Parasitology BIO 451 ١ 1- Symbiosis: Two different organisms live together and interact, in this association one partner lives in or on another one one s body. It includes 3 types: A. Mutualism, B. Commensalism, C. Parasitism. ٢ 1
1- Symbiosis: A. Mutualism. Is a permanent association between two different organisms that life apart is impossible, two partners benefit each other, such as termites and flagellates. The mutuals are metabolically dependent on one another; one cannot survive in the absence of the other. ٣ 1- Symbiosis: A.Mutualism. (termites and flagellates) ٤ 2
1- Symbiosis: B. Commensalism. Is the association of two different organisms, in which one partner is benefited while the other neither benefited nor injured, such as E. coli and man. 5 Shark and Remora Anemone and Fish 1- Symbiosis: C. Parasitism. Is the association of two different organisms, in which one partner is benefited while the other is injured, such as Ascaris lumbricoides and man. Ascaris Mosquito ٦ 3
2- Parasite: In parasitism, it is the benefited partner. It is an animal organism which lives in or on the host in order to obtain nourishment and shelter from the host as well as does harms to the host. ٧ Endoparasite Ectoparasite 2- Parasite: Types of parasites: a. Endoparasite A parasite living within the host. b. Ectoparasite A parasite that is found on the surface of the body. c. Temporary parasite A parasite that obligatory parasitizes at one or more stages of its life cycle but free living at others. d. Permanent parasite A parasite that all stages of its life cycle permanently parasitize a host. Have no free living stages. e. Obligatory parasite A parasite which totally dependent on others for survival. f. Facultative parasite An organism that lives independent of a host but may occasionally be parasitic under certain conditions. g. Accidental parasite A parasite that parasitizes an organism other than the usual host. ٨ 4
3- Host: In parasitism, it supplies the parasite with nourishment and shelter, it is the injured partner. 4- Carrier: A person who harbours parasite has no clinical symptoms, is an important source of infection in epidemiology. 5- Definitive (final) host: Host harbours adult or sexually reproductive stage of a parasite. ٩ 6- Intermediate host: Host harbours larval or asexually reproductive stage of a parasite, according to priority they are classified into: first intermediate host, second intermediate host, third intermediate host etc... 7- Reservoir host: Hosts are the vertebrate hosts which harbour the same species of parasite at same stage as a human host. They are an important source of infection in epidemiology. ١٠ 5
8- Zoonosis: Zoonosis refers to animal s s diseases which can be transmitted to man. These animals infected with parasites are called reservoir hosts. 9- Paratenic host or transport host: Is an abnormal host in which some parasitic larvae can survive but can t t develop into adults. If the larvae have a chance to enter their appropriate hosts, they can continue to develop into adults there. ١١ 10- Larva migrans: Means that the larvae living in their abnormal hosts in which they can not grow into adults but can wander everywhere and cause the local and systemic pathological lesions of the hosts. 11- Life cycle: Is the process of a parasite s s growth, development and reproduction, which proceeds in one or more different hosts depending on the species of parasites. ١٢ 6
12- Infective stage: Is a stage when a parasite can invade human body and live in it. 13- Infective route: Is the specific entrance through which the parasite invades the human body. 14- Infective mode: Means how the parasite invades human body. Such as the cercariae of the blood fluke actively penetrate the skin of a swimming man and the infective Ascaris eggs are swallowed by man. ١٣ ١٤ 15- Alternation of generation: In life cycles of some parasites, there are the regular alternations of sexual and asexual reproductions, this phenomenon is called alternation of generation. Such as the life cycle of Plasmodium vivax (the causative organism of malaria). 16- Mechanical transmission: Arthropods play a role of the transportation of pathogens, which is not indispensable for the disease transmission. Such as flies carry typhoid bacilli, ascarid eggs and amoebic cysts. 7
17- Biological transmission: Pathogens have to spend a part of their life cycle in the vector arthropods in which they multiply or develop into the infective stage and then invade the human body under the help of the arthropod. Such as Anopheles mosquitoes transmit malaria. ١٥ Endoparasite Evolution of Parasitism Free Living Ectoparasite Commensalism Temporary parasite Symbiosis Mutualism Permanent parasite Obligatory parasite Parasitism Facultative parasite Accidental parasite Opportunistic parasite Parasite Host Carrier Patient Final host Intermediate host Reservoir host Paratenic host ١٦ Zoonosis Larva migrans 8
