Clinical Parasitology - 01 Intro to Parasitology

CLINICAL PARASITOLOGY INTRODUCTION TO PARASITOLOGY • PARASITOLOGY • • • • • • Parasitology o Study of parasites ▪ Parasitic protozoa ▪ Helminths ▪ Arthropods o Parasites - organisms that live on and obtain nutrients from other organisms (host) o Host - organisms that harbors the parasite o Focused on ▪ Morphology ▪ Life cycle ▪ Relationship w/ host & environment Types o Ectoparasites - Live on the outer surface of the host o Endoparasites o Live within the host ▪ Obligate (dependent on their hosts) ▪ Facultative ▪ Accidental Life Cycle o Simple life cycle ▪ One host ▪ All developmental stages are completed in 1 host o Two hosts required ▪ Definite Host – harbors the parasite; reproduces sexually ▪ Intermediate Host – harbors the larval stage/asexual forms • Few parasites require two intermediate hosts Transmission Routes o Oral route/ skin or mucous membrane penetration/ Inoculation (by arthropod vectors)/ Sexual Contact Clinical Features o May vary o Some are acute, MOST are chronic Diagnosis o Uses clinical diagnosis o Uses laboratory diagnosis ▪ Documentation of characteristic forms of parasites in feces, urine, sputum, body secretion, blood ▪ E.g. Serological Tests • TYPES OF PARASITES • • • • • • PARASITOLOGY • Host-Parasite Relationship o Symbiosis - the association of two different organisms 1. Mutualism - both organisms benefit from each other 2. Commensalism - one organism benefits while the other is unharmed 3. Parasitism - one organism benefits; other is harmed • • TYPES OF HOST • • • Host - organism that harbors the parasite Definitive Host o Final host o harbors the sexual/adult stage of the parasite o Mosquito - harbor Plasmodium spp. (Malaria) Intermediate Host o harbors the asexual/larval stage of the parasite o Man - harbor Plasmodium spp. (Malaria) Reservoir o harbors the parasite and serve as an important source of nutrients for parasite to continue its life cycle. o also serve as additional source of infection for the susceptible host o Example: ▪ Pigs - Balantidium coli ▪ Dogs - Echinococcus granulosus Paratenic host o host the parasite but no development happening o only serve as carrier or transport host o Example: ▪ Freshwater prawns - Angiostrongylus cantonensis ▪ Freshwater fishes - Gnathostoma spinigerum ▪ Big suitable fishes - Plerocercoid larva of Diphyllobothrium latum • • Endoparasites o Parasites that live inside the host o Infection - when parasite live inside the host o Entamoeba histolytica - amoebiasis Ectoparasites o Parasites that live outside the body of the host o Infestation - when parasite lives outside the host o Sarcoptes scabiei - scabies Erratic - parasites that invades a part of the body where it is not usually found. o Entamoeba histolytica - usually found in the intestine, can also be found in liver (extraintestinal amoebiasis) o Ascaris lumbricoides - usually in intestine, can also be found in the lungs, heart Pathogenic - capable of eliciting disease o Plasmodium spp. - Malaria o Entamoeba histolytica - Amoebiasis o Trichomonas vaginalis - Trichomoniasis Non-pathogenic o Not capable of producing disease o Also called commensals o Endolimax nana o Entamoeba coli o Trichomonas tenax Facultative - parasites that are capable of living independently (with or without a host) o Strongyloides stercoralis o Naegleria fowleri o Acanthamoeba castellani Obligatory - parasites that cannot live without a host o Example: Ascaris lubricoides Intermittent - parasites that only visit the host during feeding time o Anopheles, Aedes, Culex spp. - mosquito o Phlebotomus spp - sandfly o Glossina spp - tsetse fly Incidental - parasites that infects unusual host. o Echinococcus granulosus - usually infect dogs, can also infect humans Zoonotic - animal parasites that are also capable of infecting human o Ancylostoma caninum - aka dog hookworm o Ancylostoma braziliense - aka cat hookworm • • • • • • • • • Aberrant - infects host where they cannot develop further o Toxocara spp. - usually infect animals; can also infect human but do not develop Permanent - parasites that are found within the host from early life until maturity o Wuchereria bancrofti - Elephantiasis Transitory - parasites wherein the larval stage develops inside the host but the adult is free-living o Strongyloides stercoralis - egg/larval stage in man, adult stage independent Periodic - parasite wherein the larval stage develops in a host different from that of the adult o Schistosoma japonicum - larval