Optimal surveillance strategies for bovine tuberculosis in a low-prevalence country

Abstract

Bovine tuberculosis (bTB) is a chronic disease of cattle that is difficult to control and eradicate in part due to the costly nature of surveillance and poor sensitivity of diagnostic tests. Like many countries, bTB prevalence in Uruguay has gradually declined to low levels due to intensive surveillance and control efforts over the past decades. In low prevalence settings, broad-based surveillance strategies based on routine testing may not be the most cost-effective way for controlling between-farm bTB transmission, while targeted surveillance aimed at high-risk farms may be more efficient for this purpose. To investigate the efficacy of targeted surveillance, we developed an integrated within- and between-farm bTB transmission model utilizing data from Uruguay’s comprehensive animal movement database. A genetic algorithm was used to fit uncertain parameter values, such as the animal-level sensitivity of skin testing and slaughter inspection, to observed bTB epidemiological data. Of ten alternative surveillance strategies evaluated, a strategy based on eliminating testing in low-risk farms resulted in a 40% reduction in sampling effort without increasing bTB incidence. These results can inform the design of more cost-effective surveillance programs to detect and control bTB in Uruguay and other countries with low bTB prevalence.

Role of animal movement and indirect contact among farms in transmission of porcine epidemic diarrhea virus

“…Mathematical and computational modeling of infectious diseases is a common approach to simulating the spread of disease in a population, exploring key epidemiological parameters that drive transmission, and evaluating alternative control strategies (Brooks-Pollock et al, 2015;Craft, 2015;VanderWaal et al, 2017). In livestock populations, network-based models based on data on animal movements between farms have been a key area of research (Bajardi et al, 2012;Craft, 2015;Green et al, 2006;Kao, 2002;Kao et al, 2007;Rossi et al, 2015).…”

Identifying outbreaks of Porcine Epidemic Diarrhea virus through animal movements and spatial neighborhoods

“…A farm's risk of infection may thus be impacted not just by its own animal movements, but also by movements made by neighbors. These local spatial dynamics are rarely accounted for in network-based assessments of risks associated with livestock movement, although such dynamics are an emergent property of epidemiological models simulating disease spread in spatial networks 11,12 .Much of our understanding of between-farm pathogen transmission in the United States swine industry is based on outbreak investigations, case-control studies, cohorts and case reports involving a relatively small number of farms [13][14][15] . Large-scale datasets in which to investigate the interacting roles of animal movements versus local transmission in between-farm spread are largely lacking.…”

“…A farm's risk of infection may thus be impacted not just by its own animal movements, but also by movements made by neighbors. These local spatial dynamics are rarely accounted for in network-based assessments of risks associated with livestock movement, although such dynamics are an emergent property of epidemiological models simulating disease spread in spatial networks 11,12 .…”

An experts’ opinion-based comparison and benefit cost analysis of post-mortem versus tuberculin skin test surveillance systems, Mpumalanga, South Africa

“…This low prevalence in cattle may justify the use of point-of-slaughter postmortem evaluation in communal areas for diagnosis and surveillance. VanderWaal et al [11] studied different surveillance strategies such as PMS and targeted testing as alternatives to routine skin testing in low TB prevalence settings. They found that targeted surveillance was more cost effective and reduced sampling effort by 40% without increasing the incidence of bTB.…”