Incidence: approximately 870k cases worldwide annually
Geography
Widespread
Incidence in Tropical Regions is 10x Higher than that in Temperate Regions
Tropical Cases are Seen Mainly in Areas with High Poverty
Highest Number of Annual Cases are Reported in Hawaii: possibly due to ongoing legally required reporting of cases
Peak Areas in Southern and Pacific Coastal States
Cases Have Been Reported in Florida
Risk Factors
Occupational
Abattoir Workers
Farming (Rice, etc)/Ranching
Laboratory Workers
Loggers
Military
Pet Traders
Sewer Workers
Trappers
Recreational
Canoeing/Kayaking
Freshwater Swimming
Trail Biking
Household
Pet Dogs
Domesticated Livestock
Rainwater Catchment Systems
Rodents
Other
Accidental Laboratory Exposure
Contact with Wild Rodents
Skin Lesions
Walking Barefoot Through Surface Water
Transmission/Microbiology
Transmission
Mammalian Vectors: infected animals may be asymptomatic or manifest clinical infection
Rodents: most important reservoir
Infection Usually Occurs Early in Life with Shedding or Organism Intermittently or Continuously Throughout Life (Typically with Contamination of Water Sources)
Cattle
Swine
Dogs
Horses
Sheep
Goats
Cats: rarely
Modes of Infection
Exposure to Animal Urine, Contaminated Water/Soil, or Infected Animal Tissue with Entry Via Wound (Cuts, Abraded Skin), Mucous Membranes, or Conjunctivae
It is Unclear as to Whether Leptospira Can Penetrate Intact Skin
Ingestion of Contaminated Food: rarely
Transplacental Infection: has been reported
Microbiology
Leptospira Species: 9 species are known to be pathogenic
Leptospira Interrogans
Leptospira kirschneri
Leptospira noguchii
Leptospira alexanderi
Leptospira weilii
Leptospira alstonii
Leptospira borgpetersenii
Leptospira santarosai
Leptospira kmetyi
Diagnosis
Serology
Most Commonly Used Diagnostic Methods
Techniques
Enzyme-Linked Immunosorbent Assay (ELISA)
Indirect Hemagglutination
Microscopic Agglutination Test (MAT)
Most Specific with Detection of a 4x-Increase Between Acute and Convalescent Serum Specimens
Single Titer of >1:800 is Reasonable Evidence of Current or Recent Leptospira Infection
Macroscopic Agglutination Test
Molecular Tests
Techniques
Real Time PCR
Loop-Mediated Isothermal Amplification (LAMP)
Culture
Technique
Blood Culture (see Blood Culture, [[Blood Culture]]): insensitive
Urine Culture (see Urine Culture, [[Urine Culture]]): become positive during the second week of illness and remain positive for 30 days after resolution of symptoms
Cerebrospinal Fluid Culture (see Lumbar Puncture, [[Lumbar Puncture]]): usually positive during the first 10 days of illness
Clinical Manifestations
General Comments
Clinical Course of Variable, Ranging from Subclinical Illness to Fata Illness
Most Cases are Mild and Self-Limited
Incubation Period: 2-26 days
Typical Presentation
Abrupt Onset of Fever, Rigors, Myalgias, and Headache: occurs in 75-100% of cases
Physiology: outer membrane protein of Leptospira inhibits the Na/K/Cl cotransporter in the thick ascending limb of Henle, causing hypokalemia and renal sodium wasting
Physiology: outer membrane protein of Leptospira inhibits the Na/K/Cl cotransporter in the thick ascending limb of Henle, causing hypokalemia and renal sodium wasting