parasitology part 1 - Details

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Area of biology concerned with the phenomenon of dependence of one living organism on another

Parasitology

Seen in case of transfusion malaria and toxoplasmosis after organ transplantation

IATROGENIC TRANSMISSION

Wet mount preparation of lymph node aspirate and chancre fluid are used as rapid methods for demonstration of trypanosomes. o Biopsies from liver, spleen, bone marrow, and lymph nodes are taken in visceral leishmaniasis for demonstration of Leishman Donovan (LD) bodies. o All biopsy tissues must be submitted to the laboratory without the addition of formalin fixative. If there is delay in transport or processing, the specimen should be placed in polyvinyl alcohol fixative o Adult filarial worms can sometimes be found in section of biopsied lymph node. o Corneal scrapings are useful in diagnosis of acanthamoeba keratitis.

SKIN BIOPSY

– deals with the parasites that cause human infections and the diseases they produce; broadly divided into two parts: protozoology and helminthology

Medical Parasitology –

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

SKIN BIOPSY

Living together; the association of two living organisms, each of a different species

SYMBIOSIS

Seen in case of transfusion malaria and toxoplasmosis after organ transplantation

IATROGENIC TRANSMISSION

Seen in case of transfusion malaria and toxoplasmosis after organ transplantation

IATROGENIC TRANSMISSION

Seen in case of transfusion malaria and toxoplasmosis after organ transplantation

IATROGENIC TRANSMISSION

Seen in case of transfusion malaria and toxoplasmosis after organ transplantation

IATROGENIC TRANSMISSION

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

SKIN BIOPSY

Association of two different species of organisms that is beneficial to one and neutral to the other

COMMENSALISM

SKIN BIOPSY

Association of two different species of organisms that is beneficial to both

MUTUALISM

SKIN BIOPSY

Association of two different species of organisms that is beneficial to one at the other’s expense

PARASITISM

SKIN BIOPSY

A parasite, which lives within the body of the host. The presence of an endoparasite causes an: INFECTION Most of the protozoan and helminthic parasites causing human disease are endoparasites.

ENDOPARASITE

SKIN BIOPSY

Inhabit only the body surface of the host without penetrating the tissue. (e.g. head lice, ticks) The presence of an ectoparasite causes an: INFESTATION

ECTOPARASITE

SKIN BIOPSY

Most parasites are obligate parasites; cannot exist without a host. Need a host at some stage of their life cycle to complete their development and to propagate their species Depends entirely upon their host for existence Ex. Toxoplasma gondii, Plasmodium spp.

OBLIGATE

SKIN BIOPSY

May exist in a free-living state or become parasitic when the need arises (e.g. Strongyloides)

FACULTATIVE

SKIN BIOPSY

Infect an unusual host; establishes infection in a host where it does not normally live (e.g. Echinococcus granulosus, Dipylidium caninum, Dirofilaria immitis, Ancylostoma caninum)

ACCIDENTAL/INCIDENTAL

Remain in or on the host for its entire life Ex. Strongyloides, Loa loa, Taenia solium

PERMANENT

Live in the host for a short time (e.g. Plasmodium spp.)

TEMPORARY

Passes digestive tract of humans without infecting them (e.g. Eimeria sardinae)

SPURIOUS

Infect a host where they cannot develop further (e.g. Toxocara canis)

ABERRANT

Female parasite capable of reproducing eggs without being fertilized by a male and whose eggs contain larva that immediately hatches (e.g. Strongyloides

PARTHENOGENETIC

Usually protozoans; able to multiply in fecal matter outside human body

COPROPHILIC

Lives inside red blood cells (e.g. Plasmodia, Babesia, Leishmania)

HEMATOZOIC

Lives inside cells or tissues (e.g. Trichinella spiralis)

CYTOZOIC

Lives in body cavities (Mansonella spp.)

