Atypical lymphocytosis in leptospirosis: a cohort of hospitalized cases between 1996 and 2009 in State of Rio de Janeiro, Brazil

Abstract

INTRODUCTION: Leptospirosis is a zoonotic disease found in tropical and temperate countries, and its clinical diagnostic confusion with arboviruses (dengue fever, oropouche fever and yellow fever), Brazilian spotted fever, viral hepatitis and hantaviruses has been an ongoing public health concern. The aim of this observational study was to demonstrate an association between findings of atypical lymphocytosis and the progression of endemic leptospirosis. METHODS: A retrospective analysis was performed on the demographic, epidemiological, clinical and laboratory aspects of 27 human leptospirosis cases that occurred over a period of 13 years (1996-2009) with no reported epidemic outbreaks in Rio de Janeiro, Brazil. RESULTS: The overall mortality rate was 11.1% in our cohort of hospitalized cases. However, there was no mortality among patients with atypical lymphocytosis (OR = 11.1; 95% CI = 1.12-110.9; p = 0.04). Two patients who were in the septicemic phase showed signs of expansion of γδ T cell responses in peripheral blood. CONCLUSIONS: Atypical lymphocytosis may be observed in patients with leptospirosis. Our observations suggest that these atypical leukocyte subsets are associated with partial protection during the disease course of leptospirosis.

The panorama of animal leptospirosis in Rio de Janeiro, Brazil, regarding the seroepidemiology of the infection in tropical regions

“…Members of this serogroup are maintained by rodents, mainly the Norwegian rat ( Rattus norvegicus ) [36]. They are extremely virulent [37] and cause severe acute illness in several species, including humans [7,13]. Rats captured in Rio de Janeiro were highly infected [17], consistent with findings from other regions [38,39].…”

“…Despite inherent limitations of serological testing, we inferred that leptospirosis is endemic and widespread in Rio de Janeiro, since all tested animal species had high seroreactivity. It was not an unexpected result, since studies from other regions of Brazil [13,31-33] as well as from other tropical areas reported leptospirosis as a widespread infection [1,6,11]. Despite this, animal leptospirosis is often neglected and many practitioners, even from endemic regions, are only familiar with the acute syndromes of the disease.…”

“…In contrast, in rural areas, serovars that most commonly infect livestock (e.g. Hardjo), only rarely cause human infections [10,13,15]. Furthermore, the role of rodents in the rural cycle has been neglected and more studies are needed.…”

“…Tropical regions have many particularities that affect the occurrence of the infection, as well as its routes and disease severity [7,13,14]. In addition to geographical conditions and aspects as climate or topography, management factors and husbandry practices, as well as frequency of veterinary assistance, may affect overall seroprevalence and also the serovar distribution [3,9,15,16].…”

Atypical lymphocytosis in leptospirosis

“…Transmission from animal carriers to humans results from exposure to the urine of infected animals, either by direct contact or more frequently, through and reliable laboratory test, however, remains the major barrier for diagnosis and epidemiologic surveillance [1][2][3] . A diagnosis may be made on the basis of the clinical presentation and symptoms that show characteristics of the severe disease form together with a suggestive epidemiological history 3,4 .…”