Molecular epidemiology of bovine tuberculosis in indigenous cattle and selected wild animals in livestock wildlife interface in Mikumi-selous ecosystem, Tanzania
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Date
2016
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Sokoine University of Agriculture
Abstract
Bovine tuberculosis is a chronic infectious disease that affects the health of
livestock, humans and wild animals in Tanzania and worldwide. In Tanzania, the
majority of livestock are indigenous and are kept under extensive management
system. High number of the livestock are reared in livestock-wildlife interface areas
where there is sharing of pasture and water among different animal species. Such
ecological environment can easily enhance the spread of multi-species pathogens
such as M. bovis. Spread of M. bovis depends on spatial-temporal variation of
animals within population, population dynamics and movement of pathogens within
population. The present study aimed at investigating the burden, spatial distribution,
clustering and genetic relatedness of pathogenic Mycobacteria in indigenous cattle
and wild animals in Mikumi-Selous ecosystem. The single intradermal comparative
tuberculin test (SICTT), gamma interferon (ylFN) and BovidTB Stat-Pak assays
were applied to test M. bovis infection in live animals. Tissue samples from dead
animals were cultured and isolates were identified using the Mycogenus and
Deletion methods. Genotypic relatedness was determined using Spoligotyping. A
total of 1288 live cattle, 89 slaughtered cattle, 63 African buffaloes (Syncerus
caffer) and 35 hunter-killed wild animals of 17 different species were tested. The
prevalence of M. bovis infection in cattle was 3.7% and 7.8% (n=1288) using a cut-
off for positivity of 4 mm and 2 mm, respectively. Significant large M. bovis
infection clusters was located across Msolwa, Mfilisi, Mikumi and Msongozi
villages and round Wami and Mkondoa rivers near Mikumi National Park (p=0.02)
in
Kilosa district.
Low clusters were found
in Ulanga district (p=0.03).
Mycobacterium bovis was isolated from 11.2% (n—89) of cattle samples. No
Mycobacteria isolate was found in wild animals samples. Three spoligotypes were identified, namely SB 1467, SB013.3 and SB2190. Spoligotype SB 1467 was the most
dominant and was reported for the first time in Tanzania. Spoligotype SB2190 was
novel isolate. Spoligotypes SB 1467 and SB2190 were genetically related by 96.9%
while SB2190 and SBO133 were related by 59.4%. The agreement between the tests
was established using Cohen’s kappa statistic to evaluate the agreement and form
the basis for evaluation and comparison between S1CTT, ylFN and BovidTB Stat-
Pak. Cohen’s kappa coefficient (k) agreement between ylFN and BovidTB Stat-Pak
in African buffaloes was 0.14 while the agreement between SICTT and ylFN and
between SICTT and BovidTB Stat-Pak in indigenous cattle was 0.5 and 0.21,
respectively. The agreement between the tests ranged from poor (k=O.I4) to
moderate (k=0.5). This study, for the first time established the spatial distribution of
AL bovis infection and identified AL bovis infection clusters and a novel AL bovis
spoligotype. A structured questionnaire was used to capture information from
livestock farmers on knowledge and awareness related to tuberculosis transmission
and the associated risk factors in animals and humans. About 21% (n=148) of
livestock farmers were aware of existence of AL bovis infection in livestock. There
was significant difference (p<0.001) between farmers with knowledge on M. bovis
infection transmission in animals and humans and those without the knowledge.
These findings can be applied to guide cost-effective surveillance and interventions
strategies in control of bovine tuberculosis in Tanzania.
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Thesis
Keywords
Bovine tuberculosis, Cattle, Wild animals, Mikumi, Tanzania, Ecosystem