Introduction to Parasitology

Welcome to Parasitology

• Parasitology is the study of parasites.

Parasites Overview

• Most microorganisms are prokaryotes, especially bacteria.
• Parasites are eukaryotes.
• Humans are usually secondary or incidental hosts.
• Most parasitic infections are indirect transmission.
• Parasites are more complex vs bacteria and viruses.
• Parasites do not have cell walls compared to other eukaryotes.

Pathogenesis

• Pathogenesis is the process by which a disease begins and develops.
• The steps in pathogenesis are:
  • Causative agent entry
  • Replication
  • Cell and tissue damage
  • Immune escape
• Parasites escape mechanisms include:
  • Invading immune-privileged tissues like the CNS or eyes
  • Laying eggs in adipose tissues, not patrolled by the immune system
  • Shielding surface components after opsonization to achieve "invisibility"
  • Changing surface identity to evade T-cells and antibodies
  • Producing molecules to modulate or block the host's immune response
  • Going inactive (quiescence)

Diagnosis

• Definitive diagnosis involves microscopic identification.
• Samples for microscopic identification can be from stool, urine, blood, or depends on the portal of exit.
• Identification of larvae, eggs, or adult forms determines the causative agent.
• Serologic or antibody testing involves blood tests.
• "Kits" are used for detecting different antibodies.
• The presence of antibodies determines the causative agent.
• Both methods are useful for detecting and confirming causative agents.

Prevention of parasitic infestation and infections.

• Effective sanitation
• Thorough Cooking
• Elimination of vectors

RTS, S (Mosquirix)

• It was the first ever malaria vaccine although it was unapproved by the FDA
• Created by GlaxoSmithKline (GSK)
• It had 3 primers that was taken within 1 year and one booster shot after 15-18 months.
• It offered partial protection (5 months to 2 years)

Kinds of parasites

• Endoparasites: More common for Humans
  • Live on the inside the body
  • Ex: Helminths and Protozoans
• Ectoparasites: More common for animals
  • Live on the outside body
  • Ex: Lice, ticks, and mites

General forms of protozoa

• Cysts
  • Egg-shaped, spherical
  • Dormant, inactive state
  • Infective state
  • Survive outside the host
• Trophozoites
  • Adult form, oval, pointed from the anterior end
  • Absorbs nutrients from the host
  • Non-infective, but disease-causing
  • Survive inside the host

Classification according to locomotion

Intestinal Diseases

• Diseases to tackle
  • Amoebiasis
  • Cryptosporidiosis
  • Giardiasis
• including
  • Causative agents
  • Route of transmission
  • Signs and symptoms
  • Diagnosis
  • Treatments

Amoebiasis

• Causative agent: Entamoeba histolytica
• Called the "handmaiden of war."
• Causes bloody diarrhea/amoebic dysentery
• May spread to other tissues, especially the liver, if left untreated.
• Symptoms: Diarrhea with blood and pus due to inverted flask-shaped lesions in the intestines
• Route of Transmission: Fecal-oral transmission
• Diagnosis: Fecalysis or stool analysis to observe cysts in the stool
• Treatment:
  • Tissue amebicides kill causative agents in the bowels or liver, e.g., chloroquine, emetine.
  • Luminal agents kill causative agents in the bowels only, e.g., diloxanide (asymptomatic cases), paromomycin, iodoquinol.
  • Mixed agents kill causative agents in both lumen and liver, e.g., metronidazole (DOC)
• Asymptomatic: Diloxanide
• Mild to moderate: Metronidazole + Luminal agent
• Severe: Metronidazole, (alternative: Tinidazole)
• Hepatic abscess: Metronidazole/Tinidazole + luminal agent

Cryptosporidiosis

• Causative agent: Cryptosporidium parvum
• Extremely hard to kill, does not die in chlorine
• Transient in healthy hosts (self-limiting)
• Severe in immunocompromised hosts
• Infects the small intestines
• Leading cause of diarrhea in children under 2
• Route of Transmission: Through undercooked meat and contaminated drinking water (fecal-oral)
• Symptoms: Watery diarrhea
• Diagnosis:
  • Color change of oocysts in stools in acid-fast diagnosis
  • Dots in biopsy
• 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 (beaver fever)
• One of the major diarrheal diseases
• Symptoms: Fatty, foul-smelling diarrhea; weight loss; explosive, watery diarrhea
• Route of Transmission: Infected beber's feces contaminate water, and if a human drinks that water they are infected
• Diagnosis:
  • Pear-shaped with bilobed nuclei under the microscope.
  • Old man's eyeglasses, falling leaf motility
  • "Smiling" causative agent, cysts in stools.
• Treatment:
  • Metronidazole (DOC)
  • Alternatives: Tinidazole, nitazoxanide, paromomycin.