stage in mollusks (snails); adult stage develop in human Cytozoic - parasites that are found intracellularly o Toxoplasma gondii, Leishmania tropica, Cryptosporidium parvum Hematozoic - parasites that are found inside red blood cells o Plasmodium spp., Babesia microti Enterozoic - parasites that are found in the intestines o Ascaris lumbricoides, Entamoeba histolytica Coelozoic - parasites found in the body cavities o Mansonella perstans, Mansonella ozzardi Pseudoparasites - non-living things mistaken as parasites in the laboratory o Pollen grains - mistaken as helminth/worm egg o Plant hairs - mistaken as helminth larva o o o o o o o SOURCES OF INFECTION • • • MODE OF TRANSMISSION • • • • • • • Ingestion o Food-borne parasites ▪ Taenia solium - in pork ▪ Taenia saginata - in beef ▪ Trichinella spiralis - in pigs, rats Oral contact o Transmitted through kissing, etc. o Entamoeba gingivalis - cause pyuric alevolaris o Trichomonas tenax - cause pyuric alevolaris Transplacental o Transmitted from mother to fetus o Toxoplasma gondii o Plasmodium spp. o Trypanosoma cruzi Sexual o Transmitted sexually o Trichomonas vaginalis - most common o Annilingus - mouth to anus contact; among homosexuals ▪ Entamoeba histolytica ▪ Giarda lamblia ▪ Enterobius vermicularis Skin Penetration o Include vector-borne parasites o Hookworms o Strongiloides stercoralis Blood Transfusion o Transmitted through blood o Plasmodium spp o Babesia spp o Trypanosoma spp o Leishmania spp Autoinfection o self-infection; infection to oneself External autoinfection - can be acquired from contaminated hands ▪ Enterobius vermicularis - adult female lay egg on anal area causing pruritus (excessive itching) Reverse peristalsis - parasite travel back to body Enterobius vermicularis Strongyloides stercoralis Hymenolepis nana Taenia solium Cryptosporidium parvum • • Man o Anthroponoses - transmission between 2 humans o Usually sexually-transmitted parasites ▪ Trichomonal vaginalis,etc. Animals o Zoonoses - transmission from animal to man o Echinococcus granulosus - in dogs o Toxoplasma gondii - in cats o Trematodes - group of parasites that are primarily found in snails Raw/Uncooked Meat o Food-transmitted parasites o Transmitted through oral ingestion o Taenia solium - in pork o Taenia saginata - in beef o Trichinella spiralis - in pigs, rats o Toxoplasma gondii - in cats o Fasciola fasciolopsis - in crabs o Paragonimus westermani - in crabs o Echinostoma ilocanum - in snails o Heterophyes - in fishes o Opistorchis felineus - in fishes o Clonorchis sinensis - in fishes Contaminated Soil and Water o Soil-transmitted parasites - from contaminated soil ▪ Helminths ▪ Hookworms ▪ Ascaris lumbricoides ▪ Trichuris trichiura ▪ Strongyloides stercoralis Vector o Arthropods - insects o Transmit infection from one organism to another o Biologic vector ▪ Transmits the parasite only after it completed its development within the vector ▪ Mosquito (Anopheles spp.) • Vector for Plasmodium spp. o Mechanical vector ▪ Also called Phoretic vector ▪ Transport parasite only ▪ Cockroach (Periplaneta americana) - Ascaris lumbricoides, Trichuris trichiura ▪ Fly - Ascaris lumbricoides, Trichuris trichiura PATHOGENESIS OF PARASITIC INFECTION • Mechanical Damage o Eggs – large parasitic egg may be deposited in organs or tissues which may cause irritation ▪ Trematodes - large parasitic egg ▪ Schistosoma japonicum - in intestinal mucosa • • • • • • • ▪ Schistosoma hematobium - in urinary bladder ▪ Paragonimus westermani - in lungs ▪ Fasciola hepatica - in liver o Larva – migratory helminths may cause trauma ▪ Ascaris lumbricoides - from intestine to lungs, capable of heart to lung migration ▪ Strongyloides stercoralis - from intestine to lungs, capable of heart to lung migration ▪ Hookworms - from intestine to lungs, capable of heart to lung migration ▪ ASH o Adult – may cause trauma of intestinal wall ▪ Hookworms ▪ Ascris lumbricoides ▪ Strongyloides stercoralis ▪ Taenia spp ▪ Trichuris trichiura Space-Occupying Lesion o Some parasites may produce cysts that may compress surrounding tissues/organ. o Echinococcus granulosus - cause hydatid cyst o Taenia solium - cause neurocysticercosis Inflammatory Reaction: o Cause inflammation o Entamoeba histolytica - elicit inflammation of the large intestine causing granuloma o Wuchereria bancrofti - cause blockage & chronic inflammation of lymphatics (esp. in lower extremities) o Trematode eggs - inflammation around the surroundings of egg deposition; large compared to other parasitic