Leptospirosis: Symptoms, Transmission, and Prevention
Leptospirosis
Overview
Leptospirosis is an acute infectious disease with systemic involvement. It is endemic and can become epidemic under certain conditions. Infections range from asymptomatic or subclinical to severe, anicteric or icteric, with high mortality. The subclinical form often mimics other syndromes.
Anicteric Form (60-70% of cases)
This form has two phases:
- Septicemic Phase: Characterized by hepatomegaly (enlarged liver), sometimes splenomegaly (enlarged spleen), gastrointestinal bleeding, myalgia (muscle pain) in calves, thighs, abdomen, and paraspinal muscles, photophobia (light sensitivity), chest pain, dry cough (with or without hemoptysis), and rashes (macular, maculopapular, urticarial, or petechiae). Mucosal hyperemia (redness) lasts 4-7 days.
- Immune Phase: Marked by severe headaches, vomiting, signs of meningeal irritation, and uveitis (eye inflammation). This phase lasts 1-3 weeks.
Icteric Form (Weil’s Disease)
This more severe form involves renal failure, hemorrhagic phenomena, and hemodynamic changes. Symptoms are more intense than the anicteric form, lasting 1-3 weeks, with a mortality rate of 50-20%.
Other Names
Swamp fever, autumnal fever, seven-day fever, canine typhus.
Etiologic Agent
Leptospira, a helical aerobic spirochete bacterium. Seven pathogenic species are known, the most important being L. interrogans. Over 200 serovars exist, each with preferred host(s), though one animal can harbor multiple serovars. Any serotype can cause various clinical presentations in humans. In some regions, the most severe cases are linked to the icterohaemorrhagiae and Copenhageni serovars.
Reservoir
Rodents, especially domestic ones, are the primary reservoirs. Domestic animals such as dogs, cattle, pigs, sheep, goats, and horses can also be carriers.
Transmission
Contact with water or soil contaminated by the urine of infected animals (mainly rodents). Rarely, direct contact with infected animal blood, tissue, organs, or urine.
Incubation Period
24 hours to 30 days (average 7-14 days).
Communicability Period
As long as leptospires are present in the urine of the infected person or animal. In animals, this can last months, years, or even a lifetime, depending on the species. Human-to-human transmission is rare.
Complications
Gastrointestinal and pulmonary hemorrhage, interstitial pneumonia, acute renal failure, electrolyte and acid-base imbalances, circulatory collapse, congestive heart failure, multiple organ failure, and death.
Diagnosis
Clinical, epidemiological, and laboratory testing.
Epidemiological Characteristics
Leptospirosis is a zoonosis and a public health concern. Floods and heavy rains in tropical and subtropical regions increase human contact with contaminated water and mud, leading to outbreaks. It occurs in both urban and rural areas, but many cases are linked to poor living conditions and sanitation, especially at the household level. The population is generally susceptible, with the 20-49 age group most affected. Certain professions (e.g., drain cleaners, farmers, veterinarians, animal handlers, fishermen, butchers, laboratory workers, firefighters) have increased risk.
Objectives
Implement preventative measures, especially before heavy rains in areas with cyclical occurrences. Provide appropriate treatment for severe cases to reduce mortality.
Notification
Reportable disease nationwide.
Control Measures
- Prompt medical care
- Case notification, investigation, and confirmation
- Risk area identification and control implementation
- Public awareness and education, especially before rainy seasons, to avoid contact with floodwaters without protection
- Rodent control and improved sanitation
- Environmental disinfection to prevent contamination by animal urine
- Cleanliness of kennels and animal breeding areas, removing leftover food to deter rodents
- Isolation and treatment of infected animals
- Immunization of domestic animals (dogs, cattle, pigs) with vaccines based on prevalent serovars