Urogenital Disease Topic

• Diseases to tackle
  • Trichomoniasis

Trichomoniasis

• Causative agent: Trichomonas vaginalis
• STD infection which can be transmitted vertically.
• Progression of the disease is faster if the patient's genital pH is higher than normal (neutral to alkaline).
• Transmits easily (Ping pong disease)
• Symptoms: Itching, urethritis, strawberry cervix, frothy discharge
• Routes of Transmission
  • Vertical transmission
  • Direct sexual contact
• Diagnosis: Methylene blue on vaginal discharge to indicate trophozoites presence.
• Treatment: Metronidazole (DOC)

Blood and Tissue Diseases to tackle

• Leishmaniasis
• Malaria
• Toxoplasmosis
• Trypanosomiasis
• Causative agents
• Route of transmission
• Signs and symptoms
• Diagnosis
• Treatments

Leishmaniasis

• Causative Agent: Leishmania
• Two Forms: Amastigote (no flagella) and Promastigote (flagella)
• Variants: Leishmania braziliensis, Leishmania tropica, and Leishmania donovani
• Symptoms
  • L. tropica - "Oriental Sore", Cutaneous leishmaniasis
  • L. braziliensis - “Espundia”, Mucocutaneous leishmaniasis attacks mucous membranes, highly disfiguring
  • L. donovani - "Black Fever", Visceral form is darkening of skin with enlargement of liver and most severe form
• Route of Transmission: From female sand fly, Phlebotomus (old world; Africa, Asia, Europe); Lutzomyia (new world; North and South America)
• Diagnosis:
  • L.tropica: Amastigotes in the skin lesions
  • L.braziliensis: Amastigotes in mucous membrane lesions
  • L.donovani: Amastigotes in spleen, liver, bone marrow. Giemsa-stained tissues and fluid will reveal trophozoites
• Treatment: Sodium stibogluconate (DOC), Pentamidine (ALT), Paromomycin, Miltefosin, and Amphotericin

Malaria

• Hosts
  • Arthropods (Female Anopheles mosquitoes)
  • Humans are vertebrates
• Arthropods can both a vector and a host. They create schizonts, which is the infective part of the disease.
• There's sexual-based reproduction (Gametogony and sporogony)
• Life Cycle
  • An infected mosquito bites a human; injects sporozoites.
  • Sporozoites migrate to liver and infect hepatocytes, mature to merozoites collectively, which are schizonts that rupture and release into the bloodstream
  • Merozoites infect RBCs and evolve into trophozoites. The trophozoites in the RBCs multiplies and vorms new merozoites, causing burst RBCs with more merozoites into the bloodstream forming gametocytes. -Female, uninfected mosquitoes pick up these gametocytes forming a zygote, then an oocyte with infective sporozoites that will ultimately travel to mosquito’s salivary glands.
• Causative agents
  • P. falciparum: Malignant tertian malaria, "Blackwater fever", Periodicity: 48hrs, can cause cerebral malaria & 48hrs between paroxysms, attacks old and new RBCs with Crescent-shaped gametocytes
  • P. vivax (Benign tertian malaria) and P. ovale (Ovale tertian malaria): Periodicity: 48hrs, both causes relapse because of hypnozoites which stays in the liver, 48hrs between paroxysms, P. Vivax enlarges RBCs & has Lemon cyst with Schauffer dots
  • P. malariae: Benign quartan malaria, Periodicity: 72hrs, causes recrudescence and attacks old RBCs, Maurer's cleft
  • P. knowlesci: Quotidian malaria, Periodicity: 24hrs, attacks old RBCs and causes severe malaria in Southeast Asia
• Diagnosis (blood smear): Crescent-shaped gametocytes in the blood or ringlike formation of trophozoites
• Route of Transmission: From female Anopheles mosquito

