Zoonotic Diseases Exam 2 Review

Describe the morphology of vibrio

gram -, curved rods, facultative anaerobes, flagella

What environment does vibrio live in?

water, pH 7-9, acid-sensitive, 18-37C

What species of vibrio exist?

cholerae, parahaemolyticus, vulnificus

Where does V. cholerae come from?

brackish water, infected copepods, enters fecal-orally in shellfish/plankton, endemic in areas with poor sanitation, caused 7 pandemics

What serotypes of V. cholerae exist?

150 based on O antigen, O1/O139 cause cholera, O1 split into classical/el tor that have toxin coregulated pilus/cholera toxin, O139 has capsule

What are the symptoms of cholera?

2-3d after consumption, usually mild, vomiting, cramps, diarrhea, death in 18h-few days without treatment

Who does V. cholerae infect?

high infectious dose due to stomach acidity, people with low stomach acid like infants, elderly, blood type O

What adhesins contribute to V. cholerae virulence?

accessory colonization factors, outer membrane protein, toxin coregulated pilus, must overcome peristalsis and invade enterocytes

What toxins does V. cholerae have?

AB dimeric exotoxins, binding domain B helps absorption via receptor mediated endocytosis, active domain A disrupts cell function, cytolytic toxins are degradative enzymes that cause hemolysis, necrosis, lethal if IV

What is the mechanism of action of cholera toxin?

B subunit binds to GM1 receptor, receptor-mediated endocytosis, travels to ER, A fragment ADP-ribosylates GTP-binding protein by transferring ADP-ribose from NAD, which keeps adenyl cyclase “on”, increasing cAMP, stimulating protein kinase A to open ion channels, causing hypersecretion of fluids/electrolytes

What treatments exist for cholera?

rehydration therapy with oral NaCl, KCl, trisodium citrate, rice flour, IV antibiotics, 3 vaccines available but none offer long term protection

Where does V. parahaemolyticus come from?

fecal-oral transmission in raw seafood, usually warm oysters in sun on boats, causes GI/enteric and wound infection

What virulence factors does V. parahaemolyticus have?

2 variants of T3SS and hemolysins tdh/trh on pathogenicity islands

Where does V. vulnificus come from?

raw seafood, aquatic environments, causes wound infections that can lead to amputation, 80x more likely in immunocompromised/liver disease people

What are the virulence factors of V. vulnificus?

capsular polysaccharide endotoxin, iron acquisition, flagella motility, hemolysin/cytolysin, metalloprotease exotoxins

What treatments exist for V. vulnificus?

fluid therapy, acid/base adjustment, antibiotics, carriers detected via antibodies after infection, test sewage

Describe the morphology of Clostridium

gram +, straight/slightly curved rods, anaerobic, spore forming, acid-sensitive

What kinds of spores does Clostridium form?

mostly ovoid subterminal, tetani has round terminal

How does Clostridium work with saprophytes?

commensals in the human gut initiate decomposition by invading blood and gut after an animal dies

What species of Clostridium exist?

120, difficile, perfringens, botulinum, tetani

What is antibiotic-associated diarrhea?

when antibiotics wipe out normal flora, C. difficile spores germinate and cause severe colitis

What are the risk factors for C. difficile?

surgery, colon diseases, chemotherapy, kidney disease, proton pump inhibitors that reduce stomach acid

What is fecal microbiota transplantation?

instilling stool from healthy donor into sick person to restore healthy gut flora, recently approved 2022

Describe the morphology of C. perfringes

capsulated, nonmotile, 5 strains a-e, identified with nagler reaction

What diseases are caused by C. perfringes?

food poisoning, gas gangrene, diarrhea in goats, mortality high in lambs

What is the mechanism of a-toxin of C. perfringes?