COELOZOIC

Resides in intestines (Tapeworms, Entamoeba histolytica)

ENTEROZOIC

ACCORDING TO PATHOGENECITY, Capable of causing disease

PATHOGENIC

Commensals; incapable of causing disease (e.g. Trichomonas tenax, Entamoeba gingivalis)

NONPATHOGENIC

CLASSIFICATION OF HOSTS Host in which the adult parasite lives and undergoes sexual reproduction May be human or any other living being however in majority of human parasitic infections, humans are the final hosts (e.g. filarial, roundworm, hookworm

DEFINITIVE/FINAL

CLASSIFICATION OF HOSTS, Host in which the larval stage of the parasite lives or the asexual multiplication takes place. If there are more than one IH, these can be classified as 1st and 2nd IH.

INTERMEDIATE

CLASSIFICATION OF HOSTS Parasite does not develop further to latter stages Parasite remains alive and is able to infect other susceptible host Harbors the parasite; will only serve as a transport medium; no further development occurs. Ex. Paragonimus metacercaria in raw wild board meat Diphyllobothrium latum plerocercoid larva in big carnivorous fish

PARATENIC

CLASSIFICATION OF HOSTS Harbors parasite; allows the parasite life cycle to continue and become additional sources of infection Ex. Pigs – reservoir host of Balantidium coli Field Rats – reservoir host of Paragonimus westermani Cats – reservoir host of Brugia malay

RESERVOIR

Host in which the parasite is not usually found (e.g. man in echinococcosis)

ACCIDENTAL

CLASSIFICATION OF VECTORS A vector, which not only assists in the transfer of parasites but the parasites undergo development or multiplication in their body as well; also called as true vectors.

BIOLOGIC

A vector, which assists in the transfer of parasitic form between hosts but is not essential in the life cycle of the parasite. Ex. Housefly – Amebiasis Cockroach - Ascariasis

MECHANICAL/PHORETIC

Harbors pathogen and is asymptomatic

CARRIER

Period between the entry of parasite in the host and subsequent recovery of the form/s of parasite in samples

PRE-PATENT PERIOD/ BIOLOGIC INCUBATION

Period between infection to development of symptoms

CLINICAL INCUBATION PERIOD

Individual becomes infected by his/her own Nematodes: Capillaria philippinensis, Enterobius vermicularis, Strongyloides Cestodes: Taenia solium, Hymenolepis nana Protozoan: Cryptosporidium hominis, Cryptosporidium parvum

AUTOREINFECTION

Already infected individuals are further infected with same species (e.g. Strongyloides)

SUPERINFECTION/HYPERINFECTION

SOURCES OF INFECTION Most common Lack of sanitary toilets and the use of night soil or human excreta as fertilizer allow the eggs to come in contact with the soil and form the development of specific parasites Ex. Hookworm, Ascaris lumbricoides, Trichuris trichiura, Strongyloides stercoralis (HATS)

SOIL

SOURCES OF INFECTION Cysts of amebae or flagellates; cercaria of schistosomes

WATER

SOURCES OF INFECTION Trematodes (Flukes) and Cestodes (Tapeworms)

FOOD

SOURCES OF INFECTION Mosquitoes – Malaria, Filarial worms Triatoma bugs – Trypanosoma cruzi Phlebotomus sandflies – Leishmania spp

ARTHROPODS

SOURCES OF INFECTION Cats – direct sources of Toxoplasma infection Rats – may be infected with Hymenolepis nana

ANIMALS

SOURCES OF INFECTION Asymptomatic carriers of Entamoeba histolytica working as food handlers.

