Tuberculosis spread from animals to humans may be greater than
previously thought

Date:
June 15, 2020
Source:
Penn State
Summary:
The number of human tuberculosis (TB) cases that are due
to transmission from animals, as opposed to human-to-human
transmission, may be much higher than previously estimated,
according to an international team of researchers. The results
could have implications for epidemiological studies and public
health interventions.



FULL STORY ==========================================================================
The number of human tuberculosis (TB) cases that are due to transmission
from animals, as opposed to human-to-human transmission, may be much
higher than previously estimated, according to an international team
of researchers. The results could have implications for epidemiological
studies and public health interventions.


========================================================================== "Tuberculosis kills 1.4 million people every year, making it the most
deadly disease arising from a single infectious agent," said Vivek Kapur, professor of microbiology and infectious diseases and Huck Distinguished
Chair in Global Health, Penn State. "India has the largest burden of
human tuberculosis globally, with more than 2.6 million cases and 400,000 deaths reported in 2019.

Additionally, the cattle population in India exceeds 300 million, and
nearly 22 million of these were estimated to be infected with TB in 2017.

Kapur noted that the World Health Organization, World Organisation
for Animal Health and Food and Agriculture Organization of the United
Nations define zoonotic TB as human infection with Mycobacterium bovis,
a member of the Mycobacterium tuberculosis complex (MTBC).

To evaluate the use of M. bovis as a proxy for zoonotic tuberculosis
and to investigate the potential role of other MTBC subspecies, Kapur
and his colleagues analyzed 940 bacterial samples -- both pulmonary
(from lung fluid or tissue) and extrapulmonary (from tissues other
than the lungs) -- collected from patients who were visiting a large
reference hospital for TB in southern India. The researchers used PCR
to speciate M. tuberculosis complex organisms and then sequenced all
the non-M. tuberculosis samples. Next, they compared the sequences to
715 sequences from cattle and humans that had previously been collected
in south Asia and submitted to public databases.

"Surprisingly, we did not find any evidence for the presence of M. bovis
in any of the samples," said Sreenidhi Srinivasan, postdoctoral scholar
in the Huck Institutes of the Life Sciences. "Instead, we found that
seven of the patient samples contained M. orygis. Six of these came from patients with extrapulmonary TB." They describe their findings in a
paper published June 1 in The Lancet Microbe.

As expected, most of the remainder of the sequences from the patients
belonged to M. tuberculosis -- the TB bacterium that is generally thought
to be transmitted only among humans.

"Our findings suggest that M. bovis might be uncommon in India, and that
its detection may not be an adequate proxy for zoonotic TB infection
in humans," said Srinivasan. "These data indicate that members of the
TB complex other than M. bovis might be more prevalent in livestock
in India." Kapur added that the operational definition of zoonotic TB
should be broadened to include other MTBC subspecies capable of causing
human disease.

"By 2035, the World Health Organization is aiming to reduce the incidence
of tuberculosis by 90% as a part of its End TB Strategy," he said. "The increasing evidence supporting M. orygis endemicity in south Asia and the identification of M. tuberculosis in cattle highlight the importance of
using a One Health approach, involving multisectoral collaboration across
the veterinary and clinical sectors, to meet the WHO's goal in India."

========================================================================== Story Source: Materials provided by Penn_State. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Shannon C Duffy, Sreenidhi Srinivasan, Megan A Schilling,
Tod Stuber,
Sarah N Danchuk, Joy S Michael, Manigandan Venkatesan, Nitish
Bansal, Sushila Maan, Naresh Jindal, Deepika Chaudhary, Premanshu
Dandapat, Robab Katani, Shubhada Chothe, Maroudam Veerasami,
Suelee Robbe-Austerman, Nicholas Juleff, Vivek Kapur, Marcel A
Behr. Reconsidering Mycobacterium bovis as a proxy for zoonotic
tuberculosis: a molecular epidemiological surveillance study. The
Lancet Microbe, 2020; 1 (2): e66 DOI: 10.1016/ S2666-5247(20)30038-0 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200615115814.htm

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