Module 4 - Parasites & Viruses

Explain the significance of parasitic diseases in the United States

- they are not very common in the U.S. because there are high levels of sanitation, adequate housing, and temperate climates

- they are more common in low and middle income countries

Groups that are affected by Neglected Tropical Diseases

- those in poverty, politically marginalized, and rural areas

- ignored by funders and pharmaceutical research

Strategies to control and eliminate NTDs

- clean water & sanitation

- vector control

- inexpensive pharmaceuticals & simple surgery

- veterinary control

Stool specimen preservatives and their uses

Formalin - concentration, EIA, acid-fast

PVA - PCR, permanent slide

Microscopic characteristics used to identify parasites

- size & shape

- internal organelles

- color & staining characteristics

- life stage form

Stool specimen preparation

- collect by using clean, wide-mouth container

- unpreserved if viewing motile forms

- preserved by two vial system

- processing --> wet mount (sometimes with iodine), concentration by centrifugation, permanent stained smears

Whole blood parasitic specimen

- use EDTA

- thick smear concentrates parasites

- thin smear allows for species identification

Other parasitic specimens (4)

- cellophane tape prep or pinworm paddle

- fluid specimens (urine & CSF should be concentrated)

- tissues, biopsy, corneal scrapings

- sputum

Entamoeba histolytica

disease -

symptoms -

geographic region -

transmission -

specimen -

pathogenic? -

Protozoa (Amoebae)

disease - amebic colitis, extra-intestinal infections, or asymptomatic

symptoms - mild diarrhea with periods of constipation, abdominal discomfort, abscesses in the liver or brain if serious

geographic region - worldwide

transmission - water contaminated with human feces (fecal-oral)

specimen - stool

pathogenic? - yes

Entamoeba coli

specimen -

pathogenic? -

Protozoa (Amoebae)

specimen - stool

pathogenic? - no

Naegleria fowleri

disease -

symptoms -

geographic region -

transmission -

specimen -

pathogenic? -

Protozoa (Amoebae)

disease - primary amoebic meningoencephalitis

symptoms - CNS infection --> headaches

geographic region - warm fresh water

transmission - force of contaminated water into the nasal cavity

specimen - CSF

pathogenic? - yes

Acanthamoeba sp.

disease -

symptoms -

geographic region -

transmission -

specimen -

pathogenic? -

Protozoa (Amoebae)

disease - granulomatous amebic encephalitis (GAE), amebic keratitis, skin ulcers

symptoms - mental status changes, eye pain

geographic region - worldwide in water sources

specimen - biopsy, CSF

pathogenic? - yes

Giardia duodenalis

disease -

symptoms -

geographic region -

transmission -

specimen -

pathogenic? -

Protozoa (Flagellate)

disease - giardiasis

symptoms - diarrhea, abdominal cramps, nausea

geographic region - worldwide

transmission - ingestion of cysts by contaminated food/water, fecal-oral, sexual contact

specimen - stool

pathogenic? - yes

Trichomonas vaginalis

disease -

symptoms -

transmission -

specimen -

pathogenic? -

Protozoa (Flagellate)

disease - trichomoniasis

symptoms - vaginitis, uretrhitis

transmission - sexually transmitted

specimen - vaginal or urethral fluid, urine sediment

pathogenic? - yes

Trypanosomiasis cruzi

disease -

symptoms -

geographic region -

transmission -

specimen -

pathogenic? -

Protozoa (Flagellate)

disease - Chaga's disease

symptoms - painful red lesions caused by replication of amastigotes

geographic region - Central & South America

transmission - triatomine bug bite

specimen - blood

pathogenic? - yes

Cryptosporidium parvum

disease -

symptoms -

geographic region -

transmission -

specimen -

pathogenic? -

Protozoa (Apicomplexa)

disease - cryptosporidiosis

symptoms - healthy --> self-limiting diarrhea, immunocompromised --> malabsorption & wasting

geographic region - worldwide

transmission - ingestion of water with oocysts

specimen & identification - stool; acid-fast stain, EIA, fluorescent Ab stain

pathogenic? - yes

Cyclospora caytanesis

disease -

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

Protozoa (Apicomplexia)

disease - cyclosporiasis

symptoms - persistant diarrhea, myalgia, fatigue, vomitting, malaise, abdominal cramps, bloating, flatus

