Bovine tuberculosis

 CAB International 2018. Bovine Tuberculosis
(eds M. Chambers, S. Gordon, F. Olea-Popelka, P. Barrow) 173

* Email: [email protected]

12.1 Introduction

Bovine tuberculosis (TB) is generally considered

a slowly progressive disease of extended dura-

tion (lasting years), and most cattle do not

exhibit readily apparent clinical signs of infec-

tion until late in the course of disease (Waters,

2015). Currently, agent-based strategies for the

detection of tuberculous cattle, such as detec-

tion of bacilli within bodily excretions, are gen-

erally unreliable for use as ante-mortem tests,

possibly due to the paucibacillary nature of the

disease resulting in a transient and low level of

bacterial shedding (Good and Duignan, 2011).

Thus, traditional clinical and microbiological

techniques are rarely used for the ante-mortem

diagnosis of bovine TB. Fortunately, Mycobacte-

rium bovis is highly immunogenic in cattle,

eliciting robust cell-mediated immune (CMI)

responses early in the course of disease, thereby

providing a useful surrogate of infection for a

disease in which ante-mortem detection of the

organism is difficult.

An immunological basis for the diagnosis

of TB was first realized shortly after Koch’s dis-

covery of tuberculin in 1890. With his studies,

Koch noted that injection of tuberculin into

Mycobacterium tuberculosis-infected humans

often resulted in systemic reactions including

hyperthermia. Using this information, veteri-

narians discovered that subcutaneous injection

of tuberculin also evoked a transient rise in body

temperature in tuberculous cattle and this reac-

tion could be of use as an immune-based diag-

nostic assay. The cumbersome subcutaneous

test was eventually replaced by a more sensitive

and practical intradermal tuberculin test. Along

with slaughter inspection followed by epidemio-

logic trace-back studies to determine herds of

origin for tuberculous carcasses, application of

the intradermal tuberculin test for removal of

test positive cattle has led to the complete eradi-

cation of bovine TB in Australia and near eradi-

cation of TB in Canada, most states within the

USA, New Zealand, and several European Union

countries (Cousins and Roberts, 2001; Good and

Duignan et al., 2011; Farnham et al., 2012;

Rivière et al., 2014; More et al., 2015). Despite

these advances, eradication and control efforts

are seriously hindered by the emergence of wild-

life reservoirs of M. bovis in multiple countries,

large-scale dairy calf and replacement heifer

rearing operations resulting in congregation

and widespread dispersal of single source-

infected animals, and increasing trade of cattle

(as a result of globalization of economies) from

regions with moderate bovine TB prevalence to

regions with very low prevalence (e.g. ~1 mil-

lion cattle shipped annually from Mexico to the

US). Thus, modern approaches requiring novel

and improved ante-mortem tests and testing

algorithms will be required to offset the emerg-

ing challenges in the control and eradication of

bovine TB.

12 Immunological Diagnosis

Ray Waters1,* and Martin Vordermeier^2

(^1) National Animal Disease Center, Agricultural Research Service, United States
Department of Agriculture, Ames, Iowa, USA;^2 Tuberculosis Research Group,
Animal and Plant Health Agency, Addlestone, UK