Leptospirosis in people is known by a variety of names, reflecting
the sources of infection, e.g., "rice-field fever"
and "cane-cutters fever" (transmission from
contaminated water) and "swine herder's disease"
(transmission from contact with infected animals).
Leptospirosis cases can occur either sporadically or in epidemics,
with an incubation period of ~10 days. Humans are susceptible
to infection with a variety of serovars.
- The incidence of disease is highest in tropical areas, especially
when heavy rainfall increases risks for waterborne infection
and drives rodents into urban dwellings.
- In 2000, there was a massive outbreak associated with flooding
in Thailand in which over 5,000 people were infected and over
180 people died.
- In many cases, infection occurs through mucosal contact with
water or soil contaminated with the urine of infected animals.
Such contact may occur through outdoor jobs, or just recreational
activities, e.g., kayaking or swimming in contaminated waters
(triathlons, eco-challenge races).
- Veterinarians, farmers and abattoir workers are at particularly
increased risk for infection from contact with contaminated urine.
- Veterinarians and veterinary technicians should handle even
routine urinalysis specimens as if they contain leptospires,
taking precautions such as gloves and a face shield (to prevent
mucosal splashes). Similar precautions should be taken by staff
housing down dog runs etc.
- In one survey, 15% of abattoir workers were sero [+], and
the rate of seropositivity was directly proportional to a worker's
number of years on the job!
- In 1998, 9 people who worked with the University of Missouri
swine herd developed leptospirosis. (See Campagnolo et al.,
2000)
- The major risk factors above and beyond pig contact were
smoking and drinking beverages while working with the pigs; hand
washing was protective.
- Other occupations at risk include sewer workers, members
of the military, and rice and sugar cane plantation employees.
- In 1996, a golfer apparently contracted leptospirosis just
by going into a ditch to recover an errant golf ball.
Human infections with Leptospira are broadly classed
as icteric (10% of cases) or anicteric (less severe; 90% of cases).
Human infections with Leptospira begin, after an
incubation period of 7-12 days, with fever (biphasic) and "flu-like"
illness. Patients may then develop intense headaches, severe
myalgia, abdominal pain, nausea, diarrhea, and sometimes rash,
conjunctivitis and conjunctival hemorrhage.
"Weil's disease" (icteric form)
This is the name for the classic hepatic and renal form of
leptospirosis in humans, which is most often due to infection
with serovar L. icterohaemorrhagiae. The clinical presentation
may begin as described above for the anicteric form, but subsequently
include:
- petechiae
- hepatomegaly and jaundice
- The jaundice is primarily due to hepatocellular dysfunction
rather than fulminant hepatic necrosis.
- ALT/AST levels rarely exceed 100-200 and SAP levels are only
moderately elevated.
- renal tubular damage >>> renal insufficiency
- The renal insufficiency follows renal tubular damage due
to hypoxia or a direct toxic effect of the leptospires.
Recovery can take months and mortality can approach 20% if
liver/renal compromise is not treated aggressively.
Leptospiral meningitis
Aseptic meningitis can occur as a sequelae of either Weil's
disease or anicteric leptospirosis. The meningitis is thought
to be immune-mediated, since the organism is generally not present
in the CSF by the time clinical signs develop.
Leptospiral Pulmonary hemorrhage
Leptospira infections affected about 2,500 people and
killed at least 16 in Nicaragua in 1995. This outbreak was initially
attributed to a "Mystery disease." Illness began
following a period of substantial flooding. Specific risk factors
for infection included walking in creeks, having household rodents
and owning dogs with Leptospira titers >400.
- The unique feature in these cases was a syndrome of pulmonary
hemorrhage. This is a rare manifestation of leptospirosis. However,
similar cases have been reported from Southeast Asia and, most
recently from Argentina in 2000-2001.