geographic region - tropical and subtropical regions

transmission - ingestion of oocysts

specimen & identification - stool; autofluorescence on wet mount, acid-fast stain

pathogenic? - yes

Plasmodium vivax

disease -

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

life cycle -

prevention -

Protozoa (Apicomplexia)

disease - malaria

symptoms - fever attacks every second day, anemia, splenomegaly

geographic region - central & south America, Africa, southern Europe/Asia

transmission - mosquito (vector)

specimen & identification - blood in EDTA; thin & thick smears

pathogenic? - yes

life cycle - different in humans than mosquito; in humans lifecycle occurs in liver and blood

prevention - chemoprophylaxis, insecticide tents, preventative treatment (pregnant women)

Plasmodium ovale

disease -

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

life cycle -

prevention -

Protozoa (Apicomplexia)

disease - malaria

symptoms - fever attacks every second day, anemia, splenomegaly

geographic region - central & south America, Africa, southern Europe/Asia

transmission - mosquito (vector)

specimen & identification - blood in EDTA; thin & thick smears

pathogenic? - yes

life cycle - different in humans than mosquito; in humans lifecycle occurs in liver and blood

prevention - chemoprophylaxis, insecticide tents, preventative treatment (pregnant women)

Plasmodium malariae

disease -

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

life cycle -

prevention -

Protozoa (Apicomplexia)

disease - malaria

symptoms - fever attacks every third day, anemia, splenomegaly

geographic region - central & south America, Africa, southern Europe/Asia

transmission - mosquito (vector)

specimen & identification - blood in EDTA; thin & thick smears

pathogenic? - yes

life cycle - different in humans than mosquito; in humans lifecycle occurs in liver and blood

prevention - chemoprophylaxis, insecticide tents, preventative treatment (pregnant women)

Plasmodium falciparum

disease -

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

life cycle -

prevention -

Protozoa (Apicomplexia)

disease - malaria

symptoms - fever attacks every second day, anemia, splenomegaly

geographic region - Africa

transmission - mosquito (vector)

specimen & identification - blood in EDTA; thin & thick smears

pathogenic? - yes

life cycle - different in humans than mosquito; in humans lifecycle occurs in liver and blood

prevention - chemoprophylaxis, insecticide tents, preventative treatment (pregnant women)

Babesia sp.

disease -

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

Protozoa (Acomplexia)

disease - babesiosis

symptoms - asymptomatic or flu-like, anemia

geographic region - North America

transmission - tick-borne

specimen & identification - blood; intracellular, ring-form

pathogenic? - yes

Toxoplasma gondii

disease -

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

Protozoa (Acomplexia)

disease - toxoplasmosis

symptoms - mono-like in healthy but organ inflammation in immunocompromised

geographic region - worldwide

transmission - ingestion *worry about transmission to fetus

specimen & identification - test for IgG & IgM Ab, biopsy staining

pathogenic? - yes

Enterobius vermicularis (pinworm)

symptoms -

transmission -

specimen & identification -

lifecycle -

pathogenic? -

Helminth (Nematode)

symptoms - intense itching

transmission - fecal-oral

specimen & identification - tape prep/pinworm paddle

lifecycle - female migrated from intestines to perianal folds and deposits eggs at night

pathogenic? - yes

Trichuris trichiura (whipworm)

disease -

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

Helminth (Nematode)

disease - trichuriasis

symptoms - mostly asymptomatic, but if heavy worm burden --> other serious symptoms

geographic region - worldwide

transmission - soil, fecal-oral

specimen & identification - microscopic examination of stool

pathogenic? - yes

Strongyloides stercoralis (threadworm)

disease -

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

Helminth (Nematode)

disease - gut or lung infection

symptoms - mostly asymptomatic, but sometimes red rash at original site or disseminated

geographic region - worldwide

transmission - soil transmitted, penetration of skin

specimen & identification - microscopic examination of sputum & stool

pathogenic? - yes

Trichinella spiralis

disease -

symptoms -

transmission -

specimen & identification -

pathogenic? -

Helminth (Nematode)

disease - trichinosis or trichinellosis

symptoms - may be asymptomatic or GI or muscle encystment

transmission - ingestion of meat with encysted larvae

specimen & identification - ELISA, muscle biopsies, eosiniphilia

pathogenic? - yes

Schistosoma haematobium

disease -

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

Helminth (Trematode)

