Parasitology Notes PDF

PARASITOLOGY BY DR. ASMAA ADEL  RELATIONSHIPS BETWEEN ORGANISMS: Symbiosis: a close and prolonged association between two organisms of different species. It may be one of three relationships: Symbiosis: permanent association between two organisms Mutualism: two organisms living together,...

PARASITOLOGY BY DR. ASMAA ADEL  RELATIONSHIPS BETWEEN ORGANISMS: Symbiosis: a close and prolonged association between two organisms of different species. It may be one of three relationships: Symbiosis: permanent association between two organisms Mutualism: two organisms living together, the two organisms benefit. Commensalism: Two organisms Living together, one is benefited and the other is not been a ected. When the other organism become a ected, then the relationship turns = Parasitism. Zoonosis: disease of animals but can be transmitted to a man. Ex: Hymenolepis nana.  IMPORTANT TERMS USED IN PARASITOLOGY Parasite: An organism entirely dependent on another larger organism (Host) in order to have shelter and /or nutrition. Parasitology: A science that deals with parasite. Medical Parasitology: The study of parasites of medical importance that is capable of causing disease in man.  Parasite Permanent Temporary parasite parasite (e.g. head louse) (e.g. bed bugs)  Parasite Ectoparasite Endoparasite (e.g. head louse) (e.g. Entamoeba histolytica)  Parasites can be 1. Facultative parasite: parasites able to live both free living and parasite living e.g. Strongyloides species. 2. Obligate parasite : parasite living permanently in a host and cannot live without a host e.g. Trichomonos species. 3. Coprozic (spurious) parasites: foreign, pass through alimentally canal without affect. Clinical Parasitology: deals with animal parasites of man and their medical importance.  LIFE CYCLE Host: That harbours the parasite. Definitive host: a host which harbours the adult stage, the most highly developed form of the parasite or sexually mature stage of a parasite. Intermediate host: a host which harbours sexually immature or larval stage of a parasite. Reservoir host: The animal that holds the same species of parasites as man, and constitutes a source of infection to man and ensures continuity of parasite life cycle.  Habitat: The tissue ororgan in which the adult stage of parasite exists in the definitive host. Infective Stage: The stage of parasite that capable of causing infection (entering the host and continue development within it). Diagnostic Stage: it is the stage of a parasite that can be detected in stool, blood, urine, sputum, CSF,… and used in diagnosis.  VECT OR Any arthropod which transports a parasite from an infected to non- infected host. Biological vectors: Vectors that are necessary to complete the life cycle of a parasite. Mechanical Vectors: It is a passive carrier of parasites, not essential in the life cycle.  Infection: Invasion of the body by any pathogenic organism “except” arthropods. Infestation: The establishment of arthropods upon or within a host. Autoinfection:A situation where the infected individual acts as a source of infection to himself. Zoonosis: Diseases of animals that are transmittable to man. CLASSIFICATION OF THE MEDICALLY IMPORTANT PARASITES  CLASSIFICATION OF PARASITES General classification: animal parasites are classified according to international code taxonomy – Each parasite belong to a: Kingdom Phylum Class Order Family Genus Species Some have further divisions to: Sub – order, super family, sub – species in classification, scientific parasitic name is of 2 parts: Genus name and species name. Ex: Plasmodium Falciperum Genetic name (one word): plasmodium Species name (two words): plasmodium falciperum. Genus: means group of close related species. Species: means population with the same genetic characters. CLASSIFICATION OF PARASITES Parasites Protozoa Helminthes Blood and Intestinal Urogenital Cestodes Trematodes Nematodes tissue  Protozoa Intestinal Blood and tissue Urogenital tract Entamoeba Malaria histolytica Toxoplasma Trichononas Giardia lamblia Trypanosoma Vaginalis