Parasites Harms to Man 1. Mechanical effects of parasites on host tissues and organs: e. g., biliary ascariasis and larva migrans. 2. Depriving nourishment from hosts: e.g. hookworms suck blood. 3. Toxic effect: e. g., mosquitoes, spiders and ticks introduce venom when they insert their mouth parts into the skin. 4. Immuno-pathological lesion. e.g. schistosoma liver cirrhosis; when hydatid fluid is released from the rupture of a hydatid cyst anaphylaxis often results. ١٧ Human Immunity against Parasites Its intensity and specificity are usually at a lower level than those produced by bacteria and viruses. It refers to Non-sterilizing immunity (Premunition( Concomitant immunity). Resistance to infection by the same or closely related pathogen established after an acute infection has become chronic, and lasting as long as the infecting organisms are in the body. The host may be protected from superinfection as long as the parasites remain in the body. This situation is known as premunition.. This may be of great importance in endemic areas in limiting the severity of infection with Plasmodium, Schistosome, hookworms and other parasites. ١٨ 9
Adaptations to Parasitism 1- Morphologic adaptations Absence of locomotor organelles (eg. Protozoa). A digestive tract, is reduced (e.g. Trematodes) or is absent (e.g. Cestodes). The reproductive system is very highly developed (e.g. trematodes and cestodes). Specialized attachment organs (e.g. flatworms). ١٩ Adaptations to Parasitism 2- Biochemical changes. 3- Develop specialized mechanisms for effecting entrance into the body or tissue. 4- Successfully overcome the immune response of the host. Locate in relatively protected sites. Changes in the parasite surface antigenic structure. Modify the host immune response by products of parasite metabolism. 5- Increase reproductive capacity. ٢٠ 10
(WHO) - Priority Diseases 1. Schistosomiasis Schistosomiasis, also known as bilharziasis or snail fever,, is a primarily tropical parasitic disease caused by the larvae of one or more of five types of flatworms or blood flukes known as schistosomes. The name bilharziasis comes from Theodor Bilharz, a German pathologist, who identified the worms in 1851. ٢١ 2. Malaria (WHO) - Priority Diseases Malaria is a serious infectious disease spread by certain mosquitoes. It is most common in tropical climates. It is characterized by recurrent symptoms of chills, fever, and an enlarged spleen. The disease can be treated with medication, but it often recurs. Malaria is endemic (occurs frequently in a particular locality) in many third world countries. ٢٢ 11
3. Filariasis (WHO) - Priority Diseases Filiariasis is the name for a group of tropical diseases caused by various thread-like parasitic round worms (nematodes) and their larvae. The larvae transmit the disease to humans through a mosquito bite. Filariasis is characterized by fever,, chills, headache, and skin lesions in the early stages and, if untreated, can progress to include gross enlargement of the limbs and genitalia in a condition called elephantiasis. ٢٣ (WHO) - Priority Diseases 4. Trypanosomiasis An infection by an organism of the Trypanosoma genus. Kinds of trypanosomiasis are African trypanosomiasis and Chagas' disease.. Also called trypanosomal infection. 5. Leishmaniasis Leishmaniasis refers to several different illnesses caused by infection with an organism called a protozoan. ٢٤ 12
(WHO) - Priority Diseases 6. Leprosy Leprosy is a slowly progressing bacterial infection that affects the skin, peripheral nerves in the hands and feet, and mucous membranes of the nose, throat, and eyes. Destruction of the nerve endings causes the affected areas to lose sensation. Occasionally, because of the loss l of feeling, the fingers and toes become mutilated and fall off, causing the deformities that are typically associated with the disease. Leprosy is replaced by HIV/AIDS Human Immunodeficiency Virus / Acquired Immune Deficiency Syndrome me. ٢٥ Why were they selected? 1- Schistosomiasis 200,000,000 infected 500,000-1,000,000 deaths/year 2- Malaria 500,000,000 infected 2,500,000 deaths/year 3- Filariasis 250,000,000 infected 4- Trypanosomiasis 25,000,000 infected 65,000 deaths/year 5- Leishmaniasis 1,200,000 infected 6- Leprosy 1,300,000 infected Approximately 25% of world's population infected by one of these. ٢٦ 13
General Characteristics The list of those diseases are: 1. Chronic diseases 2. With no effective vaccine 3. With no practical chemotherapy 4. Affect young 5. Affect underprivileged (poor peoples) 6. Vector-borne borne Other parasites include: Hookworm 1.3 billion infected Amebiasis Infected, 1% world population Annual deaths, 40,000 to 110,000 Ascariasis 1.3 billion infected Annual deaths (intestinal obstruction), 1550 ٢٧ Presence of Diseases in a Population (Prevalence) Factors required: 1. Source could be: Infected persons Carriers Animals 2. Mode of transmission may be: Direct Indirect Vectors-born 3. Susceptible host Immunity ٢٨ 14
