Zoonoses

Question 1

Leptospira

Answer 1

Gram negative, obligate aerobe spirochete
Periplasmic flagella. Two internal flagella within periplasma
Secretes soluble haemolysin (bursts RBCs)

Question 2

Leptospirosis/Weil’s disease

Answer 2

Caused by Leptospira interrogans
Serogroup icterohaemorrhagiae is main serovar causing disease
Contact with infected urine, soil, food (from carrier or infected animal)

Question 3

Leptospirosis effects

Answer 3

Renal injuries (interstitial nephritis)
Hepatocellular disease due to vasculitis
Meningitis
Symmetric pretibial rash

Question 4

Leptospire infection

Answer 4

Penetrate skin through breaches
Disseminate haematogenously and establish in target organ
Produce adhesins for binding to host cell components (ECM, cadherin)
Secrete proteases and haemolysins that degrade host membrane
Can survive within macrophages and induce apoptosis

Question 5

Leptospira treatment/prevention

Answer 5

Antibiotics (penicillin, tetracycline)
Serovar-specific vaccine
Prophylaxis with short/long-term tetracycline

Question 6

Borrelia burgdorferi

Answer 6

Helical cell shape
Periplasmic flagella
BBK32 protein forms catch bonds with endothelial cells of blood vessels to move along without being swept away

Question 7

B. burgdorferi genome

Answer 7

One large linear chromosome
21 other linear and circular plasmids
Plasmid Ip25 necessary for Borrelia infection
Uses manganese to avoid scavenging for iron (no free iron in tissues/fluids as a defence mechanism)

Question 8

B. burgdorferi life cycle

Answer 8

Unfed larval ticks acquire B. burgdorferi by feeding on infected rodent
Spirochetes multiply and persist in midguts of tick to nymph stage
When nymph feeds, spirochetes migrate to salivary glands and are transmitted to new mammal host

Question 9

Lyme disease

Answer 9

Stage 1 3-30 days after bite
Flu-like symptoms (fatigue, headache)
Skin rashes in 80% of individuals
Stage 2 weeks or months after
Severe headache and neck pain
Arthritis in 60% of patients
Neurological symptoms

Question 10

B. burgdorferi infection

Answer 10

Decreases expression of OspA lipoprotein (prevents injection) which allows detachment from the gut
Expresses OspC which aids flow to tick salivary glands
Tick protein Salp15 binds OspC in salivary glands
Protects against neutralising antibodies in the new host

Question 11

Cryptosporidium

Answer 11

Coccidian protozoan parasite
Hosts are animals (livestock) and humans
Cryptosporidium parvum causes cryptosporidiosis
Pathogenic form is oocyst

Question 12

Cryptosporidium infection

Answer 12

Sporozoites excyst from oocysts and invades epithelial cells of the gastrointestinal tract
Develops into trophozoite
Cell death results from invasion, multiplication and extrusion
T cell-mediated inflammation can produce microvilli death and crypt. growth

Question 13

Cryptosporidiosis

Answer 13

Diarrhoea, pain, fever
Symptoms last longer in immunocompromised individuals
No effective treatment (eukaryotic cell within eukaryotic human)