscess formation.
• Diagnosis traditionally involves microscopic demonstration of the parasite
in the stool samples
• Treatment is effective with metronidazole or tinidazole, followed by a
luminal agent, such as paromomycin, to eliminate intestinal carriage.

7. Entamoeba histolytica
• It is endemic in many parts of the tropical and sub-tropical
areas. It is transmitted by the faeco-oral route. The cysts which
contain four nuclei are indicative of an infective stage in
humans. It produces amoebic dysentery which is characterized
by large, flask shaped ulcers. It may get complicated into
amoebic liver abscess and amoebic lung abscess

9. Giardia lamblia
• The protozoan parasite Giardia intestinalis, also known as G. Lamblia and G. Duodenalis.
• Transmission : Infection usually occurs through ingestion of G. Intestinalis cysts in water
(including both unfiltered drinking-water and recreational waters) or food contaminated by
the faeces of infected humans or animals.
• Nature of the disease: Many infections are asymptomatic. When symptoms occur, they are
mainly intestinal, characterized by chronic diarrhoea (watery initially, then loose greasy
stools), abdominal cramps, bloating, fatigue and weight loss.
• Geographical distribution: Worldwide.
• Diagnosis traditionally involves microscopic demonstration of the parasite in the stool
samples
• Treatment is effective with metronidazole or tinidazole

10. Giardia lamblia
• The infection with Giardia lamblia may lead to
explosive watery diarrhoea, foul smelling stools and
steatorrhoea. In endemic areas, young children are
more frequently infected than the adults, particularly
those who are malnourished. It produces a severe form
of infection in immuno-compromised individuals,
particularly in those with AIDS

12. Leishmania donovani
• haeomoflagellate parasite. In man it resides in leishmanial form in
lymphoid—macrophage (reticuloendothelial) cells of the spleen, liver,
bone- marrow, intestine and lymph glands.
• In its vector host sand fly, phlebotomous it is found in leptomonad form in
the intestine.
• The disease caused by leishmania is known as leishmaniasis or kala-
azar.
• The disease is prevalent in the eastern hemisphere specially in India,
southern U.S.S.R., Burma, central china, Iraq etc.

14. Leishmania donovani

15. MALARIA
• An infectious disease caused by protozoan parasites from the
plasmodium family that can be transmitted by the bite of the
anopheles mosquito or by a contaminated needle or
transfusion. ... The symptoms of malaria include cycles of
chills, fever, sweats, muscle aches and headache that recur
every few days.

16. Malaria
• Malaria is a life-threatening disease caused by parasites that are
transmitted to people through the bites of infected female anopheles
mosquitoes. It is preventable and curable.
• In 2018, there were an estimated 228 million cases of malaria worldwide.
• The estimated number of malaria deaths stood at 405 000 in 2018.
• Children aged under 5 years are the most vulnerable group affected by
malaria; in 2018, they accounted for 67% (272 000) of all malaria deaths
worldwide.

17. MALARIA
• Plasmodium vivax/P.Falciparum/P.Ovale/P.Malariae
• Protozoan, non motile (sporozoa)
• Virulence: intracellular parasite - invades RBC's, liver
• Transmission: bite of infected anopheles mosquito
• Complex life cycle - part in mosquito, part in human liver, RBC's
• Disease: release of parasites & toxic substances from ruptured RBC's causes high
fever, chills, vomiting, severe headaches. Occurs in approx. 3-day cycles.
• Identification: peripheral blood smear; observation parasite in RBC's

19. MALARIA -- MICROSCOPIC DIAGNOSIS
• Malaria parasites can be identified by examining under the microscope a
drop of the patient’s blood, spread out as a “blood smear” on a microscope
slide. Prior to examination, the specimen is stained (most often with the
giemsa stain) to give the parasites a distinctive appearance. This technique
remains the gold standard for laboratory confirmation of malaria. However,
it depends on the quality of the reagents, of the microscope, and on the
experience of the laboratorian.

20. TOXOPLASMOSIS - Toxoplasma gondii
• Protozoan (sporozoa) intracellular parasite
• Reservoir: birds, cats, mice, cattle, etc.
• Transmitted: usually by contact with feces of infected animal (cat), ingestion
inadequately cooked beef
• Disease: infects lymph nodes  mild inflammation
• Complication: if pregnant female becomes infected crosses placenta, infects
fetus  causes several congenital defects (neurological), spontaneous
abortions, stillbirths.