Cryptosporidium Leishmaina  SARCODINA(AMOEBAS) ENTAMOEBA HISTOLYTICA Disease: Amoebiasis Mode of locomotion : Pseudopodia (false feet) Geo. Dis.: cosmopolitan, but more common in tropical and subtropical countries and in countries with poor sanitation Habitat: in the lumen of the large intestine (it is pathogenic because it can invade the wall of intestine) Reservoir: major: humans minor: dogs, pigs, monkeys  ENTAMOEBA HISTOLYTICA Morphology: 2 forms Cyst Trophozoite Infective stage: in polluted water Pathogenic stage: give and in infected food pathology as a result of infection  LIFE CYCLE: Cyst: Inters mouth through infective stage contaminated food, drink, To L.I. lumen and fly, or through using human change into trophozoite stool as fertilizer (pathogenic stage) Can do erosion through B.V. Produce lytic enzymes to liver and (capable of doing lysis other organs Flask shape and produce ulcer) ulcer Clinical picture: Dysentery: blood+mucous diarrhea (as a result of flask shape ulcer wall invasion) Sever abdominal pain Tenesmus: sense of incomplete evacuation (the patient at this point should be seeking medical advice) Complication: A. intestinal: peritonitis, appendicitis, Hemorrhage B. Extra intestinal: Most commonly: liver hepatitis (sever right abdominal pain) Fever amoebic liver abscess (sever pathology in the liver because the inflammation spots came together) shoulder pain and Toxemic manifestations Also in lung, skin, and brain S. N Characteristics Entamoeba histolytica Entamoeba coli Trophozoite 1. Structure 2. Size 12-30 µm 20-40 µm Progressive. Hyaline, fingerlike pseudopodia Sluggish ,nondirectional Granular pseudopodia 3. Motility 4. Nucleus difficult to visualize in unstained smear often visible in unstained smear 5. Karyosome Sharp central Eccenteric Pheripheral 6. Chromatin Fine and dispersed Coarse and Clumped Cytoplasmic RBCs, leukocytes and tissue debris but no 7. Inclusions bacteria Bacteria and other material but never RBCs S. N Characteristics Entamoeba histolytica Entamoeba coli Cysts 1. Structure 2. Size 10-15 µm 15-25 µm Usually spherical, may be oval, triangular or other shaped 3. Shape Usually spherical 4. Nucleus Mature Cyst=4 nuclei Mature Cyst=8 Nuclei Peripheral 5. Chromatin Fine and dispersed Coarsely granular or clumped Chromatoid Bodies 6. Rounded ends Filamentous, thread like, pointed ends Glycogen Mass 7. Visible in uninucleate stage Large and visible in binucleate stage TRYPANOSOMA - Subphylum Mastigophora Trypanosomes parasitize the blood or tissues of many vertebrates, including humans. The most common types of Trypanosoma infecting humans are Trypanosoma gambiense and Trypanosoma rhodesiense, Trypanosoma rosea.. Disease: trypanosomaiasis Mode of locomotion : undulating movement of the flagella and undulating membrane, also the contraction and relaxation of the body parts in succession are helps in the movement Geo. Dis.: cosmopolitan, Habitat: swims in the blood plasma Intermediate host: tse tse fly Definitive host :vertebrate, man - General structure:Trypanosomes have a spindle-shaped body, pointed at both ends and fixed because of the presence of a shell covering it from the outside. The internal structure as shown in the drawing includes the cytoplasm and inside it a large oval nucleus, the flagellum, the undulating membrane which is the part of the flagellum attached to the body, the basal granule and it is located at the base of the flagellum and to the back of it there is the motor body (kinetoplast).  - Reproduction: - Trypanosomes reproduce asexually by longitudinal binary fission. ‫اﻟﺳﺎﺑق‬ ‫اﻟﺗﺎﻟﻲ‬ Infection and symptoms HAT is mostly transmitted through tsetse flies. Other possible transmission ways are: mother-to-child: trypanosomes can cross the placenta and infect the fetus; mechanical transmission by other blood-sucking insects is possible, accidental infection in laboratories via pricks with contaminated needles; and transmission through sexual contact has been reported once. Initially the trypanosomes multiply in subcutaneous tissue, blood and lymph. This is called haemo-lymphatic or first stage, which entails bouts of fever, headache, enlarged lymph nodes, joint pains and itching. Later the parasites cross the blood-brain barrier into the central nervous system causing the second stage. Generally this is when more obvious signs and symptoms of HAT appear: behaviour changes, confusion, sensory disturbances and poor coordination. Sleep cycle disturbance, which gives the disease its name, is a prominent feature. Without treatment, HAT is usually fatal although rare cases of self-cure have been reported. - Chagas disease, or American trypanosomiasis, is an illness that can cause serious heart and stomach problems. It is usually spread by infected blood- sucking bugs called triatomine bugs. They are also known as "kissing bugs" because they often bite people's faces. Disease: leishmaniaiasis Geo. Dis.: cosmopolitan, Intermediate host: sand fly Definitive host :vertebrate, man and dogs LEISHMANIA LIFE CYCLE  Giardia lamblia Distribution It has a global distribution. It is endemic in the tropics and subtropics where sanita- tion is poor. Visitors to such areas develop traveller’s diarrhoea. Habitat Giardia lamblia lives in the duodenum and upper jejunum. Morphology It exists in 2 forms:Trophozoite and Cyst Pathogenesis and Clinical Features Trophozoite does not invade the tissue, but remains adhered to intestinal epithelium by means of the sucking disc causing stunting and shortening of the villi. Patients are usually asymptomatic, but in some cases, giardiasis may cause diarrhoea, fat malabsorption (steatorrhea), dull epigastric pain and flatulence. The stool contains excess mucus and fat. Children may develop chronic diarrhoea, malabsorption of fat and vitamin A and weight loss. Incubation period is about 2 weeks. Trichomonas vaginalis Distribution It is distributed worldwide. Habitat In human, it lives mainly in the vagina and cervix of females. In males, it occurs mainly in the anterior urethra. Pathology: Causes trichomoniasis. The infection can range from mild irritation to severe inflammation. Infection is often asymptomatic, particularly in males, although some may develop urethritis ‫اﻟﺗﮭﺎب اﻻﺣﻠﯾل‬, epididymitis ‫اﻟﺗﮭﺎب اﻟﺑرﺑﺦ‬and prostatitis. In females, it may produce severe itching in the genital area with foul smelling yellowish green frothy discharge, dysuria‫ ﻋﺳر ﺑول‬, burning sensation with urination and dyspareunia‫ ﻋﺳر ﺟﻣﺎع‬. Cervical erosion‫ ﺗﺎﻛل ﻋﻧق اﻟرﺣم‬is common. The incubation period is 4 days to 4 weeks. Ciliate Balantidium coli Distribution It is distributed worldwide. Habitat Balantidium coli resides in te large intestine of humans, pigs and non-human primates. Morphology It is the largest intestinal protozoa of human. Balantidium coli exists in 2 stages— trophozoite and cyst. Pathogenesis and Clinical Features Clinical disease results when the trophozoites burrow into the intestinal mucosa and initiate inflammatory reaction. This leads to mucosal ulcers, resembling lesions in amoebiasis. Unlike E. histolytica, B. coli infection does not involve extraintestinal sites. Most infections are asymptomatic. Symptomatic disease resembles intestinal amoebiasis causing diarrhoea or dysentery with abdominal colic, nausea and vomiting. Occasionally, intestinal perforation‫ ﺗﺛﻘب اﻻﻣﻌﺎء‬and peritonitis may occur.  PLASMODIUM SP. (MALARIA) Approximately 300 million people worldwide are a ected by malaria and between 1 and 1.5 million people die from it every year Geo. Dis.: Previously extremely widespread, the malaria is now mainly confined to Africa, Asia and Latin America The problems of controlling malaria in these countries are aggravated by inadequate health structures and poor socioeconomic conditions. The situation has become even more complex over the last few years with the increase in resistance to the drugs normally used to combat the parasite that causes the disease. Causative agent: Malaria is caused by protozoan parasites of the genus Plasmodium. Species of Plasmodium are: ✔ Plasmodium falciparum the most widespread and dangerous of the four, if untreated it can lead to fatal cerebral malaria. ✔ Plasmodium vivax. ✔ Plasmodium ovale. ✔ Plasmodium malaria.  