Introduction to Parasitology

• Welcome to Parasitology

Parasitology

• It is the study of parasites

Parasites

• Eukaryotes
• Humans are usually secondary in incidental hosts
• Lack cell walls
• Majority of parasitic infections are indirect transmission

Pathogenesis

• Process by which disease begins or develops

Pathogenesis: Steps

• Entry of Causative Agent
• Replication
• Cell and tissue damage
• Immune escape

Pathogenesis: Escape mechanisms

• Invasion of immune-privileged tissues like CNS or eyes.
• Some parasites lay eggs in the adipose tissues
• "Invisibility" through shielding surface components after opsonization.
• Change surface identity as T-cells and antibodies of the host's immune system recognize specific epitopes
• Production of molecules that are able to modulate or block certain steps in the host's immune response.
• Parasite can go inactive to escape the immune system (quiescence).

Diagnosis

• Definitive & Serologic/Antibody testing

Definitive

• Microscopic identification using samples like stool, urine, or blood
• Larvae, egg, or adult forms are identified to determine causative agent

Serologic or Antibody testing

• Uses blood tests and kits for different antibodies
• Presence of antibodies determines causative agent
• Both Definitive & Serologic/Antibody testing are equally useful for detecting and confirming causative agents

Kinds of Parasites

• Endoparasites and Ectoparasites

Endoparasites

• More common for humans and lives inside the body

Ectoparasites

• More common for animals and lives outside the body

Protozoa

• Two general forms are Cysts and Trophozoites

Classification according to locomotion

• Protozoa are classified to locomotion and have several pathogens and their diseases

Prevention

• Includes effective sanitation, thorough cooking, and elimination of vectors

RTS, S (Mosquirix)

• First-ever malaria vaccine, created by GlaxoSmithKline, but unapproved by the FDA
• Involves three primers within a year and a booster after 15-18 months
• Offers partial protection for 5 months to 2 years

Cysts

• Egg-shaped, spherical
• In a dormant, inactive state
• Infective state
• Survives outside the host

Trophozoites

• Adult form that are oval and pointed from the anterior end
• Absorbs nutrients from the host
• Non-infective state but disease-causing
• Survives inside the host

Classification according to locomotion

• Rhizopoda, Mastigophora, Sporozoa, Cilliates

Rhizopoda

• Uses Pseudopodia "false feet"
• Example = Entamoeba histolytica

Mastigophora

• Uses Flagella
• Examples = Giardia lamblia (old), Giardia intestinalis (new), Trichomonas vaginalis & Leishmania spp.

Sporozoa

• Does not use locomotion; it just moves with the circulation
• Examples = Plasmodium spp., Cryptosporidium parvum/homini, Toxoplasma gondii & Trypanosoma spp.

Cilliates

• Uses Cillia
• Example = Balantidium coli

Intestinal Diseases

• Amoebiasis, Cryptosporidiosis & Giardiasis
• includes causative agents, route of transmission, symptoms and manifestations, diagnosis and Treatments

Amoebiasis

• Causative agent: Entamoeba histolytica
• Called the "handmaiden of war"
• Causes bloody diarrhea, amoebic dysentery
• May spread to other tissues if left untreated, especially the liver
• Includes bloody diarrhea due to inverted-flask shaped lesions in intestines
• Route of Transmission: Fecal-oral portal of exit and entry
• Detection of cysts in the stool done via fecalysis or stool analysis

Treatment: Types

• Tissue amebicides: Kill CA in the bowels or liver (Ex. Chloroquine, emetine)
• Luminal: Kills CA in the bowels ONLY (Ex. Diloxanide (asymptomatic cases), paromomycin, iodoquinol)
• Mixed: Kills CA in both lumen and liver (Ex. Metronidazole (DOC))

Amoebiasis: Treatment based on severity

• Asymptomatic: Diloxanide
• Mild to moderate: Metronidazole + Luminal agent
• Severe: Metronidazole (alternative: Tinidazole)
• Hepatic abscess: Metronidazole/Tinidazole + luminal agent

Cryptosporidiosis

• Causative agent: Cryptosporidium parvum
• Very hard to kill, does not die in chlorine
• Transient in healthy hosts (self-limiting) and severe in immunocompromised hosts
• Infects the small intestines
• Leading cause of diarrhea in children under two

Cryptosporidiosis: Route of Transmission

• Through undercooked meat and contaminated drinking water (FECAL - ORAL)
• Symptom: Watery Diarrhea
• Diagnosis: Color change of oocysts in stools in acid-fast diagnosis and Dots in biopsy

