Diagnosis and Epidemiology of Zoonotic Nontuberculous Mycobacteria among Dromedary Camels and Household Members in Samburu County, Kenya
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Date
2020
Authors
Lucas, Luvai Azaale Asaava
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Zoonotic nontuberculous Mycobacteria (NTM) cross infect a wide range of
domestic animals, wildlife and man causing various diseases. Despite the public
health implications associated with mycobacterial infection and the existing close
interaction of pastoralists and camels, information on diagnosis and epidemiology of
zoonotic NTM amongst camels and closely associated community members is
scanty. The present study was a one-health approach study involving diagnosis and
epidemiology of zoonotic NTM infection among dromedary camels and associated
household members in Samburu East sub-county. The study was cross sectional
covering camels slaughtered at county abattoirs as well as household members and
camels. Abattoirs sampled included Isiolo and Athi-River camel abattoirs, where all
sampled camels were confirmed to have come from Samburu east. Household camel
sampling strategy involved stratification of the study area to Wamba and Waso
rearing areas. Sampling at abattoirs was consecutive for camels identified to have
TB-like lesions during meat inspection. People presumed to have TB from amongst
the sampled households were requested to provide a sputum sample. Screening of
lactating camels for Mycobacteria infection was done using single intradermal
comparative tuberculin test (SICTT) in a consecutive sample of 612 lactating camels
from 83 households. A consolidated milk sample from all four mammary quarters
was collected from 238 tuberculin test reactive camels. Post mortem (PM)
examination was conducted on 1600 camels originating from the study area. A semistructured questionnaire was administered to collect data on risk factors from 83
respondents. All milk, sputum and tissue samples were analysed at Kenya Medical
Research Institute (KEMRI)/Centre for Respiratory Disease Research (CRDR)
enhanced BSL2 laboratory using mycobacteriology, molecular speciation using
GenoType® Mycobacterium line probe assay (HAINLifescience), drug
susceptibility testing, 16S rDNA sequencing and phylogenetic analysis. This study
was conducted between April, 2017 and December, 2018. Results indicated that the
proportion of M. bovis and M. avium reactors was estimated at 6.05% and 39.38%
respectively. Out of 238 milk samples, 57 (23.95%) had culture positive acid fast
bacilli (AFB). Out of 132 suspected lesions on PM, 27/1600 1.69% (binomial 95%,
CI: 1.11%-2.45%) were AFB positive on culture. Of the 48 sputum samples, 7 were
AFB culture positive. The NTMs were observed to occur widely in various samples
analysed, including post mortem lesions: M. fortuitum 17/27 (62.96%), M.
scrofulaceum 3/27 (11%), M. szulgai 2/27 (7.4%); camel milk samples: M. szulgai
20/57 (35.09%), M. monacense 5/57 (8.77%), M. litorale 4/57 (7.02%), M. fortuitum
3/57 (5.26%), M. lehmannii 3/57 (5.26%), M. elephantis 3/57 (5.26%), M. duvalii
3/57 (5.26%); and in Human sputum samples: M. fortuitum 1/48 (2.08%), M. szulgai
2/48 (4.16%), and M. litorale 1/48 (2.08%) among others. These findings
demonstrate high levels of infection with NTM in both humans and camels. Camel
post mortem analyses revealed bronchial, mediastinal lymph nodes and lung lobes
were most affected tissues. Several NTMs of medical importance with varying level
of commonly used TB drugs sensitivity. The pattern of resistance to first-line TB
drugs was as follows: Isoniazid (100%), rifampicin (97.9%) and ethambutol
(65.3%). All NTM species isolated were highly resistant to first-line TB drugs.
Camel breed, age, production system, origin of new introductions, migration and
herd size were identified as risk factors for infection in camels (p<0.05).
Surveillance and notification systems for NTMs including specific immunological
test for NTMs diagnoses are needed. The public health significance of NTM in
camels and humans needs further unravelling.
Description
A Thesis Submitted in Fulfilment of the Requirements for
the Award of the Degree of Doctor of Philosophy
(Immunology) in the School of Pure and Applied Sciences
of Kenyatta University
Keywords
Zoonotic Nontuberculous Mycobacteria, Dromedary Camels, epidemiology of zoonotic NTM, Kenya