disease - bladder fluke

symptoms - hematuria, anemia, bladder fibrosis, associated with bladder cancer

geographic region - freshwater of southern Africa, Egypt, and middle east

transmission - penetration of skin by free-living cercariae

specimen & identification - urine; EIA or microscopic examination

pathogenic? - yes

Diphyllobothrium latum

disease -

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

Helminth (Cestode)

disease - intestinal infection

symptoms - asymptomatic, abdominal pain, weight loss, vitamin B12 deficiency

geographic region - parts of U.S., Scandinavia, Latin America, Asia, Africa

transmission - larva ingested in uncooked/undercooked fish

specimen & identification - microscopic examination of stool

pathogenic? - yes

Taenia saginata

disease -

symptoms -

transmission -

specimen & identification -

pathogenic? -

Helminth (Cestode)

disease - Taeniasis

symptoms - asymptomatic, mild GI

transmission - ingestion of cysticercus larvae in undercooked beef

specimen & identification - microscopic examination of stool

pathogenic? - no

Taenia solium

disease -

symptoms -

transmission -

specimen & identification -

pathogenic? -

Helminth (Cestode)

disease - cysticercosis

symptoms - infection of other organs with cysticercus

transmission - ingestion of cysticercus larvae in undercooked pork

specimen & identification - microscopic examination of stool, immunoassay

pathogenic? - yes

Hymenolepsis nana

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

Helminth (Cestode)

symptoms - asymptomatic or symptoms if heavy word burden

geographic region - most common tapeworm in U.S., but found globally

transmission - ingestion of embryonated egg or arthropod with cysticercoid larva

specimen & identification - microscopic examination of stool

pathogenic? - yes

Dipylidium caninum

disease -

symptoms -

transmission -

specimen & identification -

pathogenic? -

Helminth (Cestode)

disease - intestinal infection

symptoms - asymptomatic or mild symptoms

transmission - contact with dog and cat tapeworm

specimen & identification - microscopic examination of stool

pathogenic? - yes

Echinococcus granulosus

disease -

symptoms -

geographic region -

transmission -

specimen & identification -

pathogenic? -

Helminth (Cestode)

disease - intestinal infection

symptoms - hydatid cysts

geographic region - worldwide

transmission - ingestion of eggs

specimen & identification - radiologic imaging, serology

pathogenic? - yes

Echinococcus multilocularis

disease -

symptoms -

geographic region -

transmission -

pathogenic? -

Helminth (Cestode)

disease - alveolar echinococcosis

symptoms - hydatid cysts

geographic region - Eurasia & North America

transmission - ingestion of eggs

pathogenic? - yes

Ixodes scapularis

diseases transmitted -

geographical region -

visual identification -

Ectoparasite (tick)

diseases transmitted - babesiosis, erlichiosis, relapsing fever borreliosis, lyme disease, anaplasmosis, powassan virus disease (B.E.R.L.A.P.)

geographical region - Eastern US

visual identification - mouthparts longer than basis capituli, inornate, no festoons, no eyes, anterior anal groove

Amblyoma americanum

diseases transmitted -

geographical region -

visual identification -

Ectoparasite (tick)

diseases transmitted - heartland, erlichiosis, Tularemia, southern tick rash illness (H.Er.T.S.)

geographical region - Southeastern US

visual identification - mouthparts longer than basis capituli, ornate, eyes, festoons, white spot (lonestar), posterior anal groove

Pediculus humanis (subspecies: capitis & corporis)

diseases transmitted -

visual identification -

Ectoparasite (lyse)

diseases transmitted - only by corporis --> endemic typhus, trench fever, louse-borne relapsing fever

visual identification - louse body longer than wide, nit (egg) is flattened operculum

Pediculus pubis (pubic lyse)

transmission -

visual identification -

Ectoparasite (lyse)

transmission - sec

visual identification - body wide as it is long, nit (egg) is raised and conical operculum

Sarcoptes scabiei

diseases transmitted -

geographical region -

visual identification -

transmission -

Ectoparasite (scabies)

diseases transmitted - human scabies (human itch mite)

geographical region - worldwide

visual identification - roundish mite with 4 pairs of legs, oval-shaped egg

transmission - direct, prolonged, skin to skin contact

Viral structure (4)