Toxoplasmosis

• Causative agent: Toxoplasma gondii
• Two types of trophozoites are tachyzoites (highly invasive & smaller) and bradyzoites (not very invasive & larger).
• Cats are the primary hosts.
• Humans can acquire it through ingestion of raw meat, contact with cat feces, vertical transmission, or blood transfusion.
• Symptoms: Mononucleosis-like symptoms and for the immunocompromised may have fatal encephalitis and chorioretinitis
• Diagnosis: Serologic test reveals rising IgM levels
• Treatment: Pyrimethamine + Sulfadiazine (Daraprim), Pyrimethamine + Clindamycin, or TMP + SMX (Co-Trimoxazole)

Trypanosomiasis

• Hosts, route of transmission, causative agents, symptoms, diagnosis, and treatments included.

• Causative agent: Trypanosoma spp.

  • Two species: Trypanosoma cruzi and Trypanosoma brucei
  • Trypanosoma cruzi is transmitted by the Triatoma reduviid bug (kissing bug)
  • Trypanosoma brucei is transmitted by the Tsetse fly
  • Symptoms, treatment pathways, and other information depend on the species

• Trypanosomiasis

  • T. cruzi: Chagas disease/American trypanosomiasis causes a distinct sign, Romania's sign, that can result in conditions like heart failure and or even death
  • T. brucei: African sleeping sickness causes a winter bottom's sign (posterior triangle cervical lymphadenopathy) through the complications in the CNS

• T.gambiense: Causes West African sleeping sickness

• T.rhodesiense: Causes East African sleeping sickness which most likely lead thyroid dysfunction, adre adrenal insufficiency and cardiac problems

• Trypanosomiasis

  • T. cruzi displays in stages
    • In the acute stage: there is fever, fatigue, rash, diarrhea and Romania's sign
    • In the chronic stage: muscles and organ enlargement
    • In the reservoir stage: Cats, dogs, armadillos are signs of poverty

• Trypanosomiasis

  • T.brucei displays in stages
    • 1st Phase: fever, headaches, joint pains
    • 2nd Phase: confusion, mental disturbances

• Diagnosis: Trypomastigotes in blood films or CSF or serologic testing shows high IgM levels

• T. cruzi: Benznidazole (DOC) and Nifurtimox

• T.brucei: African sleeping sickness treated depending on species

  • West African (Gambiense)
    • Pentamidine (DOC if early)
    • IV Eflornithine (DOC if late)
    • Melarsoprol (2nd line tx)
  • East African (Rhodiense)
    • Suramin (DOC)
    • Melarsoprol (DOC if late)

Metazoa/Helminths

• Involves: general forms of metazoa, classifications, diagnosis, diseases, and treatments

Helminths

• "Metazoan parasites", "worms", "helminthic parasites"
• Multicellular worms bilaterally symmetrical
• Complex life cycles, multiple hosts and forms
• Most helminths have no digestive systems. Vaccines are difficult to develop
  • Head
  • Neck
  • Proglottid
• Classifications of Helminths
  • Phylum Nemahelminthes; Class Nematodes
  • Phylum Platyhelminthes; Class Cestodes and Class Trematodes

Nematodes/Roundworms

• Bodies are Unsegmented
• Described as a "tube within a tube"
• Possess an external cuticle which is shed periodically
• Most numerous multicellular animals on Earth
• Resevoir: Environment - mostly soil, Definitive host: Humans
• Class Nematode
  • Description
  • Cause Intestinal Diseases
  • Cause Blood and Tissues
  • Diagnosis
  • Treatments
• Cause Intestinal Diseases :
  • Causative Agent-
    • A.lumbricoides
    • T.trichuria
    • E.vermicularis
    • C. philippinesis
    • A.duodenale / N. americanus
    • S. stercoralis
    • Diagnosis
    • Symptoms
    • Direct contact
    • Treatments