Cryptosporidiosis: Treatment

• Nitazoxanide (DOC), Paromomycin & Azithromycin

Giardiasis

• Causative agent: Giardia lamblia (old) or Giardia intestinalis (new)
• Most commonly identified intestinal parasite globally
• More common in children than adults
• Common hosts are beavers
• One of the major diarrheal diseases
• Symptoms: Fatty, foul-smelling diarrhea, Weight loss & Explosive, watery diarrhea
• Route of Transmission: Infected beaver's feces contaminate water, and if a human drinks it = infection
• Diagnosis: Pear-shaped with bilobed nuclei under the microscope
• Diagnosis: "Old man's eyeglasses", has Falling leaf motility, "Smiling" CA and cysts in stools

Giardiasis: Treatment

• Metronidazole (DOC) Alternatives: Tinidazole, Nitazoxanide & Paromomycin, used if the patient is pregnant

Urogenital disease

• Trichomoniasis disease to tackle

Trichomoniasis

• Causative agent: Trichomonas vaginalis
• STD infection, can be passed vertically
• Progression of disease is faster if the patient's genital pH is higher than normal (neutral to alkaline)
• "Ping pong disease" due to how fast it transmits
• Symptoms: Itching around the genitals, Urethritis & Colpitis macularis, which causes "strawberry cervix" and frothy discharge
• Diagnosis: Methylene blue on vaginal discharge to indicate trophozoites presence & Corkscrew motility under the microscope
• Treatment: Metronidazole (DOC)

Blood and Tissue Diseases

• Leishmaniasis, Malaria, Toxoplasmosis & Trypanosomiasis (includes Causative agents, Route of transmission, Symptoms and manifestations, Diagnosis & Treatments)

Leishmaniasis

• Causative agent: Leishmania spp.
• Route of Transmission: From female sand fly (Phlebotomus for old world) & Lutzomyia (new world)
• Consists of 2 forms: Amastigote (no flagella) & Promastigote (with flagella)

Leishmaniasis: Variants

• L.tropica, L.brazilensis & L.donovani

L.tropica

• "Oriental sore"
• Cutaneous leishmaniasis

L.brazilensis

• "Espundia"
• Mucocutaneous leishmaniasis that Attacks the mucous membranes
• Highly disfiguring

L.donovani

• Cala-azar "black fever" disease
• Visceral leishmaniasis
• Darkening of skin, enlargement of liver
• Most severe form of leishmaniasis

Leishmaniasis: Diagnosis

• L.tropica: Amastigotes in the skin lesions
• L.brazilensis: Amastigotes in mucous membrane lesions
• L.donovani: Amastigotes in spleen, liver, bone marrow and fluid will reveal trophozoites in Giemsa-stained tissues Treatment (Sodium stibogluconate (DOC); Pentamidine (ALT); Paromomycin; Miltefosin & Amphotericin)

Malaria

• Hosts: arthropods (Female Anopheles mosquito) and Vertebrates (humans)
• Asexual based reproduction (Schizogony), creates schizonts; which is the infective part of the disease
• Sexual based reproduction (Gametogony and sporogony).
• Mosquito = Can be both a vector and a host

Malaria: Life Cycle

• Infected mosquito bites human
• Injects sporozoites, which migrate to liver and infects hepatocytes
• Matures into merozoites (collectively; schizonts) that rupture and releases schizonts into the bloodstream
• Merozoites infect the RBCs, and evolves into a trophozoite, which multiplies and forms new merozoites to spread to bloodstream.
• Some new merozoites becomes gametocytes and are picked up by mosquitos where the sexual phase of the malaria life cycle occurs and it forms sporozoites.
• Gametocytes (male and female) are picked up by a female, uninfected mosquito to form a zygote, then into an oocyte which contains infective sporozoites to travel to the mosquito's salivary glands.