- viral genomes (DNA or RNA) in a protein coat known as a capsid

- genome + capside = nucleocapsid

- entire virus = virion

- sometimes an envelope

Explain host cell tropism

Viruses show host specificity because the viral anti-receptor only binds to certain host cell receptors

What is viral neutralization by antibodies

Patient antibodies prevent cell culture identification

Viral Classification System

- DNA

- DS, linear or circular

- SS, linear or circular

- RNA

- DS, linear

- SS, linear --> positive (mRNA), negative, ambisense (circular), segmented

What is the role of mRNA in viral replication

All types of nucleic acids get transcribed into mRNA and translated into proteins

First step of viral replication

attachment

- virus attaches to the target cell by receptors (tropism)

- anti-receptors on virus + host cell receptors

Second step of viral replication

Entry/penetration

- naked virions directly penetrate the membrane

- enveloped virions enter by endocytosis

- once into the cell the virions lose their protein coat releasing the genome (RNA-->cytoplasm, DNA-->nucleus)

Third step of viral replication

replication & translation (biosynthesis)

- viral genome directs host cell to make viral proteins and replicate the genome

*host cell metabolism may stop

Fourth step of viral replication

Assembly of viral particles

- capsid protein subunits form capsomers

- capsomers combine to form capsid

- capsid and genome combine to form nucleocapsid

Fifth step of viral replication

Release

- naked viruses release by lysis (kills host cell)

- enveloped viruses release by budding

Why are RNA viruses more prone to rapid mutation than DNA viruses

Because RNA polymerase does not have an exonuclease proofreading function

Basis of viral culture & identification

- grow virus in culture cells

- detect by: cytopathic effect, hemadsorption, immunostaining, neutralization

Basis of Ag detection by EIA & immunofluorescence

- identifies viral Ags to identify and classify viruses

Basis of PCR and RT PCR

- rapid, high volume, specific

- non-culturable viruses

- quantitative can be used to monitor therapy effectiveness

What cell culture can enteroviruses grow in?

PMK, HDF

What cell culture can influenza grow in?

PMK, HDF

What cell culture can adenovirus grow in?

PMK, HDF, HeP-2, A549

What cell culture can HSV grow in?

PMK, HDF, HeP-2, A549

What cell culture can SARS-CoV-2 grow in?

VERO

Rotavirus

genome type -

disease -

transmission -

diagnostic test -

genome type - segmented dsRNA

disease - viral gastroenteritis in infants and children

transmission - fecal-oral

diagnostic test - EIA for Ag detection, RT PCR

Norovirus

genome type -

disease -

transmission -

diagnostic test -

genome type - ssRNA

disease - viral gastroenteritis "stomach flu"

transmission - fecal-oral --> very low infectious dose

diagnostic test - PCR, EIA but low sensitivity

Poliovirus

genome type -

disease -

transmission -

genome type - ssRNA

disease - asymptomatic or mild flu-like, paralytic polio

transmission - fecal-oral

Hepatitis A

genome type -

disease -

transmission -

diagnostic test -

genome type - ssRNA

disease - acute flu-like symptoms and jaundice

transmission - fecal-oral

diagnostic test - IgM detection, nucleic acid testing

Hepatitis C

genome type -

disease -

transmission -

diagnostic test -

genome type - ssRNA

disease - acute asymptomatic and self-limiting, or chronic leading to liver cirrhosis

transmission - blood borne --> IV-drug use, mom to child

diagnostic test - ELISA for HCV Ab, qualitative & quantitative HCV RNA, HCV genotyping

What are the steps of viral replication that are targeted by anti-virals? (3)

- protein coat release

- replication & translation

- release of virus from infected cells

Rubella

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - ssRNA, enveloped

disease/symptoms - German measles --> rash, lymphadenopathy, mild fever

Congenital --> development impairment

transmission - respiratory / placental

diagnostic testing - viral culture preferred, IgM 4x rise in titer

Measles

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - ssRNA enveloped

disease/symptoms - fever, cough, rash, Koplick's spots, SSPE (encephalitis)

transmission - respiratory aerosol

diagnostic testing - IgM, PCR, viral culture

Rabies

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - ssRNA enveloped (bullet shaped)

disease/symptoms - flu-like, CNS

transmission - zoonotic by bite injecting saliva, travels via peripheral nerves to CNS

diagnostic testing - saliva: RT PCR, serum & CSF: Ab tests, skin biopsy & brain tissue: DFA