Ascariasis

• Causative agent: Ascaris lumbricoides (Giant Intestinal Roundworm)
• Second to most prevalent multicellular parasite; major sites: Lungs, intestines, and appendix
• Signs and Symptoms: Lungs may show Loeffler's syndrome, GIT problems, Obstruction, enterocolitis
• Diagnosis: Eggs in feces can be viewed through the Kato Katz Technique and look to be mamiliated

Ascariasis

• Route of transmission: Ingestion of Infective eggs needing to be on the ground
• Treatment
  • Albendazole (DOC)
  • Pyrantel pamoate (Combantrin )Piperazine
  • Surgery (severe cases) and Supportive therapy (corticosteroids)

Trichuriasis/Whipworm disease

• Causative agent: Trichuris trichuria
• Major site: Intestine, where patients are usually asymptomatic
• Increase in peristalsis or clubbing of nails, can lead to appendicitis
• Diagnosis: Look for eggs in feces, eggs are barrel-shaped
• Routes of transmission is the same with Ascaris
• Treatment option is the use of Antibiotics

Enterobiasis/Oxyuriasis

• Causative Agent - Enterobius vermicularis a.k.a Pinworm/Seatworm
• Normally affects children
• Where female pinworms lay eggs around the anal region and if one family member is affected , the entire group should be treated
• Patients normally display nocturnal perianal itching, restlessness and Pseudo Appendicitis/enterocolitis

Transmission: Ingestion / Inhalation of eggs

• Diagnosis:
• Graham scotch tape test, eggs appear as D shaped Treatment:
• Pyrantel pamoate Albendazol Mebendazol

Hookworms

• Causative agent: Necator americanus/Ancylostoma duodenale
  • A.K.A New World/Old World hookwork
  • Direct penetration so is a Direct contact based transmission

Transmission and Symptoms :

-Direct skin Penetration Anemia due to the Iron Deficiecy and progress to microcytic and hypochromic

• Treatment: to use Albendazole and give Iron suppliments

Ancylostomiasis: Cutaneous Larva Migrans

• Causative agent: Ancylostoma brazilensis/Ancylostoma caninum (Cat Hookworm Cat Hookworm)

  • Direct based Transmission

  • Patients usually have cutaneus and pruritis type symptoms

• To diagnose this- one perform a fecis and to observe any larva , give anthelmintics for Tx : Albendazole or - Thiabendazole

Strongyloidiasis

• Agent = strong loides stercolaris
• Direct Host such as Human and Dogs
• Sx normally include dermatitis a localized rash or asthma with percutaneous entry
• Best Dx would be a serologic test to check the best out come

Filarasis

• This would includes various diseases such with that such as
  • T- Spiralis
  • T.Zoe Volulus

Filariasis/Lymphatic filariasis

• Wuchereria bancrofti
• Causative: agent Anopheles Culex
• Bruglya Transmission -Agent Aedes Mansonia

Symptoms: Symptoms Normally Cause Lympatic obstuction

Treatment: DEC is given and Microfilarle are normally present

Trichinosis/Trichinellosis

• This would include Involves Sprialia Direct ingestion of pork, Muscle round worms , biopsy will show larvae

Onchoceriasis Transmission

• Black flies, usually have nodules. In the body cause skin issues skin such as leopard type rashes

Loiasis

-Is Bites given by mangos that display swelling Treatments:DEC normally work

Dracunculiasis

• Is Causes symptoms which show most of the time, by water and infected copepods. Usually from worm infections that can be extracted and treated.
• Is a infection that is done through the water systems. Where worm is extracted usually after

Class trematode

• Causes Flukes

Blood flukes

• is Schistosomaispp trematode Treatment: that includes praziquantel . Transmisison by percutanous . Can have various Symptoms

Schisomiasis

• caused by S . Hematobium is a spine, that affects bladder and the Urogenital tract while The S.Jopani is from a japponum is contracted from per cuteness in the liver with intestine symptoms

Liver flukes

-This Can cause by Hepatica that happens when eggs and feces and biopsy and the treatemnts include albendazol

Fasciolopsiasis :

is a Fluke where transmission from Water Chests where treatments Prazuantal such as Pigs.

Clonorchiasis

Treatements : eggs that comes out and if can is usually asymtpatic. If there is a severe, one looks for more obstrucitons