21. Toxoplasmosis

22. ROUND WORM- ASCARIS

23. ASCARIS LUMBRICOIDES
• It has a world-wide distribution and its spread occurs by the
faecal pollution of the environment. A person becomes infected
by ingesting its infective eggs through contaminated food or by
eating with contaminated hands

25. HOOKWORM
• Its infection is caused by A.Duodenale and Nectar americanus,
with Ancylostoma as the predominant species.
• The infection is spread by the faecal pollution of the soil.
• The infection occurs when the infective filariform larvae
penetrate the skin.
• Hookworm resides in the intestine and sucks blood, leading to
iron deficiency anaemia and chronic blood loss

28. Enterobius vermicularis
• It has worldwide distribution, with children being more
commonly infected than adults.
• Its transmission is by the injestion of infective eggs.
• The eggs are deposited on the anal skin usually during the
night hours.
• An autoinfection is common in children because the eggs
cause intense irritation and scratching in the infected anal area

29. The adhesive tape method
• This is useful for the detection of the eggs of E.Vermicularis.
The eggs can be collected by wrapping a strip of clear
adhesive tape (Eg. Cellotape, scotch tape) around the anus.
After collecting the eggs, the tape should be sticked
lengthways, face down on a microscope slide. Alternatively, an
anal or perianal specimen can be collected by using a national
institute of health (NIH) swab

31. Guinea-worm
• Guinea-worm disease is caused by the parasitic worm Dracunculus
medinensis or "guinea-worm".
• This worm is the largest of the tissue parasite affecting humans.
• The adult female, which carries about 3 million embryos, can measure
600 to 800 mm in length and 2 mm in diameter.
• The parasite migrates through the victim's subcutaneous tissues causing
severe pain especially when it occurs in the joints. The worm eventually
emerges (from the feet in most of the cases), causing an intensely painful
oedema, a blister and an ulcer accompanied by fever, nausea and
vomiting.

34. LYMPHATIC FILARIASIS
• Commonly known as elephantiasis, is a painful and profoundly
disfiguring disease.
• In communities where filariasis is transmitted, all ages are affected.
• While the infection may be acquired during childhood its visible
manifestations may occur later in life, causing temporary or
permanent disability.
• In endemic countries, lymphatic filariasis has a major social and
economic impact

35. LYMPHATIC FILARIASIS
• The disease is caused by three species of thread-like nematode worms, known as
filariae – Wuchereria bancrofti, Brugia malayi and Brugia timori.
• Male worms are about 3–4 centimetres in length, and female worms 8–10 centimetres.
The male and female worms together form “nests” in the human lymphatic system, the
network of nodes and vessels that maintain the delicate fluid balance between blood and
body tissues.
• Filarial infection can cause a variety of clinical manifestations, including lymphoedema of
the limbs, genital disease (hydrocele, chylocele, and swelling of the scrotum and penis)
and recurrent acute attacks, which are extremely painful and are accompanied by fever.
• The vast majority of infected people are asymptomatic, but virtually all of them have
subclinical lymphatic damage and as many as 40% have kidney damage, with
proteinuria and haematuria.

36. LYMPHATIC FILARIASIS- VECTORS
• Adult male and female worms lodge in the lymphatics. Fecund females release larvae
(microfilaria) which periodically circulate in the blood. Microfilaria circulating in the blood
can be ingested by feeding mosquito vectors. Microfilaria must mature in the vector
before becoming infective. The mosquitoes can then spread infective larvae to new
hosts when feeding.
• The major vectors of W. bancrofti are mosquitoes of the genus Culex (in urban and
semi-urban areas), anopheles (in rural areas of africa and elsewhere) and Aedes (in
islands of the pacific).
• The parasites of B. Malayi are transmitted by various mosquito species of the
genus Mansonia; in some areas, Anopheline mosquitoes are responsible for transmitting
infection. Brugian parasites are confined to areas of east and south Asia, notably India,

39. LYMPHATIC FILARIASIS --TREATMENT
• The primary goal of treating affected communities is to eliminate microfilariae from the blood
of infected individuals in order to interrupt transmission of infection by mosquitoes.
• Preventive chemotherapy involves a combined dose of two medicines given annually to an
entire at-risk population as follows: albendazole (400 mg) plus ivermectin (150–200 μg/kg) or
diethylcarbamazine citrate (DEC) (6 mg/kg). MDA with albendazole (400 mg) alone should be
given preferably twice per year to stop the spread of lymphatic filariasis in areas where loa
loa is present.
• Individuals
• All people with filariasis who have microfilaraemia or a positive antigen test should receive
antifilarial drug treatment to eliminate microfilariae. Unfortunately, the medicines available
have limited effect on adult worms. Infected patients can be treated with one of the following
regimens:
• A single dose of a combination albendazole (400 mg) plus diethylcarbamazine (6 mg/kg) or
DEC (6 mg/kg) alone for 12 days.