Malaria: Causative agents

• P. falciparum, P. vivax, P.ovale, P.malariae & P.knowlesci

P. falciparum

• Malignant tertian malaria
• "Blackwater fever"
• Periodicity: 48hrs
• Cerebral malaria; most severe neurological complication
• 48hrs between paroxysms, attacks old and new RBCs
• Features: Crescent-shaped gametocytes

P.vivax & P.ovale

• Benign tertian malaria) and (Ovale tertian malaria)
• Periodicity: 48hrs
• Causes relapse due to hypnozoites which stays in the liver
• 48hrs between paroxysms
• Features: P. Vivax; Enlarge RBCs, Lemon cyst, Schauffer dots

P.malariae: Malaria

• Benign quartan malaria
• Periodicity: 72hrs
• Causes recrudescence
• Attacks old RBCs
• Maurer's cleft

P.knowlesci: Malaria

• Quotidian malaria
• Periodicity: 24hrs
• Attacks old RBCs
• Causes severe malaria in Southeast Asia

Malaria: Route of Transmission:

• From female Anopheles mosquito
• Diagnosis done via blood smear
• Treatment for P.falciparum use Artemether + Lumefantrine
• Treatment for P. vivax and P.ovale use Chloroquine (Aralen®) then Primaquine
• Treatment for P.knowlesi and P.malariae is Chloroquine

Toxoplasmosis

• Causative agent: Toxoplasma gondii
• Hosts: Cats are the primary hosts
• Transmission: Ingestion of raw meat, Contact with cat feces, Vertical transmission and Blood transfusion
• Consists of 2 trophozoites: Tachyzoites (highly invasive and smaller) & Bradyzoites (Not very invasive and Larger)

Toxoplasmosis: Symptoms and complications

• Mononucleosis-like symptoms (swollen lymph nodes, fever, fatigue, headaches)
• Immunocompromised people have fatal encephalitis and ringlike lesions & Chorioretinitis
• Diagnosis done via Serologic test reveals rising IgM levels

Toxoplasmosis: Treatment

• Pyrimethamine + Sulfadiazine (Daraprim) DOC, Pyrimethamine + Clindamycin & TMP + SMX (Co-Trimoxazole)

Trypanosomiasis

• Route of transmission & causative agent depends on the species
• 2 general species: Trypanosoma cruzi & Trypanosoma brucei

General Information

• Amastigotes & Trypomastigotes are only two forms
• Trypanosoma cruzi = Triatoma reduviid bug/kissing bug is the 2 Vector
• Trypanosoma brucei = Tsetse fly is the 2nd Vector
• Symptoms, treatment pathways, and other information will depend on the species

Trypanosomiasis: Disease

• T.cruizi = Chagas disease/American trypanosomiasis
• T.brucei = African sleeping sickness

Trypanosomiasis: Distinct markers

• T.cruizi = Romania's sign
• T.brucei = Trypanosomal chancre

Trypanosomiasis: Complications

• T.cruzi has Heart failure/ death
• T.brucei has CNS complications/ death

Trypanosomiasis: Markers

• T.gambiense: winterbottom's sign (posterior triangle cervical lymphadenopahty) and causes West African sleeping sickness
• T.rhodesiense: aremore likely to result in endocrine abnormalities thyroid dysfunction, adrenal insufficiency) and cardiac problems and causes East African sleeping sicknesses

Trypanosomiasis: Treatment

• Benzidazole (DOC) and Nifurtimox for Chagas disease
• African sleeping sickness has two stages: early and late pentamidine or Eflornithine

Metazoan/Helminths

• Multicellular worms
• Bilaterally symmetrical
• Complex life cycles that includes multiple forms and hosts unlike parasitic protozoans
• Do not have digestive systems
• Hard to develop vaccine

Helminths (parts of the helminth)

• head
• neck
• proglottid

Helminths: Classifications

• Phylum: Nemahelminthes (Class: Nematodes)
• Phylum: Platyhelminthes (Class: Cestodes & Class: Trematodes)

Nematodes/Roundworms

• "thread-like"
• Unsegmented bodies ("tube with a tube")
• Most numerous multicellular animals on Earth and posses external cuticle
• Reservoir: Environment (soil)
• Definitive hosts: Humans

Class Nematode

• Consists of Intestinal and Blood & Tissue Diseases

Intestinal Diseases (Class Nematode)

• Causative agents ( A.lumbricoides, T.trichuria, E.vermicularis, C. philippinesis, A.duodenale / N. americanus, and S. stercoralis)
• Diagnosis and Symptoms
• transmission occurs through routes
• Treatment is available

Ascariasis

• caused by Ascaris lumbricoides (Giant intestinal roundworm)
• second most prevalent multicellular parasite (E. vermicularis is first), infects lungs (Loeffler's syndrome), GIT obstructions and enterocolitis
• Route of Infection occurs in site (Lungs, intestines, and appendix)
• mamiliated eggs and curved tail diagnosis
• Treatment includes albendazole, pyrantel pomoate, piperazine, steroids (corticosteroids) and surgery if severe

