Diagnosis And Epidemiology Of Zoonotic Nontuberculous Mycobacteria Among Dromedary Camels And Household Members In Samburu County, Kenya

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 semi-structured 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