C domain binds, N domain active site, cleaves phospholipids and destroys membrane

What are neuraminidases?

cleaves glycosidic linkages of neuraminic acids, catalyze sialic acid hydrolysis, increases membrane permeability

Describe the morphology of C. tetani

motile with flagella, 10 types distinguished by H and O antigens, killed by 1% iodine in water

What is the mechanism of tetanospasmin?

prevents action of inhibitory motor neurons by cleaving synaptobrevin II, increasing excitability of spinal cord

How is C. tetani treated?

stop toxin production, antibodies to neutralize unbound toxin, tdap vaccine

What environment does C. botulinum live in?

naturally in soil, anaerobic so likes canned food, honey, deep wounds

What are the effects of botulinum toxin?

most lethal toxin known, 1.3-2.1ng/kg iv, inhibit acetylcholine secretion causing paralysis and death if unable to breathe, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, muscle weakness

What are the different types of botulism?

food borne, wound, infant, adult intestinal toxemia, iatrogenic

What is the mechanism of botulinum toxin?

heavy chain binds to gangliosides, receptor-mediated endocytosis, light chain enters cytoplasm, degrades SNARE proteins

What is the function of SNARE proteins?

synaptobrevin, syntaxin, SNAP-25, help fusion of vesicles with cell membrane, normally for exocytosis of acetylcholine

What are the different types of parasites?

protozoa, helminths, ectoparasites

What are protozoa?

single celled eukaryotes, enter body through any method

What some examples of protozoa?

giardia, cryptosporidia, toxoplasma, babesia, leishmania

Describe the life cycle of giardia

human definitive host, cysts ingested, multiply in gut, more cysts passed in stool

What are the symptoms of giardia?

diarrhea that doesn’t go away

Who does giardia infect?

kids in daycare, unsanitary water, types a-f can infect many species but mostly humans

How is giardia treated?

chlorinated water, antibiotics

Describe the life cycle of crystosporidium

2 forms of oocysts, one excreted as infectious and other has thin walls that bursts and replicates again

What are the symptoms of cryptosporidium?

watery, bloody diarrhea

Who does cryptosporidium infect?

young cattle, public pools, chlorination doesn’t kill it, just controls

Describe the life cycle of toxoplasma

rodents eat fecal oocysts, form tissue cysts, infected rodents eaten by cats, parasite replicates in cat gut, more oocysts excreted, mature outside 5d

Who does toxoplasma infect?

definitive host cats, but humans can get it from eating tissue cysts in meat from animals on farms with cats, or directly from cleaning litter boxes of pet cats, infected rodents have altered behavior, can cross placental barrier and cause abortions in sheep

Describe the life cycle of babesia

tick takes blood meal from infected rodent, replicates in tick gut, takes blood meal of another rodent/species and introduces sporozoites that infect RBCs

What are the symptoms of babesia?

fever, chills, anemia in immunocompromised

Describe the life cycle of leishmania

sandfly takes blood meal from infected human, multiplies in sandfly gut, takes blood meal of another human and injects parasite into skin, phagocytized by macrophages, multiplies and infects various cells

Who does leishmania infect?

definitive host humans, brazil, east africa, india, some species have reservoirs in stray dogs

What are the symptoms of leishmania?

visceral fever, weight loss, enlarged liver and spleen, 95% fatal if untreated, cutaneous skin lesions, lose mucous membranes

What are helminths?

roundworms/nematodes and flatworms/platyhelminths, flatworms divided into trematodes and cestodes

What some examples of roundworms/nematodes?

whipworms/trichuris, ascarids/toxocara canis, filarial worms/heartwor/lungworm

Describe the life cycle of whipworms/trichuris

eggs hatch in intestine, mate and multiply in gut, produce eggs passed in feces, eggs mature 10-60d outside

Describe the life cycle of toxocara canis

eggs hatch in intestine, larvae invade gut and travel through body to lungs, coughed up, swallowed again, mature worms produce eggs passed in feces

Who does toxocara canis infect?

travel to lungs in young dogs, form tissue cysts in older dogs and other species, can travel to fetus

What are the symptoms of toxocara canis?

depends where it migrates, liver, heart, respiratory, eye problems but mostly asymptomatic

Describe the life cycle of filarial worms/heartworm/lungworm

mosquito takes blood meal from infected dog, consuming microfilariae, parasite travels to salivary gland, takes blood meal from another dog/human, injecting parasite

What are the stages of development of filarial worms/heartworm/lungworm

L1-3 in mosquito, L3 deposited in skin of dog, mature to L4, migrates to muscles, mature to L5, enter blood stream, live in pulmonary artery, mate and produce microfilariae

Who does filarial worms/heartworm/lungworm infect?

definitive host dogs, can infect humans needs temp above 57 so spreads during warm seasons

What are the symptoms of filarial worms/heartworm/lungworm?

lesions in pulmonary vessels in humans, cough, exercise intolerance, heart failure in severe cases

What some examples of trematodes?