How to control parasitic diseases? Control: ٢٩ Mouth Contact 3 Vector Infection Stool, Urine, Bronchial, Secretion or Vector Stage in man Stage left man Stage Infective in environment 1 (vector) 2 stage 1- Destruction of source of infection 2- Interruption of transmission 3- Protection of susceptible population Diagnosis Pathogenicity Treatment & Diagnosis Epidemiology Transmission 2 Important Groups of Human Parasites Protozoa Amoebae Flagellates Sporidium Ciliates Helminthes Nematodes Trematodes Cestodes Arthropoda Mosquitos Flies Ticks Mites Bugs Fleas Lice ٣٠ 15
PROTOZOA Protozoa can be classified into 3 types according to degree of pathogenicity: 1. Pathogenic. 2. Non-pathogenic (commensals). 3. Whose pathogenicity are debatable (doubtful). Protozoa can be classified into 4 types according to organs for locomotion: 1. Amoebae pseudopodia 2. Flagellates flagella 3. Ciliates cilia 4. Sporozoa absence of locomototion. Entamoeba histolytica Giardia intestinalis, A flagellate Balantidium, Ciliophora ٣١ PROTOZOA LUMINAL PROTOZOA - It colonize the luminal organs i.e. intestinal tract and the urogenital tract. - It have two stages: 1. Trophozoite (vegetative / invasive stage) 2. Cyst (infective stage) Entamoeba histolytica The causative organism for: Amoebiasis, Amoebic dysentery and Amoebic liver abscess. Life cycle It inhabits the large intestine. The cyst is the infective stage. On ingestion excyst into amoebulae trophozoites which is the vegetative stage invade the mucosa to absorb nourishment from tissues dissolved by its cytolytic enzymes and also ingest RBCs (Red Blood Corpuscles). Trophozoites of E. histolytica with ingested erythrocytes ٣٢ 16
Entamoeba histolytica ٣٣ Pathology Primary lesion is ULCER - invasion of the wall of large intestine Complications appendicitis, stricture, intestinal perforation. Secondary lesions occur as a result of presence of trophozoites in extraintestinal organs especially liver Hepatic amoebiasis; pulmonary amebiasis; cerebral ameobiasis; cutaneous amebiasis; spleenic abscess. Symptoms Diarrhea; dysentery stool containing blood, mucous and shreds of necrotic mucosa, acute abdominal pain, and fever. Chronic ameobiasis recurrent attacks of dysentery. HEPATOMEGALY; and weight loss. ٣٤ Ulcer of large intestine Amoebic ulceration Amebic liver abscess 17
Causal Agent for giardiasis Giardia intestinalis Giardia intestinalis is a protozoan flagellate Life Cycle: Cysts are resistant forms and are responsible for transmission of giardiasis. Both cysts and trophozoites can be found in the feces (diagnostic stages). The cysts are hardy and can survive several months in cold water. Infection occurs by the ingestion of cysts in contaminated water, food, or by the fecal-oral route. In the small intestine, excystation releases trophozoites (each cyst produces two trophozoites). Trophozoites multiply by longitudinal binary fission, remaining in the lumen of the proximal small intestine where they can be free or attached to the mucosa by a ventral sucking disk. Encystation occurs as the parasites transit toward the colon. The cyst is the stage found most commonly in nondiarrheal feces. Because the cysts are infectious when passed in the stool or shortly afterward, person-to-person transmission is possible. While animals are infected with Giardia, their importance as a reservoir is unclear. ٣٥ Giardia intestinalis ٣٦ 18
Giardia intestinalis Disease: Chronic diarrhea. Signs and symptoms may vary and can last for 1 to 2 weeks or longer. In some cases, people infected with Giardia have no symptoms. Acute symptoms include: ٣٧ Diarrhea Gas Greasy stools that tend to float Stomach or abdominal cramps Upset stomach or nausea/vomiting Dehydration (loss of fluids) Weight loss and failure to absorb fat, lactose, vitamin A and vitamin B12. In children, severe giardiasis might delay physical and mental growth, slow development, and cause malnutrition. Balantidium coli Balantidium coli, a large ciliated protozoan parasite. Balantidium coli, is an intestinal protozoan parasite that can infect humans. These parasites can be transmitted through the fecal-oral route by contaminated food and water. Causes diarrhea, abdominal pain, and sometimes a perforated colon. Balantidium coli infection can be prevented by following good hygiene practices. Wash all fruits and vegetables with clean water when preparing or eating them, even if they have a removable skin. ٣٨ Balantidium coli, cyst Balantidium coli, trophozoite 19
Balantidium coli Life Cycle: Cysts are the parasite stage responsible for transmission of balantidiasis. The host most often acquires the cyst through ingestion of contaminated food or water. Following ingestion, excystation occurs in the small intestine, and the trophozoites colonize the large intestine. The trophozoites reside in the lumen of the large intestine of humans and animals, where they replicate by binary fission, during which conjugation may occur. Trophozoites undergo encystation to produce infective cysts. Some trophozoites invade the wall of the colon and multiply. Mature cysts are passed with feces. ٣٩ Balantidium coli ٤٠ 20
