First Year Biology Parasitology PDF

/ First year Biology Dentistry Dep Parasitology Introduction: □ Medical parasitology deals with the parasites, which cause human infections and the disease...

/ First year Biology Dentistry Dep Parasitology Introduction: □ Medical parasitology deals with the parasites, which cause human infections and the diseases they produce. □ Here, we study host/parasite relationship, geographical distribution, habitat, morphology, lifecycle, mode of infection, disease manifestations, treatment. □ It is divided into 2 parts: Protozoology Helminthology Parasite r Protozoa Helminths (multicellular) Kingdom-Protista Kingdom-Animalia \ I 1 si&m i***- 1 I Cili?tes- , 1 X-. T ' EalamdebaC: dG Isrdia ' Plasmdium Balantidium ™chomms g Cesfedes y. l &Trematodes T 1 T -Ancylostoma Ascaris Tannin Fasciola Echinococcus Schistosoma Parasites: □ Parasites are living organisms, which depend on a living host for their nourishment and survival. They multiply or undergo development in the host. CamScannerÿ  Biology Dentistry Dep First year (unicellular □ The term 'parasite' is usually applied to Protozoa organisms) andTTelniinthes (multicellular organisms). Parasites can also be classified as: 1. Ectoparasite: Ectoparasites inhabit only the body surface of the host ""without penetrating the tissue. Lice, ticks, and mites are examples of ectoparasites. The term infestation is often employed for parasitization with ectoparasites. 2. Endoparasite: A parasite, which lives within the body of the host and Ts said to cause an infection is called an endoparasite. Most of the protozoan and helminthic parasites causing human disease are endoparasites. 3. Free-living parasite: It refers to non-parasitic stages of active existence, which live independent of the host. Endoparasites can further be classified as: VT 1. Obligate parasite: The parasite, which cannot exist without a host. 2. Facultative parasite: Organism which may either live as parasitic V" form or as free-living form. / ?3. Accidental parasites: Parasites which infect an unusual host are ___ known as accidental parasites. 4. Aberrant parasites: Parasites, which infect a host where they cannot develop further, are known as aberrant or wandering parasites. Host is defined as an organism, which harbors the parasite and provides nourishment and is relatively larger than the parasite. The host may be of the following-types:- -- - 1. Definitive host: The host in which the adult parasite lives and undergoes sexual reproduction is called the definitive host. The definitive host may be a human or any other living being. However, in majority of human parasitic infections, man is the definitive host. 2. Intermediate host: The host in which the larval stage of the parasite lives or asexual multiplication takes place is called the intermediate host. In some parasites, 2 different intermediate hosts CamScanner-; First year Biology Dentistry Dep may be required to complete different larval stages. These are known as first and second intermediate hosts, respectively. 3ÿ Paratenic host: A host in which larval stage of the parasite remains v'able without further development is referred as a paratenic host. Such host transmits the infection to another host, include freshwater shrimp, flatworms, and frogs. A Reservoir host: In an endemic area, a parasitic infection is continuously kept up by the presence of a host, which harbors the parasite and acts as an important source of infection to other susceptible hosts. 5ÿ Accidental host: The host, in which the parasite is not usually found. Host-parasite Relationships 1. Symbiosis: Both host and parasite are dependent upon each other, none of them suffers any harm from the association. 2. Commensalism: Only the parasite derives benefit from the association without causing any injury to the host, a commensal is capable of living an independent life also. 3. Parasitism: The parasite derives benefits and the host is always harmed due to the association, the parasite cannot live an independent life. Life cycle of Parasites: Direct life cycle: When a parasite requires onlv(6mglehost) to complete its development, it is called as direct life cycle. > Indirect life cycle: When a parasite requires(2 or morelpecies* of host to complete its development, the life cycle is called as indirect life cycle. * ~ Sources of infection: 1. Contaminated soil 2. Contaminated water 3. Contaminated Food 4. Animals (cow, pig, dog, cat) CamScanner-; First year Biology Dentistry Dep 5. Insect vectors: A vector is an agent usually an arthropod that transmits an infection from man to man or from other animals to man. Vectors can be: Biological vectors: The term biological vector refers to a vector, which not only assists in the transfer of parasites but the parasites undergo development or multiplication in their body as well. They are also called as true vectors. Mechanical vectors: The term mechanical vector refers to a vector, which assists in the transfer of parasitic form between hosts but is not essential in the life cycle of the parasite. 6. Persons, which may be carriers of the parasite or patients, e.g., all anthroponotic infections, vertical transmission of congenital infections. 7. Self (autoinfection) > Finger-to-mouth transmission, e.g. pinworm > Internal reinfection. Modes of Infection: 1. Oral transmission: The most common method of transmission is through oral route by contaminated food, water, soiled fingers, or fomites. Many intestinal parasites enter the body in this manner, the infective stages being cysts, embrvonated eggs, or larval forms. 2. Skin transmission: Entry through skin is another important mode of transmission. _3. Vector transmission: Many parasitic diseases are transmitted by insect bite. A vector could be a biological vector or a mechanical vector. 4. Direct transmission: Parasitic infection may be transmitted by person-to-person contact in some cases. 5. Vertical transmission: Mother to fetus transmission may take place in malaria and toxoplasmosis. 6. Iatrogenic transmission: It is seen in case of transfusion malaria and toxoplasmosis after organ transplantation. CamScanner-; First year Biology Dentistry Dep Pathogenesis: Parasitic infections may remain unapparent or give rise to clinical disease. A tew organisms, such as E. histolytica may live as surface commensals, without invading the tissue. Clinical infection produced by parasite may take many forms acute, subacute, chronic, latent, or recurrent. > Pathogenic mechanisms, which can occur in parasitic infections are: 1. Lytic necrosis: Enzymes produced by some parasite can cause lytic necrosis. 2. Trauma: Attachment of hookworms on jejunal mucosa leads to traumatic damage of villi and bleeding at the site of attachment. 3. Allergic manifestations: Clinical illness may be caused by host immune response to parasitic infection. 4. Physical obstruction: Masses of roundworm causes intestinal obstruction. 5. Inflammatory reaction: Clinical illness may be caused by inflammatory changes and consequent fibrosis. 6. Neoplasia: A few parasitic infections have been shown to lead to malignancy CamScanner-j *>>***) I