liver flukes: fasciola hepatica

Describe the life cycle of liver flukes

eggs passed in feces of ruminants/humans, infect and mature in snails, ruminants/human eats contaminated watercress, penetrate intestinal wall, live in bile duct, produce eggs

What are the symptoms of liver flukes?

holes in liver, fever, abdominal pain, jaundice, respiratory problems, 67% mortality in cattle

What some examples of cestodes?

taenia, echinococcus

Describe the morphology of a cestode

head/scolex and many segments/proglottids packed with eggs, are hemaphrodites

Describe the life cycle of taenia

human consumes raw infected meat, excrete 1000 proglottid segments with 50k eggs per segment into environment, consumed by pigs/cattle, invade intestine, travel to muscle

Describe the life cycle of echinococcus

ruminant ingests eggs in feces, dog consumes infected meat, passes eggs in feces, humans can ingest eggs and form cysts or infected meat and pass eggs

What is an enveloped virus?

has soft phospholipid bilayer with embedded proteins, can form strange shapes, vulnerable to disinfectants

What is a non-enveloped virus?

ball of protein, hard shell, symmetrical shape, resistant to disinfectants

What are the major surface proteins on influenza?

hemagglutinin and neurimidase

What are the subtypes of influenza?

H1-18, N1-11, almost all found in birds, last 2 of each in bats

What is antigenic drift?

slow accumulation of point mutations every time virus replicates

What is antigenic shift?

when 2 viruses infect same cell and new virus produced has mixed genome from both

What is LPAI?

H9N2, mild disease in chickens

What is HPAI?

H5N1, H5/7 can mutate into it, severe disease, 1 positive case means whole farm must be culled

How is avian influenza transmitted?

direct contact with feces, bedding, feed, water, equipment, but not airborne

What was the spanish flu?

1918, H1N1, 50mil dead, mostly due to 2nd pneumonia, no vaccines, antibiotics, controlled via education and masks

What was the asian flu?

1957, H2N2, 1-2mil dead, had antibiotics for pneumonia and vaccines

What was the swine flu?

2009, different H1N1, mostly mild, but vaccine development was too slow and missed peak

Why are birds not vaccinated in the US?

trade restrictions would prohibit any export of poultry if even 1 in the country was vaccinated due to masking symptoms

What is coronavirus?

enveloped virus with spike protein, big non-segmented RNA genome, no reassortment

What was SARS-CoV-1?

infection contained without vaccines due to testing, isolating, contact tracing, and asymptomatic people were rare, virus came from wild cats in live markets in asia

What was MERS?

2012 in saudi arabia, never took off because of low human-human spread, came from camels from bats

What was Nipah virus?

enveloped, non-segmented genome, came from pigs who ate contaminated fruit that bats also ate from, non pig farmers got it from contaminated sap, no vaccine

What was Hendra virus?

similar to nipah but in horses, vaccine for horses

What is Ebola?

enveloped, worm-shaped, causes leaky vessels, crying blood, anemia, hypovolemia, from bats

What are the major issues in food production?

food security, food safety, sustainability

What are the disadvantages of bacteriophage therapy?

strain specific, unstable efficacy, release bacterial endotoxins, immune response against phage, horizontal transfer of bacterial toxic gene

What are the disadvantages of vaccines?

specificity, short effectiveness, professionals, cost, delivery system for poultry

What are the disadvantages of natural antimicrobials?

unpredictable safety, low access to target, low uptake

What are the advantages of berry fruits?

black/blue berry promote probiotic growth, antioxidant, anti-inflammatory, poorly absorbed in small intestine so accumulate in large intestine

What are the advantages of citrus oil?

inhibits S. aureus biofilms, prevents mastitis

What are the advantages of olive?

enhance probiotics, decrease pathogenic bacteria, decrease inflammation

What metabolites are produced by commensal bacteria?

polypeptides, vit B, short chain FA, PUFAs

What are the characteristics of an ideal prebiotic?

inert polysaccharide, not absorbed in upper GI, able to alter microflora, enhance mineral absorption, selective substrate for a few bacteria

What are some examples of probiotics?

lactobacillus, S. thermophilus, B. bifidum

What are some examples of prebiotics?

beneo inulin, fructo-oligosaccharide

What are some disadvantages of a procommensal strategy?

long term side effects, may enhance pathogenic bacteria, lack of practical application on farms