Protozoa and Helminth Parasites ppt by Dr.Prince.C.P

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.

3. 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.

4. 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

5. 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

6. 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

7. 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 .

8. Leishmania donovani

9. 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.

10. 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 .

11. 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

12. 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 .

13. 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.

14. Toxoplasmosis

15. Round worm- Ascaris

16. 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

17. 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

18. 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

19. 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

20. 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.

21. 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

22. Lymphatic filariasis The disease is caused by three species of thread-like nematode worms, known as filariae –   W uchereria 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 .

23. 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, Indonesia, Malaysia and Thailand.

24. 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.

25. 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 .

26. 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

27. 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.

28. Hydatid cyst

29. 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

30. 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

31. 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

32. 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.

33. 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.

34. Entamoeba histolytica- Trophozoite and cyst

35. Giardia lamblia trophozoite & cyst

36. Helminth eggs

37. Thank you