Seroprevalence of leptospira among rodents and shrews in public markets and hospitalized febrile patients in Unguja Island
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Date
2023-05
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Sokoine University of Agriculture
Abstract
Leptospirosis is a neglected infectious zoonotic disease of public health significance
caused by spirochete pathogenic bacteria of the genus Leptospira. This disease occurs
mainly in tropical and subtropical countries and affects animals and humans, of which
rodents and shrews are considered significant reservoirs of infection. Human might be
infected by Leptospira pathogen through a contact mode of transmission, either direct or
indirect, with the urine of infected animal’s host or a urine-polluted environment such as
water or soil. However, infected humans develop a range of symptoms undifferentiated
from other tropical diseases, such as malaria, particularly in regions with high malaria
prevalence. A cross-sectional study was carried out between January and April 2022 in
Unguja Island (i) to determine the seroprevalence of Leptospira infection among rodents
and shrews in public markets and (ii) to determine the seroprevalence of leptospirosis
among hospitalized febrile patients. Blood samples were collected from 210 live captured
rodents and shrews in the five purposively selected markets including Darajani,
Mombasa, Jumbi, Kwerekwe C and Mkokotoni. Likewise, 402 human blood samples
were collected from febrile patients who were attended to the selected hospitals namely
Mnazi Mmoja referral hospital, Kivunge district hospital and Makunduchi district hospital.
The Leptospira antibodies of rodents, shrews and humans were tested against five
serovars namely Sokoine, Lora, Pomona, Grippotyphosa and Hebdomadis using the
Microscopic Agglutination Test (MAT). The results indicated that out of 210 rodents and
shrews captured in public markets, 16 were seropositive for Leptospira serovars. Thus,
the overall seroprevalence of Leptospira infection was 7.6% (95% CI =4.4−12.1), with a
prevalence of 6.6% (14/210) in rodents and 1.0% (2/210) in shrews. The Leptospira
serovars circulating among rodents and shrews antibodies were Sokoine 11 (5.2%), Lora
4 (1.9%), Pomona 2 (1.0%), and Grippotyphosa 1 (0.5%). Rattus rattus were shown to
have high seroprevalence of Leptospira infection (4.2%), followed by Rattus norvegicus
(1.4%), Mus spp (1.0%) and Crocidura spp (1.0%). Furthermore, out of 402 human sera
collected from three hospitals, 31 human samples were seropositive for Leptospira
serovars, and thus, the overall seroprevalence of human leptospirosis was 7.7% (95% CI
= 5.3−10.8). Females 20 (5.0%) were shown to have high seroprevalence of disease
compared to males 11 (2.7%). The major Leptospira serovars circulating in humans were
Sokoine 44 (10.9%), Lora 25 (6.2%), Grippotyphosa 20 (5.0%), Pomona 10 (2.5%), and
Hebdomadis 9 (2.2%). The findings of this study have indicated that several Leptospira
serovars are common to rodents, shrews and humans. Likewise, market features and
practices, including a poor drainage system, the presence of stagnant water, unhygienic
conditions, and wet soil, favor rodent population and pose a risk of environmental
contamination and perpetuation rodent-environment-human infection cycle. This report
call for consideration and inclusion of this disease in the differential diagnosis of acute
febrile syndromes in humans.
Description
Dissertation
Keywords
Seroprevalence, Leptospirosis, rodents and shrews, febrile patients, Unguja Island