INTRODUCTION TO MEDICAL PARASITOLOGY

Learning outcomes By the end of this section, you should be able to: Define Parasitology. Mention kinds of parasitism. Mention kinds of hosts. Classify human parasites. Mention transmission of parasitic infection Mention Host – Parasite relationship Define infection, infestation, incubation period, and Convalescence Classify Medical Protozoalogy Define and Classify medical Helminthology.

MEDICAL PARASITOLOGY The science that deals with parasites that live in or on other organisms called their hosts and causing injury to them. A parasite may be: Endo-parasite which lives inside the host (parasitic infection). Ecto-parasite which lives on the surface of the host (parasitic infestation).

General Types of Parasites A. Obligatory parasite: One that is entirely dependent upon a host for its survival. B. Facultative parasite: Free-living organisms, but can become parasitic upon another organism C. Accidental parasites: The parasite infect unsuitable host, so cannot complete its life cycle

KINDS OF HOST Definitive host: A host in which the adult stages of the parasite develop (It is the host in which sexual reproduction takes place) Intermediate host: A temporary host for the parasite, in which the immature stage of the parasite develop (It is the host in which asexual reproduction takes place). Reservoir host: An animal host which can be infected with the parasite and act as a source for human infection

Vector: An arthropod, that serves as an intermediate host as well as transmitting a pathogen from host to host. Accidental hosts: These are hosts in which the parasite cannot successfully develop, but can still cause disease

Transmission of parasitic infection 1- Mouth: most common: Ingestion of infective stage, e.g. protozoan cysts & embryonated nematode eggs. Intimate oral kissing, e.g. Entamoeba gingivalis. 2- Skin penetration of infective larval stage to skin Directly: e.g. Cercaria of Schistosoma & filariform larva of hookworm. Indirectly (through insect vectors), e.g. infective stage of trypanosome 3- Airborne. Parasite inhaled  nose  nasopharynx  intestine, e.g. E. vermicularis. Parasite inhaled  nose  blood or lymphatic  specific tissues, e.g. T. Gondii & free living amoeba. 4- Transplacental: Parasite from mother to foetus

Host – Parasite Relationship Commensalism: 2 animals of different species live together without metabolically dependent on the other, although one organism may receive some benefit but does not harm the other. Mutualism: Where shared benefits are present; one cannot survive in the absence of the other

Parasitism: where an organism living in or on another living organism, causing some degree of damage to its host

DISEASE TERMINOLOGY Infection: Term applied to invasion of the body by pathogenic organisms and the reaction of the body to their presence and to the toxins . Infestation: Some parasites do not multiply within the host and this situation is at times referred to as infestation.

Incubation period: The incubation period is the time between infection and the development of symptoms and signs of disease. Convalescence: Convalescence is the period of healing and describes a phase in which balance is regained and damage repaired.

Life cycle of parasites Study of life cycle of parasites is following up the pathway of its development, starting by one stage ending to where the cycle repeats. Hosts Habitat Infective stage Mode of infection Diagnostic stage

Hosts: Definitive – Intermediate – Reservoir Habitat: The organ inside the definitive host where adult stages of the parasite live Infective Stage: The stage of the cycle that infect man Mode of Infection: Ingestion Injection Inhalation Penetration of skin Bite of insect Organ transplantation Blood transfusion Congenital Diagnostic Stage: The stage from the cycle which can be seen under microscopy or by naked eye

Diagnosis Clinical Diagnosis Clinical Picture – Symptoms - Signs Laboratory Diagnosis - Direct Methods: Demonstration of the diagnostic parasitic stage, in urine or stool or blood or sputum, under microscopy - Indirect Methods: *Detection of Antibodies (Abs) by serological tests [IHAT- IFAT-ELISA] *Detection of Antigens (Ags) Imaging Methods X-Ray – Ultrasonography – Ct Scan - MRI

MEDICAL PARASITOLOGY 1- Medical Helminthology. 2- Medical Protozoology. 3- Medical Entomology

Human Parasites 1- Unicellular Parasites (Protozoa). Parasites infect human fall into 2 categories: 1- Unicellular Parasites (Protozoa). 2- Multicellular Parasites (Metazoa). Flat worms. Round worms. Ticks. Mites. Insects.

Each Parasite is classified into: Phylum الشعبة Class الطائفة Order الرتبة Family العائلة Genus الطبقة Species الصنف

Classification of human parasitic protozoa kingdom: Protozoa 1- Phylum: Rhizopoda Entamoeba 2- Phylum: Ciliophora Balantidium 3- Phylum: Euglenozoa (Mastigophora or Flagellates) Trypanosoma Leishmania 4- Phylum: Apicomplexa (Sporozoa) Toxoplasma Plasmodium

MEDICAL HELMINTHOLOGY Helminths are a general term meaning worms. This part deals with the study of helminths that parasitize man.

CLASSIFICATION of MEDICAL HELMINTHOLOGY I-Platyhelminthes (Flatworms): They include; Trematoda (Flukes):. Cestoda (Tapeworms) II) Nemathelminthes (Nematoda) (Roundworms): The medically important worms have separate sexes.