hCoVs

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - ssRNA, enveloped

disease/symptoms - mild coldlike, GI tract

transmission - airborne

diagnostic testing - multiplex molecular panels

MERS-CoV

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - ssRNA, enveloped

disease/symptoms - respiratory, GI, kidney failure

transmission - zoonotic (camels), airborne

diagnostic testing - molecular testing

SARS-CoV

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - ssRNA, enveloped

disease/symptoms - high fever, respiratory

transmission - zoonotic, airborne

diagnostic testing - no longer circulatin

SARS-CoV2

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - ssRNA, enveloped

disease/symptoms - mild to severe

transmission - zoonotic, droplet/airborne

diagnostic testing - rapid Ag test, multiplex molecular panels, culture, swabs

influenza A/B

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - ssRNA segmented, enveloped

disease/symptoms - flu-like

transmission - droplet

diagnostic testing - rapid Ag tests, PCR, culture

HIV

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - retrovirus (enveloped ssRNA)

disease/symptoms - CD4+ cells are targeted; acute --> chronic --> AIDS

transmission - blood, body fluids

diagnostic testing - screening (Ab detection), combo immunoassay (HIV 1/2 Ab & p24 Ag), Ab differential assay, HIV 1 RNA assay

Herpes Simplex Virus 1 & 2 (HSV)

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - dsDNA

disease/symptoms - oral & congenital herpes --> recurrent disease, neonatal herpes, ocular herpes, HSV encephalitis

transmission - direct contact with virus secretions

diagnostic testing - viral culture (fast), DFA typing, serology, PCR

Varicella Zoster Virus (VZV)

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - dsDNA

disease/symptoms - chicken pox & shingles

transmission - contact with fluid from skin vesicles or through aerosols

diagnostic testing - clinical findings, viral culture, DFAs, PCR

Epstein-Barr Virus

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - dsDNA

disease/symptoms - mononucleosis

transmission - contact with saliva

diagnostic testing - monospot test (heterophile antibodies), VCA antibodies, early Ag antibodies, EBV nuclear Ag antibodies

Antibodies found in an individual susceptible to mono

Anti-EA - negative

Anti-VCA IgM - negative

Anti-VCA IgG - negative

Anti-NA IgG - negative

Antibodies found in a individual with a primary mono infection?

Anti-EA - positive

Anti-VCA IgM - positive

Anti-VCA IgG - positive

Anti-NA IgG - negative

Antibodies found in a individual who was previously infected with mono?

Anti-EA - negative

Anti-VCA IgM - negative

Anti-VCA IgG - positive

Anti-NA IgG - positive

Cytomegalovirus (CMV)

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - dsDNA

disease/symptoms -

HEALTHY --> asymptomatic, goes latent, rarely reactivated

IMMUNOCOMPROMISED --> high risk for CMV disease

transmission - vertical or horizontal, contact with someone shedding the virus, contact with body fluids, blood transfusion or transplant

diagnostic testing - culture (slow growth), pp65 antigen detection, PCR

Human Papillomavirus (HPV)

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - dsDNA

disease/symptoms - cervical cancer from high-risk strains and variety of warts from low-risk strains

transmission - sexual contact

diagnostic testing - NAT test for detection of HPV, partial and extended genotyping for strain differentiation

Hepatitis B Virus (HBV)

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - partially circular dsDNA

disease/symptoms - Acute & Chronic hepatitis

transmission - bloodborne

diagnostic testing - serology --> identification of antigens and antibodies in serum

What is found in an individual's serum who is susceptible to HBV?

Nothing!

What is found in an individual's serum who is immune from infection of HBV?

Anti-HBs

Anti-HBc IgG

What is found in an individual's serum who is immune from vaccination of HBV?

Anti-HBs

What is found in an individual's serum who has an acute infection with HBV?

HBsAg

HBeAg

Anti-HBc IgM

What is found in an individual's serum who has a chronic infection with HBV?

HBsAg

HBeAg

Anti-HBe

Anti-HBc IgG

Parvovirus B19

genome type -

disease/symptoms -

transmission -

diagnostic testing -

genome type - ssDNA

disease/symptoms - Parvovirus B19 also known as Fifth disease which has a characteristic symptom of a "slapped-cheek" appearance

transmission - respiratory droplets, blood or blood products, vertical

diagnostic testing - serology, PCR