Intro to Spirochetes and Leptospira

Question 1

Spirochete Gram characteristics

Answer 1

Gram negative

Stain poorly with Gram stain, can be demonstrated with dark field microscopy or silver stains

Question 2

Spirochete morphology

Answer 2

Tight/loose coiled morphology due to flagella (Axial filaments/endoflagella) located in the periplasmic space

Question 3

Pathogenic Spirochete members

Answer 3

Brachyspira
Borrelia
Treponema
Leptospira
-agents of systemic infections or intestinal infections

Question 4

Pathogenesis of Leptospira

Answer 4

Pathogenic species maintained in the renal tubules of reservoir animals -> reservoir animals excrete the bacteria through urine and contaminate the environment (water) -> pathogenic species survive for short period of time in ponds, rivers, surface waters, moist soil, and mud -> direct contact with urine or contaminated water results in infection in susceptible hosts

Question 5

Habitat of leptospires

Answer 5

Proximal convoluted tubules of kidney of maintenance hosts

Question 6

Virulence factors of Leptospira

Answer 6

Cell associated - Endoflagella, Outer membrane proteins, LPS (different from other Gram negative bacteria)
Extracellular - Hemolysins

Question 7

Types of pathology of Leptospira

Answer 7

Acute and chronic inflammation
During bacteremic phase intravascular hemolysis petechial hemorrhages and DIC
Jaundice (hepatitis), nephritis, placentitis (abortion), mastitis
Local infection of genital tract may lead to infertility (salpingitis) in some hosts

Question 8

Pathogenesis of Leptospira in maintenance hosts vs. incidental hosts

Answer 8

Maintenance hosts: privileged sites (kidneys or reproductive tract) = Long term shedding
Incidental hosts: recovery with short term shedding in urine

Question 9

Pathology of Leptospirosis in dogs

Answer 9

Renal or hepatic injury
Uveitis
Pulmonary hemorrhage
Abortion
Signs of renal and hepatic failure, including icterus

Question 10

Serology testing for Leptospirosis in dogs

Answer 10

Microscopic Agglutination Test (MAT)
Gold standard test
Measures antibody titers to Leptospira serovars using an agglutination test which uses live Leptospira serovars
Serovar specific (serovar selected based on geographic prevalence)

Question 11

Serology testing for definitive diagnosis of Leptospirosis in dogs

Answer 11

Perform MAT on a paired sera (acute and convalescent)
Four-fold increase in MAT titers is indicative of active infection
Low titers are seen in maintenance (reservoir hosts)
Vaccine-induced antibodies may interfere with interpretation

Question 12

Interpretation of Leptospirosis MAT in dogs

Answer 12

Serovar specific but cross reactivity is very common
Serovar showing highest titer is interpreted as infecting serovar - this concept is questionable because of Paradoxical titers in acute infection

Question 13

Acute infection MAT interpretation for Leptospirosis in dogs

Answer 13

Paradoxical titers in acute infection

In acute infection, positive titers are present for non-infecting serovars

Question 14

Ideal samples/tests for ante-mortem diagnosis to maximize diagnostic sensitivity of Leptospirosis in dogs

Answer 14

Blood - for PCR/FA
Urine - for PCR/FA
Serum - for MAT

Question 15

Treatment of Leptospirosis in dogs

Answer 15

Antimicrobials based on acute phase vs. carrier
Penicillins - during acute disease; ampicillin, amoxicillin

Doxycycline - to minimize carrier state; post-exposure prophylaxis state

Question 16

Vaccination for Leptospirosis in dogs

Answer 16

Protective immunity against leptospirosis is primarily humoral (mediated through antibodies)
“Old” vaccine - 2 serovars
“New” vaccine - 2 additional serovars
Protective antibodies are serovar specific

Question 17

Leptospirosis in cattle

Answer 17

Leptospira borgpetersenni serovar hardjo

Host adpted in cattle resulting in reproductive failure due to early embryonic death and repeated breeding

Question 18

Leptospirosis in horses

Answer 18

Clinical leptospirosis in horses is commonly associated with abortions, systemic illness in goals

Question 19

Serovars in US and Canada that are responsible for equine Leptospirosis

Answer 19

Serovars Pomona and Grippotyphosa

Question 20

Serovars of Leptospirosis in pigs

Answer 20

Serovars pomona and Bratislava
Reproductive failure (inferitlity and sporadic abortion)
Serovar Pomona is endemic in California sea lions

Question 21

Leptospirosis in humans

Answer 21

Most widespread zoonotic disease