Bovine tuberculosis

 CAB International 2018. Bovine Tuberculosis
(eds M. Chambers, S. Gordon, F. Olea-Popelka, P. Barrow) 93

* Email: [email protected]

Although Mycobacterium bovis is classically

thought of as a cattle disease, this name belies its

diverse range of hosts. M. bovis has one of the

widest known host ranges of any zoonotic

pathogen, and has been isolated from multiple

members of a majority of mammal orders, from

rodents and insectivores, to primates and carni-

vores (O’Reilly and Daborn, 1995; Coleman and

Cooke, 2001; Delahay et al., 2002).

The presence of wildlife hosts may hinder

attempts to eradicate M. bovis in livestock. How-

ever, the isolation of M. bovis from an animal

population does not necessarily implicate that

species as important in disease outbreaks. A

host’s role in disease dynamics is dependent on a

plethora of interacting factors, including the

structure and location of lesions determining

levels and routes of excretion, host behaviour,

and likelihood of contact (direct and indirect)

between infectious and susceptible individuals.

Through understanding how these factors vary

within and between host species, their potential

role in disease maintenance and transmission

can be elucidated.

7.1 M. bovis Infection in Key

Wildlife Hosts

Given the breadth of the known host range of

M. bovis, we summarize infection in host species

thought to play a role in the epidemiology of

livestock disease. There is a vast literature on

M. bovis in these hosts and so here we focus on

the sites of infection that result in excretion,

which when combined with behaviour, provides

potential routes of intra- and inter-specific

transmission that drive infection prevalence and

persistence. The detailed pathological picture

observed in some of these species is covered in

Chapter 8.

7.1.1 Possums

Brushtail possums (Trichosurus vulpecula) are a

key wildlife maintenance host for M. bovis in

New Zealand. Although prevalence of M. bovis

in possums is generally low with an average of

5%, they are considered highly susceptible and

locally prevalence can reach 60% (Coleman

and Cooke, 2001). The average density of

brushtail possums in New Zealand is around

1 possum/ha (Nugent et al., 2015a), although

uncontrolled populations in diverse forests can

exceed 20 possums/ha (Coleman et al., 1980),

providing potential for large numbers of

infected animals. Disease progression in indi-

viduals is rapid with minimal encapsulation,

and extensive necrosis within lesions is con-

comitant with downregulation of macrophage

activity, suggesting a failure of innate

7 Role of Wildlife in the Epidemiology of

Mycobacterium bovis

Naomi J. Fox,^1 Paul A. Barrow^2 and Michael R. Hutchings1,*

(^1) SRUC, Edinburgh, UK; (^2) The University of Nottingham, Nottingham, UK