PLASMODIUM SP. (MALARIA) Transmission: Malaria parasites are transmitted from one person to another by the female Anopheles Mosquito. The males do not transmit the disease as they feed only on plant juices. Reproduction: 1. Sexually reproduction: in anopheles mosquito 2. Asexual reproduction: in human (called sporozoans) in which sporozones multiply to produce merozoites, these, in turn, become trophozoits.  LIFE CYCLE: Mosquito bite Plasmodium sporozoits are carried by After 9-16 days they develops in the gut blood to the victim's liver return to the blood and of mosquito and is where they form cyst-like penetrate the red cells, passed on in the structure containing where they multiply again, saliva of an infected thousands of merozoits progressively breaking insect down the red cells This induces bouts of fever and anemia in the infected individual. In cerebral malaria, the infected red cells obstruct the blood vessels in the brain. Other vital organs can also be damaged often leading to the death of the patient.  PLASMODIUM SP. (MALARIA) Pathology and clinical significance: When merozoits invade the blood cells, using hemoglobin as a nutrient, eventually, the infected red cells rupture, releasing merozoits that can invade other erythrocytes. If a large numbers of red cells rupture at roughly the same time, a paroxysm (sudden onset) of fever can result from the massive release of toxic substance. Plasmodium falciparum is the most dangerous species. P. malriae, P. vivax, and P. ovale cause milder form of the disease, probably because they invade either young or old red cells, but not both. This is in contrast to P. falciparum, which invades cells of all ages. Plasmodium falciparum is characterized by persistent high fever and orthostatic hypertension.‫ ارﺗﻔﺎع ﺿﻐﻂ اﻟﺪم‬Infection can lead to capillary obstruction and death if treatment is not introduced.  TOXOPLAMA GONDII Disease is called “Toxoplasmosis” Geo. Dis.: world wide Transmission: (1) eating row, undercooked meat of sheep and cow containing viable trophozoits (bradyzoits) (2) swallowing food and water contaminated with infected cat feces (3) Congenital transmission, through placenta (fatal) especially when infection occurs during pregnancy (4) person to person: ex. By blood transfusion or organ transmission Clinical symptom: -Infection of normal human hosts are common and usually asymptomatic -The infection can be very sever in immunocompromised individuals, who may also su er recrudescence (relapse) ‫اﻧﺘﻜﺎس ﻟﻠﻤﺮض‬of the infection. -Congenital infections can also be sever, and they are the major cause of blindness in newborns. Major symptoms: fever, headache, splenomegally, lymphadenopathy, hydrocephales abortion, still birth. Toxoplasmosis in immunocompromised patients may be due to reactivation of chronic or latent infection. Involvement of the brain is most common, causing toxoplasmic encephalitis. Symptoms may include headache, confusion, ataxia‫ ﺗرﻧﺢ‬, hemiparesis‫ ﺷﻠل ﻧﺻﻔﻲ‬and seizures‫ ﺻرع‬.  Helminthes Nematodes Cystods Trematodes (round worms) (flat worms) (fluks) Ascaris Bilharzia lumbricoides Taenia saginata (Schistosomiasis) (Roundworm)  Trematodes (fluks) General Characteristics Attached to their host by of suckers. The digestive system consists of a mouth and an esophagus which divides to form two intestinal caeca. For the development, eggs must reach water. Adult flukes live in the bile duct (liver flukes) intestinal tract (intestinal flukes), portal veins (blood flukes) and lung (lung flukes) according to species. Reproductive structure is similar to the tapeworm's.Sexes are separate in Schistosoma  TREMATODES BILHARZIA (SCHISTOSOMIASIS) Disease of the venous system, acquired by people when they come in contact with contaminated water Adult Schistosomes take up residence in various abdominal veins, depending on the species; they are, therefore called (Blood Flukes) Very common among children Geo. Dis.: developing countries, a ects up to 200 million people Transmission: Direct skin penetration Fresh water becomes contaminated by Schistosoma eggs when infected people urinate or defecate in the water. The eggs hatch and the parasites grow and develop inside snails. Schistosoma is not acquired by ingestion of contaminated food, it directly penetrates the skin of swimmers in contaminated rivers and lakes. 