40. LYMPHATIC FILARIASIS- DIAGNOSIS
&PREVENTION
• Diagnosis by peripheral blood smear examination for
Microfilaria (night blood sampling)
• Avoidance of mosquito bites through personal protection
measures or community-level vector control and participation
in Mass drug administration (MDA) is the best option to
prevent lymphatic filariasis.

41. TAENIA SPP.
• Two species, namely T.Saginata and T.Solium, are responsible for
the infections in humans.
• The infection is mainly transmitted by eating raw or insufficiently
cooked beef and pork meat respectively.
• T.Solium is not as widely distributed as T.Saginata, but it can
produce a serious infection called neurocysticercosis, which causes
epilepsy and other central nervous disorders

43. ECHINOCOCCOSIS ---HYDATID DISEASE
• A Dog tapeworm (Echinococcus) infection that affects the liver, lungs, brain and
other organs.
• Echinococcosis is spread by contact with animal faeces contaminated with
tapeworm eggs. Sources include contaminated food, water and animal fur.
• Cysts containing tapeworm larvae may grow in the body for years before
symptoms appear. When cysts become large, they may cause nausea,
weakness, coughing and stomach or chest pain.
• Treatment may include surgery, removal of fluid from the cysts and medication.

44. HYDATID CYST

46. EXAMINATION OF THE STOOL FOR
PARASITES
• Stool examination (Microscopic) is performed for the diagnosis of
following parasitic infections
• 1. Protozoa • Entamoeba histolytica • Giardia lamblia • intestinal
coccidian parasites (i) Cryptosporidium parvum (ii) Cyclospora (iii)
Isospora • Balantidium coli
• 2. Helminthes • nematodes: (i) Ascaris lumbricoides (ii) Trichuris
trichuria
• (Iii) hookworm • Ancylostoma duodenale • Nectar americans (iv)
Strongyloides stercoralis
• Cestodes: (i) Taenia spp • T. Saginata • T.Solium (ii) Hymenolepsis
nana (iii) Enterobius vermicularis

47. Examination of the stool for parasites
• An ova or cyst or egg is detected by microscopic evaluation of
a stool sample that is used to look for parasites that may infect
the lower digestive tract, causing symptoms such as diarrhoea.
The parasites and their eggs (ova) are shed from the lower
digestive tract into the stool

48. Examination of the stool for parasites- Methods
1.MACROSCOPIC EXAMINATION
• Various points which have to be noted are:
• Consistency: formed, unformed (soft), loose or watery. The cysts have been mostly found in
the formed stools, while trophozoites have been most abundantly found in watery stools.
• The presence of blood, mucus or pus.
• The presence of worms, e.G. Enterobius vermicularis, ascaris, tapeworm segments, e.G.
Taenia species.
• Colour (white, yellow, brown or black).
• Normal faeces appear brown and formed or semiformed. Infant faeces are yellow-green and
semiformed

49. Examination of the stool for parasites- Methods
2.MICROSCOPIC METHODS
• 1. Saline wet mount: it is used to detect worms, bile stained eggs, larvae, protozoan
trophozoites and cysts. In addition, it can reveal the presence of rbcs and wbcs.
• 2. Iodine wet mount: it is used to stain the glycogen and nuclei of the cysts. A cyst is
appreciated better in an iodine preparation, but the motility of the trophozoite is inhibited in
the iodine preparation.
• Procedure • place a drop of saline on the left half of the slide and one drop of iodine on the
right half. • With an applicator stick, pick up a small portion of the specimen (equivalent to the
size of a match head) and mix it with a saline drop. • Similarly, pick up a similar amount and
mix with a drop of iodine. • Put the cover slip separately on both and examine under the
microscope. • The ova, cysts, trophozoites and adult worms can be identified as per their
characteristic features.

50. Examination of the stool for parasites- Methods
• 3. STOOL CONCENTRATION TECHNIQUES
• If the number of parasites in the stool specimens is low, the examination of a direct wet
mount may not reveal them and hence the stool should be concentrated. Eggs, cysts and
larvae can be recovered after the concentration procedure, whereas trophozoites can get
destroyed during this procedure. This makes a direct wet mount examination obligatory
as the initial phase of the microscopic examination.
• The concentration procedures can be grouped under 2 categories:
• 1. Sedimentation procedures: in which the eggs and cysts settle down at the bottom.
• 2. Flotation procedures: in which the eggs and cysts float at the surface due to the
specific gravity gradient.

51. Entamoeba histolytica-
Trophozoite and cyst

52. Giardia lamblia
trophozoite & cyst

53. Helminth eggs

54. THANK YOU