eggs Enzyme Production & Lytic Necrosis o Plasmodium spp., Leishmania spp., Trypanosoma produces enzymes that cause digestion and necrosis of host cells o Entamoeba histolytica - produce cysteine proteinase (hydrolytic enzyme); can cause tissue destruction leading to lytic necrosis Toxins o Minimalistic significance o Clinically significant in bacterial infection o Entamoeba histolytica Allergic Reaction o Parasite that induce allergies o Schistosomes - cause cercarial dermaitis o Hydatid cyst (Echinococcus granulosus) - may rupture that can cause anaphylactic reaction (anaphylaxis) ▪ Anaphylaxis - severe form of allergy o Occult filariasis - hidden; can cause tropical pulmonary eosinophilia ▪ Eosinophil - increase in allergic reaction ▪ Eosinophilia - increase in eosinophils Neoplasia o Cancerous o Schistosoma haematobium - can cause bladder carcinoma o Clonorchis spp, Opistorchis spp. - can cause cholangiosarcoma Secondary Bacterial Infection o Seen in some helminthic infections o Schistosoma spp o Strongyloides stercoralis LIFE CYCLE OF PARASITES • • • • Infective stage - the stage in the life cycle of parasite that is capable of eliciting disease. Diagnostic stage o the stage in the life cycle of parasite that can be detected in the laboratory o the stage wherein the parasite can be identified o parasites are unique compared to other Direct Life Cycle o aka Simple Life Cycle o Involves only one host Entamoeba histolytica Indirect Life Cycle o aka Complex life cycle o Involves 2 or more host to complete its life cycle Paragonimus Westermani o Host # 1 - Man o Host # 2 - snails PARASITE TAXONOMY • Kingdom Animalia o Subkingdom Metazoa ▪ Phylum Nemahelminthes • Class Adenophorea o Order Trichurida ▪ Trichuris trichiura ▪ Trichinella spiralis ▪ Capllaria philippinensis • Class Rhabditea o Subclass Secernentia ▪ Order Ascaridida, • Ascaris lumbricoides • Toxocara canis • Toxocara cati • Anisakis spp. ▪ Order Oxyurida • Enterobius vermicularis ▪ Order Strongylida • Necator americanus • Ancylostoma duodenale • Ancylostoma braziliense • Ancylostoma caninum • Angiostrongylus cantonensis • Angiostrongylus costaricensis ▪ Order Rhabditida • Strongyloides stercoralis ▪ Order Spirurida • Wuchereria bancrofti • Brugia malayo • Loa loa • Onchocerca volvulus • Mansonella ozzardi • Mansonella perstans • Mansonella streptocerca • Dirofilaria immitis • Drancunculus medinensis ▪ Phylum Platyhelminthes • Class Cestoidea o Subclass Cestoda ▪ Order Pseudophyllidea • Diphyllobothrium latum ▪ Order Cyclophyllidea • Taenia solium • Taenia saginata • Hymenolepsis nan • Hymenolepsis diminuta • Dipylidium caninum • Echinococcis granulosis • Class Trematoda o Subclass Digenea ▪ Order Plagiochiformes • Paragonimus westermani ▪ Order Echinostomatifermes • Fasciola hepatica • Fasciolopsis busko • Fasciola gigantica • Echinostoma ilocanum ▪ Order Opistorchiformes • Chlonorchis sinensis • Opistorchis felineus ▪ • • Opistorchis viverrine • Heterophyes heterophyes • Metagonimus yokogawai Order Strigeiformes • Schistosoma japonicum • Schistosoma mansoni • Schistosoma haematobium • Schistosoma mekongi • Schistosoma intercalatum Kingdom Protista o Subkingdom Protozoa ▪ Phylum Sarcomastigophora • Subphylum Sarcodina o Class Lobosea ▪ Order Amoebida • Entamoeba histolytica • Entamoeba coli • Entamoeba nana • Iodamoeba butschii • Entamoeba gingivalis • Entamoeba dispar • Entamoeba hartmanni • Entamoeba polecki • Acanthamoeba spp. ▪ Order Schizopyrenida • Naegleria spp. • Subphylum Mastigophora o Class Zoomastigophora ▪ Order Trichomonadida • Trichomonas vaginalis • Trichomonas tenax • Trichomonas hominis • Dientamoeba fragilis ▪ Order Diplomonadida • Giardia lamblia ▪ Order Retortomonadida • Retortamonas intestinalis • Chilomastix mesnili ▪ Order Enteromonadida • Enteromonas hominis ▪ Order Kinetoplastida • Leishmania donovani • Leishmania tropica • Leishmania braziliensis • Trypanosoma cruzi • Trypanosoma brucei gambiense • Trypanosomabrucei rhodesiense ▪ Phylum Ciliophora • Class Ciliatea o Order Trichostomatida ▪ Balantidium coli ▪ Phylum Apicomplexa • Class Sporozea o Subclass Coccidia ▪ Suborder Haemosporina • Plasmodium falciparum • Plasmodium malariae • Plasmodium vivax • Plasmodium ovale • Plasmodium knowlesi ▪ ▪ Suborder Eimeriina • Toxoplasma gondii • Cryptosporidium parvum • Cyclospora cayetanensis • Sarcocystis • Cytoisospora belli o Subclass Piroplasmia ▪ Order Piroplasmidora • Babesia microti Phylum Microspora • Encephalitazoon intestinalis • Enterocytozoon bieneusi