ANOTHER INDIVIDUAL

MODES OF TRANSMISSION, Most common method Cestodes, Trematodes, Intestinal Protozoans are foodborne

ORAL (FECAL-ORAL)

Another important mode of transmission Hookworm and Strongyloides stercoralis enter upon exposure to soil Schistosoma spp. is acquired when cercariae in water penetrate the skin

SKIN PENETRATION

Transmit parasites through their bites Malaria, Filariasis, Leishmaniasis, Trypanosomiasis, Babesiosis

ARTHROPODS

Toxoplasma gondii Trophozoites can cross the placental barrier during pregnancy TRANSMAMMARY INFECTION Ancylostoma and Strongyloides - may be transmitted through mother’s milk

CONGENITAL TRANSMISSION

MODES OF TRANSMISSION, Enterobius vermicularis

INHALATION OF AIRBORNE EGGS

MODES OF TRANSMISSION, Trichomonas vaginalis

SEXUAL INTERCOURSE

Seen in case of transfusion malaria and toxoplasmosis after organ transplantation

IATROGENIC TRANSMISSION

– most commonly submitted sample for examination of parasites The most common procedure performed is the examination of a stool specimen for Ova and Parasites (O&P).

Stool

All-purpose fixative; buffered with sodium phosphate to preserve morphological characteristics - 5% concentration: recommended for protozoan cysts - 10% concentration: recommended for helminth eggs and larvae - When the stool specimen is added to the vial, the final ratio of stool to preservative is 1:3 - Preserved stool can be concentrated using Formalin-Ether/Ethyl Acetate Concentration Technique (FECT/FEACT)

FORMALIN

- Used to preserve fresh stool/fresh fecal specimen in preparation for staining the stool smears - Provides excellent preservation of protozoan trophozoites and cysts - For many years, considered as the “gold standard” - Contains mercuric chloride which is highly toxic to humans

SCHAUDINN’S SOLUTION

- Plastic resin that serves to adhere a stool sample onto a slide - Normally incorporated into the Schaudinn’s solution - Main advantage: preservation of protozoan cyst and trophozoites for permanent staining - Stool preserved in PVA can be concentrated using FECT - Modified PVA: using non-mercuric compounds such as copper sulfate or zinc sulfate (used with trichrome stain) - Disadvantage: use of mercuric chloride

POLYVINYL ALCOHOL (PVA)

- Components both fix and provide stain color - Contains Merthiolate (Thimerosal) and Iodine that act as staining components - Formalin acts as a preservative - Useful for fixation of intestinal protozoans, helminth eggs, and larvae - Disadvantages: Contains mercury compounds (thimerosal) Staining of preserved stools in MIF yields unsatisfactory results or not as good as Schaudinn’s fluid

MERTHIOLATE IODINE-FORMALIN (MIF)

- Advantage: Does not contain mercuric chloride; long shelf-life - Disadvantage: Images are not as sharp after staining as compared with those fixed in PVA or Schaudinn’s solution

SODIUM ACETATEACETIC ACID FORMALIN (SAF)

Both the concentration and permanent stained smear can be prepared - It is also possible to perform fecal immunoassay procedures from some of these vials.

SINGLE-VIAL COLLECTION SYSTEMS

- 2 mg of stool + 1 drop of 0.85% NaCl (NSS) + coverslip - Routine method of stool examination - Can be stained with Nair’s Buffered Methylene Blue (BMB) solution - Micrometry is used to measure cysts and ova (ex. differentiation between cysts of Entamoeba histolytica and E. hartmanni is based entirely on their sizes) - LPO (x100) of entire 22x22 mm coverslip & HPO (x400) of at least 1/3 of the coverslip area of both saline and iodine - OIO (x1000) is not recommended (organism morphology is not clear) - The use of iodine is optional Eggs of helminths are also readily seen. o Rhabditiform larvae of Strongyloides stercoralis are detected in freshly passed stool

DIRECT FECAL SMEAR

50-60 mg of stool is placed over a glass slide; covered with cellophane paper soaked in a mixture of glycerin and malachite green solution - GLYCERIN: clearing solution - MALACHITE GREEN: gives a pale green color minimizing the brightness of the microscopic field - Best examined within 10-20 minutes - Useful in mass stool examination; technique is simple and economical - Very good in detecting eggs with thick shells (e.g. Ascaris and Trichuris) but not eggs with thin shells (e.g. Hookworm) - Not able to detect protozoan cysts and trophozoites

KATO THICK SMEAR

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