Am. J. Trop. Med. Hyg., 80(3), 2009, pp. 345–346
Copyright © 2009 by The American Society of Tropical Medicine and Hygiene
Longitudinal Seroepidemiologic Study of Visceral Leishmaniasis in
Hyperendemic Regions of Bihar, India
Kamlesh Gidwani, Rajiv Kumar, Madhukar Rai, and Shyam Sundar*
Department of Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
Abstract. We conducted a seroepidemiologic study of visceral leishmaniasis (VL) in hyperendemic communities in
Bihar, India, to determine its seroprevalence. A direct agglutination test (DAT) and rK39 antigen strip test were used as
serologic tests. Capillary blood samples were collected on filter papers from 870 healthy persons (574 and 296 from households with or without VL, respectively). Of these persons, 230 (26.43%) were positive by DAT (titer > 1:1,600) and 120
(13.79%) were positive by the rK39 antigen strip test. During a two-year follow-up, 25 persons developed VL; 1 and 8 persons were positive by the rK39 strip test and DAT, respectively, and 1 was positive by both tests. Fifteen (2.57%) persons
who were seronegative at baseline also developed VL. Disease occurred more among persons living in the same household (24 of 25). However, there was no significant difference in disease conversion among children (5–15 years of age) and
adults (> 15 years of age). Seropositivity among asymptomatic persons is not a predictor for development of VL.
frequency of positive persons (28.4%) than the neighbor group
(22.82%; P = 0.04; Table 1).
Of the persons followed-up for 2 years, 25 (2.87%) developed clinical VL. There was no significant difference in disease
conversion among seronegative persons (15 of 583, 2.57%)
and seropositive persons (10 of 283, 3.48%). Of 63 (7.24%)
persons who were positive by both tests, only one showed disease conversion. Among 25 persons who showed disease conversion, 15 (3.84%) were males and 10 (2%) were females.
Among the seropositive group, at the end of three months,
six months, one year, and two years, three, one, two, and four
persons, respectively, showed disease conversion. Among the
seronegative group, one, five, five, and four persons, respectively, showed disease conversion. Of 25 persons who showed
disease conversion, 13 (3%) were 3–15 years of age and 12
(2.73%) were > 15 years of age. However, the difference
between these groups was not significant.
Interestingly, of the 25 persons who showed disease conversion, 24 were from households with VL cases (4.18%), whereas
only 1 was from the neighbor group (0.33%; P = 0.0013). This
finding indicated that persons from households with VL cases
are at a significantly greater risk of developing overt disease regardless of their serologic status than their neighbors.
The difference in disease conversion between persons from
households with VL cases and their neighbors has also been
observed in a study in Bangladesh.12
A high prevalence of seropositive but asymptomatic persons in areas endemic for VL has been reported.13,14 In our
study, 287 (33%) persons were serologically positive. Only
10 (3.48%) seropositive persons showed disease conversion.
However, 15 (2.57%) seronegative persons at baseline showed
disease conversion. Our findings differ from those of previous studies in India in which disease conversion was extremely
high in the seropositive group.5,6 The present study had a much
larger sample size with follow-up of entire cohort irrespective of serologic results. Prior studies did not consider the
serologically negative group. However, the variation in findings is difficult to explain if persons included are not properly screened for early disease or they developed the disease
a short time after testing. High conversion rates would be
erroneously reported. Significantly higher disease conversion rates in households with VL patients indicate increased
susceptibility compared with that in households without any
incidence of VL irrespective of rate of seropositivity.
Visceral leishmaniasis (VL) is a disease caused by intracellular protozoan parasite that spread by a female sand fly vector. If left untreated, this disease is fatal and is characterized by
prolonged fever, splenomegaly, hepatomegaly, pancytopenia.1
India is one of the most important foci in the world for VL.1,2
The number of cases of VL per year in India is approximately
100,000. Of these cases, the state of Bihar accounts for more
than 90%.3 Asymptomatic, infected persons are presumed to
be carriers and may play a significant role in transmission of
the disease.4 Seroepidemiologic data from disease-endemic
areas of India are scarce and based on small sample sizes.5,6
Serologic analysis of infection was conducted using the direct
agglutination test (DAT)7,8 and rK39 antigen strip test9,10
because of their ease of use in community-based studies and
reliable sensitivity and specificity.
To quantify incidence of infection, 200 households in
the hyperendemic community of the Sahebganj block of
Muzaffarpur district were selected for this study. Persons who
never had VL and had no fever in past month were enrolled
into the study. Children less than three years of age were
excluded; 870 healthy persons living in the disease-endemic
area were included. Enrolled persons were divided into two
groups: those from families in which there were members
who currently or previously had VL (household group) and
those from families with no history of VL (neighbor group).
Longitudinal follow-up was conducted up to two years at
intervals of three months, six months, one year, and two years.
The DAT11 and a commercially available rK39 antigen strip
test (Kalazar Detect; InBios, Seattle, WA) were used for serologic analysis.
Of the 870 persons, 574 were from the household group and
296 were from the neighbor group. Serologic analysis showed
that 120 (13.79%) persons were positive by the rK39 antigen
strip test and 230 (26.43%) were positive by the DAT. Only
63 persons (7.24%) were positive by both assays. Overall, 287
(33%) persons were seropositive by either test.
There was no significant difference in rK39 antigen strip
test results between the household (14.11%) and neighbor
(13.17%) groups. However, using data from the DAT, we
observed that the household group had a significantly higher
* Address correspondence to Shyam Sundar, Department of Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi
221005, India. E-mail: [email protected]
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GIDWANI AND OTHERS
TABLE 1
Serologic results of direct agglutination test (DAT) and rK39 antigen strip test for study participants
Category
Household
Neighbor
Total
Disease conversion
No. of persons
rK39 –ve, DAT –ve (%)
rK39+, DAT+ (%)
rK39 –, DAT+ (%)
rK39 +ve, DAT –ve (%)
574
296
870
25 (2.9%)
(24 household + 1 neighbor)
374 (65.15)
209 (70.60)
583 (67.01)
15 (1.7%)
(14 household + 1 neighbor)
44 (7.66)
19 (6.41)
63 (7.24)
1 (0.1%)
(household)
119 (20.73)
48 (16.21)
167 (19.19)
8 (0.9%)
(household)
37 (6.44)
20 (6.75)
57 (6.55)
1 (0.1%)
(household)
Genetic susceptibility to Leishmania spp. infection has been
reported in human VL.15,16 Thus, on the basis of our study, we
recommend that serologic status is not a good predictor for
conversion to clinical VL. Because serologic analysis using the
DAT and rK39 antigen strip test were performed only at the
baseline and further follow-up was conducted without serologic analysis, our study may have failed to detect seroconversion of persons who developed clinical VL during follow-up.
Received April 9, 2008. Accepted for publication September 27, 2008.
Financial support: This study was supported by the Kala-azar
Medical Research Center, Sitaram Memorial Trust, Muzaffarpur, India. Rajiv Kumar was supported by a fellowship from the
Indian Council of Medical Research, New Delhi, India.
Authors’ address: Kamlesh Gidwani, Rajiv Kumar, Madhukar Rai,
and Shyam Sundar, Department of Medicine, Institute of Medical
Sciences, Banaras Hindu University, Varanasi 221005, India.
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