Environmental Zoonotic Diseases

Question 1

What factors affect the following pathogens to survive in the environement?

• viruses
• bacteria
• protozoan parasites
• helminths
• prions

Answer 1

• Viruses: humidity, temperature, light, matrix – general rule: soft surfaces kill viruses more quicly as does low himidity and exposure to sunlight
• bactera: matrix, persistence within feces or animal tissues, spore-formation
• protozoans: matrix, persistence within feces or animal tissues, ability to encyst
• helminths: ability of eggs to survive harsh conditions
• prions: transmission via consumption of tissues, exposure to bodily fluids (pretty hardy)

Question 2

What makes anthrax persistent in the environment?

Answer 2

exists as an endospore

Question 3

Describe the transmission cycle of anthrax

Answer 3

infected animal –> biting fly –> bites human (cutaneous)

ingestion of contaminated meat

animal decomposition –> anthrax spores in environment –> inhalation or gets into an open wound in humans

Question 4

Describe the anatomy of an athrax spore and the function of each structure

Answer 4

• core (Cr): houses chromosomes + SARPs –> protection against UV and heat
• cortex (Cx): layer of PG –> keeps spore dry
• coat (Ct): multilayered protein shell –> prvents entry of toxins and attack by other microbes
• interspace (IS)
• exosporium (Exo): interacts with the environment

Question 5

What are the three forms of anthrax disease in domestic animals?

Answer 5

• apoplectic
• acute and subacute
• chronic

Question 6

What happens to anthrax is dead animals and in oozing blood?

Answer 6

• dead animal: readily destroyed by anaerobic bacteria
• blood: develops into spores

Question 7

What are the 3 forms of athrax disease in humans? Describe the tranmittence of each

Answer 7

1. pulmonary – inhaling spores
2. gastrointestinal – ingestion of spores
3. cutaneous – contact with infected caracasses, contaminated wool, hides, etc

Question 8

In anthrax pulmonary disease, how does the bacteria gain access to the pulmonary draning lymph nodes and thus go systemic?

Answer 8

1. trojan horse model: hitches a ride in lung phagocytes to PLNs where it escapes
2. jailbreak model: breaches the epithelial/endothelilar barrier –> enters PLN

Question 9

What are the two plasmids in athrax? what do they encode for?

Answer 9

1. PX01: encodes edema factor, lethal factor and protective Ag
2. PX02: encodes antiphagocytic capsule

Question 10

Describe the effects of the following antrax virulence factors:

• poly D glutamic acid capsule
• edema factor
• lethal factor

Answer 10

• capsule: inhibits phagocytosis, linear polymer that is weakly antigenic
• edema factor: inactivates neutrophils via adenyl cyclase which cleaves ATP –> cAMP and floods cells with cAMP to disrupt signaling pathways
• lethal factor: targets endotherial cells –> vasuclar leakage –> low blood volume –> septic shock; proteases that cleaves MAPK kinases –> disrupts signaling pathways

Question 11

What does anthrax’s protective Ag do?

Answer 11

creates a pore that facillitates entry of EF and LF into cells

Question 12

How can anthrax be diagnosed?

Answer 12

• microscopic examination of blood smears
• PCR amplification of EF or LF
• inoculation of lab animals

Question 13

What are the treatments for anthrax?

Answer 13

early antibiotic treatment

Question 14

what do old world vs new world hantavirsuses cause?

Answer 14

old world –> HFRS
new world –> HPS

Question 15

Why is there seasonality with HFRS?

Answer 15

• harvesting of wheat in summer
• harvesting rice in late fall

fields with rodent excreta –> harvesting kicks up a lot of dust

Question 16

What is the primary agent of HPS?

Answer 16

Sin nombre virus

Question 17

What is the transmission route for hantaviruses?

Answer 17

aersolized animal excreta (salvia, feces, urine)

Question 18

Why does hantaviruses horizontally transmit around male rodents more efficiently?

Answer 18

fighting and aggressive behaviours (e.g. urinating closer to each other)q

Question 19

What is the significance of andesvirus? What is worrisome about this?

Answer 19

linked to person-to-person tranmsision (only hantavirus that can do this

ANDV and SNV have (in lab) reassorted their M segments

Question 20

Describe the different strands of hantaviruses

Answer 20

• (S)mall: nuclecapsid
• (M)edium: glycoproteins G1/G2
• (L)arge: viral transcriptase/replicase

Question 21

Describe hantavirus viral entry

Answer 21

1. binds to B3 integrin R
2. endocytosis
3. nucleocapsid empty into cytoplasm via pH-dependent fusion with endosome
4. targeted to ER-Golgi

Question 22

What is the main difference between HFRS and HPS causing hantaviruses?

Answer 22

G1/G2 composition

Question 23

Briefly describe some pathogenic characterisitics of hantaviurses

Answer 23

• dysregulate B3 functions
• high [IL], [TNF], [IFN], and activated T cells –> pro-inflam immuine response

Question 24

How can we prevent HFRS and HPS?

Answer 24

• education: caution about rodent infested areas
• early treatment
• reduce rodent population

Question 25

what are some risk factors for contracting new world hantaviruses?

Answer 25

* greatest risk is rodents in the house (mostly farmers) * entrance to rarely used building

Question 26

What are virinos?

Answer 26

postulated idea that the scrapie's agent is a nucleid acid-PrPsc complex -- nucleic acid transmits genetic info for transmitting disease and PrPsc serves as protective coat

Question 27

What is PrPc?

Answer 27

normal host protein expressed on neurons,, glia, and other peripheral cells

Question 28

how do prions replicate?

Answer 28

mut --> shifts --> misfold --> misfolded PrPc (PrPsc) converts normal PrPc to misfold --> aggregates --> fragments to convert more protein

Question 29

Which tissue is most highly infected by prions?

Answer 29

brain, sc, eye (CNS)

Question 30

How can prions be tranmitted into the environment?

Answer 30

* nasal secretions * saliva -- salt blocks can trasmit * skin and mucous membrane lesions * feces and urine * in utero tranmission * milk

Question 31

Why was BSE so prevelant in cows?

Answer 31

high use of ruminant animal protein in dairy feeds

Question 32

lDescribe the different kinds of human prion diseases (i.e. how they are acquired)

Answer 32

_sporadic_ * sCJD * random mutation _inherited_ * autosomal dominant mutation * familial CJD (fCJD) _acquired_: * lCJD from contaminated surgical tools and tissues grafts * Kuru: from endoconnibalism * vCJD: consumption of BSE prion strain

Question 33

What are there more sCJD cases in elderly folks?

Answer 33

elders -- longer life --> greater chance of mutation

Question 34

For the following treatments of inactivating prions, describe their effectiveness: * standard autoclaving * boiling * phenol * 50% bleach

Answer 34

* autoclave = reduces infectivity * boiling = reduces * phenol = effective * bleach = effective