2 types of Schistosomiasis: intestinal Schistosomiasis Urinary tract Schistosomiasis Intermediate host  BILHARZIA (SCHISTOSOMIASIS) Pathology: Katayama fever Intestinal Schistosoma: the primary site of infection is the gastrointestinal tract. Damage to the intestinal wall is caused by the host’s inflammatory response to eggs deposited at that site. The eggs also secret proteolytic enzymes that further damage the tissue. Urinary tract Schistosoma: The primary site of infection are veins of the urinary bladder, where the organism eggs can induce fibrosis, granulomas, and hematuria Clinical picture: Intestinal Schistosoma: GI bleeding,‫ ﻧﺰﻳﻒ اﻟﻘﻨﺎة اﻟﻬﻀﻤﻴﺔ‬diarrhea, and liver damage. Urinary tract Schistosoma: hematuria‫اﻟﺒﻮل اﻟﺪﻣﻮي‬ Disease: Bilharzia  FASCIOLA HEPATICA Liver Flukes Fasciola hepatica (sheep liver fluke) Laboratory Diagnosis: ▪ Eggs in the faces in chronic infection ▪ Eggs in aspirates & in bile if eggs are absent in stool. Note: If eggs are found in human faces it must be confirmed that they are present due to a Fasciola infection & not from eating animal liver containing fascioliasis eggs (false fascioliasis) False Fascioliasis - due to ingestion of animal liver containing Fasciola egg, with the passage of eggs in stool, is at time mistaken for actual infection  Free-swimming Metacercariae on water 4a 4b 4c cercariae plant Sporocysts Rediae Cercariae 5 encyst on water ingested by human, plants sheep, or cattle 6 i in snail tissue 4 Snail 7 Excyst in duodenum 7 3 Miracidia hatch, 8 penetrate snail 2 d Embryonated eggs in water 8 i = Infective Stage Unembryonated eggs 1 Adults in hepatic d = Diagnostic Stage passed in faeces biliary ducts Pathogenesis and Clinical Features Fasciola hepatica causes mechanical damage due to its large size. It causes parenchymal injury while passing through the liver tissues. Humans develop severe inflammatory response as they are not its primary host. During larval migration, patients may present with fever, right upper quadrant pain, eosinophilia and hepato- megaly. The symptoms subside as parasites reach the liver. In chronic infection, patients may present with biliary obstruction, cholelithiasis‫ﺣﺻوات ﺻﻔراوﯾﺔ‬, obstructive jaundice‫اﻟﯾرﻗﺎن‬, biliary cirrhosis‫ ﺗﻠﯾف ﻛﺑدي‬and anaemia. Its larvae may undergo ectopic migration and penetrate through the diaphragm to reach the lung. Other ectopic sites include subcutaneous tissue, genitourinary tract and brain.  INTESTINAL FLUKES Heterophyes heterophyes Habitat:-Adult: In small intestine of man, cat, dog, fox Egg : In the faeces Larval forms: In fresh water snails Metacercariae: fresh water fish Requires three hosts to complete its life cycle. Definitive host: Man Intermediate host: First intermediate host: Fresh water snail such as Pirenella Second intermediate host: Brackish water fish such as Tilapia,mullet. Man acquires infection from eating infected raw fish containing metacercariae. Pathology: Each worm causes a mild inflammatory reaction at its site of contact with the intestine. In heavy infections which are common cause damage to the mucosa and produce intestinal pain and mucosa diarrhea. Sometimes eggs can enter the blood and lymph vascular systems through mucosa go into the ectopic sites in the body. The heart can be affected with tissue reaction in the valves and myocardium that cause heart failure. Eggs can also get into the brain or spinal cord and cause neurological disorders and sometimes fatalities H. heterophyes can cause intestinal infection called heterophyiasis. The infection can be asymptomatic or intestinal discomfort and mucous diarrhea ,enlarged intestinal crypts, acute to chronic inflammation, atrophy‫ﺿﻣور‬, and fusion and shortening of the intestinal villi