Malaria Malaria Parasites Malaria parasites are micro-organisms that belong to the genus Plasmodium. There are more than 100 species of Plasmodium, which can infect many animal species such as reptiles, birds, and various mammals. Four species of Plasmodium have long been recognized to infect humans in nature. Malaria is a mosquito-borne disease caused by a parasite. People with malaria often experience fever, chills, and flu-like illness. Left untreated, they may develop severe complications and die. In 2008, an estimated 190-311 million cases of malaria occurred worldwide and 708,000-1,003,000 people died. ٤١ Malaria Biology The natural ecology of malaria involves malaria parasites infecting successively two types of hosts: humans and female Anopheles mosquitoes. In humans, the parasites grow and multiply first in the liver cells and then in the red cells of the blood. In the blood, successive broods of parasites grow inside the red cells and destroy them, releasing daughter parasites ("merozoites") that continue the cycle by invading other red cells. The blood stage parasites are those that cause the symptoms of malaria. When certain forms of blood stage parasites ("gametocytes") are picked up by a female Anopheles mosquito during a blood meal, they start another, different cycle of growth and multiplication in the mosquito. After 10-18 days, the parasites are found (as "sporozoites") in the mosquito's salivary glands. When the Anopheles mosquito takes a blood meal on another human, the sporozoites are injected with the mosquito's saliva and start another human infection. Thus the mosquito carries the disease from one human to another (acting as a "vector"). ٤٢ 21
Malaria ٤٣ CONTROL AND PREVENTION OF INTESTINAL INFECTIONS WITH PROTOZOA In general, the prevention of intestinal protozoa infections is largely a problem of sanitation and hygiene. Infections can be reduced or even eliminated in a community by: (1) sanitary disposal of fecal wastes; (2) the protection of susceptible individuals, (3) treatment of infected individuals; (4) wash hands and vegetables; (5) Screened toilets from flies, cockroaches (mechanical vectors) ٤٤ 22
١ Schistosomiasis Schistosomiasis, also known as bilharzia, is a disease caused by parasitic worms, Schistosoma. More than 200 million people are infected worldwide. In terms of impact this disease is second only to malaria as the most devastating parasitic disease. The parasites that cause schistosomiasis live in certain types of freshwater snails. The infectious form of the parasite, known as cercariae, emerge from the snail, hence contaminating water. You can become infected when your skin comes in contact with contaminated freshwater. Most human infections are caused by Schistosoma mansoni, S. haematobium, or S. japonicum. Biology Causal Agents: Schistosomiasis is caused by digenetic blood trematodes. The three main species infecting humans are Schistosoma haematobium, S. japonicum, and S. mansoni. Two other species, more localized geographically, are S. mekongi and S. intercalatum. In addition, other species of schistosomes, which parasitize birds and mammals, can cause cercarial dermatitis in humans. ٤٦ 23
Life Cycle: Eggs are eliminated with feces or urine. Under optimal conditions the eggs hatch and release miracidia, which swim and penetrate specific snail intermediate hosts. The stages in the snail include 2 generations of sporocysts and the production of cercariae. Upon release from the snail, the infective cercariae swim, penetrate the skin of the human host. It migrates through several tissues and residence in the veins. Adult worms in humans reside in the mesenteric venules in various locations, which at times seem to be specific for each species. S. haematobium most often occurs in the venous plexus of bladder, but it can also be found in the rectal venules. The females (size 7 to 20 mm; males slightly smaller) deposit eggs in the small venules of the portal and perivesical systems. The eggs are moved progressively toward the lumen of the intestine (S. mansoni and S. japonicum) and of the bladder and ureters (S. haematobium), and are eliminated with feces or urine, respectively. Human contact with water is thus necessary for infection by schistosomes. Various animals, such as dogs, cats, rodents, pigs, hourse and goats, serve as reservoirs for S. japonicum, and dogs for S. mekongi. ٤٧ ٤٨ 24
Intermediate hosts Biomphalaria sp., the intermediate host for S. mansoni. Right: Bulinus sp., the intermediate host for S. haematobium ٤٩ phylum Platyhelminthes Classification: Class: Trematoda 1. Fasciola hepatica The Liver Fluke ٥٠ Leaf- like worm Live in in bile ducts of cattle, sheep and goats 25
Life Cycle ٥١ General Structure phylum Platyhelminthes Classification: Class: Cestoda Taenia (Tapeworm) ٥٣ 26
Head Neck Immature proglottis Mature proglottis ٥٥ Gravid proglottis ٥٧ 27