Trichuriasis/Whipworm Disease

• Causative agent :Trichuris trichuria (Whipworm): Intestines
• Diagnosis involves detection of Eggs
• Route of transmission occurrs when one ingests the eggs
• Albendazolole is treatment and supplementation that combats iron depletion

Enterobiasis/Oxyuriasis

• Caused by Enterobius vermicularis (Pinworm / Seatworm) affects children
• causes perianal nocturnal itching
• Treatment involves albendazolde, family treated if someone is positive

Necatoriasis/Ancylostomiasis

• Hookworm also know as Old-World Necator americanus and New World ancylostoma duodenale (Soil transmitted helminths)
• Diagnosis = Eggs in feces of a D shaped Eggs in feces or sputum
• Symptoms = fatigue (often)
• Transmission = Direct Skin Penetration
• Treatment (Albendazole ) and iron supplements will alleviate symptoms

Ancylostomiasis Hookworm

• Necator and Ancylostoma, route is direct skin pentration
• Symptoms
• Diagnosis:eggs (feces)
• Route of transmission = Skin
• Treatments: DOC: albendazole or Thiabendazole

Strongyloidiasis

• Threadworm or angullata and soil transmitted helmiths: Humans, dogs, and non human primates can contract parasite and paradoxical asthma
• Treatents: Best Serologic test is ivesmectin

Blood and Tissue diseases

Causative agents A.parastic B.spirals C.vovulous

Filarisis or Elephantasis

• Transmitted vis Vectored in Culex, aedes, and mansonia bites for lymphatic obstruction
• Tested via provocation and treated with with Dicrthyk arbamazine DOC

Trichinosis ,Trichinellosis

• Caused by Agent Trichinella spiralis,
• Transmitted by ingestion of encysted larvae and the pork must be cooked
• Gastro symptoms, mysositis,,periorbital edema are all symptoms
• Treated with Albendazole ,with steroid augmentation of Swelling and muscle Biopsy Visulous. Larvae as diagnostic method

Onchoceriasis River blindness

• Onchocercia Volvus causative and cause visiousl damage
• Femake Similium and black flies cause skin infection
• Treatment Is via Ivermectin
• Leopard rash, visiousl damage and skin itch are all symptoms

Loiasis

• Loa loa warms
• Chysopo Flies cause the spread of bites
• Calibar swelling and visual observation are symptoms
• Diagnosd by detection in blodd and tissue
• DEC and abendazoles all help

Dracunculiasis Guinea Norm disease

• Transmission Occurs thru Drinking of infected copepods, blisters and ulcers happen
• slow remo of nor,, albendazoke can he applied

Class Trematode

• unsystematized Flat and Leiflike as host
• Transmitted Via snail to get from
• primary host to Humans
• Secondary will also infect fish /aquatic veggies

Schitosomiasis

• Symptoms via secondary or water borne or direct contact
• Schotosoma agent and all species have some effect,
• -Blood Flukes : Schitosoma also
• Eggs and fever, liver or Cirrhosis, treatment, route, diagnosis, all require attention
• Also named in Schosomiasis or Bihalziarsis

Facioliasis

• Causative Agents F hepatica
• Causes Hepatoxicity
• Water crustacean/fish snails transmit
• Symptoms: Pain that gets really bad

Trematod

• Clonorchiasis agent via Fish eaten raw
• Eggs/Biopsy as Diagnsotioc and Prawiquantel as Treatment
• Intestional
• faluciolopiasis

Fasciclopasis or Giant Intestinal Fluke

• Transmited by ingestions of infected crustacean
• symptions: abdominal

Lung Flue as part of Termatod

• P and Western are the Agengs via Crustacean that transmits it
• Symptoms: are TB esque

Paragonimiasis

• Transmited via Crusteatce / Ingestion via shellfish
• P and Westermanni are most commo agents and can infect water
• Also can give TB Symp
• Prawiquantel, Eggs and fever, all are affected by it

Cestodes Parts and Description

• Stobila,scotex
• Proglttids

Taeniasis

• Saginata is beef / Soulm si swin
• Transmited vis ingsrtion of beef,pork .and test eggs
• Praziuanterl or Surfery

Diphiobothriasis

D. Latums caused by eating rae fish (tapewarm) that is broad

• Trnasmissiib and treated via praZis

Encochilosis

• dog taped are, via Ingestion of uncooked beef /catles
• Hagadtic Disease is common result and can create cysts

Hymenolepis Nanda

• Dwars Tape warm causes transssmissin via ingestion and can be contracted during transmission Symptoms:usually asymptompatic with some Diag and Prowiquan